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Foul air a slow poison for Delhi lungs round the year

A view of the Qutub Minar engulfed in dense smog, New Delhi, on Thursday, November 14, 2019. (Sanjeev Verma/HT PHOTO)

People in Delhi were exposed last year to pollution levels 11 times higher than what is considered safe by the World Health Organization, an analysis of average PM2.5 particle concentrations showed, suggesting the crisis was not limited only to pre-winter months when the levels reach concentrations up to 45 times as high as the global standards and become a talking point.

According to Central Pollution Control Board (CPCB) data, Delhi’s annual average PM 2.5 (particulate matter of 2.5 micron size) last year was 115 microgram per cubic metre while the WHO recommends this be kept under 10 micrograms per cubic metre.

PM2.5 are ultra-fine particles roughly 3% of the diameter of an average human hair and lead to the most harmful of health effects, including respiratory distress and cardiovascular conditions, that have been linked to millions of premature deaths around the world every year.

“The WHO guideline is 10 micrograms per cubic metres for a reason. The levels we are recording round the year are not safe at all. That needs to be understood by policymakers,” Sagnik Dey, associate professor at IIT Delhi.

Till November 14 this year, the average is 97.7 micrograms per cubic metre based on data from the CPCB’s continuous monitoring stations. This cannot be compared with the CPCB’s average for last year because it may not have considered the same number of stations to calculate the average. The chronic health effects begin at annual mean concentrations are as low as 11-15 micrograms per cubic metre, according to the WHO’s air quality guideline document.

Each time there is a severe spike in air pollution level as has been for the last couple of days when PM 2.5 concentrations ranged from 250 to 450 micrograms per cubic metre, people worry for their health and rush to wear masks or opt to stay indoors. Health impacts can be curbed only if the annual average concentrations is reduced drastically through various interventions.

The WHO has devised intermediate targets for countries that are higher than the 10 micrograms per cubic metre, which “have been shown to be achievable with successive and sustained abatement measures”, says the WHO air quality guideline document.

The first and most lenient target is 35 micrograms per cubic metre, which is associated with significant deaths in the developed world; the second is 25 micrograms per cubic metre that would reduce health risks from long-term exposures by 6% as compared to the first goal. The toughest target is 15 micrograms per cubic metre.

India’s national air quality standards were devised in 1982, revised in 1994 and again in 2009, when the annual average standard was set at 40 micrograms per cubic metre and a 24-hour standard of 60 micrograms per cubic metre.

“The IIT Kanpur team did an extensive study on health impacts from pollution around the world. The WHO guideline was also considered. But in India, the background pollution levels are so high that even if we stopped all vehicles, industries etc, we may not be able to meet the WHO guideline. Our topography is such that there is a lot of windblown dust. WHO guidelines were developed based on European conditions,” said B Sengupta, who was the member secretary at CPCB when the 2009 standards were notified.

“The satellite data shows that pollution levels have kind of stabilised in Delhi but they have definitely not come down and the annual average remains 110+ micrograms per cubic metres, which is extremely high. Our data also indicates that annual PM 2.5 concentrations came down around 2002 after CNG was introduced in public transportation, but started rising 2005 onwards,” said Dey.

“Health evidences show that most of the health effects of air pollution — premature deaths and illness — occur at a level that is much lower than the annual average level we record in Delhi. Multisector action plan has to reduce year-long exposure to meet health based guidelines,” said Anumita Roychowdhury, executive director, Centre for Science and Environment.

The State of Global Air 2019, which makes a direct link between air pollution concentrations and premature mortality, said that air pollution was the fifth largest risk factor for premature deaths in 2017. It said there was a causal relationship between exposure to ambient PM2.5 and ischemic heart disease, cerebrovascular disease (stroke), diabetes, lung cancer, chronic obstructive pulmonary disorder, and lower-respiratory infections (in particular, pneumonia).

Spikes are equally important to be controlled because a PM10 concentration of 150 micrograms per cubic metre would translate into roughly a 5% increase in daily mortality, according to the WHO.

Experts hope that the National Clean Air Programme of the Centre launched last year, which aims to reduce PM2.5 pollution by 20 to 30% over 2017 levels by 2024 in 102 cities, is strictly enforced. As of today, only 102 city action plans have been developed but they are yet to be implemented, with the plans lacking regional focus and being limited to the municipal limits of each city.

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