Low birth weight and preterm births among infants born to women living near a municipal solid waste landfill site in Montreal, Quebec.

Using data from the Quebec birth registration file, case-control analyses were conducted in order to evaluate the risk of low birth weight (< 2500 g), very low birth weight (< 1500 g), preterm birth (< 37 completed weeks), and small for gestational age (< third percentile) among infants born to women living near a municipal solid waste landfill site in a densely populated area of Montreal, Quebec. Potential exposure to vapors and gases (biogas) was defined in terms of exposure zones around the site. A set of reference areas was selected to be similar to these exposure zones on a number of key sociodemographic factors. Odds ratios (OR) adjusted for variables on the birth file were calculated using logistic regression. Low birth weight was significantly elevated in the exposure zone proximal to the site (adjusted OR = 1.20; 1107 exposed cases; 95% confidence interval: 1.04-1.39). Excess risks were also observed for small for gestational age, but the association was not as strong as for low birth weight (adjusted OR = 1.09; 951 exposed cases; 95% confidence interval: 0.96-1.24). No significant positive associations were observed for very low birth weight or for preterm birth. Because it was not possible to evaluate the effects of all potentially important confounding factors and because detailed environmental exposure assessments were not available, it is not possible to conclude definitively whether low birth weight and small for gestational age are associated with exposure to biogas. Further studies at this and at other landfill sites are warranted in order to confirm or refute these observations and to investigate other possible adverse reproductive outcomes.