FUNCTIONAL-ASPECTS OF DEVELOPMENTAL TOXICITY OF POLYHALOGENATED AROMATIC-HYDROCARBONS IN EXPERIMENTAL-ANIMALS AND HUMAN INFANTS

A scientific evaluation was made of functional aspects of developmenta l toxicity of polychlorinated biphenyls (PCBs), polychlorinated dibenz o-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in exper imental animals and in human infants. Persistent neurobehavioral, repr oductive and endocrine alterations were observed in experimental anima ls, following in utero and lactational exposure to PCBs, PCDDs and PCD Fs. The lowest observable adverse effect levels (LOAELs) for developme ntal neurobehavioral and reproduction endpoints, based on body burden of TCDD-toxic equivalents (TEQs) in animals, are within the range of c urrent background human body burdens. Relatively subtle adverse effect s on neurobehavioral development and thyroid hormone alterations have also been observed in infants and children exposed to background level s. Exclusive use of the toxic equivalency factor (TEF) approach may un derestimate the risk of neurodevelopmental effects, because both Ah re ceptor dependent and independent mechanisms may be involved in these e ffects. The use of marker congeners and/or bioassays based on Ah recep tor mediated mechanisms are rapid, low cost pre-screening alternatives for expensive and time consuming gas chromatographic-mass spectrometr ic analysis.