Study Links Wildfire Smoke Exposure to Reduced Immune System Function

An Air Resources Board-funded study at the California National Primate Research Center showed for the first time that exposure to high levels of fine particle pollution at infancy adversely influences development of the branch of the immune system that combats infectious disease, and adversely affects the development of lung function. The study was the product of unusually high levels of fine particle pollution in Northern California as the result of about 2,000 wildfires in June 2008. Over a period of 10 days levels of PM2.5 (the terminology for inhalable particles smaller than 2.5 microns) at the UC Davis campus were recorded at 50 to 60 micrograms per cubic meter. Some readings reached as high as nearly 80 micrograms per cubic meter, well over the federal standard of 35 micrograms per cubic meter.

Significant findings of the ARB-funded research project, “Persistent Immune Effects of Wildfire PM Exposure During Childhood Development” include:

  • Several parameters of immune system function that help protect the body from bacterial infection were found to be reduced in the animals exposed as infants to the wildfire PM2.5, compared to animals born the following year.
  • This is the first time fine particle pollution has been shown to influence the branch of the immune system that combats infectious disease.
  • Unexpectedly, investigators found a link between reduced immune system function and abnormalities in lung function, particularly in female animals.

The results suggest that infancy is a period during which high PM2.5 exposures may adversely influence development of the innate immune system, and adversely affect development of lung function. Infancy may be associated with increased vulnerability to high levels of air pollution exposure because of the rapid lung and immune system development that occurs during the early months of life. For more information about the research project, go to