—Some cases have occurred from the manufacture of capsules for bottles. The capsule consists of a lead leaf rolled between two leaves of tin. Cases arising in the early processes of casting and rolling do not differ from those described as due to contact with molten metal and handling of lead. The most difficult to deal with are those which occur in the final process of cleaning and colouring. Before colouring with varnish paint, the capsule is placed on a rapidly revolving lathe, and the hand of the worker, carrying a cloth containing whitening, is placed lightly on the capsule. A slight amount of dust is inevitably raised, and this dust, collected from the bench, was found to contain from 11·5 to 25·6 per cent. of lead; while dust which had settled on a beam 9 feet from the floor contained 9·3 per cent. Of thirty-one workers employed in cleaning and colouring, fifteen showed evidence of lead absorption in a blue line on the gums, and in one there was considerable weakness of the left wrist. Similar experience of lead poisoning in this industry has been noted in German and Austrian factories.
Periodical medical examination at quarterly intervals has been instituted in the principal factory, with good results, as it enables those who show early signs of lead absorption to be transferred to other processes. Exhaust ventilation has been tried, but, except at the few lathes where cleaning alone is done, without complete success, in view of the nature of the work.
Shot-making.
—Cases in shot-making arise from the dust given off when sifting the shot into different sizes—an operation which should be carried on in sieves entirely closed in and under negative pressure. Dust collected from the glass casing over a sifting machine contained 60·3 per cent. of metallic lead. The sample was free from arsenic.
Heading of Yarn dyed with Chromate of Lead.
—Cotton yarn is dyed (10) on a considerable scale with chromate of lead, chiefly for Oriental markets; and it is the orange chrome—that most heavily weighted with lead—which is most in demand there. The orange chrome colour is obtained by dipping hanks of yarn into solution of lime, and then into acetate of lead. The process is repeated a second time, after which the chromate is formed by dipping in bichromate of soda, and finally boiling in lime-water[39].
In production of yellow chrome colour, the yarn is treated only once in a bath of lead acetate. Other colours made are lemon chrome and (by addition of an indigo bath) chrome green.
The early processes of dyeing rarely give rise to poisoning, but the strong solution of bichromate of soda readily causes characteristic ulceration of the skin—“chrome holes.” Danger arises from dust in the process of heading or “noddling,” as it is sometimes called, of the dried yarn over posts. The hanks of yarn are tugged and shaken by women as a rule, and in the case of orange chrome very considerable quantities of dust are liberated. We have been told that a hank of this kind of yarn does not commend itself to an Oriental buyer unless, when shaken, dust is visible.
The industry was certified as dangerous in 1895, in view of serious illness and death in Glasgow and Manchester, and special rules were made to apply, not only to the heading operations, but also to the winding, reeling, and weaving, of the dyed yarn—processes in which cases of poisoning are very rare.
Detailed inquiry was made in 1906 in eleven factories where yarn was dyed on a considerable scale by means of chromate of lead—in eight mainly for export to India, and in three for the home market. Yarn dyed for the home market gives off less dust when headed, as the material undergoes additional washing in water and in dilute acid; and it is also sometimes passed through a sizing of starch, which fixes the chromate of lead to the yarn more securely.