WEDNESDAY, April 1 (HealthDay News) -- People exposed to high levels of traffic pollution have an increased risk of rheumatoid arthritis, a new study suggests.

Researchers analyzed the records of 90,000 women in the Nurses Health Study and used special software to measure the distance between each woman's home and the nearest major roadways. The results showed that women who lived within 50 meters (164 feet) of interstates or primary, multi-lane roads were 31 percent more likely to develop rheumatoid arthritis (RA) than those who lived more than 200 meters (656 feet) from a major roadway. Women who lived within 50 meters of the largest roadways had a 63 percent increased risk.

"Even after accounting for the effects of age, race, sex, socioeconomic status and cigarette smoking, the increased risk for women located near major roads remained substantially higher," Jaime Hart, a research fellow in the Channing Laboratory at Brigham and Women's Hospital in Boston, said in a hospital news release.

The study was published online in the journal Environmental Health Perspectives.

It's believed that genetic factors account for less than 50 percent of rheumatoid arthritis risk, and that environmental factors such as cigarette smoke may increase the risk of developing RA, according to the researchers.

"This, coupled with prior research that suggests air pollution from traffic can cause systemic inflammation, prompted us to study whether there was a direct relationship between air pollution and the risk of RA," Hart said.

Further research is needed to determine the exact effect that specific, measured levels of pollution have on the risk of developing the condition.

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