Air Pollution Particles Tied to Atherosclerosis Risk

• Ambient and household air pollution was tied to an increase in carotid intima-media thickness (CIMT), a marker for atherosclerosis, in a study of peri-urban Indian households.

• The airborne particles are likely causing chronic inflammation in the lung tissue, which leads to development of atherosclerosis.

• Atherosclerosis is the narrowing and weakening of blood vessels caused by a buildup of fatty deposits, which is a precursor to cardiovascular disease or stroke.

The following commentary was posted by Reason on FightAging.org:

It is known that exposure to airborne particles, such as smoke from cooking fires, correlates with increased mortality due to cardiovascular disease. Setting aside commentary on wealth and its correlation with exposure to particulate air pollution, the obvious candidate mechanism is an increase in chronic inflammation due to the effects of inhaled particles on lung tissue. Raised inflammation then leads to an accelerated progression of atherosclerosis, the fatty deposits that narrow and weaken blood vessels, ultimately leading to heart failure, stroke, and heart attack. Researchers here provide epidemiological data to support this chronic inflammation hypothesis for the harms caused by particulate air pollution.

The following study was published in International Journal of Epidemiology in October 2019:

Cardiovascular diseases are the leading cause of mortality and morbidity worldwide, including in many low- and middle-income countries (LMICs). India has experienced a rapid epidemiological transition, resulting in notable prevalence of hypertension, diabetes, and obesity. India is also affected by high levels of ambient and household air pollution (HAP), resulting in a setting with high baseline cardiovascular risk and widespread exposure to high levels of air pollution.

Long-term exposure to ambient particulate matter (PM) has been associated with risk of acute myocardial infarction, stroke, and cardiovascular mortality. The most plausible pathway by which PM causes cardiovascular diseases is by promoting inflammation and atherosclerosis. Atherosclerosis is a systemic vascular disease representing the aging process and the cumulative adaptive response to cardiovascular risk factors (e.g. hypertension, diabetes). Carotid intima-media thickness (CIMT) is a non-invasive, surrogate marker of subclinical atherosclerosis, associated with cardiovascular risk factors, events, and mortality. There is evidence for a positive association between long-term ambient PM and CIMT. However, the magnitude of associations has been heterogeneous and studies are limited to high-income countries with low or moderate levels of air pollution. Additionally, the evidence for the association between HAP and CIMT is limited.

To our knowledge, there is no previous evidence about the association between outdoor ambient fine particulate matter (PM) and CIMT from populations in low- and-middle income countries. In this population-based study of 3372 participants, with annual mean ambient PM of 32.7 µg/m3, annual mean PM was associated with carotid intima-media thickness among men. 60% of participants used biomass cooking fuel, which was strongly associated with carotid intima-media thickness in women cooking with an unvented stove. Women had higher values of carotid intima-media thickness compared with men, which might be attributed to high cumulative exposure to household air pollution.