In many areas of the world, concentrations of ambient air pollutants exceed levels associated
with increased risk of acute and chronic health problems. While effective policies to reduce emissions at
their sources are clearly preferable, some evidence supports the effectiveness of individual actions to reduce
exposure and health risks. Personal exposure to ambient air pollution can be reduced on high air pollution
days by staying indoors, reducing outdoor air infiltration to indoors, cleaning indoor air with air filters, and
limiting physical exertion, especially outdoors and near air pollution sources. Limited evidence suggests that
the use of respirators may be effective in some circumstances. Awareness of air pollution levels is facilitated
by a growing number of public air quality alert systems. Avoiding exposure to air pollutants is especially
important for susceptible individuals with chronic cardiovascular or pulmonary disease, children, and the
elderly. Research on mechanisms underlying the adverse health effects of air pollution have suggested potential
pharmaceutical or chemopreventive interventions, such as antioxidant or antithrombotic agents, but in the
absence of data on health outcomes, no sound recommendations can be made for primary prevention. Health
care providers and their patients should carefully consider individual circumstances related to outdoor and
indoor air pollutant exposure levels and susceptibility to those air pollutants when deciding on a course of
action to reduce personal exposure and health risks from ambient air pollutants. Careful consideration is
especially warranted when interventions may have unintended negative consequences, such as when efforts
to avoid exposure to air pollutants lead to reduced physical activity or when there is evidence that dietary
supplements, such as antioxidants, have potential adverse health effects. These potential complications of
partially effective personal interventions to reduce exposure or risk highlight the primary importance of
reducing emissions of air pollutants at their sources.