Objectives A cross-sectional study was conducted to evaluate the relationship between respiratory health and paraquat exposure. Methods The study population was selected from among workers at 15 Nicaraguan banana plantations which relied on paraquat for the control of weeds. All the workers were interviewed after they received their job assignment for the day of the survey, and all who reported never having applied paraquat and all who reported more than 2 years of cumulative exposure as

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... tors of paraquat with knapsack sprayers were invited for medical evaluation. One hundred and thirty-four exposed workers and 152 unexposed workers were administered a questionnaire interview asking about exposure and respiratory symptoms, and they underwent spirometric testing of forced expiratory volume in 1 s (FEV, , ) and forced vital capacity (FVC). Results In the exposed group 53% reported having experienced a skin rash or burn resulting from paraquat exposure, 25% reported epistaxis, 58% nail damage, and 42% paraquat splashed in the eyes. There was a consistent dose-response relationship between intensity of exposure (as indicated by a history of skin rash or burn) and the prevalence of dyspnea. This relationship was more marked for more severe dyspnea. There was a 3-fold increase in episodic wheezing accompanied by shortness of breath among the more intensely exposed workers. There was no relationship between exposure and FEV, , or FVC. COIICIUS~O~S The high prevalence of respiratory symptoms associated with exposure, in the absence of spirometric abnormalities associated with exposure, could be a result of unmeasured gas exchange abnormalities among workers with long-term exposure to paraquat. Key terms dyspnea, herbicides, pesticides, spirometry, wheezing Paraquat, a nonselective contact herbicide used in approximately 130 countries (I), is widely available to as much as 98% of agricultural workers in third-world countries (2). Paraquat has become well known for its acute oral toxicity. A review published in 1974 reported 232 deaths world-wide between 1964 and 1973 (3). By 1985 almost 2000 deaths were occurring yearly in Japan alone as a result of (primarily intentional) ingestion of paraquat (4). In reports from Asia, the Pacific Islands, and South America, it is the agent of choice for suicide (4-6). In Costa Rica, a country with one of the highest incidences of pesticide poisoning in the world, paraquat causes more deaths than any other pesticide, including 86% of all deaths from occupational pesticide poisoning (7). Almost half of all fatal paraquat poisonings in Costa Rica are not intentional. The case fatality rate after the ingestion of liquid formulations of 20% paraquat is reported to be 60%, and the minimum lethal dose may be no more than 10 ml(8). Paraquat is unusual in that it concentrates in vivo and in vitro in lung tissue in experimental animals.(9) It produces acute pulmonary edema and dense intraalveolar pulmonary fibrosis (perhaps mediated by the formation of superoxide radicals) in patients who do not succumb