Increased exposure to air pollution caused by traffic has been blamed for lowering good cholesterol or the high-density lipoprotein (HDL). This has been blamed for the lower HDL levels of middle-aged and even older adults living in urban areas in the United States. A research published in the Arteriosclerosis, Thrombosis and Vascular Biology journal of the American Heart Association has indicated that people exposed to high-traffic areas with polluted air have increased risks of developing heart failure, atherosclerosis, and other cardiovascular diseases.

The research involved 6,654 adults in the middle and senior ages who lived in areas with high air pollution, as per the American Heart Association. The subjects of the study had lower levels of good cholesterol. Lead author Griffith Bell of Seattle's University of Washington School of Public Health said that more than the cholesterol content of the heart, it is the HDL particles' functionality that provides a healthy effect on the heart. The researchers also found out that exposure to pollution had a greater effect on the good cholesterol level of women subjects.

This is not the first time that increased air pollution has been linked to an increase cardiovascular disease. However, this is the first study that strives to understand the role of pollution in reducing the numbers of the HDL particles. Pollution resulting from traffic produces black carbon which significantly lowered the god cholesterol level. The study also found out that exposure to traffic pollution for more than three months could lead to a lower particle number of the good cholesterol.

The World Health Organization warned as early as 2012 that air pollution was not only an environmental problem but a health problem as well. In the same year, 72 percent of premature deaths related to traffic pollution were caused by strokes and ischaemic heart disease. Some of the deaths were, however, blamed not only on traffic-cased pollution but also by tobacco smoke. The International Agency for Research on Cancer reported that carcinogenic effect of polluted air on humans. It also linked outdoor pollution to an increase in urinary or bladder cancer.

It is sad to note that the burden of having poor health conditions and deaths due to air pollution is carried more by people who live in developing countries with poor income levels. Since polluted air is a major health and environment risk, countries would be better of if it has more policies that would reduce the pollution levels in the air. This would greatly reduce the occurrence of diseases like asthma, lung cancer, and other respiratory diseases.