ATSDR TOXZINE

BENZENE

1 . . . . . . . . . . . . . . . . . . . . . . . . . . . Benzene Overview

2 . . . . . . . . . . . . . Benzene and the Environment

3 . . . . . . . . . . . . . . . . . . . . . . . . Exposure to Benzene

5 . . . . . . . . . . . . . . . . . . . Benzene and the Body

6 . . . . . . . . . . . . . . . Health Effects of Exposure

8 . . . . . . . . . . . . . . . . . . . Benzene and Children

9 . . . . . . . . . . . . . . . Reducing Risk of Exposure

10 . . . . . . . . . . . . . . . . . . . . . . . . . Exposure Testing

12 . . . . . . . . Governmental Recommendations

13 . . . . . . . . . . . . . . . . . . . Additional Information

CONTENTS

BENZENE 

OVERVIEW

Benzene, also known as benzol, is a 

colorless liquid with a sweet odor. 

Benzene evaporates into air very quickly and dissolves 

slightly in water. Benzene is highly flammable.

Most people can begin to smell benzene in air at 

approximately 60 parts of benzene per million parts of 

air (ppm) and recognize it as benzene at 100 ppm. Most 

people can begin to taste benzene in water at 0.5–4.5 

ppm. One part per million is approximately equal to one 

drop in 40 gallons. Benzene is found in air, water, and 

soil. Benzene comes from both industrial and natural 

sources.

Industrial Sources and Uses

Benzene was first discovered and isolated from coal 

tar in the 1800s. Today, benzene is made mostly from 

petroleum. Because of its wide use, benzene ranks 

in the top 20 in production volume for chemicals 

produced in the United States. Various industries use 

benzene to make other chemicals, such as styrene (for 

Styrofoam® and other plastics), cumene (for various 

resins), and cyclohexane (for nylon and synthetic fibers).

Benzene is also used in the manufacturing of some 

types of rubbers, lubricants, dyes, detergents, drugs, 

and pesticides.

Natural Sources

Natural sources of benzene, which include gas 

emissions from volcanoes and forest fires, also 

contribute to the presence of benzene in the 

environment. Benzene is also present in crude oil and 

gasoline and cigarette smoke.◆

Benzene is 

highly 

flammable.

1
BENZENE AND 

THE ENVIRONMENT 

Industrial processes are the main sources of benzene in 

the environment.

Benzene is commonly found in the environment. Benzene levels in the air can 

be elevated by emissions from burning coal and oil, benzene waste and storage 

operations, motor vehicle exhaust, and evaporation from gasoline service stations.

Tobacco smoke is another source of benzene in air, particularly indoors. Industrial 

discharge, disposal of products containing benzene, and gasoline leaks from 

underground storage tanks release benzene into water and soil.

Benzene can pass into air from water and soil surfaces. Once in the air, benzene

reacts with other chemicals and breaks down within a few days. Benzene in the air 

can also be deposited on the ground by rain or snow.

Benzene in water and soil breaks down more slowly. Benzene is slightly soluble

in water and can pass through the soil into underground water. Benzene in the 

environment does not build up in plants or animals.◆

Wax

Benzene Tar

Gas

Oil

2
3

EXPOSURE 

TO BENZENE

Everyone is exposed to a small amount of 

benzene every day.

You are exposed to benzene in the outdoor environment, 

in the workplace, and in the home. Exposure of the 

general population to benzene mainly occurs through 

breathing air that contains benzene. The major sources 

of benzene exposure are tobacco smoke, automobile 

service stations, exhaust from motor vehicles, and 

industrial emissions. Vapors (or gases) from products that 

contain benzene, such as glues, paints, furniture wax, 

and detergents, can also be a source of exposure. Auto 

exhaust and industrial emissions account for about 20% 

of the total national exposure to benzene. About half 

of the exposure to benzene in the United States results 

from smoking tobacco or from exposure to tobacco 

smoke. The average smoker (32 cigarettes per day) takes 

in about 1.8 milligrams (mg) of benzene per day. This 

amount is about 10 times the average daily intake of 

benzene by nonsmokers.

Measured levels of benzene in outdoor air have ranged 

from 0.02 to 34 parts of benzene per billion parts of air 

(ppb) (1 ppb is 1,000 times less than 1 ppm). People 

living in cities or industrial areas are generally exposed 

to higher levels of benzene in air than those living in 

rural areas. Benzene levels in the home are usually higher 

than outdoor levels. People may be exposed to higher 

levels of benzene in air by living near hazardous waste 

sites, petroleum refining operations, petrochemical 

manufacturing sites, or gas stations.

About half 

of the exposure 

to benzene 

in the 

United States 

results from 

smoking tobacco 

or from 

exposure to 

tobacco smoke.
4

For most people, the level of exposure to benzene through food, beverages, or 

drinking water is not as high as through air. Drinking water typically contains less 

than 0.1 ppb benzene. Benzene has been detected in some bottled water, 

liquor, and food. Leakage from underground gasoline storage tanks or from 

landfills and hazardous waste sites that contain benzene can result in benzene 

contamination of well water. People with benzene-contaminated tap water 

can be exposed from drinking the water or eating foods prepared with the 

water. In addition, exposure can result from breathing in benzene while 

showering, bathing, or cooking with contaminated water.

Individuals employed in industries that make or use benzene may be 

exposed to the highest levels of benzene. As many as 238,000 people may 

be occupationally exposed to benzene in the United States. These industries 

include benzene production (petrochemicals, petroleum refining, and coke 

and coal chemical manufacturing), rubber tire manufacturing, and storage 

or transport of benzene and petroleum products containing benzene. Other

workers who may be exposed to benzene include coke oven workers in the 

steel industry, printers, rubber workers, shoe makers, laboratory technicians, 

firefighters, and gas station employees. ◆

As many as 

238,000 people 

may be 

occupationally 

exposed to benzene 

in the 

United States.
5

BENZENE 

AND THE BODY 

Benzene can enter your body through your lungs, 

gastrointestinal tract, and across your skin. 

When you are exposed to high levels of benzene in air, about half of the benzene 

you breathe in passes through the lining of your lungs and enters your bloodstream.

When you are exposed to benzene in food or drink, most of the benzene you take 

in by mouth passes through the lining of your gastrointestinal tract and enters your 

bloodstream. A small amount will enter your body by passing through your skin and 

into your bloodstream during skin contact with benzene or benzene-containing 

products. Once in the bloodstream, benzene travels throughout your body and can 

be temporarily stored in the bone marrow and fat. Benzene is converted to products, 

called metabolites, in the liver and bone marrow. Some of the harmful effects of 

benzene exposure are caused by these metabolites. Most of the metabolites of

benzene leave the body in the urine within 48 hours after exposure.◆
6

HEALTH EFFECTS

OF EXPOSURE 

The main targets of benzene are the nervous system and the 

blood forming organs.

After exposure to benzene, several factors determine whether harmful health effects 

will occur, as well as the type and severity of such health effects. These factors 

include the amount of benzene to which you are exposed and the length of time 

of the exposure. Most information on effects of long-term exposure to benzene are 

from studies of workers employed in industries that make or use benzene. These 

workers were exposed to levels of benzene in air far greater than the levels normally 

encountered by the general population. Current levels of benzene in workplace air 

are much lower than in the past. Because of this reduction and the availability 

of protective equipment such as respirators, fewer workers have symptoms of 

benzene poisoning.

Brief exposure (5–10 minutes) to very high levels of benzene in air (10,000–20,000 

ppm) can result in death. Lower levels (700–3,000 ppm) can cause drowsiness, 

Cancer Determinations 

from Regulatory Agencies 

for Benzene

Department of 

Health and Human 

Services (DHHS)

Known 

carcinogen

International 

Agency for Research 

on Cancer (IARC)

Carcinogenic to 

humans

Environmental 

Protection Agency 

(EPA)

Carcinogenic to 

humans
7

dizziness, rapid heart rate, headaches, tremors, confusion, and unconsciousness. In

most cases, people will stop feeling these effects when they are no longer exposed 

and begin to breathe fresh air.

Eating foods or drinking liquids containing high levels of benzene can cause vomiting, 

irritation of the stomach, dizziness, sleepiness, convulsions, rapid heart rate, 

coma, and death. The health effects that may result from eating foods or 

drinking liquids containing lower levels of benzene are not known. If you 

spill benzene on your skin, it may cause redness and sores. Benzene in your 

eyes may cause general irritation and damage to your cornea.

Benzene causes problems in the blood. People who breathe benzene 

for long periods may experience harmful effects in the tissues that form 

blood cells, especially the bone marrow. These effects can disrupt normal 

blood production and cause a decrease in important blood components.

A decrease in red blood cells can lead to anemia. Reduction in other 

components in the blood can cause excessive bleeding. Blood production 

may return to normal after exposure to benzene stops. Excessive exposure 

to benzene can be harmful to the immune system, increasing the chance for 

infection and perhaps lowering the body’s defense against cancer.

Long-term exposure to benzene can cause cancer of the blood-forming 

organs. This condition is called leukemia. Exposure to benzene has been 

associated with development of a particular type of leukemia called acute 

myeloid leukemia (AML).

Exposure to benzene may be harmful to the reproductive organs. Some

women workers who breathed high levels of benzene for many months 

had irregular menstrual periods. When examined, these women showed a 

decrease in the size of their ovaries. However, exact exposure levels were unknown, 

and the studies of these women did not prove that benzene caused these effects. It

is not known what effects exposure to benzene might have on the developing fetus 

in pregnant women or on fertility in men. Studies with pregnant animals show that 

breathing benzene has harmful effects on the developing fetus. These effects include 

low birth weight, delayed bone formation, and bone marrow damage.

We do not know what human health effects might occur after long-term exposure to 

food and water contaminated with benzene. In animals, exposure to food or water 

contaminated with benzene can damage the blood and the immune system and can 

cause cancer . ◆

The main targets 

of benzene are 

the nervous system 

and the 

blood forming 

organs.
8

BENZENE 

AND CHILDREN 

Children are exposed to benzene in many of the same ways 

that adults are. 

Children (up to 18 years of age) can be affected by benzene exposure in the same 

ways as adults. Benzene can pass from the mother’s blood to a fetus. It is not known if 

children are more susceptible to benzene poisoning than adults. ◆
9

REDUCING RISK 

OF EXPOSURE 

If your doctor finds that you have been exposed to substantial 

amounts of benzene, ask whether your children might also 

have been exposed. Your doctor might need to ask your state 

health department to investigate.

Gasoline and cigarette smoke are two main sources of human exposure to benzene.

Benzene exposure can be reduced by limiting contact with these sources. People 

are exposed to benzene from both active and passive second-hand smoke. Average 

smokers take in about 10 times more benzene than nonsmokers each day. Families 

are encouraged not to smoke in their house, in enclosed environments, or near 

their children.

Benzene is a major component of gasoline and used in many manufacturing 

processes. Increased levels of benzene can be found at fueling stations, and in air 

emissions from manufacturing plants and hazardous waste sites. Living near gasoline 

fueling stations or hazardous waste sites may increase exposure to benzene. People 

are advised not to have their families play near fueling stations, manufacturing plants, 

or hazardous waste sites. ◆
10

EXPOSURE 

TESTING 

Several tests can show whether you have been exposed 

to benzene.

Some of these tests may be available at your doctor’s office. All of these tests are 

limited in what they can tell you. The test for measuring benzene in your breath must 

be done shortly after exposure. This test is not very helpful for detecting very low 

levels of benzene in your body. Benzene can be measured in your blood. However, 

because benzene rapidly disappears in the blood, measurements may be useful only 

for recent exposures.

In the body, benzene is converted to products called metabolites. Certain metabolites 

of benzene, such as phenol, muconic acid, and S-phenylmercapturic acid can be 

measured in the urine. The amount of phenol in urine has been used to check for 

benzene exposure in workers. The test is useful only when you are exposed to 

benzene in air at levels of 10 ppm or greater. However, this test must also be done 

shortly after exposure, and it is not a reliable indicator of how much benzene you 

have been exposed to, because phenol is present in the urine from other sources 
11

(diet, environment). Measurements of muconic acid 

or S-phenylmercapturic acid in the urine are more 

sensitive and reliable indicators of benzene exposure.

The measurement of benzene in blood or of metabolites 

in urine cannot be used for making predictions about 

whether you will experience any harmful health effects.

Blood counts of all components of the blood and 

examination of bone marrow are used to determine 

benzene exposure and its health effects.

For people exposed to relatively high levels of benzene, 

complete blood analyses can be used to monitor 

possible changes related to exposure. However, blood 

analyses are not useful when exposure levels are low.◆

The measurement 

of benzene 

in blood or of 

metabolites 

in urine cannot be 

used for making 

predictions about 

whether you will 

experience 

any harmful 

health effects. 
12

GOVERNMENTAL 

RECOMMENDATIONS 

Recommendations and regulations are also 

updated periodically as more information 

becomes available. 

Recommendations and regulations are also updated 

periodically as more information becomes available. For 

the most current information, check with the federal 

agency or organization that provides it. Some regulations 

and recommendations for benzene include the following: 

EPA has set 5 ppb as the maximum permissible level of 

benzene in drinking water. EPA has set a goal of 0 ppb for

benzene in drinking water and in water such as rivers and 

lakes because benzene can cause leukemia. EPA estimates 

that 10 ppb benzene in drinking water that is consumed 

regularly or exposure to 0.4 ppb in air over a lifetime 

could cause a risk of one additional cancer case for every 

100,000 exposed persons. EPA recommends 200 ppb as 

the maximum permissible level of benzene in water for 

short-term exposures (10 days) for children.

EPA requires that the National Response Center 

be notified following a discharge or spill into the 

environment of 10 pounds or more of benzene.

OSHA regulates levels of benzene in the workplace. The

maximum allowable amount of benzene in workroom air 

during an 8-hour workday, 40-hour workweek is 1 ppm.

Because benzene can cause cancer, NIOSH recommends 

that all workers wear special breathing equipment 

when they are likely to be exposed to benzene at levels 

exceeding the recommended (8-hour) exposure limit of 

0.1 ppm. ◆
13

ADDITIONAL 

INFORMATION 

If you have any more questions or concerns, please contact 

your community or state health or environmental quality 

department or contact ATSDR at the address and phone 

number below. 

Agency for Toxic Substances and Disease Registry

Division of Toxicology and Human Health Sciences

1600 Clifton Road NE, Mailstop F-57

Atlanta, GA 30329-4027

Toll-free information and technical assistance:

1-800-CDCINFO (1-800-232-4636)
ATSDR TOXZINE A publication of CDC/ATSDR

CS250227-A