Wayne E. Cascio, MD Director, Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park; Division of Cardiology, Department of Medicine, University of North Carolina School of Medicine at Chapel Hill.
Alison Davis, BA Senior Advisor for Public Affairs, Office of Air Quality Planning and Standards, Office of Air and Radiation, US Environmental Protection Agency, Research Triangle Park, North Carolina.
Susan Lyon Stone, MS Senior Environmental Health Scientist, Office of Air Quality Planning and Standards, Office of Air and Radiation, US Environmental Protection Agency, Research Triangle Park, North Carolina.
The authors have no funding or conflicts of interest to disclose.
Correspondence Wayne E. Cascio, MD, Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, 104 Mason Farm Rd, MD-58A, Chapel Hill, NC 27514 (firstname.lastname@example.org).
The Green Heart Initiative is designed to raise public awareness about the role outdoor air pollution plays in cardiovascular health. Developed by the US Environmental Protection Agency (EPA) to complement the national Million Hearts initiative,1 Green Heart seeks to teach healthcare providers, patients, and their families about the potential for air pollution to adversely affect people with heart or vascular disease and to encourage patients with established disease to use EPA’s Air Quality Index (AQI) to reduce their daily air pollution exposure. This simple-to-use tool converts pollution concentrations to color-coded categories representing different levels of health concern (see Figure 1), with recommendations for actions to reduce exposure. Cardiovascular nurses have a unique opportunity to convey this important information to their patients.
Millions of Americans are at higher risk from air pollution because of heart or vascular disease. These include more than 15 million with coronary heart disease, 5 million with heart failure, and 6.8 million with stroke.2 Despite significant national progress in reducing pollution during the past 4 decades, studies continue to show pollution-related adverse health impacts including premature death, hospitalization for unstable angina, myocardial infarction, heart failure, and stroke among people with established cardiovascular disease.3
The most significant outdoor air pollutants of concern to patients with heart disease are particle pollution (also called particulate matter) and ground-level ozone. Particle pollution can form in the atmosphere from chemical reactions of emissions from power plants, industries, and motor vehicles, or it can be directly generated from fuel combustion and natural sources such as wildfires, windblown dust, and volcanic ash. Ozone is a product of chemical reactions between hydrocarbons and nitrogen dioxide in the atmosphere that depend on sunlight. Particle pollution can be elevated at any time of day, depending on the source and the location, and tends to be higher at different times of year in different regions of the country. By contrast, ozone accumulates during the day and generally dissipates at night. In most areas of the country, ozone levels are elevated primarily during the warm summer months. Although evidence of health effects on the cardiovascular system is stronger for particle pollution than for ozone, both have been shown to increase cardiovascular morbidity and mortality, such as in the clinical populations previously described.4
Identifying the cause of the cardiovascular health effects from these pollutants remains an active area of environmental health research. Inhaled particulate matter can reach the alveoli, where it appears to activate the autonomic nervous system and initiate a local and systemic inflammatory response that includes changes in inflammatory proteins and proteins related to hemostasis and thrombosis. Functionally, this results in endothelial dysfunction, vasoconstriction, and a small increase in blood pressure. Likewise, controlled human exposure studies have recently shown that ozone can affect the autonomic neural input to the heart and cardiac repolarization and can decrease proteins associated with fibrinolysis.5 These mechanisms might explain the increase in myocardial infarction and stroke observed in epidemiology studies that follow short-term exposures to poor air quality in susceptible individuals found in large populations of patients with heart and vascular disease. On the other hand, long-term exposure to particle pollution is associated with arterial stiffness, insulin resistance, lipid changes, and progression of atherosclerosis.3
The primary focus for the prevention of heart and vascular disease should always be evidence-based medical management of hypertension, diabetes, and hyperlipidemia, and encouraging a heart-healthy lifestyle. Checking the AQI is a step patients can easily fold into daily healthy activities. An expert panel of cardiologists and environmental health scientists convened by the American Heart Association recommends educating all patients with cardiovascular disease about the cardiovascular risks from air pollution—including providing information about where to find the AQI and including practical “recommendations to reduce air pollution exposure and limiting activity based on the patient’s level of risk.”3 The AHA-sponsored panel also recommends considering this education for patients at high risk for cardiovascular disease.
The AQI provides pollutant-specific health information and cautionary statements designed to help at-risk groups reduce their exposure to pollution by reducing inhaled pollutant concentrations, ventilation rate, or duration of activities outdoors. Recommendations are simple, including scheduling outdoor activity to times when air quality is better (reduces the concentration of pollution inhaled), taking it easier during outdoor activities (reduces ventilation rate), or spending less time engaged in outdoor activities (reduces duration of exposure) when air quality is poor. All of these measures will reduce the inhaled dose of pollution. The EPA recommends that patients with cardiovascular disease take these steps when the AQI is expected to reach “unhealthy for sensitive groups,” often expressed simply as a “code orange day.”
Current AQI information and AQI forecasts for the next day are broadly available, the result of state and local government commitments to providing this information as a public service. Every hour, air quality monitors in several hundred US cities send data on particle pollution and ozone to AirNow, a federal state local partnership program that provides the information via the airnow.gov Web site. AirNow converts hourly ozone and particle concentrations to an AQI value and color, then maps the colors so users can quickly find current air quality information for their communities (see Figure 2). Air Quality Index forecasts—one of the best tools for planning outdoor activity to reduce pollution exposure—for the next day are also available for more than 400 cities. These forecasts are available from national media outlets, such as USA Today and The Weather Channel; on local television weathercasts; via state and local agency Web sites; and through free tools available on airnow.gov. These include a smartphone app for iPhone and Android phones; an air quality widget that businesses and organizations can put on their Web sites; and AirNow EnviroFlash, an e-mail service that provides air quality forecasts and action day alerts to anyone who signs up.
Although research is needed on the impact of AQI use on cardiovascular outcomes, we can make reasonable inferences from research on patients with asthma that AQI use will make a positive difference. Several studies and surveys assessing behavior modification in response to air quality advisories by patients with asthma and their families demonstrate convincingly that, when environmental health information is available, patients will take action to modify activities and limit or avoid exposure.6 Air quality advisories have also been shown to reduce hospital admissions.7 However, surveys of AQI awareness among adults in the United States show that, although most are aware of the index, few have been informed about the AQI or air quality advisory use by their healthcare providers. When healthcare providers recommend using the AQI to reduce pollution exposure, the number of adults reporting exposure reduction measures increases dramatically.8
Because of the trust patients place in nurses, nurses with an interest in cardiovascular disease prevention have a unique opportunity to convey important and potentially lifesaving information to patients at risk from the effects of outdoor air pollution. Opportunities exist, while in clinic or at the time of hospital discharge, to identify those at higher risk and provide simple-to-understand instructions on how and when to reduce exposure (see text box). Increasing awareness of the need to take action when the AQI rises to the orange level or beyond and advising behavioral response to limit exposure might be enough to avert the triggering of an adverse cardiac event.
Box. Actions to Help Patients With Cardiovascular Disease Reduce Exposure to Air Pollution
* Make checking the AQI a healthy habit and encourage your patients to do the same. Checking the air quality forecast is as easy as checking the weather. Days when air quality reaches “code orange” or beyond are good days for patients with cardiovascular disease to modify their exercise plans. These modifications can be simple, such as reducing the intensity of exercise (walking instead of running, weeding the garden instead of spreading mulch), shortening outdoor exercise, or planning the exercise for a time when air quality is expected to be better. See www.airnow.gov.
* Share Green Heart information. Learn more about research to promote heart health and download a handout for patients. See www.epa.gov/greenheart/.
* Take advantage of AirNow information for healthcare providers (http://bit.ly/airnowproviders). This includes the following:
* Material for use in patient education, including a medical poster and a downloadable fact sheet developed by the EPA, the American Heart Association, and the American College of Cardiology.
* “Ozone and Your Patients’ Health,” an evidence-based training course that offers continuing medical education credits from the American Academy of Family Physicians. The course explains the physiological effects of ozone and outlines steps people can take to reduce their ozone exposure. A similar course on particle pollution, available in late 2013, will offer continuing medical education credit from the Centers for Disease Control and Prevention.
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3. Brook RD, Rajagopalan S, Pope CA III, et al. Particulate matter air pollution and cardiovascular disease: an update to the scientific statement from the American Heart Association. Circulation. 2010; 121 (21): 2331–2378.
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