Road traffic is one of the major causes of NO2, which is largely caused by burning fuel.
If you’re regularly exposed to high concentrations of NO2, it may lead to asthma or greater risk of respiratory problems. It can also make existing breathing problems worse and cause coughing and wheezing.
Children and older people are particularly vulnerable to the effects.
High levels of NO2 can also affect the environment, damaging vegetation and reducing plant growth.
Carbon monoxide (CO) is a colourless, odourless poisonous gas. Outdoors, it is largely produced by road traffic and machinery burning fossil fuels, particularly petrol.
This gas reduces the amount of oxygen circulating in your bloodstream to critical organs like the brain and the heart.
Very high levels of CO are not likely to occur outdoors. But when it does, it can cause real problems for people with heart disease, who already have difficulty getting enough oxygen to their heart.
‘Good’ ozone in the stratosphere shields us from the sun’s ultra violet rays.
But at ground level, ozone is a harmful pollutant and one of the main ingredients of ‘smog’.
It’s created when pollutants from cars and other industrial combustion sources (like power plants or factories) have a chemical reaction in the presence of sunlight.
That means unhealthy levels are more likely to happen on hot, sunny days. Ozone can be carried a long way by wind, so can affect rural as well as urban areas.
It irritates the lungs, increasing the symptoms of people suffering from asthma and lung diseases.
It can also affect sensitive vegetation and ecosystems, by slowing plant growth and causing risk of disease or damage from insects or bad weather.
The main source of sulphur dioxide (SO2) in the UK is power stations burning fossil fuels such as coal and heavy oils. Widespread home use of coal burning stoves can also lead to high levels.
Even moderate concentrations of SO2 can cause problems for asthmatics. At high levels it can cause tightness in the chest and coughing, and asthmatics may need medical assistance.
Sulphur dioxide pollution is considered more harmful when particulate and other pollution concentrations are high.
In nature, SO2 can contribute to acid rain, damaging sensitive ecosystems, plant life and decreasing growth.
Fine particles are also referred to as ‘particulates’ and are mainly caused by road traffic and burning fuel.
They are more commonly known to us as dust, dirt, soot, or smoke. In very polluted areas you may see particles as smog or ‘haze’.
Particles are measured in ‘micrometre’ (one-thousandth of a millimetre) size fractions. PM10 and smaller (or ‘finer’) particles like PM2.5 are a particular problem for our health and the environment.
That’s because you can breathe fine particles deep into your lungs, causing inflammation and making heart and lung conditions worse. Some fine particles carry cancer-causing substances and may even get into your bloodstream.
As you’d expect, particles can aggravate asthma, causing problems like coughing and difficulty breathing. Studies have also shown links to premature death in people with heart of lung disease.
Particles also cause environmental damage by contributing to acid rain, damaging rivers, ponds and lakes and affecting crops and ecosystems.
To find out more about these and other harmful pollutants, visit the Department for Environment, Food and Rural Affairs website.