Exercise. In most developed countries, both air pollution and physical inactivity pose significant health risks to urban populations. The benefits of regular exercise on cardiovascular disease incidence and progression are unequivocal (). Active transportation (e.g., walking or cycling to work) can increase physical activity and reduce the burden of cardiopulmonary disease; however, the health benefits of active transport may be partially compromised if location and potential air pollution exposure are not also considered. Exercise leads to increased PM inhaled dose () and, under some circumstances, to increased PM deposition (). Further, outdoor exercise among children who live in areas with high levels of ozone has been associated with an increased risk of asthma development (). Initial analyses suggest that although walkable areas may have lower levels of ozone and therefore provide multiple health benefits, they may also promote higher exposures to primary traffic-related pollutants (). Furthermore, the design of many communities represents a challenge to promoting physical activity because of proximity to pollutant sources near residential and recreational areas, lack of sidewalks, and long commuting distances. Given this apparent paradox, it is imperative to better understand the interaction of exercise and poor air quality on cardiorespiratory health and function.
In addition to the air quality management strategies focused on emissions reductions and local initiatives to control sources and separate them from residential locations, schools, and health care facilities, the workshop highlighted the value of lowering baseline health risks to reduce pollution-related health impacts. Specifically, the implementation of established primary, secondary, and tertiary interventions (e.g., controlling hypertension, lowering lipids, reducing obesity, promoting physical activity and smoking cessation) for diseases affected by air pollution exposure will serve to reduce the overall burden of disease associated with air pollution exposure. For example, sedentary individuals and those with a diet deficient in antioxidants or with a high salt diet may have an increased risk of developing cardiovascular disease (; ; ) and may therefore also be more susceptible to the effects of air pollution. Through diet modification, exercise, and possibly via antioxidant supplementation, individuals can potentially reduce their personal susceptibility. Several of these approaches are discussed in more detail below.
Mechanisms. To develop an optimal mix of community and individual actions, it is important to understand how long-term, short-term, and very short-term (subdaily, over the course of several hours) exposure to air pollution affects disease mechanisms and particularly disease progression and reversibility. A clearer understanding of this relationship could support the development of improved health messaging around exposure reduction, particularly among susceptible individuals.
Indoor pollutant exposure can also be lowered through the use of air cleaners. Several studies have shown that high-efficiency particulate air (HEPA) filter air cleaners can effectively reduce indoor PM concentrations resulting from both indoor (; ; ; ) and outdoor (; ; ) sources. However, these studies show that air cleaner effectiveness will differ within and between buildings depending on factors such as air exchange, the capacity of the air cleaner, and baseline pollutant levels. Clinical studies investigating the health benefits of air cleaner use have shown mixed results. A limited number of studies suggest that air cleaners can provide some health benefits by reducing exposure to PM that subsequently trigger biological responses associated with air pollutant exposure (). Some associations have been found between the use of HEPA filter devices and a reduction in asthma symptoms among adults and children () and cat allergy–related symptoms among adults () associated with indoor-generated pollution and allergens. Researchers have also found associations between the use of portable air cleaners and decreased symptoms relating to exposure to outdoor generated pollution (). In one study of elderly persons living in close proximity (). In contrast, other studies have found no association between air cleaner use and air pollution–related health effects (; ; ). In a recent review, researchers suggested that investigating the health impacts of air cleaner use over a short-term period (days to weeks), as is the case for most studies, may not allow sufficient time to detect any resulting health benefits (). In addition to air cleaning, the use of air conditioning has been linked to some reduction in health impacts related to air pollution such as a decreased risk of cardiovascular hospitalizations in communities with a higher prevalence of air conditioning (). The role of air conditioning is presumably related to reduced pollutant infiltration due to the decreased air exchange rates during the use of an air conditioner (because windows are closed), but the above ecologic association may also result from regional and/or socioeconomic factors and may not be specifically linked to air conditioner use ().
Given that most exposures, even to ambient pollution, occur indoors and that individuals may choose to remain or exercise indoors on days when outdoor air quality is poor, it is important that information on indoor air quality be included in health protection advice regarding air pollution exposure. Besides environmental tobacco smoke, which leads to well-documented exposures and effects, indoor sources such as cooking can generate high concentrations of PM indoors both in residences and commercial settings (). The health impacts related to exposure to indoor-generated PM not related to smoking have not been thoroughly evaluated. Not surprisingly, following advice to stay indoors can reduce exposure to some pollutants while increasing exposure to others (). There is large variation in indoor:outdoor ratios for pollutant concentrations, both between and within homes. Indoor:outdoor pollutant ratios depend on numerous factors, including the type of pollutant, city, indoor and outdoor sources, building design, use of windows, age of the building, and season. Infiltration efficiency is the fraction of outdoor pollution that penetrates indoors and remains suspended and can be decreased by modifying penetration (the movement of outdoor pollutants to indoors), deposition (the depositing of pollutants on room surfaces), and exfiltration (the movement of pollutants to outdoors). Specifically, decreasing air exchange within a home or building can effectively reduce infiltration. Air conditioning and its coincidence with closing of windows, and the winter season (when windows are also generally closed) all function to reduce infiltration of ozone and PM by reducing air exchange (; ; ).
Background: Associations between air pollution and a multitude of health effects are now well established. Given ubiquitous exposure to some level of air pollution, the attributable health burden can be high, particularly for susceptible populations.
Objectives: An international multidisciplinary workshop was convened to discuss evidence of the effectiveness of actions to reduce health impacts of air pollution at both the community and individual level. The overall aim was to summarize current knowledge regarding air pollution exposure and health impacts leading to public health recommendations.
Discussion: During the workshop, experts reviewed the biological mechanisms of action of air pollution in the initiation and progression of disease, as well as the state of the science regarding community and individual-level interventions. The workshop highlighted strategies to reduce individual baseline risk of conditions associated with increased susceptibility to the effects of air pollution and the need to better understand the role of exposure duration in disease progression, reversal, and adaptation.
The environmental policies and laws do have the intended effect of reducing the emissions of some chemicals emitted by most industries. However, asthma rates increase and so too does community concern. It is likely that the costs of further decreasing emissions from industry, from municipalities, and from all of us will be more expensive. The current context of global warming and rapid climate change drives many air pollution controversies to center stage.
Conclusion: We have identified two promising and largely unexplored strategies to address and mitigate air pollution–related health impacts: reducing individual baseline risk of cardiovascular disease and incorporating air pollution–related health impacts into land-use decisions.
Associations between air pollution and multiple health effects are now well established (; ; ). For key pollutants such as particulate matter (PM) and ozone (), there are no established thresholds of exposure below which population health impacts are absent. Given that everyone is exposed to some level of air pollution, the attributable health burden can be high, particularly for vulnerable subpopulations. Recent evidence that air pollution leads to inflammatory processes that mediate a variety of diseases suggests an expanding range of health impacts related to air pollution exposure. Consequently, the population health burden may be greater than previously believed.
Ports are the latest example of this. On September 5, 2007, the EPA began a research project to test equipment that measures air emissions by equipment used in ports to move goods around docks and on and off cargo ships, trucks, and trains. Most of this equipment burns diesel fuel. The EPA wants to test new equipment that can recapture the energy of hydraulic brakes and thereby use less polluting fuel. They are predicting fuel savings of 1,000 gallons per vehicle per year, with decreased maintenance costs for the fleet. The EPA is working with the Port Authority of New York and New Jersey, Kalmar Industries, Parker Hannifin Corporation, and the Port of Rotterdam. Port authorities are very powerful independent legal entities that can neither tax nor be taxed. They issue bonds. Interest on bonds is not income for federal tax purposes, or for state tax purposes if issued in that state. Wealthy individuals can reduce their tax liability and invest in the country’s infrastructure. Historically, this was done in the West with railroad bonds. Authorities are creatures of state law, but very little is required in the way of public participation or environmental planning. Port authorities are able to resist many environmental requirements, especially if they involve several different states. The environment and ecology of ports are often toxic and unappealing. Ports are places where many ships empty their bilges of waste, often illegally. Some states have passed legislation to prevent cruise ships from dumping their wastes in their ports, such as California. Ports have also been the site of land-based waste-dumping practices. Along tidal areas many communities did this with the idea that the tide would take it away. Wastes from fishing and fish processing can also add to the mix. Ports are also the terminus of many rivers that have collected agricultural runoff, municipal sewage, industrial water discharges, and other types of waste. Ports are among the most environmentally challenging ecosystem reconstruction projects in the United States. In early 2000 many port authorities began to incorporate principles of sustainability into their long-range strategic corporate planning. The cumulative effects of waste, the increasing liability for cleanup costs and its accounting as a contingent liability, and increasing urban environmental activism all undercut achieving anything sustainable in an environmental, business, or social sense. Port authorities now partner with the EPA around air pollution, expressly motivated by a concern about sustainability. New controversies will also emerge from these new policies, such as how clean is clean.