Benzene and Cancer Risk

Benzene can increase your risk of certain cancers, especially with long-term high exposure. Limiting your exposure can help lower your risk and protect your health.

What is benzene?

Benzene is a colorless, flammable liquid with a sweet odor. It evaporates quickly when exposed to air. Benzene is formed from natural processes, such as volcanoes and forest fires. Most people, however, are exposed to benzene through human activities.

Benzene is one of the 20 most widely used chemicals in the United States. It is used mainly to make other chemicals, including:

• Plastics
• Resins
• Lubricants
• Rubbers
• Dyes
• Detergents
• Medicines
• Pesticides

In the past, benzene was also commonly used as an industrial solvent, a substance that can dissolve or extract other substances, and as a gasoline additive. These uses have been reduced in recent decades.

Benzene can also be found in crude oil and gasoline, motor vehicle exhaust, and cigarette smoke.

Does benzene cause cancer?

Exposure to benzene has been linked with a higher risk of cancer, particularly leukemia and other cancers of blood cells.

What expert agencies say

In general, the American Cancer Society (ACS) does not determine whether something should be considered a carcinogen (something that can cause cancer). Instead, ACS looks to other respected organizations for help with this.

Based on animal and human evidence, several expert agencies have evaluated the cancer-causing potential of benzene.

• The International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO), classifies benzene as “carcinogenic to humans.” This classification is based on sufficient evidence that benzene causes acute myeloid leukemia (AML). IARC also notes that benzene exposure has been linked with acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), multiple myeloma, and non-Hodgkin lymphoma.
• The US National Toxicology Program (NTP) has classified benzene as “known to be a human carcinogen.”
• The US Environmental Protection Agency (EPA) classifies benzene as a known human carcinogen.

For more information on the classification systems used by these agencies, see How Do We Know What Causes Cancer? and Known and Probable Human Carcinogens.

What do studies on benzene show?

Researchers try to determine if a substance causes cancer using 2 main types of studies:

• Lab studies are done using lab animals or cells in lab dishes.
• Studies in people compare groups to see if people with higher exposures are more likely to develop cancer.

Often, neither type of study provides conclusive evidence on its own. Researchers usually look at both lab-based and human studies when trying to figure out if something causes cancer.

Lab studies

When inhaled or swallowed, benzene has been found to cause different types of tumors in rats and mice.

The bone marrow is where new blood cells are made. In the lab, benzene has been shown to cause chromosome changes in bone marrow cells. These types of changes are commonly found in human leukemia cells.

These results support the finding of a higher risk of leukemia in humans.

Studies in people

In some studies, rates of leukemia were higher for workers exposed to high levels of benzene. Significant increases in AML have been shown for these workers. People exposed to high levels of benzene on the job include those working in chemical, shoemaking, and oil refining industries.

Some studies have also suggested links to childhood leukemia (mainly AML). In adults, links have been shown between benzene and ALL, CLL, and other blood-related cancers, such as multiple myeloma and non-Hodgkin lymphoma. However, the evidence is not as strong for these cancers.

There is less evidence linking benzene to other types of cancer.

How are people exposed to benzene?

People are exposed mainly by breathing in air containing benzene. Benzene can also be absorbed through the skin during contact with a source such as gasoline. Because liquid benzene evaporates quickly, this type of benzene exposure is less common.

People can be exposed to benzene:

• In the environment
• At work
• When using some consumer products

Community exposures

People can be exposed to benzene from gasoline fumes, automobile exhaust, emissions from some factories, and wastewater from certain industries. Benzene is commonly found in air. The levels in most places are usually very low.

Levels of benzene can be higher in enclosed spaces with unventilated fumes from gasoline, glues, solvents, paints, and art supplies. Areas with heavy traffic, gas stations, and areas near industrial sources may also have higher air levels.

Cigarette smoke, either from smoking directly or from secondhand smoke, accounts for about half of the exposure to benzene in the United States. Benzene levels in rooms containing tobacco smoke can be many times higher than normal.

People can also be exposed to benzene in contaminated drinking water and some foods, although the levels are usually very low.

Workplace exposures

Typically, the highest levels of benzene exposure have been in the workplace. However, high-level exposures have decreased over the last several decades due to federal and state safety regulations.

Workers in industries that make or use benzene can be exposed to this chemical. These include:

• The rubber industry
• Oil refineries
• Chemical plants
• Shoe manufacturers
• Gasoline-related industries

Other people who may be exposed to benzene at work include:

• Steel workers
• Printers
• Lab technicians
• Gas station employees
• Firefighters

Are benzene levels regulated?

Several US government agencies regulate benzene levels and exposures.

• The Occupational Safety & Health Administration (OSHA) is responsible for health and safety regulations in most workplaces. OSHA limits exposure to benzene in the air in most workplaces to 1 ppm (part per million) during an average workday and a maximum of 5 ppm over any 15-minute period. When working at potentially higher exposure levels, OSHA requires employers to provide personal protective equipment (PPE), such as respirators.
• The EPA limits the percentage of benzene allowed in gasoline to a yearly average of 0.62% by volume (with a maximum of 1.3%).
• The EPA limits concentrations of benzene in drinking water to 5 ppb (parts per billion). Some states may have lower limits. Likewise, the US Food and Drug Administration (FDA) sets a limit of 5 ppb in bottled water.
• The Consumer Product Safety Commission (CPSC) considers any consumer product containing 5% or more by weight of benzene to be hazardous, requiring special labeling.

Can I avoid or limit my exposure to benzene?

It might not be possible to avoid benzene completely. But if you are concerned about benzene, you can limit your exposure in several ways.

Stay away from cigarette smoke. If you smoke, it’s important to try to quit. It’s also important to avoid secondhand smoke. Cigarette smoke is a major source of exposure to benzene and other harmful chemicals.

Pump gas carefully. Use gas stations with vapor recovery systems that capture the fumes. Avoid getting gasoline on your skin.

When possible, limit the time you spend near idling car engines. This can help lower your exposure to exhaust fumes, which contain benzene and other potentially harmful chemicals.

Use common sense around any chemicals that might contain benzene. Limit or avoid exposure to fumes from solvents, paints, and art supplies, especially in unventilated spaces.

If you are exposed to benzene at your workplace, talk to your employer about limiting your exposure through process changes. Perhaps benzene could be replaced with another solvent. Maybe the source of benzene could be enclosed. You might also be able to use PPE. If needed, you can also contact OSHA, which can provide more information or assistance.

What should I do if I’ve been exposed to benzene?

For short-term exposure to high levels of benzene, the Centers for Disease Control and Prevention (CDC) recommends:

• Getting away from the source
• Removing any contaminated clothing
• Washing exposed areas with soap and water
• Getting medical care as soon as possible

If you think you may have been exposed to benzene over a long period of time, talk to a doctor. Benzene can be measured in the blood or breath, and breakdown products of benzene can be measured in urine. These tests can only detect recent exposures to benzene. They can’t reliably show how much benzene you’ve been exposed to over time, and they can’t predict possible health effects.