Risk of adverse birth outcomes in populations living near landfill sites

Abstract

Objective: To investigate the risk of adverse birth outcomes associated with residence near landfill sites in Great Britain. Design: Geographical study of risks of adverse birth outcomes in populations living within 2 km of 9565 landfill sites operational at some time between 1982 and 1997 (from a total of 19 196 sites) compared with those living further away. Setting: Great Britain. Subjects: Over 8.2 million live births, 43 471 stillbirths, and 124 597 congenital anomalies (including terminations). Main outcome measures: All congenital anomalies combined, some specific anomalies, and prevalence of low and very low birth weight (<2500 g and <1500 g). Results: For all anomalies combined, relative risk of residence near landfill sites (all waste types) was 0.92 (99% confidence interval 0.907 to 0.923) unadjusted, and 1.01 (1.005 to 1.023) adjusted for confounders. Adjusted risks were 1.05 (1.01 to 1.10) for neural tube defects, 0.96 (0.93 to 0.99) for cardiovascular defects, 1.07 (1.04 to 1.10) for hypospadias and epispadias (with no excess of surgical correction), 1.08 (1.01 to 1.15) for abdominal wall defects, 1.19 (1.05 to 1.34) for surgical correction of gastroschisis and exomphalos, and 1.05 (1.047 to 1.055) and 1.04 (1.03 to 1.05) for low and very low birth weight respectively. There was no excess risk of stillbirth. Findings for special (hazardous) waste sites did not differ systematically from those for non-special sites. For some specific anomalies, higher risks were found in the period before opening compared with after opening of a landfill site, especially hospital admissions for abdominal wall defects. Conclusions: We found small excess risks of congenital anomalies and low and very low birth weight in populations living near landfill sites. No causal mechanisms are available to explain these findings, and alternative explanations include data artefacts and residual confounding. Further studies are needed to help differentiate between the various possibilities. What is already known on this topic: Various studies have found excess risks of certain congenital anomalies and low birth weight near landfill sites Risks up to two to three times higher have been reported These studies have been difficult to interpret because of problems of exposure classification, small sample size, confounding, and reporting bias What this study adds: Some 80% of the British population lives within 2 km of known landfill sites in Great Britain By including all landfill sites in the country, we avoided the problem of selective reporting, and maximised statistical power Although we found excess risks of congenital anomalies and low birth weight near landfill sites in Great Britain, they were smaller than in some other studies Further work is needed to differentiate potential data artefacts and confounding effects from possible causal associations with landfill