National Toxicology Program

National Toxicology Program
https://ntp.niehs.nih.gov/go/767520

NTP Hexavalent Chromium Research: Studies and Results

Front cover TR-546 and TOX-72

After receiving nominations in 2000-2001 to study hexavalent chromium for safety in drinking water, NTP began preliminary studies and designed long-term two-year studies. For a full list of studies, see the NTP testing status page for sodium dichromate dihydrate, a hexavalent chromium compound.

In July 2002, NTP held a meeting to receive input from a panel of scientific experts and the public about data available from preliminary studies on hexavalent chromium and the design of proposed laboratory toxicity and carcinogenicity studies of hexavalent chromium administered in drinking water to rodents. The meeting provided data from preliminary studies, and the design of proposed laboratory toxicity and carcinogenicity studies of hexavalent chromium administered in drinking water to rodents. The expert panel noted that NTP's studies were well designed and provided recommendations on some elements for improvement.

In 2007, NTP published the results of the short-term three-month toxicity studies (TOX-72) on a hexavalent chromium compound. NTP reported that exposure to sodium dichromate dihydrate caused increased tissue growth and ulcers in the stomach of rats. NTP also found, low blood count and lesions of the small intestine in rats and mice. The lesions of the small intestine are potentially symptoms of the initial stage of cancer.

In 2008, NTP published the results of the two-year toxicity and carcinogenicity studies (TR-546) on hexavalent chromium compound. NTP reported that sodium dichromate dihydrate in the drinking water caused oral cancers in rats and small intestine cancer in mice. NTP’s results and conclusions from the three-month and two-year studies were peer reviewed by external experts.

NTP staff have also published results in a number of refereed journals including:

NTP is located at the National Institute of Environmental Health Sciences, part of the National Institutes of Health.