<unk>  are naturally occurring chemicals that can contaminate certain seafood. The seafood contaminated with these chemicals frequently looks, smells, and tastes normal. When humans eat such seafood, disease can result.
http://www.cdc.gov/ncidod/dbmd/diseaseinfo/marinetoxins_g.htm#whatsort
Marine toxins
Counterfeit drug
Toxic metal
Food additive
Neurotoxin
Hazardous drugs
Mucolytic agent
Allergen