Low birth weight and exposure to magnetic fields in Sao Paulo/Brazil

摘要

Background: Potential effects of exposure to magnetic fields on human health have worried the population and policy makers worldwide. Magnetic fields (MF) have been associated with several outcomes such as cancer, leukemia, amyotrophic lateral sclerosis, cardiovascular diseases and birth outcomes. Aims: To evaluate the association between low birth weight (LBW) and maternal exposure during pregnancy to MF from transmission lines (TL) in the city of Sao Paulo, Brazil. Methods: Analysis included 5,772 cases of term-LBW (＜2,500 g) and 5,814 controls matched by sex and month of birth. The subjects were selected from the birth registration system and mothers' addresses were geocoded to estimate exposure to MF according the distance to nearest TL. Three regression models were developed: TL of all voltage, TL≤200 kV and ＞200 kV. The final models were evaluated using multiple logistic regression adjusting for birth, maternal and pregnancy characteristics. Results: The analysis did not indicate association between proximity to TL and LBW. In the multivariate analysis mothers residing 100-200 m from TL exhibited OR 1.06 (95% IC 0.85; 1.33) in relation to mothers ≥400 m (reference group). The analysis with TL≤200 kV and ＞200 kV did not alter the results. We did not observe a linear trend of risk. Moreover mothers with less income and low education resided nearest to the TL. Conclusions: We did not find association between maternal residential distance to TL and LBW. The results suggest no relation between occurrence of LBW and MF exposure.