Levels of PCBs in wild bird eggs: considering toxicity through enzyme induction potential and molecular structure

Polychlorinated biphenyls (PCBs) were analysed in wild bird eggs from industrialised areas in South Africa. The concentration, congener profile, feeding guild, potential associated risk and biology were investigated. PCBs were detected in all eggs with 30 congeners present in more than 80% of the samples. Σ(34)PCB concentrations ranged between 0.9 and 296 ng g(-1) wet weight (ww). The metabolic potential of the PCB metabolic groups showed good agreement with the biodegradability of the individual congeners. Phenobarbital-type (PB-type) inducer PCBs were prevalent, indicating the predominance of less toxic PCB congeners. However, non-ortho PCBs which were not included in the current analyses, could affect the toxic potential of the PCBs in the eggs requiring more investigation. Although the current levels of PCBs measured do not indicate a health risk to the birds assessed, the presence of mono-ortho PCBs at appreciable levels motivates for the assessment of dioxin-like chemicals in wild bird eggs.