Elevated TCDD in chicken eggs and farm-raised catfish fed a diet with ballclay from a southern United States mine

The U.S. Food and Drug Administration (FDA) terminated the use of ball clay from a mine in Mississippi as an additive in animal feed after discovering nanogram per gram concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2 ,3,7,8-TCDD). The FDA collected chicken eggs and farm-raised catfish in aff ected areas and throughout the remaining continental United States to asses s levels of 2,3,7,8-TCDD. A new method using quadrupole ion storage tandem- in-time mass spectrometry (QISTMS) measured the 2,3,7,8-TCDD levels in 42 c atfish fillet composites, 3 Tilapia fillet composites, 46 chicken egg sampl es, and 6 chicken feeds. Six catfish composites and 20 egg samples had 2,3, 7,8-TCDD concentrations significantly above 1.0 pg/g wet weight of fillet o r whole egg. Farm-raised catfish not exposed to feed containing ball clay h ad a mean 2,3,7,8-TCDD concentration of 0.12 pg/g. The TCDD isomer pattern in ball clay differed from the TCDD isomer pattern in a fly ash sample and from the "chick edema factor" TCDD pattern in a sample of reference toxic f at used as a feed ingredient in the 1950s.