Kolkata’s polluted air

Kolkata’s air pollution, as reported by WHO and UNEP (United Nations Environment Program) has assumed gruesome proportions and the city’s pollution level is next to Delhi’s. Following the apex court’s stricture, Delhi has adopted certain stern measures, and these include the use of CNG and the planting of more trees. Virtually nothing has been done in Kolkata.

Kolkata’s polluted air

Representational Image. (Photo: IANS)

The National Green Tribunal (NGT) has imposed a penalty of Rs 5 crore on the West Bengal government for its indifference towards air pollution. It is deplorable that the state has completely failed to honour the NGT’s directive that was advanced two years ago. The state’s Chief Secretary has been ordered to appear before the tribunal with a comprehensive report on the action taken so far towards mitigating the toxic air of the twin cities of Howrah and Kolkata.

It is surprising that no data is available on the number of Bharat Stage (BS) II and III compliant vehicles that are entering the city. Equally stern is the NGT’s warning that officials responsible for non-compliance should be put behind bars . The tribunal has also observed that “air pollution is the primary responsibility of the Pollution Control Board, but it is silent”.

The quality of ambient air in Kolkata has assumed alarming proportions and its pollution level is far more detrimental to health in comparison to Delhi. This estimate was furnished by the US embassy last January. The air pollution data, as furnished the US embassy, can differ from that of the West Bengal Pollution Control Board (WBPCB) and such variations are not unlikely for a variety of reasons.


Chiefly, these relate to the technique adopted, the quality of high volume air sampler equipment, the chromatograph attenuator adjustment, chemicals used, sensors and auto analysis of ambient air quality procedures. But this does not in any way establish that the reports forwarded by the US embassy are absolutely wrong. As a matter of fact, the statistics furnished by the WBPCB clearly state that the particulate matter in Kolkata on certain days is much higher than in Delhi. It is in fact extremely poor, as per the guidelines framed by the World Health Organization (WHO).

The Green Bench of Calcutta High Court had directed that no fuel, be it petrol or diesel will be given to any vehicles of the city unless they furnish the pollution control certificates (PUC). The Bench also raised a pertinent question as to why compressed natural gas (CNG) is not used in Kolkata, unlike in other cities. It criticised the authorities for their negligent nonchalance.

Kolkata’s air pollution, as reported by WHO and UNEP (United Nations Environment Program) has assumed gruesome proportions and the city’s pollution level is next to Delhi’s. Following the apex court’s stricture, Delhi has adopted certain stern measures, and these include the use of CNG and the planting of more trees. Virtually nothing has been done in Kolkata. The air we breathe in the city is poisoned with anthropogenic and natural emissions. However, air pollution is not a new problem. As long as man has lived in cities, he has developed a propensity to pollute the air. It is a problem of the ever-expanding technological society.

Most artificial impurities are injected into the atmosphere at or near the earth’s surface. Therefore, it is the scope and severity that is critical about air pollution. For most pollutants, the troposphere cleanses itself within a very short period of time because of the so called “vertical mixing tendency”. The rainfall also helps remove the impurities to a certain extent, but acid rain damages the environment and this is now a matter of grave concern.

Therefore, any substance that is not part of the air’s gaseous make-up is regarded as a pollutant. “Particulate Matter pollution” consists of materials that are directly emitted to the air or results from the transformation of gaseous pollutants. They come from natural sources or by human activities that are anthropogenic in character.

Airborne suspended particulate matter (SPM), respiratory particulate matter (RPM) and contaminant gases like volatile organic matter exist in the atmosphere in various degrees. The size of PM is extremely important in order to understand their impact on the human body and absorption potential in the throat and lungs.PM larger than10 micrometers in diameter are generally trapped in the nose and throat and never reaches the lungs.

On the other hand, particles smaller than 2.5 micrometers in diameter reach the bronchial tubes and can enter the deepest portions of the lungs. In Kolkata, air pollutants exist in gaseous or particulate form. Their concentrations are expressed most commonly either in microgram per cubic meter (gram to the power-3 of air) or as volume mixing ratio (1 ppb =10 to the power-9 ) which are diverse in character.

Toxicological, clinical and epidemiological studies have revealed the danger of PM inhalation. This can aggravate the severity of chronic lung diseases, inflammation, irritation of lungs, increase susceptibility to viral and bacterial pathogens, changes of blood chemistry, causing carcinoma and heart attacks.

Air pollution is not confined to a particular territory but is a trans-boundary phenomenon. In major urban cities of India, the quality of air has been deteriorating rapidly over the past two decades. The problem is particularly acute in Kolkata and its suburbs where the air is unclean according to standards fixed by the World Health Organization.

The city’s ever-increasing population, expected to be around 15 million by 2020, is posing a serious problem. Emission from vehicles has been identified as the major source of pollution in the Kolkata metropolitan region. It is responsible for nearly 60 per cent of the city’s total pollution level. The situation is appalling owing to the increasing number of vehicles and the limited space for their movement.

Domestic consumption of fossil fuels, sometimes out in the open and pollutants from small industries and godowns are further accentuating the problem. The pollutants vary from one place to another. Its intensity is the highest in the heart of the city. The common air pollutants in Kolkata are: sulphur dioxide, oxides of nitrogen, carbon monoxide, hydrocarbons, heavy metals like lead, and traces of dangerous carcinogenic polynuclear aromatic hydrocarbons (PAH).

In order to minimise the effect of air pollution and make the city a better place to live, work and invest in, the British Overseas Development Administration has put forward certain recommendations, called the Calcutta Environment Management Strategy and Action Plan (CEMSAP) about two decades ago. It has identified auto-emissions from the vehicles of outmoded technologies as solely responsible for environmental hazards.

The CEMSAP has also pointed out that the 24-hour average concentration of SPM, sulphur dioxide, nitrogen oxides, carbon monoxide and hydrocarbons in some places of Kolkata in their maximum level are far above the limits of the Central and State Pollution Control Boards. The air pollution index (API), according to CEMSAP, is maximum at the Howrah Bridge approach, followed by the BBD Bag area. The CEMSAP envisaged that auto-emission control, air quality monitoring and dissemination are inter-related.

In its consolidation phase document, CEMSAP has put forward its proposal for effective and meaningful implementation. The roadside air quality is far worse than the air quality standards for all pollutants. It is unfortunate that during the 34- year rule, the CPI-M led Left Front government virtually did nothing tangible to curb the air pollution problem in Kolkata and its adjoining areas including the district headquarters. The menace is horrendous in the headquarters of Nadia, Hooghly, and Burdwan districts.

The poor are acutely affected by pollution. The pavement dwellers, underprivileged and vulnerable groups are exposed to direct health hazards. In addition, the heavy air pollution leads to higher rates of mortality and morbidity. Lead petrol has been banned in most developed countries. But unleaded petrol has other disadvantages which need special attention.

Lead-free petrol releases a higher level of aromatic organic compounds and a high concentration of benzene which is known to be potentially carcinogenic. According to WHO, the risk of cancer is substantial. Suitable measures need to be taken immediately to eliminate the emission of toxic benzene into the air. Investigation of the presence of ultrafine particles (UFP) and nano particlees (NP) is absolutely imperative in the city.

Given the horrifying level of air pollution in Kolkata, how is it that millions manage to survive? One probable explanation is that the ambient air pollutants are shared by millions of people and they act as biological filters. The body doesn’t immediately suffer any symptoms of danger, but they arise unfortunately after a prolonged period of time.

As the pollutants are chiefly the outcome of auto-emissions, the entire auto-emission regulatory process needs to be revamped immediately. Reduction of vehicular emissions through continuous check, strict enforcement of the law and periodical survey of the emission control equipment are absolutely necessary. The air quality monitoring process should be strengthened.

The writer, a former Reader in Chemistry, Presidency College, Kolkata, was associated with UGC and UNICEF.