Benzene and Cancer: Exposure and Leukemia Risk

This page is for anyone wondering whether benzene exposure affects their cancer risk. It covers what benzene is, how people are exposed, its link to leukemia, and ways to lower exposure.

Benzene is a chemical found in crude oil, gasoline, and cigarette smoke. Breathing it in over long periods can harm the bone marrow, where blood cells are made. That damage can lead to leukemia. Everyday levels are usually low, but smokers and some workers face much higher exposure.

Benzene is a colorless or light-yellow liquid at room temperature. It evaporates quickly into the air. Industry uses it as a solvent and as a building block for many other chemicals, and it is in gasoline. Benzene is a natural part of crude oil, which is the main source of it today. Volcanoes and forest fires give off benzene as well.

People are exposed mainly by breathing air that holds the chemical.

• Tobacco smoke. Mainstream cigarette smoke accounts for about half of the total exposure in the U.S. population. Among smokers, 90 percent of benzene exposure comes from smoking.
• Work in industries that make or use benzene. These workers may face the highest levels, though rules have cut exposures in recent decades.
• Glues, adhesives, cleaning products, and paint strippers.
• Outdoor air, which holds low levels from secondhand smoke, gasoline fumes, vehicle exhaust, and industry.

Exposure to benzene raises the risk of leukemia and other blood disorders. The risk rises with the amount and the length of exposure. That is why workplace exposure and heavy smoking are the biggest concerns.

The International Agency for Research on Cancer (IARC) is the branch of the World Health Organization that judges what causes cancer. It places benzene in Group 1, carcinogenic to humans. Group 1 is the top level of evidence. It means studies give enough proof that benzene can cause cancer in people. In the United States, the National Toxicology Program reaches the same view. Its Report on Carcinogens lists benzene as known to be a human carcinogen.

Hazard means something can cause harm. Risk means how likely that harm is for you. A carcinogen listing is about hazard only. It says benzene can cause cancer under some conditions. It does not predict what will happen to any one person. Your risk depends on the dose, the years of exposure, and other factors. Being in the same group as another agent does not mean posing the same danger in daily life.

• Do not smoke, and stay away from secondhand smoke.
• Limit time breathing gasoline fumes. Do not linger while refueling.
• Use solvents, paints, and glues where the air moves well.
• Follow workplace limits and protection if you work with benzene.

To see how one exposure fits the whole picture, read our overview of cancer prevention and what raises cancer risk.

Benzene is a known human carcinogen (IARC Group 1). For most people, tobacco smoke is the largest source by far, and that one is under your control. Keep solvent work and refueling well ventilated. Then put your attention on the bigger risks in your life.