Science Wednesday:OnAir@AAAR: For Coarse Particles, is a Single Monitor enough?

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Payam Pakbin, an EPA grantee and scientist at USC, has recently begun to investigate a controversial topic in air pollution science: coarse particles.

Coarse particles are relatively large, ranging in diameter from 2.5 – 10 micrometers. They come from sources like windblown dust, pollen and fungal spores—which, unlike the combustion sources that produce fine particles, are often extremely difficult to control.

Though there have been preliminary studies on the health effects of coarse particles, there is still a lack of definitive evidence.

EPA scientists are working to bridge this gap in understanding. Until there is a scientific consensus on the health effects of coarse PM, regulations to control it as an isolated pollutant cannot be developed or implemented.

payam pakbin-AAAR

Scientists like Pakbin and his advisor, Costas Sioutas, are beginning to tackle this scientific question and its accompanying challenges. Because coarse PM levels vary significantly over seasons and space, estimating the extent to which people are exposed is very difficult.

By sampling in 10 locations across the Los Angeles Basin once per week for an entire year, Pakbin and Sioutas were able to observe how coarse particle levels changed over space and time. This information is critical to health researchers who need accurate estimates of coarse PM exposure in order to determine the long term effects on human health.

Pakbin found that in the urban locations where pollutants mostly come from the same sources, there was little spatial variability. This suggests that a single, central monitor may be adequate for estimating the amount of coarse PM exposure in a given region. This finding is a boon for health researchers who may now be able to rely on cheap data from central monitors that already exist.

The LA Basin study area makes this work especially significant, Sioutas explained.
“One in 18 Americans lives in the LA Basin,” he said, “this makes our research extremely relevant.”

Pakbin and Sioutas believe that their findings will be relevant to other regions in the U.S. with air quality characteristics similar to the LA Basin.

Data from the study has already been shared with the Multi-Ethnic Study of Atherosclerosis (MESA) Air study, where associations between coarse PM and health will be assessed by expert epidemiologists.

The work was presented Monday at the 2010 AAAR conference and has been accepted for publication in the journal Aerosol Science and Technology.

For more information on Pakbin’s research, visit

About the Author: Becky Fried is a science writer with EPA’s National Center for Environmental Research. Her OnAir posts are a regular “Science Wednesday” feature.