By: Ruth Callaghan
Living near a major road can mean constant noise — the rumble of trucks, the wail of the occasional police siren — but it is the silent impact of heavy traffic that has researchers concerned.
A growing body of research is providing evidence of the impact of traffic pollution on human health, not just in the countries normally perceived as having unbreathable levels of smog, but much closer to home.
In fact, new modelling based on a New Zealand study released by climate researchers estimates around 11,000 Australian adults die prematurely each year due to exposure from the emissions created by traffic. That’s roughly 10 times the deaths in the national average road toll.
Poor air takes its toll
The numbers represent a wake-up call for both road users and governments says RAC acting general manager Social Impact, Marion Morton, given the risks to Australians will only rise if we do not take action to reduce vehicle emissions.
“The key call out for us is that there's no safe level of air pollution. That’s what the World Health Organisation (WHO) have said — there's no level at which they would deem air pollution to be safe. This pollution can affect anyone and becomes particularly problematic when exposed over a long time.”
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Solid particles from traffic can be very fine, measuring 2.5 micrometres in diameter (also known as particulate matter 2.5, or PM2.5 ), making them a quarter the size of dust, pollen or mould (particulate matter 10, or PM10) and almost 30 times smaller than the diameter of a human hair. Given their size, these particulates can enter the bloodstream easily, creating inflammation and damage to vital organs.
Nitrogen dioxide (NO2) is one of a group of highly reactive gases known as nitrogen oxides. NO2 can cause irritation and inflammation of the respiratory system and can aggravate respiratory diseases such as asthma, or cause acute symptoms such as coughing, wheezing or difficulty breathing.
The same study that identified the impact of poor air quality on premature deaths also suggests more than 12,000 cardiovascular hospitalisations a year can be traced to traffic pollution exposure, along with nearly 7000 respiratory hospitalisations annually and the prevalence of 66,000 childhood asthma cases.
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Marion Morton says a particular challenge is that some population groups are at heightened risk from poor air quality, which increases the need to be aware of the potential impact of traffic pollution.
“There are particularly vulnerable people, including pregnant women, children, elderly people, people with pre-existing health conditions. But many people are really unaware of their risk. We believe it’s important that everyone can access accurate and timely data so they can better understand their risk and mitigate it as best they can.”
Australia’s biggest air sensor network
Capturing accurate and consistent data to aid decision making for cleaner and healthier air is the key motivation behind an RAC initiative that has seen the launch of the biggest air sensor network in Australia. Known as the RAC Air Health Monitor, it measures both PM2.5 and PM10 and NO2.
The RAC Air Health Monitor uses an interactive model, blending air quality data from more than 150 monitoring stations across Perth and Peel, and combines this with other sources, including near real-time traffic data from Main Roads WA, and motor vehicle emissions modelling from Copert Australia.
The result is a searchable map, covering almost 10,000 square kilometres that can provide a guide to the air quality across the Perth and Peel area.
While most results have been within the WHO’s 24-hour average threshold, Morton says there have been some elevated readings. That is particularly concerning as researchers in Australia, the UK and US have all found that even a single unit increase in particulate matter can correlate to increased morbidity.
Major roads a hotspot for pollution
A number of factors can influence air quality levels, including environmental influences like prevailing winds and weather conditions or physical influences like a ‘canyon’ of buildings, however traffic levels remain a key driver of pollution concentration. One clear finding from the RAC Air Health Monitor is that since March 2022, every sensor location has recorded at least one reading higher than the WHO recommendations.
Gavin Pereira, a Professor at Curtin School of Public Health who has researched the area extensively, says in Perth, vehicles are responsible for about 40 per cent of particulates, with industry responsible for a further 20 per cent. Natural sources such as sea salt, dust and bushfires comprise 20 per cent, followed by a range of other sources.
While it has been known for more than a decade that living 300-500m of a major road is associated with poorer health outcomes, with evidence suggesting a link with exacerbation of childhood asthma, there is now increased evidence of neurological diseases.
A recent meta-analysis suggests a correlation between increased PM2.5 and dementia, while Canadian research suggests the risk of dementia is greatest for those living within 50m of a major road.
Professor Pereira’s research has also looked at the impact on pregnant women, finding particulate exposure can put a woman and her baby at risk.
“There is accumulating evidence that pregnant women exposed to higher levels of PM2.5 are at greater risk of adverse pregnancy outcomes such as preterm birth and foetal growth restriction,” he says.
“Observational studies provide strong evidence of an effect, but the biological mechanisms are not well established.
“It will take a long time to reach scientific consensus, and observed effect sizes are small, but in my opinion there is sufficient evidence to warn the public so that sensitive populations can limit exposure.”
Managing exposure only part of the solution
The WA Government’s advice for when PM2.5 levels are elevated includes recommendations for sensitive groups, such as pregnant women, those with heart and lung conditions, children and the elderly.
For days when PM2.5 readings are poor, the advice includes avoiding outdoor physical activity, remaining indoors and closing doors and windows. People are also advised to monitor how they are feeling, follow the treatment plan recommended by their doctor. If a person, or someone in their care, has trouble breathing or experiences tightness in the chest, it is advised to call 000 for an ambulance.
In very poor conditions, vulnerable people are encouraged to seek out clean air away from home if they need to, such as heading to an air-conditioned library or shopping centre. This advice tends to relate more to spikes in poor air quality, however, rather than long term exposure.
Masks can be used to reduce exposure to poor air quality, but need to be at least medical grade and fitted properly for best effect. Air purifiers can assist indoors but redesigning residential properties to block pollution is not an easy fix.
If walking with babies and infants, who can be exposed to higher levels of particulates given they are lower to the ground and closer to exhaust pipes, using a pram cover can help.
But Professor Pereira says there is only so much that individual measures can do to reduce risk.
“The effectiveness of personal measures depends on the situation,” he says. “Staying indoors reduces exposure during a bushfire, and air filters and masks are useful for highly sensitive groups or in high exposure settings. However, modifying behaviour, such as limiting outdoor physical activity over long periods of time, can also be detrimental to health. Reducing emissions should be our primary focus.”
Limit the car, limit the pollution
For RAC, the message to reduce traffic emissions overall remains critical.
Marion Morton says RAC’s Vision 2030 includes reducing harmful vehicle emissions, and has set ambitious targets for 2030, including a 15 per cent reduction in nitrogen oxide emissions per kilometre travelled by car, and a 20 per cent reduction in CO2 emissions per kilometre travelled by car against levels measured in 2016-17.
Some regulatory changes, such as requiring cleaner fuel for passenger vehicles, introducing impactful mandatory fuel efficiency standards, tightening noxious emissions standards and reducing new Australian Design Guidelines for heavy vehicle emissions will assist, but the best fix starts with choosing transport modes other than a car.
“Some 93 per cent of our members feel they have a personal responsibility to help reduce vehicle emissions, so we are hearing that our members are on board with making change,” Morton says.
“It's really about choosing alternatives to the car where you can, using the car less or using public transport or an active transport option, such as a bicycle or walking.”
“When it comes to emissions, the choices we make today can have a big impact on our health and our community's health overall.”
To check the air health in your local area, check the RAC Air Health Monitor's interactive map.
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