Volume 138: Automotive gasoline and some oxygenated gasoline additives

We are pleased to announce that the results of the recent IARC Monographs evaluation of the carcinogenicity of automotive gasoline and some oxygenated gasoline additives have now been published in The Lancet Oncology. This summary article presents the conclusions of IARC Monographs Meeting 138.

Automotive gasoline, methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), tert-butyl alcohol (TBA), diisopropyl ether (DIPE), and tert-amyl methyl ether (TAME) were accorded high priority by the Advisory Group to Recommend Priorities for the IARC Monographs during 2020–2024. Gasoline and MTBE were previously evaluated by the IARC Monographs in Volumes 45 and 73, respectively. ETBE, TBA, DIPE, and TAME were evaluated for the first time.

Automotive gasoline is a commercial product and a complex mixture primarily used as a fuel in internal combustion engines. Although the composition of gasoline has changed over time, the typical components are volatile, petroleum-derived hydrocarbons that are blended with various additives. Occupational and general population exposure occurs primarily through the inhalation of gasoline vapour. Occupational exposure is expected during the production and transport of gasoline and during car refuelling. Service station attendants are exposed to higher levels of gasoline than is the general population. The present evaluation did not include marine or aviation gasoline, gasoline engine exhaust, or diesel fuel or engine exhaust.

MTBE, ETBE, TBA, TAME, and DIPE are volatile compounds used as oxygenated additives in gasoline to increase combustion efficiency, and more commonly since the elimination of lead. All except TAME are chemicals with a high production volume. MTBE and ETBE have been used most widely, including historically in the USA and currently at the highest concentrations in some countries in Europe and Asia. These chemicals have been detected in groundwater contaminated by leaking underground storage tanks and in air polluted by gasoline evaporation and traffic emissions. Workers may be exposed during the production of these chemicals and via gasoline vapour containing these additives. Occupational exposure has been measured among ship and railroad tanker workers, gasoline pump repairers and inspectors, service station attendants, and automobile mechanics. The general population is mainly exposed via gasoline vapours at service stations, in air pollution, or via water and soil contaminated by gasoline spills.

The Working Group evaluated automotive gasoline as carcinogenic to humans (Group 1) on the basis of sufficient evidence for cancer in humans and the combination of sufficient evidence for cancer in experimental animals and strong mechanistic evidence in exposed humans. Automotive gasoline causes cancer of the urinary bladder and acute myeloid leukaemia in adults. The evidence was limited for a causal association between automotive gasoline and acute lymphoblastic leukaemia in children, and non-Hodgkin lymphoma (including chronic lymphocytic leukaemia), multiple myeloma, myelodysplastic syndromes, and cancers of the stomach and kidney in adults.

MTBE and ETBE were both classified as possibly carcinogenic to humans (Group 2B) on the basis of sufficient evidence for cancer in experimental animals. The mechanistic evidence in experimental systems was limited for MTBE and strong for ETBE. TBA, DIPE, and TAME were each evaluated as not classifiable as to its carcinogenicity to humans (Group 3). For all the oxygenated gasoline additives, the evidence regarding cancer in humans was inadequate.

The full scientific assessment will be published as Volume 138 of the IARC Monographs.

Turner MC, Godderis L, Guénel P, Hopf N, Quintanilla-Vega B, Coelho Soares-Lima SC, et al.
Carcinogenicity of automotive gasoline and some oxygenated gasoline additives
Lancet Oncol, Published online 21 mars 2025;
https://doi.org/10.1016/PII/S1470-2045(25)00165-2

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