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Benzene Exposure

This page was reviewed or revised on Wednesday, November 04, 2009 1:16 PM

Fact Sheet

What is Benzene?

Benzene, also known as benzol, is a colourless liquid with a sweet odour made from petroleum. A component of gasoline, benzene is also used to make other chemicals like styrene. Benzene is used for making some types of rubbers, lubricants, dyes and drugs. It evaporates quickly and is highly flammable. Most people can begin to detect the odour of benzene in the air at concentrations of about 2 - 5 parts per million (ppm) . In most cases, benzene does not exist by itself, but is a part of a mixture of chemicals (gasoline for example). When benzene is mixed with other chemicals, some of the chemicals which are less toxic may give off an odour at much lower concentrations.

Risk of Exposure

The major sources of benzene exposure are gas stations (benzene is a component of gasoline), exhaust from motor vehicles, tobacco smoke, and industrial emissions. Background levels of benzene normally present in the air range from 2.8 to 20 parts per billion (ppb). Most exposure to benzene is from inhalation.

What are the current exposure limits for benzene?

The Ontario Ministry of Labour has recently set the occupational exposure limit at 1 ppm. This exposure limit is based on an 8 hour work day, 40 hours a week. One study has shown that the 1 ppm limit would be similar to the level of benzene a person would be exposed to while pumping gas. The short term exposure limit is set at 5 ppm for fifteen minutes.

Health Effects of Benzene Exposure

Short term health effects are usually caused by brief exposure to benzene at elevated levels. Symptoms may include eye and throat irritations, headache, dizziness and rapid heart rate. These symptoms are usually mild and will disappear once the exposure has stopped and the person starts to breathe fresh air. People who are more sensitive may experience these symptoms for up to a few days. Short term exposure to high levels of benzene may cause drowsiness, dizziness, confusion and unconsciousness.

Long Term Health Effects

People who breathe benzene at 10 ppm or higher for long periods of time may experience harmful effects in the blood forming organs causing low blood counts (anemia) and weakening of the immune system. Chronic exposure to levels of benzene above 10 ppm over a long period of time (5-10 years) has been associated with the development of a particular type of leukemia called acute myeloid leukemia (AML). Benzene has been classified by the International Agency for Cancer Research as a human carcinogen. The effects of chronic exposure to benzene on human reproduction are not known.

Where can I get more information?

In the workplace, contact your health and safety officer or Occupational Health Nurse. For the general public, ask your family doctor or contact the Environmental Health Department of the Community Health Services.

Based on information provided by Sidney Siu, M.D., FRCPC, SRS Consultants Inc.