History of Ambient Aerosol Sampling for Environmental Health Assessments

JOHN WATSON, Xiaoliang Wang, Judith Chow, Desert Research Institute

     Abstract Number: 16
     Working Group: History of Aerosol Science

Abstract
Although associations between suspended particulate matter (PM) and adverse effect on human health and ecosystems was known for hundreds of years, practical methods to quantify concentrations and exposures were lacking. Early attempts used passive methods, such as dustfall buckets and deposition plates followed by microscopic analyses, but it was eventually recognized that the larger and more massive particles that settled to the surface were not those that are inhalable and respirable. The availability of electrically-powered air pumps at the beginning of the 20th century permitted continuously pulling air through filters that could then be examined. This also permitted more precise measures of the air sample volumes. These filters were first analyzed for their degree of darkening as “British Smoke” to indicate soot concentrations. Active flow sampling was needed to determine radioactive exposures near the Nevada test site during above ground nuclear tests in the 1950s, and this evolved into the high-volume (hivol) sampler that was adapted to early air quality measurements of Total Suspended Particulate Matter (TSP). Hivols were applied in many urban areas and their mass concentrations were used in epidemiological studies that related TSP to adverse health indicators. This resulted in the first TSP National Ambient Air Quality Standards established by the U.S. EPA in the early 1970s. Further research indicated that smaller and more repeatable size fractions (PM10 and PM2.5) were better health indicators, and samplers were created with size-selective inlets that were less sensitive to meteorological conditions and sampling artifacts that affected the hivol. Recently developed aerosol samplers emphasize portability, smaller footprints, and ability to operate without electrical connections. Small, self-contained filter samplers have also evolved for personal and indoor monitoring.