Exposure to heavy traffic pollution may lead to an increase in C-reactive protein for those living with type 2 diabetes and using insulin, according to research in Environmental Pollution.

In contrast, adults assigned oral diabetes medications did not experience increases in C-reactive protein (CRP), a marker for inflammation, while exposed to the same amount of heavy traffic, according to researchers.

“According to our findings, [oral diabetes medication] users may be protected over time compared to insulin users,” the researchers wrote. “CRP concentration progressed in those on insulin but remained steady in those on [oral diabetes medications], in relation to proximity or number of major roadways.”

Christine Rioux, PhD, MS, assistant professor in the department of public health and community medicine at Tufts University School of Medicine in Boston, and colleagues analyzed data from 356 Puerto Rican adults (aged 44 to 75 years) with type 2 diabetes living in the Boston area. Within that group, 26% used insulin, 55% used oral diabetes medications and 19% reported using no diabetes medications.

Christine Rioux

Researchers assessed major road proximity and traffic density for each participant’s residential address. Approximately 20% of the group lived within 100 meters of one or more roads with more than 20,000 vehicles per day, and another 20% lived within 100 to 200 meters of roads with the same amount of traffic. Approximately 70% of the participants resided in the greater Boston area. Traffic considerations did not affect the selection criteria for the study.

Researchers measured CRP at the beginning of the study and again 2 years later.

Participants living within 100 meters of a busy roadway showed a 58.2% greater increase in CRP concentration (P =.054) compared with those living more than 200 meters away. Participants living between 100 and 200 meters of a busy roadway showed an 81% greater increase in CRP concentration (P = .03) compared with those living farther from busy roadways. Living near two or more busy roadways was associated with a 190% greater increase in CRP concentration (P = .001) compared with zero roadways.

Participants using oral diabetes medications and living near the highest traffic density showed a 49.3% relative decline in CRP concentration (P = .04).

The study is the first to examine the role that various type 2 diabetes medications may play when combined with a patient’s exposure to traffic pollution, according to researchers. The study builds on the research team’s previous work that suggested oral diabetes medications may provide a protective effect against inflammation for adults with type 2 diabetes.

“People on insulin appear to be even more susceptible to increases in inflammation when living in high traffic area,” Rioux said in a press release. “People can reduce their exposure to traffic pollution by keeping windows closed during the heaviest traffic periods of the day, using air conditioners in the summer months, and avoiding heavy exercise near busy roads, especially during peak traffic times.”

“We would like to examine the relationship between traffic pollution exposure, inflammation and type of diabetes medication in larger cohorts in other parts of the U.S. and world,” Rioux told Endocrine Today.  – by Regina Schaffer