Low levels of arsenic, commonly found in tap water, may increase susceptibility to the H1N1 virus, Dartmouth Medical School researchers reported Wednesday in the journal Environmental Health Perspectives online.
The researchers found that mice given water contaminated with arsenic had "increased susceptibility" to the H1N1 virus, which includes the swine flu strain responsible for the current international outbreak.
The study "would obviously raise some serious concerns" about whether current drinking water standards are adequate, Courtney Kozul, the study's lead author and a third-year Ph.D. candidate at DMS, said.
Exposure to mild levels of arsenic may delay the immune system's response to the H1N1 virus, the study found. While the study's findings apply to swine flu, the study began two years ago and was not inspired by the recent outbreak.
"It was so serendipitous that a lot of press came out with H1N1," Kozul said.
Although swine flu is a sub-type of H1N1, Kozul explained that the strain is not identical to the one used in the study.
In the experiment, the researchers gave mice drinking water contaminated with 100 parts per billion of arsenic, and later exposed the mice to a sublethal strain of H1N1.
The research team found that mice that had consumed the arsenic had a delayed immune response to the infection, which allowed the virus to replicate substantially. Although the mice's immune systems eventually responded to the infection, the mice had difficulty fighting off the virus.
The arsenic exposure also increased their susceptibility to the disease, the study reported, which lead to higher morbidity and "higher pulmonary influenza virus titers" in the week following infection.
The study's findings should be applicable to humans, Kozul said.
"We feel like we've created a model that will allow us to investigate the mechanisms of what we see in human populations," she said.
A large percentage of the human population contracts some form of influenza each year, and between 5 and 15 percent will contract the seasonal flu, Kozul said.
Influenza A, a category of contagions that includes H1N1, is responsible for approximately 36,000 deaths across the globe each year, according to the Centers for Disease Control and Prevention.
The current swine flu outbreak has resulted in 58 deaths in Mexico and 10 in the United States thus far.
In 2006, the Environmental Protection Agency lowered the maximum level of arsenic allowed in drinking water to 10 ppb, but many Americans consume well water, which is not regulated and may contain much higher levels of arsenic, Kozul said.
Kozul said an arsenic concentration of 100 ppb is "not an uncommon level to see," despite EPA regulations, adding that some places in Asia have water with a concentration of 3,000 ppb.
Due to the prevalence of granite in New Hampshire, well water in the state may contain concentrations of arsenic that mirror those used in the study, Kozul said.
Maine, Massachusetts and New Hampshire, as well as large sections of the Rocky Mountains, upper Midwest and Southwest have all been found to have water with arsenic concentrations of 100 ppb or higher, former DMS professor Joshua Hamilton, the last author on the paper, said in a DMS press release. Hamilton was a professor of pharmacology and toxicology at DMS, but recently left to work for the Marine Biological Laboratory in Woods Hole, Mass.
"One of the challenges with arsenic is our ability to detect and measure it in water," Kozul said, explaining that the research team plans to further investigate the immunological effects of arsenic using lower doses of the chemical.
Staff writer Kate Farley contributed to the reporting of this article.
