PM2.5 Exposure And Low Birth Weight: A Contribution From A Follow-Up In Mice

Abstract

Epidemiological evidence from different parts of the world show that gestational exposure to air pollution are associated with reduced birth weight. However, results are divergent regarding which pollutant and which trimester of pregnancy presents the highest risks. The present study aimed to investigate experimentally the association between gestational (GS) exposure to the ambient levels of urban air pollution and the risk of low birth weight in mice exposed to real world concentration of PM2.5 and further explore if maternal pre-gestational (MPG) exposures are relevant for this outcome. Experiments were carried out in Sao Paulo city where the source of air pollution is predominantly automotive. Mice were raised and maintained in two inhalation chambers, one receiving ambient air (P) and the other filtered air (C) 24hs/day. Females (n=100) were mated with non-exposed males and divided in 10 groups submitted to differential exposure protocols (Pre-gestational and three gestational periods in order to mimic the trimesters of human gestation). Gestations resulted in 508 live born pups that were weighted after birth. We used a logistic regression to estimate the association between reduced birth weight and MPG and G exposure to PM2.5 which was assessed by daily mean concentration inside chambers. Daily mean PM2.5 concentration during the studies period were 6.4 µm³ in C and 32.8 µm³ in P (p= 0.002). Results show that the maternal exposure increases the risk of low birth weight in 11.17% and the critical gestational stage exposure was GS1, which corresponds to the 1st trimester in humans, increasing the risk in 5.4 %. Our findings agree with results obtained from epidemiological study in humans suggesting that the early gestational exposure to air pollution are critical to increased risk for low birth weight and has shown for the first time that maternal pre-gestational exposure to PM2.5 are more critical for this outcome.