Two studies published by researchers in London this week (5 December) have uncovered health impacts from exposure to air pollution in both unborn babies and the over-60s.
The research adds to a ‘growing body of evidence showing the negative impacts of urban air pollution on cardiovascular and respiratory health’ according to Imperial College London – one of the institutions to have participated in the research.
The first study, published in The BMJ, was carried out at the MRC-PHE Centre for Environment and Health at Imperial College London and Kings College London, and looked at the impact of air and noise pollution on the health of around half a million infants.
Findings of the study suggested that pregnant mothers exposed to air pollution from air pollution in the capital are more likely to give birth to babies that are underweight or smaller than they should be. The study found no conclusive effect on babies health by noise pollution.
According to the authors, cutting the average concentration of fine particle pollution emitted by the city’s road traffic by just 10% could prevent around 90 babies a year (3% of cases) being born with low birth weight.
The researchers used data from the London Atmospheric Emissions Inventory to estimate average monthly concentrations of pollutants related to road traffic, including nitrogen dioxide (NO2), nitrogen oxides (NOx), and fine particulate matter (PM2.5) and larger particulate matter (PM10). Average day and night-time road traffic noise levels were also estimated.
Analysing the data, they estimated that higher levels of these air pollutants, particularly PM2.5, were associated with 2% to 6% increased odds of low birth weight and 1% to 3% increased odds of being small for gestational age.
Commenting on the findings, Dr Mireille Toledano, from the School of Public Health at Imperial College London and senior author of the research, said: “Our study has shown that a small but significant proportion of babies born underweight in London are directly attributable to exposure to air pollution, particularly to small particles produced by road traffic.
“Babies born with low birth weight or who are small for their gestational age, are at increased risk of dying within their first month, as well as diseases in later life, such as cardiovascular disease. Any policies aimed at reducing road traffic pollution in urban environments could therefore help to reduce the health impact on unborn babies and their life-long disease risk.”
The project was also supported by the UK Natural Environment Research Council, the Medical Research Council, the Economic and Social Research Council, the Department of Environment, Food and Rural Affairs, and the Department of Health.
The second study, published in The Lancet, suggested that short term exposure to air pollution in built up areas can prevent the positive effects on the heart and lungs that can be gained from light exercise such as walking in older adults.
The project was again led by researchers from Imperial College London alongside Duke University.
In the study, researchers recruited 119 volunteers through the Royal Brompton Hospital in London, who were over the age of 60 and were either healthy, had stable Chronic Obstructive Pulmonary Disease (COPD), or had stable heart disease.
Patients walked for two hours in two London settings at midday; in a ‘relatively quiet’ part of Hyde Park and along a section of Oxford Street.
Physical measurements were taken before and after the walks to show the effects of the exercise on cardiovascular health, including measurements of lung volume exhaled, blood pressure, and the degree to which the blood vessels could expand.
Environmental measurements were also collected, to track pollution levels and volunteers’ exposure. Data analysis was carried out at the MRC-PHE Centre for Environment and Health at Imperial College London and Kings College London, and the Rutgers School of Public Health in New Jersey.
Analysis revealed that participants benefitted from walking in the park, with lung capacity improving within the first hour and a significant lasting increase for more than 24 hours in many cases. But, a walk along a busy roadside led to only a small increase in lung capacity in participants, far lower than recorded in the park, the research suggested.
Blood flow also increased after exercise, with decreases in blood pressure and an increase in heart rate. Arteries became less stiff in those walking in Hyde Park with a maximum change from baseline of more than 24% in healthy and COPD volunteers, and more than 19% in heart disease patients.
This effect was reduced when walking along Oxford Street, the researchers added, with a maximum change in arterial stiffness of 4.6% for healthy volunteers, 16% for those with COPD and 8.6% for heart disease patients.
The authors add that it is possible that stress could account for some of the physiological differences seen between the two settings, with the increased noise and activity of Oxford Street having an effect. They also claimed that while the study only involved two relatively short walks, the findings suggest that repeated exposures to air pollution would not be beneficial to respiratory and cardiovascular systems.
Commenting on the results, Fan Chung, Professor of Respiratory Medicine and Head of Experimental Studies Medicine at the National Heart & Lung Institute at Imperial College London and senior author of the study, said: “These findings are important as for many people, such as the elderly or those with chronic disease, very often the only exercise they can do is to walk. Our research suggests that we might advise older adults to walk in green spaces, away from built-up areas and pollution from traffic.”
The study was funded by the British Heart Foundation.
STUDY 1: Impact of London’s road traffic air and noise pollution on birth weight: a retrospective population-based cohort study
STUDY 2: Respiratory and cardiovascular responses to walking down a traffic-polluted road compared with walking in a traffic-free area in participants aged 60 years and older with chronic lung or heart disease and age-matched healthy controls: a randomised, crossover study