London air pollution causing lower birth weights in babies, major study finds

Air pollution in London is linked to low birth weight in babies
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Eleanor Rose6 December 2017

London's polluted air is leading to lower birth weights in babies, which in turn is linked to infant mortality and diseases later in life, a major study has found.

The study by scientists from Imperial College London, Kings College and St George's, published in the British Medical Journal, found that London mothers exposed to higher levels of damaging PM2.5 particles caused by traffic are up to six per cent more likely to give birth to a baby with low birth weight.

PM2.5s are smaller particulates that can bypass the nose and throat and penetrate deep into the lungs, causing premature mortality, aggravation of the respiratory system and cardiovascular diseases.

Dr Rachel Smith, research associate at Imperial, said the findings were significant but that Londoners should stay calm. "First of all pregnant women shouldn't panic," she said.

"The increased risk is relatively small compared with smoking, which we know raises the risk of low birth rate.

"But even if it is a small increased risk, all Londoners are exposed to air pollution and it's difficult for individuals to make an impact on their exposure."

Pollution in London

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She said the findings should be a wake-up call to policy-makers as they consider the impact traffic emissions have on ordinary people.

"It is exactly 65 years since the Great Smog of London that caused many deaths, and the response to that was the Clean Air Act. Air pollution is again damaging the health of Londoners even before they are born," she said.

She added: "Introducing policies restricting the use of diesel will have the most health benefit."

Low birth weight - defined as less than 2,500 grams - is consistently linked to higher rates of infant mortality as well as diseases such as diabetes and cardiovascular problems in later life.

Although the study looked at various pollutants including nitrogen dioxide and ozone, PM2.5 was found to be the most influential factor on low birth weight.

Three per cent of all cases of low birth weight in babies born at term in London were thought by researchers to be "directly attributable" to exposure to PM2.5 concentrations of more than 13.8 micrograms/m3.

Data from the London Atmospheric Emissions Inventory showed in October that every area of London exceeds World Health Organisation (WHO) limits for PM2.5 of 10 micrograms/m3. In central London the average annual levels are nearly double the WHO limit of 10 micrograms/m3.

Researchers said the study suggests that a reduction of 10 per cent in average PM2.5 levels would prevent 90 babies, or three per cent of cases, from being born at term with low birth weight each year in London.

The study, by scientists at Imperial College London and published in the British Medical Journal, examined birth data from inside the M25 from 2006 to 2010.

In what is believed to be the largest UK study on air pollution and birthweight, data from about 670,000 births was cross-referenced against the mother's address.

Addresses were checked against a dispersion model based on London emissions data for average monthly concentrations of nitrogen dioxide, nitrogen oxides, ozone and PM2.5 and PM10 particles.

Shirley Rodrigues, the Deputy Mayor of Environment & Energy told the Standard: “The toxic air that Londoners are forced to breathe is nothing short of a health crisis."

She added that Mayor of London Sadiq Khan has prioritised measures to make the capital's bus and taxi fleet cleaner, introducing the T-Charge and the ULEZ early to reduce dirty vehicle emissions.

"The Mayor recently revealed that not a single area of London meets World Health Organisation recommended health standards. We know for a fact that air pollution exacerbates chronic illnesses and shortens life expectancy,” she added.

Children exposed to PM2.5s are more likely to grow up with reduced lung function and develop asthma.

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