Howrah is the second most polluted city in the country in terms of nitrogen oxide emission, says a report by the Center for Science and Environment.

Nitrogen oxide is mainly released by diesel-driven vehicles and industrial units. Prolonged exposure to it can affect lung function. The report, which used 2019 data, shows Howrah had annual nitrogen oxide level of 72microgram per cubic meter of air. Only Pune’s data is worse — 75.