Researchers found that people with the highest levels of perfluorooctanoate (PFOA) in their blood were up to 40% more likely to develop arthritis than people with lower blood levels more typical of the general US population.
Dr Kim Innes of West Virginia University and colleagues studied data on nearly 50,000 adults living in areas of Ohio and West Virginia where a chemical plant had contaminated water supplies with PFOA and perfluorooctane sulfonate (PFOS). Both chemicals are widely used in non-stick and stain-resistant coatings.
Both chemicals are also "persistent organic pollutants", meaning they remain in the environment and in the human body for years. They've been shown to affect human and animal immune systems and metabolism.
Chemicals and arthritis
To see whether there was a connection between the chemicals and arthritis risk, the researchers looked at people being monitored as part of a larger effort known as the C8 Science Panel, established following the settlement of a 2001 class-action lawsuit against DuPont Chemical. It was a DuPont plant in Washington, West Virginia that released PFOA, PFOS and other chemicals into the air, eventually contaminating the drinking water.
Overall, nearly 8% of subjects had arthritis. People with blood levels of PFOA in the top quartile were about 20% more likely to have arthritis than people in the bottom-quartile, according to the online report in the American Journal of Epidemiology.
After adjustment for age, weight, socioeconomic status, gender, military service and other factors, the top quartile was associated with a 40% higher risk than the bottom quartile.
Somewhat unexpectedly, the opposite was true for PFOS. Blood levels in the highest quartile were tied to a 25% lower risk of arthritis. Dr Innes speculated that this may stem from an inflammation-reducing effect of PFOS.
The connection between PFOA and arthritis was strongest in people who were younger and not obese. Since age and obesity are two known risk factors for osteoarthritis, that finding strengthens the apparent link, the researchers note.
Still, the design of the study cannot prove that arthritis is caused by PFOA exposure, or prevented by PFOS exposure, cautioned Dr Kyle Steenland, an epidemiologist at Emory University in Atlanta, Georgia and a member of the C8 Science Panel. However, he acknowledged, no viable alternate cause for the study findings has been proposed.
Dr Innes and her colleagues also note that the 8% rate of arthritis reported by participants in this study is actually lower than the national average for adults – a difference they attribute to underreporting of arthritis by the study participants. More cases would not have likely changed the results, they wrote.
Given the many thousands of people in Ohio and West Virginia who were exposed to the chemicals in their drinking water, it is important to continue to monitor the health of the affected population, Dr Steenland said.
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