Work carried on in lead-smelting works may be divided into five classes according to risk. Those most exposed to risk are the smelters at lead hearths and reverberatory furnaces, persons employed at the lead and slag runs, flue cleaners, and in crushing and packing flake litharge. Next come those employed at the refining furnaces, those breaking up the roasted ore, blast furnace workers, and those employed at the cupellation process. Attended with danger also is the removal of lead ashes and distillation of the zinc crust. Less dangerous are transport of material, crushing and mixing the ore, refining the work-lead and zinc crust, and work at the Pattinson and Parkes’ processes.
In zinc smelting risk of lead poisoning is great, no matter which process is in question, because of the high proportion of lead in the ore and work-zinc. Swedish blende contains as much as 9 per cent. of lead, and Upper Silesian 2½ per cent. or less. There is risk in calcination, but it is much less than in the distillation process.[5]
There are no quite satisfactory statistics as to the number of cases of lead poisoning in smelting works. Nevertheless, a number of recent publications give valuable data for certain smelting works in Germany, Austria, and Hungary.
From details[6] of lead poisoning at Tarnowitz it would appear that the conditions have materially improved since 1884, the cases having declined from 32·7 per 100 employed in 1884 to 6·2 in 1894 and 1895. The following figures show the proportion affected in the different processes in the years 1901 and 1902:
| Process. | Year. | No. Employed. | Cases. | Per Cent. | |
|---|---|---|---|---|---|
| Reverberatory Furnace | { | 1901 | 131 | 11 | 8·3 |
| { | 1902 | 111 | 4 | 3·6 | |
| Blast Furnace | { | 1901 | 152 | 47 | 30·9 |
| { | 1902 | 187 | 21 | 11·1 | |
| Cupelling Furnace | { | 1901 | 12 | 1 | 8·3 |
| { | 1902 | 12 | 1 | 8·3 | |
| De-silverising | { | 1901 | 32 | 10 | 31·2 |
| { | 1902 | 34 | 7 | 20·6 | |
| Other Employment | { | 1901 | 300 | 7 | 2·3 |
| { | 1902 | 350 | 2 | 0·6 | |
In one smelting works the percentage attack rate was 17·8 in 1901, and 27·1 in 1902. Here the number of workers had increased from 73 in 1901 to 129 in 1902, and the absolute and relative increase probably has relation to the well-known fact that newly employed untrained workers become affected. Similar incidence according to process can be given for the Friedrich’s smelting works during the years 1903-1905:
| Process. | Year. | No. Employed. | Cases. | Per Cent. | |
|---|---|---|---|---|---|
| Reverberatory Furnace | { | 1903 | 86 | 12 | 13·9 |
| { | 1904 | 87 | 8 | 9·2 | |
| { | 1905 | 83 | 11 | 13·3 | |
| Blast Furnace | { | 1903 | 267 | 59 | 22·1 |
| { | 1904 | 232 | 24 | 10·3 | |
| { | 1905 | 247 | 27 | 10·9 | |
| De-silverising | { | 1903 | 56 | 12 | 21·4 |
| { | 1904 | 73 | 4 | 5·5 | |
| { | 1905 | 75 | 4 | 5·3 | |
| Cupelling | { | 1903 | 16 | 4 | 25·0 |
| { | 1904 | 15 | 1 | 6·7 | |
| { | 1905 | 14 | 1 | 7·1 | |
| Other Employment | { | 1903 | 330 | 5 | 1·5 |
| { | 1904 | 309 | 4 | 1·3 | |
| { | 1905 | 347 | 7 | 2·0 | |
Among 3028 cases of lead poisoning treated between 1853 and 1882 in smelting works near Freiberg (Saxony) gastric symptoms were present in 1541, rheumatic pains in 215, cerebral symptoms in 144, paralysis in 58, and lead colic in 426.
The recent reports of the German factory inspectors point still to rather high incidence in many lead smelting works. Thus in the district of Aix la Chapelle in 1909 there were sixty cases involving 1047 sick days, as compared with 58 and 878 in 1908.