Fetal air pollution exposure linked to low birth weight

Globally, two billion children (90% of all children) are exposed to air pollution above WHO guidelines

image of Low birth weight

New UK research links toxic air to low birth weight that can cause lifelong damage to health, raising fears that millions of babies worldwide are being harmed.

What is already known on this topic

  • Road traffic pollution comprises not only air pollutants such as NO2 and particulate matter, but also noise
  • There is a large body of research demonstrating associations between maternal exposure to ambient air pollution during pregnancy and reduced birth weight, low birth weight (LBW), or small for gestational age (SGA)
  • The relation between road traffic noise and birth weight is unclear, and research examining traffic related air pollutant and noise coexposures together is very limited, so the extent to which observed air pollution associations might be attributable to road traffic noise is poorly understood

What this study adds

  • There is an increased risk of LBW specifically in relation to the air pollution profile of London
  • Exposure to local air pollution from road traffic is associated with increased risk of LBW in London, but there is little evidence for an independent exposure-response effect of traffic related noise on birth weight
  • Reducing exposure to traffic related air pollution could reduce the burden of LBW, SGA, and subsequent morbidity, and ultimately give babies in urban environments a healthier start in life

2017 Study Abstract

To investigate the relation between exposure to both air and noise pollution from road traffic and birth weight outcomes.

Retrospective population based cohort study.

Greater London and surrounding counties up to the M25 motorway (2317 km2), UK, from 2006 to 2010.

540 365 singleton term live births.

Main outcome measures
Term low birth weight (LBW), small for gestational age (SGA) at term, and term birth weight.

Average air pollutant exposures across pregnancy were 41 μg/m3 nitrogen dioxide (NO2), 73 μg/m3 nitrogen oxides (NOx), 14 μg/m3 particulate matter with aerodynamic diameter <2.5 μm (PM2.5), 23 μg/m3 particulate matter with aerodynamic diameter <10 μm (PM10), and 32 μg/m3 ozone (O3). Average daytime (LAeq,16hr) and night-time (Lnight) road traffic A-weighted noise levels were 58 dB and 53 dB respectively. Interquartile range increases in NO2, NOx, PM2.5, PM10, and source specific PM2.5 from traffic exhaust (PM2.5 traffic exhaust) and traffic non-exhaust (brake or tyre wear and resuspension) (PM2.5 traffic non-exhaust) were associated with 2% to 6% increased odds of term LBW, and 1% to 3% increased odds of term SGA. Air pollutant associations were robust to adjustment for road traffic noise. Trends of decreasing birth weight across increasing road traffic noise categories were observed, but were strongly attenuated when adjusted for primary traffic related air pollutants. Only PM2.5 traffic exhaust and PM2.5 were consistently associated with increased risk of term LBW after adjustment for each of the other air pollutants. It was estimated that 3% of term LBW cases in London are directly attributable to residential exposure to PM2.5>13.8 μg/m3during pregnancy.

The findings suggest that air pollution from road traffic in London is adversely affecting fetal growth. The results suggest little evidence for an independent exposure-response effect of traffic related noise on birth weight outcomes.

More Information
  • Impact of London’s road traffic air and noise pollution on birth weight: retrospective population based cohort study, BMJ 2017;359:j5299, 05 December 2017.
  • Air pollution harm to unborn babies may be global health catastrophe, warn doctors, theguardian, 05 December 2017.
  • Featured image Raivenne-lations.

Have your say! Share your views