Grazing animals could possibly ingest residues of phenoxy compounds, such as 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) or their impurities from pasture or rangelands, when these compounds are applied to control broadleaf weeds and brush (LENG 1972). The determination of 2,4,5-T bovine milk has previously been reported but nothing has been reported on the possible presence of the toxic impurity 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This surveillance study was undertaken to determine if low level concentrations of TCDD could be detected in milk from cows grazing on grass where 2,4,5-T had been applied following normal agricultural practice.
