A research on animals, conducted by the National Toxicology Program (NTP), has produced strong evidence that a chemical referred to as hexavalent chromium (chromium 6) causes cancer when it is consumed in drinking water.
Hexavalent chromium compounds are often used in electroplating, leather tanning, and textile manufacturing, and have been found in some drinking water sources.
The two-year study showed that the mice had developed malignant tumors upon administration of the chemical.
"Previous studies have shown that hexavalent chromium causes lung cancer in humans in certain occupational settings as a result of inhalation exposure. We now know that it can also cause cancer in animals when administered orally," said Dr. Michelle Hooth, NTP study scientist for the technical report.
During the study, male and female rats had been given four different doses of sodium dichromate dihydrate, an inorganic compound containing hexavalent chromium, in drinking water for two years.
The lowest doses of the chemical administered to the rats were 10 times higher than what humans could consume from the most highly contaminated waters sources identified in California.
Researchers observed increases in the number of benign and malignant tumors in the mice's small intestines, which increased with dose in both males and females.
"We found that hexavalent chromium is absorbed from the gastrointestinal tract. After it is orally administered, it is taken up by the cells in many tissues and organs," said Hooth.
The NTP began work on this compound after gaining inputs from the public and a panel of scientific experts about the study design.
The study findings were announced at the National Institute of Environmental Health Sciences.