Effects of Polychlorinated Biphenyls (PCBs) and Dioxins on Growth and Development

Abstract

<jats:p> Polychlorinated biphenyls (PCBs) and dioxins are potentially toxic compounds which occur widely in the environment. Their effects on the growth and development of infants at the levels currently found in highly industrialised western countries is not well known. This Dutch multicenter study, combining animal and human studies, tries to answer this question. </jats:p><jats:p> Animal studies showed that PCB 169, given once during pregnancy at a dose of 1.8 g kg<jats:sup>-1</jats:sup> bodyweight, has an effect on developmental parameters, dopamine regulation and fertility. Effects on thyroid hormones were also found in animals, probably due to both a competitive binding of PCB metabolites to the thyroxine binding protein and increased glucuronidation, Perhaps to compensate for this, an increased diodase activity in the brain was found. Human studies involved 400 mother-infant pairs, half of them being breast-fed, the other half were fed a formula devoid of PCBs and dioxins. PCB levels were measured in serum and dioxin and PCB levels in breastmilk. Levels were found to be as high as previously found in highly industrialised countries. Growth and development were carefully documented, but no data are as yet available. In pregnant women, a significant negative correlation was found between some dioxin and PCB congeners in milk and plasma thyroid hormones, while newborn infants showed higher thyroid stimulating hormone (TSH) at higher levels of dioxin exposure. </jats:p><jats:p> In summary, data from this combined multicenter study involving animals and humans increases our insight into the potentially negative effects of PCBs and dioxins on growth and development. </jats:p>

Maternal seafood diet, methylmercury exposure, and neonatal neurologic function

“…Simlarly, ΣPCB in cord tissue from the same cohort (4) showed an arithmetic average of 1.6 ng/g lipid, as calculated from concentrations of congene 138, 153 and 180. However, the Dutch study showed a median of 2 μg/l for the sum of PCB congeners 118, 138, 153, and 180 in maternal plasma (9,28). In the present study, the median for the same congeners in maternal seru 11…”

“…Prenatal exposures below this level were associated with neurobehavio delays detectable at age seven years (4), but equivocal findings on developmental tests have been reported from other studies of younger children (5,6). Other seafood contaminants include polychlorinated biphenyls (PCBs), an prenatal PCB exposures have also been linked to delays in neurobehavioral development (7)(8)(9). However, the nature of these deficits and their detailed relation to specific organochlorine compounds is unclear, although som PCBs may act via interference with thyroid function (10).…”

Maternal contamination with PCBs and reproductive outcomes in an Australian population

“…This method of exposure measurement has been used in several previous studies (Dewailly et al, 1993;Sauer et al, 1994;Schade and Heinzow, 1998).…”

Thyroidal dysfunction and environmental chemicals--potential impact on brain development.

“…Laterally substituted chlorinated aromatic compounds such as the meta and para PCBs, particularly when hydroxylated, are ideally suited to serve as binding ligands for T4-binding proteins (54,56). Because environmental persistence is correlated with lateral substitution, many of the congeners accumulating in the environment are likely to impact the thyroidal system (55 (1,56,(60)(61)(62). Cheek et al (62) have shown that half the hydroxylated PCBs they tested had higher affinities than did T4 for TTR.…”