Researchers announced yesterday that there is strong evidence a chemical referred to as hexavalent chromium, or chromium 6, causes cancer in laboratory animals when it is consumed in drinking water. The two-year study conducted by the National Toxicology Program (NTP) shows that animals given hexavalent chromium developed malignant tumors.
“Previous studies have shown that hexavalent chromium causes lung cancer in humans in certain occupational settings as a result of inhalation exposure,” said Michelle Hooth, Ph.D., NTP study scientist for the technical report. “We now know that it can also cause cancer in animals when administered orally.”
The study findings were announced at the
National Institute of Environmental Health Sciences (NIEHS) after the
NTP Board of Scientific Counselors Technical Reports Review Subcommittee completed its independent peer review of the
sodium dichromate dihydrate research report. Sodium dichromate dihydrate is an inorganic compound containing hexavalent chromium that was used in the NTP studies. The NTP is located at the NIEHS, part of the National Institutes of Health.
Hexavalent chromium compounds are often used in electroplating, leather tanning, and textile manufacturing and have been found in some drinking water sources.
Male and female rats and mice were given four different doses of sodium dichromate dihydrate in their drinking water ranging from 14.3 mg/l to 516 mg/l for two years.
The lowest doses given to the animals in the study were ten times higher than what humans could consume from the most highly contaminated water sources identified in California.
The researchers report finding significant increases in tumors at sites where tumors are rarely seen in laboratory animals. Male and female rats had malignant tumors in the oral cavity. The studies conducted in mice found increases in the number of benign and malignant tumors in the small intestine, which increased with dose in both males and females.
"We found that hexavalent chromium is absorbed from the
gastrointestinal tract," said Hooth. "After it is orally administered,
it is taken up by the cells in many tissues and organs."
Hexavalent chromium has been brought to the public’s attention in
many ways, most notably in the movie "Erin Brockovich." Eleven members
from the California Congressional Delegation sent a letter to the NTP
Director requesting the NTP conduct the studies. Nominations for
studying this compound also came from the California Environmental
Protection Agency and the California Department of Health Services. The
NTP began work on this compound after gaining input from the public and
a panel of scientific experts about the study design.
The two-year study is one of several studies that NTP has completed
on this chemical. A series of three-month toxicity tests in rats and
different mouse strains was published in January 2007 in the "NTP
Toxicity Report Series" at http://ntp.niehs.nih.gov/go/29184.
The National Toxicology Program is an interagency program
coordinated by the U.S. Department of Health and Human Services. It is
located at the National Institute of Environmental Health Sciences
(NIEHS) in Research Triangle Park. For more information about the NTP,
visit
http://ntp.niehs.nih.gov.
The National Institute of Environmental Health Sciences (NIEHS), a
component of the National Institutes of Health, supports research to
understand the effects of the environment on human health. For more
information on environmental health topics, visit http://www.niehs.nih.gov/home.htm.
The National Institutes of Health (NIH) - The Nation’s Medical
Research Agency - includes 27 Institutes and Centers and is a component
of the U. S. Department of Health and Human Services. It is the primary
federal agency for conducting and supporting basic, clinical, and
translational medical research, and it investigates the causes,
treatments, and cures for both common and rare diseases. For more
information about NIH and its programs, visit http://www.nih.gov/.
Source: NIEHS Press Release, May 16, 2007
Related Studies
D.J. Paustenbach, B.L. Finley, F.S. Morwat, B.D. Kerger,
Human health
risk and exposure assessment of chromium (VI) in tap water, J. Toxicol.
Environ. Health Part A, 66/17 (2003) 1295-1339.
DOI: 10.1080/15287390306388 Max Costa, Catherine B. Klein,
Toxicity and Carcinogenicity of Chromium Compounds in Humans, Crit. Rev. Toxicol., 36/2 (2006) 155-163.
doi: 10.1080/10408440500534032
Related Information
NIEHS: NTP Study Report: TOX 72 Sodium Dichromate Dihydrate ATSDR: Toxicological Profile for Chromium US EPA: Contaminant Focus: Chromium VI Environmental Working Group: Chrome-Plated Fraud: How PG&E's Scientists-For-Hire Reversed Findings of Cancer Study
David Egilman,
Corporate Corruption of Science—The Case of Chromium(VI),Int. J. Occup. Environ. Health, 12 (2006) 169–176.
DOI: 10.1179/oeh.2006.12.2.169
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