By Herbert Beauchamp
Australia has the dubious honour of having the highest incidence of asthma in the world. Twenty-five per cent of children in Australia have asthma, and the rate has doubled over the last 10 years.
To the well-known triggers for asthma such as plant pollens and dust mites must be added pollutants from motor vehicle emissions. In the city of Sydney, an added burden of 1.1 million tonnes of chemicals per year is added to the pollutants in the air.
All the major pollutants such as tropospheric ozone, sulphur dioxide and carbon monoxide have significant effects on lung function. Health regulators are slowly and reluctantly accepting the relationship of air pollution to asthma.
Increasingly research is implicating ozone, nitrogen dioxide and particulates — all pollutants formed from vehicle exhausts. In October 1993 Professor R. Davies of St Bartholomew's Hospital in the UK published new research which showed that both ozone and nitrogen dioxide damage the lining of the respiratory system, allowing triggering substances to penetrate, impair the cilia (the tiny hairs that clear infection from cells) and lead to the chemical cascade that brings on asthma attacks.
Until recently there were no known mechanisms to explain how even low levels of pollution might exacerbate asthma. It has now become evident that asthma is a persistent disease associated with inflammation of the airways. Pollutants can activate inflammatory cells either directly or indirectly through stimulating the release of cytokines. These are cell mediators which are released by one cell type and influence the activity of either the same or other cell types.
An attack is triggered when a chemical irritates the damaged airways. It starts with wheezing, breathlessness and tightening in the chest. Breathing gets harder and harder in a severe attack, and in a very bad incident the amount of oxygen in the blood drops alarmingly.
Pollution has the worst effect on children because they are much more vulnerable. Children under three breathe in twice as much air as adults for each kilogram of body weight. Children exercise more and so take in more air, and thus more pollution. The airways of children are narrower and so more easily constricted. Because their lungs are maturing, pollution can affect them permanently, leading to a lifetime of breathing difficulties.
What can we do about all this?
We can demand an improvement of public transport — in NSW expenditure on road building has been 20 times that on public transport. We can ask government to impose stringent controls on motor vehicle emissions. We can ask parents not to leave their car engines idling for more than 30 seconds when picking up their children. Owners of pre-1986 cars can find out whether those cars will run on unleaded petrol. We can participate in "rideshare" schemes.
Although it is government that can introduce and enforce non-polluting legislation, individuals cannot afford to be passive — the issue is too important.
[Herbert Beauchamp is chairperson of the Toxic Chemicals Committee, Total Environment Centre, NSW.]