Chronic low level exposure to the toxic metal cadmium may decrease bone density and increase the risk of fractures, according to a new study.

Lifetime cadmium exposure of men and women in 10 districts in Belgium was estimated by measuring urinary cadmium excretion. The researchers also collected data on bone density, the incidence of fractures and loss of height, following the participants for an average of six and a half years.

Six of the districts investigated bordered on zinc smelters and, not surprisingly, the cadmium excretion of the 225 people in these more polluted districts was found to be 22.8 per cent higher than that of the 281 inhabitants of the other four districts. This had serious implications for their bone health.

For both men and women, external exposure to cadmium was a significant predictor of the incidence of fractures and of height loss.

In women, a two fold increase in cadmium excretion was associated with a 73 per cent increased risk of fractures; in men, the same increase was associated with a 60 per cent greater risk of height loss.

Most studies into cadmium and its effect on bones have been in populations with a high exposure. This is the first to show that low levels of cadmium exposure can also cause bone loss (Lancet, 1999; 353: 1140-44).