People across India are exposed to high levels of pollution, both in urban and rural areas. According to a recent international study (Brauer et al, 2015), less than 1% of the Indian population lives in areas that meet the World Health Organisation’s air quality guideline (i.e. PM2.5 less than 10 µg/cubic metres).
Air pollution has become a health hazard and features among the top health risks that contributes to mortality and morbidity in India.
As the central and state governments announce initiatives for pollution control, it is important to consider other sources that also contribute to air pollution. Beyond vehicles, sources of particulate matter include dust (construction dust, non-exhaust vehicular emissions- tyre and brake wear, etc.), waste burning, coal combustion, biomass (firewood, cow dung cakes etc.), brick kilns and industrial activities among others. Activities such as festive fireworks and wood burning (particularly around Diwali, Lohri) and funeral pyres can also lead to bad quality air.
Some sources can become important in certain seasons for eg, burning firewood and waste in open for heating purposes in winter, or the dust in summer. The problem is further compounded by the fact that pollution doesn’t respect geographical borders, emissions in other states impact the quality of air in Delhi and vice versa. As a result, farmers burning agricultural residues in Punjab can affect air pollution levels in the city, as can dust intrusion from the Thar Desert.
Other Sources of Pollution Shouldn’t Be Ignored
- As the Central and state governments announce initiatives for air pollution control, it is important to take into account other pollution sources.
- Dust from road and construction is harmful, hence, exposure to it must be reduced.
- Previous research has revealed road dust in Delhi is high in concentration of metals such as copper, zinc, cadmium and lead.
- Restricting the number of cars on the road is an important step, and represents willingness on part of the government to act on the issue.
- Other initiatives, such as mechanised cleaning of roads, coupled with odd-even restriction will help improve Delhi’s air quality.
Dangers of Dust Pollution
Imagine burning incense in a room, but providing no outlet (windows, fans etc.) vs burning incense in a room with open windows. The same is true for air pollution. When temperatures are higher, and wind speeds are higher, pollution doesn’t remain in one place, and conversely, lower wind speeds result in pollution build-up. Particles are ultimately made up of chemicals, and these chemicals continue to react with each other after they are released into the atmosphere, often leading to new particles (secondary air pollution), which is another contributor to overall pollution levels, albeit more difficult to measure directly.
When thinking about dust, it is important to segregate between crustal soil (often not harmful to human health unless in cases on very high exposure) and road dust, construction dust or fly ash, which can be enriched in chemical species that are harmful for humans. Some of my previous research on road dust in Delhi found high concentrations of heavy metals such as copper, zinc, cadmium and lead and this dust can be re-suspended every time we drive, walk or cycle and we end up inhaling these particles.
While most scientific studies identify dust as a source of air pollution, classification of the source is often vague, and it is difficult to assess the potential for health effects. It should be noted, however, that dust is more relevant in case of coarse particulate matter (PM10) while any activity where material is burnt (wood burning, waste burning, etc.) releases smaller particles (PM2.5).
More Needs to be Done
Delhi government’s recent decision to introduce odd-even restrictions has received mixed reactions. Ever since the scheme was introduced on January 1, different reports have claimed reduction or no effect on air pollution levels. Restricting the number of cars on the road is an important step forward in that it represents willingness on part of the government to act on the issue.
Several exceptions, and the fact that the policy does not apply to two-wheelers, could have contributed to a lack of visible effect on air pollution reduction. As I mentioned earlier, weather can also play an important role, and since January 1, wind conditions have often been reported as calm (again, think of a room with burning incense but no outlet).
However, much more is needed if the city has to become more breathable, and liveable. Traffic jams are an everyday occurrence in Delhi, and the stop- and-go traffic not only increases tailpipe emissions but also causes more tyre and brake wear, releasing metallic particles into the air.
Ensuring A Healthy Future
Restriction on movement of cars can help ease congestion and allow smooth flow of traffic, thus reducing emissions as well as human exposure to harmful pollutants in outdoor environments. Stricter controls at construction sites including use of water sprinklers, and use of low-sulphur fuel in equipment can help reduce construction emissions.
The good news is that the odd-even restrictions aren’t the only government policy that is currently underway to control air pollution. Several other initiatives have been announced including mechanised cleaning of roads (that would help control dust levels), restrictions on burning of waste materials, tyres and firewood; closure of the Badarpur power plant are in the works. Inclusion of control and mitigation measures for dust (from various sources) in the air quality action plans at city, state and national levels will help us improve the air quality and help provide a healthier future for the people. Additionally, it is important for us to continue characterisation and quantification of various source emissions that contribute to particulate pollution and devise methods to control such emissions.
Finally, while it is important to continue pollution control initiatives in New Delhi, it is equally important to turn our attention to other cities where pollution levels are equally bad, if not higher.
(Pallavi Pant is a researcher at the University of Massachusetts, Amherst (USA) and studies air pollution in India.)