What are they?
A heavy metal is any metallic chemical element that has a relatively high density and is toxic or poisonous at low concentrations. While not all heavy metals are highly toxic, some are. Some include Arsenic, Lead, Cadmium and Mercury.
Like other food products, pet foods and their constituents can be exposed to heavy metals through industrial wastes, agricultural runoff, chemical treatments and more. Some ingredients are more likely to be exposed than others and therefore products with higher ratios of those ingredient theoretically are more likely to contain increased levels of heavy metals.
Heavy metal exposure can lead to a variety of symptoms in pets, such as inflammatory bowel, nausea and vomiting, diarrhea, blindness, respiratory distress, behavioral changes, muscle weakness, and nerve damage.