Under one in 10 childhood asthma cases linked to traffic

Just under one in ten cases of Irish childhood asthma is linked with traffic pollution, according to a new global study.

The research, which has just been published in the Lancet Planetary Health journal, revealed that traffic-related air pollution is linked to 4m new cases of childhood asthma every year.

The country with the highest percentage of traffic pollution-attributable childhood asthma incidence was South Korea with 31% of cases.

Ireland ranked No 122 out of 194 countries with 9% of cases of childhood asthma linked to fuel fumes while the UK ranked 24th at 19%, which is almost double the Irish rate.

It is estimated that just under half a million people (470,000) in Ireland have asthma which includes one in five children. The Asthma Society of Ireland says this country has the fourth highest prevalence of the disease in the world.

Globally, the new Lancet study estimates suggest that there are 170 new cases of traffic pollution-related asthma per 100,000 children every year, and 13% of childhood asthma cases diagnosed each year are linked to traffic pollution.

Authors suggest that pollution guidelines may need to be re-evaluated, as most children developing traffic pollution-related asthma lived in areas within recommended levels.

The first global estimates of their kind come from the health impact assessment of children in 194 countries and 125 major cities worldwide.

In the study, the authors used nitrogen dioxide as a stand-in or a marker for the traffic pollution. The gas is a pollutant which comes mainly from the burning of fuel with traffic emissions contributing up to 80% of nitrogen dioxide in cities.

The authors combined a global dataset of the presence of ambient nitrogen dioxide with data on population distribution and asthma incidence to estimate the number of new traffic pollution-related asthma cases in children aged from one to 18 years.

“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, George Washington University, USA.

Our findings suggest that the World Health Organisation guideline for annual average NO2 concentrations might need to be revisited, and that traffic emissions should be a target to mitigate exposure.

Globally, asthma is the most common non-communicable disease among children.

The study says traffic-related air pollution may result in asthma development as pollutants may cause damage to the airways, leading to inflammation that triggers asthma in genetically predisposed children.

It adds that although it is not yet clear which specific pollutant within the traffic-related air pollution is linked to asthma, reviews by the US Environmental Protection Agency and Health Canada suggest that a causal relationship is likely to exist between long-term nitrogen dioxide exposure and childhood asthma development.

The country with the highest rate of traffic pollution-related childhood asthma was Kuwait with 550 cases per 100,000 children each year, followed by the United Arab Emirates with 460 per 100,000, and Canada with 450 per 100,000.Ireland is at No. 102 in the world with 150 per 100,000 children per year with Switzerland and Botswana having the same rates.

Lead author Ploy Achakulwisut, George Washington University, USA, said the study indicates that policy initiatives to alleviate traffic-related air pollution can lead to improvements in children’s health and also reduce greenhouse gas emissions