Arsenic is an important environmental contaminant, being number ONE in the EPA (Environmental Protection Agency) Superfund list.

The degree of human sufferings caused by arsenic is beyond comprehension in some other parts of the world, such as in Bangladesh and West Bengal, India where an estimated 50 million people are at risk from drinking arsenic contaminated water.

Arsenic's cancer-causing properties may stem from the production of DNA-damaging particles called free radicals.

The finding supports the use of antioxidants such as vitamin C and vitamin E, which mop up free radicals, in cancer prevention.

Researchers studied the effects of arsenic on cells grown in the laboratory.

Cells exposed to arsenic produced about three times as many damaging free radicals as other cells, the authors report, and an antioxidant cut the level of free radicals in the arsenic-exposed cells by half.

Arsenic exposure also doubled the number of cells with genetic mutations, the researchers note. And when an antioxidant blocker was added to the mix, mutated cells increased by 5 to 16 times.

Studies have already shown arsenic to be a human carcinogen, but before this study, the way arsenic caused cancer was unclear.

These results, however, clearly demonstrate that the generation of free radicals within minutes of arsenic exposure can lead to gene mutations and death of the cell, the authors conclude, and that antioxidants can block those effects.

Proceedings of the National Academy of Sciences February 13th 2001;98:1643-1648