ABSTRACT BACKGROUND: Exposure to air pollutants has several effects on human health, including during pregnancy. OBJECTIVE: To identify whether exposure to benzene and toluene among pregnant women contributes to preterm delivery. DESIGN AND SETTING: Longitudinal study using data on newborns from mothers living in São José dos Campos (SP) in 2016, who had been exposed to benzene and toluene. METHODS: A logistic regression model with three hierarchical levels was constructed using maternal variables relating to newborns, and using benzene and toluene concentrations in quartiles. Occurrences of cesarean births, twins or malformations were excluded. Maternal exposure windows of 5, 10, 15, 30, 60 and 90 days prior to delivery were considered. RESULTS: Out of the 9,562 live births, 3,671 newborns were included and 343 newborns were born at less than 37 weeks of gestation (9.3%). The average birth weight was 3,167.2 g. Exposure to benzene and toluene was significantly associated (P = 0.04) with preterm delivery in the five-day window. There was no association in any of the other exposure windows. CONCLUSIONS: It was possible to identify that maternal exposure to benzene and toluene has an acute effect on preterm delivery.

RESUMO CONTEXTO E OBJETIVO: São vários os efeitos da exposição a poluentes do ar na saúde humana. O objetivo deste estudo foi identificar se a exposição da gestante contribui para o baixo peso ao nascer e qual o sexo mais acometido. TIPO DE ESTUDO: Estudo longitudinal com dados de recém-nascidos de mães residentes em São José do Rio Preto (SP) com exposição a poluentes do ar em 2012 e 2013. MÉTODOS: Foi construído modelo hierarquizado em três níveis com variáveis maternas, do recém-nascido e concentrações de material particulado, ozônio e dióxido de nitrogênio, em quartis. Foram excluídos recém-nascidos prematuros, gemelares ou com malformações e consideradas janelas de exposição de 30, 60 e 90 dias anteriores ao parto. RESULTADOS: Foram incluídos 8.948 recém-nascidos, 4.491 do sexo masculino (50,2%) e 4.457 do feminino (49,8%), e identificados 301 recém-nascidos com baixo peso (3,4%). Os pesos médios foram diferentes entre o sexo masculino (3.281,0 g) e o feminino (3.146,4 g) (P < 0,001). Exposição ao ozônio esteve associada significativamente ao baixo peso ao nascer em ambos os sexos nas janelas de 30 dias (odds ratio, OR = 1,38) e 90 dias (OR = 1,48) e, no sexo feminino, nas janelas de 30 dias (OR = 1,58) e 90 dias (OR =1,59). Exposição ao material particulado teve efeito protetor paradoxal. Não houve associação no sexo masculino. CONCLUSÕES: Houve maior susceptibilidade do sexo feminino aos poluentes a partir da exposição materna. Estudos sobre baixo peso ao nascer segundo exposição materna a poluentes do ar devem separar sexo masculino e feminino.

ABSTRACT CONTEXT AND OBJECTIVE: Several effects of exposure to air pollutants on human health are known. The aim of this study was to identify whether exposure of pregnant women to air pollutants contributes towards low birth weight and which sex is more affected. DESIGN AND SETTING: Longitudinal study using data on newborns from mothers living in São José do Rio Preto (SP) who were exposed to air pollutants in 2012-2013. METHODS: A hierarchical model on three levels was built using maternal and newborn variables and environmental concentrations of particulate matter, ozone and nitrogen dioxide in quartiles. Preterm new-borns, twins and newborns with birth defects were excluded and exposure windows of 30, 60 and 90 days before delivery were considered. RESULTS: 8,948 newborns were included: 4,491 males (50.2%) and 4,457 females (49.8%); 301 newborns presented low birth weight (3.4%). The mean weight differed between males (3281.0 g) and females (3146.4 g) (P < 0.001). Exposure to ozone was significantly associated with low birth weight in both sexes in the 30-day window (odds ratio, OR = 1.38) and 90-day window (OR = 1.48); and among females, in the 30-day window (OR = 1.58) and 90-day window (OR = 1.59). Exposure to particulate matter had a paradoxical protective effect. No association was found among male newborns. CONCLUSIONS: Female newborns showed greater susceptibility to maternal exposure to air pollutants. Studies on low birth weight in relation to maternal exposure to air pollutants should deal with males and females separately.