A study conducted in Ambattur, Kolathur, Saidapet and Egmore by the department of environmental management, Bharatidasan University, Tiruchy, showed the average concentration of particle-associated PAHs ranged from 325.7 to 790.8 nanogram/cubic metre — an alarming pollution level — in Chennai.

According to Anumita Roychowdhury, executive director, research and advocacy, Centre for Science and Environment (CSE), the study was published in 2011, and the high PAH levels were attributed to increasing vehicular traffic.

The maximum PAH level of 790.8 nanogram/cubic metre was recorded in Egmore (urban commercial area), followed by the industrial hub of Ambattur (582.9 nanogram/cubic metre). “PAHs are mostly emitted by diesel vehicles. There is a need to spruce up air quality monitoring to track these toxins,” she said.

Ms. Roychowdhury was speaking at a city dialogue on clean air and sustainable mobility on Tuesday. “We need to move to cleaner diesel that has less sulphur content,” she said.

Former Central Pollution Control Board scientist Manoharan said heavy vehicle manufacturers could look at making vertical vehicle exhausts so the impact of pollution on human beings is reduced.

Bhure Lal, chairman, Environment Pollution Control Authority (EPCA), said more States were becoming aware of the problem of air pollution and setting up monitoring stations.