Milk and Whole Blood Surveillance Following Lethal and Sublethal Lead Intoxication in a Michigan Dairy Herd

Lead contamination in the environment affects both humans and animals. Even with the decrease in manufactured items containing lead, contaminants persist in the landscape and may enter the food supply through animal products. In cattle, lead poisoning is associated with economic losses due to mortality and treatment costs and poses a health risk to consumers. A dairy herd was exposed to lead through feed that was contaminated with a 12-volt battery from a mixer wagon. Lead concentrations in blood and milk samples were examined over 289 days. A 2 ng/mL threshold for lead in milk was utilized to release affected cows back into the milking herd. After 289 days of surveillance, one of the five cows under milk surveillance was yet to meet this threshold. Milk lead concentrations greater than 2 ng/mL can result in lead intakes exceeding 2.2 µg/day limits for young children in the highest milk consumption group. Lead is not routinely assessed in fluid milk as a quality control step prior to processing in the United States, yet interstate commerce justifies a need for harmonized protocols for routine lead surveillance of the general milk supply and enhanced surveillance and quarantine for known food-animal exposures.