Does Automotive Gasoline Cause Cancer? What Science Says

IARC finds convincing evidence that exposure to automotive gasoline causes bladder cancer and acute myeloid leukemia.

It had been 37 years since the International Agency for Research on Cancer (IARC) last evaluated whether automotive gasoline causes cancer. That was in 1988 and since then a large number of new scientific studies on the subject have been produced worldwide. IARC convened 20 experts from 16 countries in February-March to critically review the total updated scientific evidence base. I had the distinct privilege and pleasure of chairing the Working Group meeting, where we evaluated the studies according to strict and established criteria.

Sufficient evidence that automotive gasoline causes bladder cancer and leukaemia

In 1988, automotive gasoline was previously classified (volume 45) as possibly carcinogenic to humans (also known as Group 2B). This year, we concluded that overall there was sufficient evidence for cancer in humans. Therefore, the answer to the question is indeed, yes, there is convincing evidence that automotive gasoline causes cancer. Automotive gasoline exposure causes urinary bladder cancer and acute myeloid leukaemia in adults. The official classification is known as a Group 1 classification, that automotive gasoline is carcinogenic to humans. This is the highest level used by IARC when evaluating whether an agent is carcinogenic to humans.

Source: IARC.

The studies in exposed humans mainly included people exposed to automotive gasoline fuel and vapours as part of their job. Automotive gasoline is a complex mixture, and occupational exposure occurs during the production and transport of gasoline and during vehicle refuelling. Service station attendants are also exposed to higher levels of gasoline than the general public.

One of the major epidemiological studies assessing gasoline exposure, which contributed to this evaluation, was conducted by researchers now at ISGlobal (formerly at IMIM during the study).

Limited evidence that automotive gasoline can cause other types of cancer

Studies of other types of cancer were also reviewed, and it was determined that the evidence was limited. This means that there were some studies that showed that automotive gasoline was associated with an increased risk of other types of cancer, but the evidence was not strong enough to make a clear conclusion at this moment in time. There was limited evidence in humans for non-Hodgkin lymphoma (including chronic lymphocytic leukaemia), multiple myeloma, myelodysplastic syndromes, and cancers of the stomach and kidney. There was also limited evidence for acute lymphoblastic leukaemia (ALL) in children, including from studies of children living in close proximity to service stations.

Gasoline causes genetic damage, oxidative stress and chronic inflammation

In addition to evaluating studies of cancer in humans exposed to automotive gasoline, we also found that there was sufficient evidence for cancer in laboratory animals (studies of mice and rats) and strong mechanistic evidence in exposed humans. There was strong evidence that gasoline is genotoxic (causes genetic damage), that it induces oxidative stress, and it induces chronic inflammation in exposed humans, mainly service station attendants. There was also convincing mechanistic evidence in experimental systems for endpoints associated with oxidative stress and chronic inflammation.

More research is needed

Although automotive gasoline is now classified as a Group 1 agent, there is still much more research that can be done to provide an even more complete picture of the cancer risk to humans. More research can be done to provide more evidence as to whether automotive gasoline causes cancer at other sites, beyond urinary bladder cancer and acute myeloid leukaemia in adults, including in new large-scale studies in humans. It is important that research is conducted independently, is unbiased, and free from potential conflicts of interest.

What about gasoline additives?

In addition to automotive gasoline, we also evaluated whether oxygenated gasoline additives cause cancer. Oxygenated gasoline additives are used to enhance octane rating and to increase combustion efficiency, as well as minimize atmospheric pollution. The additives evaluated included methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), tert-butyl alcohol (TBA), diisopropyl ether (DIPE), and tert-amyl methyl ether (TAME). The evidence for the different oxygenated gasoline additives was weaker than it was for automotive gasoline and classifications ranged from Group 2B (possibly carcinogenic to humans) to Group 3 (not classifiable as to its carcinogenicity to humans).

For more information please also see the IARC Monographs website.

IARC is the specialised agency of the World Health Organisation (WHO) that focusses specifically on cancer research and prevention. The IARC Monographs Programme has coordinated to date, 138 cancer monograph evaluation meetings in its more than 50-year history. These evaluations are often used for national and international policies, guidelines, and recommendations to minimize cancer risks.