What are Nitrogen Mustards?

Nitrogen mustards are chemicals that cause severe skin blisters and damage by attacking cells' DNA. They are colourless to pale yellow, oily liquids that don’t evaporate quickly. They are often referred to by their military names: HN-1, HN-2, and HN-3.

HN-3: Pure HN-3 doesn’t have a smell, but some say it can smell like buttered almonds. It is the most stable but breaks down at temperatures over 256°C. It doesn’t evaporate easily and doesn’t mix with water.

HN-1: Has a slight fishy or musty smell. It doesn’t mix well with water but can dissolve in substances like acetone. It breaks down when heated above 194°C.

HN-2: Smells fruity in large amounts and soapy in smaller amounts. It behaves like HN-1 in terms of solubility.

What are Nitrogen Mustards used for?

HN-1 was originally created to treat warts, but it was later found to have potential use in chemical warfare.

HN-2, initially developed for military purposes, was later used in cancer treatments. However, it has since been replaced by other, more effective drugs.

HN-3 was designed specifically for military use as a chemical weapon.

Nitrogen Mustard Hazards

Sources of exposure

Air Exposure: If nitrogen mustards are released as a vapour, you could be exposed by breathing it in or through contact with your skin or eyes.

Water Exposure: If released in water, exposure can occur through drinking contaminated water or getting it on your skin.

Direct Contact: You could also be exposed by directly touching liquid nitrogen mustards.

Settling: Since nitrogen mustard vapour is heavier than air, it tends to settle in low-lying areas.

Routes of Exposure

Ingestion: Although rare, swallowing nitrogen mustard can cause burns in the digestive system and lead to absorption throughout the body.

Inhalation: Breathing in nitrogen mustard vapour is a key way people can be exposed. The lethal concentration for 50% of the population (LCt50) is 1,500 mg-min/m³ for HN-1 and HN-3 and 3,000 mg-min/m³ for HN-2.

Skin/Eye Contact: Exposure to vapour can irritate the eyes, skin, and mucous membranes, even at low levels. Direct contact with liquid nitrogen mustard can cause burns. The median incapacitating dose for the eyes is 100 mg-min/m³ for HN-2 and 200 mg-min/m³ for HN-1 and HN-3. Nitrogen mustard can also be absorbed through the skin or eyes, leading to further toxicity in the body.

Health Effects

Acute Effects

• Central Nervous System: High doses can cause tremors, seizures, lack of coordination, and coma.
• Respiratory System: Damage to the airway lining starts within hours and can worsen over several days. Symptoms include pain, cough, and breathing difficulty, though fluid in the lungs is rare.
• Gastrointestinal System: Swallowing nitrogen mustard can cause chemical burns in the digestive system, along with nausea, vomiting, and bloody diarrhoea.
• Eyes: Exposure can lead to intense eye inflammation, pain, swelling, tearing, sensitivity to light, and potentially blindness at high concentrations.
• Skin: Skin exposure causes redness and blisters, with more severe exposure leading to second- or third-degree burns.
• Hematopoietic System: Absorption into the body can suppress bone marrow, increasing the risk of infection, bleeding, and anaemia.
• Delayed Effects: Chemotherapy using HN-2 has been linked to menstrual issues, hair loss, hearing problems, liver damage, and fertility issues.
• Potential Sequelae: After exposure to large amounts of nitrogen mustards, chronic respiratory and eye problems can persist. Swallowing formalin, a related chemical, can cause severe damage to the esophagus and stomach lining.

Chronic Effects

In animal studies, long-term or repeated exposure to nitrogen mustards has led to cancer, developmental issues, reproductive problems, and liver damage. These effects build up over time because the body cannot naturally get rid of nitrogen mustards.

Carcinogenicity

The International Agency for Research on Cancer (IARC) classifies nitrogen mustards as "probably carcinogenic to humans" (Group 2A). There is some evidence linking it to leukaemia in humans, and studies have shown it can cause cancers in the lungs, liver, uterus, and large intestine in animals.

Reproductive/Developmental Effects

Nitrogen mustards may reduce fertility. Some reports have connected HN-2 treatment with birth defects in humans. Animal studies have shown that nitrogen mustards can cause developmental problems.

Nitrogen Mustards Safety

First Aid Measures

• Eyes: If someone gets nitrogen mustard in their eyes, remove contact lenses if present, and flush the eyes with water or saline for 20 to 30 minutes. Call a hospital or poison control immediately. Don’t apply ointments or medications without a doctor’s instructions. Even if no symptoms appear, the person must be taken to a hospital immediately.
• Skin: Immediately rinse the affected skin with water while removing contaminated clothing. Wash the skin with soap and water. Call a hospital or poison control right away, even if there are no visible symptoms. The person should be taken to the hospital immediately.
• Inhalation: Leave the contaminated area immediately and breathe fresh air. Call a doctor and be ready to take the person to the hospital, even if they don’t show symptoms like coughing or chest pain. Rescuers should use a Self-Contained Breathing Apparatus (SCBA) or other protective gear.
• Ingestion: Do not induce vomiting, as the chemical can cause burns and may enter the lungs during vomiting. If the person is conscious, give them 1-2 glasses of water and call poison control or a hospital immediately. If they are unconscious or having seizures, do not give anything by mouth and lay them on their side. The person must be taken to the hospital immediately.
• Other Considerations: Since nitrogen mustards are known or suspected carcinogens, contact a physician for advice regarding the possible long-term health effects and potential recommendation for medical monitoring. Recommendations from the physician will depend upon the specific compound, its chemical, physical and toxicity properties, the exposure level, the length of exposure, and the route of exposure. (NTP, 1992)

Pre-Hospital Management

• Contamination Risk: People who have nitrogen mustard on their skin or clothes can spread it to others by direct contact or by vapours.
• No Antidote: There is no antidote for nitrogen mustard poisoning. Immediate decontamination of exposed areas is the only way to reduce damage.

Nitrogen Mustards Safety Handling

Hot Zone

• Rescuers need proper training and equipment before entering the contaminated area. If equipment is unavailable, or if the rescuers have not been trained in its use, call for assistance from the U.S. Soldier and Biological Chemical Command—Edgewood Research Development and Engineering Centre.
  • Rescuer Protection: Nitrogen mustard vapour and liquid are readily absorbed by inhalation and ocular and dermal contact.
  • Respiratory Protection: Use a pressure-demand self-contained breathing apparatus (SCBA) for any exposure.
  • Skin and Eye Protection: Wear personal protective equipment (PPE) and butyl rubber gloves when dealing with nitrogen mustard.
• Triage in Multi-Casualty Situations: Casualties are categorised by the severity of their symptoms and injury. All victims must be decontaminated before transport. Those exposed should be observed for at least 6 hours, even if symptoms haven’t appeared. If symptoms develop, patients should be taken to the hospital for evaluation.

Chemical Dangers

• HN-1: It starts to corrode iron alloys at 65°C (149°F). Hydrolysis of HN-1 can produce toxic by-products, and it may release flammable hydrogen gas when in contact with metals.

Explosion Hazards

• Fire and Explosion: Nitrogen mustards do not pose an immediate fire or explosion risk, but heating can create explosive vapors. Containers may explode when heated.

Fire Fighting Information

• Combustibility: HN-1 is combustible but doesn’t ignite easily. Fire can produce toxic and corrosive gases.
• Small Fires: Use dry chemical, carbon dioxide, or water spray.
• Large Fires: Use alcohol-resistant foam, dry chemical, or water spray. Move containers from fire areas if it’s safe. Dike fire control water for later disposal; do not scatter the material. Avoid methods that will cause splashing or spreading. 
• Fire involving tanks or car/trailer loads: Use unmanned hoses or monitor nozzles and keep maximum distance. Do not get water inside containers. Cool containers with flooding quantities of water until well after the fire is out. Withdraw immediately in case of rising sound from venting safety devices or discolouration of tanks. Always stay away from tanks engulfed in fire.
• Runoff: Runoff water from firefighting may be toxic and cause pollution. Control and dispose of it properly if possible.

Regulations

United States

No occupational exposure limits have been established for nitrogen mustard. However, the United States Military has established a TLV (threshold limit value) of 0.003mg/m3.