Fumes contribute to four million new cases of asthma in children around the world every year, according to a study published in the medical journal The Lancet. The research suggests that 13 per cent of childhood asthma cases diagnosed are linked to traffic pollution.
The country with the worst overall figure was South Korea, where almost a third of cases had a link to traffic pollution. China was ranked 19th in the world, with the UK was ranked 24th, and the US 25th. There was a huge variation between different cities, with almost half the cases in Shanghai (48 per cent) linked to car fumes.
The research was collated by a team from America's George Washington University. It looked at 125 cities around the world, and combined measurements of nitrogen dioxide levels from ground-level monitors and satellite data, with population distribution and asthma incidence figures. These were used to estimate the number of new traffic pollution-related asthma cases in children up to the age of 18.
"Nitrogen dioxide pollution appears to be a substantial risk factor for childhood asthma incidence in both developed and developing countries, especially in urban areas," says senior author Dr Susan
Anenberg. "Our findings suggest that the World Health Organisation guideline for annual average concentrations might need to be revisited, and that traffic emissions should be a target to mitigate exposure."
Nitrogen dioxide is a waste product of fossil fuel combustion, and traffic emissions can contribute up to 80 per cent of ambient levels of the gas in cities. The study estimates that there are 170 new cases of traffic pollution-related asthma per 100,000 children every year. However the report’s lead author, Ploy Achakulwisut, points out that some authorities are taking effective measures to tackle the problem.
"Policy initiatives can lead to improvements in children’s health and also reduce greenhouse gas emissions”, she says. “Recent examples include Shenzhen's electrification of its entire bus fleet, and London's Ultra-Low Emission Zone congestion charges.”
Asthma is the most common non-communicable disease among children world-wide, and the World Health Organisation says its prevalence has increased dramatically since the 1950s. It’s believed pollutants may cause inflammation to airways that triggers asthma in genetically predisposed children. The US Environmental Protection Agency, and Health Canada have suggested that a causal relationship between long-term nitrogen dioxide exposure and childhood asthma development is likely.
A recent German study suggested that traffic-related pollution could be leading to more deaths than smoking. The results, published in the European Heart Journal, showed that every year an average of 120 people out of every 100,000 inhabitants around the world die prematurely from the consequences of polluted air. The World Health Organisation estimates that smoking – including passive smoking – causes 7.2 million deaths annually worldwide.
