Sulfur Mustard and Cancer

This page is for veterans, their families, and anyone curious about mustard gas. It covers what the chemical is, who was exposed, which cancers it causes, and what the VA offers.

Sulfur mustard is a vesicant. That means it blisters whatever it touches: skin, eyes, and the lining of the airways. Its CAS number, a chemical ID code, is 505-60-2. Chemists call it bis(2-chloroethyl) sulfide. Most people know it as mustard gas.

The name is misleading. At room temperature it is not a gas. It is an oily liquid, clear to yellow, with a sweet odor. The VA says it is yellow-brown and smells of mustard, garlic, or horseradish. It melts at 13 to 14 degrees Celsius and boils at about 215 to 217. It barely dissolves in water. It dissolves very well in fats.

The VA notes that mustard gas belongs to a class of compounds that includes sulfur mustard and nitrogen mustard.

The history is short and specific:

• World War I, its first use in chemical warfare.
• Ethiopia, in 1936.
• The Iran-Iraq war, from 1984 to 1988.
• Production plants, where workers made and handled it.
• Weapons testing programs run by governments on their own troops.

Sulfur mustard was even tested as a cancer drug. It failed, because it was far too toxic to use.

This part is often left out, and it matters for veterans and their families.

In the 1940s, the Department of Defense recruited "volunteer soldier" subjects. The goal was to test protective clothing, ointments, and gear. The VA says about 60,000 military personnel took part.

One common design was a patch or drop test. A drop of agent went on the arm, to see how well an ointment worked. NTP puts the patch and drop test group at 15,000 to 60,000 soldiers and sailors.

About 4,000 soldiers went through severe, full-body exposures. Some of those happened in field exercises. In chamber tests, volunteers wore masks and gear inside a gas chamber. Sessions ran an hour or more, daily or every other day, until the gear failed. Failure was measured by moderate to intense chemical burns on the skin.

The scale in the earlier war was larger still. As many as 28,000 members of the American Expeditionary Forces were exposed in World War I. Levels were seldom lethal, because the agent scattered on the battlefield.

The VA says the U.S. Army provides medical care to eligible test participants through military treatment facilities. The number for questions is 1-800-984-8523. For VA benefits, call 800-827-1000 or ask your local VA Environmental Health Coordinator.

NTP lists mustard gas as known to be a human carcinogen. The basis is sufficient evidence in humans, not an inference from animals. It has been on the list since the first Report on Carcinogens in 1980.

Several studies found raised rates of lung and other airway cancer. Those studies covered people exposed in military use or at work. The dose pattern is there too. Among production workers, airway cancer risk was higher in people exposed for longer.

The clearest single study followed workers who made mustard gas in England in World War II. It found significant excesses of four cancers. Those were laryngeal, pharyngeal, upper-airway, and lung cancer. Our page on lung cancer covers how that cancer is found and staged.

Animal work fits the human pattern. Mustard gas caused cancer in mice of both sexes. Breathed in or injected into a vein, it caused lung tumors. Injected under the skin, it caused tumors at the injection site.

The mechanism is blunt. Mustard gas is an alkylating agent. That means it sticks chemical groups straight onto DNA. NTP reports genetic damage in every system where it was tested. In mice, it bound tightly to DNA, RNA, and protein.

The VA may grant service connection by presumption. That means a veteran does not have to prove the link case by case. The VA says the rule applies to veterans with full-body mustard gas or lewisite exposure.

Cancers the VA lists:

• Leukemia.
• Nasopharyngeal cancer.
• Laryngeal cancer.
• Lung cancer.
• Skin cancer.

Other conditions the VA lists:

• Chronic eye conditions: conjunctivitis, keratitis, and corneal scarring.
• Chronic breathing conditions: laryngitis, bronchitis, emphysema, asthma, and COPD.

The VA has exact rules for each condition. Ask a VA Environmental Health Coordinator or call the VA before you assume a condition is or is not covered. You can also write to mustardgas@vba.va.gov.

NTP says that by the end of World War I, daily U.S. production had reached about 18,000 kilograms. The country kept making and storing it until 1968, building up more than 34 million pounds.

NTP says the United States no longer produces, imports, or exports mustard gas. Its profile, written years ago, described aging stockpiles at eight Army bases that were scheduled for destruction. We have not confirmed the current status of those stockpiles in an approved source, so this page does not report it.

NTP says the general population is typically not exposed. The main routes are breathing it in and skin contact. People may also be exposed to residue from disposal sites used years or decades ago if those sites are disturbed. Small amounts are still used in research as a model for alkylating agents.

For anyone with a documented exposure, two steps are practical. One is a VA Environmental Health Coordinator evaluation. The other is attention to airway symptoms, such as hoarseness or a cough that will not settle. For how these hazard labels work in general, see our explainers on what a carcinogen is and hazard versus risk.

• National Toxicology Program, Report on Carcinogens, Fifteenth Edition: Mustard Gas, accessed August 6, 2026 (re-checked October 2, 2026)
• U.S. Department of Veterans Affairs, Mustard Gas — Public Health, last updated April 16, 2026, accessed August 6, 2026