Molybdenum is an essential heavy metal. Toxic effects of molybdenum in cattle were described for the first time in 1938. The maximum immission values (MI values) for molybdenum listed in this standard are designed to protect farm animals and the food derived from them. Maximum immission values for molybdenum have been calculated on the basis of the results of livestock feed trials. In these experiments, the animals received fodder to which sodium or ammonium molybdate had been added or whose sodium or ammonium molybdate content was naturally high or elevated as a result of ambient air pollution. MI values can thus be specified only for those animals for which corresponding data is available. In this case cows, young cattle, beef cattle, sheep, goats, horses, fattening pigs and broiler hens. Reductions in performance, reproductive disorders, impairment of health and biochemical changes were the criteria used to determine the effect of molybdenum on farm animals. This standard applies in particular to all people who directly and indirectly handle or come into contact with farm animals and the food products derived from them. The standard is part of the series of standards "Maximum immission values to protect farm animals and the food derived from them". That regards pollutants for which generally there is no animal feed regulation.