Determinants of disability in illnesses related to agricultural use of organophosphates (OPs) in California.

Organophosphate (OP)-related illness data reported to the Worker Health and Safety Branch (WH&S) at the California Department of Food and Agriculture (CDFA, now Cal-EPA) in the years 1984-1988 were examined. Eight hundred and seventy-eight cases with systemic illness and 199 cases of skin disease or eye injury were identified. Systemic cases were divided into two outcome groups: (1) "severe," disability and/or hospitalization days (n = 361), and (2) "mild," no disability or hospitalization days (n = 372). For the remainder (n = 145) or 16.5% of the cases, illness severity could not be determined. Using multiple logistic regression, independent predictors of "severe" illness were identified among the systemic cases. Workers coming in contact with OP residue on commodities or in the field ("exposed to residue" or ER) (OR = 4.6, 95% CI = 3.03-7.07) and mixer/loaders/applicators (MLA) (OR = 4.1, 95% CI = 2.72-6.07) were at significantly increased risk of severe illness when compared with cases exposed to OP application drift. Cases with a Spanish surname were also at increased risk of severe illness (OR = 1.8, 95% CI = 1.25-2.73). Increased numbers of OPs per exposure were also associated with severe illness (p < 0.001). Among cases who were exposed to only one OP, severe systemic cases were more likely than mild systemic cases to be associated with exposure to diethyl than dimethyl compounds (OR = 1.6, 95% CI = 1.09-2.38). Severe systemic cases were also more likely than severe skin/eye cases to be associated with exposure to OPs with high toxicity (OR = 5.5, 95% CI = 2.42-12.60) and with exposure to diethyl groups (OR = 4.8, 95% CI = 1.90-12.00). These findings suggest that reducing exposure to OP residues, to OPs with diethyl groups, and to multiple OPs, and exposure during mixer/loader/applicator activities would reduce the risk of OP-related illness.