Lead poisoning and lead absorption

by Sir Thomas Morison Legge; Kenneth Weldon Goadby

“The absence of lead poisoning among terne-plate workers and tinners would appear to be explained by—(1) The use of cleaning agents and a flux of such a nature, and in such a way, as to involve a minimum contact with the tinning metals, and under such conditions as to inhibit extensive interaction between them, and also under such conditions as to inhibit production of fume or vapours, even if any interaction occurs; (2) use of a scientifically prepared flux containing no uncombined acid or excess of water in such a way as to prevent introduction of these substances, or of ferrous compounds coming into intimate contact with the tinning metal; (3) so conducting the operation of tinning that any chlorides possibly adhering to the plates are removed before the plate reappears in the open air, under conditions preventing them from appearing in the air as vapour, but it is very doubtful whether any chlorides could adhere to the plates; and (4) absence of any manual work on the plates before the metallic coating is set and hard. On the other hand, the existence of widespread lead poisoning in tinning of hollow-ware is explained by—(1) Use of cleaning agents and flux in such a way as to bring these materials into intimate contact with the tinning metals under conditions eminently favourable to chemical interaction and vaporization of resultant compounds; (2) use of an unscientifically prepared flux containing a large excess of water and much free acid; (3) so conducting the operations as to favour the escape into the atmosphere of vapours of soluble lead compounds, such as lead chloride, and of metallic lead and soluble lead compounds, carried mechanically by fibres of tow during processes subsequent to tinning, as in wiping; and (4)—a minor point not to be lost sight of—possibility of contamination of the hands by soluble lead compounds, due to manipulating the material with which the articles are wiped.

“It should be added that while use of a scientifically prepared flux [(2) above] in hollow-ware tinning would no doubt lessen the possibility of the production of fumes, it is not to be anticipated (unless a flux containing no chlorides were used) that this would do away with lead poisoning. In other words, the method of use is, as indicated above, a far more important factor.”

In the ten years 1900-1909 the number of reported cases in tinning hollow-ware was 93 among about 200 persons employed, in harness furniture 23 among about 150 persons employed, and in iron drums and kegs 47 among about 250 persons employed.

Plumbing and Soldering.

—The figures included in the table on [p. 47] have reference only to these processes as carried on in factory premises. House plumbers, when reported, are included with house painters. The figures are made up of two classes—(1) Those handling white and red lead paste, and (2) those engaged in soldering and lead burning. The number of cases reported in the ten years 1900-1909 was, in the first class 122, and in the second 95.

Any worker using red lead as a jointing paste who is not a house plumber or a coach or ship builder is included under the first heading, as, for example, electricians, persons engaged in mechanics’ workshops, lead-light making where red lead cement is brushed between the lead lines and the glass to render them water-tight, and such occupations as placing strips of canvas coated with red lead between sheets of iron work before riveting, so as to afford protection against rust. In several reports there is reference to the dust created in the breaking up of old joints with aid of hammer and chisel before proceeding to recaulk them.

Dust in making up the paste is the principal source of danger. This is crudely done, and unless large quantities of paste are made exhaust ventilation is never provided, in view of the intermittency of the work. The wearing of a respirator should be possible, but it would be unsafe to recommend that as a sufficient means of prevention. Installation, whenever possible, of localized exhaust ventilation at the mixing bench is most desirable. Personal cleanliness is important, as the hands become ingrained with the paste.

The heading “Soldering” includes in the main (a) the soldering of tins of all descriptions, bicycle lamps, etc., with a stick of solder, either held in the hand or lying on the bench, which is touched by the hot soldering-iron, the surface to be soldered having previously been cleaned with “killed spirit”—i.e., zinc chloride flux; and (b) lead burning, by means of a hydrogen or oxy-hydrogen blowpipe flame, of lead-lined boxes, vats in sulphuric acid and other chemical works. Some cases are included which occurred in the manufacture of solder itself. Green wood is held at the bottom of the pot of molten metal, and the gases distilled from the wood pass upwards through the metal and escape at the surface, carrying small quantities of lead into the atmosphere of the workroom.

Dangers and Prevention.

—It can be confidently said of soldering that, bearing in mind the very large number of persons employed, the number of cases reported is remarkably small, and it is difficult to assert generally, as can easily be asserted of tinning, that inhalation of soldering fumes must necessarily set up lead poisoning. Moreover, examination of persons employed in soldering for signs of lead absorption is almost always negative, a blue line on the gums even being rarely visible.