Motor Vehicle Emissions

Motor traffic is a major source of air pollution in Australian cities. Little monitoring of typical motor exhaust emission pollutants has been conducted in Tasmania. Whilst it is unlikely that Tasmanian urban centres suffer from the levels of vehicle pollution experienced in larger Australian cities, we need to do what we can to minimise it.

What are the pollutants vehicles emit?

The main primary pollutants emitted include:

In addition, mixtures of these pollutants may produce ozone or photochemical smog when exposed to sunlight and are known as secondary pollutants.

Particulates

After domestic woodheaters, vehicles emissions are the second greatest contributors to particulate pollution in Tasmania. Out of all the different types of vehicles diesel vehicles can contribute up to 91% of the total particulate output.

Particulates not only come from the exhaust fumes of vehicles but also from the dust on the roads which is picked up and thrown into the air as vehicles pass over it. These types of particulates, however, are generally larger than those from exhaust fumes and fall out of the air fairly quickly. This is why actions to reduce particulate pollution from motor vehicles has focused on exhaust fumes.

Greenhouse Gases and Carbon Dioxide

Not only do vehicles cause localised air pollution, they are also responsible for a large proportion of our greenhouse gas emissions. Vehicles are responsible for about 25 per cent of Tasmania's total greenhouse gas emissions through emissions of carbon dioxide. Nitrogen oxides, volatile organic compounds and ozone in the lower atmosphere also add to the greenhouse effect, although they are not the major greenhouse gases.

Petrol cars emit about 2.3kg of carbon dioxide per litre of fuel burned, diesels emit about 2.8kg, and LPG cars emit 1.5kg. However, these figures don’t tell the full story. Diesel cars tend to go much further on a litre of fuel than petrol cars, so their overall carbon dioxide emissions per kilometre are lower. LPG cars do not go as far per litre, but on balance they emit less carbon dioxide per kilometre than petrol cars.

To understand just how much carbon dioxide is released from cars, 2.3 kilograms of carbon dioxide is released from the exhaust for every litre of petrol used by a car, then a 50-litre tank will release about 115 kg of carbon dioxide. Imagine how much carbon dioxide is released from the 245,000 cars in Tasmania every year!

Lead

Vehicles used to be a major source of lead in urban environment and concentration levels could get very high. The National Pollutant Inventory (NPI) results for 1999-2000 period indicate that Hobart 82% of the lead present in the urban area was attributed to vehicle emissions. However, today lead concentration levels are much lower as lead has been removed from petrol and vehicles no longer emit lead in their exhaust gases.

Further Information

For further information, please contact:

Air Specialist

134 Macquarie Street
GPO Box 1751
Hobart TAS 7001

Phone: 03 6233 3373
Fax: 03 6233 3800

Email: EnvironmentEnquiries@environment.tas.gov.au

See also