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In Delhi, indoor pollution worse than outdoor

Ridden as they are with vehicular-pollution, roads actually offer safer breathing air than what obtains in most homes, says a new scientific study.

Pollutants found in indoor air are similiar to those found outdoors and in some instances, they actually come from outdoor sources according to a new study, Exposure assessment in the middle class sub-population of east Delhi.

The study revealed that Mayur Vihar in east Delhi presented a classic example of a residential area where indoor concentrations of suspended particulate matter was found to be almost double to that found outside.

Regular heavy traffic on the nearby highways, proximity to the Noida industrial belt and fly ash from the nearby power plants all contribute to poor ambient air inside homes in Mayur Vihar and the surrounding areas of east Delhi.

Interestingly, levels of SPM -- a dangerous pollutant emanating from diesel vehicles -- at all locations in east Delhi was found far better during the day time than during the night owing to the phenomenon of ''atmospheric inversion'' which is very active at sunset and prevents dispersion of air pollutants during the night.

Upon sunrise, the earth's surface gets heated and the connective current generated upon heating rise vertically till noon and gradually erodes and destroys the ground inversion layer formed and stabilised during the evening. Car exhaust and fine particles can readily infiltrate into homes especially if windows are kept open but there are significant internal sources of pollution adding to the problem, according to Dr Mahendra Pandey, scientist at the Central Pollution Control Board.

A variety of pollutants originate inside the home from such human activities as cooking, cleaning, smoking and heating. Many studies have shown that the concentrations of pollutants inside the kitchen can be 60 times higher than that found in the outside environment.

If raw fuels such as cowdung, wood, leaves and sawdust are used, the problem is naturally worse because organic fuels generate thousands of pollutants, including carcinogens increasing the risk of lung cancer. Women are naturally at a greater risk.

But the east Delhi study showed that even in homes where relatively safer fuels such as cooking gas are used, the concentration of pollutants could be significantly greater than in the outside air nearby.

In fact, almost none of the middle-class families surveyed used raw biomass fuels such as cowdung or firewood and separate investigations had to be mounted to discover the source of pollutants.

According to Dr Pandey, while pollutants disperse rapidly outdoors, they stay trapped indoors for a very long time, increasing exposure levels of inmates. Chronic effects of indoor pollution include inflammation of the respiratory tract caused by reduced resistance to respiratory infections which in turn enhances susceptibility to the inflammatory effects of smoke and fumes to establish a vicious cycle of pathological changes.

Most pregnant women in India are already anaemic due to malnutrition and at such a stage, exposure to pollutants, particularly carbon monoxide, is naturally dangerous, Dr Pandey said.

The biological effects of CO exposure on the foetus and to newborns are not yet clear but studies have shown that babies delivered by mothers who live in high indoor concentrations of CO weigh less than those delivered by mothers living in normal conditions.

High concentrations of CO may be found in kitchens and living rooms in which cooking gas is used improperly and without proper ventilation. Deaths have been reported in winters due to acute poisoning.

In east Delhi, 23 per cent of the population was found to be suffering from severe respiratory disorders while another 31 per cent was found to be suffering from mild or moderate breathing problems.

Adult females were the worst sufferers from ailments such as asthma and allergic rhinitis, further confirming that people who stay indoors are exposed more to pollutants.

The main problem with indoor pollutants is that most of them are smaller and can be inhaled easily. Called respirable particulate matter these pollutants easily penetrate homes.

According to Dr Nandita Shukla, a research assistant with the Council of Scientific and Industrial Research, each home resembles a reaction vessel in a laboratory with chemicals continually entering and exiting.

Some of these chemicals can react with one another creating products such as free radicals which are potentially irritating and would be negligible were it not for continued renewal.

Other products of indoor chemistry are more stable than free radicals, but are difficult to detect using the sampling and analysis techniques currently applied to indoor air.

Dr Pandey and Dr Shukla say that effective techniques exist to control indoor pollutants but these call for much higher levels of public awareness and co-operation.

Meanwhile, the only people who benefit are chemists who are selling drugs for respiratory disorders at an increasing rate of 20 per cent per annum in Delhi.

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