What springs to mind when you think of smog alerts? Perhaps the summer weather reports announcing ozone readings, or pictures of the London ‘pea-soupers’ in the 1950’s – or even the panic over smog in the run-up to the Olympic Games in Beijing.
Smog does fire the imagination – but what is it and what does it do?
What Is Smog?
The word ‘smog’ is probably an amalgamation between smoke and fog and first came into use in the 19th century when the Industrial Revolution saw a dramatic increase in the burning of fossil fuels and coal in particular.
London became famous for its thick yellow-black fogs which would settle, sometimes for days, in periods of damp, calm weather, when a lot of fires were burning. It eventually got so bad and resulted in so many deaths that Britain’s first Clean Air Act was introduced in 1956.
Today, we don’t experience thick, visible smogs in quite the same way, because the pollutants that caused them – mainly a mixture of smoke and sulphur dioxide – are not used as much in the same context. However, we now have a more ‘dangerous’ condition in that the chemicals that cause smog today are far less visible.
This type of smog is generally known as photochemical smog or ‘summer smog’.
Components Of Summer Smog
The main cause of smog today is pollutants from traffic emissions, notably, hydrocarbons, PM10s (tiny particles less than 10 micrometres across), nitrogen dioxide and ozone. It is known as summer smog because it mainly occurs in hot weather conditions and when wind speeds are low.
PM10’s are so tiny that they are able to freely enter the airways, causing irritation and coughing, and can have extremely detrimental effects on people with bronchial or asthmatic tendencies.
Nitrogen dioxide is a strong pollutant and can cause chest pains and shortness of breath.
Ozone is a thick, bluish gas which, when found in the stratosphere above the Earth, forms a natural, protective layer between us and the effects of ultraviolet radiation from the sun. This is when the ozone layer is a good thing, and its disappearance a bad thing.
However, when ozone occurs at ground level, within our atmosphere, it is very harmful and can cause irreparable damage to the lungs. Ozone is produced when the sun reacts with volatile organic compounds (VOCs) in the presence of nitrogen dioxide.
What Effects Does Smog Have?
Because the effects of photochemical smog cannot always be easily seen, people tend to feel safer. However, the effects to health can still be tremendously damaging and is a growing problem.
Smog can trigger asthma attacks, and bronchial coughs in those who suffer from them. It can also cause hay fever-type symptoms such as runny eyes, itchy, irritated airways, coughing, sneezing, and headaches.
Ozone in particular can affect even very fit people who may experience tightness in the chest and lungs and some coughing and during episodes of high summer smog, there are many deaths directly attributable to this type of pollution.
Smog pollution also has an impact on plants. It is known to impair their ability to store or produce food and reduces their resistance to insect damage and disease. In fact the Nicotiana plant is particularly sensitive and is used to help monitor ozone levels.
Smog Alerts
In 1989 the government’s department of the environment began collating information on any ozone ‘episodes’ on a daily basis, fed to them from monitoring sites across Britain and in more recent years, air quality has begun to be reported as part of our weather forecasts.
Ozone data is made available each day to the Met Office which forecasters can decide to use to announce smog alerts if necessary.
However, many clean air lobbyists feel that air quality forecasts should be made available to everyone each day and that the current system doesn’t go far enough given the impacts to health the environment.
What can you do to help?
To help cut down pollution and photochemical smog through traffic emissions:
- Use your car less, and if possible not at all
- Switch off your engine when at traffic lights or in a traffic jam
- Avoid over-filling your tank when re-fuelling due to spillage
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