Air Pollution and Cardiovascular Health - by Eugenia Miller, MD (Non-Academic Version)
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Introduction
Many Americans are aware that air pollution is a problem for persons with underlying lung disease and may be associated with cancer risk. Few are aware of the negative impacts air pollution has on the cardiovascular health of the entire population.
When people are made aware of how they themselves are adversely affected by air pollution, they may become more inspired to make changes in their personal and political behavior that may both benefit their own health and benefit air quality and climate for everyone.
Cardiovascular disease remains the leading cause of death worldwide and has been the leading cause of death for the last century. Identification and treatment of standard risk factors for cardiovascular disease (high blood pressure, smoking, elevated cholesterol, diabetes, inactivity, and unhealthy diet) has led to a 50% reduction in cardiovascular disease since 1950. However, air pollution has been less well recognized as a risk factor for cardiovascular disease although its contribution to the prevalence of cardiovascular disease is substantial.
The Global Burden of Disease Study estimates that air pollution accounts for 9 million deaths worldwide, with 61% related to cardiovascular disease. The Institute for Health Metrics Estimate found air pollution to be the fourth highest ranking risk factor for death worldwide after hypertension, smoking and dietary risks.
Sources of air pollution
Air pollution is a complex mixture that varies with location, time of day and weather. Its components include particulate matter (defined as coarse <10um, fine <2.5um and ultrafine <0.1um) and gases (carbon monoxide, sulfur dioxide, nitric oxides, and volatile and semi volatile organic compounds) released into the atmosphere and ozone formed in the atmosphere. Ambient (outdoor) air pollution comes from natural and human sources. Natural sources include windblown dust and wildfires. Human sources include both stationary and mobile sources. Stationary human sources include coal fired power plants, industrial activity, agricultural dust, oil and gas wells and gas compressors. Mobile human sources include emissions from automobiles, trucks, ships, and airplanes.
Particulate matter is the pollutant most implicated in adverse CV events
Particulate matter (PM) is the pollutant most implicated in poor health and death from cardiovascular disease. Pollution increases the standard risk factors for cardiovascular disease. For instance, relatively small increases in PM 2.5 have been consistently associated with increases in blood pressure in the 2 to 3 days after exposure to a high level of PM. Buildup of plaque in the arteries is associated with increases in PM. Higher levels of PM are associated with increased rates of heart attack, stroke, heart rhythm abnormalities and death from cardiovascular disease.
Government efforts to limit air pollution
In the early twentieth century, several severe urban pollution events clearly associated with major acute increases in hospitalization and death triggered public outrage and led to worldwide legislative activity and regulatory acts limiting the toxic and often deadly effects of air pollution. In the US this included the Clean Air Act of 1963 and the Air Quality Act of 1967.
The Clean Air Act, last amended in 1990, requires the EPA to set National Ambient Air Quality Standards (NAAQS) for 6 principal pollutants including PM2.5 and PM 10. The primary standard for public health protection set by the EPA for PM 2.5 is 12ug/M3 annual mean and 35 ug/M3 24 hour mean. Between 1970 and 2018 aggregate emissions of the 6 common pollutants were reduced by 74%.
Unfortunately for Colorado, the oil and gas industry obtained an exemption from the cumulative impacts provision of the Clean Air Act. Unlike other industries, such as automobile manufacture, aggregated point source pollution from multiple oil and gas production wells is exempt from air quality standards set forth in the act. 17.6 million Americans live within a mile of an oil and gas well.
Despite improvements since passage of the Clean Air Act, as of 2019 132 million people lived in US counties that were not in compliance with national air quality standards. Extensive evidence demonstrates that there is no lower concentration threshold below which exposure can be considered safe. Studies from Europe and Canada show increased mortality associated with PM 2.5 at levels as low as 2 ug/M3. In addition, the risk of illness and death rise sharply at low concentrations and then somewhat level off at higher concentrations.
Disparities in risk of adverse effects from air pollution
Black, Hispanic, indigenous, and low-income persons have a higher exposure to air pollution. They are more likely to live in urban areas near industrial sources of air pollution, near fossil fuel plants, near oil and gas wells and near highways. These communities have a higher prevalence of existing respiratory and cardiovascular conditions making them more vulnerable to adverse effects of air pollution. They also have less access to health care.
Indoor air pollution
Since most adults spend 90% of their time indoors, indoor air pollution is also a concern. Indoor air pollution sources include burning of wood, coal and natural gas, tobacco products, building materials and furnishings, aerosol sprays and volatile cleaning products. In situations when outdoor air is heavily polluted, outdoor air is a source of indoor air pollution. Indoor air pollution is not regulated by the EPA.
Personal Strategies to mitigate air pollution and its adverse effects
Personal strategies to reduce or eliminate exposure to pollutants are particularly applicable to individuals living in or traveling to certain Asian nations such as China and India where ambient pollutants are routinely at very high levels. Personal strategies are particularly applicable to persons at high risk for adverse effects of pollutants such as those with preexisting cardiac and pulmonary disease. Such strategies are particularly important for persons who are exposed to microenvironments with higher levels of pollutants such as urban environments, persons living within 100 meters of a major roadway and persons exposed to wildfires and dust storms.
Limit exposure. The EPA’s Air Quality Index (AQI) converts concentrations of 5 regulated pollutants (CO, NO2, ozone, PM, and SO2) into levels of increasing health risk both for healthy and persons at increased health risk. Recommendations regarding activity are available for each level for healthy persons and persons at increased health risk. Although only a minority of the population follows these recommendations, those who do can reduce their individual exposure. (24) Metropolitan areas with populations above 350,000 are required to report the AQI to the public daily. Many smaller municipalities report the AQI as well. The EPA’s web site, airnow.gov, can be used to determine the AQI updated hourly by zip code and a AQI forecast if available.
N95 masks filter 95% of particles > 0.3 um. Use of the N95 mask may be a wise choice in situations of high pollutant exposure such as with wildfires, dust storms or severe urban pollution events.
Portable Air Cleaners (PACs) are small units designed for cleaning small areas such as a single room. They are mechanical air filters that capture particles on filter material. Use of PACs has been shown to reduce PM 2.5 by as much as 50 to 60% and to improve measures of cardiovascular health including blood pressure, vascular function, and inflammation.
Use HVAC units with HEPA filters. Central heating, ventilation, and air conditioning units (HVAC) equipped with high efficiency particulate arrestance filters (HEPA) can be an effective means for uniform reductions in PM.
Replace gas will all-electric heating and cooking appliances. Cooking and heating with fossil fuels is a major source of indoor air pollution. Transitioning from cooking and heating with coal, oil, natural gas or wood pellets to electric induction cook tops/ranges and heat pumps has the potential to significantly decrease indoor air pollution.
Opportunity for global impact on air pollution
Although actions at the individual and personal level to mitigate adverse effects of air pollution are important, action on the community, state, regional, national, and global level is needed to achieve major reductions in air pollution attributable morbidity and mortality. The American Heart Association (AHA) in a statement issued in 2020 and the AHA along with the World Heart Federation, American College of Cardiology, and the European Society of Cardiology in a statement in 2021 acknowledged the need for further research regarding air pollution’s effects on cardiovascular health and dissemination of that research, advocacy of policy solutions to reduce pollution and education of physicians and patients regarding the cardiovascular effects of air pollution.
Policy advocacy should address reduction in emissions through action on air quality, action on vehicle emissions and promotion of renewable energy generation. Policy interventions should align with policies that benefit community, address health disparities, promote healthy transportation infrastructure, support sustainable food systems, produce reductions in climate forcing agents and reduce frequency and intensity of wildfires. Such policies are intimately interrelated with improvements in each ultimately capable of reducing air pollution’s adverse health effects. Advocacy should address not just government policy but private sector action and public private partnerships.
Causes and solutions for air pollution overlap significantly with causes and solutions for climate change. To achieve success, we need to address both.
Please check out the full version of this articles written for health professionals here.