Fertilizer’s Dangerous Ingredient: The Health Hazards of Ammonia Exposure

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A blast at a fertilizer plant in the small town of West, Texas, raises concerns about exposure to anhydrous ammonia, a potentially deadly gas that is stored at high pressure.

Investigators are still determining whether the explosion, which killed 15 people and injured more than 160, was the result of criminal activity or simply an industrial accident. But because the plant relied on anhydrous (without water) ammonia, a colorless, strong-smelling nitrogen-based gas, as the primary ingredient in manufacturing farming fertilizer, authorities are concerned about toxic fumes released from the site. According to the Dallas Morning News, the facility reportedly stored as much as 54,000 lb. of anhydrous ammonia on-site. D.L. Wilson, a state trooper with the Texas Department of Public Safety, told reporters that half of the town’s 2,700 residents had been evacuated as a precaution.

A smaller fire at the plant apparently spread and caused an explosion when the flames came in contact with some of the tanks containing chemicals for the fertilizer.

(PHOTOS: Texas Town Rocked by Fertilizer-Plant Explosion)

If not handled properly, the U.S. Centers for Disease Control and Prevention says, anhydrous ammonia can cause eye, nose and throat irritation, breathing difficulty and burns. Although the ammonia is colorless, it carries a strong odor, which health experts say is the simplest way for people to know if they have been exposed.

“Have you ever opened a bottle of household ammonia? It’s the same stuff,” says Neal Langerman, a chemical-safety consultant for Advanced Chemical Safety in San Diego and officer of the division of health and safety at the American Chemical Society. “The difference between the stuff that was involved in that fire and the stuff in the bottle is the stuff in the bottle is diluted in water and this was anhydrous ammonia, dry ammonia. Just more concentrated. It is extremely irritating, you start coughing and sneezing, and the first thing you want to do is get the hell out of there.”

The odor makes it fairly easy for Fire Department responders to monitor for presence of the gas, says Langerman. And so far, Waco police say the air in West does not pose a health threat:

The fires, as well as rains that followed, may have contained some of the ammonia released from the plant. “A large fraction of the ammonia that was in that [storage] tank burned off because it is a flammable gas,” says Langerman. “When it burns, it forms of a whole variety of oxides of nitrogen that pretty quickly dissipate in the atmosphere.” Add to that the rainfall that drenched West after the blast, and he says it’s likely that most residents will be spared from health problems related to ammonia exposure. “The residual will pretty rapidly react with any atmospheric moisture, and it is raining there right now. The rain will flush it out of the air and very quickly dilute it out and into the soil where it will actually act as fertilizer. The rain not only helped to put out the fires, but it also washed any of the residual ammonia out of the atmosphere so it is not going to have a health impact on the community.”

(MORE: Crews Seek Survivors, Bodies After Texas Blast)

For people who have been exposed, burns and irritation from the gas are likely to be the most common symptoms. Eye irritation can be treated by flushing with water while severe breathing or asthma-like symptoms can be addressed with inhalers, inhaled steroids or oxygen if necessary. Often, says Dr. Ken Spaeth, the director of Occupational and Environmental Medicine center in the Department of Population Health at the North Shore University Hospital in Manhasset, N.Y., symptoms resolve without any treatment. “If there is a silver lining, it is that it is not likely that exposure would happen without the person knowing. If they didn’t smell the ammonia smell, which is very distinctive, it is not very likely they had any kind of exposure. If they did and they are feeling O.K., it is quite likely they are fine and there is nothing to worry about,” says Spaeth.

The U.S. Chemical Safety Board has sent a large investigative team to the scene, and the Texas Commission on Environmental Quality is monitoring air quality for any potentially harmful elevations in ammonia levels.