Story highlights On Tuesday, the Pueblo Chemical Depot will begin to destroy the largest stockpile of chemical weapons in the U.S.

Here are nine facts to know about chemical weapons

(CNN) The Pueblo Chemical Depot will begin destroying the United States' largest remaining stockpile of chemical weapons Tuesday in southern Colorado. There are 2,611 tons of World War II-era mustard agent at the Pueblo depot.

Here are nine things to know about these chemical weapons and how we got here:

1. First use: April 22 marks the 100th anniversary of the first use of chemical weapons in modern warfare at Ypres in Belgium.

2. Huge production: From World War I to 1968, the United States produced nearly 40,000 tons of chemical weapons. These weapons were either nerve agents or blister agents.

3. Scary stuff: Mustard agent is a blister agent, which can cause skin redness and itching, eye irritation, scarring, and an increased risk for lung and respiratory cancer.

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