New Data Reveals Popular Car Models' Hidden NOx Pollution in Australia | Health Impact & Stricter Standards

Unveiling Hidden Car Pollution: Australia's New Data Exposes NOx Emissions from Popular Models

When two cars pull up at a red light – one a compact SUV, the other a large 4WD – most would assume the larger, petrol-powered vehicle is the bigger polluter. While the smaller SUV might emit less carbon dioxide (CO2), new data reveals a surprising truth: it could be producing significantly more of another, often overlooked, pollutant with a greater immediate public health impact: oxides of nitrogen, or “NOx.”

NOx, comprising nitrogen dioxide (NO2) and nitric oxide (NO), is largely invisible and frequently ignored, yet it contributes to hundreds of premature deaths annually from serious conditions like heart and lung diseases. Despite its critical health implications, drivers have historically lacked clear information on their car’s NOx emissions. However, newly accessible data is shedding light on which popular models are the worst offenders, coinciding with the implementation of updated Australian standards designed to drastically cut NOx emissions from new diesel vehicles.

The Gap Between Lab Tests and Real-World Emissions

Unlike CO2, NOx emissions have never been prominently displayed on vehicle stickers or guides in Australia. Previously, cars adhered to maximum NOx levels set nine years ago, enforced through laboratory tests where vehicles ran on treadmills and exhaust gases were measured. While useful, these lab conditions often don’t reflect real-world driving.

To bridge this gap, the Australian Automobile Association (AAA) conducted comprehensive real-world testing. They fitted over 100 popular cars, utes, and vans with emissions measurement systems and drove them through Geelong traffic under strict protocols. Their findings revealed that many vehicles polluted far more on the road than suggested by lab tests, with significant discrepancies found particularly in NOx emissions.

Diesel Cars: Major Contributors to NOx Pollution

Petrol cars generally performed well, with only two out of 90 tested exceeding the 60 mg/km NOx limit. Diesel vehicles, however, struggled dramatically. Seventeen of the 24 diesels tested surpassed their respective limits (280 mg/km for commercial, 180 mg/km for passenger models – two to three times higher than petrol limits), with diesels exceeding mandated maximums by nearly 40 percent on average. This was against standards in place since 2016.

Though diesel vehicles constitute only about one in ten cars on the road, AAA data suggests they emit approximately 20 times more NOx than petrol cars. Given that NOx exposure is linked to the majority of traffic pollution-related deaths, these relatively fewer diesel vehicles have a disproportionately high public health impact. Research from the University of Tasmania's Centre for Safe Air estimates thousands of premature deaths and hospital admissions are caused by traffic-related particulate and NOx pollution annually.

The Health Toll of Invisible Gases

Professor Fay Johnston, director of the Centre for Safe Air, emphasizes that motor vehicles are a major source of Australian air pollution, and among all vehicle emissions, NOx has the most significant impact on public health. NOx forms a near-invisible haze, with levels remaining high within 100-200 meters of busy roads. Long-term exposure to this gas can damage lungs, cause bronchitis and asthma, and inflame body cells, contributing to heart disease.

Australia's Lagging Standards and the Solution: SCR Technology

Despite the severe health consequences, Australia has lagged significantly, with its NOx pollution regulations about a decade behind Europe, the UK, and the US. A striking example from the AAA’s tests compares a 2024 Toyota LandCruiser Prado (GXL) diesel and a 2024 Mitsubishi Pajero Sport (GSR) diesel. While having similar fuel consumption and CO2 emissions, the Pajero’s NOx output was about 17 times higher than the LandCruiser’s. The key difference lies in “after treatment,” specifically Selective Catalytic Reduction (SCR) technology, which uses a nitrogen-rich additive like AdBlue to convert NOx into harmless nitrogen gas, water, and CO2. The LandCruiser Prado incorporates SCR, while the Pajero Sport does not.

Shawn Kook, director of the UNSW engine research laboratory, notes that virtually all diesels sold in Europe now use SCR to meet stricter standards in place since 2015, proving the technology is readily available. The primary barrier to wider adoption has been the added cost for manufacturers.

New Standards for a Cleaner Future

As of December 1, new Australian standards have more than halved the NOx emission limits for new diesel utes, vans, and SUV models. The limit for diesel passenger vehicles has dropped from 180 mg/km to 80 mg/km, and for commercial diesels from 280 mg/km to 125 mg/km. This effectively means new diesel models without SCR technology will no longer be sold in Australia. Existing models have until mid-2028 to comply. The new standards also introduce updated laboratory testing procedures that better simulate real-world driving conditions, though petrol car NOx limits remain unchanged.

Most popular diesel models, based on real-world testing, currently exceed these new limits, necessitating upgrades from manufacturers. The Federal Chamber of Automotive Industries reassures that popular diesel models will remain available, as car makers have had time to prepare. Dr. Nic Surawski, an environmental engineering expert at UTS, highlights that these new standards will compel manufacturers to supply Australia with superior technology, rectifying the current situation where Australia often received older, less clean vehicle models.

With the European Union preparing for even tighter Euro 7 emissions rules – potentially the last standards before combustion engines are phased out entirely – Australia's past delay in updating its Euro 5 standards means it has "really dropped the ball," according to Dr. Surawski, making the new changes a crucial step forward.