ARS | Publication request: Predicting Perchlorate Exposure in Milk From Concentrations in Dairy Feed

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 23, 2007
Publication Date: September 25, 2007
Citation: Rice, C., Baldwin, R.L., Abbott, L., Hapeman, C.J., Capuco, A.V., Le, A.N., Bialek Kalinski, K.M., Bannerman, D.D., Hare Jr, W.R., Paape, M.J. 2007. Predicting Perchlorate Exposure in Milk From Concentrations in Dairy Feed. Journal of Agricultural and Food Chemistry. 55:8806-8813.

Interpretive Summary: A nine-week long perchlorate dosing experiment of 20 Holstein dairy cows revealed that perchlorate uptake into the milk occurs as a linear relationship between the log of the concentration of perchlorate being consumed by the cows and the log of the resulting milk concentrations. Therefore a predictable dose response relationship between consumption of perchlorate and transfer to the milk was established. Food was analyzed on a weekly basis and found to vary in perchlorate content when ingredients are changed, e.g., alfalfa straw was changed to sudan grass midway in the dosing experiment and caused a 40% increase in perchlorate. Analyses of some major ingredients making up the cow's special diet revealed that 41% of the perchlorate came from corn silage, 24.3 % came from alfalfa hay and 11.7 % was supplied by sudan grass. Tabulating how much fluid milk is consumed by certain population groups (adults, children, and pregnant women) allowed comparisons with the National Research Council maximum allowable intake dose value. From this data it was determined that one and two year olds were likeliest to be affected by perchlorate in milk; however, the maximum exposure was low, less than 20% of the NRC reference dose.

Technical Abstract: Perchlorate has been detected in US milk samples from many different states. To attempt to manage this problem it is important to know the pathways for its possible accumulation. Data taken from a recently reported 9-week perchlorate experiment dosing 16 Holstein dairy cows allowed us to derive an equation for the dose-response relationship between perchlorate concentrations in feed/drinking water and its appearance in milk. Examination of background concentrations of perchlorate in the total mixed ration (TMR) fed in addition to the variable dose supplied to treated cows as a ruminal drip revealed that cows receive significant and variable exposure to perchlorate from the TMR. Weekly examination of the TMR disclosed that a minor change in ingredients midway through the experiment caused a significant (40%) change in perchlorate concentration. Analyses of the ingredients comprising the TMR revealed that 41.9% of the perchlorate came from corn silage, 22.9 % came from alfalfa hay and 11.7 % was supplied by sudan grass. Finally, USDA Food and Nutrition Survey data on fluid milk consumption were used to predict potential human perchlorate exposures from milk that contained concentrations of perchlorate observed in this dosing study. The study emphasized the importance of maintaining low concentrations of perchlorate in dairy feeds to minimize potential human exposure.