Polychlorinated biphenyls and hexachlorobenzene in full-term neonates. Reference values updated

To determine actual reference values of polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) in full-term neonates.

Cord blood samples were taken from 200 healthy, full-term neonates in 1998. Blood specimens were immediately centrifuged, and serum was stored in glass tubes at -20 degrees C up to analysis. Six PCB congeners (IUPAC No. 28, 52, 101, 138, 153, and 180) and HCB were determined with capillary gas chromatography with electron capture detection. Study groups were tested on mean differences with Wilcoxon's test of independent samples. The 95th percentiles by rank were calculated as reference values.

One sample was excluded from further evaluation because of unusually high PCB concentrations. Personal data of the remaining 199 newborns showed 106 male and 93 female neonates. Mean gestational age was 40 weeks (range 38-43 weeks), mean birth weight was 3,450 g (2,300-5,060 g). The concentrations of the lower-chlorinated PCB congeners 28, 52, and 101 were below the detection limit with exception of two probes. Reference values (95th percentile by rank) of the higher-chlorinated PCB congeners and HCB were as follows: PCB 138, 0.5 microg/l; PCB 153, 0.5 microg/l; PCB 180, 0.4 microg/l; and HCB, 0.5 microg/l.

The results of the present study clearly demonstrate a further decline in the prenatal uptake of PCBs and HCB since 1994-1995. During the past 15 years, a 75% decline in the prenatal burden with PCBs and a 90% reduction in the burden with HCB could be demonstrated.