Residential and occupational exposure to pesticides may increase risk for cutaneous melanoma: A case-control study conducted in the south of Brazil

Background: Incidences of primary cutaneous melanoma (CM) have risen over the last few decades, mainly among populations of White European extraction. Some risk factors for melanoma have been clearly established, but other potential risk factors, such as exposure to pesticides, are currently under study. Methods: A case-control study on melanoma was conducted during 2012 and 2013 at three dermatological reference centers in Porto Alegre, Brazil. A total of 191 CM patients and sex- and age-matched control subjects were enrolled in the study. Data on domestic and occupational use of pesticides and the risk factors already established for CM were collected. Multivariate logistic regression was used to study the association between exposure to pesticides and melanoma risk. Results: Subjects exposed to pesticides had twice the level of risk for melanoma (odds ratio [OR] 2.03, 95% confidence interval [CI] 1.03-6.89). When pesticides were used indoors for >10 years, the risk for CM increased further (OR 2.84, 95% CI 1.56-5.33). A high frequency of indoor use of pesticides (four or more times per year) was associated with a 44% increase in the risk for melanoma (OR 1.44, 95% CI 1.11-3.49). The domestic use of pesticides outdoors was not associated with increased risk. Subjects exposed to pesticides at an occupational level were at four times greater risk than subjects who were not occupationally exposed (OR 4.23, 95% CI 1.94-6.31). Conclusions: These findings indicate that the general use of pesticides, particularly indoor domestic use, frequently and over a long period, may be an independent environmental risk factor for CM.