Nearly a third of Indian cities have breached annual pollution limits mandated by the Central Pollution Control Board (CPCB) between 2011 and 2015, according to figures from the Union Environment Ministry-affiliated organisation.

The numbers — the latest available and updated in blocks of 4 years — sourced from 680 pollution-monitoring stations spread over 300 cities across the country, measure levels of particulate matter (PM 10), nitrogen dioxide (NO2), and sulphur dioxide (SO2).

94 cities crossed norms

While cities such as Delhi are usually the worst performers with regard to pollution spikes in winter, the CPCB data show that 94 cities spanning States from Andhra Pradesh to Jammu and Kashmir and Assam to Gujarat were guilty of breaching the annual, particulate matter limit of 60 micro-gram per cubic metre.

Delhi; Badlapur, Pune and Ulhasnagar in Maharashtra; and Kolkata additionally transgressed the NO2 levels.

While cities like Delhi, Mumbai and Pune measure PM2.5 levels, most lack the sensors required to gauge the presence of these minute particles that are considered more toxic than the more-commonly measured PM 10.

Monitoring and enforcing pollution limits was done by the State pollution control boards and the Centre could only send advisories, according to officials.

“The CPCB can only give guidelines on controlling air pollution, it is up to the States to implement them,” said D. Saha, Head, Air Pollution Monitoring, CPCB. He added that the agency only calculated average figures because there was tremendous variation within a year among cities, mostly on account of rainfall.

The numbers come on the back of international research reports attributing about a million deaths in India to air pollution. The Environment Ministry has said these mortality figures were “extrapolations without due scientific validation” but hasn’t countered with numbers of its own. It is, along with the Health Ministry, working on a study to assess ‘official’ mortality from air pollution.

Key directives by the Centre to the States to control particulate matter pollution include promoting public transport, improving fuel quality and fuel efficiency standards and banning burning of leaves, biomass and municipal solid waste.