UC study of Sacramento-area residents links air pollution to increased Type 2 diabetes risk

A team of University of California scientists said they have found a higher risk of Type 2 diabetes in older Californians who live — and exercise outdoors — in communities with poor air quality, according to new research published this month in the Environmental Health Perspectives journal.

The researchers focused their study on Mexican Americans aged 60 and up living in Placer, Sacramento, Solano, Sutter, Yolo and Yuba counties, but researchers said the findings apply to anyone living in regions where air pollution is high. The study participants all had enrolled in the Sacramento Area Latino Study on Aging, or SALSA.

Study co-author Dr. Beate Ritz, a professor of epidemiology and environmental health sciences at the University of California, Los Angeles, has long focused her studies on the impact of ozone, a very common element of air pollution, on human health. Ritz’s UCLA team worked with researchers at UC Berkeley, UC Irvine and UC San Francisco for this latest study on diabetes.

The ozone-related risk “of developing diabetes was 1.5 times higher in the higher-outdoor activity group, and even in the lower activity group, there is an observably higher risk compared with those living in less polluted communities,” said Ritz, who’s also a professor of neurology at UCLA’s David Geffen School of Medicine. “Physical activity is well-known and widely recognized for its health benefits, but the beneficial effects that outdoor physical activities have on human health may have to be weighed against the detrimental impacts of air pollution in areas affected by high pollution levels.”

Physicians often advise diabetics to take up exercise as a way of helping to control their disease, a chronic illness that affects the way the body controls blood sugar.

“Mexican Americans are the fastest growing segment of the U.S. population, have a high prevalence of diabetes and are also among the most highly air pollution-exposed populations in California,” said Mary N. Haan, professor emeritus at UC San Francisco and the principal investigator on the SALSA study, which began in 1998. “Yet, thus far we are not aware of any studies in the U.S. that have explored the relationship between (ozone) exposure and diabetes, or evaluated whether outdoor physical activity modifies associations between (ozone) and diabetes in this population.”

The researchers surveyed the participants and tracked pollution, air quality and traffic levels in the their neighborhoods on a regular basis until 2007. During the period, they found 186 newly developed diabetics among the roughly 1,800 individuals who were surveyed.

Those who developed diabetes were more likely to exercise outdoors and lived in communities that had higher exposure to smog. Outdoor activities included gardening and yard work, swimming, dancing, hunting, camping, boating, walking and outdoor sports.

“Sadly, what this makes clear is that even those Californians who are doing the right thing when it comes to health and wellness are at risk of diabetes because of poor air quality,” said Jason G. Su, a co-author and researcher at UC Berkeley. “These findings are of great relevance for public health protection. Policies and strategies are needed to reduce ozone exposure in communities to guarantee that the health benefits from physical activity are not diminished by pollution exposure, especially in vulnerable populations.”