People with type 2 diabetes who were using insulin and lived near roads with heavy traffic had significantly increased concentrations of C-reactive protein (CRP) than those living in lower traffic areas, according to a study published in Environmental Pollution.

The 2-year epidemiological study included 356 Puerto Rican adults with type 2 diabetes living in the greater Boston area. Of these participants, 91 (26%) used insulin, 197 (55%) used oral diabetes medications only and 68 (19%) reported using no diabetes medications.

Approximately 20% of participants lived within 100 meters of one or more roads with more than 20,000 vehicles per day and 20% lived within 100 to 200 meters of roads with more than 20,000 vehicles per day. About 70% of all participants lived in Boston neighborhoods, including South End, Dorchester, Roxbury and Jamaica Plain.

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For the study, researchers measured CRP concentrations at the beginning of the study and 2 years later.

“C-reactive protein concentration increased 75% to 200% over the 2-year period for those 10% of study participants living in the highest traffic areas who were using insulin when compared to those living in lower traffic areas,” study author Christine Rioux, PhD, MS, who is research assistant professor in the department of public health and community medicine at Tufts University School of Medicine, said in a press release.

“In contrast, CRP concentration did not increase for the 22% of people taking metformin and/or other oral diabetes medications who were also living in the high traffic areas.”

Specifically, data demonstrated a significant association between increases in CRP concentration and living within 100 meters of a roadway or near multiple roadways, as compared with further away in participants using insulin in both stratified models (P=.009 and P<.001, respectively) as well as interaction models (P=.071 and P=.002, respectively).

In those using oral diabetes medications only, however, CRP concentrations were markedly lower with the highest traffic density exposure in both stratified (P=.03) and interaction models (P=.024), according to the data.

“This study is important because many people who live near highways may have diabetes and other serious chronic conditions. It’s interesting to see that treatments for diabetes may interact with the risks associated with exposure to air pollution,” Mkaya Mwamburi, MD, PhD, MA, another study author and director of the Center for Global Public Health and associate professor in the department of public health and community medicine at Tufts University School of Medicine, said in the release.

“While this is an intriguing finding, it is not clear why oral diabetes medications, unlike insulin, appear to be protective and it warrants additional research.”


  1. Rioux CL et al. Environ Pollut. 2015;doi:10.1016/j.envpol.2015.03.012.