Epigenetic changes seen in elderly men after prolonged air pollution exposure.
Madrigano J, A Baccarelli, MA Mittleman, RO Wright, D Sparrow, PS Vokonas, L Tarantini and J Schwartz. 2011. Prolonged exposure to particulate pollution, genes associated with glutathione pathways, and DNA methylation in a cohort of older men. Environmental Health Perspectives http://dx.doi.org/10.1289/ehp.1002773.
Exposure to two kinds of air pollutants has been linked to declines in a specific type of gene expression known to influence the onset of chronic disease, report researchers in the journal Environmental Health Perspectives. The six-month study of elderly men in Boston found that DNA methylation was reduced after exposures to higher levels of sulfates and black carbon.
This study builds on previous research examining the long-term health effects of air pollution exposure but is one of the first to examine underlying biologic mechanisms that may lead to chronic disease. Little epidemiologic research has examined epigenetic factors and how they may be affected by environmental exposures.
DNA methylation is involved in the control of the way genes are expressed – such as which genes are turned on and off and when. Age, diet, drugs and environmental chemicals can influence this so-called epigenetic alteration. Changes to the process are commonly implicated in cancer and increasingly associated with other common, chronic diseases affecting the heart and lungs.
Researchers examined the effects on DNA methylation of long-term (90 days) exposure to common air pollutants among a large population of elderly men who live in the greater Boston area. The men are part of the 40-year Normative Aging Study and range from 66 – 78 years old.
Using blood samples, researchers measured indicators of DNA methylation and related them to levels of particulate matter (PM2.5), sulfates and black carbon measured in the air during the previous six months. Black carbon is released with car exhaust, and sulfates are associated with burning coal.
The authors found that exposure to black carbon and sulfates during the 90 days were associated with decreases in DNA methylation. These decreases may lead to changes in gene expression and altered risk for diseases that become more common with aging. Based on their results, the authors suggest these air pollutants "should remain a regulatory concern," though further studies are needed to determine if the epigenetic changes contribute to heart or other disease.
Factors that might influence the results – such as seasonal weather, smoking and other personal habits, and medications – were taken into account in the analysis. The results are limited by the broad air measures of the pollutants – instead of personal exposures – and an elderly, all male population.
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