india

Updated: Apr 12, 2019 00:08 IST

Noxious fumes from traffic cause four million new cases of childhood asthma every year, of which 350,000 occur in India, according to the first global study that makes a case for tougher air pollution laws worldwide to protect children.

Traffic pollution-attributable childhood asthma was low in India, which ranked 58th among 194 countries.

South Korea was the worst affected, with 31% children affected by noxious vehicular emissions, with China ranking 19, the United Kingdom 24, and the United States 25, found a health impact assessment of children in 194 countries and 125 major cities worldwide, published in The Lancet Planetary Health.

Eight of 10 cities with the highest proportion of cases were in China, along with Moscow in Russia, and Seoul in South Korea.

There was huge variation in the proportion of cases attributable to traffic emissions across cities.

The variation ranged from 6% in Orlu, Nigeria, to 48% in Shanghai, China.

The study uses nitrogen dioxide (NO2) levels as an indicator of traffic pollution. In most urban centres, road traffic accounts for up to 80% of ambient NO2, which is produced largely by diesel vehicles. It accounts for 13% of childhood asthma linked to traffic pollution.

With 92% of cases emerging in areas that have traffic pollution levels below WHO guidelines of 40ug/m3 (21 parts per billion), the study authors suggest that this limit be reviewed.

“NO2 levels may not be high all the time but during winter at high traffic zones and around power plants, it occasionally breaches the standard. NO2 levels are important because it reacts with volatile organic compounds in the presence of sunlight and forms Ozone (O3), which affects both asthmatics and healthy people. It is gradually developing in to a problem in India,” said SN Tripathi, professor at the Centre for Environmental Science and Engineering at IIT-Kanpur.

In congested city centres in India, levels are often high. At Delhi’s Anand Vihar, for example, the 24 hour average concentration of NO2 ranged between 74-118 ug/m3 (micrograms per cubic metre) between April 1 and April 6, 2019, which is well above the annual safe limit of 40ug/m3.

Asthma is the most commonly reported non-communicable disease in children worldwide, with prevalence of childhood asthma in India ranging between 8% and 12%.

“Childhood asthma prevalence in India has increased dramatically, especially in children who live near arterial roads. Several components of traffic emission, such as carbon and other particulate matter, ozone and carbon monoxide, can irritate and inflame the airways and lead to asthma in those with airway sensitivity, we need a deep-dive into the triggers for children in India,” said Dr Arvind Kumar, chairman of the centre for chest surgery at Sir Ganga Ram Hospital in New Delhi, and founder-trustee of the Lung Care Foundation, which works on lung health and asthma prevention in 25 Delhi schools.

The study says policy initiatives that lower traffic-related pollution, such as China’s electrification of Shenzhen’s bus fleet and London’s ultra-low emission zone congestion charges, can reduce greenhouse emissions and improve children’s health.