Public Health Statement for Sulfur Dioxide
Spanish: Anhídrido sulfuroso
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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 1-800-232-4636.
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.
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
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.
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
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
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.
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
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 Long-term exposure to
persistent levels of sulfur dioxide can also affect your health
Lung function changes have been observed in some workers exposed
to 0.4ï¿½3.0 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 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.
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
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 12ï¿½17) 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 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
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 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.
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.
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.
What recommendations has the federal government made to protect human health?
The federal government develops regulations
and 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
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.
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
Where can I get more information?
If you have questions or concerns, please contact your community or state health or environmental quality department or:
For more information, contact:
Agency for Toxic Substances and Disease Registry
Division of Toxicology and Human Health Sciences
4770 Buford Highway
Chamblee, GA 30341-3717
Phone: 1-800-CDC-INFO 888-232-6348 (TTY)
Email: Contact CDC-INFO
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.