Traffic-related air pollution is seen to manipulate the levels of high-density lipoprotein (HDL), otherwise known as “good” cholesterol. These are the findings of the American Heart Association (AHA) in their recent study published in Arteriosclerosis, Thrombosis, and Vascular Biology. These lowered levels are evident even after brief and medium-length exposures to air pollution. Researchers find that reduced levels of HDL increases the risk of developing a cardiovascular condition.
It has long been determined that breathing in air pollution raises the risk of cardiovascular disease, but scientists have been unable to explain the exact mechanisms involved. This new study sheds some light to this conundrum, finding that pollution reduces beneficial cholesterol levels, which in turn increases levels of “bad” cholesterol (low density lipoprotein or LDL). Consequently, arteries can harden, leading to heart attacks. The research notes that while the effect is seen in both genders, women are more affected. Dr. Griffith Bell, the lead author, writes on Science Daily that lower levels of HDL “may put individuals at a higher risk for cardiovascular disease down the line.”
These findings are part of an ongoing multi-ethnic study examining different lifestyle factors as predictors of cardiovascular disease. Unlike previous studies that assume individuals living in the same city are exposed to the same level of air pollution, this study uses cohort-focused monitoring campaigns that estimate different levels of air pollution exposure for each participant. It is also the first study to measure correlations between air pollution and HDL particles. Dr. Bell sees that higher exposure to black carbon is significantly associated with lower HDL levels. Worryingly, even only three months of high exposure to these particulates dramatically lowers HDL levels.
Dr. Bell adds a caveat to these results, stating that “we were unable to examine whether [HDL particle numbers] changed over time,” having only measured HDL levels once in his analysis. Keeping multiple records of HDL levels can further prove (or disprove) air pollution’s relationship with cholesterol production, he says. Still, he goes on to conclude that the “study helps strengthen the biological plausibility of the link between traffic-related air pollution and cardiovascular disease. We’re slowly beginning to understand some of the biology of how that link works.”
City living is toxic....literally
This is not the first time that city living, and its associated byproducts, have been linked to poor health. Dwellers not only have to contend with a higher crime rate, researchers are now finding that the environmental stressors found in urban environments can contribute to mental illness and a plethora of other adverse health conditions. Studies are suggesting that growing up in the city doubles the risk of developing psychosis later in life. Additionally, those who live in cities generally report themselves as unhappier, more stressed, and more fatigued than those who live in the countryside.
There is also the additional factor of the prevalence of highly-processed foods in cities, which contribute to the growing epidemic of obesity. Javier Lopez, Director of New York’s Strategic Alliance for Health, says that these fatty foods are a favorite among minority neighborhoods; not only because they taste good, but because they’re cheap. Javier also states that lack of exercise programs in schools lead to more children being overweight or obese. “So then you have to look at opportunities outside of the school day for physical activity. You have more bike lanes, for instance.”
These conditions are less observed among country dwellers.
Recent U.N. statistics forecast that the percentage of Americans living in the country will diminish from 46 percent to 34 percent by 2050.
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