[Biological monitoring of fluoride-exposed workers in Switzerland: development of the internal fluoride burden in the last 10 years].

In Swiss plants a risk of industrial fluorosis exists only for workers in the aluminum industry (electrolysis of Al2 O3, raffination of aluminium). Exposure to fluorides is assessed by ambient monitoring, by health surveillance (early detection of fluorosis) and by biological monitoring (urinary fluoride determinations, pre-shift und post-shift). The results of biological monitoring in the 4 plants in Switzerland are presented (1976/77-1986; 1977 264 workers, 1986 242 workers). During the period from 1976/77-1986 a significant reduction of the urinary fluoride excretion in exposed workers was observed. This reduction was correlated in time with technical measures to reduce external fluoride exposure of workers. Urinary fluoride excretion was within limits of biological exposure indices at the end of the observation period in all plants (on group base). Therefore the risk of industrial fluorosis seems to be eliminated in newly engaged workers and significant lowered in the other workers of the Swiss aluminium industry.