Pollution and the Heart

Posted by Carla Rothaus

How does climate change exacerbate the adverse effects of air pollution on health?

Pollution is an important yet often overlooked risk factor for cardiovascular disease. Read the NEJM Review Article here.

Clinical Pearls

Q: What are some of the factors that can increase a person’s susceptibility to air pollution?

A: Biologic factors such as advanced age, prior cardiovascular disease, cardiovascular risk factors, pulmonary disease, and immunosuppression can increase a person’s susceptibility to air pollution. Social determinants of health such as income inequality, poverty, food deserts, reduced tree cover, and proximity to highways and industrial facilities — many of them the legacy of structural racism — are associated with increased pollutant exposure and pollution-related cardiovascular disease.

Q: How does climate change exacerbate the adverse effects of air pollution on health?

A: Particulate matter (PM) is the most thoroughly studied component of air pollution and is strongly linked to multiple health effects. PM is categorized into coarse particles (aerodynamic-mass median diameter, <10 μm [PM10]), fine particles (<2.5 μm [PM2.5]), and ultrafine particles (<0.1 μm [PM0.1]). Climate change exacerbates the adverse effects of air pollution on health through multiple cascading mechanisms. High temperatures enhance ground-level ozone formation and also increase the risk of wildfires and dust storms. PM2.5 from wildfire smoke and dust storms increases the risk of cardiovascular disease, with effect estimates that are similar to those for anthropogenic PM2.5. High temperatures also increase the demand for electricity, which in turn increases fossil-fuel combustion and pollution. Temperature extremes and temperature variability are associated with increased mortality from myocardial infarction and stroke.

Morning Report Questions

Q: Has ambient PM2.5 pollution been linked to hypertension?

A: Ambient PM2.5 pollution has been causally linked to multiple risk factors for cardiovascular disease — most notably, hypertension and diabetes. Short-term increases in ambient PM2.5 levels, as well as short-term experimental human exposure to pollution, have been associated with alterations in vascular tone and increased blood pressure. On average, an increase in PM2.5 exposure of 10 μg per cubic millimeter during the preceding day increases systolic and diastolic blood pressure by 0.5 to 1.0 mm Hg, with a wide range of responses and, in some persons, elevations as high as 5 to 10 mm Hg. Long-term exposures are associated with an increased incidence of new-onset hypertension, suggesting that air pollution is an underrecognized, remediable risk factor for the leading cause of death worldwide.

Q: Name some of the toxic metal pollutants that are or may be tied to an increased risk of cardiovascular disease.

A: Lead is a known risk factor for hypertension. Until recently, lead was thought to have few toxic effects in adults at blood levels below 40 μg per deciliter. However, new data from a long-term follow-up study of 14,289 U.S. participants in the Third National Health and Nutrition Examination Survey, who had a mean blood level of 2.71 μg per deciliter, suggest that a relationship between lead and mortality from cardiovascular disease extends down to blood lead levels below 3 μg per deciliter. On the basis of these findings, the number of deaths from cardiovascular disease in the United States could be up to 10 times as high as current estimates. In aqueous environments, metallic and inorganic mercury are converted to highly toxic methylmercury. Methylmercury has long been known to be a potent developmental neurotoxicant. Recent data suggest that it is also associated with a dose-dependent increase in the risks of death from cardiovascular disease and nonfatal myocardial infarction. In the United States, elevated levels of arsenic in groundwater are found in northern New England and the Southwest. Consistent, dose–response associations have been documented between arsenic exposure and coronary heart disease, peripheral arterial disease, and type 2 diabetes.

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