Explained: What is responsible for most air pollution deaths?

New Delhi, Mar 11: Exposure to air pollution has been linked to 100,000 excess premature deaths in the Indian cities of Mumbai, Bangalore, Kolkata, Hyderabad, Chennai, Surat, Pune and Ahmedabad between 2005 and 2018, according to a study.

The researchers found significant annual increases in pollutants directly hazardous to health of up to 14 per cent for nitrogen dioxide (NO2) and up to 8 per cent for fine particles (PM2.5).

They also found increase in the level of up to 12 per cent for ammonia and up to 11 per cent for reactive volatile organic compounds.

The team, including researchers from the Harvard University in the US, attributed this rapid degradation in air quality to emerging industries and residential sources like road traffic, waste burning, and widespread use of charcoal and fuelwood.

Death toll from air pollution
The pollutant that is responsible for most air pollution deaths is particulate matter
There are a number of pollutants that have negative health impacts. But there is one that all studies focus on: particulate matter.

Particulate matter - often abbreviated as PM - is everything in the air that is not a gas. These are very small particles made up of sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water that are suspended in the air that we breathe.

Particles with a diameter of 10 micrometers (10 millionth of a metre) or less can enter deep inside a person's lungs. But the most health-damaging particles are even smaller. Those with a diameter of 2.5 micrometers or less - abbreviated as PM2.5 - can penetrate the lung barrier and enter a person's blood system. These are extremely fine particles: 2.5 micrometers is about one-thirtieth of the diameter of a human hair.1

All studies of the mortality impacts of air pollution consider our exposure to particulate matter. Some studies also consider the impact of ground-level ozone. The death toll from ozone is much lower than that of PM, but it is still considerable: it's responsible for hundreds of thousands of premature deaths every year. Other air pollutants are rarely considered in global studies.

It should be noted that the number of deaths attributed to outdoor air pollution ranges from 3 million to almost 9 million per year. In addition, a large number of deaths are attributed to indoor air pollution.