ABSTRACT

The US Environmental Protection Agency is in the process of assessing the need for a National Ambient Air Quality Standard for the coarse fraction of particulate material (PM_CF). Specifically, the PM indicator being considered is particulate matter between 2.5 and 10 μm in aerodynamic equivalent diameter (AED). EPA is primarily relying on the available epidemiological studies that examine the possible health effects of PM_CF to reach a decision about developing a coarse particulate matter standard. These epidemiological studies utilize data from size selective PM samplers to estimate the study population’s exposure to each PM indicator as defined by EPA (PM₁₀, PM_2.5, and PM_CF). Epidemiological studies typically focus on urban populations in order to obtain sufficient sample size and to increase statistical certainty associated with study findings. Because of this focus on the urban environment, there has been a lack of studies that evaluate the effect of coarse particulate matter in rural environments on human health.

There are a number of key differences between the urban and rural environments in the United States that can lead to critical mistakes in applying data from urban studies to the rural environment. These include differences in particle sources, which affect particle size distribution and composition, differences in the concentration of gaseous co-pollutants, and differences in PM sampler performance in the two environments. It is our contention that these differences between the urban and rural environment are significant and that the epidemiological studies cited by EPA rely on data that are not representative of the rural environment. These factors raise serious concerns that the implementation of a PM_CF standard in the rural environment will impose an unfair and unwarranted regulatory burden on the businesses and citizens in the rural areas.