Researchers say that World Health Organisation traffic pollution guidelines need to be re-evaluated as the vast majority of children developing traffic pollution-related asthma lived in areas within recommended levels. In a new study* they estimate that some four million new cases of childhood asthma every year are related to traffic fumes.
The first global estimates of their kind suggest that more than one in 10 childhood asthma cases could be linked to traffic-related air pollution every year, according to the health impact assessment of children in 194 countries and 125 major cities worldwide, published in The Lancet Planetary Health journal.
Globally, they 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.
The country with the highest proportion of traffic pollution-attributable childhood asthma incidence was South Korea (31%), the UK ranked 24th out of 194 countries, the US 25th, China 19th, and India 58th.
Of the 125 cities studied, there was a large variation in the proportion of childhood asthma cases attributable to traffic pollution – from 6% in Orlu, Nigeria, to 48% in Shanghai, China. Of the 10 cities with the highest proportion of cases, eight were in China, alongside Moscow, Russia, and Seoul, South Korea.
In the study, the authors used NO2 as a surrogate for the traffic pollution mixture to focus specifically on the effects of traffic pollution on childhood asthma development. NO2 is a pollutant formed mainly from fossil fuel combustion, and traffic emissions can contribute up to 80% of ambient NO2 in cities. NO2 is just one component of air pollution, which is made up of many pollutants (including particulate matter, ozone, carbon monoxide), which are known to have numerous adverse effects on health.
The authors combined a global dataset of ambient NO2 (modelled from ground-level monitors, satellite data, and land use variables such as road networks) with data on population distribution and asthma incidence to estimate the number of new traffic pollution-related asthma cases in children aged 1-18 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 Organization guideline for annual average NO2 concentrations might need to be revisited, and that traffic emissions should be a target to mitigate exposure.”
Lead author Ploy Achakulwisut, George Washington University, added: “Our 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. Recent examples include Shenzhen’s electrification of its entire bus fleet and London’s Ultra-Low Emission Zone congestion charges.”
*Achakulwisut P, Brauer M, Hystad P, et al. Global, national, and urban burdens of paediatric asthma incidence attributable to ambient NO2 pollution: estimates from global datasets. The Lancet Planetary Health, Published: April 10 2019. DOI:10.1016/S2542-5196(19)30046-4