Association of Fine Particulate Matter Air Pollution With SIHD

Mar 28, 2019   |  Benjamin Davies Horne, PhD, MPH, FACC; Joseph Muhlestein

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Overview

Ambient outdoor and indoor (or household) air pollution are connected to morbidity and mortality throughout the world through a broad and extensive body of evidence.1-3 Elevated, unhealthy levels of air pollution are routinely found in the geographic regions inhabited by approximately 90% of the world's human population.2,3 This poor air quality may adversely impact the health of billions of people, with 7-8 million people dying each year due to this exposure.2,3 According to the Global Burden of Disease study, indoor and outdoor air pollution are among the top ten risk factors for disease globally,4 and together they are the top environmental health risk factor.2

Fine particulate matter (PM2.5) air pollution consists of particles that are ≤2.5 mcm in diameter and often pass into the respiratory tract and the blood stream after inhalation.1 Airborne particles in this size range tend to be generated by combustion sources such as vehicles, power generation facilities, industrial factories, and wildfires. PM2.5 is primarily responsible for the adverse health effects of air pollution among humans through both chronic and acute exposures; other air pollutants have more minor roles in health risk.2 Ambient air pollution exposures are the most studied in relation to human health effects across the globe; indoor exposure such as to smoke from combustion sources that are used for heating and cooking have been studied primarily in the developing world.2

Long-term PM2.5 exposure may lead to chronic morbidity and early mortality through regular exposure to moderately elevated air pollution levels over a period of many years to decades. These air pollution levels in the United States range from annual mean levels of 12.1-35.3 mcg/m3, as delineated by the US Environmental Protection Agency,5 and ranges are similar in Europe. Elsewhere, such as in India, China, and other southeastern Asian countries,2 annual mean PM2.5 levels in major metropolitan areas routinely exceed 35.4 mcg/m3 and can be as high as annual means of 100 mcg/m3 or more. These air pollution concentrations usually are chronic elevations in the respective geographies and may influence health risk through localized or systemic inflammation, direct irritation of organs or tissues, and other potential mechanisms. Long-term exposure to moderately elevated PM2.5 is associated with the initiation and progression of both cardiac risk factors (e.g., metabolic syndrome components) and atherosclerotic cardiovascular disease.6 Long-term exposure is also associated with death due to cardiovascular diseases.7,8 How long-term exposure to annual means ≥35.4 mcg/m3 impact health are just beginning to be studied.

In contrast, short-term PM2.5 exposures, such as may occur as a result of a weather inversion or a wild fire may lead to acute adverse outcomes in periods of just days to weeks and, in some cases, perhaps hours.9 Such exposures typically are measured as daily 24 hour mean PM2.5 levels and include elevations of PM2.5 over periods of several weeks to up to a month or more. These short-term exposures include PM2.5 concentrations typically exceeding 35.4 mcg/m3 and may reach levels that are classified as unhealthy (35.4-150.4 mcg/m3), very unhealthy (150.5-250.4 mcg/m3), or hazardous or toxic (>250.4 mcg/m3).5 These short-term temporary elevations in PM2.5 levels are associated with acute effects on health via a dose-response relationship, including major adverse cardiovascular events such as unstable angina,9 myocardial infarction (MI),9 and heart failure (HF) exacerbation10; respiratory outcomes such as acute lower respiratory infection11 and exacerbation of chronic obstructive pulmonary disease12; and mortality due to these events. These short-term exposures may elevate risk of poor health outcomes primarily among people with pre-existing conditions such as HF or chronic obstructive pulmonary disease10,12 and may lead to unstable angina and MI primarily among people with existing stable ischemic heart disease.9 With wildfires becoming more common in some areas, such as those experienced recently in California, short-term exposures to elevated PM2.5 levels should continue to be considered when examining the health effects of air pollution.

Guidelines

In addition to the overview provided above, medical guidelines suggest that patients and healthcare providers may take individual actions to reduce or prevent the adverse health effects of air pollution. The most recent medical guideline on the topic in the United States was published in 2010.1 Other guidelines include those from the World Health Organization (WHO) that provide topic-specific information regarding indoor and outdoor air quality, their potential effects on health, and actions that may be taken to reduce risk.13 The WHO guidelines focus primarily on indoor air quality.13 A wealth of other information is available through websites provided by WHO.3

Distilling all this information into a useful and usable format may be a challenge for many clinicians, though. Resources exist for patient and provider education that may aid in delivering a concise message to patients regarding their individual risks related to air pollution exposure and what they can do to ameliorate those risks.14-19 Actions that patients may take to reduce their air pollution-related health risks include two primary approaches:

  1. Reducing or eliminating the exposure to elevated levels of air pollution
  2. Preventing the adverse effects of air pollution on the body

Actions to reduce exposure to air pollution include staying indoors in buildings with filtered air, conducting outdoor activities when air pollution levels are lower (e.g., air pollution from vehicular sources tends to be lower in the early morning), and avoiding areas that are close to roadways and highways where vehicular sources of air pollution are greater. Choices that may reduce the health risk once air pollution exposure has occurred include complying with medication prescriptions, dietary advice, and exercise regimens recommended or provided by the patient's physician or other provider and quitting smoking. People should also not exercise outside during short-term PM2.5 elevation and should consider their options when engaging in outdoor exercise in areas where PM2.5 is chronically elevated. A care process model for clinical use may aid in delivering that message consistently and precisely to outpatients.20 People could also choose to live in areas with less air pollution or could become politically active to influence policy decisions that may result in improved local air quality.

Conclusions

Air pollution is ubiquitous in the world today, and human exposure is largely involuntary. The risks to health are well-documented and result in a large burden of morbidity across the population. The risks of mortality from air pollution are also high. Among patients at some risk of developing ischemic heart disease, long-term exposure to moderately elevated PM2.5 levels may significantly heighten that risk. For patients who have developed ischemic heart disease, air pollution exposure may destabilize otherwise stable coronary plaque and initiate the processes leading to unstable angina and MI, as well as HF of ischemic etiology. Both indoor and outdoor air pollution should be considered when health risks are evaluated. Although the impact of air pollution on human health is substantial, common-sense approaches to amelioration of risk are possible on an individual patient basis. National and world-wide policy approaches to reduce the impact of air pollution on health are beginning to form.3 Continued efforts to reduce air pollution and to educate patients regarding its prevention should aid in reducing risk individually and globally.

References

  1. Brook RD, Rajagopalan S, Pope CA 3rd, et al. Particulate matter air pollution and cardiovascular disease: An update to the scientific statement from the American Heart Association. Circulation 2010;121:2331-78.
  2. World Health Organization. Ambient air pollution: A global assessment of exposure and burden of disease (WHO website). 2016. Available at: https://www.who.int/phe/publications/air-pollution-global-assessment/en/. Accessed March 5, 2019.
  3. World Health Organization. Air pollution (WHO website). 2019. Available at: https://www.who.int/airpollution/en/. Accessed March 5, 2019.
  4. Lim SS, Vos T, Flaxman AD, et al. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet 2012;380:2224-60.
  5. United States Environmental Protection Agency. AQI Breakpoints (EPA website). 2019. Available at: https://aqs.epa.gov/aqsweb/documents/codetables/aqi_breakpoints.html. Accessed March 5, 2019.
  6. Pope CA 3rd, Turner MC, Burnett RT, et al. Relationships between fine particulate air pollution, cardiometabolic disorders, and cardiovascular mortality. Circ Res 2015;116:108-15.
  7. Hoek G, Krishnan RM, Beelen R, et al. Long-term air pollution exposure and cardio- respiratory mortality: a review. Environ Health 2013;12:43.
  8. Beelen R, Raaschou-Nielsen O, Stafoggia M, et al. Effects of long-term exposure to air pollution on natural-cause mortality: an analysis of 22 European cohorts within the multicentre ESCAPE project. Lancet 2014;383:785-95.
  9. Pope CA, Muhlestein JB, Anderson JL, et al. Short-Term Exposure to Fine Particulate Matter Air Pollution Is Preferentially Associated With the Risk of ST-Segment Elevation Acute Coronary Events. J Am Heart Assoc 2015;4:e002506.
  10. Pope CA 3rd, Renlund DG, Kfoury AG, May HT, Horne BD. Relation of heart failure hospitalization to exposure to fine particulate air pollution. Am J Cardiol 2008;102:1230-4.
  11. Horne BD, Joy EA, Hofmann MG, et al. Short-Term Elevation of Fine Particulate Matter Air Pollution and Acute Lower Respiratory Infection. Am J Respir Crit Care Med 2018;198:759-66.
  12. Li MH, Fan LC, Mao B, et al. Short-term Exposure to Ambient Fine Particulate Matter Increases Hospitalizations and Mortality in COPD: A Systematic Review and Meta-analysis. Chest 2016;149:447-58.
  13. World Health Organization. Air Pollution Guidelines (WHO website). 2019. Available at: https://www.who.int/airpollution/guidelines/en/. Accessed March 5, 2019.
  14. Intermountain Healthcare. Outdoor Air Quality and Heart Disease Fact Sheet (Intermountain Healthcare website). 2015. Available at: https://intermountainhealthcare.org/about/transforming-healthcare/sustainability-environmental-health/air-quality-health/. Accessed March 5, 2019.
  15. Intermountain Healthcare. Outdoor Air Quality and Stroke Fact Sheet (Intermountain Healthcare website). 2015. Available at: https://intermountainhealthcare.org/about/transforming-healthcare/sustainability-environmental-health/air-quality-health/. Accessed March 5, 2019.
  16. Intermountain Healthcare. Outdoor Air Quality and Outdoor Exercise or Work Fact Sheet (Intermountain Healthcare website). 2015. Available at: https://intermountainhealthcare.org/about/transforming-healthcare/sustainability-environmental-health/air-quality-health/. Accessed March 5, 2019.
  17. Intermountain Healthcare. Outdoor Air Quality in Summer Fact Sheet (Intermountain Healthcare website). 2015. Available at: https://intermountainhealthcare.org/about/transforming-healthcare/sustainability-environmental-health/air-quality-health/. Accessed March 5, 2019.
  18. Intermountain Healthcare. Outdoor Air Quality and Early Childhood Fact Sheet (Intermountain Healthcare website). 2015. Available at: https://intermountainhealthcare.org/about/transforming-healthcare/sustainability-environmental-health/air-quality-health/. Accessed March 5, 2019.
  19. Intermountain Healthcare. Indoor Air Quality: Radon Fact Sheet (Intermountain Healthcare website). 2015. Available at: https://intermountainhealthcare.org/about/transforming-healthcare/sustainability-environmental-health/air-quality-health/. Accessed March 5, 2019.
  20. Intermountain Healthcare. Outdoor Air Quality and Health CPM (Intermountain Healthcare website). 2015. Available at: https://intermountainphysician.org/clinical/Pages/Care-Process-Models-(CPMs).aspx. Accessed March 5, 2019.

Keywords: Angina, Stable, Air Pollutants, Particulate Matter, Air Pollution, Indoor, Risk Factors, United States Environmental Protection Agency, Metabolic Syndrome, World Health Organization, Preexisting Condition Coverage, Factor V, Smoking Cessation, Air Pollution, Coronary Artery Disease, Angina, Unstable, Myocardial Ischemia, Myocardial Infarction, Environmental Health, Respiratory System, Heart Failure


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