Toxic environmental contaminants, such as polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), and polychlorinated biphenyls (PCBs) occur differentially in animal tissues. This study examined paired liver and muscle tissues from the same animals, reducing the uncertainty inherent in other studies that source tissues from different animals. Investigations were carried out on cattle and sheep from two separate herds in Southern Italy. As all animals experienced the same environmental impacts, husbandry, and feed regimes, contaminant distribution between tissues would result from physiological considerations, which would also allow for better examination of the effects of age. In both investigations, PCDD/F and PCB concentrations were significantly higher (p 95% in cattle tissues and 78% and 67% in sheep muscle and liver, respectively. A majority of liver samples exceeded regulated maximum limits, and the herds were excluded from the food supply. Subsequent regional monitoring showed regulatory compliance of cattle/sheep meat and liver, but prominence of PCB-TEQ persisted. Concentrations of both contaminants declined strongly in the tissues of both species with increasing age of juveniles but stabilized in older animals (>one year in sheep; 2/3 years in cattle). Although weight gain might partly account for this pattern, the initial decline may also relate to inadequate levels of CYP enzymes in the youngest juveniles, but this would need to be confirmed in both species by targeted toxicokinetic studies during this perinatal period. The expression of these detoxifying enzymes is reported to rise rapidly with increasing postnatal age in many animal species, including sheep.
Ceci et al. (2026) studied this question.