A train lost 60,000 pounds of ammonium nitrate

Jul 03, 2023

Officials believe a railcar malfunction is to blame, not bad actors.

By Andrew Paul | Published May 22, 2023 2:10 PM EDT

An estimated 30 tons of highly volatile ammonium nitrate disappeared from a railcar traveling last month between Wyoming and the Mojave Desert in California. Frequently used as a fertilizer, the compound is also infamous for its role in the deadly 1995 Oklahoma City bombing, as well as a massive 2020 explosion in Beirut, Lebanon, that killed over 200 people. In this instance, however, multiple reports indicate Union Pacific railway officials believe the cargo accidentally leaked out of "the bottom gate on the railcar" during its two-week journey across the western US.

According to The New York Times, a Union Pacific spokesperson explained that the fertilizer—transported in pellet form within a covered hopper car akin to coal shipments—is designed for ground application and quick soil absorption, and "should pose no risk to public health or the environment." The shipment belonged to an explosives manufacturer, Dyno Nobel, whose representatives also told the Times they do not currently suspect "criminal or malicious activity" behind the disappearance. Union Pacific is reportedly in the "early stages" of its investigation, while the Federal Railroad Administration and the California Public Utilities Commission are also conducting their own reviews of the incident.

[Related: Toxic train derailment in East Palestine, OH highlights issues facing America's railways .]

"The railcar was sealed when it left the Cheyenne facility, and the seals were still intact when it arrived in Saltdale. The initial assessment is that a leak through the bottom gate on the railcar may have developed in transit," a Dyno Nobel spokesperson said in a statement.

Although ammonium nitrate is relatively harmless on its own, its addition to a fuel source combined with heat and pressure make for an extremely powerful explosion. This can often prove useful—as is the case with a compound called ANFO (ammonium nitrate/fuel oil), which miners use to clear large rock formations. However, ammonium nitrate is also a go-to chemical for illegal homemade explosives and bombs. As California radio outlet KQED explains, Congress passed a law in 2007 on the regulation and transfer of ammonium nitrate to prevent its misuse by bad actors. In 2011, the Department of Homeland Security proposed additional regulations, but never formally adopted them.

News of the rail incident comes only a few months after a Norfolk Southern freight train derailed in East Palestine, Ohio, resulting in a temporary, mandatory evacuation order for thousands of residents. The release of toxic chemicals such as vinyl chloride gas and a carcinogen called ethylhexyl acrylate resulted in numerous reports of physical and respiratory issues such as headaches, coughing, and acute bronchitis.

Andrew Paul is Popular Science's staff writer covering tech news. Previously, he was a regular contributor to The A.V. Club and Input, and has had recent work also featured by Rolling Stone, Fangoria, GQ, Slate, NBC, as well as McSweeney's Internet Tendency. He lives outside Indianapolis.