Heavy metals also accumulate in the food chain. Cadmium was found in all kidney samples. The maximum permitted level for cadmium was exceeded in three of the 204 kidney samples, once in a pig and twice in milking cows. The kidneys of horses contain about ten times as much cadmium as the kidneys of other animals. This is because horses are often slaughtered only when they are quite old, and have thus been exposed to the substance for almost the full life span of a horse.
Moreover some of the horses slaughtered in the Netherlands originate from heavily contaminated areas in Eastern Europe. The cadmium levels in horse kidneys in 1997 ranged from about 2 to 46 mg/kg. Cattle kidneys may now contain more than 2.5 mg/kg of cadmium. However there is no legal limit for horses. The maximum permitted levels of lead and mercury were not exceeded in any of the kidney samples.