17. What Can You Do?

Some measures to reduce transport noise require changes in international and national laws, and in the planning and operation of transport systems. However, as transport users we can all make a contribution to reducing noise. Most measures that reduce noise also reduce air pollution and are better for our health and the quality of the local environment, and some reduce fuel use and save money.

Walk or cycle for short journeys

Use public transport

Stick to speed limits

Keep vehicles well maintained – this will save fuel too − keep silencers in good order − check brakes are properly adjusted

Drive smoothly

Don't rev the engine

Turn off the engine when stationary

Keep the music down

Don’t slam doors or sound the horn unnecessarily

Choose quieter tyres

(http://www.environmental-protection.org.uk/noise/environmental-noise/transport noise/#wa2220)

18. Ozone Pollution

Ozone (O3) is a positive or negative presence in our atmosphere, depending on where it is found. The atmosphere of the earth is divided into four layers, defined by their distance above the planet's surface, with ozone important in the two lower levels − the stratosphere and the troposphere. In the troposphere − the level that contains the air we breathe − ozone is a damaging pollutant. In the stratosphere − 15 − 50 kilometres above the ground − ozone forms a protective layer which filters out the harmful rays of the sun.

Tropospheric ozone. Ozone (O3) occurs naturally in the troposphere (the lowest layer of our atmosphere − 8 − 16km above the surface of the earth) and the stratosphere (the second layer of the atmosphere − 12 − 50km above the earth). The background level of tropospheric, or ground level, ozone is 10 − 30ppb. However, in Europe it is thought to be increasing by 1 − 2% a year due to the effects of pollution. Higher concentrations of ozone can be damaging to plants, animals and materials. Tropospheric ozone is also a greenhouse gas, contributing to global warming.

Ozone pollution. Ozone is a secondary pollutant formed by the action of sunlight on primary pollutants − these are nitrogen oxides from vehicle emissions and industry and volatile organic compounds from vehicles, solvents, paint and industry. Nitrogen oxides react in sunlight (photochemical reaction) to form ozone − a major constituent of photochemical smog. Other constituents are PAN (peroxyacetylnitrate) and aldehydes.

Ozone Formation. The atmospheric chemistry involved in ozone formation is complex. Ultraviolet (uv) radiation from the sun breaks down nitrogen oxide (NO2) into nitrogen oxide and atomic oxygen −

NO2 + uv - NO + O

Oxygen atoms combine with oxygen molecules to form ozone −

O + O2 - O3

However, ozone will not accumulate when nitrogen oxide is present, as the two molecules react to reform nitrogen dioxide and oxygen −

NO + O3 - NO2 + O2

Problems occur when volatile organic pollutants (VOCs) such as hydrocarbons, react in the atmosphere to form oxygenated products such as aldehydes. The oxygen in these molecules allows NO to form NO2, without breaking down ozone, thus ozone accumulates. The build-up of ozone therefore depends upon the relative concentrations of nitrogen oxides, hydrocarbons and other pollutants, and sunlight. It takes time for the ozone to accumulate as the chemical reactions involved are quite slow − ozone builds up in polluted air masses. This takes several days and is favoured by prolonged sunny weather and low windspeeds. Polluted air masses often come from continental Europe, so ozone episodes are more frequent in southern England.

The distribution and build up of ozone is also affected by air movement. Although most of the pollutants that form ozone (ozone precursors) are generated in urban areas, concentrations of tropospheric ozone tend to be higher away from towns. Ozone levels are also higher on high ground and on the coast. For this reason ozone monitoring stations are situated in the countryside as well as in urban areas.

Effects of ozone pollution. Ozone is an unstable oxygen molecule and therefore a strong oxidising agent. It is very reactive and can impact on health. Elevated concentrations can cause eye, nose and throat irritation, chest discomfort, cough and headache. People who exercise or suffer from bronchitis, respiratory allergies or asthma are particularly at risk.

Ozone is also damaging to crops − peas, beans, spinach and wheat are all particularly susceptible. It can affect crop yields and tree growth. It also damages materials such as rubber, paint and textiles. Material damage is related to long term exposure to ozone rather than severe episodes. As ozone is very reactive with all surfaces, it is unlikely that high concentrations will be found indoors.

Reducing ozone pollution. Ozone levels in the air are dependent on atmospheric conditions, as well as pollutants, and ozone can travel on air masses. Therefore reducing pollution requires action at international level to reduce ozone precursors (the pollutants that form ozone). Guidelines for levels of ozone in the air, to protect health, and vegetation have been set by several bodies.

World Health Organisation. As the long term chronic health effects of ozone are uncertain, the recommended WHO air quality guideline is 100 µg/m3 over 8 hours.

EU Ozone Thresholds. Directive 2002/3/EC relating to ozone in ambient air, came into force in 2002; with measures for its implementation had to be in place by September 2003.

 Under the Directive Member states must identify zones and agglomerations where these values and objectives are unlikely to be met and draw up action plans or programmes. It also requires that monitoring information is available to the public.

Threshold	Target Value	µg/m3	Target
Health protection	8 hour mean	120	To be achieved by 2010, not to be exceeded more than 25 days per calendar year, averaged over 3 years
Health protection	8 hour mean	120	To be achieved by 2020
Vegetation protection	5 year average	1800 (from 1 hour values May - July)	To be attained where possible' by 2010
Vegetation protection		6000	To be achieved by 2020 'save where not achievable through proportionate measures'
Information threshold	1 hour average	180
Alert threshold	3 consecutive hour average	240

UK Air Quality Guidelines. The UK objective for protection of human health for Ozone is 100 µgm3. This is measured as a daily maximum of a running 8 hour mean, to be achieved by the end of 2005, with no more than 10 exceedences per year. The UK National Air Quality Strategy recognises that ozone is not easily controlled by local measures and that measures to reduce it will therefore need to be agreed at European level. The ozone objectives are therefore for guidance and are not included in UK regulations. 

Minimising the effects. Prolonged still sunny weather is necessary for ozone to build up, making photochemical smog a summer phenomenon and only an intermittent problem in the UK. However, during the summer there are often regular exceedences of guidelines − particularly in the south and west. During photochemical smog episodes it is advisable to avoid taking vigorous exercise and stay indoors if possible, particularly elderly and the vulnerable. In some US and European cities photochemical smog is a more serious summer problem. Drastic measures have been taken during severe episodes, such as limiting or banning vehicle use, banning charcoal barbeques and petrol driven lawn mowers.

The problem of tropospheric ozone is not easy to solve. Tighter controls on vehicle and industrial emissions of NOx and VOCs and a reduction in traffic levels would reduce emissions of ozone precursors and ozone formation. The European Union have agreed a Directive controlling VOC emissions during petrol storage and distribution and limits on solvent emissions from industry.

What can you do? There are measures that you can take to reduce emissions of the pollutants that cause ozone formation:

Limit car use, and ensure your vehicle is running efficiently to reduce emissions

Try to avoid parking the car in sunlight when the engine is hot, and overfilling the tank or spilling petrol

Use water based or low solvent paints, glues and varnishes