For Release: May 20, 2009
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New Role for an Old Poison: Common Arsenic Exposure Levels Inhibit Flu-fighting Ability against H1N1, DMS Scientists Find
Hanover, N.H.—Low levels of arsenic exposure that commonly occur through drinking contaminated well water severely compromise the immune response to influenza A (H1N1) infection and may lead to increased susceptibility and severity, Dartmouth Medical School scientists have found.
"Hundreds of millions of people across the world are exposed to levels of arsenic above the recommended standard so the impact of arsenic exposure on the potential for a pandemic flu outbreak is of particular concern," said DMS graduate student Courtney Kozul, lead author of the study, reported online in Environmental Health Perspectives.
Respiratory infections with influenza A virus are responsible for 36,000 deaths annually. The recent outbreak of the influenza A H1N1 (swine flu) killed 58 people in Mexico and perhaps up to eight in the United States, according to recent estimates. Many geographic areas with confirmed human cases of avian flu or H1N1 include populations that also have elevated arsenic exposures.
Mice exposed to arsenic, followed by a sublethal H1N1 infection, do not mount an appropriate immune response, the investigators reported. In mice that had ingested 100 ppb (parts per billion) arsenic in their drinking water for five weeks, the immune response to H1N1 infection was initially inadequate and when a response finally kicked in days later, it was "too robust and too late," they determined. Morbidity over the course of the infection was significantly higher for the arsenic-exposed mice than the normal animals.
It appears that arsenic exposure leads to an increased susceptibility and severity of respiratory influenza A infection.
The U.S. Environmental Protection Agency considers 10 ppb arsenic in drinking water "safe," yet concentrations of 100 ppb and higher are common in well water in regions where arsenic is geologically abundant, including Massachusetts, New Hampshire, Maine, Florida, and large parts of the Upper Midwest, the Southwest and the Rocky Mountains, said Dr. Joshua Hamilton, who headed the team study.
"Arsenic is a known immuno-modulatory agent, but our work is the first to show that exposure in drinking water can compromise the response to a subsequent respiratory infection. Based on our model, it appears that arsenic exposure leads to an increased susceptibility and severity of respiratory influenza A infection," Kozul said.
Kozul, a graduate student in the DMS Program in Experimental and Molecular Medicine, was a member of the research group led by Hamilton, formerly a professor of pharmacology and toxicology who is now based at the Marine Biological Laboratory, Woods Hole. Coauthors also include Drs. Richard Enelow, professor of medicine and of microbiology and immunology and chief of pulmonary medicine at DHMC, and Kenneth Ely, of medicine. Kozul is supported by the Dartmouth Superfund basic research program.
The article, Low dose arsenic compromises the immune response to influenza infection in vivo, is available online at no charge.