Petrol and the risk of cancer

How will the reclassification of gasoline as carcinogenic to humans, impact dutyholders and their insurers?

Summary

The IARC has recently reclassified automative gasoline as carcinogenic to humans¹ and advise that exposure to gasoline can cause bladder cancer and acute myeloid leukaemia (AML). 

Whilst there are a significant number of new bladder cancer and AML diagnoses every year in the UK (10,500 and 2,945 respectively), it seems unlikely that this will result in any significant increase in associated claims at the present time. This is principally because claimants will find it difficult to establish causation, not least due to the multitude of potential exposure sources.  

Dutyholders should ensure that they appropriately manage the risk associated with gasoline exposure, especially in respect of those who are potentially at high risk (i.e. mechanics, forecourt attendants, municipal workers etc.). Failure to do so will likely hinder the defensibility of such claims. 

Background

Until recently, automative gasoline was not classed as carcinogenic to humans. The previous classification in 1988 was that gasoline was “possibly carcinogenic to humans.” Since then, numerous studies have investigated the association between gasoline exposure and cancer in humans.

Gasoline, a commercial product, is a complex mixture primarily used in internal combustion engines. Typical components of gasoline are volatile, petroleum-derived hydrocarbons, including alkanes, alkenes and aromatics which are blended with various additives. The composition of gasoline has changed over time and the actual composition will vary according to the source of crude oil, the manufacturing process and between batches. 

In February -March 2025 a working group of 20 scientists met at the International Agency For Research on Cancer (IARC) to finalise their evaluation of the carcinogenicity of automative gasoline (“gasoline”) and some oxygenated gasoline additives. Gasoline was classified as carcinogenic to humans based on sufficient evidence for cancer in humans and the combination of sufficient evidence for cancer in experimental animals and strong mechanistic evidence in exposed humans.

The group concluded that there is sufficient evidence in humans that gasoline causes urinary bladder cancer and acute myeloid leukaemia (AML) in adults. Consistent increases in the incidence of bladder cancer and AML were noted in occupational cohort and case control studies of service station attendants, gasoline distribution workers and studies specifically assessing gasoline exposure.

Studies showed that service station attendants also had elevated levels of oxidative DNA damage endpoints and compromised antioxidant defence systems. The same studies also showed that chronic exposure to gasoline induced a systemic inflammatory response that correlated with the duration of exposure. There was also some suggestive evidence that gasoline induces epigenetic alterations, immunosuppression and hormonal alterations in service station attendants.

There are around 10,500 new bladder cancer cases in the UK every year.  Bladder cancer is the 11th most common cancer in the UK accounting for 3% of all cancer cases. Since the early 2000s, bladder cancer incidence rates have decreased by almost a quarter. AML is a blood cancer that originates in the bone marrow and affects white blood cells. There are around 2,945 new cases each year and it accounts for less than 1% of all new cancer cases. (2017-2019, Cancer Research UK).

Who is at risk

Occupational and general population exposure occurs primarily through inhalation of gasoline vapour. Occupational exposure is mainly during the production and transport of gasoline and during vehicle refuelling, and includes occupations such as tanker drivers, mechanics, refinery workers and petrol station attendants. Volatile compounds are used as oxygenated additives in gasoline to increase combustion efficiency, especially since the elimination of lead. Workers can be exposed during additive production.

The general population is mainly exposed via gasoline vapours at service stations, via air pollution or via water and soil contaminated by gasoline spills. Compared with the general population, service station attendants are exposed to higher levels of gasoline and similar levels of engine exhaust (although this evaluation does not include engine exhaust). There is limited data available on the absorption, distribution and excretion of gasoline but most individual components of gasoline are absorbed via inhalation and dermally then excreted via urine.

What does this mean for Defendants and Insurers

Previous studies have not demonstrated a statistically significant link between cancer and occupational exposure to gasoline. Now that gasoline classification has been elevated to carcinogenic in humans, employers of those workers referred to above should consider the risks and how exposure can be managed. 

Claims for bladder cancer and AML will likely be deemed indivisible conditions for the purposes of causation. Both conditions can be caused by agents other than gasoline, such as smoking, or can be idiopathic in nature. Consequently, where there are multiple possible causes, it is arguable that these claims will not be subject to the material contribution test, but rather the but for test² (i.e. is it more likely than not that the Claimant’s gasoline exposure has caused the cancer rather than smoking or idiopathic causes). This will be a particularly high causative hurdle for claimants to overcome. 

In any event, even if the Court deems that material contribution should apply in such cases, causation will be difficult to prove because medical science is unlikely to be able to establish the causal mechanism of the disease, beyond that of an increase in risk. Consequently, Defendants and their insurers will likely be able to maintain robust causation defences to these claims.  

1. IARC Monographs evaluation of the carcinogenicity of automotive gasoline and some oxygenated gasoline additives – IARC

2. Re Wilsher v Essex HA [1988] AC 1074