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Four groups of 16 age-matched female Crl:SKH1-hrBR hairless mice were exposed to either control soil or polychlorinated biphenyl (PCB)-contaminated soil (retrieved from an electrical waste landfill in Southern Illinois) for 11 weeks. The mice were exposed in a study to determine interactions between environmental PCBs and ultraviolet radiation (UVR), but the UVR group did not differ and provided a replicate for the residue study. Ear biopsies were performed immediately after the termination of soil exposure. The mice were maintained in regular bedding for 37 weeks thereafter. The ear-skin, trunk-skin, fat-pad, and liver samples were collected and weighed at the end of the study (week 48) and analyzed for PCB residues. A total of 141 PCB congeners were target analytes. There were significant differences in body weights and food consumption from week 2 to 28. The liver weights of mice treated with PCB only were significantly greater than those of UVR-treated mice. The fat-pad weight did not differ among treated groups. PCB residues in the ear biopsies specimens of mice exposed to contaminated soil were 342.3 and 317.2 ppm in the PCB- and PCB + UVR-treated groups, respectively, and contained both persistent and episodic congeners. After 37 weeks of isolation from soil, the ear PCB residues decreased to 21.5 ppm (PCB group) and 14.5 ppm (PCB + UVR group), and only persistent congeners contributed to the total PCB residues. The accumulation of PCB residues was highest in the fat pad (fat pad > ear skin > trunk skin > liver) in both PCB +/- UVR groups at the end of the study. However, the percentage of individual congeners contributing to total PCBs in these different tissues did not differ.

One-hundred-and-twenty hairless mice were irradiated with UVB (310 nm, exposure 60 mJ/cm2) on a limited area of the dorsal skin. At different time intervals after irradiation, the rate of endogenous dehydrogenase activity per mg dry epidermis was measured by the tetrazolium reduction method. The amount of formazan deposited remained normal for 18 h, and then increased, reaching a peak significantly higher than normal at 24 h, and thereafter returned to normal. At day 8 there was a new, probably significant peak. The reaction was followed for 14 days. It was concluded that UVB irradiation provokes a period of increased formazan deposition in the epidermis, similar to what has been observed after ionizing radiation and chemical carcinogens. The validity of the tetrazolium test for skin carcinogenic irritaments was thus also confirmed.