Occupational exposure to cotton dust in cottonseed oil mills

Air samples were collected at breathing height in the hulling-separation department of a modern cottonseed oil mill in Uzbekistan. The average elutriated mass concentration measured by standard cotton dust samplers was 4.6 mg/m3, much lower than the average total dust concentration measured by stationary personal samplers, 12.49 mg/m3, and by personal samplers attached to workers, 14.53 mg/m3. Differences in readings among the vertical elutriators, stationary personal samplers, and roving personal samplers are attributed to the distinct sampling nature and dynamics of these samplers. The data suggest that most of the dust consisted of particles larger than 15 microm, the particle size cutoff of the vertical elutriator. Differences in readings among stationary and roving personal samplers are statistically significant, presumably representing biased sampling by the roving personal samplers of regions characterized by high dust concentration (due to machines malfunctioning), the nonstatic nature of the sampling, and the interaction between the sampler and the worker (the personal cloud). Cotton dust concentrations in the hulling-separation room were nonuniform, peaking in front of and between the huller-separator pairs. The high total mass readings show that workers were exposed to very high levels of nonthoracic airborne dust, which upon inhalation tends to deposit in the extrathoracic airways. The high elutriated mass concentrations suggest that workers were exposed to respirable cotton dust at levels higher than 1 mg/m3 mean concentration, the current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) for cotton dust. Regressions between dust concentrations measured by stationary vertical elutriators and by personal samplers attached to workers serve for estimating the potential occupational exposure to cotton dust of workers in the hulling-separation room.