Poison in the air: Invisible pollutants are causing visible health damage

The winter smog in north India is a grim reminder of its toxic air quality. Southern India, where there is little drop in temperature in winters, wakes up to no such alarm but there is a cause for concern.

While particulate matter (PM 2.5 and 10) remains the primary pollutant across the country, the risk that pollutants such as nitrogen oxides (NOx), sulphur oxides (Sox), volatile organic compounds (VOCs) and ozone pose is increasingly being recognised.

Before 2017, NOx and SOx monitoring was patchy. It was only last year that a clearer picture began to emerge though a comprehensive analysis is still awaited.

In Bengaluru, along with particulate matter, nitrogen dioxide and ozone were major pollutants for almost half of the days in February 2016, Central Pollution Control Board (CPCB) data shows.

In Chennai, carbon monoxide and ozone were primary pollutants for a third of the days that month.

The toxic cocktail

Nitrogen oxides (NOx)
A group of highly reactive gases, including nitrogen dioxide (NO2), which forms a reddish brown haze

Source: Fuel combustion (electric utilities, big industrial boilers, vehicles) and wood burning

Health impact: Inflammation of the airways, lung tissue damage, reduced lung capacity, skin cancer, nerve damage

Sulphur dioxide (SO2)
Colourless gas that reacts with water vapour to form acid and interacts with other gases and particles in the air

Source: Fuel combustion (especially high-sulphur coal), electric utilities and industrial processes

Health impact: Coughing, wheezing, shortness of breath, or a tight feeling around the chest within 10-15 minutes of exposure

Ozone (O3)
Pale blue gas with a distinctively pungent smell, which is a secondary pollutant formed when other pollutants react under sunlight

Source: Areas where scavenging takes place

Health impact: Watery eyes, scratchy throat, dry cough, respiratory tract infections, chest tightness, painful deep breath, asthma, reduced lung capacity, chronic obstructive pulmonary disease, and even premature death

Volatile organic compounds
These are organic compounds such as benzene, toluene, ethylbenzene and xylene that easily become vapours or gases

Source: Incense sticks, polish and paint on walls and furniture, perfumes and deodorants and plastic items

Health impact: Persistent dry cough, irritable and watery eyes, itchy skin, rashes, fatigue, high blood pressure, artery blockage, lung damage

Exposure to pollutants such as NOx, SOx, carbon monoxide and VOCs such as benzene, toluene, ethylbenzene and xylene (also known as Btex) is detrimental to lung function. These cause restriction in the lung expansion and obstruct and narrow the airways.

Particulate matter levels, to a great extent, depend on the season and weather conditions, but the other pollutants are virtually perennial as their sources include thermal power plants, vehicles and industries.

There is growing evidence that even a short-term exposure has serious health impacts. Annual averages often cited to allay fears of poor air quality do not capture spikes and also the exposure of people who live or work close to the sources of pollution.

“Prolonged exposure can lead to fatal lung conditions such as chronic obstructive pulmonary disorder, which is a progressive lung disease that makes it hard to breathe, aplastic anaemia and several types of cancers as pollutants like ammonia, arsenic, benzene are known carcinogens,” said Dr Vikas Maurya, senior pulmonologist at Fortis in Delhi’s Shalimar Bagh.

NOx are a growing concern across Indian cities and is particularly worrying because it is a precursor to ozone formation that can trigger shortness of breath, respiratory distress, aggravate conditions such as asthma and damage lungs.

Read | Poison in the air: Not Delhi alone, pollution is a pan-India issue

New research has linked short-term exposure to ozone with mortality. According to an analysis by the Institute for Health Metrics and Evaluation’s Global Burden of Disease Project and the Health Effects Institute, India had the highest number of premature deaths, 254,000, linked to ozone pollution in 2015. The Indian government disputes the data.

SOx, NOx and VOCs are not just dangerous themselves, they also add to the particulate pollution because they generate particles through atmospheric reactions. The health impacts of dangerous levels of particulate pollution have been documented across India.

Most premature deaths in Mumbai and Delhi in the 1991-2015 period were caused by stroke (a medical condition that occurs when the blood supply to the brain is cut off) due to inhalation of ultrafine suspended particles, said a 2017 study by the Indian Institute of Technology-Bombay.

A limited study of 12 air samples in Chennai this winter – December 2017-January 2018 – found that levels of PM2.5 far exceeded the 24-hour national standard. Levels of some toxic metals such as manganese and lead, too, had risen significantly compared to April 2017, the study Healthy Energy Initiative–India, an NGO, found.

There is no standard for manganese and lead is not measured by the CPCB monitors. Both lead and manganese are neurotoxicants that can cause confusion, fatigue, irritability and other behavioural changes.

“The Tamil Nadu Pollution Control Board has a plan to fight the menace of pollution and it is now taking more cognisance of findings of environmental activist bodies on polluting industries and taking action in cities,” said environmental activist Nityanand Jayaraman. “But clearly, these are not enough as the problem is so huge that it requires efforts on a war footing.”

The percentage of children with asthma in Bengaluru increased from 9% in 1979 to 29.5% in 1999, according to a study cited by the Supreme Court in 2003. The study noted that there was a corresponding rise in vehicles from 150,000 to 1.2 million.

A recent survey found alarming instantaneous levels of particulate matter exposure near the city’s key road junctions.

“There is a high incidence of heart attacks among the auto and cab drivers in the city as they spend long hours in slow-moving traffic,” Rahul Patil, a cardiologist at the city’s Jayadeva Hospital, said.

Particulate pollution gets absorbed into the bloodstream within a few minutes and was responsible for blocking arteries, he said. “Bengalureans should... not walk and cycle on or near busy roads as the benefits might not outweigh the risks,” the doctor said.

(With inputs from Badri Chatterjee in Mumbai and KV Lakshmana in Chennai)