Contamination by Heavy Metals

• In areas where subsistence foragers rely on fish and seafood for survival, heavy metals from industrial, domestic, and other man-made activities can accumulate in fish. For instance, species of carp in the River Ravi, Pakistan, show increased levels of cadmium and chromium.
  
  

Contamination by Oil Operations

• Oil spills, leakages, and byproducts from processing plants can produce contaminants in fish. The recent Gulf oil spill threatened possible buildup of polycyclic aromatic hydrocarbons in fish and shellfish. The crude oil effluent operations on the Qua-Iboe River in Nigeria introduce neurotoxic chemicals that fish take up and pass along the food chain.
  
  

Mycotoxins (Mold)

• Molds in the genera Aspergillus, Alternaria, Claviceps, Fusarium, Penicillium and Stachybotrys can produce toxic substances in crop plants both pre- and post-harvest that can have serious health effects on the people who consume them. Examples are ergot in wheat and aflatoxins from Aspergillus.
  
  

Bacterial Contamination

• Animal foodstuffs and crops can be contaminated from untreated animal and human waste used to fertilize the crops, or are contaminated in storage or transport. Serious illness can result.