Hydrazine Use in the Military: Health Effects, Exposure Limits, and Protection Guidelines

Hydrazine (N₂H₂) is an inorganic compound used in industrial applications. In the military, hydrazine is used in various rocket fuels and as a propellant onboard space vehicles, such as the NASA Dawn probe to Ceres and Vesta. In addition, the F-16 fighter jet, NASA Space Shuttle, and U-2 Spy Plane use hydrazine to fuel their emergency power units.¹

The hydrazine molecule consists of two co-joined nitrogen atoms plus four peripheral hydrogen atoms. In its anhydrous (waterless) form, hydrazine is a colorless liquid that smells a bit like ammonia because it’s made of two ammonia molecules joined together, less two hydrogen atoms.²

 

Hydrazine at a Glance

 

Health Effects of Hydrazine

Hydrazine is an extremely toxic and dangerously unstable liquid that produces symptoms as extreme as tumors and seizures.³

Hydrazine can enter the human body through the skin and eyes, as well as being inhaled and ingested.⁴ Exposure to hydrazine can cause skin irritation/contact dermatitis and burning, irritation to the eyes/nose/throat, nausea/vomiting, shortness of breath, pulmonary edema, headache, dizziness, central nervous system depression, lethargy, temporary blindness, seizures and coma.

Exposure can also cause damage to the liver, kidneys and central nervous system^4,5 and is documented as a strong skin sensitizer – meaning that skin contact with hydrazine will lead to an allergic response.⁶

The National Institute for Occupational Safety and Health (NIOSH)⁷ lists hydrazine as a “potential occupational carcinogen.”  The National Toxicology Program (NTP) finds that it is “reasonably anticipated to be a human carcinogen.”  The American Conference of Governmental Industrial Hygienists (ACGIH) grades hydrazine as “A3 – confirmed animal carcinogen with unknown relevance to humans.”  The U.S. Environmental Protection Agency (EPA) grades it as “B2 – a probable human carcinogen based on animal study evidence.”⁸

The International Agency for Research on Cancer (IARC) rates hydrazine as “2A – probably carcinogenic to humans” with a positive association observed between hydrazine exposure and lung cancer.⁹

 

Treatment for Hydrazine Exposure

In the event of a hydrazine exposure-related emergency, NIOSH recommends removing contaminated clothing immediately, washing skin with soap and water, and for eye exposure removing contact lenses and flushing eyes with water for at least 15 minutes.

NIOSH also recommends that anyone with potential hydrazine exposure seek medical attention as soon as possible.⁴ There are no specific post-exposure laboratory or medical imaging recommendations, and the medical workup may depend on the type and severity of symptoms.

The World Health Organization (WHO) recommends potential exposures be treated symptomatically with special attention given to potential lung and liver damage. Past cases of hydrazine exposure have documented success with pyridoxine (vitamin B6) treatment.⁶

 

Permissible Exposure Levels

Because of the toxic effects of hydrazine, the permissible exposure level is extremely low:

• NIOSH Recommended Exposure Limit (REL): 0.03 ppm (0.04 mg/m³) 2-hour ceiling⁸
• OSHA Permissible Exposure Limit (PEL): 1 ppm (1.3 mg/m³) 8-hour Time Weighted Average⁸
• ACGIH Threshold Limit Value (TLV): 0.01 ppm (0.013 mg/m³) 8-hour Time Weighted Average⁸

Because the odor threshold for hydrazine is 3.7 ppm, if a person is able to smell an ammonia-like odor, the environment is probably over the exposure limit. However, odor thresholds vary greatly from person to person and should not be used to determine potentially hazardous exposures.⁹

The USAF uses the Short-Term Public Emergency Exposure Guideline (SPEGL), developed by the National Academy of Science Committee on Toxicology, for non-routine exposures of the general public. It does not apply to occupational exposures. SPEGL defines the acceptable peak concentration for unpredicted, single, short-term emergency exposures of the general public and rare exposures in a worker’s lifetime. For hydrazine the 1-hour SPEGL is 2 ppm, with a 24-hour SPEGL of 0.08 ppm.¹⁰

 

Guidelines for Handling Hydrazine

Common controls for hydrazine handling include process enclosure, local exhaust ventilation, and personal protective equipment (PPE).⁴ Guidelines for PPE include non-permeable gloves and clothing, indirect-vent splash resistant goggles, face shield, and in some cases a respirator.⁹  In cases where respirators are needed, proper respirator selection and a complete respiratory protection program consistent with OSHA guidelines should be implemented.⁴

For USAF personnel, Air Force Occupational Safety and Health (AFOSH) Standard 48-8, Attachment 8, reviews the considerations for occupational exposure to hydrazine in missile, aircraft and spacecraft systems.

Specific guidance for exposure response includes mandatory emergency shower and eyewash stations and a process for decontaminating protective clothing. The guidance also assigns responsibilities and requirements for proper PPE, employee training, medical surveillance, and emergency response.¹⁰

In general, USAF bases that use hydrazine have specific regulations governing local requirements for safe hydrazine use and emergency response.

 

Safe Storage of Hydrazine

Hydrazine should be stored in tightly closed containers in a cool, dry, well-ventilated place. Containers that are opened must be carefully resealed and kept upright to prevent leakage. It is recommended that the area be secured to restrict access, such as a lockable chemical cupboard.

All sources of ignition – such as smoking or mobile phone use – should be eliminated. Take measures to prevent the build-up of electrostatic charge and use non-sparking tools and intrinsically safe equipment in the area. Keep hydrazine away from oxidizing agents, oxygen, copper, zinc and organic materials.

Installation of a hydrazine gas monitor can increase safety by detecting leaks from containers that are defective or have not been properly sealed, thus eliminating the risk of accidental exposure.  Depending on the size of the storage area, there could be more or less justification for this.

 

Hydrazine Monitoring and Detection Solutions

Area monitoring 

Hydrazine DrägerTubes^®

 

Personal Protection

Dräger X-am^® 5100

Fixed gas detection

Dräger developed the following hydrazine detection devices as a result of a request years ago by the U.S. space program.

 

 

 

Dräger Polytron^® 8100 EC

 

 

Personal Protective Equipment (PPE)

Dräger also has a line of protective equipment including the PSS^® 7000/FPS^® 7000 SCBA for breathing protection and the CPS 5900 chemical protective suit to protect workers in and around military facilities that use hydrazine from harm.

References

1. Suggs, HJ; Luskus, LJ; Kilian, HJ; Mokry, JW (1979). “Exhaust Gas Composition of the F-16 Emergency Power Unit”(technical report). USAF. SAM-TR-79-2. Archived from the originalon 4 Mar 2016. Retrieved 23 Jan 2019.
2. 2. https://eic.rsc.org/magnificent-molecules/hydrazine/2000023.article.
3. www.chm.bris.ac.uk/motm/hydrazine/hydrazineh.htm
4. “Occupational Safety and Health Guideline for Hydrazine – Potential Human Carcinogen”(PDF). NIOSH. 1988. Retrieved 23 Nov 2018.
5. “Hydrazine 302-01-2″(PDF). US EPA. Retrieved 23 Nov 2018.
6. International Programme on Chemical Safety – Health and Safety Guide No. 56 – Hydrazine”. IPCS INCHEM. Geneva: WHO. 1991. Retrieved 24 Nov 2018.
7. “NIOSH Guide – Hydrazine”. Centers for Disease Control. Retrieved 16 Aug 2012.
8. “Occupational Chemical Database – Hydrazine”. www.osha.gov. OSHA. Retrieved 24 Nov 2018.
9. “Hazardous Substance Fact Sheet – Hydrazine”(PDF). New Jersey Department of Public Health. Nov 2009. Retrieved 23 Nov 2018.
10. “Air Force Occupational Safety and Health (AFOSH) Standard 48-8”(PDF). USAF. 1 Sep 1997. Retrieved 23 Nov 2018.