How smog and air pollution cause long-term health problems – DW – 11/22/2024

The 100 most polluted cities in the world are all in Asia. In November 2024, severe air pollution persisted in major cities in India, including New Delhi, and in parts of Pakistan. Local residents were advised to stay indoors and school and outdoor construction work was suspended as a result of the bouts of winter smog.

But air pollution is nothing new in the most populated and urbanized cities in the world. And exposure to polluted air can occur anywhere: whether a person is walking through a city full of factories, stuck in rush-hour traffic, or in a rural area that relies on wood fires for warmth.

However, for many people in the hardest-hit parts of the world, taking precautions to avoid poor air quality is easier said than done.

What causes air pollution and how does it become smog?

Smog is a portmanteau of “smoke” and “fog.” That should give you an indication of how this dirty chemical mist arises.

It forms when ground-level pollutants such as ozone, particulate matter, sulfates, nitrates and other toxic chemicals combine with fog under sunlight.

Why are smog and air pollution dangerous?

Smog and pollution are dangerous because they are very easily inhaled.

Combustion processes, whether in an industrial factory, your car engine, or your home’s wood-burning oven, release toxic gases into the atmosphere.

Often, within smoke and gas there are suspended microscopic particles that result from complex chemical reactions between the substances we burn.

The particles are labeled by size. For example:

• PM10 for particles from 2.5 to 10 micrometers
• PM2.5 for particles 2.5 micrometers or smaller
• PM0.1 for ultrafine particles less than 100 nanometers

These particles are tiny. For comparison, a human red blood cell would fit within the size range of PM10, as it is between 6 and 8 micrometers in diameter.

Bacteria, such as those that cause disease. E.coli, They are about 3 micrometers wide, so PM2.5 is even smaller than that.

As for ultrafine PM0.1, these particles are even smaller than the viruses that cause flu and HIV.

It is because of their microscopic size that inhaling a puff of these chemical particles (formed from toxic gases, heavy metals, and volatile organic compounds) can be easily absorbed into the bloodstream, where they can cause long-term damage.

What are the health effects of smog and air pollution?

Inhalation of particulate and gas pollutants has long been associated with poor health and a variety of diseases and disorders.

Short-term exposure can aggravate acute conditions, such as asthma and other respiratory problems and infections, and can affect lung function.

In the longer term, chronic diseases can occur, such as cancer, stroke, obstructive heart and lung diseases.

This can affect people of all ages, but children and people over 65 are particularly vulnerable.

In May 2024, a study of low emission zones in Germany They found that children who were exposed to clean air from conception to age one were less likely to need medication before age five.

“Being exposed to air pollution this early in life can have long-term effects as children grow,” said Hannah Klauber, the study’s lead researcher.

Previous studies have also shown that children who are exposed to pollution early in life do worse in school, earn lower test scores, and, on average, earn lower incomes as adults.

“We have shown in several studies that there are no safe levels of air pollutants,” Klauber told DW. “There are basically no safe levels of suspended particulate matter, so any increase in particulate matter in them produces adverse health effects.”

While Klauber’s study focused only on Germany, Klauber said he would expect to find similar results in other parts of the world as well.

How is air quality classified and why?

Air quality ratings are used to monitor the level of air pollution in an area.

These rating scales are typically developed by national governments, so standards may vary from country to country. But many are based on global recommendations of the World Health Organization.

Some countries and cities color code their quality ratings. For example, in the United States and India:

• Green is for good quality air.
• Yellow is for moderate contamination.
• Orange for poor air quality.
• Red indicates very poor air quality.

What can you do to protect yourself against smog?

There is little you can do to effectively protect yourself against smog if you find yourself in a situation where you can’t avoid it.

But in some cities with high pollution, such as New Delhi and Lahore, authorities impose restrictions on outdoor activities. That includes school closures, limits on driving cars and other vehicles and suspensions of outdoor work.

Cities prone to smog and high air pollution can also advise their residents to use filtration mechanisms whenever possible and reduce physical exertion.

Does school closure help reduce air pollution?

No, not according to Rajib Dasgupta, a professor of public health at Jawaharlal Nehru University in New Delhi. Dasgupta told DW that restrictions on outdoor activities or school closures are only temporary measures.

“It’s something that really can’t be managed through personal or household-level interventions. It’s something that has to involve state action and very broad multi-sectoral action,” Dasgupta said.

Measures are being taken around the world to impose stricter limits on air pollution. The European Union agreed to new rules in June 2024, and efforts are also underway in Asia to reduce air pollution in some of the hardest-hit places, such as Beijing, China.

Beijing authorities introduced a plan to electrify public transport services in 2013. This has achieved some significant reductions in smog and pollution, but its levels are still above government and global recommendations on air quality.

India has also enacted new clean air policies, but Dasgupta criticized the lack of progress: “States don’t seem to be able to act together, and it’s not because of a lack of money, but because of a lack of will.”

Edited by: Zulfikar Abbany

Select sources:

WHO Global Air Quality Guidelines (2021)

Study: Killing Prescriptions Softly, published by Klauber, Hannah, Felix Holub, Nicolas Koch, Nico Pestel, Nolan Ritter and Alexander Rohlf in the American Economic Journal, Economic Policy (2024) DOI: 10.1257/pol.20210729