What is rusty lettuce and is it edible?

According to chefs, the reddish-brown stuff that appears on lettuce is called 'rust'. It happens due to excess moisture during the storage process in the refrigerator.

What is rusty lettuce and is it edible?
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According to chefs, the reddish-brown stuff that appears on lettuce is called 'rust'. It happens due to excess moisture during the storage process in the refrigerator.