volunteers in either of the two districts. Comparison of the results of p,p'DDE and total DDT between the two districts in exposed workers showed no significant difference (p > 0.05), but a highly significant difference (p = 0.001) was found in p,p'DDT levels. This is due to the fact that, according to FUNASA/MT, DDT was applied more intensively in the District of Sinop in more recent years. Figure 2 presents a boxplot of total DDT serum concentrations for the two districts and three working functions on which these comparisons are best observed. In general, total DDT levels for the exposed group in the two districts were higher than those found in the most recent study conducted on sprayers in Sao Jose do Rio Preto, Sao Paulo State, Brazil (Minelli & Ribeiro, 1996a). However, the results of the present study were lower than those reported by Carvalho & Berbet (1987) in sprayers from Sucam (Superintendency of Public Health Campaigns) who also had early but not recent exposure (mean total DDT = 258.28g/L). From the samples analyzed in this study, four individuals in the District of Sinop and one individual in the District of Caceres presented total serum DDT above 500g/L. It is important to emphasize that the occupationally exposed individuals analyzed had used DDT up to 1997, when exposure to this substance was terminated. Consequently, it is likely that more individuals had high concentrations when still exposed to this insecticide. Conclusions Both sprayers and drivers were occupationally exposed to DDT as a consequence of their job activities. Total DDT levels for these two exposed groups did not differ statistically and were higher than those reported by Minelli & Ribeiro (1996b) in a recent study with sprayers, but were lower than those observed by Carvalho (1991) in another study with this same category of workers in Bahia State. Concentrations of the DDT metabolite p,p'DDE generally higher than those of p,p'DDT indicate non-recent exposure. The occupationally exposed group, sprayers and drivers, presented DDT levels significantly higher than those of unexposed workers from the National Health Foundation (Mato Grosso State) in both districts. These high levels are probably due to the fact that exposed workers did not use personal protective equipment, as reported by Souza (1998). Median total serum DDT for the unexposed group was lower than the mean value for the unexposed population, 30g/L, as stated in Act 6,514 (Dec. 22, 1977) of the Brazilian Ministry of Labor. Acknowledgements This study was supported by grants from the Brazilian National Research Council (CNPq) and the Mato Grosso State Research Foundation (FAPEMAT). We gratefully acknowledge the cooperation of the Mato Grosso State Office of the National Health Foundation and their workers, who participated voluntarily in this study. References ALBERT, L., 1981. Residuos de plaguicidas en leche materna y riesgo pra la salud. Boletin de la Oficina Sanitaria Panamericana, 91:15-28. [ Links ]CANTOR, K. P. & BOOZE, C. F., 1991. Mortality among aerial pesticide applicators and flight instructors: A reprint. Archives of Environmental Health, 46:110-116. [ Links ]CARVALHO, W. A., 1991. Fatores de risco relacionados com exposicao ocupacional