What caused air pollution in New Delhi? Sydney experts respond

6 November 2019
On Sunday, air pollution in New Delhi, India reached its worst levels for the year, with authorities declaring a public health emergency and ordering the closure of schools. Experts discuss the causes of the air pollution and the significant health impacts.

Public health researchers from the University of Sydney respond to reports air pollution in Delhi has reached toxic levels, prompting concerns from health authorities.

Air pollution the greatest environmental threat to human health

Professor Guy Marks is an Honorary Professor at the University of Sydney and was in India in November for the World Lung Health Conference of the International Union Against Tuberculosis and Lung Disease.

“I have witnessed, first-hand, the dreadful air pollution event affecting Delhi at the moment. Air pollution is the greatest environmental threat to human health. There were an estimated 4.9 million deaths globally attributable to air pollution in 2017, 1.24 million of which were in India.

“It is a global emergency that we need to tackle. It causes illness and death due to heart attacks, strokes, pneumonia, asthma and other lung disease, and, in the longer term, cancer. 

“The solution requires multi-sectoral approaches involving governments, the private sector and individuals.”


The acute respiratory and eye symptoms that many people will experience are only just the tip of the iceberg.
Associate Professor Camille Raynes-Greenow

‘Eye burning’ smog the ‘tip of the iceberg’

Associate Professor Camille Raynes-Greenow  is a maternal and child health expert at the University of Sydney School of Public Health.

“Delhi and India more broadly are at the crossroads of a major industrial transition where industry without regard for environmental control continues to pollute, at the same time traditional farming practices continue. Combined, this creates exceedingly high air pollution.

“Pregnant women and children are also extremely vulnerable to the poor air quality in Delhi.  The acute respiratory and eye symptoms that many people will experience are only just the tip of the iceberg that will also impact the developing fetus and small children.” 

Crop residue likely main cause of air pollution

Geoff Morgan is an Associate Professor of Environmental Health at the University of Sydney’s School of Public Health.

“A major component of the air pollution in the current incident in Delhi is related to crop residue or “stubble”, burning in the regions surrounding the city.  Burning is used to clear the fields in preparation for the next seasons planting. 

“These extreme episodes of air pollution highlight the magnitude of the health impacts due to air pollution in cities throughout India and in low / middle income countries around the world. 

“However, it is important to understand that these cities generally have high levels of air pollution with substantial heath impacts. 

“While it is important that policies be put in place to reduce the impacts of smoke from agricultural burning, it is also essential to develop effective strategies to reduce everyday air pollution emissions from the broad range of urban sources such as coal fired power plants, motor vehicles and industry.”

Air quality symptomatic of demand for energy

Dr Ivan Hanigan is a research fellow with the University of Sydney’s Rural Clinical School

“Unfortunately, such extreme levels of air pollution are symptomatic of the modern human's demand for energy derived from burning fossil fuels and other carbon-based fuels such as wood and cow dung, two very common sources of energy in India. 

“The short-term impact on air pollution such as small airborne particles and toxic gases is of substantial public health concern, even at the low levels we find in Australia.

“In Australia we have much lower levels than in Delhi, but our studies show that there appears to be no safe lower threshold of exposure to small airborne particles and there is likely premature mortality and lost life expectancy in Australia.

“There are also very worrying long-term impacts of the large-scale environmental and climatic changes associated with the modern human's high consumption phase of our evolutionary ecological history, especially the enhanced green-house effect and global heating induced by the emission of green-house gases from environmentally damaging technologies.”


Sitou Sally

Higher degree research student

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