Researchers believe they're now onto an explanation for the process. Arsenic acts as an endocrine disrupter, upsetting the action of hormones by blocking or mimicking them, say Joshua W. Hamilton of Dartmouth College in Hanover, N.H., and his colleagues. Previously identified endocrine disrupters have included many pesticides, industrial chemicals, and pollutants including dioxin. This is the first time that a metal has joined the list, says Hamilton. The researchers suggest that arsenic interferes with the action of glucocorticoids, hormones never known before to be vulnerable to endocrine disruption by pollution.
Glucocorticoids belong to the same family of steroid hormones as estrogen and testosterone.
Glucocorticoids are responsible for turning on many genes that may suppress cancer and regulate blood sugar. To test arsenic's effect on the glucocorticoid system, Hamilton and his coworkers treated rat tumor cells with a solution containing water and a synthetic glucocorticoid, arsenic and the glucocorticoid, or water alone. They then measured the activity of a gene normally switched on by glucocorticoids. The hormone alone activated the gene, but the glucocorticoid-arsenic mix caused no more gene activity than the water solution did. Arsenic blocked the hormone's action, the researchers report in the March Environmental Health Perspectives .