anhydrous ammonia

Mike Stone / Reuters

The deadly explosion at a fertilizer plant in West, Texas is prompting questions about regulatory oversight there.  In Iowa, officials say fertilizer is only produced at a handful of sites across the state, but many others store it.

A U.S. Environmental Protection Agency spokesman says the agency regulates 700 retail facilities in Iowa that store more than 10,000 pounds of anhydrous ammonia fertilizer, an ingredient that can be particularly volatile.