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Pollution, Air Quality, Public Health and Mobility Challenges in Chennai

Vehicular PollutionChennai, IndiaAccording to this year’s Global Burden of Disease estimates, one-fifth of deaths across the world occur from outdoor air pollution. Also, outdoor air pollution is the fifth leading cause of deaths in India. These alarming pieces of information have drawn everyone’s attention and forced experts to take stock of pollution trends in India’s cities – including Chennai.

A recent analysis of Chennai’s air quality, done by Centre for Science and Environment (CSE), the New Delhi-based research and advocacy body, indicates that though Chennai shows deceptively low to moderate pollution levels because of its location near the sea, local impacts and exposure are high and the pollution levels are rising steadily, thereby increasing public health risks.

CSE released the findings of its analysis at Chennai on August 6 at a stakeholder workshop – Chennai City Dialogue on Clean Air and Sustainable Mobility: An Agenda for Action – conducted in association with the Tamil Nadu State Pollution Control Board. Bhure Lal, Chairperson of the Supreme Court’s Environment Pollution (Prevention and Control) Authority, and Anumita Roychowdhury, Executive Director – Research and Advocacy, CSE, addressed the participants.

Said Roychowdhury, “Chennai’s case is different from the trends observed in other high-growth megacities where overall ambient air pollution is very high. But this must not breed complacency as detailed scanning of available pollution data as well as research studies point to steady and rapid increase over time, high local impacts and high traces of toxics making Chennai’s air dangerous to breathe. This demands more rigorous scrutiny of air pollution profile and aggressive action in this rapidly motorizing city.”

Key Findings

Annual average levels of particulates increasing rapidly: Though lower than other megacities of India, a rapid escalation in levels has been witnessed in Chennai: PM10 levels have increased from 32 microgram per cu m in 2007 to 94 microgram per cu m in 2011 (a 193 per cent jump) – increasing at 29 per cent a year.

Annual average levels of nitrogen dioxide increasing at a more rapid rate than PM10: Between 2007 and 2011, NO2 levels rose from 9 microgram per cu m to 24 microgram per cu m – an increase of 166 per cent, at 60 per cent a year. An official source apportionment study in Chennai carried out by IIT Madras under the aegis of the Ministry of Environment & Forests (MoEF) attributes 63 per cent of nitrogen oxides to vehicles.

Pollution hotspots inside the city: In localities like Kathivakkam, Manali and Thiruvottiyur, the daily average pollution levels go up 1.3 times the standards. The peak levels can be as much as 2.0 to 2.42 times the standards.

Studies indicate high traces of carcinogenic toxins: A group of air toxins that are not part of official routine monitoring have been studied by the scientists of Department of Environmental Management, Bharatidasan University, Tiruchirappalli in Ambathur, Kolathur, Saidapet, and Egmore areas. Results published in 2011 show high levels of polycyclic aromatic hydrocarbons (PAH), a group of toxic carcinogens. Average concentration of particle-associated PAHs ranged from 325.7 to 790.8 nanogram per cu m, which is alarming. The same study found more toxic compounds, among them benzo-a-pyrene – an indicator of carcinogenic risk – varying between 6.8 and 16.4 nanogram per cu m, exceeding the national standard for annual average of 1 nanogram per cu m. PAHs are known to come more from diesel vehicles. There is a need to spruce up air quality monitoring to track these toxins.

There cannot be any room for complacency about comparatively lower level of particulates in Chennai. Though the overall particulate levels are comparatively lower than other regions in the country, they are much above World Health Organization (WHO) guidelines. Global assessments now available from the Global Burden of Disease estimates show that the most of the health effects occur at lower levels. Chennai has several local pollution hotspots, and road side exposures are also high. Annual averages do not help address the risks. Air quality monitoring would need to address these challenges and issue health advisories to people.

There is, therefore, absolutely no reason to think that the risk in southern cities like Chennai is lower than other cities. In fact, a health study released by the Health Effects Institute in Chennai and Delhi in 2011 shows that in Chennai, there is a 0.4 per cent increase in risk per 10-µg/m3 increase in PM10 concentration. In Delhi, it is 0.15 per cent – thus Chennai indicates a higher impact.

Road TransportVehicles are a Special Problem

High exposure to vehicular fumes: Vehicles pose a special challenge. In terms of actual exposure, people are more vulnerable to vehicular fumes while traveling and in close proximity to roads. Pollution concentration in our breath is 3-4 times higher than the ambient air concentration. In densely-populated cities, more than 50-60 per cent of the population lives or works near the roadside where levels are much higher. This is very serious in low income neighbourhoods located close to roads. Road users, public transport users, walkers and cyclists are the most exposed groups – they are also the urban majority.

Vehicles contribute hugely to air pollution: Source apportionment studies carried out in Chennai by IIT Madras under the aegis of the Ministry of Environment and Forests show vehicles contribute 14 per cent of particulate matter and 68 per cent of nitrogen oxides. Some other studies show that 35 per cent of PM2.5 in Chennai comes from vehicles – tinier the particles higher the share of vehicles.

Chennai records very high exposure to vehicular pollution: A study carried out by scientists of University of Berkeley published in the journal Environmental Science and Technology in 2012 shows that the exposure to vehicular fumes (in terms of population-weighted intake fraction, or the grams of vehicular pollution inhaled per grams of vehicular pollution emitted) in Chennai (72) is one of the highest in cities studied in India – third after Kolkata (150) and Delhi (100).

Leapfrog technology to address diesel emissions, which is a Class 1 carcinogen: India is motorizing at a level of technology and fuel quality that can compound health risks. There are special concerns about growing use of poor quality diesel. The International Agency for Research on Cancer (IARC), a wing of the WHO, has said that diesel engine exhaust can certainly cause cancer, especially lung cancer in humans. This finding comes at a time when India has failed to adopt a clean diesel roadmap, prevent use of under-taxed and under-priced toxic diesel in cars.


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