High blood levels of a man-made chemical used in non-stick coatings were associated with a raised risk of arthritis in a large new study of adults exposed to tainted drinking water.
Researchers found that people with the highest levels of perfluorooctanoate (PFOA) in their blood were up to 40 percent more likely to develop arthritis than people with lower blood levels more typical of the general U.S. population.
Dr. Kim Innes of the School of Medicine at West Virginia University and colleagues used 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 widely used in non-stick and stain-resistant coatings.
Both chemicals are "persistent organic pollutants," meaning they remain in the environment and in the human body for years. Both have also been shown to affect human and animal immune systems and metabolism, including functions such as inflammation that are linked with arthritis.
Arthritis is a degenerative joint disease characterized by pain, stiffness and bone damage that affects some 27 million Americans.
To see whether there was a connection between the chemicals and arthritis risk, Innes' team 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.
A DuPont plant in Washington, West Virginia, released PFOA, PFOS and other chemicals into the air, which eventually contaminated drinking water.
Overall, nearly 8 percent of the study participants were found to have arthritis. People with the top-25 percent highest blood levels of PFOA were about 20 percent more likely to have arthritis than people in the bottom-25 percent.
Once the researchers adjusted for a variety of factors including, age, weight, socioeconomic status, gender and military service, the people with the highest PFOA blood levels were 40 percent more likely to develop arthritis than those with the lowest levels.
Somewhat unexpectedly, the authors also found the opposite to be true for PFOS. People with the highest blood levels of PFOS were 25 percent less likely to be diagnosed with arthritis than people with the lowest levels. 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 the School of Public Health at Emory University in Atlanta, Georgia, and a member of the C8 Science Panel. However, a viable alternate cause for the study findings has not been proposed, Steenland acknowledged.
Innes and her colleagues also note that the 8 percent 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, Steenland said.