CHAPTER XII_Lead poisoning and lead absorption

PREVENTIVE MEASURES AGAINST LEAD POISONING

=Amount of Lead Fume and Dust in the Atmosphere Breathed.=--Lead fuses

at 325° C. and boils at between 1450° and 1,600° C. It is volatile when

heated to a cherry-red colour--about 550° C.

Experiments[A] carried out in the laboratory of a lead smelting works

in London to determine the temperature at which leady fumes rise

from the surface of open baths of molten lead, showed that unless

pure lead is heated to about 500° C., and at the same time stirred,

no appreciable fume comes off, and that from lead, at the same

temperature, under ordinary working conditions, little or no lead

in the form of oxide passes into the air. From lead that has been

unrefined or which contains zinc--that is, lead in the earlier stages

of its manufacture (in the reverberatory furnace)--leady fume was not

given off at temperatures less than 760° C. even when stirred, because

at a temperature of 600° C. the surface of the molten metal became

covered with fluid slag, which will not allow any oxide to be given

off. Impurities such as tin or antimony prevent the oxidation of molten

lead at lower temperatures, and give it a bright, shiny colour. When

heated to about 600° C., these impurities form a slag on the surface

of the lead containing antimoniates and stannates of lead, which do

not evolve lead fumes unless heated to temperatures never likely to be

reached in open lead pots. The reason why molten refined lead can give

off lead fume more readily than those named is because the oxide formed

on the surface is a dry powder and not in the form of slag. Hence, when

the bath is stirred, some of the dry oxide is broken up and may rise

into the air. When a bath of molten lead is not stirred at all, it can

be heated to over 740° C. without finding oxide in the air aspirated--a

temperature not obtained under ordinary working conditions.

[A] In these experiments air was aspirated through an iron funnel

having an area of 113 square inches (12 inches diameter), placed at

a height of 1¹⁄₂ inches above the molten metal, and connected to an

iron tube 3 feet in length and ¹⁄₂ inch in diameter. Inside the iron

tube was a glass tube, one end reaching own to the top of the funnel

and the other connected with a tube containing pure loose asbestos

wool, and continued down to a tightly stoppered bottle holding

dilute sulphuric acid. Another glass tube connected this bottle with

an aspirator. The asbestos tube was weighed before and after each

test, and the asbestos then treated with nitric acid, and the lead

determined volumetrically. In none of the tests made was lead found

in the bottle containing sulphuric acid.

Were there nothing else to consider but escape of lead fume from a pot

or bath of molten metal, obviously hooding over of the bath and removal

of the fume from the atmosphere of the workroom would be unnecessary

until this temperature was reached. Usually, however, the bath is kept

standing exposed to the air, and the oxide which forms on the surface

has to be skimmed off periodically, and whenever the ladle is emptied

a small cloud of dust arises. Or at times, in certain processes,

chemical interaction takes place in the bath, as in the dipping of

hollow-ware articles previously cleaned in hydrochloric acid, with

evolution of fume of volatile chloride of lead. Any vessel, therefore,

of molten metallic lead in which skimming is necessary, or in which

chemical action gives rise to fume, requires a hood and exhaust

shaft, even although the temperature is little, if at all, above the

melting-point--unless, indeed, a separate exhaust can be arranged for

the removal of the dust immediately above the point where the skimmings

are deposited.

Of many samples of dust collected in workrooms where there are baths

of molten lead, it is impossible to say definitely how much of the

lead present is due to fume, and how much to dust. Thus, a person

tempering the tangs of files was attacked by plumbism, and a sample of

dust collected from an electric pendent directly over the pot, at a

height of 4 feet from the ground, was found to contain 15·6 per cent.

of metallic lead. Similarly, a sample taken above a bath for tempering

railway springs contained 48·1 per cent. metallic lead[1]. And,

again, a sample collected from the top of the magazine of a linotype

machine contained 8·18 per cent. Such analyses point to the necessity

of enclosing, as far as possible, the sources of danger--either the

fume or the dust, or both. Determination of the melting-point of the

molten mass will often help in deciding whether there is risk of fume

from the pot, and, if there is not (as in the sample of dust from the

linotype machine referred to), will direct attention to the sources of

dust in the room. Proceeding on these lines, S. R. Bennett[2], using

a thermo-electric pyrometer which had been previously standardized and

its rate of error ascertained, and checking the results in some cases

by a mercury-in-glass thermometer (the bulb of which was protected by

metal tubing), determined the temperature of the various pots and baths

of molten lead used in the Sheffield district. As was anticipated,

temporary cessation of work, stirring up of metal, recoking of

furnaces, and other causes, produced fluctuations of temperatures from

minute to minute in the same pot, and in its different parts. The

compensated pyrometer used gave for file-hardening pots a maximum of

850° C., and a minimum of 760° C., the average mean working temperature

being about 800° C. The variations of temperature of lead used for

tempering tangs of files and rasps was found to be high, and largely

unrestricted from a practical standpoint. The maximum was 735° C.,

and the minimum 520° C., the average mean working temperature being

650° to 700° C., varying more than this within a few hours in the same

pot. Spring tempering is carried out at some comparatively constant

temperature between a maximum of nearly 600° C. and a minimum of 410°

C., depending on the kind of steel and the purpose for which the steel

is to be employed. Generally, the temperature required rises as the

percentage of carbon in the steel is diminished. As these baths are

larger than file-hardening pots, the temperature range is higher at

the bottom than at the top unless well stirred up. Some lead pots are

set in one side of a flue, and the temperature in the mass is then

greater on the furnace side. From further observation of these pots

during experiments, he was inclined to believe that the lead did not

volatilize directly into the atmosphere, as heated water does, but that

the particles of coke, fused oil, etc., which rise from the surface,

act as carriers of the rapidly oxidized lead particles which cling to

them.

Similar experiments were carried out in letterpress printing works. The

average temperature was 370° C. in the stereo pots, and in the linotype

pots at work 303° C. Scrap lead melting-pots when hottest registered

424° C., but registered as low as 310° C., according to the amount of

scrap added, the state of the fire underneath, etc. The best practical

working temperature depends largely on the composition of the metal

used. That at some factories is the same for stereo drums as for lino

pots--viz., 81·6 per cent. lead, 16·3 per cent. antimony, and 2·0 per

cent. tin, added to harden the lead. On the other hand, some printers

use a higher percentage of antimony in the lino than in the stereo

metal. Lead melts at 325° C., and antimony at 630° C., but by adding

antimony to lead up to 14 per cent. the melting-point is reduced at

an almost uniform rate to 247° C., after which further addition of

antimony raises the melting-point. This explains why temperatures as

low as 290° C. are practicable for linotype pots. The molten eutectic

has a specific gravity of about 10·5, whereas the cubic crystals

average 6·5 only; therefore in these pots the latter float on the top,

and excess of antimony is to be expected in the skimmings or on the

surface.

Administration of certain sections of the Factory and Workshop Act,

1901, would be simplified were there a ready means available for

determining the extent of contamination of the air--especially of

Section 1, requiring the factory to be ventilated so as to render

harmless, as far as practicable, all gases, vapours, dust, or other

impurities, generated in the course of the manufacturing process, that

may be injurious to health; of Section 74, empowering an inspector

to require a fan or other means if this will minimize inhalation of

injurious fumes or dust; of many regulations having as their principal

object removal of dust and fumes; and of Section 75, prohibiting meals

in rooms where lead or other poisonous substance is used, so as to give

rise to dust or fumes. Unfortunately, owing to the difficulty hitherto

of accurate collection, only a very few determinations of the actual

amount of lead dust and fume present in the atmosphere breathed have

been made. This lends peculiar value to a series of investigations by

G. Elmhirst Duckering, which have thrown much light on the amount of

lead fume present in the air of a tinning workshop, and the amount of

lead dust in the air during certain pottery processes, and the process

of sand-papering after painting. Incidentally, also, they help to

determine the minimal daily dose of lead which will set up chronic lead

poisoning[3]. Aspirating the air at about the level of the worker’s

mouth for varying periods of time, he determined the amount of lead

in the fume, or in the dust, per 10 cubic metres of air, and from

knowledge of the time during which inhalation took place he calculated

the approximate quantity inhaled per worker daily. We have summarized

some of his conclusions in the table on pp. 204, 205:

Duckering’s experiments as to the presence of fumes containing

compounds of lead in the atmosphere breathed were carried out in a

workshop for the tinning of iron hollow-ware with a mixture consisting

of half lead and half tin. The process of manufacture and the main

sources of lead contamination in the air (knowledge arrived at from

these experiments) are explained on p. 59. As the result of laboratory

experiments designed to show the effect of the violent escape of vapour

produced below the surface of molten metal in causing contamination of

the air, and the nature of the contaminating substances, he was able

to conclude that the chemical action of the materials (acid and flux)

used, and subsequent vaporization of the products of this action, was

a much more important factor than the mechanical action of escaping

vapour. Subsequently, experiments carried out on factory premises gave

the results which are expressed in the table as to the relative danger,

from lead, to (_a_) a tinner using an open bath; (_b_) a tinner working

at a bath provided with a hood and exhaust by means of a furnace flue;

and (_c_) the nature and extent of air contamination caused by the

operation of wiping excess of metal (while still in a molten state)

from the tinned article. In all three experiments aspiration of air

was made slowly: it was maintained at the rate of 3 to 4 cubic feet

an hour in the first experiment for between seven and eight hours; in

the second for twenty-eight to twenty-nine hours; and in the third for

twenty-four to twenty-five hours. The person engaged in tinning at the

open bath was shown to be exposed to much more danger than one working

at a hooded bath, while the wiper was exposed to even more danger than

the tinner using an open bath, since not only was he inhaling fume from

the hot article, but also fibre to which considerable quantities of

metallic lead and tin adhered.

Analysis of samples of dust collected in different parts of the

workroom bore out the conclusions derived from analysis of the

fumes. Thus, samples collected from ledges at varying heights above

the tinning bath containing the mixture of tin and lead contained

percentages of soluble lead (lead chloride) in striking amount as

compared with samples collected at points in the same room remote from

any source of lead fume, while the insoluble lead present, as was to be

expected from the fact that it consisted of lead attached to particles

of tow floating in the air, was less variable.

TABLE XII., SHOWING QUANTITIES OF LEAD (PB) IN THE ATMOSPHERE AT

BREATHING LEVEL.

(G. E. DUCKERING’S EXPERIMENTS.)

+------------------------------+-------------+--------+--------------+

| +-----+-------+halation| inhaled |

+------------------------------+-------------+--------+--------------+

| (1) | (2) | (3) | (4) | (5) |

|Tinner using open bath | -- | 37·79| 5¹⁄₂ | 10·70 |

| | | | | |

|Tinner using bath covered by | -- | 6·36| 5¹⁄₂ | 1·80 |

|Wiping off (tinning) | -- | 124·31| 5¹⁄₂ | 35·20 |

|Earthenware dipping (pottery) | 38 | 1·80| 7¹⁄₂ | 0·69 (average|

|Earthenware dipping (pottery) | 84 | 6·27| 7¹⁄₂ | 2·40 (single |

|China dipping (pottery) | 36 | 2·12| 7³⁄₄ | 0·83 (average|

| | | | | |

|Rockingham ware dipping | 44 | 2·26| 7¹⁄₂ | 0·86 (single |

| | | | | |

|Earthenware cleaning (pottery)| 47 | 2·29| 7¹⁄₂ | 0·88 (average|

|China ware cleaning (pottery) | 123 | 13·34| 6 | 4·08 (single |

| | | | | |

|Earthenware drying (pottery) | 25 | 2·19| 8 | 0·92 (average|

|Earthenware glost placing | 34 | 2·08| 8³⁄₄ | 0·93 (average|

|China glost placing (pottery) | 30 | 1·08| 9 | 0·50 (single |

|China glost placing (pottery) | 21 | 0·32| 9¹⁄₂ | 0·16 (single |

|Majolica-painting of tiles | 61 | 9·11| 7¹⁄₂ | 3·48 (single |

| | | | | |

| |{206 | 53·70| -- | -- |

|Sand-papering and dusting |{ | | | |

|railway coaches |{241 | 116·10| -- | -- |

| |{ | | | |

| {| 453 | 83·10| -- | -- |

|Sand-papering {| | | | |

|coach wheels {|1343 |1025·60| -- | -- |

| {| | | | |

|Sand-papering motor-car body | 600 | 278·30| -- | -- |

| | | | | |

| |{ 88 | 38·70| -- | -- |

| |{ | | | |

|Sand-papering |{ | | | |

|motor-car wheels |{ | | | |

| |{ 35 | 4·70| -- | -- |

| |{ | | | |

|Sand-papering van wheel | 494 | 143·80| -- | -- |

| | | | | |

|Burning off old paint | 52 | 3·40| -- | -- |

| | | | | |

+------------------------------+-------------+--------+--------------+

+-----------------------------+-----+--------------------------------+

| | | |

| | Per-| |

| |cent-| |

| | age | |

| | of | |

| | Lead| |

| | in | |

| Occupation. |Dust.| Remarks. |

+-----------------------------+-----+--------------------------------+

| (1) | (6) | (7) |

|Tinner using open bath | -- |The whole inhaled in the form of|

| | |vapour of lead or similar |

| | |compound. |

|Tinner using bath covered by | -- |The whole inhaled in the form of|

|hood, and having fumes | |vapour of lead or similar |

|exhausted by draught of | |compound. |

|furnace | | |

|Wiping off (tinning) | -- |14·1 milligrammes of metallic |

|furnace | |lead inhaled as lead chloride, |

|furnace | |and 21·1 milligrammes as |

|furnace | |metallic lead adhering to |

|furnace | |floating fibres of tow. |

|Earthenware dipping (pottery)| 8·30|Dipping boards not used. |

| | | |

|Earthenware dipping (pottery)| 7·42|Very dirty dipping boards used. |

|furnace | |Work very rapid, and much |

|furnace | |shaking of ware after dipping. |

|China dipping (pottery) | 5·43|China glaze usually contains |

| | |about two-thirds as much lead as|

| | |that of earthenware. |

|Rockingham ware dipping | 4·37|Dirty dipping boards in use. |

|(pottery) | |Glaze contains three times as |

| | |much lead as ordinary earthen- |

| | |ware glaze, but the ware is not |

| | |shaken after dipping. |

|Earthenware cleaning | 5·90|Cleaning done in or at front of |

|(pottery) | |exhaust hood. |

|China ware cleaning (pottery)|10·85|Very defective exhaust; hood so |

| | |arranged that cleaning had to be|

| | |done outside. Glaze contains |

| | |about two-thirds as much lead as|

| | |that for earthenware. |

|Earthenware drying (pottery) | 8·58|Filter placed at breathing level|

| | |in centre of drying stillage. |

|Earthenware glost placing | 6·58| |

|(pottery) | | |

|China glost placing (pottery)| 3·64|Boards used were fairly dirty. |

| | | |

|China glost placing (pottery)| 1·50|One man only working. |

| | | |

|Majolica-painting of tiles |15·00|Tiles cleaned, while still damp,|

|(pottery) | |with knife. Much dry waste glaze|

| | |on wooden floor, and much |

| | |traffic. Several cases of lead |

| | |poisoning in this room. |

| |26·10|Passenger fish truck after one |

|Sand-papering and dusting | |coat of lead colour. |

|railway coaches |48·10|Railway coach after one coat of |

| | |lead colour on filled and faced |

| | |surface. |

| {|18·30|After two coats of quick-drying |

|Sand-papering {| |white lead paint. |

|coach wheels {|76·40|Old cream-painted wheel before |

| {| |repainting. |

|Sand-papering motor-car body |46·40|Door of motor body after one |

| | |coat of lead colour and quick- |

| | |drying sand-paper stopping. |

| | |Urgent work. |

| |44·00|Wooden motor wheels after two |

| | |coats of lead colour and sand- |

|Sand-papering | |papering between. Exhaust not |

|motor-car wheels | |running. |

| |13·30|Same point, but with exhaust |

| | |running. |

|Sand-papering van wheel |29·10|After one coat of quick-drying |

| | |permanent red on two coats of |

| | |flesh colour (sand-papering |

| | |after each coat). |

|Burning off old paint | 6·50|White paint of London and North-|

| | |Western coach. Gas-burner used. |

+-----------------------------+-----+--------------------------------+

=Dust.=--Reference to the table shows that the conditions in the

pottery workrooms, as stated in Column 7, are reflected in Columns 3

and 5. Further details from his experiments may be useful. Thus, in a

dipping room where low-solubility glaze was in use, the amount of lead

in the dust collected per 10 cubic metres of air was 0·70 milligramme.

The average of four experiments where there were no dipping boards

was 1·80 milligrammes, and where dipping boards were used, 3·75;

_i.e._, 1·95 milligrammes of lead in the dust per 10 cubic metres of

air is added by the use of dirty dipping boards. As the result of his

experiments, Duckering believes that approximately 1·95 milligrammes of

lead per 10 cubic metres of air was due to the fine spray given off in

the shaking of the ware. In bright sunlight, he says, the spray can be

seen dancing high above the dipping tub. In a dipping house where work

was done slowly by two occupants only, the proportion of lead in the

measured quantity of air was also low--0·58 milligramme per 10 cubic

metres. Where, in the absence of special provision made for admission

of fresh air to a fan, the air was drawn from a neighbouring room in

which lead processes were carried on, the amount of lead rose to 5·76

milligrammes at the level breathed by the gatherer at a mangle. In

ware-cleaning the average of all his observations where lead was used

(eleven) was 3·44 milligrammes; and he concluded that “wet cleaning of

ware causes less direct contamination of the atmosphere, even where

no local exhaust is applied. A still more important result of wet

cleaning, however, is that the overalls keep much freer of dust.” The

highest results were obtained when the process of ware-cleaning was

done outside the influence of the exhaust draught. In one instance,

where the ware was cleaned at a distance of 6 feet from the exhaust

opening, 13·34 milligrammes per 10 cubic metres of air were found.

Subsequently at the same point, after the exhaust system of ventilation

had been remodelled, 0·95 milligramme only was present. Even in a

stillage room in which no work was done other than the placing on and

removal of the boards from the racks, the lead content per 10 cubic

metres of the air was 1·08 milligrammes. In glost-placing, the average

of four experiments was 1·83 milligrammes--no doubt the result of glaze

on the boards. As much as 9·11 milligrammes of lead was found per 10

cubic metres of air in the centre of a large majolica-painting room,

with wooden floors and much traffic in it. Wooden floors generally

appeared to influence the results, as determinations of the lead

present were higher in rooms with them than with tiled floors.

In coach-painting the proportion of lead found by Duckering in the air

breathed during the actual time of sand-papering explains the severe

incidence of poisoning in this class of work. The table shows the

amount of lead in the air to be enormous, and in many cases much in

excess of the amount found in the air when wiping off in the tinning

of hollow-ware. The work of sand-papering is, however, very rarely

continuous, the time occupied in it being, for the painter, about one

to two hours daily; for the brush hand, two to three and a half hours;

and for the painter’s labourer, four to five hours.

Knowing intimately the processes at which the estimations recorded

in the table were made, the relative frequency of cases of plumbism

reported among those employed at them, and the duration of employment

prior to attack, we believe that, if the amount of lead present in the

air breathed contains less than 5 milligrammes per 10 cubic metres of

air, cases of encephalopathy and paralysis would never, and cases of

colic very rarely, occur. And this figure is a quite practical one in

any process amenable to locally-applied exhaust ventilation. Somewhere

about 2 milligrammes, or 0·002 gramme, of lead we regard as the lowest

daily dose which, inhaled as fume or dust in the air, may, in the

course of years, set up chronic plumbism.

=Local Exhaust Ventilation.=--In considering preventive measures

against lead poisoning, precedence must be given to removal of fumes

and dust by locally-applied exhaust ventilation, as, unfortunately, the

wearing of a respirator is neither in itself a sufficient protection,

nor, if it were, could the constant wearing of one be enforced. A

respirator is of no use against lead fume. In the case of dust, the

conditions which it must fulfil to be effective are, first, that the

air breathed is freed from dust, and, secondly, that it should not

incommode the wearer. Further, it should be simple in construction,

easily applied, and allow of frequent renewal of the filtering medium.

No existing respirator of moderate price conforms quite satisfactorily

with these requirements. The more closely to the face it is made to

fit, and the more effectually the air is filtered, the greater is the

inconvenience experienced when it is worn. This inconvenience is due to

the exertion (showing itself in increase of the respiratory movements

and pulse-rate) caused in aspirating the air through the filtering

medium, and rebreathing some portion of the expired breath, containing

a much greater proportion of carbonic acid gas and of moisture at

a higher temperature than are present in fresh air. Respirators,

therefore, except for work lasting a short time--half an hour to

an hour--cannot be considered an effective or sufficient means of

protecting the worker against dust. If a respirator must be worn, the

simplest form is a pad of ordinary non-absorbent cotton-wool (absorbent

wool quickly becomes sodden and impervious), about 3 inches by 4

inches, placed over the mouth and nostrils, and kept in position by

elastic bands passed round the ears. The pad should be burnt after use.

With a smooth, impervious floor, however, and ventilation designed to

remove the fumes and dust at, or as near as possible to, the point of

origin, lead poisoning would become very rare in most of the industries

to be described. The essential points of such a system are--(1) The

draught or current of air set in motion either by heat or by a fan; (2)

the ducts along which the current travels; (3) the hoods or air-guides

designed to intercept and catch the fumes and dust at the point of

generation; (4) inlets from the outside air into the room to replace

continuously the air extracted, and, in many cases, (5) a suitable dust

filter or collector.

_Exhaust by Heat._--Processes giving rise to fumes or to dust liberated

on stirring or skimming, which can be dealt with by the draught created

in the furnace flue or over a bath of molten metal provided with

adequate hood and duct up which the heated air travels, are--Smelting,

refining, spelter manufacture, and the numerous operations

necessitating the melting of lead, such as tinning with a mixture of

tin and lead, sheet lead and lead piping, stereo pots in letterpress

printing, pattern-making, tempering springs, file-hardening, etc. The

dusting of red-hot metallic surfaces, as in vitreous enamelling, might

possibly also be dealt with in the same way. The disadvantage of the

exhaust by heat is the uncertainty and inequality of the draught, and

the size of the duct necessary to cope with the volume of rarefied air

from above the molten vessel.

The closer the hood is brought down over the point where the fumes

escape, the less risk is there of cross-currents deflecting them into

the workroom. Hence all baths of molten metal should have the sides

and back closed in, leaving as small a space open in front as is

practicable in view of necessary skimming or other operations.

In the case of tinning baths, Duckering[4] describes completely

successful results when from the top of the hood a shaft at least 24

inches in diameter was carried vertically upwards into the open air to

a height of 18 feet, and the top of the shaft fitted with a wind screen

in the form of a very large cone, having its lower edge below the upper

edge of the shaft, and its nearest point at least 8 inches from the top

of the shaft. Smoke produced in large quantity at any point 6 inches

outside the front of the hood was entirely drawn into it. As, however,

the inrush of air caused an eddy of the fumes at the upper edge of

the opening, the edges of the hood were turned inwards, so that the

operation of wiping was done in a sort of short tunnel. In general, it

may be said that the diameter of pipes leading from hoods to the outer

air (on the efficacy of the draught in which success depends) is much

too small. Frequently mere increase in size will convert an indifferent

draught into a good one. The height of the hood also--_i.e._, the

distance between its lower border and the point where it joints

the duct--is of importance. The shorter this distance is, the less

serviceable does it become for the removal of fume. Indeed, it may even

retain the fume which, were the hood not present, would rise to the

roof. Sometimes safety is increased by making the hood double, leaving

a space between the two sheets, and so concentrating the draught at

the centre and at the margin. With a fan, ducts of less diameter can

be used than when dependence is placed on heat alone. A duct carried

into a chimney-stack has the advantage of dispersing the fume at a safe

distance from the workroom.

The variableness of the draught produced by heat makes it unsuitable

for removal of dust, except such as arises from skimming. The

receptacle for the skimmings should always be kept inside the canopy of

the hood. We have, however, seen the dust given off in the heading of

yarn dyed with chromate of lead successfully carried away under hoods

connected up by branch ducts with the main chimney-stack.

[Illustration: FIG. 1.--DAVIDSON’S SIROCCO PROPELLER FAN.]

_Exhaust by Fans._--The draught for removal of dust, and frequently

also of fumes, is produced by a fan, of which there are two types:

(1) low-pressure volume fans and (2) high-pressure centrifugal fans.

In the first the draught is created by the rotation of a wheel with

inclined vanes, causing the air to be driven transversely through the

wheel parallel to the axis of rotation (Fig. 1). During a revolution

a portion of the air is cut off from one side of the wheel, and

transferred through the wheel to the other. Such fans are light, run

easily, and are cheap. They are of many forms, both with regard to the

number of blades--from two to eight--and general manner in which they

are arranged. Some closely resemble the screw-propeller of a ship,

while others have blades turned over and fastened on an outer rim.

Their main defect is inability to overcome any but slight resistance

in the course of suction behind, as from constriction in, or friction

along the sides of, the ducts and right-angled bends, or of outflow in

front, as from wind-pressure. Under favourable conditions, however, and

when carefully fitted, a volume fan will exhaust dust and fumes through

a system of ducts several feet in length, as, for example, from mono

and linotype machines and electro melting-pots in letterpress printing

works. But, in order to avoid resistance from friction, the ducts have

to be somewhat larger in diameter than when a centrifugal fan is used.

With nine[A] linotype machines connected up to a 14-inch propeller

fan, the branch ducts should be about 4 inches in diameter, and the

main duct 12 inches, increasing from 12 to 15 inches within 2 feet of

the fan-box. The shorter and straighter the course of the duct to the

propeller fan, the more efficiently it works. Wind-guards are necessary

to overcome resistance from this source in front, but their position

requires to be carefully considered, so as to prevent the screen itself

crippling the outflow.

[A] If gratings are also inserted in the same duct for general

ventilation the number of machines must be decreased _pro ratâ_.

All fans require frequent cleaning, and in this respect propeller fans

have the advantage over centrifugal, in that they are usually more

accessible.

[Illustration: FIG. 2.--DAVIDSON’S DUST CENTRIFUGAL FAN.]

_Centrifugal Fans._--Generally, in the removal of dust, a strong

suction has to be set up in a system of narrow ducts by means of a

centrifugal fan--_i.e._, a fan-wheel formed by a number of vanes

attached to an axle mounted in a spiral-shaped casing--so that when

the wheel rotates air is carried along by the vanes, and flies off

tangentially into the space between the blades and the casing, and

thence to the outlet (Fig. 2). The air inlet or junction of the fan

with the exhaust duct is at the centre of the fan, an arrangement by

which the kinetic energy created by the rapid motion of the air leads

to increase of draught instead of being wasted in production of eddies

in the surrounding spaces. They are made in many different patterns,

according to the nature of the work to be done. Their advantage over

the propeller type in the removal of dust lies in the fact that they

overcome greater internal resistance, and a uniform high velocity in a

complicated system of pipes can thus more easily be maintained.

[Illustration: FIG. 3 shows adjustable hoods and ducts fitting closely

over rollers for mixing coloured inks, and serving not only to prevent

inhalation of lead dust by the workers, but also the colour from one

machine affecting that on another. In the particular room where the

installation is fitted there are thirteen separate sets of rollers; the

diameter of the branch duct of each machine is about 5 inches, and that

of the main duct close to the fan about 20 inches. The special points

we have considered as to entrance of all branch ducts into the main

duct tangentially, gradual tapering of the main trunk, and collection

of the dust in filter-bags, are noticeable. Further, when one set of

rollers is not in use the raising of the hood automatically cuts off

the draught through it. (Drawing supplied by the Sturtevant Engineering

Company, Limited, London.)]

_Ducts._--The main duct should be of metal (steel, sheet-iron, or

zinc); it should be circular in shape, have as straight and short a

course as possible, and be tapered in such manner that the area of

cross-section at any point shall equal the combined areas of all the

branch pipes which have entered it at that point (Fig. 3). Proper

dimensions must be studied in relation to the size of the fan and the

work to be done. Wooden ducts, unless chosen for specific reasons,

such as the presence of acid in the fumes to be removed, are very

unsatisfactory, as it is difficult to maintain them in an air-tight

condition or to make branch pipes enter with rounded junctions. Where

several branch ducts enter a main duct, situation of the fan midway

between them has advantage, not only in saving metal in piping, but

also in causing the distance of the fan from the farthest branch

duct to be only half what it would be were the fan placed at the end

of the system (see Fig. 7, p. 217). Further, the sectional area of

the two collecting ducts will be less than that of one main duct, and

greater uniformity of flow thereby secured. Where the two ducts join

up into the single duct of the fan, the bends must be easy; otherwise

the draughts would collide and neutralize one another. Branch ducts,

if they cannot be made tangential to a rounded curve, should enter

the main duct at an angle of 30 degrees, as by so doing equalization

of the draught at different openings is made fairly uniform. The very

common defect of a right-angle joint diminishes the draught by nearly

one-half. Branch ducts should never be made to enter a main duct on the

outer side of a bend, because at this point the pressure of the current

of air inside the duct is increased. They should join up on the inside

of a bend, where the pressure is reduced.

_Hoods and Air-Guides._--As the object of hoods is to concentrate the

draught on the fumes or dust to be removed from the worker, position

in regard to origin of the fumes or dust requires first consideration.

The more restricted the opening consistent with unimpeded work, the

more effective is the draught, and the less disturbed will it be by

cross-currents in the workroom. Pendock lays it down as a useful

principle that the area of the front opening into the hood should not

be more than four times that of the exhaust throat--_i.e._, the point

of junction of the hood and duct (Fig. 4). Not less important is it

that the draught should operate below the breathing level. Preference

as to the direction to be given to the exhaust current should be in the

order named: (1) Downwards; (2) downwards and backwards combined; (3)

backwards and upwards combined; and (4) upwards only. Use should be

made, for the removal of the fumes or dust, of any initial current of

hot air set up from a bath of molten metal or from a heated metallic

surface, as in vitreous enamelling. Hence under such circumstances only

(3) and (4) need be considered. Generally hoods applied err in having

too wide an opening, or they are placed too far away from the source of

danger. They require sometimes to be adjustable to suit different-sized

articles. Care is necessary to see that, when a hood has been adjusted

for large articles, it is readjusted for smaller-sized articles. The

principle of ventilation downwards and backwards is recognized as right

for grinding and polishing on a wheel, since the tangential current set

up by the wheel in its rotation is utilized. Pug-mills in paint-works

are perhaps best ventilated by applying the exhaust to a dome-shaped

hood covering the posterior half of the mill. Edge-runners must be

encased, with an exhaust pipe attached to the casing and sliding

doors or shutters for introduction or removal of material (Fig. 5). A

small negative pressure inside the casing is all that is necessary,

so as to insure passage of air inwards and not outwards. Branch ducts

must protect the casks out of which material is scooped, and the

receptacle into which it is discharged. In scooping out dry colour

from a barrel, it is unwise to attempt to remove the dust created at

every displacement of air on removal of a scoopful by means of a hood

suspended over the barrel. Instead, the last joint of the duct should

be a telescopic one, so that it can be lowered into the barrel, and be

kept at a distance of about 6 inches above the material. The air is

thus drawn downwards into the barrel (Fig. 6).

[Illustration: FIG. 4 shows a well-designed arrangement of hoods,

duct, and fan, in the packing of white lead, and the filter-bags for

collecting the dust so removed. An additional safeguard is introduced,

as the casks stand upon grids through which a down-draught is

maintained by connecting the space underneath with the exhaust system.

(Drawing supplied by the Sturtevant Engineering Company, Limited,

London.)]

Processes such as colour-dusting, aerographing, ware-cleaning,

enamel-brushing, and the like, are best carried out at benches under

hoods with glass tops. Air will enter from in front, and carry the dust

or spray away into the exhaust duct placed at the back of the bench.

[Illustration: FIG. 5 shows a pan mill with edge runners fitted with

casing (partially open). The casing is connected to a powerful fan,

and branch ducts with telescopic terminal sections control the dust

in scooping out from the barrel, in feeding into the mill, and at the

point where the ground material is discharged.]

=Collection of Dust.=--Frequently no heed is paid to the collection

of the dust. Sometimes a dust chamber is arranged to intercept it on

the far side of the fan, or attempt is made to blow the dust into

a tank of water. The fine dust of which we are speaking cannot be

satisfactorily collected by either of these methods, nor even by a

cyclone separator, so useful for the collection of many kinds of dust.

In lead works generally, the dust removed by the fan is best collected

in filter-bags made of some porous fabric. Various efficient filters

constructed on these lines by Messrs. Henry Simon, Ltd.; Messrs. Beth

and Co., Ltd.; and the Sturtevant Engineering Company, Ltd., are on the

market.

[Illustration: FIG. 6 shows an arrangement of piping with balanced

telescopic joints fitted to a Sirocco dust fan for removal of dust, in

an electric accumulator works, when scooping out litharge from a cask

into the receptacle prior to emptying the weighed quantity into the

mixing machine, also under a hood connected with the exhaust system.

(Illustration supplied by Davidson and Company, Limited, Belfast.)]

In collecting the dust, care must be taken to provide an adequate

outlet for the spent air, so as to prevent creation of a source

of friction in front which might destroy the effectiveness of the

installation.

[Illustration: FIG. 7.--EXHAUST VENTILATION ON THE PATENT “PENTARCOMB” PRINCIPLE

APPLIED TO LINOTYPE AND MONOTYPE MACHINES IN PRINTING WORKS, AS

INSTALLED BY THE ZEPHYR VENTILATING COMPANY, BRISTOL.

P, Patent “pentarcomb” for equalizing exhaust; V, patent “pentarcomb”

for general ventilation; D, main and branch ducts; F, fan; U, upcast

from fan; M, hoods over metal-pots of monotype machines, constructed

to raise and lower, and swing out and in with metal-pot; L, hoods over

metal-pots of linotype machines, constructed to raise and lower.

In the illustration “pentarcomb” grids connect the branch ducts over

the metal-pots of mono and linotype machines with the main duct. The

“pentarcomb” grids are arranged also elsewhere in the main duct itself

to assist in the general ventilation of the workroom. The hoods over

the metal-pots are constructed to be raised and lowered, and to swing

out and in radially with the melting-pot arm. (Drawings supplied by the

Zephyr Ventilating Company, Bristol.)]

In order to secure equality of flow from a number of branched ducts,

the Zephyr Ventilating Company apply a special grating of curved and

slanting inlets--the “pentarcomb”--to each branch duct. The air

passing through the comb is split up into numerous small columns, and

the inclination of the curve which each is made to take is such as to

reduce friction to a minimum. By means of this device we have found,

in a trunk with twenty branches, the draught at the one farthest from

the fan as serviceable as that next to it. The method is illustrated

applied locally to remove the fumes from linotype machines, and

generally in the main duct for removal of foul air near the ceiling.

Where electricity is available as a motive power for driving the fan,

some modification in the views expressed as to the curvature of the

pipes and system of installation can be allowed. In a red lead plant,

for instance, it may be desirable to have the pipes leading to the

sifter or packing machine with sharp angles, so as to prevent tendency

of such heavy dust to collect in them. The electric current allows a

fan to be installed at any point desired; and if applied with knowledge

that the increased friction due to an acute angle has to be overcome,

the result may be quite satisfactory.

The various forms of vacuum cleaning apparatus with mouthpieces

designed to aspirate the dust from different surfaces are sure

to be increasingly used. In our opinion, wherever electric power

is available, they will obviate barbarous methods involving use

of hand-brushes to collect dust from machines, such as those for

litho-dusting or for sweeping lead dust from benches and floors, or use

of bellows to blow out the dust from compositors’ cases.

Finally, the carrying out of lead processes by automatic methods and

with the interior of the casing under a negative pressure, so that

the material is transported from one process to another by means of

worms or conveyors, is everywhere to be aimed at. Or, again, it has

been found possible on a commercial scale, by means of compressed air

in a closed system of receivers and pipes, to force material in very

fine state of division from one place to another, as, for instance, of

litharge from the cask into the mixing machine for preparation of the

paste for manufacture of accumulator plates, without risk of contact.

Indication of the efficiency of the draught may be gained by holding

smoke-paper at the orifice of the hood. The definition of efficient

exhaust in some regulations for the removal of fumes, as in the Tinning

Regulations, is that it shall not be deemed to be efficient unless

it removes smoke generated at the point where the fume originates.

Accurate gauging, however, of the draught can only be done with an

anemometer, so as to determine the number of linear and cubic feet

passing through the throat per minute. Only rarely does one find an

occupier alive to the value of the use of such an instrument. The

importance of this point has been recognized in the Regulations for

Heading of Yarn, by the requirement that the speed of each exhaust

opening shall be determined once in every three months at least,

and recorded in the general register. We prefer to use Davis’s[A]

self-timing anemometer, which gives readings in feet per second without

the need of a watch. Other useful anemometers--Casella’s or Negretti

and Zambra’s--require to be timed.

[A] It is not available for velocities exceeding 1,200 linear feet

per minute.

The details of all routine observations on localized exhaust

ventilation might well be entered on a card hung up in the workroom.

Such a card drawn up by our colleagues, Miss Lovibond and Mr. C. R.

Pendock, has the following headings:

FIRM............................... PROCESS...........................

FANS: No..... Kind................ Size....... Maker.................

Motive power........ H.P........ Method of driving.....

Other load.......... Condition of driving..

Screen.............. Dust col-

Direction........... lection....

Periodic cleaning...

HOODS: No..... Kind................ Size.......

Structure...........

Distance between each..

DUCTS: No..... Kind................

Size................ Length..... Section...............

Structure...........

Periodic cleaning...

FRESH-AIR

INLETS: No.... Kind................

Position............

Size................

Fixed or temporary..

+-------+--------+--------------------+-------+------------+---------+

| Refer-| of | | | |

+-------+--------+-------+-----+------+-------+-----+------+---------+

| | |Area of| F. | C.F. |Area of| F. | C.F. | |

| | |Throat.| p.m.| p.m. |Throat.| p.m.| p.m. | |

+-------+--------+-------+-----+------+-------+-----+------+---------+

| | | | | | | | | |

+-------+--------+-------+-----+------+-------+-----+------+---------+

Frequent cleaning and inspection of exhaust installations are very

important, as accumulation of dust greatly impedes the flow of air

at all points of the system. The person employed in cleaning the fan

should wear a respirator. Hoods and ducts should always be cleaned with

the exhaust in full action.

REFERENCES.

[1] Annual Report of the Chief Inspector of Factories for 1910, p.

172.

[2] _Ibid._, pp. 172, 173.

[3] G. ELMHIRST DUCKERING: A Report on an Experimental Investigation

into the Conditions of Work in Tinning Workshops, and Appendices.

Included in Special Report on Dangerous or Injurious Processes in the

Coating of Metal with Lead or a Mixture of Lead and Tin. Cd. 3793.

Wyman and Sons, Ltd. Price 1s.

G. ELMHIRST DUCKERING: The Cause of Lead Poisoning in the Tinning of

Metals. Journal of Hygiene, vol. viii., pp. 474-503, 1908.

G. ELMHIRST DUCKERING: Report on an Investigation of the Air of

Workplaces in Potteries. Included as Appendix XLIX. in Report of

the Departmental Committee appointed to inquire into the Dangers

attendant on the Use of Lead, and the Danger or Injury to Health

arising from Dust and Other Causes in the Manufacture of Earthenware

and China, vol. ii., pp. 93-113, 1910. Cd. 5278. Price 1s. 9d.

[4] G. ELMHIRST DUCKERING: Annual Report of the Chief Inspector of

Factories for 1910, p. 47.

[5] C. R. PENDOCK (one of H.M. Inspectors of Factories): Report on

Systems of Ventilation in Use in Potteries. Included as Appendix

XLVIII. in vol. ii. of Potteries Committee’s Report referred to

under[3].

C. R. PENDOCK: Second Report of the Departmental Committee appointed

to inquire into the Ventilation of Factories and Workshops, part i.,

and especially part ii., 1907. Cd. 3552 and 3553. Price together, 4s.

8d.

Other works referred to include--Construction des Usines au Point de

Vue de l’Hygiène, by Ingénieur-Architecte Maniguet. Ch. Béranger,

Paris, 1906; Hygiène Industrielle, by MM. Leclerc de Pulligny,

Boulin, and others. J. B. Baillière et Fils, Paris, 1908; and many

excellently illustrated trade catalogues issued by ventilating

engineering firms, such as the Sturtevant Engineering Company, Ltd.,

London; Henry Simon, Ltd., Manchester; Davidson and Company, Ltd.,

Belfast; John Gibbs and Son, Liverpool.

CHAPTER XIII

PREVENTIVE MEASURES AGAINST LEAD POISONING--_Continued_

=Periodical Examination.=--In various codes of regulations a surgeon

is required to make periodical medical examination of the workers.

The term “surgeon” is defined as the “Certifying Factory Surgeon of

the district, or a duly qualified medical practitioner, appointed

by written certificate of the Chief Inspector of Factories, which

appointment shall be subject to such conditions as may be specified

in that certificate.” The wording of the regulation varies somewhat

in different codes, but the intention in all is the same, and the

following example from the Tinning Regulations will indicate the

purpose and scope:

“Every person employed in tinning shall be examined by the surgeon

once in every three months (or at such shorter or longer intervals as

may be prescribed in writing by the Chief Inspector of Factories),

on a day of which due notice shall be given to all concerned. The

surgeon shall have the power of suspension as regards all persons

employed in tinning, and no such person after suspension shall be

employed in tinning without written sanction from the surgeon entered

in the health register.

“Every person employed in tinning shall present himself at the

appointed time for examination by the surgeon. No person employed

in tinning shall, after suspension, work at tinning without written

sanction from the surgeon entered in the health register.”

Under the Special Rules for white-lead works, examination is required

at weekly intervals; under the Special Rules for Earthenware and

China, Manufacture of Litho-Transfers and Red Lead, and under the

Regulations for Electric Accumulators, and Paints and Colours, monthly;

under the Regulations for Tinning, Yarn dyed with Chromate of Lead,

and Enamelling, at quarterly intervals, subject to the limitation or

extension specified in the regulation quoted.

The limitation as to quarterly examination is useful to meet

conditions, on the one hand, where special incidence calls for

increased safeguards; and, on the other, relaxation, by reason of

adoption of special processes or measures lessening risk. Thus, in

a yarn-dyeing factory, in consequence of occurrence of six cases

within five months, a weekly instead of a quarterly examination was

prescribed. After eight months, as no further cases were reported, a

monthly examination was substituted for the weekly, and eventually,

with continued absence of illness, the normal quarterly examination was

resumed.

An appointed time for the surgeon’s attendance at the factory has been

found necessary, because, in conformity with the literal wording of the

regulation, the occupier should not continue to employ a worker who,

for one reason or another, has not been examined by the surgeon during

the prescribed interval. With knowledge of the date and hour posted

in a conspicuous place in the factory, excuse for absence becomes

difficult. Alteration by the surgeon of his appointed time should,

whenever possible, be given beforehand. Surgeons in the past frequently

made examination of the persons employed with the view of taking them

unawares, and so of precluding special preparation beforehand--a

practice which had its advantages; but they are outweighed by the

hardship inflicted on workers who were unavoidably absent, as, for

example, night-workers. A health register is supplied to all occupiers

where periodical medical examination is enjoined, the headings of which

and manner of entry are indicated later on in this chapter.

The objects which the surgeon should have in mind in making his

examination are:

1. To prevent lead poisoning and minimize lead absorption.

2. To obtain information for the occupier and Inspector of Factories of

the relative danger of one process and another with a view to adoption

of remedial measures.

In safeguarding the health of the workers, he should make effort to

gain their confidence, in order to be able to attach proper value to

statement as to subjective symptoms. Suspicion in their minds that the

examination is made solely in the interests of the employer militates

against success, and increases inclination to conceal symptoms and

to give untruthful answers as to the state of health since the last

examination. In our opinion, the surgeon will best carry out the first

object by attention to the second. The study of thousands of reports

on cases of lead poisoning convinces us that 90 per cent. at least are

due to inhalation of dust and fumes. The surgeon, therefore, should

utilize the earliest sign of lead absorption to warn the occupier and

inspector of conditions favourable to the development of plumbism, and

due probably either to some unguarded spot in the manufacturing process

whereby dust or fumes are not being removed completely, or to ignorance

or carelessness (often excusable in the absence of proper instruction)

on the part of the worker. He should direct, therefore, especial

attention to new workers, not only because of their need for guidance

as to precautions to be observed and greater liability to attack

during the first year of employment, but also because development of

signs in them constitutes the surest guide to defects in the process

of manufacture. Occasionally symptoms in a worker may be so menacing

as to demand immediate suspension, but generally before the power is

exercised attempt to rectify the condition which gives rise to them

should be made. The surgeon can do much by influencing the foremen and

forewomen, who will necessarily come before him for examination, in

insisting on the supervision by them of care and cleanliness by the

workpeople under their charge. Should suspension, despite attention in

the manner suggested, be necessary, he will recognize that transference

to a non-lead process, if feasible, is preferable to entire cessation

from work in very many cases. The surgeon, therefore, should know what

departments are possible alternatives to lead work.

The fact that an examination is made on factory premises, is directed

to detection and prevention, treatment taking a subordinate place, and

is often made on persons who, unlike hospital patients, seek to conceal

their symptoms, causes it to be an examination _sui generis_. Hence

the surgeon must trust his sight more than his hearing. A surgeon with

experience of such work has said: “The worker in lead must be surveyed

as an individual, and idiosyncrasies must be carefully studied and

allowed for; the ‘personal equation’ is of vital importance”[1].

For the examination a well-lighted room affording privacy is essential.

While it is desirable for the surgeon periodically to see the processes

and conditions under which work is carried on, systematic examinations

of workers should not be made elsewhere than in a private room. The

custom of marshalling workers in a queue, although perhaps unavoidable

in many cases, is liable to detract from the seriousness of the

proceedings, a sense of which it should be one of the aims of the

examination to arouse. In discussing the method of interrogation and

usual examination, Dr. King Alcock[2], Certifying Factory Surgeon of

Burslem, says: “Note the general manner assumed in answering questions

and any indications of carelessness in dress and toilet. Inquire

into the state of digestion, existence of colicky pains, regularity

of bowels, menses, history of pregnancies and miscarriages, whether

before, in the intervals of, or during lead employment; existence of

headache, diplopia, or amaurosis. Note the type, facies, state of teeth

and nails, complexion, speech, tongue, strength of grasp (if possible,

with dynamometer), any tremor in outstretched hand, resistance to

forcible flexion of wrist.... If strabismus is present, note whether of

old standing or recent; and if ocular troubles seem imminent, examine

for optic neuritis, either at once or at home (this is very important,

as cases of acute and serious optic neuritis still baffle examination

by their intermensual development).” He recommends the surgeon, apart

from entry in the health register, which must necessarily be very

brief, to keep a private notebook, and to enter in it as a matter of

routine such details as name, process, age, duration of employment,

condition (married or single), pregnancies, state of bowels and menses,

dental toilet, and any special point worthy of note in individual

workers. A card index, if in use, might conveniently serve for such

entries.

In the actual routine examination it may be useful to describe the

procedure where a large number of workers pass before the surgeon in a

white-lead works every week. The points noted are:

1. The general appearance of the man as he walks forward, especially

the face with regard to anæmia, which in the majority of cases of early

lead absorption is not a true anæmia, but is due to vaso-motor spasm

of the arterioles of the face and eyes. Frequently, on speaking to a

lead-worker, the face, apparently anæmic, flushes directly.

2. The brightness of the eyes, state of the pupils, and condition of

the conjunctiva and of the ocular muscles.

3. The mouth should next be examined, and search made for any evidence

of blue line around the gum.

4. The gait should be watched both on advancing to, and retiring from,

the surgeon. If necessary, the man should be made to walk a few steps.

Although the peroneal type of palsy is extremely rare, the possibility

of its occurrence should never be absent from the mind of the surgeon.

5. The man should then be directed to stretch his hands out in front

of him, with wrists extended and fingers widely spread. Presence

or absence of tremor should be looked for, and the condition of the

finger-nails, as to the practice of biting, etc. The extensor power

should then be tested, firstly of the fingers. While the hands of the

workman remain outstretched, the surgeon places the forefinger of his

hand in the outstretched palm of the workman, and the ball of the

thumb upon the extreme tip of each finger, and by gently pulling it

down, noting the spring present in the muscles. This test is probably

the most delicate there is for detection of early extensor paralysis.

The condition of the lumbricals and interossei are noted on movement

of the fingers. The extensors of the wrist are then further examined,

the workman being directed to flex his arm at the elbow and strongly

pronate the wrist, so that the palm of the hand is directed forwards.

He is then told to close the fist when the surgeon endeavours to flex

the wrist, the workman at the same time resisting by forcible extension

of his wrist. Ordinarily the extensor communis digitorum and minimi

digiti are sufficiently powerful to resist a very powerful pull upon

the wrist; and if the wrist is found to yield, it is a sign that the

muscles are affected. Sometimes the strength of the wrists and fingers

is judged by the surgeon placing his palms on the dorsum of the

patient’s outstretched hands, and seeing whether the patient can be

prevented from lifting them without flexing the wrists or finger-joints.

The test detects (1) paralysis which has been recovered from to a large

extent; (2) commencing partial paralysis; and (3) weakness of muscular

power, especially in those who have worked in lead for a number of

years. This weakness appears to be an effect of lead upon the muscular

tissue or dependent on debility, the result of lead absorption, and

independent of nerve implication. We have known the condition to remain

unaltered for years, and also to undergo alteration, being at times

absent for months together. Occasionally reports of definite paralysis

refer to pre-existing weakness.

6. The pulse is next noted. The pulse-rate need not ordinarily be

counted, but if it is either very slow or fast careful examination at

the conclusion of the general inspection should be made.

It is well to make all these points before asking any questions. After

they are completed inquiry as to regularity of the bowels, existence

of pain or discomfort, would follow. The speech should be noted, as

slurring or hesitating speech is occasionally associated with early

lead poisoning.

All these points can be gone through quite rapidly, and at the

conclusion of the general examination, if judgment is in suspension,

careful examination in the routine medical manner should be made.

In some factories all new workers are examined by the surgeon before

they commence work in dangerous processes. At any rate, a list of such

persons should be given to the surgeon at his visit, as naturally

the question of personal fitness for employment should be decided

at his first examination. Conditions which should lead to rejection

are tubercular disease of every kind, idiopathic epilepsy, all forms

of mental disease or weakness (hysteria, feeble-mindedness, and

neurasthenia), obvious alcoholism, women who are pregnant or who give

a history of repeated miscarriages prior to work in lead, persons with

marked errors of refraction unless corrected by glasses, kidney disease

of all kinds, evidence of previous chronic saturnism, and bad oral

sepsis. Special attention will have to be paid to casual labourers, and

it should be the aim of the surgeon to discourage this class of labour

in lead industries. Work under special rules or regulations requires

to be carried out under strict discipline, and this it is extremely

difficult to maintain on other than regular workers, who recognize the

need for cleanliness and observance of regulations.

Other aids to diagnosis cannot be carried out as a matter of

routine, but will necessarily be used in particular cases, such as

ophthalmoscopic examination of the fundus, electrical reactions of

muscles, analysis of the urine, and examination of the blood-pressure.

A few words may be added on the significance of the two commonest

signs--the blue line and anæmia. It cannot be too strongly insisted

on that presence of the Burtonian line on the gums is, as a rule,

indicative of lead absorption, and not of lead poisoning. As a

danger signal its value is immense, and hardly less so its value in

clinching diagnosis in doubtful cases. Whenever the line is seen risk

is imminent, and poisoning (not necessarily of the individual in whom

it is pronounced) among the workers is inevitable in the absence of

adoption of precautions. Unfortunately, careful dental toilet, which

the surgeon will necessarily lay stress on, may prevent development,

or the practice, when adopted, cause disappearance of the line after

the lapse of a few months. Under these circumstances, the merest trace

will have all the significance of the fully-developed line in a worker

neglectful of care of the teeth. Among new workers a commencing blue

line should be strong evidence of the need for dust removal at some

point in the process of manufacture. The line, in our experience, is

dense in occupations giving rise to fumes or to dust of compounds of

lead, but comparatively rare in those handling metallic lead or its

alloys, as compositors, tea-lead rollers, solderers, and the like.

Some degree of pallor is so commonly met with in adolescence that it

is the progressive development of the anæmia which the surgeon must

especially watch for. As a danger signal, therefore, it has the same

significance nearly as the blue line; but when lead absorption has

affected the elements in the blood, progressive anæmia in new workers,

attributable to the employment, and showing no tendency to improve

after watching for a few months, is an indication for suspension or

transference to other work. In older workers, with a duration of

employment of five years or more, there may be a quasi-pathognomonic

pallor which does not vary from year to year. In them it must be

supposed that an equilibrium has been established, and development of

other symptoms, such as tremor, wrist weakness, or albuminuria, becomes

significant. Attention has already been directed to the distinct

saturnine facies associated with anæmia, and characterized by loss of

fat, particularly noticeable in the orbit and buccinator region of the

face. “So far as the question of any worker’s suspension is concerned,”

says Dr. King Alcock, “I prefer to make my instinctive _primâ facie_

distrust of a saturnine pallor the basis for action. The pallor of

plumbism cannot be summed up in hæmoglobin and corpuscular content;

it is the expression of a complex toxæmia resulting from defective

assimilation and excretion”[3].

The knowledge the surgeon should gain of the idiosyncrasies of the

workers by his periodical examination will enable him to appraise at

their proper value the nature and degree of the symptoms in notified

cases.

Sometimes a rule is made that no lead-worker who has suffered from an

attack of plumbism should be allowed to resume work. This we consider

too harsh a measure. It may be true for painters, but when remedial

measures, such as locally applied exhaust ventilation, can be applied,

with consequent removal of the danger in the process at which the

poisoning has arisen, prohibition of employment seems an unnecessarily

drastic measure.

The health register in general use where periodic medical examination

is required in pursuance of special rules and regulations is divided

into two parts, in each of which entries by the surgeon are required at

each visit.

PART I.

+--------------------------------+-------------------------------+

|List of Persons Employed in | Particulars of Examination. |

| Processes.| |

+---+--------+--------+----------+-------+-------+-------+-------+

| | Name, | +----+-----+-------+-------+-------+-------+

+---+--------+--------+----+-----+-------+-------+-------+-------+

|(1)| (2) | (3) | (4)| (5) | (6) | (7) | (8) | (9) |

| | | | | | | | | |

+---+--------+--------+----+-----+-------+-------+-------+-------+

PART II.

+----------+------------+---------+---------------------+---------+

+-----+----+ Date of | Persons | of Work must be | of |

+-----+----+------------+---------+---------------------+---------+

| (1) | (2)| (3) | (4) | (5) | (6) |

| | | | | | |

+-----+----+------------+---------+---------------------+---------+

In Part I. of the register the surgeon should, at the times of

examination, enter the date at the head of one of the columns numbered

6 to 9; and in the space below, opposite the name of each person

examined on that date, a brief note (see next page) of the condition

found.

In Part II. he should again enter, in Column 3, the date of

examination, with a statement of the total numbers examined on that

occasion (Column 4); and in Column 5 any certificate of suspension from

work, or certificate permitting resumption of work, and particulars of

any other direction given by him, appending his signature in Column 6.

It is the duty of the occupier to enter in Part I. the following

particulars with regard to each person examined: (1) Name in full

(Column 2); (2) the process in which he or she is employed (Column

3); (3) age when first employed (Column 4); and (4) date of first

employment in that process (Column 5); and these particulars, in

respect of each person so employed, must be entered immediately on

commencement of work in the process named.

Various methods of noting the state of health of the workers have

been adopted. Use of the words “Good,” “Very fair,” and “Fair,” is

common as indicating the state of general health, with special note in

addition, often in the form of a symbol, of the presence and character

of definite ill-effects. The object of the register, however, is to

keep a record intelligible not only to the Certifying Surgeon, Factory

Inspector, and occupier, but also to the workers. Entries, therefore,

on a uniform system are desirable, taking account of the two aspects of

the health of every lead-worker, which must be considered (_a_) that

indicative of specific effects from the occupation, and (_b_) that of

general health uninfluenced by the employment. With this in mind, the

following system of entry in the health register has been adopted:

The entries should be made upon a uniform system, as below,

indicating degrees of deviation from normal health, and

distinguishing (by use of _numerals_) those attributable (or possibly

attributable, in whole or part) to work in lead, from those not

so attributable, for which latter _letters_ should be used. The

conclusion is perhaps best expressed as a fraction

1 2

---, ---,

A C

and so on.

The numerals should be taken to mean:

1. Passed without comment (no observed effect of lead).

2. Blue line (or indication thereof).

3. Marked (quasi-pathognomonic) anæmia, or other signs of impairment

of health. (Albuminuria, or slight deficiency in tone of the extensor

muscles of the forearm, would, and miscarriage, or other suspicious

history of illness between examinations, might, come under this head.)

4. Suspension or transfer, by reason of impairment of health from

effects of work in lead. (In such cases the surgeon would be prepared

to entertain an application for a certificate under the Workmen’s

Compensation Act.)

Except in the case of a worker whose exposure to lead is only recent,

renal disease should always be indicated by a numeral.

Letters should bear the following meaning:

A. No comment (_i.e._, fair general health).

B., C. Increasing degrees of impairment of general health.

(Pregnancy, if without suspension, should be entered as C.)

D. Suspension or transfer, for reasons other than impairment of

health from effects of work in lead.

X. Carelessness, or neglect of precautions, or unsuitability for work

in lead. (Suspensions for such reasons should be marked DX.)

Such entries of numerals and letters will in general suffice for the

intended purpose; but the surgeon may, of course, find it desirable

to make other notes for his own information, and it is within

his discretion to supply further details to occupiers or workers

concerned.

REFERENCES.

[1], [2] S. KING ALCOCK, B. M. BOND, A. SCOTT and others, in

discussion on the Value of Systematic Examination of Workers in

Dangerous Trades. Brit. Med. Journ., vol. ii., pp. 741-749, 1902.

[3] KING ALCOCK: The Early Diagnosis of Industrial Lead Poisoning.

Paper contributed to the Second International Congress for the Study

of Industrial Diseases held at Brussels, 1910.

CHAPTER XIV

PREVENTIVE MEASURES AGAINST LEAD POISONING--_Continued_

=Overalls and Head Coverings.=--Stress has been laid on the wearing

of overalls and head coverings in processes giving rise to dust or to

splashes of glaze or paint in special rules and regulations in the

past. With the improvement that has taken place in exhaust ventilation,

they have become less important. Indeed, the aim of all manufacturers

and ventilating engineers should be to render processes so free of dust

as to make them altogether unnecessary. Increasing knowledge of the

insidious manner in which lead dust can arise has shown that from this

point of view overalls of the cotton or linen material ordinarily worn

constitute a real source of danger. Splashes of glaze dry on them, and

at every movement involving rubbing of the surface dust is generated.

Some operations almost oblige the worker to press the article worked

upon against the chest, so that chance of inhalation of dust from

this source alone is considerable. Taking them off creates dust, and

after this is done a reprehensible practice exists of either shaking

or beating them against a post. In large factories they are usually

washed on the premises, and the water in which this is done will become

a solution containing some lead in suspension. Hence, even when washed

and dried ready for wear, overalls may not be quite free of lead. Apart

from the general obligation recognized that an employer should provide

and maintain everything necessary to guard against danger contracted

in his factory, we think that the risk run by a worker in taking the

overall home and washing it there is negligible, and offers advantages

in the ultimate cleanliness of the overall over washing on factory

premises. Laundresses shaking overalls prior to washing them have been

known to contract plumbism.

Where work with the arms is incessant, as in the heading of yarn,

overalls are burdensome, and for this reason and the fact that with

efficient exhaust ventilation there should be practically no dangerous

dust, the regulations for the heading of yarn enjoin provision of them

only on written certificate of the Chief Inspector of Factories.

Protection for the clothing, however, where splashing is incidental to

the operations, cannot be dispensed with. Hence either the overalls

themselves or the front of them should be made of some light ventilated

waterproof material, or a waterproof apron worn over overalls of the

kind at present in use. Daily sponging would then take the place of

washing.

If lead dust be visible on the hair of workers, there must be a defect

in the conditions of work to be rectified by other means than cumbering

the head. In our opinion, head coverings ought never to be necessary.

We cannot think that an attack of plumbism can ever be precipitated by

the amount of lead dust inhaled on brushing the hair.

A common provision in regulations for overalls is:

“Overalls shall be provided for all persons employed in lead

processes, and shall be washed or renewed every week.

“The occupier shall provide and maintain for the use of all persons

employed in lead processes--(_a_) A cloakroom or other suitable place

in which such persons can deposit clothing put off during working

hours, and separate and suitable arrangements for the storage of

overalls required by regulation; (_b_) a dining-room, unless all

workers leave the factory during meal-hours.

“All persons employed in lead processes shall wear the overalls

provided ... and shall deposit such overalls and any clothing put off

during working hours in the places provided under the regulations.

The overalls shall not be removed by persons employed from the

factory or workshop.”

General sense of propriety--and it is on this ground, and not from

danger attaching to non-observance, that we press it--suggests that

overalls should be kept apart from working clothes, and preferably

outside any room in which a lead process is carried on. So long as

actual contact between the two sets of garments is prohibited, we

do not see objection to the same cloakroom sufficing for both. The

best arrangement that we have seen is a room in which each worker

has two lockers--one for the storage of overalls, and the other for

clothing put off during working hours. This presupposes supervision

and effective discipline. We think that all reasonable need in the

provision to be made is met by numbered pegs on one side of the room

or wide passage for clothing, and on the other pegs correspondingly

numbered for the overalls. Means for heating and drying the clothes

should not be overlooked (see Fig. 8).

[Illustration: FIG. 8 shows a good arrangement in a white-lead

factory, by which, as is best, cloakroom, meal-room, and washing and

bath accommodation, are all under one roof. The men on entering hang

up their clothes in the private clothes lobby, and pass through the

swinging doors to the lobby where the overalls are hung. On leaving the

factory and at midday they enter by the door leading into the lobby

for storing overalls, and from that pass to the lavatory and bathroom.

Having washed and put on their ordinary clothes, they enter the

meal-room. The building throughout is lined with white glazed bricks.]

[Illustration: FIG. 8A.--WELL LIGHTED MESS-ROOM IN A SMELTING WORKS.]

=Meal-Room Accommodation.=--Wherever lead processes are carried on the

provision of a mess-room is called for in a part of the factory remote

from possible contamination from lead dust. This we hold on general

grounds of cleanliness and self-respect, and not because we think the

eating of meals in rooms where lead is used would noticeably increase

the number of cases. The more conveniently situated in relation to the

workrooms the mess-room is, the more will it be used. Set out briefly,

the requirements of a mess-room are that it should be--

1. Well ventilated, warmed, and lighted.

2. Not less than 10 feet high, and with floor-space ample for each

person likely to occupy it at any one time.

3. Have walls the surface of which is smooth and impervious to a height

of at least 4 feet from the ground.

4. Have pigeon-holes or other arrangement in which each person can

deposit his food separate from that of others.

5. Have means of warming and cooking food.

6. Be kept properly clean and dry.

No part of a factory becomes so unsightly in the absence of daily

cleaning as a mess-room, especially where provision has only to be made

for five or six workers.

Reid[1] has suggested the following scale of floor-space per person in

mess-rooms:

6 persons and under 10¹⁄₂ square feet per person.

Over 6 and up to 12 7¹⁄₂ „ „ „

„ 12 „ 20 6 „ „ „

„ 20 „ 28 5¹⁄₂ „ „ „

„ 28 and any number 5 „ „ „

In a factory well known to us for manufacture of white lead there is

a restaurant originally started in connection with the sick club of

the factory. For fivepence the workman obtains a hot meal of meat,

bread, and vegetables. Any profits go to the sick fund. Since this has

been started improvement in the physical condition of the men has been

marked; several cases of anæmia and malnutrition have entirely cleared

up. No workman, as has already been emphasized, should commence work in

a lead factory unless he has had a good meal--that is, unless there is

some food at least in the stomach--particularly albuminous food, such

as milk, cocoa made with milk, or _café au lait_. The most suitable

foods generally for lead-workers are those containing proteids--meat,

eggs, milk, cheese, and fatty foods. Acids--vinegar, pickles, and the

like--are especially to be avoided.

Section 75 (2) of the Factory and Workshop Act, 1901, requires that,

where lead or other poisonous substance is used so as to give rise to

dust or fumes, meal-room accommodation shall be provided. The question,

as a rule, is easily decided, but there are border-line cases where

doubt may arise, as, for example, in letterpress printing factories

in regard to dust, and in soldering operations in regard to fume.

Operations in the composing-room undoubtedly give rise to dust, and in

stereotyping and casting the débris trodden underfoot causes dust to

rise. In linotype rooms, however, in the present state of knowledge, a

difficult burden of proof would rest on the person who sought to show

that dust or fumes were present to such an extent as to justify action

under the section. And the same view holds, in our opinion, in regard

to soldering.

=Lavatories.=--The usual requirement for this in nearly all regulations

is:

The occupier should provide and maintain in good repair for all

persons employed in lead processes--

(1) Suitable lavatory accommodation, including at least one lavatory

basin for every five such persons, fitted with a waste pipe, or

placed in a trough having a waste pipe, and having a constant supply

of hot and cold water laid on; or alternatively troughs of enamel or

similar smooth impervious material, fitted with waste pipes without

plugs, and having a constant supply of warm water laid on, and

affording a length of at least two feet of trough for every five such

persons.

(2) Soap, nail-brushes, and a sufficient supply of clean towels,

renewed daily.

Discipline, and responsibility placed on some one person to see to

the cleanliness of the lavatory appliances and adequate supply of the

necessary means for washing, can alone insure proper use of them by

the persons employed. The workman has so narrow a margin of time in

which to get his breakfast and dinner that he cannot be expected to

wash if facilities for doing so fail. The alternative of an enamelled

iron trough with jets of warmed water is in our experience much the

most satisfactory installation where the number employed is more than

five or six. Provision of soft soap or of soap in the form of powder,

and nail-brushes nailed to the table, hinder peculation. Wooden stands

for holding wash-basins present almost invariably a most uninviting

appearance unless covered with sheet lead.

Well-equipped wash-hand basins with hot and cold water laid on close

to the work-place are sometimes provided in addition to the lavatory

proper. If looked after they are valued and used, but if not they

become converted into receptacles for oddments.

[Illustration: FIG. 9.--GOOD WASHING AND BATH ACCOMMODATION IN A LEAD

SMELTING WORKS.]

[Illustration: FIG. 10.--WASHING TROUGH, DOUCHE BATHS, AND CLOTHES

CUPBOARDS.

Type common on the Continent.]

Roller towels should be at least 15 square feet in area for every three

persons employed, and renewed daily.

The merits of soluble sulphides in “akremnin” soap have been advanced

on the ground that the lead is converted into the insoluble black

sulphide, which is thereby made visible to the eye, and the sight of

which will, it is hoped, still further stimulate the desire to wash.

Probably such lead as remains on the hands after well washing with soap

is so closely adherent to the skin as to render risk of contamination

of the food in this way negligible. Dr. Robertson, Chemist of the Royal

Gunpowder Factory at Waltham Abbey, has found that results as good

as those to be obtained from use of akremnin soap (and without any

discoloration of the skin) are obtained from use of a solution made up

as follows: Sal ammoniac added to saturation to a solution containing

8·5 c.c. of commercial hydrochloric acid (specific gravity, 1·15) per

100 c.c. of water. The procedure adopted at Waltham Abbey is--(1) Usual

washing with soap, water, and a nail-brush; (2) scrubbing with the

special solution by means of a nail-brush dipped in it; (3) rinsing in

water; and (4) washing with soap and water.

Sommerfeld[2], from his wide experience, considers that pumice-soap,

with the addition of turpentine, is the best cleansing material

lead-workers can use.

=Baths.=--Provision of bath accommodation is required under the special

rules for white-lead factories and the regulations for electric

accumulators. In several factories, however, baths are provided

for the use of the workers. They naturally make for improvement in

general health, but we cannot regard provision of them, any more than

cloakrooms and mess-rooms, as likely to influence materially incidence

of lead poisoning in a factory. The three requisites of (1) convenience

and quickness, (2) comfort, and (3) regular use, can best be secured

by the use of shower baths in place of slipper baths. The advantage

they have are--(1) Initial cost of installation is less; (2) economy

in space; (3) economy in water; (4) economy in time required for

bathing; (5) no worker comes into contact with water used by another;

(6) cleansing must be from the head downwards. Danger of scalding can

be absolutely excluded by use of valve levers, so placed in relation to

one another that steam cannot be turned on until the cold-water valve

has been opened, and the heater can be so arranged that the water is

not raised above a definite temperature.

=Separation of Processes.=--Lead processes should, as far as possible,

be carried on in such a way that there is aerial disconnection of one

process from another. Separate workrooms, although desirable unless

very small, may not always be possible, but by exhaust ventilation

processes may be arranged so that dust is not a source of danger to

persons working elsewhere. Instances could be given where, in paint and

colour works, persons employed in the grinding of earth colours, in

which no lead entered, succumbed to attacks of plumbism from contiguity

of the plant with that for grinding lead colours. Threading up of

castor runners on a wire previous to dipping used to be done, prior to

1901, in the dipping-house itself, with the result that some severe

cases of poisoning occurred. By the rules of 1901 the process was

required to be done in a place separate from any place where dipping

(or other scheduled process) was carried on, and very few cases have

occurred since. And if exhaust ventilation is relied on, Duckering’s

experiments (p. 206) show the attention to detail necessary to prevent

air charged with lead dust being drawn to the spot by the fan. The need

for separation of processes becomes less in proportion as the cubic

space of the room increases, and dust and fumes are locally removed.

=Age of Employment.=--The same considerations as have been stated

above govern this point also. Wherever lead dust or fumes arise,

whether exhaust ventilation is applied or not, persons of either sex

under eighteen years of age are probably rather more susceptible to

attack by reason of natural failure to appreciate the risk run. When

periodical medical examination in addition to exhaust ventilation has

been adopted, the age limit can safely be reduced to sixteen. Where

handling only of metallic lead and ordinary soldering with an iron are

done, risk of contracting plumbism is so remote that an age limit may

be unnecessary.

=Wall Surface.=--Wherever walls are likely to be splashed, as in

dipping rooms and enamelling workshops, the inner surface of the walls

should be of glazed bricks or tiles or enamelled plates, any of which

help also in increasing the light necessary in such rooms. If, on

account of the cost, such perfectly smooth material is impracticable,

the walls should be painted with oil colour, which will enable them

periodically to be wet-cleansed. Dusting the walls is to be deprecated.

Hence accumulations of dust and débris on ledges, rafters, beams,

roofs, etc., should, in our opinion, only very occasionally be cleaned

down. We consider that the risk from one big cleaning down is less than

that from repeated small ones. (See p. 218).

=Floors.=--These should be smooth and impervious. Wood flooring can

hardly be regarded as coming within this category; it is unsuitable

where lead processes are carried on. Preference must be given to floors

of concrete and the like material, which can be washed down easily

rather than swept. Frequently the dust raised in sweeping the floor

has determined an attack of lead poisoning. No objection can be raised

to wooden grids and iron roll matting placed on the concrete floor for

the workers to stand on. Cold feet and transference of lead dust by the

boots are lessened by their use. Where traffic is heavy, as is often

the case in lead works, vibration is set up with wooden floors, and

dust disseminated. In smelting works cast-iron plates are serviceable

as flooring.

=Instruction of the Worker.=--Too much stress cannot be laid on this

point. To insist upon it, however, is useless unless the occupier has

installed the necessary exhaust ventilation, and equipped his factory

with the other essentials for enabling the workman to guard against

dust and free his hands of adhering lead, in whatever form. When this

has been done, then the worker himself can do something.

Often he creates dust unnecessarily. In shovelling out of a cask with

spade or trowel, in order to get out the last trace of the material to

be transferred, he generally gives it a knock, which causes dust to

fly so sharply as to escape the exhaust; or he removes the implement

quickly from the exhaust, before it has been completely emptied and

while dust is still being given off. He will use a brush to clean his

bench in preference to cleaning it by a wet method. The printer may

hold type between his teeth. Many workers bite their nails. Moustache

and beard may be fingered, and because of this workers may even be

advised to be clean-shaven. They may chew or smoke constantly while at

work, and will frequently eat with unwashed hands.

Notices enjoining care and cleanliness may be, and often are, hung

up in the workrooms, or a leaflet, such as the one here printed, is

handed to the worker on his first examination by the surgeon. Nothing,

however, can take the place of actual verbal instruction from occupier,

foreman, and fellow-worker impressed with the importance of the matter.

LEAD POISONING: HOW CAUSED AND HOW BEST PREVENTED.

Unless great care is taken, work in lead and lead compounds is

injurious to health, because the lead enters the system and causes

lead poisoning.

Danger is greatest from breathing leady dust or fume, but eating with

unwashed hands, and biting nails or putting such things as sweets or

pipes into the mouth while the fingers are soiled with lead, all help

to cause poisoning.

Many workers in lead have a blue line round the edge of the gums,

but the first actual symptoms of the injurious action of lead on the

system are costiveness, colicky pains in the stomach, headache, and

marked paleness. Occasionally headache is associated with epileptic

fits, a very serious condition, which may be followed by loss of

sight. “Wrist-drop,” loss of power in the muscles moving the fingers

and wrist, results sometimes from lead poisoning, and may cause

permanent disablement from work. It does not usually come on until

after a person has worked in lead for some years.

Lead, even if absorbed in small quantities, has a tendency to remain

in the system, and if care be not taken it will go on accumulating,

so that in time the health may become permanently damaged, even

without any definite attack recognized as lead poisoning.

Girls and boys, because they are not so likely to observe the

necessary precautions as grown-up people, should be closely watched.

Women should be especially careful, as the injurious effect of

lead in them may seriously interfere with the healthiness of their

children.

As lead does not enter the system through the pores of the skin, it

can in great measure be avoided by--

1. Taking special care to avoid raising dust. It is to the interest

of everyone to see that ventilating arrangements are in order for

carrying dust away at the point where it is produced.

Any little cloud constantly made at work is sure, if breathed, to set

up lead poisoning. Where lead colours are used wet, danger arises

from the splashing of the material and its subsequent drying into

dust.

2. Paying scrupulous attention to cleanliness of the hands, face,

teeth, and clothing. The hands and nails should always be cleaned

with soap and nail-brush before food is eaten, and it is a wise

practice also to wash out the mouth. The teeth should be brushed at

least once a day, preferably before the evening meal.

3. Never commencing work on an empty stomach. Food containing fat,

such as bacon and milk, is suitable.

Overall suits, if worn, should never be shaken to rid them of dust.

They require washing at least once a week.

Aperient medicine, such as Epsom salts (one or two teaspoonfuls

in water), can be taken once or twice a week with advantage by

lead-workers.

Experience shows that the habits and home life of the workers

influence their liability to lead poisoning. Intemperate persons are

the first to fall victims. Those who begin work on an empty stomach

incur additional risk by so doing.

Carefulness while at work, and cleanliness, offer the best means of

escaping attacks of lead poisoning.

Those who work in lead should keep in mind every hour of every

working day the importance of not breathing lead dust and not

carrying lead to the mouth in any way.

Medical advice should at once be obtained if signs of lead poisoning

present themselves.

REFERENCES.

[1] GEORGE REID: Memorandum on Mess-room Accommodation: Appendix XXV.

of the Potteries Committee’s Report, vol. ii., 1910. Cd. 5278.

[2] TH. SOMMERFELD: Die Bekämpfung der Bleigefahr, edited by Leymann,

p. 76.

CHAPTER XV

DESCRIPTION OF PROCESSES

Lead smelting--Red and orange lead and litharge--Letterpress

printing--File-cutting--File-hardening--Tinning of metals--Plumbing

and soldering--Brass.

=Lead Smelting and Silver Refining.=--Lead poisoning very rarely occurs

in lead mining in Europe, as galena (sulphide of lead), the principal

ore in which the metal is found, is insoluble. Galena always, and other

lead ores very often, contain a small proportion of silver, ranging

from 0·001 to 1 per cent., and at times traces of gold. Owing to the

great affinity of lead for silver, lead smelting is necessarily a

process preliminary to the extraction of silver and gold from it[1].

Lead ores, drosses, etc., on arrival at the factory, are, after

sampling, deposited in bins or heaps (often in the open air), and

watered to prevent dust. All ores may, and refractory ores (containing

over 4 per cent. silica) and dross must, be smelted in a blast furnace

by aid of coke. The bulk of the charge in a blast furnace may consist

of more or less complex ores of the precious metals, especially silver.

When galena is treated in a blast furnace, preliminary roasting is

indispensable, and in many smelting works its treatment takes place in

a reverberatory or open-hearth furnace, and not in a blast furnace.

The three principal methods applicable to extraction of lead from ores

are--(1) The roast and reaction method; (2) the roast and reduction

method; and (3) the precipitation process.