India’s air pollution monitoring: Study hints at bias
THE MANUAL STATIONS IN INDIA COLLECT SAMPLES OVER EIGHTHOUR SPANS TYPICALLY TWICE A WEEK
NEW DELHI: India’s network of manual and real-time (automatic) air pollution monitoring stations is resulting in an information bias and may not be giving a representative picture for health epidemiology studies, a new study done by US and Indian scientists this year revealed.
Currently, India has one air pollution monitoring station for every two million people. It has more manual than real time monitoring stations. The realtime stations are concentrated in north India, some western and southern states — Delhi, Uttar Pradesh, Rajasthan, Maharashtra, Telangana — but there is no real-time data reporting from central states — Chhattisgarh, Jharkhand, Odisha — that have a heavy burden of polluting industries and mines. There are no real-time stations in the northeastern states either.
The report — ‘Monitoring Particulate Matter in India: Recent Trends and Future Outlook’ — to be published shortly, has mapped manual air pollution monitoring stations under the National Air Quality Monitoring Programme (NAMP) based on population density, and found that air pollution dataset from India mainly represents urban and peri-urban areas. Lack of data from rural areas may also be contributing to exposure misrepresentation, the study found.
While urban bias in such monitoring is known, the report has raised questions about data quality from manual monitoring stations and discussed trends in PM 10 (coarse pollution particles) concentrations from 2004 to 2015 from the NAMP.
MANUAL VERSUS AUTOMATIC STATIONS
There are 683 manual air quality stations in 300 cities and towns and a network of 87 continuous automatic air quality monitoring stations (CAAQMS) that provide data in real time from 52 cities in only 15 states, the report found. India’s sparse pollution monitoring network can be contrasted with 87 monitoring stations for PM 10 and 32 for PM 2.5 in Greater London that has a population of about 9 million.
The manual stations in India collect samples over eight-hour spans typically twice a week, which may not provide representative air quality status. Manual monitoring also results in delay in data collection and has a large error margin and variation. Manual stations should pick up data for at least 104 days a year, but at most stations, data was captured for fewer days than required. Besides, in states like Manipur and Arunachal Pradesh, even manual station density is very poor and only data for two to five years is available.
The report added that there was no meta data or quality control data available for public scrutiny.
A senior Central Pollution Control Board (CPCB) official said the number of stations has increased marginally since this study was conducted. “We have recently added a few stations. There are 703 manual stations in 307 cities and 134 continuous stations in 71 cities.
There is a target to have 1,000 manual stations shortly and realtime stations in all million-plus cities, state capitals and rural areas under the National Clean Air Programme (NCAP),” he said.
On the advantages of manual monitoring, he said, “We can always conduct chemical speciation (analysis) after collecting particulate matter on filter paper while the advantage of real-time station is there is no time lapse...”