UC Davis study identifies toxicity of particulate matter from specific sources
19 February 2013
The California Air Resources Board and the Electric Power Research Institute (EPRI) released a report they commissioned by investigators at the University of California, Davis that looks at how to distinguish health effects caused by different types of fine and ultrafine airborne particulate matter (PM) from different sources. This is among the first studies to examine the toxicology of particles according to their source origin. Previous research has linked fine and ultrafine particles to asthma, heart disease and other adverse health effects.
These particles—produced by emissions from many different sources, including traffic, industrial processes, wood-burning fireplaces and gas- and coal-fired power plants—combine in the atmosphere and are affected by sunlight and other meteorological variables. National Ambient Air Quality Standards do not distinguish between these source since they are based solely on mass in given particle size rang. Further, the mixing makes it difficult to determine which compounds in particulate matter may be responsible for specific health effects.
The research was conducted by Dr. Anthony Wexler, director of the Air Quality Research Center at the University of California, Davis. Dr. Wexler used a single particle mass spectrometer and ten particle samplers to capture ambient particles. He then developed novel methods to extract particulate matter from the filter and polyurethane foam substrates, so that (a) as much of the particulate matter was extracted from the substrates and (b) hydroscopic and hydrophobic compounds in the particulate matter were extracted evenly.
Laboratory mice were exposed to the separated particles, and their responses were monitored for signs of toxicity by Dr. Kent Pinkerton, a professor of pediatrics at the UC Davis School of Medicine.
The analysis showed different levels of toxicity for different PM samples, associated with a variety of sources, such as traffic and wood smoke. Most of the toxicity was associated with automobile and cooking sources in both seasons while in the winter toxicity was also associated with secondary compounds. Ultrafine particles were more potent inducers of inflammatory markers and cell death than larger particles.
Broadly, the study found that:
Based on particle size, UF PM was a more potent inducer of inflammatory and cytotoxic response compared to SMF PM on a per mass basis.
For pulmonary inflammation and cytotoxicity, samples containing PM from vehicular sources or metals had the high biological response for summer samples, while PM from vehicular sources, regional processes background, and nighttime inversions had the highest response for winter samples.
In general, the same PM sample produced greater inflammatory and cytotoxic responses in lung samples than in the blood samples under the conditions used in this study.
Analysis of systemic inflammation did not reveal major differences between the collected samples.
Direct toxicity testing of source-oriented PM can increase understanding of the associations between adverse health effects and PM exposure. Different source-oriented and size-resolved samples of sub-micron particulate matter elicited differing levels of response in an array of toxicity measures, supporting the founding hypothesis for this study that different sources and combinations of sources of particulate matter have different levels of toxicity. The unanticipated result was that the sources were toxic in different ways. Ultimately, these advances will contribute to more specific regulations of particulate matter in order to provide greater protection of human health.—Wexler and Pinkerton
EPRI’s air quality research team of Dr. Annette Rohr, Dr. Stephanie Shaw and Dr. Eladio Knipping, helped design the study, as well as reviewed the methods used and results from the ambient measurements and toxicity responses.
Anthony S. Wexler and Kent Pinkerton (2012) Toxicity of Source-Oriented Ambient Submicron Particulate Matter
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