Airborne Particulate Matter and Human Health: A Review

Results of recent research show that particulate matter (PM) composition and size vary widely with both space and time. Despite the variability in PM characteristics, which are believed to influence human health risks, the observed relative health risk estimates per unit PM mass falls within a narrow range of values. Furthermore, no single chemical species appears to dominate health effects; rather the effects appear to be due to a combination of species. Non-PM factors such as socioeconomic status and lifestyle are also believed to affect the health risk, although accounting for these confounding factors is challenging. Airborne PM is also responsible for a number of effects aside from human health, such as alterations in visibility and climate. Because the PM problem is associated with a range of societal issues such as energy production and economic development, making progress on reducing the effects of PM will require integrated strategies that bring together scientists and decision makers from different disciplines to consider tradeoffs holistically.

Notes

Particulate matter refers to small particles consisting of solid or liquid droplets suspended in air. EPA currently regulates particles in two size ranges to help protect public health. These include PM₁₀ and PM_2.5. PM₁₀ refers to particles less than 10 μ m in aerodynamic diameter (about 1/10th the diameter of a human hair), while PM_2.5 (fine particles) refers to particles less than 2.5 μ m in aerodynamic diameter. Because PM₁₀ includes PM_2.5, EPA is in the process of promulgating new standards for coarse particles (PM_c). This refers to particles with aerodynamic diameters between 2.5 μ m and 10 μ m.