Ten-year follow-up of biological monitoring of cadmium-exposed workers.

In this study, 105 workers exposed to cadmium for over 10 years were subjected periodically to environmental monitoring, biological monitoring and medical surveillance. They were divided into subgroups, one in which Cd-B and Cd-U exceeded 10 micrograms/l and 10 micrograms/g creatinine respectively and the other in which they were below these proposed biological exposure indices. Urinary beta 2-microglobulin was used as an indicator of tubular damage. Over the past 3 years 12 workers had raised urinary beta 2-microglobulin values (above 250 micrograms/l). Among workers with Cd-B and Cd-U levels always below the above limits, less than 3% had increased urinary excretion of beta 2-microglobulin, a percentage comparable with that of the reference population. When Cd-B exceeds 10 micrograms/l and Cd-U 10 micrograms/g creatinine on one or more occasions (although the median value still remains below this level), the frequency of tubular damage seems to be considerably higher (8.4 and 7.5% respectively). Thus the Cd-B and Cd-U limits proposed appear to be quite safe if strictly respected. However, median values appear too high to rule out the possibility of an increased incidence of tubular alterations.