Abstract and Introduction
Abstract
Population exposures to ambient outdoor particulate matter (PM) air pollution have been assessed to represent a major burden on global health. Ambient PM is a diverse class of air pollution, with characteristics and health implications that can vary depending on a host of factors, including a particle's original source of emission or formation. The penetration of inhaled particles into the thorax is dependent on their deposition in the upper respiratory tract during inspiration, which varies with particle size, flow rate and tidal volume, and in vivo airway dimensions. All of these factors can be quite variable from person to person, depending on age, transient illness, cigarette smoke and other short-term toxicant exposures that cause transient bronchoconstriction, and occupational history associated with loss of lung function or cumulative injury. The adverse effects of inhaled PM can result from both short-term (acute) and long-term (chronic) exposures to PM, and can range from relatively minor, such as increased symptoms, to very severe effects, including increased risk of premature mortality and decreased life expectancy from long-term exposure. Control of the most toxic PM components can therefore provide major health benefits, and can help guide the selection of the most human health optimal air quality control and climate change mitigation policy measures. As such, a continued improvement in our understanding of the nature and types of PM that are most dangerous to health, and the mechanism(s) of their respective health effects, is an important public health goal.
Introduction
Ambient particulate matter (PM) air pollution represents a major burden on the health of the global population. Indeed, the Global Burden of Disease Report lists outdoor ambient PM as one of the leading causes of global health burden, associating some 3.2 million deaths per year, and 76 million disability-adjusted life years lost per year, from human exposures to ambient PM air pollution worldwide. However, PM is not a single entity, but is instead a diverse class of air pollution, with characteristics that vary depending on a variety of factors, including a particle's original source of emission or formation. As elaborated upon in this article, the risks of human exposures to PM air pollution include a wide array of adverse human health impacts that can vary depending on PM characteristics. These effects result from both short-term (acute) exposures to PM and long-term (chronic) exposures to PM, and can range from relatively minor effects, such as increased symptoms, to very severe effects, including increased risk of premature mortality.