Protection against breathing dust: behavior over time in Californian farmers.

The aim of this study was to determine whether Californian farmers changed respiratory protective behaviors over time and the personal characteristics associated with protective behaviors. We surveyed 588 farmers longitudinally from 1993 to 2004. Questions included frequency of protective mask or respirator use in dusty conditions and the percentage of time the farmers drove a tractor with a closed cab. To assess longitudinal associations between protective behaviors and potential covariates, general estimating equation modeling was used with adjustment for subject age, study date, and other covariates. Only 25% of the farmers were "very" concerned about respiratory risks. Over time, any use of a dust mask or respirator decreased significantly, from 54% in 1993 to 37% in 2004 (p-value < or = 0.0001), while consistent use of respiratory protection was maintained by 20% of the cohort. Use of a closed-cab tractor increased slightly from 14% in 1993 to 17% in 2004 (p-value = 0.04). Farmers who were ex-smokers and those concerned about respiratory risk were more likely to consistently use a dust mask or respirator. However, the more acreage or time spent in dust, the less likely farmers were to use protection. Closed-cab tractor use was associated with higher salary, more time driving tractors, and larger acreage farmed. Emission reduction remains a priority. Exposure reduction by closed-cab tractor use was not associated with perception of respiratory risk. As mask or respirator use was most positively associated with respiratory concern, more effort needs to be concentrated on educating farmers about long-term respiratory health risks, and providing more user-friendly personal protective equipment.