Fine Particles in Traffic Pollution Tied to Lower ‘Good’ Cholesterol

People who live near sources of heavy traffic exhaust may be at higher risk of heart disease because the fine particles in this type of pollution lower levels of “good” cholesterol needed for healthy blood flow, a US study suggests.

High-density lipoprotein (HDL) cholesterol helps curb the odds of heart disease by purging blood vessels of debris and lowering levels of triglycerides - dangerous fats that can make blood thicker, stickier and more prone to clots.

Researchers studied 6,654 adults and found people exposed to higher levels of fine and ultrafine particles in traffic pollution tended to have lower levels of HDL cholesterol in their blood, Reuters reported.

 “However, this was a fairly small effect - it wasn’t a dramatic lowering of HDL - so I don’t think this is a huge cause for alarm beyond what we already know about the dangers of air pollution,” said lead study author Griffith Bell of the University of Washington School of Public Health in St. Louis.

Previous research has linked pollution from traffic exhaust to an increased risk of lung damage and respiratory diseases as well as cardiovascular disease and stroke.

For the current study, researchers focused on so-called PM 2.5, a mixture of solid particles and liquid droplets smaller than 2.5 micrometers in diameter that can include dust, dirt, soot and smoke. They also looked at what’s known as black carbon, a component of particulate pollution that’s formed by burning various kinds of fuels.

Study participants were 62 years old on average, and half of them were current or former smokers. About 16% of the participants took cholesterol-lowering drugs and roughly 45% had high blood pressure. None had cardiovascular disease at the start of the study period.

Researchers used participants’ home addresses to estimate average exposure to PM 2.5 and black carbon over 12-month, three-month and two-week periods in the year 2000.

Over one year, people exposed to more black carbon had lower levels of HDL cholesterol than participants with little or no exposure to black carbon. The difference was small, but statistically meaningful, researchers reported in the journal Arteriosclerosis, Thrombosis, and Vascular Biology.