Objectives Paraquat is commonly used worldwide as major herbicide. The objective of this study was to investigate the association among farmers between occupational paraquat exposure and respiratory health effects.

Methods A cross-sectional survey of health effects related to an oil spill was conducted in South Korea from 2008 to 2009. For this analysis, a total of 2882 full-time farmers were selected from the overall sample. Data collection included an interviewer-administered questionnaire and spirometry testing. Logistic regression analysis and linear regression analysis were performed to evaluate the relationship between paraquat exposure and respiratory health outcomes after adjustment for potential confounders.

Results The risks of self-reported physician-diagnosed asthma, chronic obstructive pulmonary disease and allergic rhinitis were non-significantly increased among paraquat-applying farmers compared with non-paraquat-applying farmers. Although the results of a pulmonary function test fell within normal limits, a decline in forced vital capacity and forced expiratory volume in one second was apparent among paraquat-applying farmers compared with non-paraquat-applying farmers. Forced vital capacity (β=−5.20, p<0.001) and forced expiratory volume in one second (β=−1.89, p=0.010) significantly decreased with each unit increase in years of paraquat application. Paraquat-applying farmers showed a significant exposure–response relationship between restrictive ventilatory defects and paraquat application years (p trend=0.015) or lifetime days of application (p trend=0.007).

Conclusions Our findings suggest a possible association between paraquat application and adverse respiratory health effects among farmers.