This paper describes a cross-sectional study that aimed to evaluate the possible association between exposure to trihalomethanes present in public water supplies in the metropolitan region of São Paulo and the occurrence of adverse outcomes in pregnancy. In order to perform the research, 19 municipalities located in the metropolitan area of São Paulo that were supplied by only one water treatment plant, from 1998 to 2002, were selected. The starting point was the verification of trihalomethane levels in public water supplies and the analysis of the prevalence of low birth weight, preterm delivery, congenital anomalies, neural tube and nervous system defects in newborns of the municipalities that were involved in the study, in order to analyze the association between exposure to trihalomethanes and the occurrence of adverse outcomes in pregnancy. The population that was studied consisted of all pregnant women and their newborn children who were living in the selected municipalities during the research period, and had their birth certificates registered in the Information System on Live Births (SINASC). The levels of trihalomethanes were treated as categories. The descriptive analysis was followed by a univariate analysis and then by a multivariate analysis. To express the possible associations of the research outcomes with trihalomethanes, the chi-square test was used followed by the estimation of odds-ratio with a 95% confidence interval. Confounding variables were controlled through the analysis of unconditional multiple logistic regression, following the procedures of Hosmer and Lemeshow (2000). The variables that showed statistical significance (p < 0.2) in univariate analysis were entered into the multivariate mode. The results pointed out an association between possible risk of prematurity and malformation related to trihalomethanes, raising the need for in-depth studies, due to the implications of that fact in public health. The results raise a discussion on the relevant benefits of chlorination in comparison to the reduced risk of adverse outcomes in pregnancy; they also suggest that better monitoring of trihalomethane levels in public water supplies would be advisable.
Trihalomethanes; Low birthweight; Preterm delivery; Congenital anomalies; Neural tube defects; Nervous system defects
