Study Shows Possible Link Between Air Pollution and Higher Cholesterol Levels
Published February 26, 2019
High cholesterol, especially the “bad” type, or low-density lipoprotein (LDL), is a known risk factor for the development of cardiovascular disease which can lead to heart attacks. After entering the bloodstream, the fatty substance can build up along the walls of arteries and cause clots that slow or stop the flow of blood to the heart.
There are many causes of high cholesterol, including genetics, a high-fat diet, and lack of exercise. One other factor researchers are investigating is whether air pollutants like fine particle pollution, also called PM2.5, contribute to high cholesterol levels, especially LDL. Particle pollution is regulated because, at excessive exposures, it can be hazardous to health. Particles can form as the result of emissions from motor vehicles, industry, smoke from wildfires, and other sources of fossil fuel combustion.
Extensive studies over the past two decades have shown that air pollution can impact the heart and can cause heart attacks in people with cardiovascular disease. One decade-long study funded by EPA revealed PM2.5 can accelerate narrowing of the arteries, known as atherosclerosis, which sets up conditions for more clotting and a heart attack. More recently, attention has been given to the potential impact on cholesterol levels in those with heart disease. Researchers at EPA are using new diagnostic technology and air quality modeling to better understand the potential links between air quality and high cholesterol.
Their work is at the cutting edge of cholesterol research in medicine that is focused on the size of cholesterol particles that lead to the formation of fatty, cholesterol plaques in arteries. Studies have shown that smaller particles lend themselves to being more easily absorbed into the arteries where they can contribute to the narrowing of arteries and formation of clots. There is interest in whether these smaller particles are a better indicator for future risk of cardiovascular disease than just the overall levels of cholesterol in the blood.
“While it has been known that there are different sized particles in cholesterol for a while, what is emerging is the nature of these particles and that not all particles are created equally,” says Cavin Ward-Caviness, a computational biologist at EPA who is a co-author in the cholesterol study.
In an EPA study, led by Dr. Laura McGuinn who is now at the Icahn School of Medicine at Mount Sinai, Ward-Caviness and colleagues observed that long-term exposure to PM2.5 increased the number of small, cholesterol particles in the bloodstream of the individuals who underwent cardiac catheterization and therefore may make susceptible populations more prone to cardiovascular disease. The study is the first of its kind to describe these new cholesterol biomarkers that focus on size rather than total cholesterol in the blood. The results are published in the January issue of the journal Environmental International.
The researchers looked at the level and composition of cholesterol from blood samples collected between 2001-2010 by Duke University of 6,587 men and women in North Carolina who underwent a cardiac catheterization to visualize blockages in the arteries. NMR technology, a relatively new method for measuring particle size was used to identify the levels of small, medium or large particles of cholesterol.
The cholesterol levels were then compared to modeled PM2.5 concentrations at the residence of each patient, using satellite imaging and ground-based monitoring data. Patients who lived in an area with higher levels of PM2.5 had an increased level of LDL and in particular, an increased level of small LDL cholesterol particles.
“One of the possible implications is the finding that individuals with higher LDL levels may be more susceptible to the health impacts of air pollution,” says Dr. McGuinn.
The identification of possible links between novel cholesterol biomarkers and air pollution is a major step toward more fully understanding the biological mechanisms set in motion when air pollution impacts the cardiovascular system. The findings might contribute to the identification of intervention strategies for those most at risk of air pollution by clinicians and assist decision makers with protecting the public from environmental risks.