Agricultural dust: What is it, where does it come from, how can it be reduced

Randal Southard, University of California, Department of Land, Air and Water Resources, Davis, CA

Air quality in California’s Central Valley frequently fails to meet state and federal air quality standards for PM-10 (particulate matter with aerodynamic diameter less than 10 micrometers). Agricultural field operations contribute significant amounts of dust and PM-10, especially during harvest and land preparation. Research efforts have focused on characterizing dust sources and sinks, on health effects of dust, and on modifying agricultural practices to reduce dust emissions. Results show that dust mineralogy reflects soil silt and clay mineralogy, allowing some fingerprinting of dust within a few hundred meters of the source. Laboratory experiments show that threshold water contents for dust emission range from 8% for sandy soils to 14% for clayey soils and that loamy and silty soils produce the most PM-10. Inhaled dust can produce lung disease and reduced respiratory function.

Lab experiments with rats showed that dust from grape foliage caused more lung damage than dust from citrus foliage, but the precise causative agent could not be identified. On-farm practices that reduce dust include use of modified almond harvesters, which cut dust production by 80-90%, and conservation tillage practices for annual row crop production, which reduces in-field dust production by 60-80%.

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