New toxic cloud on Tucson freeway

An accident on Interstate 10 Tuesday in Tucson, Arizona, forced authorities to close part of the highway and issue a shelter-in-place order after a hazardous materials spill.

A tanker truck that was involved in an accident spilled a large amount of nitric acid on the road, creating a dense toxic cloud. Arizona authorities shut down the highway, initially until 6 a.m. Wednesday and issued a shelter-in-place order for the surrounding areas.

Authorities asked people within a one-mile radius of the accident to take shelter in their homes. People were also advised to turn off heaters and air conditioners that bring in outside air. The shelter-in-place order was finally lifted late Tuesday afternoon.

What is nitric acid?

Nitric acid is a viscous, corrosive liquid that can cause severe burns to living organisms. It is a laboratory reagent which is used to manufacture explosives such as nitroglycerin and trinitrotoluene (TNT). It is also used to make fertilizers such as ammonium nitrate. It has additional uses in metallurgy and refining and is also a component of acid rain.