Australians may have seen headlines warning “dirty fuel” is back, temporarily, to ease fuel supplies. The phrase sounds alarming, but it has a specific and fairly narrow meaning.

In this context, “dirty fuel” refers to petrol with higher sulfur content than Australia’s newest fuel standards allow.

So how worried should we be about our health if we use petrol containing more sulfur over the coming weeks? What about people with asthma?

Sulfur is a naturally occurring component of crude oil. When fuel is burned in engines, sulfur contributes to air pollution, particularly the gas sulfur dioxide (SO₂) and fine particles (known as PM2.5). When inhaled, both can affect our health.

Australia only fully adopted ultra-low sulfur petrol standards in late 2025, bringing sulfur levels down to 10 parts per million (ppm) across all petrol grades.

Until then, Australians had been using petrol with sulfur levels of 50ppm or more for decades.

But last week, the federal government announced a temporary 60-day exemption allowing petrol with higher sulfur levels (up to around 50ppm) back into the domestic market.

The decision was made in response to severe global supply disruptions, driven by conflict in the Middle East and the partial closure of the Strait of Hormuz, through which a sizeable proportion of the world’s oil normally flows.

According to the government, the exemption allows around 100 million extra litres of petrol per month to be diverted from export markets into Australian service stations, particularly in regional areas.

The government has emphasised the change is temporary and that fuel quality will return to the lower level of permitted sulfur once supply pressures ease.

Sulfur is also found in diesel, but the recently announced changes only relate to petrol standards.

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