Every year, a thick layer of smogA kind of toxic fog caused by high levels of air pollution. grips Delhi. On the worst days, schools and colleges close. Power stations must shut down. Those who can, stay at home.

Scientists have known for a long time that air pollution is bad for health, as tiny particles clog lungs. Asthma, cancer and heart disease are among the conditions on a grim list of diseases caused by smog. This June, experts warned air pollution in Delhi shortens life expectancy by as much as 10 years.

We are beginning to understand the effect of toxic air on the brain. A UK government research group found air pollution is "likely" to raise the risk of dementiaA syndrome associated with memory loss and other declining brain functions. . Over the course of a person's life, scientists say, pollutants enter their circulatory system and affect the blood flow to their brain.

This comes on top of a previous study proving chronicA condition which recurs over time, or lasts for several years. exposure to air pollution may cause a "steep reduction" in maths and language abilities. In extreme cases, this was equal to the loss of a year's worth of education. For British charity Medact, the findings are nothing short of "extremely worrying".

Today, up to 90% of the world's population is breathing air with unsafe levels of pollution.

Unicef has reported that around 4.5 million British children are exposed to dangerous levels of air pollution - which can impact brain and lung development. And the World Health Organisation estimates toxic air causes millions of premature deaths.

Figures show that 90% of these fatalities occur in middle or low-income countries. But there are also over 40 UK towns and cities with unsafe levels of pollution.

There are some ideas for solutions.

Architect Stefano Boer wants to cover buildings with trees and greenery, creating entire "forest cities" which would absorb carbon dioxide and harmful particulates.

Engineers in India hope they can convince farmers to give up setting their fields alight in favour of a new organic microbial spray that breaks down crop residue with a mixture of seven types of fungus.

Some have proposed a "smog allowance", which would force some companies to pay higher salaries to workers exposed to dirty air, incentivising businesses to clean up their acts. Meanwhile, cities like Oslo and Paris have experimented with simply banning cars from their city centres on certain days.

Yes: Humanity has an incredible capacity to solve problems. New and radical solutions, from giant "virtual chimneys" to microbial sprays, are being proposed by scientists almost every day.

No: The size of the problem is immense, and scientists cannot fix it alone. The answer is in politics, not science. Governments must work together with the people to stop the pollution.

Or... We know the root cause of this problem: our addiction to burning fossil fuels. It would be better for scientists to research more sustainable ways of living than jet engines to blow away toxic smog.