London and the south-east are struggling with high levels of pollution and toxic air currently, and the problem is so bad in the capital that mayor Sadiq Khan has tweeted: "The shocking and illegal state of London's toxic air means I've had to trigger a high air pollution alert today."

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He warned people with health conditions to carry their medication and added: "Walk, cycle or use public transport if you're able to, to help us cut emissions & pollution."

But what does this mean for your health, and what can be done about it?

Air pollution – the health impacts

Short-term, and if you’re healthy and only exposed to moderate levels of air pollution, there are often very few health ramifications.

In fact, you may not even notice smog and pollution levels. However, long-term exposure to high levels of pollution is a different matter, and can affect the respiratory and inflammatory systems, and exacerbate heart and lung problems if you already have them. Air pollution has also been linked with certain cancers, particularly lung cancer.

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How to stay safe from polluted air

Defra (Department for Environment Food and Rural Affairs) advises, when air pollution is in the “very high” bracket, as it is at the moment, that:

“Adults and children with lung problems, adults with heart problems, and older people, should avoid strenuous physical activity,” and note that “people with asthma may find they need to use their reliever inhaler more often”.

For the general population, regardless of pre-existing health conditions they recommend that people “reduce physical exertion, particularly outdoors, especially if you experience symptoms such as a cough or sore throat”.

So what more can you do?

- Avoid running/jogging/cycling outdoors

- Stay inside if you are suffering with a cough, sore throat, sore eyes and avoid “strenuous physical exertion”, even indoors

- Carry an inhaler if you require one

- Work at home if possible

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How can you help combat air pollution?

- Use public transport to reduce emissions and pollution produced by cars on the road

- If you really do need to drive, do not leave your engine running. Turn the car off if you are stopping for more than a minute, and try and avoid multiple trips

- Decrease your energy usage e.g. turn off lights, use green energy providers, insulate your home rather than relying on heating, recycle

- Reduce food miles by buying locally grown foods, or grow your own