金奈的空气质量

What is the current air quality in Chennai?

Chennai is the large Indian formerly known as Madras. It is the capital city of the Tamil Nadu state and is situated on the Bay of Bengal. The city and surrounding land rank as the 36^th largest urban area population in the entire world. There are three rivers that flow through the city and they are all heavily polluted with factory waste amongst other things. The Cooum river is so polluted that it looked upon as one of the city’s eyesores. When considering the world’s dirtiest cities, Chennai is ranked at 320 US AQI with an average PM2.5 measurement of 34.6 µg/m³ in 2019. This figure reflects the improvement to the air quality in Chennai since 2017 when the average PM2.5 figure was 39.8 µg/m³. The 2018 average was 43.2 µg/m³. For seven months of the year, Chennai’s air quality is classed as being “Moderate” according to the World Health Organisation’s (WHO) guidelines. A further four month’s readings class it as being “Unhealthy for Sensitive” groups and during January 2019 the quality was classed as “Unhealthy”.

Where does the air pollution in Chennai originate?

As with other densely populated industrial mega-cities, most of the air pollution comes from the number of vehicles using its roads on a daily basis. Add to this the emissions from factories, of which there are many in and around the city. Emissions from the power stations in the suburbs of Ennire add large quantities of polluted air to the environment as does particulate matter generated through demolition and construction and poor quality roads that are unpaved, thus producing a lot of dust.

The burning of organic waste from crops is a large contributor to the poor quality of air in Chennai. Straw from the rice harvest and unwanted stems from sugar cane production cause what the locals call “Black Snow” because of the prolific way in which it falls.

Is air pollution in Chennai getting better or worse?

Due to the restrictions put into place to control the COVID 19 pandemic both air and noise pollution levels have dropped this year (2020). The State government imposed tight restrictions on the use of firecrackers which are traditionally set-off extensively during the Diwali festivities. The values of particulate matter PM2.5 and PM10, sulphur dioxide (SO₂) and nitrogen dioxide (NO₂) have been considerably lower this year. These were the findings of the monitoring stations based in Chennai when compared to figures from 2019. PM10 figures ranged from 52-111 µg/m³ (micrograms per cubic metre) during the Diwali festivities, which exceeded the standards of 100 µg/m³, as recommended by the Tamil Nadu Pollution Control Board (TNPCB). The PM2.5 readings ranged from 32-59 µg/m³ and were within the recommended level of 60 µg/m³. The gaseous pollutants of sulphur dioxide (SO₂) and nitrogen dioxide (NO₂) were also found to be within the recommended levels. The air quality index in some of the largest city areas was found to range from “Good”, “Satisfactory” or “Moderate” in Nungambakkam, Sowcarpet and Tiruvallikeni, respectively.

What can be done to improve the air quality in Chennai?

Chennai has a very small number of Continuous Ambient Air Quality Monitoring Stations (CAAQMS). There are just 3 stations which are controlled by the Central Pollution Control Board (CPCB) and a further five which have yet to become fully operational. Eight is considered to be far too few, considering the size of Chennai. It has been recommended to install and operate at least another 30 stations.

The reduction in the number of vehicles using the road network is one way to reduce pollution but a difficult one to achieve. Whilst public transport is available, many commuters still prefer the convenience of having the use of their personal vehicle. The government could do more to encourage the drivers to leave the car at home on certain days of the week. In certain Indian cities the “odd/even” rule applies. This means that if your registration plate ends in an odd or even number, then on certain specified days it is prohibited from travelling within the city limits.

Some local governments are gradually replacing public buses with ones that run on cleaner fuel or by electricity.

The construction industry is supposed to shield the dust created through demolition and spray water on the ground to stop the dust blowing into the surrounding areas.

Factories should be encouraged to monitor their emissions and use a filtration system to capture some of the pollutants before they enter the environment.

What are the health effects through breathing polluted air in Chennai?

Air pollution is the third largest cause of premature deaths, in India, ranking slightly above smoking. On a global scale, it is proved that more people die from diseases directly linked to air pollution than from traffic accidents and malaria. In 2017 over 1.2 million deaths were attributed to exposure to polluted air. According to a report by the State of Global Air (SOGA2019), the life expectancy of a South Asian child born in 2020 will be shortened by 2 and a half years. This compares to a global figure of 20 months.

The database compiled over several years by the World Health Organisation (WHO) listed India’s tier one and tier two cities as some of the worst polluted cities in the world. In 2018, it was discovered that out of 15 most polluted cities in the world, 14 of them were in India. Another report, commissioned by The Lancet revealed that India ranked in the first place when looking at premature deaths and mortality related to long-term exposure to poor air quality.

When the level of air quality in Chennai falls into the “Unhealthy” category, people suffering from respiratory issues, children under 14 years old, senior citizens and those who work outdoors are warned to limit their exposure where possible. If it is impossible to avoid, then a good quality mask should be worn at all times. These people from the sensitive group should take exercise in an indoor environment with air-conditioning, if possible. They are also advised to notice symptoms such as coughing and shortness of breath.