Agricultural Burning Monitored for Air Pollutants in Imperial County; Exposure Reduction Recommendations Developed

Air pollutants, notably particulate matter (PM) with aerodynamic diameter smaller than 2.5 micrometers (PM2.5), are emitted during agricultural burning. We studied a winter period in Imperial County when predominantly bermuda-grass stubble was burned. At four locations, PM2.5 levels were 23% higher from 4 p.m. on burn days to 8 a.m. the following morning than on days when there were no burns. On days when a burn was within 2 miles of a monitoring site, concentrations were 7 to 8 micrograms per cubic meter higher than on days when burns were farther away; measured levels lowered air quality, which potentially approached moderate. In monitoring five specific burns, we found that the levels of particulate matter with aerodynamic diameter smaller than 10 micrometers (PM10) were highly elevated and potentially hazardous directly downwind of one field. In addition, PM2.5 was composed primarily of carbon, and levels of naphthalene, a respiratory carcinogen, were elevated compared with upwind samples. In interviews, most community leaders, residents and farmers thought health educational efforts were needed. As a result, we developed fact sheets and have made recommendations for further actions to reduce people's exposure to smoke from agricultural burning.