Effects of purified polychlorinated biphenyl analogs on chicken reproduction.

Polychlorinated biphenyl (PCB) compounds were administered in the diet to White Leghorm pullets for 10 weeks. Average embryonic mortality in eggs from pullets fed Aroclor 1242, Aroclor 1254 and 2,4,5,3',4',-pentachloro-biphenyl was 54.7, 59.2 and 74.0 percent, respectively, which was significantly high (p less than .001) compared to controls; however, these three feeds were shown qualitatively to have dibenzodioxin contamination. Degree of chlorination of PCB analogs may not infer that they are toxic, but rather, the position of substitution may be the factor that determines the toxicity to developing embryos.