Pollution control board contests Lancet study on air pollution deaths, claims data ‘not absolute’

The Central Pollution Control Board in the National Green Tribunal opposed the findings of a Lancet study, which claimed poor air quality had severely affected mortality rates in 10 major Indian cities.

Claiming the study's data may not be "absolute", the CPCP said the deaths couldn't be attributed to pollution alone and that the satellite data and modelling techniques used for extrapolations in it may not necessarily represent the “realistic Indian scenario.”

The NGT had taken suo motu cognizance of a newspaper report quoting the study, which stated approximately 33,000 annual deaths were linked to air pollution levels that exceeded the World Health Organization guidelines.

The study examined the cities of Delhi, Ahmedabad, Bengaluru, Chennai, Hyderabad, Kolkata, Mumbai, Pune, Shimla, and Varanasi.

In its reply dated November 4, the CPCB said the study analyzed the daily average particulate matter (PM) 2.5 concentrations at one square kilometer spatial resolution across the country between 2008 and 2020. It also used mortality records from each municipal corporation in the 10 cities.

"The study concludes that short-term PM2.5 exposure was associated with a high risk of death in India, even at concentrations below the current Indian PM2.5 standard. These associations were stronger for locally generated air pollutants. However, the study has limitations...," claimed the CPCB report.

According to the pollution control board, the "variability in the strength of death registration systems across different states and cities" and the analyses of "cause-specific mortality" as "the international classification of disease codes" was not done by the authors for most cities.

"In the absence of cause of death data, several extrapolations of data take place. Therefore, the deaths cannot be attributed to air pollution alone and thereby may not portray a correct comparison," it claimed.

Regarding the adverse health impact of PM2.5 and other pollutants, the CPCB report said air pollution was one of the factors affecting respiratory ailments and associated diseases.

It said an individual’s health was also influenced by several factors, including food habits, occupational habits, socio-economic status, medical history, immunity and heredity.

"Ground monitors-based data and satellite study-based data have been used for PM2.5 measurements using a generalized model...satellite data and modelling techniques used for extrapolations may not necessarily represent the realistic Indian scenario and that such an analysis may not be absolute," it added.

The CPCB said cities exceeding the national ambient air quality annual standards for PM10 concentrations for five consecutive years had been designated as non-attainment cities (NAC).

"CPCB has identified 130 non-attainment and million-plus cities in the 24 states and union territories including Ahmedabad, Bengaluru, Chennai, Delhi, Hyderabad, Kolkata, Mumbai, Pune, and Varanasi," the report said.

It said the national clean air program (NCAP) was launched in January 2019 to reduce PM10 concentration by 40 per cent in these 130 cities by 2025-26.

"With the implementation of comprehensive NCAP and various policy interventions, of 130 identified cities, a decrease in PM10 concentration has been observed in 95 cities during 2023-24 as compared to levels during 2017-18," said the CPCB report.

(PTI)