Lead poisoning and lead absorption

by Sir Thomas Morison Legge; Kenneth Weldon Goadby

In the linotype machine, matrices are brought down from the magazine by touching the corresponding letters on the type indicator until they are arranged so as to form the line; a lever then carries them sideways into position, so as to allow the molten metal to flow into the mould and cast the line. Another lever then raises the matrices, which are carried into the magazine again, the slab of metal with the cast line upon it falling into a receptacle. Here, again, danger of lead fume is hardly in question. As the matrices drop down from the magazine, particles of lead which they have gathered when in contact with the metal are detached, and are visible on every linotype machine at this point. The brass cover of the magazine, if not frequently cleaned, soon becomes coated with fine dust. Although lead fume may not be given off, it is none the less necessary to remove the products of combustion from the heating apparatus, in order to prevent constant vitiation of air and to reduce the temperature in the neighbourhood of the machines. Monotype machines give off much heat. Exhaust ventilation by hoods reaching well over the pots, and branch ducts entering the main duct in connection with a fan tangentially, can alone accomplish this satisfactorily. Hoods and ducts leading merely into a shaft running up the side of the building fail to prevent condensation of the water vapour, which in consequence trickles back. Wherever a well-thought-out system of exhaust ventilation has been installed, reduction in temperature and comfort to the operatives has been secured. Temperatures above 65° F. must incommode a linotype operator.

Fig. 11.—Exhaust Ventilation on the Patent “Pentarcomb” Principle applied to Metal Melting-Pots, etc., in Printing Foundry, as installed by the Zephyr Ventilating Company, Bristol.

P, Patent “pentarcomb” for equalizing exhaust; D, main and branch ducts; U, upcast from fan; F, fan; H, hoods over melting-pots and dross drums; S, stereo metal melting-pots; B, boxes or drums for dross.

The illustration shows exhaust ventilation applied to the melting and stereo pots and dross drums in a letterpress printing foundry. The draught over each pot is equalized at the point where the branch ducts join the main duct by insertion of a patent “pentarcomb” grid, which breaks up the columns of air into numerous smaller channels by specially curved metal plates so as to minimize friction. The ducts are graduated, and the exhaust is provided by a volume fan.

In the foundry the recasting of old used type, etc., is effected, and periodically scraps and sweepings are melted down. These melting-pots should have telescopic hoods so balanced that they can readily be lowered, so as to enclose the bath of molten metal and allow the fume to be drawn by the fan into a duct of such width as to offer no obstacle to escape. A duct too narrow to deal with the great expansion the heated air undergoes is a defect very frequently found. A principal source of danger is the skimming of the melting-pot for sweepings, etc., and deposit of the large amount of dross by the side of the pot. Receptacles for the dross in connection with the exhaust system are imperatively needed.

Exhaust, where practicable, over the often large melting-pot for stereotype casting is desirable, in order to secure a reasonable temperature. Here there is the danger of splashing of molten metal, which is subsequently trodden underfoot.

Compositors’ Work.

—The letters are distributed in the small compartments of the type cases. From attrition dust may lie thick in the compartments, and when at work there is always tendency for small quantities of this dust to be dispersed. While this is the principal source of poisoning, inasmuch as dust containing lead must adhere to the fingers, lead may thus enter the system with food or when smoking. It is quite as easy, also, to believe that lead poisoning may result from solvent action of the blood and tissue fluids on small spicules of lead type which penetrate the skin as to credit the well-substantiated cases of plumbism ensuing on retention of bullets or shot in the body. Compositors sometimes contract the habit of holding type between their teeth.

The old dangerous method of blowing out the dust on the staircase by means of a bellows should before long be entirely supplanted by use of suction bellows or use of printers’ case dust-extractors. In the Clements apparatus the cases are placed on a shelf, which is made to oscillate; air is forced into the compartments from numerous jets, so as to raise the dust, which is removed by suction and collected. The cases are thus cleaned with great saving of time in the composing-room itself, and without contamination of the general atmosphere by dust.