Potential for respirable quartz exposure from North Carolina farm soils.

Sandy-loam soils from six active farms in the coastal plains of North Carolina (USA) were analyzed for aerodynamic equivalent diameter and quartz content and compared with results to similar analyses of clay soils of the Piedmont and sandy soils from the sand hills of North Carolina to see whether respirable quartz content varies with soil type. The respirable fraction of sandy loam-soils averaged 0.04 (SD 0.02) versus 0.13 (SD 0.03) for clay soils and 0.04 (SD 0.03) for sandy soils. Quartz content in the 4.25 mu m fraction of sandy-loam soils averaged 15.2 (SD 4.1) % versus 2.2 (SD 0.8) % in clay soils and 29.0 (SD 11.1) % in sandy soils. The mass of respirable quartz in sandy-loam soils averaged 0.7 (SD 0.4)% versus 0.3 (SD 0.1)% in clay soils and 1.0 (SD 0.4) % in sandy soils. These results suggest that, during dusty farm activities, there is a potential for greater respirable quartz exposures associated with work with sandy or sandy-loam soils than from work with clay soils.