Does Gasoline Cause Cancer? What the Science Says Now

Gasoline is classified as “probably carcinogenic to humans” by the International Agency for Research on Cancer, which in February 2025 placed automotive gasoline in its Group 2A category based on a combination of human, animal, and mechanistic evidence.¹ That classification sits one tier below the strongest level (“carcinogenic to humans”) and reflects a picture in which the danger is real but harder to pin down than it is for, say, tobacco smoke. The cancer risk from gasoline is driven not by the fuel as a single substance but by a cocktail of known and suspected carcinogens it contains, the most important being benzene.

What Makes Gasoline Dangerous in the First Place

Gasoline is a complex mixture of hundreds of hydrocarbons, and several of them are individually recognized carcinogens. Benzene, which typically makes up around one to several percent of gasoline by volume, is classified as a known human carcinogen (Group 1 by IARC). It is strongly linked to leukemia and other blood cancers. Another component, 1,3-butadiene, is carcinogenic at multiple organ sites in laboratory animals and has been consistently associated with increased deaths from blood and lymphatic cancers in workers exposed to it.² Polycyclic aromatic hydrocarbons, or PAHs, round out the hazard profile. When researchers tested condensate from gasoline engine exhaust on mouse skin, they found a clear dose-response relationship for tumor formation, and the fraction of PAHs with more than three rings accounted for roughly 80 to 90 percent of the total carcinogenic effect despite making up only about 3.5 percent of the condensate by weight.³ Lung implantation studies in rats confirmed that this same PAH fraction drove the carcinogenic response.⁴

So gasoline’s cancer risk is not theoretical or based on a single suspect ingredient. It arises from multiple chemicals whose individual carcinogenicity is well established, acting through different pathways and targeting different organs.

How Gasoline Damages DNA

The bridge between chemical exposure and cancer runs through damage to DNA, and researchers have measured that damage directly in people who work with gasoline. Gas station attendants in one study had significantly higher levels of DNA fragmentation and higher rates of micronuclei, a marker of chromosomal breakage, compared with unexposed controls.⁵ A separate study of petrol pump workers confirmed the pattern, finding elevated rates of micronucleated cells along with other signs of nuclear damage such as nuclear buds and abnormal chromatin condensation.⁶

Lab work tells a similar story. When human bronchial cells were exposed to whole gasoline engine exhaust in a controlled air-liquid interface setup, DNA strand breaks increased significantly, along with micronuclei and nucleoplasmic bridges, both of which indicate chromosomal damage.⁷ These effects appeared even at diluted exhaust concentrations, which is noteworthy because it suggests the damage is not limited to extreme industrial exposures.

Benzene’s specific mechanism centers on what happens after it is metabolized in the liver and bone marrow. Its breakdown products attack blood-forming cells through chromosomal rearrangements, oxidative stress, disruption of normal gene expression, interference with tumor surveillance, and faulty DNA repair.⁸ The damage begins in hematopoietic progenitor cells, the precursors to all blood cells, where a specific receptor (the aryl hydrocarbon receptor) mediates the toxic response and where reactive oxygen species build up.⁹

Who Gets the Most Exposure and Which Cancers Show Up

The strongest evidence linking gasoline to cancer comes from people who work with it daily. Italian oil refinery workers followed over decades showed increased mortality from pleural cancer, brain cancer, and lymphatic leukemia, with the highest risks appearing among workers with the longest employment durations and longest time since first exposure.¹⁰ A broader systematic review and meta-analysis of petroleum industry workers found that working in the industry was associated with increased risk of mesothelioma, skin melanoma, multiple myeloma, and cancers of the prostate and urinary bladder.¹¹

Petrol station attendants are a closely watched group because their benzene exposure sits in the low-to-moderate range rather than the high end seen in chemical plants. Results here are less consistent. An Italian study found about 3.6 times more cases of acute myeloid leukemia among male station attendants than expected.¹² But a large Nordic cohort of gasoline-exposed workers with estimated benzene levels around 0.5 to 1 milligrams per cubic meter found no excess of leukemia or acute myeloid leukemia, though it did find a roughly 30 percent elevated risk of kidney cancer and a 3.5-fold risk of nasal cancer.¹³ A separate study of filling station attendants found elevated but statistically imprecise risks for esophageal cancer, brain cancer, and non-Hodgkin’s lymphoma, while lung cancer and leukemia were actually lower than expected.¹⁴

The inconsistency is worth understanding rather than dismissing. Exposure levels vary enormously from one workplace to another. So do co-exposures: a refinery worker breathes different compounds than a gas station attendant, and a mechanic’s exposure includes used motor oil, solvents, and brake dust on top of gasoline fumes. Canadian men who spent more than 30 percent of their work time exposed to gasoline engine emissions had roughly 60 percent higher odds of bladder cancer, but only among those who had never also been exposed to diesel emissions.¹⁵ Disentangling gasoline’s specific contribution from the broader occupational chemical stew is one reason the evidence is “limited” rather than “sufficient” in IARC’s judgment.

Risks for People Who Live Near Gas Stations

You do not need to work at a gas station to be exposed to gasoline vapors. People living nearby breathe low levels of benzene and other volatile compounds regularly, and several studies have focused on whether this matters for cancer risk, especially in children.

A meta-analysis pooling four studies on childhood leukemia and residential proximity to petrol stations estimated roughly double the risk for children living closest, with a summary relative risk of about 2.0.¹⁶ A French study looking specifically at the question found that children living within 50 meters of a petrol station had about twice the risk of leukemia compared to children living 1,000 meters or more away, with the strongest associations in older children and at stations with more intense refueling activity, though the numbers were too small for statistical certainty.¹⁷ An earlier ecological study found higher rates of acute myeloid leukemia in children and young adults in municipalities with greater car density, which the authors attributed partially to benzene from gasoline vapors and exhaust.¹⁸

One community-level study made the connection especially vivid. After a large gasoline spill in northeastern Pennsylvania, residents in the affected area experienced leukemia rates several times higher than state or local averages in the years that followed. Acute myeloid leukemia rates were roughly 11 times higher than expected statewide rates for the period 1995 through 2001.¹⁹ That is an extreme case involving chronic exposure to spilled fuel, not normal residential exposure, but it illustrates how dramatically benzene-rich gasoline vapor can shift cancer rates when exposure is sustained.

Exposure You Might Not Think About

The most commonly discussed exposure pathway is inhalation, breathing in vapors while filling your car or working around engines. But skin absorption and indoor air contamination are underappreciated routes that can add meaningfully to your overall benzene dose.

Benzene penetrates intact human skin more rapidly than many small organic molecules. Even from gasoline, where benzene is a minority component, measurable amounts pass through the skin and enter the bloodstream.²⁰ Among the common gasoline aromatics, benzene has the highest skin permeability, penetrating roughly seven times faster than toluene and about 50 times faster than xylenes.²¹ For workers who regularly get gasoline on their hands, this dermal route can be a meaningful contributor to total body exposure.²²

For most people, though, the sneakiest source of gasoline-related benzene is an attached garage. Research using air monitoring and indoor-air models has shown that nearly all of the benzene found inside houses with attached garages comes from garage sources, things like a parked warm car, stored gasoline containers, and lawn equipment. For nonsmokers, the benzene dose from an attached garage dominates their total daily exposure.²³ Even at gas stations where modern vehicles are equipped with onboard vapor recovery systems, fuel vapor emissions were observed during refueling for nearly every vehicle tested, especially at the end of fill-ups.²⁴

Genetic Susceptibility Changes the Risk Equation

Not everyone responds to the same benzene exposure in the same way, and genetics explain a significant share of that variation. How your body metabolizes benzene, through a series of enzymes, determines how much of the harmful breakdown products actually reach your DNA. Certain gene variants speed up activation of benzene into toxic metabolites or slow down the pathways that detoxify them, amplifying the damage.

In a study of Bulgarian petrochemical workers, individuals carrying the highest-risk combination of three gene variants had 5.5 times more DNA strand breaks than those with the lowest-risk combination, despite identical exposures.²⁵ A systematic review looking across studies of benzene-exposed workers confirmed that variants in the NQO1 and GSTT1 genes were the most consistently linked to worse health outcomes, though the full picture of which variants matter most remains unresolved.²⁶

This genetic dimension extends to cancer risk itself. People with the highest cumulative benzene exposure who also carry certain risk variants in bladder cancer susceptibility genes had roughly 2.5 times the odds of bladder cancer compared to unexposed people without those variants.²⁷ The practical takeaway is that population-average risk estimates can substantially underestimate the danger for genetically susceptible individuals. If you work around gasoline or solvents, your personal risk depends on your genes in a way that no workplace exposure limit fully accounts for.

Children and Pregnant Women Face Elevated Concern

Children’s biology makes them more vulnerable to environmental carcinogens in general. They breathe more air per kilogram of body weight, their cells are dividing more rapidly, and their detoxification systems are less mature. The childhood leukemia data described earlier reflects this vulnerability. The meta-analysis of children living near petrol stations and the ecological studies linking car density to childhood leukemia both point in the same direction.

Maternal exposure during pregnancy adds another layer. In the Norwegian Mother and Child Cohort Study, mothers who reported occupational exposure to gasoline or exhaust during pregnancy had roughly 2.6 times the risk of their child developing leukemia, with the risk rising with greater exposure levels. The association held even after adjusting for maternal smoking.²⁸ Living close to petroleum facilities was also associated with increased childhood leukemia risk in the broader meta-analysis of petroleum industry communities.¹¹

What About the Fuel Additive MTBE

Methyl tert-butyl ether, or MTBE, was widely added to gasoline as an oxygenate to reduce air pollution and improve combustion. Because it dissolves easily in water and spread through groundwater near leaking underground storage tanks, concerns about whether it might cause cancer through contaminated drinking water persisted for years. The evidence on MTBE is considerably more reassuring than the evidence on benzene.

A comparative cancer risk assessment of contaminants detected in New Hampshire drinking water found that the cancer risk from MTBE was lower than the risks from all other volatile organic compounds evaluated and thousands of times lower than the risks from naturally occurring substances like arsenic, radium, and radon in the same water supplies.²⁹ A separate reassessment of MTBE’s cancer potency concluded that it most likely does not increase cancer risk unless exposures are high enough to cause tissue damage, and that even under the most conservative assumptions, MTBE would rank among the weakest 10 percent of chemical carcinogens evaluated by the EPA.³⁰ MTBE was included in IARC’s 2025 review alongside gasoline itself; the full monograph will detail its classification, but the existing toxicology suggests it is a far smaller concern than benzene.

How Regulation Has Reduced the Risk Over Time

Gasoline today is not the same product it was a few decades ago. Engine technologies, catalytic converters, fuel reformulation, and tighter benzene limits have all reduced the carcinogenic load. A comprehensive review of the field noted that emissions of many health-concerning components have declined considerably in certain regions thanks to better engine design, improved catalytic aftertreatment, increased fuel economy, and stricter regulation.³¹

One of the most tangible regulatory successes involves benzene content in fuel. After the U.S. EPA implemented a new gasoline benzene standard, the average benzene content in Anchorage, Alaska gasoline dropped by about 70 percent, and annual ambient benzene concentrations fell by roughly half.³² That matters for health outcomes. A quasi-experimental study in Alaska found that after the benzene-reduction regulations took effect, childhood and young adult lymphoma incidence dropped significantly, declining by about 1.2 cases per 100,000, though leukemia incidence did not show a clear change.³³

Ethanol blending is another evolving factor. Adding ethanol to gasoline displaces some of the aromatic hydrocarbons, including benzene, toluene, and xylene, that drive cancer risk.³⁴ Testing a flex-fuel vehicle running on ethanol-blended gasoline showed that emissions of selected PAHs dropped by 67 to 96 percent with a 10 percent ethanol blend, and the overall genotoxic potential of the exhaust fell by roughly 72 percent compared to pure gasoline.³⁵ These are large reductions, and they suggest that the cancer hazard from modern gasoline engines is materially smaller than it was a generation ago, even though it has not disappeared.

Exhaust Versus Vapors at the Pump

People tend to lump “gasoline fumes” and “car exhaust” together, but the two exposures are chemically distinct. Raw gasoline vapor, what you inhale while refueling, is rich in benzene and other light aromatics. Engine exhaust, by contrast, has been through combustion and catalytic conversion, which transforms some compounds and generates others. Exhaust contains PAHs, carbon monoxide, nitrogen oxides, and fine particulate matter.

Interestingly, the animal evidence on inhaled exhaust is more mixed than you might expect. A review of toxicological and epidemiological evidence noted that while chronic heavy exposure to diesel exhaust is a proven lung carcinogen in rats, inhaled gasoline exhaust has not been shown to be carcinogenic in animals.³⁶ This does not mean gasoline exhaust is safe; the human epidemiology and the demonstrated genotoxicity in cell studies tell a different story. But it does highlight that the cancer risk from gasoline may operate differently depending on whether you are inhaling vapors, exhaust, or absorbing fuel through your skin. The direct vapor route, with its high benzene content, may be the more immediately dangerous of the two for cancer specifically, while exhaust contributes cardiovascular and respiratory harms that compound the overall health toll.

Practical Steps to Reduce Your Exposure

Complete avoidance of gasoline exposure is unrealistic for most people. But the difference between careless and careful habits can substantially reduce your benzene dose over a lifetime. When refueling, stand upwind if possible and avoid “topping off” the tank, which generates extra vapor release. The brief exposure from a normal fill-up is small, but it adds up over hundreds of fill-ups per year.

If you have an attached garage, keep the door to the house sealed well. Don’t idle your car in the garage, don’t store open fuel containers there, and consider running lawn equipment outdoors rather than starting it inside. Given the research showing that garage-sourced benzene dominates indoor air exposure for nonsmokers, this is one of the most impactful changes a homeowner can make.²³ For anyone who handles gasoline as part of their job, wearing chemical-resistant gloves matters more than most people realize, given how readily benzene penetrates bare skin.²¹ Pregnant women have particular reason to minimize exposure, given the prospective data linking maternal occupational gasoline or exhaust contact to increased childhood leukemia risk in offspring.²⁸