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PUBLIC HEALTH STATEMENT 

SULFUR DIOXIDE 

CAS#: 7446-09-5 

Division of Toxicology December 1998 

This Public Health Statement is the summary 

chapter from the Toxicological Profile for Sulfur 

Dioxide. It is one in a series of Public Health 

Statements about hazardous substances and their 

health effects. A shorter version, the ToxFAQsTM, is 

also available. This information is important 

because this substance may harm you. The effects 

of exposure to any hazardous substance depend on 

the dose, the duration, how you are exposed, 

personal traits and habits, and whether other 

chemicals are present. For more information, call 

the ATSDR Information Center at 1-888-422-8737. 

_________________________________________ 

This public health statement tells you about sulfur 

dioxide and the effects of exposure. 

The Environmental Protection Agency (EPA) 

identifies the most serious hazardous waste sites in 

the nation. These sites make up the National 

Priorities List (NPL) and are the sites targeted for 

long-term federal cleanup activities. Sulfur dioxide 

has been found in at least 16 of the 1,467 current or 

former NPL sites. However, the total number of 

NPL sites evaluated for this substance is not known. 

As more sites are evaluated, the sites at which sulfur 

dioxide is found may increase. This information is 

important because exposure to this substance may 

harm you and because these sites may be sources of 

exposure. 

When a substance is released from a large area, 

such as an industrial plant, or from a container, such 

as a drum or bottle, it enters the environment. This 

release does not always lead to exposure. You are 

exposed to a substance only when you come in 

contact with it. You may be exposed by breathing, 

eating, or drinking the substance or by skin contact. 

If you are exposed to sulfur dioxide, many factors 

determine whether you'll be harmed. These factors 

include the dose (how much), the duration (how 

long), and how you come in contact with it. You 

must also consider the other chemicals you're 

exposed to and your age, sex, diet, family traits, 

lifestyle, and state of health. 

1.1 WHAT IS SULFUR DIOXIDE? 

Sulfur dioxide is a colorless gas with a pungent 

odor. It is a liquid when under pressure. Sulfur 

dioxide dissolves in water very easily. It cannot 

catch fire. 

Sulfur dioxide in the air results primarily from 

activities associated with the burning of fossil fuels 

(coal, oil) such as at power plants or from copper 

smelting. In nature, sulfur dioxide can be released 

to the air, for example, from volcanic eruptions. 

1.2 WHAT HAPPENS TO SULFUR DIOXIDE 

WHEN IT ENTERS THE 

ENVIRONMENT? 

Once released into the environment, sulfur dioxide 

moves to the air. In the air, sulfur dioxide can be 

converted to sulfuric acid, sulfur trioxide, and 

sulfates. Sulfur dioxide dissolves in water. Once 

dissolved in water, sulfur dioxide can form 

sulfurous acid. Soil can absorb sulfur dioxide, but 

we do not know if or how it moves in soil. 

1.3 HOW MIGHT I BE EXPOSED TO 

SULFUR DIOXIDE? 

You may be exposed to sulfur dioxide mainly by 

breathing air that contains it. You may also be 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

 

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PUBLIC HEALTH STATEMENT 

SULFUR DIOXIDE 

CAS#: 7446-09-5 

Division of Toxicology December 1998 

exposed to sulfur dioxide by skin contact with it. 

The people most often exposed to sulfur dioxide are 

workers in plants where sulfur dioxide occurs as a 

by-product, such as in the copper smelting industry 

and in the processing or burning of coal or oil. 

Other exposures occur in the manufacture of 

sulfuric acid, paper, food preservatives, and 

fertilizers. The primary way that workers are 

exposed to sulfur dioxide is through the air. 

Workers may be exposed to concentrations of sulfur 

dioxide that are higher than typical outdoor air 

levels. People living near heavily industrial 

activities that involve smelting copper or the 

processing or burning of coal or oil are also likely to 

be exposed to sulfur dioxide by breathing it. 

1.4 HOW CAN SULFUR DIOXIDE ENTER 

AND LEAVE MY BODY? 

If you breathe air containing sulfur dioxide, you 

may absorb it into your body through your nose and 

lungs. Sulfur dioxide can easily and rapidly enter 

your bloodstream through your lungs. Once in the 

body, it breaks down to sulfate and leaves through 

the urine. 

1.5 HOW CAN SULFUR DIOXIDE AFFECT 

MY HEALTH? 

To protect the public from the harmful effects of 

toxic chemicals and to find ways to treat people 

who have been harmed, scientists use many tests. 

One way to see if a chemical will hurt people is to 

learn how the chemical is absorbed, used, and 

released by the body; for some chemicals, animal 

testing may be necessary. Animal testing may also 

be used to identify health effects such as cancer or 

birth defects. Without laboratory animals, scientists 

would lose a basic method to get information 

needed to make wise decisions to protect public 

health. Scientists have the responsibility to treat 

research animals with care and compassion. Laws 

today protect the welfare of research animals, and 

scientists must comply with strict animal care 

guidelines. 

Short-term exposures to high levels of sulfur 

dioxide can be life-threatening. Exposure to 100 

parts of sulfur dioxide per million parts of air (ppm) 

is considered immediately dangerous to life and 

health. Previously healthy nonsmoking miners who 

breathed sulfur dioxide released as a result of an 

explosion in an underground copper mine 

developed burning of the nose and throat, breathing 

difficulties, and severe airway obstructions. Longterm exposure to persistent levels of sulfur dioxide 

can also affect your health. Lung function changes 

have been observed in some workers exposed to 

0.4–3.0 ppm sulfur dioxide for 20 years or more. 

However, these workers were also exposed to other 

chemicals, making it difficult to attribute their 

health effects to sulfur dioxide exposure alone. 

Additionally, exercising asthmatics are sensitive to 

the respiratory effects of low concentrations (0.25 

ppm) of sulfur dioxide. 

For comparative purposes, typical outdoor 

concentrations of sulfur dioxide may range from 0 

to 1 ppm. Occupational exposures to sulfur dioxide 

may lawfully range from 0 to 5 ppm as enforced by 

your state OSHA (Occupational Safety and Health 

Administration). During any 8-hour workshift of a 

40-hour workweek, the average concentration of 

sulfur dioxide in the workplace may not exceed 5 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

 

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PUBLIC HEALTH STATEMENT 

SULFUR DIOXIDE 

CAS#: 7446-09-5 

Division of Toxicology December 1998 

ppm. However, during system malfunctions or 

unforeseen events, levels approaching 50 ppm or 

more have been reported. 

Studies in animals support the human data 

regarding respiratory effects of sulfur dioxide. At 

low levels (less than 1 ppm) of sulfur dioxide 

exposure, guinea pigs displayed changes in their 

ability to breathe as deeply or as much air per 

breath. More severe symptoms seen in animals 

exposed to high concentrations of sulfur dioxide 

include decreased respiration, inflammation or 

infection of the airways, and destruction of areas of 

the lung. 

1.6 HOW CAN SULFUR DIOXIDE AFFECT 

CHILDREN? 

This section discusses potential health effects from 

exposures during the period from conception to 

maturity at 18 years of age in humans. Potential 

effects on children resulting from exposures of the 

parents are also considered. 

Since sulfur dioxide is primarily present as a gas, 

the general public is exposed to it mostly by 

breathing contaminated air. Levels of sulfur 

dioxide in the atmosphere vary from region to 

region and are mainly influenced by the intensity of 

industry and development usually associated with 

cities. Therefore, children with the highest 

exposure to sulfur dioxide are those living near 

industrial sources (i.e., industries that process or 

burn coal or oil, copper smelting plants, sulfuric 

acid manufacturers, fertilizer factories, or paper 

pulp factories). 

Members of the general public may also have 

additional risk for exposure if they live near a 

hazardous waste site contaminated with sulfur 

dioxide. At 16 of the 1,467 NPL hazardous waste 

sites, sulfur dioxide has been identified in air, 

surface water, groundwater, soil, or sediment. 

Children, as well as adults, living near these sites 

are most likely to be exposed by breathing 

contaminated air. 

Most of the effects of sulfur dioxide exposure that 

occur in adults (i.e., difficulty breathing, changes in 

the ability to breathe as deeply or take in as much 

air per breath, and burning of the nose and throat) 

are also of potential concern in children, but it is 

unknown whether children are more vulnerable to 

exposure. Children may be exposed to more sulfur 

dioxide than adults because they breathe more air 

for their body weight than adults do. Children also 

exercise more frequently than adults. Exercise 

increases breathing rate. This increase results in 

both a greater amount of sulfur dioxide in the lungs 

and enhanced effects on the lungs. One study 

suggested that a person's respiratory health, and not 

his or her age, determines vulnerability to the 

effects of breathing sulfur dioxide. This study 

implies that healthy adolescents (ages 12–17) are no 

more vulnerable to the effects of breathing sulfur 

dioxide than healthy senior citizens. 

Long-term studies surveying large numbers of 

children have indicated possible associations 

between sulfur dioxide pollution and respiratory 

symptoms or reduced breathing ability. Children 

who have breathed sulfur dioxide pollution may 

develop more breathing problems as they get older, 

may make more emergency room visits for 

treatment of wheezing fits, and may get more 

respiratory illnesses than is typical for children. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

 

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PUBLIC HEALTH STATEMENT 

SULFUR DIOXIDE 

CAS#: 7446-09-5 

Division of Toxicology December 1998 

However, studies like these are unable to provide 

conclusive evidence about sulfur dioxide's effects 

on children's health because many other pollutants 

are also present in the air. 

It is known that exercising asthmatics are sensitive 

to low concentrations of sulfur dioxide. Therefore, 

increased susceptibility is expected in children with 

asthma, but it is not known whether asthmatic 

children are more sensitive than asthmatic adults. 

Additionally, asthma occurs most often in African 

Americans, children between the ages of 8 and 11, 

and people living in cities. For unknown reasons, 

the death rates associated with asthma are also 

higher in non-Caucasian people. Therefore, it is 

expected that asthmatic, African American children 

living in urban areas have increased sensitivity to 

sulfur dioxide. 

There are few studies which provide evidence of 

reproductive or developmental effects of sulfur 

dioxide exposure in humans. One study found no 

relationship between spontaneous abortion and 

exposure to sulfur dioxide among women living in 

an industrial community in Finland. However, 

another study in China showed a relationship 

between decreased infant birth weight and exposure 

to sulfur dioxide pollution during pregnancy. 

Another study, in the Czech Republic, showed that 

18-year-old males who were exposed to high levels 

of sulfur dioxide had sperm with more 

abnormalities and reduced abilities to move. 

Studies like these, though, are often hard to 

interpret. It can be difficult to distinguish among 

the effects of individual pollutants within air 

pollution mixtures. Tests on laboratory mice have 

shown that sulfur dioxide exposure did not affect 

reproductive function. 

Only a small number of developmental studies have 

been done in animals, and of these, in only one 

study were serious effects on development 

observed. Developmental studies are designed to 

determine how a pregnant female's exposure to a 

chemical might affect the normal processes that 

take place in her child as it grows (i.e., adverse 

effects might include a child with learning deficits 

or problems in social behavior). In one study the 

offspring of mice who breathed sulfur dioxide 

during their pregnancy were born small and had 

some abnormal reflexes. Three other studies in 

mice and one in rabbits showed no serious effects. 

Minor variations in the skeleton did occur in the 

offspring of the rabbits exposed to sulfur dioxide 

during pregnancy, and delayed bone hardening 

occurred in the offspring of treated mice. Due in 

large part to these conflicting results, conclusions 

about the effects of sulfur dioxide on unborn 

children cannot be drawn from the available studies. 

A study in rats indicated that poor maternal 

nutrition might cause offspring to be more 

susceptible later in life to the damage that can occur 

from breathing sulfur dioxide. In rats, offspring 

whose mothers were fed a low protein diet while 

they were pregnant showed greater lung damage 

from breathing sulfur dioxide when they were older. 

It is unknown if similar conclusions about human 

maternal nutrition can be drawn. 

It is not likely that parental exposure to sulfur 

dioxide will cause any changes in a mother's eggs or 

father's sperm that could affect their unborn 

children. It is not known if sulfur dioxide or the 

products to which it is broken down within the body 

can cross the placenta or accumulate in breast milk; 

further, it is also unknown whether these resulting 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

 

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PUBLIC HEALTH STATEMENT 

SULFUR DIOXIDE 

CAS#: 7446-09-5 

Division of Toxicology December 1998 

breakdown products would be harmful. 

Accumulation of sulfur dioxide in maternal tissues 

and then, movement during pregnancy, is unlikely 

because this compound is water soluble. 

1.7 HOW CAN FAMILIES REDUCE THE 

RISK OF EXPOSURE TO SULFUR 

DIOXIDE? 

If your doctor finds that you have been exposed to 

significant amounts of sulfur dioxide, ask if children 

may also be exposed. When necessary your doctor 

may need to ask your State Department of Public 

Health to investigate. 

Because exposure to sulfur dioxide is most likely to 

occur by breathing contaminated air, families 

should try to limit their outdoor activities during 

times of high air pollution. While levels of sulfur 

dioxide in the air are typically highest during the 

winter months, human exposure to sulfur dioxide 

has been shown to be greatest during the summer 

months. This result is most likely seen because 

people enjoy being outdoors in warm weather and 

often leave their household windows open for 

ventilation. 

By paying attention to news bulletins and air 

pollution advisories, families can control their 

amount of exposure. The EPA (Environmental 

Protection Agency) issues the vast majority of air 

quality alerts. Such warnings might reach the 

public when ATSDR (Agency for Toxic Substances 

and Disease Registry) issues a Public Health 

Advisory and notifies the EPA of a public health 

threat caused by high levels of atmospheric sulfur 

dioxide. State and local health and environmental 

agencies will also be notified and will, in turn, 

notify their communities. People with respiratory 

difficulties should pay special attention to these 

warnings. Additionally, asthmatic children's 

outdoor exercise should be limited when high levels 

of sulfur dioxide are present in the air. 

Since exposure to sulfur dioxide occurs primarily 

through direct breathing of contaminated air, 

workers in plants where sulfur dioxide occurs as a 

by-product will not expose their family members at 

home through residues on their skin or clothes. 

1.8 IS THERE A MEDICAL TEST TO 

DETERMINE WHETHER I HAVE BEEN 

EXPOSED TO SULFUR DIOXIDE? 

Sulfur dioxide in the body is changed into other 

sulfur-containing chemicals in the body. These 

breakdown products can be found and measured in 

the blood and urine. However, their measurement 

requires special equipment which is not routinely 

available in a doctor's office. Furthermore, 

exposure to chemicals other than sulfur dioxide can 

also produce sulfate, so, the presence of sulfate 

breakdown in your body does not necessarily mean 

you have been exposed to sulfur dioxide. Lung 

function tests can be used to examine potential 

respiratory effects of sulfur dioxide. However, tests 

of lung function changes cannot determine whether 

or not you have been specifically exposed to sulfur 

dioxide because other chemicals can produce 

similar lung function changes. 

1.9 WHAT RECOMMENDATIONS HAS THE 

FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

The federal government develops regulations and 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

 

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PUBLIC HEALTH STATEMENT 

SULFUR DIOXIDE 

CAS#: 7446-09-5 

Division of Toxicology December 1998 

recommendations to protect public health. 

Regulations can be enforced by law. Federal 

agencies that develop regulations for toxic 

substances include the Environmental Protection 

Agency (EPA), the Occupational Safety and Health 

Administration (OSHA), and the Food and Drug 

Administration (FDA). Recommendations provide 

valuable guidelines to protect public health but 

cannot be enforced by law. Federal organizations 

that develop recommendations for toxic substances 

include the Agency for Toxic Substances and 

Disease Registry (ATSDR) and the National 

Institute for Occupational Safety and Health 

(NIOSH). 

Regulations and recommendations can be expressed 

in not-to-exceed levels in air, water, soil, or food 

that are usually based on levels that affect animals, 

then they are adjusted to help protect people. 

Sometimes these not-to-exceed levels differ among 

federal organizations because of different exposure 

times (an 8-hour workday or a 24-hour day), the use 

of different animal studies, or other factors. 

Recommendations and regulations are also 

periodically updated 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 sulfur dioxide include the 

following: 

The federal government has set regulations to 

protect individuals from the possible health effects 

of breathing sulfur dioxide. EPA recommends that 

the long-term, 1-year average concentrations of 

sulfur dioxide should not exceed 0.03 ppm. The 

short-term, 24-hour average concentration should 

not exceed 0.14 ppm more than once a year. OSHA 

regulates levels of sulfur dioxide in the workplace. 

This regulation states that workroom air should 

contain no more than an average of 2 ppm sulfur 

dioxide over an 8-hour working shift for 5 

consecutive days in a workweek. NIOSH 

recommends that the average workroom air levels 

of sulfur dioxide not exceed 2 ppm over a 10-hour 

period. The 15-minute average exposure in air that 

should not be exceeded at any time during a 

workday is 5 ppm. 

1.10 WHERE CAN I GET MORE 

INFORMATION? 

If you have any more questions or concerns, please 

contact your community or state health or 

environmental quality department or: 

Agency for Toxic Substances and Disease Registry 

Division of Toxicology 

1600 Clifton Road NE, Mailstop F-32 

Atlanta, GA 30333 

Information line and technical assistance: 

Phone: 888-422-8737 

FAX: (770)-488-4178 

ATSDR can also tell you the location of 

occupational and environmental health clinics. 

These clinics specialize in recognizing, evaluating, 

and treating illnesses resulting from exposure to 

hazardous substances. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

 

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PUBLIC HEALTH STATEMENT 

SULFUR DIOXIDE 

CAS#: 7446-09-5 

Division of Toxicology December 1998 

To order toxicological profiles, contact: 

National Technical Information Service 

5285 Port Royal Road 

Springfield, VA 22161 

Phone: 800-553-6847 or 703-605-6000 

Reference 

Agency for Toxic Substances and Disease Registry 

(ATSDR). 1998. Toxicological profile for sulfur 

dioxide. Atlanta, GA: U.S. Department of Health 

and Human Services, Public Health Service. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov