Emissions – What Goes in Must Come Out

Cars emit a complex cocktail of exhaust gases, many of which have harmful effects on both our bodies and the planet. Below are listed some of the major pollutants, along with some of their harmful effects.

Benzene (C6H6)

This naturally occurring hydrocarbon is found in crude oil, and therefore petrol, but is also produced during its refinement and combustion. Although typical atmospheric levels of Benzene are thought not to be harmful, benzene is a carcinogenic substance, and high levels of inhalation can carry severe penalties to human health.

Cadmium (Cd)

This metal naturally occurs in the Earth’s crust, and is released into the air in the form of various cadmium compounds on combustion of petrol and other fossil fuels. Cadmium oxide, one of the main by-products of combustion, is damaging to the lungs and kidneys on inhalation or ingestion, and is thought to be carcinogenic.

Carbon Dioxide (CO2)

Although CO2 is not a health damaging gas at normal atmospheric concentrations, it is the principal driver of climate change today, and thus, arguably the most dangerous pollutant for mankind today.

Did you know, for example, that a 6,000 mile journey travelled by car produces roughly its own weight in CO2? Transportation is the fastest growing source of CO2 emissions, with road transport accounting for about 25% of Britain’s emissions. The main way to cut these emissions is through reducing our use of fuel, and this can be done by (a) driving less, and (b) using more fuel-efficient cars. You can also help offset the emissions you do create by making your driving carbon neutral. For more information, call the ETA on 0800 212 810, or view the link on Climate Neutral.

Carbon Monoxide (CO)

This is a toxic, colourless and odourless gas, produced by the incomplete burning fossil fuels such as coal, oil, petrol and gas. In Britain, road traffic is responsible for over 70% of CO emissions. CO reduces the oxygen carrying capacity of the blood, interfering with the transport of oxygen from the lungs to the tissues (including the brain). It can cause headaches, nausea, fatigue, and at high concentrations, coma and death.

CO also adds to ground level ozone concentrations, combining with other pollutants to form photochemical smog, and is one of the minor anthropogenic gases contributing to climate change.

Nitrogen Oxides (NOx)

There are a number of nitrogen oxides, all of which are produced on combustion of fossil fuels. Not only do they aggravate asthmatic conditions, and react with oxygen in the air to form the irritant ozone, but they are also one of the key causal agents of acid rain. On reacting with atmospheric moisture, they acidify it, and this moisture, when it falls as rain inhibits the growth of plants, is damaging to freshwater and soil life, and is damaging to buildings.

Nitrogen oxides also contribute to photochemical smog. They irritate lungs, and increase susceptibility to viral infections. In Britain, 44% of NOx emissions come from road vehicles.


Diesel engines emit particulates (or soot), which are increasingly being linked with asthma. Although car manufacturers are attempting to make these particulates smaller (as is now legally required), these micro particulates now penetrate even further into the lungs resulting in less obvious, but longer-term damage.

Some estimates have suggested that particulates are responsible for up to 10,000 premature deaths per year in the UK alone. What’s more, 25% of particulates come from road transport.

The black, smoky exhaust of a badly maintained diesel vehicle contains dangerously high levels of soot and should be reported to the Smoky Vehicle hotline on 020 8665 0885.

Sulphur Dioxide (SO2)

This is a colourless gas, which smells like burnt matches, and is emitted by both petrol and diesel engines. Along with Nitrogen oxides, SO2 contributes to acid rain. The gas can also cause breathing problems, aggravate asthma, and worsen both respiratory and cardiovascular disease. It also brings about the formation of acid aerosols, which as well as being highly detrimental to human health, contribute to climate change.