ToxFAQsTM for Hydraulic Fluids
Spanish: Fluidos Hidráulicos
CAS#: 55957-10-3; 68937-40-6; 50815-84-4; 55962-27-1; 66594-31-8; 63848-94-2; 107028-44-4; 28777-70-0
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This fact sheet answers the most frequently
asked health questions about hydraulic fluids. For more information, you may call the ATSDR Information Center at 1-888-422-8737. This fact sheet is one in a series of summaries about hazardous substances and their health effects. It is important you understand this information 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.
Exposure to hydraulic fluids occurs mainly in the workplace. Drinking certain types of hydraulic fluids can cause death in humans, and swallowing or inhaling certain types of hydraulic fluids has caused nerve damage in animals. Contact with some types of hydraulic fluids can irritate your skin or eyes. These substances have been found in at least 10 of the 1,428 National Priorities List sites identified by the Environmental Protection Agency (EPA).
What is hydraulic fluids?
Hydraulic fluids are a large group of
liquids made of many kinds of chemicals. They are used in
automobile automatic transmissions, brakes, and power steering;
fork lift trucks; tractors; bulldozers; industrial machinery;
and airplanes. The three most common types of hydraulic fluids
are mineral oil, organophosphate ester, and polyalphaolefin.
Some of the trade names for hydraulic fluids include Durad®,
Fyrquel®, Skydrol®, Houghton-Safe®, Pydraul®,
Reofos®, Reolube®, and Quintolubric®. (Use of
trade names is for identification only and does not imply
endorsement by the Agency for Toxic Substances and Disease
Registry, the Public Health Service, or the U.S. Department
of Health and Human Services.)
Some hydraulic fluids have a bland, oily
smell and others have no smell; some will burn and some will
not burn. Certain hydraulic fluids are produced from crude
oil and others are manufactured.
What happens to hydraulic fluids when it enters the environment?
- Hydraulic fluids can enter the environment from spills,
leaks in machines that use them, or from storage areas and
- If spilled on soil, some of the ingredients in hydraulic
fluids will stay on top and others will sink into the groundwater.
- In water, some hydraulic fluids' ingredients will transfer
to the bottom and can stay there for more than a year.
- Certain chemicals in hydraulic fluids may break down in
air, soil, or water, but how much breaks down isn't known.
- Fish may contain some hydraulic fluids if they live in
How might I be exposed to hydraulic fluids?
- Touching or swallowing hydraulic fluids.
- Breathing hydraulic fluids in the air near machines where
hydraulic fluids are used.
- Touching contaminated water or soil near hazardous waste
sites or industrial manufacturing facilities that use or
make hydraulic fluids.
How can hydraulic fluids affect my health?
Little is known about how hydraulic fluids
can affect your health. Since hydraulic fluids are actually
mixtures of chemicals, some of the effects seen may be caused
by additives in the hydraulic fluids.
In people, the effects of breathing air
with high levels of hydraulic fluids are not known. Drinking
large amounts of some types of hydraulic fluids can cause
pneumonia, intestinal bleeding, or death in humans. Weakness
of the hands was seen in a worker who touched a lot of hydraulic
Rabbits that inhaled very high levels
of one type of hydraulic fluid had trouble breathing, congested
lungs, and became drowsy. The nervous systems of animals that
swallowed or inhaled other hydraulic fluids were affected
immediately with tremors, diarrhea, sweating, breathing difficulty,
and sometimes several weeks later with weakness of the limbs,
or paralysis. The immediate effects are caused because hydraulic
fluids stop the action of certain enzymes, called cholinesterases,
in the body. There are no reports of people swallowing or
breathing the types of hydraulic fluids that cause these effects.
When certain types of hydraulic fluids were put into the eyes
of animals or allowed to touch the skin of people or animals
for short periods of time, redness and swelling occurred.
It is not known whether hydraulic fluids can cause birth defects
or reproductive effects.
How likely is hydraulic fluids to cause cancer?
The Department of Health and Human Services
(DHHS), the International Agency for Research on Cancer (IARC),
and the EPA have not classified hydraulic fluids as to their
Is there a medical test to show whether I've been exposed to hydraulic fluids?
Hydraulic fluids can't be measured in
blood, urine, or feces, but certain chemicals in the hydraulic
fluids can be measured. Some of the hydraulic fluids stop
the activity of certain enzymes, called cholinesterases, in
blood and this activity can be measured. However, many other
chemicals also cause this effect. This test isn't available
at most doctors' offices, but can be done at special laboratories
that have the right equipment.
Has the federal government made recommendations to protect human health?
There are no federal government recommendations
to protect humans from the health effects of the major hydraulic
fluids. However, mineral oil, the major chemical ingredient
of one type of hydraulic fluid, is part of the petroleum distillate
class of chemicals and there are regulations for these chemicals.
The Occupational Safety and Health Administration
(OSHA) has set an exposure limit of 2,000 milligram per cubic
meter (mg/m3) petroleum distillates for an 8-hour workday,
40-hour workweek. The National Institute for Occupational
Safety and Health (NIOSH) recommends an exposure limit of
350 mg/m3 petroleum distillates for a 10-hour workday,
Additive: Substance added to another
in small amounts to improve its properties.
CAS: Chemical Abstracts Service.
Carcinogenicity: Ability to cause cancer.
Petroleum Distillate: A chemical fraction
Agency for Toxic Substances and Disease
Registry (ATSDR). 1997. Toxicological Profile for hydraulic fluids. 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
Office of Innovation and Analytics, Toxicology Section
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.