Videographic on air pollution, as COVID-19 has made air pollution a top global concern.
Air pollution causes some seven million premature deaths each year, of which 600,000 are children under 15.
Many types of pollutants exist. The most harmful are microscopic particles in the air.
These are produced by farming, industrial activity, wood burners and and road transport. The very finest particles — released by fuels like diesel — are the most dangerous.
Smaller and often toxic, they penetrate deeper into the respiratory system and can enter the blood stream.
Ozone is also a pollutant. In the stratosphere it exists naturally but at ground level it’s a health hazard.
It is created by reactions between nitrogen oxides and volatile organic compounds in the presence of sunlight.
These compounds come especially from exhaust fumes.
Ozone can damage vegetation and causes stress for people with asthma and respiratory illness.
Another gas, nitrogen oxide, forms quickly in high-temperature combustion — in vehicle engines and power plants.
It reacts with moisture in the air to form a vapour of nitric acid, which can worsen bronchitis and other health problems.
Pollutants such as sulphur dioxide, benzene, ammonia, and toxic metals like lead and cadmium can also affect the lungs, eyes, digestive tract or nervous system.