Pregnant women who are exposed to road traffic pollution are more likely to deliver babies with low birth weight, according to a study conducted in London. Weight at the time of birth has an immediate bearing on an infant’s chances of survival — those with low birth weight are more likely to develop a range of complications.
“The findings suggest that air pollution from road traffic in London is adversely affecting foetal growth. The results suggest little evidence for an independent exposure-response effect of traffic related noise on birth weight outcomes,” the researchers concluded in an article published in the British Medical Journal.
The study was conducted by scientists from Imperial College London, King’s College London and University of London. A total of 6,71,509 births were analysed, and the residential addresses of the mothers at the time of birth were mapped to draw correlations with pollution levels.
According to the World Health Organisation (WHO), birth weight less than 2,500 g (5.5 lb) is considered low. Low birth weight is regarded as a significant public health problem globally, and is associated with a range of both short- and long-term consequences. Overall, it is estimated that 15-20 per cent of all births worldwide are affected by low birth weight, representing over 20 million births annually.
“To our knowledge, this is the largest UK study on air pollution and birth weight, and the first UK study and largest study worldwide of birth weight and noise exposure. We observed that long-term exposure during pregnancy to NO2, NOx, PM2.5 overall, and specifically from traffic exhaust and non-exhaust sources, and PM10, were all associated with increased risk of low birth weight at term, across London. There was strong confounding of the relation between road traffic noise and birth weight by primary traffic-related air pollutant coexposure,” said the BMJ article.
A linked editorial advocated not just policy change to tackle polluting vehicles, given the evidence of its effect on unborn babies and young children, but also personal protection, including, but not limited to, masks.
“With compelling evidence of harm from environmental air pollution, pregnant women should consider how to reduce their risk. Air filtering face masks might reduce acute exposure to particulate pollution, but there is no evidence that they reduce chronic exposures. Other strategies include changes to walking routes away from major roads and avoiding outdoor activity when air quality is at its poorest. However, the ubiquity of poor air quality in urban areas like London means that personal behaviour changes are unlikely to result in substantially different long-term exposures. Such lifestyle changes are not realistic for many pregnant women, owing to constraints from employment patterns, residential location and transport options. These constraints are highest in those who are socio-economically disadvantaged, contributing to health inequalities,” it said.