Lead poisoning and lead absorption

by Sir Thomas Morison Legge; Kenneth Weldon Goadby

Dangers and Prevention.

—Little risk attaches to handling the clean sheet lead or drawn lead. Danger is in the early stages. Old oxidized lead piping, lead cisterns, tea lead, old accumulator plates, etc., lie in heaps on the premises. These cannot be handled without generation of dust. When melted and stirred, copious fumes arise, carrying up dust, from which, and from that raised in drossing the surface of the metal, absorption of lead is inevitable unless the melting-pot is fully protected from side-draughts and provided with a hood and duct leading into the main chimney-stack. Doors in front of the hood serve still further to confine the fumes. The skimmings from the pot require to be placed in a receptacle under the hood. Of 109 cases reported in the ten years 1900-1909, operations at the melting-pot accounted for at least 47. We are in agreement with Dixon Mann, who remarks: “Workers in metallic lead do not suffer unless they are frequently in the presence of large quantities of the molten metal, or inhale fine particles of solid lead or its oxide whilst manipulating old metal. Lead, though not usually classed amongst the volatile metals, is capable of volatilization at a high temperature, and in the form of vapour may be taken into the system through the respiratory tract, and also into the stomach. One of the worst cases of chronic lead poisoning I ever saw was that of a man who bought the sheets of lead linings of old tea-chests, and melted them down into pig-lead. He did the work in a small room, without any contrivance for ventilation, and attended to the whole process himself”[10].

Letterpress Printing.

—In this industry account has to be taken of contact with—

1. Molten lead in (a) casting the type in different kinds of machines, including the monotype and linotype; (b) in stereotyping; and (c) in recasting into moulds the line or single type after it has been once used, together with débris from the stereo machine and sweepings from the floor.

2. Metallic lead in handling and dressing the type, and subsequent use of it by the compositor. The type metal itself usually consists of—Lead, 75 per cent.; antimony, 23 per cent.; and tin, 2 per cent.

During the ten years 1900-1909, 200 cases were reported—92 compositors, 71 stereotype and linotype operators, and 37 in subsidiary processes, mainly in the casting-room. Thus, apparently, operations involving contact with molten metal are more likely to cause lead poisoning than actual handling.

Type-Casting.

—In letter founding and in the monotype letter-casting machine the molten metal, heated by a coal fire in the former and Bunsen burner in the latter, at regular intervals fills the matrices at a point where it is cooled by a jet of compressed air, and the formed letter is then mechanically ejected into a receptacle. The temperature of the molten metal has to be carefully regulated, and does not usually rise above 400° to 450° C.—a temperature at which it is extremely doubtful if lead fume can be produced. Sommerfeld[11] states that in 60 cubic metres of air aspirated close to a type-casting machine no trace of lead was found, because vaporization does not take place below 550° C. Such skimming as must occasionally be made of the small surface of molten metal is in a slaggy state, and does not appear to contain much oxide. This is deposited usually in a small box and removed to be remelted once a day. What fume, often of unpleasant odour, is noted is probably due to acroleic acid vapour from the grease and dirt.

The letters having been cast, the type may be rubbed on sandstone or on a file, by which small quantities of metallic dust are given off; set up on setting-boards so that all letters face the same way (work on which female young persons are usually engaged); certain portions of letters undercut so as to make them lie perfectly parallel; dressed, planed, and examined, so as to be of precisely the same height; and finally assorted into founts and packed in the warehouse. In all these operations the fingers necessarily get blackened by contact, and there must be slight dislodgment of metal particles to account for the cases reported.