Air pollution may be harmful to babies even before they are born, a new study has found.
Researchers in London calculated mothers’ exposure to air pollution and traffic noise in various parts of the city from 2006 to 2010. Then they amassed data on birth weights of 540,365 babies born during those years to women who lived in those areas.
The average pollution exposure was 14 micrograms per cubic meter of PM 2.5, the tiny particles that easily enter the smallest airways in the lungs. The researchers found that for each 5 microgram per cubic meter increase in PM 2.5, the risk of low birth weight increased by 15 percent. Low birth weight is a predictor of an increased risk for diabetes, heart disease and hypertension in later life.
The Environmental Protection Agency standard for PM 2.5 is 12 micrograms per cubic meter averaged over three years, and the World Health Organization suggests 10 as a limit. But the lead author, Mireille B. Toledano, an epidemiologist at Imperial College London, said that there really is no safe level of air pollution.
“For every 10 percent reduction in PM 2.5,” she said, “we can prevent 90 babies being born with low birth weight in London. The current limits are not protecting pregnant women, and they’re not protecting unborn babies.”
Impact of London’s road traffic air and noise pollution on birth weight: retrospective population based cohort study
BMJ 2017; 359 doi: https://doi.org/10.1136/bmj.j5299
- Rachel B Smith, research associate12,
- Daniela Fecht, research fellow3,
- John Gulliver, senior lecturer1,
- Sean D Beevers, senior lecturer4,
- David Dajnak, deputy manager4,
- Marta Blangiardo, senior lecturer1,
- Rebecca E Ghosh, research associate3,
- Anna L Hansell, assistant director23,
- Frank J Kelly, professor24,
- H Ross Anderson, emeritus professor45,
- Mireille B Toledano, reader12
- Correspondence to: M B Toledano
- Accepted 1 November 2017
Objective To investigate the relation between exposure to both air and noise pollution from road traffic and birth weight outcomes.
Design Retrospective population based cohort study.
Setting Greater London and surrounding counties up to the M25 motorway (2317 km2), UK, from 2006 to 2010.
Participants 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.
Results 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/m3ozone (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.
Conclusions 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.
London’s air pollution from PM2.5 is widespread and bad – electric vehicles don’t solve the problem
New research shows just how bad air pollution by PM2.5 is across London. The latest updated London Atmospheric Emissions Inventory, shows that every area in the capital exceeds WHO limits PM2.5, which are particularly bad for health as they penetrate deep into the lungs. The particles have serious health implications – especially for children – with both short- and long-term exposure increasing the likelihood of respiratory and cardiovascular diseases. Young people exposed to these pollutants are more likely to grow up with reduced lung function and develop asthma. However, the main sources of PM2.5 emissions in London are from tyre and brake wear, construction and wood burning. A recent European commission research paper found about half of all particulate matter comes from tyres and brakes. Cutting the number of diesel vehicles helps reduce NO2 levels, but even converting to electric does not solve the problem of the particles from tyres and brakes. Heathrow hopes getting more vehicles on the road network near the airport might reduce air pollution enough to get its runway – but that will not solve its PM2.5 problem.
Particulate emissions from electric cars as bad as conventional – due to more tyre and brake wear
While electric vehicles are a welcome technology, enabling a cut in local air pollution from diesel and petrol cars and vans, (as long as the electricity they use has been sustainably produced) they are not wholly a “silver bullet” solution. A new study shows that much of the particulate air pollution in cities comes from from vehicle tyres and brakes. There is a positive relationship between vehicle weight and these non-exhaust emissions – the heavier the vehicle, the more wear on tyres and brakes, and road surface wear and resuspension of road dust. As electric vehicles tend to be around a quarter heavier, for the equivalent size, than their conventional equivalent internal combustion engine counterparts they produce more of this pollution. Therefore electric vehicle PM emissions – overall – are comparable to those of conventional vehicles. The study found that these non-exhaust sources account for around 90% of PM10 and 85% of PM2.5 from traffic. They conclude: “Future policy should consequently focus on setting standards for non-exhaust emissions and encouraging weight reduction of all vehicles to significantly reduce PM emissions from traffic.” Heathrow is pinning its hopes for cutting air pollution on more use of electric vehicles.
Air pollution from PM2.5 particulates implicated in increasing risk of premature births
Reducing air pollution from the tiny particles, PM2.5 may help to prevent 2.7 million premature births per year worldwide, according to a study published in Environment International. These particles come from sources such as diesel powered vehicles, fires and other sources. Worldwide about 10% of births are classed as preterm, and for these babies there can be significant short and long-term health implications – depending on how early the baby was born. Problems associated with prematurity are the top cause of death among children under 5 years old, and has also been associated with learning and developmental disabilities as well as an increased risk of psychiatric disorders. The number of premature births caused by this air pollution in the UK per year might be as much as 4,500. The worst problems are in south and south east Asia, including India and China. The study considered that about 18% of all pre-term births were associated with the particulate pollution in 2010. Other factors linked to pre-term birth are maternal age (young and old), multiple pregnancy (twins etc.), social and personal/lifestyle factors such as poverty, maternal education, prenatal care, physical activity, diet, and alcohol and drug consumption.