Complete outcome information was available for 21,958 private pesticide (farmer) applicators. Farmers in the AHS are predominantly white (98%) males (98%). A total of 14,629 farmers (67%) reported current rhinitis (). Farmers with rhinitis were younger, more educated, and more likely to be never smokers than those without rhinitis. There were no appreciable differences in gender or growing up on a farm between those with and without rhinitis. Individuals with rhinitis were also more likely to report asthma, conjunctivitis, and sinusitis symptoms. Of the AHS farmers who reported current rhinitis, the majority reported 3–6 episodes in the past year (35%) and 15% reported 13 or more episodes in the past year (). A polytomous model was fitted among applicators with completed data on all covariates (n=19,565) to evaluate number of episodes of rhinitis. Age, state of residence, BMI, education, race, currently working on a farm, and years mixing pesticides were significant demographic predictors of rhinitis episodes and were included in subsequent models of farming and pesticide exposures.
The associations of farm-related activities with current rhinitis status were examined in logistic models as well as polytomous models. Two separate models were fit: one to evaluate farm activities (top portion of ) and one to evaluate animal and crop exposures (bottom portion of ). presents the results of the dichotomous logistic models. Handling hay [Odds Ratio (OR) = 1.06, 95% Confidence Interval (95% CI) = 1.02–1.10] and working with swine (OR = 1.05, 95% CI =1.01–1.09) were among several significant predictors of rhinitis. Individuals with rhinitis were also more likely to take part in maintenance activities such as repairing pesticide equipment (OR = 1.16, 95% CI = 1.12–1.20), and painting (OR = 1.15, 95% CI = 1.11–1.19). The highest OR in dichotomous models for farm-related exposures was exposure to other farm animals (OR = 1.25, 95% CI = 1.12–1.41).
In the polytomous models, the significant predictors of rhinitis episodes retained in the final models to evaluate pesticides associated with rhinitis were: butchering animals, handling stored grain, handling stored hay, painting, repairing engines, repairing pesticide equipment, welding, working in swine areas, working with hogs and other farm animals, and growing cabbage, Christmas trees, field corn, sweet corn and hay. Repairing engines, handling stored grain, raising field corn and raising hay were only significant in the polytomous models.
shows the frequency of use of herbicides and insecticides by rhinitis status. The herbicides glyphosate and petroleum oil and the insecticides diazinon, malathion, carbofuran, and permethrin on animals were significantly associated with rhinitis in the polytomous models (global p < 0.05) (). In the dichotomous model, the herbicides glyphosate (OR = 1.09, 95% CI = 1.05–1.13) and petroleum oil (OR = 1.12, 95% CI = 1.05–1.19) were significantly associated with current rhinitis. Six of the 16 insecticides analyzed were also associated with rhinitis in the dichotomous logistic model (data not shown), including dichlorvos, which had the highest OR (OR = 1.15, 95% CI = 1.03–1.28), and other organophosphates including chlorpyrifos (OR = 1.06, 95% CI = 1.01–1.11), diazinon (OR = 1.12, 95% CI = 1.03–1.21), and malathion (OR =1.06, 95% CI = 1.01–1.11). For most pesticides, there was no discernible pattern of association with number of rhinitis episodes, though use of the herbicides glyphosate and petroleum oil and the insecticide permethrin on animals were consistently associated with increased number of episodes (). Six herbicides and insecticides were significantly and positively associated with 13 or more episodes of rhinitis in the past year (data not shown), including petroleum oil (13+ episodesOR = 1.23, 95% CI = 1.11–1.35) and lindane (13+ episodesOR =1.26, 95% CI = 1.03–1.55), which had the highest OR. Use of carbofuran was inversely associated with rhinitis episodes in the polytomous model and, to a lesser extent, inversely associated with any rhinitis in the dichotomous model ().
Herbicide and Insecticide Use in the Past Year by Rhinitis Status Among 21,958 Private Pesticide Applicators in the Agricultural Health Study, Enrolled 1993–7.
Significant Associations Between Rhinitis and Herbicide and Insecticide Use in the Past Year Among 19,565 Private Pesticide Applicators in the Agricultural Health Study, 1993–7.
Adjusted polytomous models were also developed to assess 6 fungicides and two fumigant predictors of rhinitis episodes (data not shown). Only the fungicide captan was significantly associated with increased number of rhinitis episodes (global p < 0.0001). The strongest association between captan use and rhinitis was noted for 7–12 episodes in past year (7–12 episodes OR = 1.32, 95% CI = 1.17–1.49). Fumigant use was not associated with rhinitis episodes (data not shown).
Exposure-response polytomous models were developed to assess whether increased days applying pesticides were associated with increased episodes of rhinitis. Of the herbicides and insecticides associated with rhinitis (), only the herbicide petroleum oil (p = 0.02) and use of permethrin on animals (p = 0.03) had significant, positive exposure-response association with rhinitis episodes (data not shown). Carbofuran had a borderline inverse association with rhinitis (p = 0.06) in exposure-response models. The herbicide metolachlor, which was not statistically associated with rhinitis in ever use models (data not shown), was significant in the exposure-response model (p = 0.03).
Other exploratory subgroup analysis in the herbicide and insecticide models investigated whether reported medical conditions such as asthma or colds attenuated our results. When individuals with asthma (7% of individuals with rhinitis and 3% of controls) were excluded, essentially the same pesticides associations were observed except that the estimate for carbaryl became statistically significant (data not shown). When participants with colds in the past year were excluded from models (n=17,260, 79% of farmers), glyphosate and malathion remained significantly associated with rhinitis. Carbaryl and 2,4-D were significant predictors of rhinitis episodes in these models but not in those with the broader case definition (data not shown). However, our ability to detect associations in these models was reduced due to the high prevalence of colds.