The UK has suffered an unusually severe smog over the last two days. The as a result.
麻豆传媒 examines how dangerous the spike in pollution is, and what is going to happen to the UK鈥檚 air in the future.
See graph: 鈥�Is the UK鈥檚 air getting cleaner or dirtier?鈥�
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What has happened?
A mixture of particles from Europe and the Sahara desert shrouded England in smog yesterday, with London, parts of the south-east and the Midlands all affected.
In some places the severity of air pollution reached 9 or 10 on used by the UK鈥檚 Department for the Environment, Farming and Rural Affairs. The smog is expected to subside to very low levels by the end of the week.
How harmful is it going to be?
It is hard to say how many people will be harmed by the spike in pollution.
There are two types of particle that pose a threat to people鈥檚 health: those smaller than 10 micrometres, known as PM10, and those smaller than 2.5 micrometres across, or PM2.5.
The PM2.5 are more dangerous, says of King鈥檚 College London. 鈥淧M2.5 is small enough to get deep down into the respiratory tract and be absorbed.鈥� This can exacerbate asthma and other respiratory complaints, and is also linked to deaths from heart attacks.
Williams estimates that there are currently about 29,000 premature deaths a year in the UK because of high pollution levels. He says the main risk comes from sustained exposure in the long-term, not short-term spikes like this one. 鈥淚f the average doesn鈥檛 go down, the bulk of health implications won鈥檛 improve.鈥�
Is this normal for the UK?
Although the levels in London are well above the local average, this spike in pollutants is nothing out of the ordinary, says Williams. 鈥淲e have seen episodes like this before.鈥�
They are also not unusual by European standards, says Williams. 鈥淟evels are typical of a large European city like Rome or Paris.鈥�
People in other cities have it far worse on a regular basis. 鈥淥n a global scale London is actually relatively clean, with pollutant levels nowhere near those in Beijing or Delhi,鈥� says Williams.
The UK鈥檚 average air quality has actually improved since 2000. The proportion of the population exposed to harmful levels of PM2.5 鈥� defined by the World Health Organization as 鈥� has been falling (see 鈥�Is the UK鈥檚 air getting cleaner or dirtier?鈥�).
What鈥檚 going to happen in the future?
There is every chance that air quality in the UK will improve over the next 10 years, as most European states are working to reduce the amount of fossil fuels they burn.
The fly in the ointment is that climate change will also increase temperatures. This affects atmospheric chemistry, leading to more frequent summer smogs. 鈥淭here is a balance,鈥� says Williams. 鈥淚f emissions stay the same, summer smog will increase a lot because of temperatures rising.鈥� The question is whether Europe will cut its emissions enough to offset this.
The other issue is that Europe is getting ever more energy by burning biomass such as wood. This is encouraged because it limits climate change, but it has a downside. 鈥淚t actually emits large amounts of particles, which contribute to air pollution,鈥� says Williams. 鈥淓uropean countries in particular burn a lot of wood.鈥�
