Hydrazine

302-01-2

Hazard Summary-Created in April 1992; Revised in January 2000

Individuals may be exposed to hydrazine in the workplace or to small amounts in tobacco smoke. Symptoms of acute (short-term) exposure to high levels of hydrazine may include irritation of the eyes, nose, and throat, dizziness, headache, nausea, pulmonary edema, seizures, and coma in humans. Acute exposure can also damage the liver, kidneys, and central nervous system in humans. The liquid is corrosive and may produce dermatitis from skin contact in humans and animals. Effects to the lungs, liver, spleen, and thyroid have been reported in animals chronically (long-term) exposed to hydrazine via inhalation. Increased incidences of lung, nasal cavity, and liver tumors have been observed in rodents exposed to hydrazine. EPA has classified hydrazine as a Group B2, probable human carcinogen.

Please Note: The main sources of information for this fact sheet are EPA's Integrated Risk Information System (IRIS), which contains information on the carcinogenic effects of hydrazine including the unit cancer risk for inhalation exposure, EPA's Health and Environmental Effects Profile for Hydrazine, and the Agency for Toxic Substances and Disease Registry's (ATSDR's) Toxicological Profile for Hydrazines.

Uses

Hydrazine is used in agricultural chemicals (pesticides), chemical blowing agents, pharmaceutical intermediates, photography chemicals, boiler water treatment for corrosion protection, textile dyes, and as fuel for rockets and spacecraft. (4,6,8,10)

Sources and Potential Exposure

Individuals may be occupationally exposed to hydrazine in the workplace. (1,2,10)
Accidental discharge into water, air, and soil may occur during storage, handling, transport, and improper waste disposal. However, hydrazine rapidly degrades in the environment and is rarely encountered. (2,3)
Small amounts of hydrazine have been detected in tobacco smoke. (2,10)

Assessing Personal Exposure

Hydrazine may be detected in the blood of exposed individuals. (1,2)

Health Hazard Information

Acute Effects:

Symptoms of acute exposure to high levels of hydrazine include irritation of the eyes, nose, and throat, temporary blindness, dizziness, headache, nausea, pulmonary edema, seizures, and coma in humans. Acute exposure can also damage the liver, kidneys, and the central nervous system (CNS) in humans. (2-4)
The liquid is corrosive and may produce chemical burns and severe dermatitis from skin contact. (1,4)
Acute animal tests in rats, mice, rabbits, and guinea pigs have demonstrated hydrazine to have high acute toxicity from inhalation and ingestion and extreme acute toxicity from dermal exposure. (5)

Chronic Effects (Noncancer):

Information is not available on the chronic effects of hydrazine in humans.
In animals chronically exposed to hydrazine by inhalation, effects on the respiratory system, liver, spleen, and thyroid have been observed. (10)
EPA has not established a Reference Concentration (RfC) or a Reference Dose (RfD) for hydrazine. (4)
The California Environmental Protection Agency (CalEPA) has calculated a chronic inhalation reference exposure level of 0.0002 milligrams per cubic meter (mg/m³) based on liver and thyroid effects in hamsters. The CalEPA reference exposure level is a concentration at or below which adverse health effects are not likely to occur. It is not a direct estimator of risk but rather a reference point to gauge the potential effects. At lifetime exposures increasingly greater than the reference exposure level, the potential for adverse health effects increases. (11)
ATSDR has calculated an intermediate inhalation minimal risk level (MRL) of 0.005 mg/m³ (0.004 parts per million [ppm]) based on liver effects in mice. The MRL is an estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse noncancer health effects over a specified duration of exposure. (10)

Reproductive/Developmental Effects:

Information is not available on the reproductive or developmental effects of hydrazine in humans.
Data regarding developmental effects in animals are limited to a study in which hydrazine injected into pregnant rats resulted in fetotoxicity including increased fetal and neonatal mortality. (6,10)
Inhalation of hydrazine for a year resulted in effects to the ovaries, endometrium, and uterus in female rats and to the testes in male hamsters. (10)

Cancer Risk:

Adequate information is not available on the carcinogenic effects of hydrazine in humans. (4)
Increased incidences of lung and liver tumors have been observed in mice exposed to hydrazine by inhalation, in their drinking water, via gavage and injection. Tumors in the nasal cavity were observed in rats and hamsters exposed by inhalation. (4,6,7)
EPA has classified hydrazine as a Group B2, probable human carcinogen. (4)
EPA uses mathematical models, based on human and animal studies, to estimate the probability of a person developing cancer from breathing air containing a specified concentration of a chemical. EPA calculated an inhalation unit risk estimate of 4.9 × 10^-3 (µg/m³)^-1. EPA estimates that, if an individual were to continuously breathe air containing hydrazine at an average of 0.0002 µg/m³ (2.0 x 10^-7 mg/m³) over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of breathing air containing this chemical. Similarly, EPA estimates that breathing air containing 0.002 µg/m³ (2.0 x 10^-6 mg/m³) would result in not greater than a one-in-a-hundred thousand increased chance of developing cancer, and air containing 0.02 µg/m³ (2.0 x 10^-5 mg/m³) would result in not greater than a one-in-ten thousand increased chance of developing cancer. For a detailed discussion of confidence in the potency estimates, please see IRIS. (4)
EPA has calculated an oral cancer slope factor of 3.0 (mg/kg/d)^-1. (4)

Physical Properties

The chemical formula for hydrazine is H₄N₂, and its molecular weight is 32.05 g/mol. (6)
Hydrazine occurs as a colorless, oily, flammable liquid that is miscible with water. (6,8)
Hydrazine has a penetrating odor, resembling that of ammonia, with an odor threshold of 3.7 ppm. (8,9)
The vapor pressure for hydrazine is 14.4 mm Hg at 25 °C, and its log octanol/water partition coefficient (log K_ow) is 0.08. (6)

Conversion Factors:
To convert concentrations in air (at 25 °C) from ppm to mg/m³: mg/m³ = (ppm) × (molecular weight of the compound)/(24.45). For hydrazine: 1 ppm = 1.31 mg/m³.

Health Data from Inhalation Exposure

ACGIH TLV--American Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effects.
LC₅₀ (Lethal Concentration₅₀)--A calculated concentration of a chemical in air to which exposure for a specific length of time is expected to cause death in 50% of a defined experimental animal population.
LOAEL--Lowest-observed-adverse-effect level
NIOSH IDLH--National Institute of Occupational Safety and Health's immediately dangerous to life or health limit; NIOSH recommended exposure limit to ensure that a worker can escape from an exposure condition that is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from the environment.
OSHA PEL--Occupational Safety and Health Administration's permissible exposure limit expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect averaged over a normal 8-h workday or a 40-h workweek.

The health and regulatory values cited in this factsheet were obtained in December 1999.
^a Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.
^b Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice. OSHA numbers are regulatory, whereas NIOSH and ACGIH numbers are advisory.
^c The LOAEL is from the critical study used as the basis for the CalEPA chronic reference exposure level.

References

M. Sittig. Handbook of Toxic and Hazardous Chemicals and Carcinogens. 2nd ed. Noyes Publications, Park Ridge, NJ. 1985.
World Health Organization. Environmental Health Criteria 68: Hydrazine. Geneva, Switzerland. 1987.
U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.
U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Hydrazine/Hydrazine Sulfate. National Center for Environmental Assessment, Office of Research and Development, Washington, DC. 1999.
U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.
U.S. Environmental Protection Agency. Health and Environmental Effects Profile for Hydrazine and Hydrazine Sulfate. EPA/600/x-84/332. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1984.
International Agency for Research on Cancer (IARC). IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man: Some Aromatic Amines, Hydrazine and Related Substances, N-Nitroso Compounds and Miscellaneous Alkylating Agents. Volume 4. World Health Organization, Lyon. 1974.
The Merck Index. An Encyclopedia of Chemicals, Drugs, and Biologicals. 11th ed. Ed. S. Budavari. Merck and Co. Inc., Rahway, NJ. 1989.
J.E. Amoore and E. Hautala. Odor as an aid to chemical safety: Odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. Journal of Applied Toxicology, 3(6):272-290. 1983.
Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Hydrazines. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1997.
California Environmental Protection Agency (CalEPA). Technical Support Document for the Determination of Noncancer Chronic Reference Exposure Levels. Draft for Public Comment. Office of Environmental Health Hazard Assessment, Berkeley, CA. 1997.
Occupational Safety and Health Administration (OSHA). Occupational Safety and Health Standards, Toxic and Hazardous Substances. Code of Federal Regulations. 29 CFR 1910.1000. 1998.
American Conference of Governmental Industrial Hygienists (ACGIH). 1999 TLVs and BEIs. Threshold Limit Values for Chemical Substances and Physical Agents, Biological Exposure Indices. Cincinnati, OH. 1999.
National Institute for Occupational Safety and Health (NIOSH). Pocket Guide to Chemical Hazards. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention. Cincinnati, OH. 1997.