An investigation into exposure of pigs to lead from contaminated zinc oxide in 2007-2008.

BACKGROUND: High levels of lead, up to 3.3 mg/kg fresh weight, were detected in pig liver in Western Australia at the beginning of 2008. This followed the detection of lead at above the maximum level (ML) in a pig liver through the National Residue Survey (NRS). The contamination source was traced back to a zinc oxide feed additive used early post-weaning that contained in excess of 8% lead. METHODS AND RESULTS: Confirmation of the source of lead contamination was obtained by comparing lead isotope ratios for the zinc oxide and the pig livers. The investigation demonstrated the importance of verifying the safety of feed and feed ingredients prior to incorporation in feed. Retrospective analysis of NRS data indicated that the level of lead needed to trigger an investigation for intensively housed pigs should be considerably lower than the ML. As a result, investigations in Australia will now be conducted when levels of lead in pig liver exceed 0.1 mg/kg fresh weight. CONCLUSIONS: Despite the potential for small amounts of non-compliant kidney and liver to enter the human food chain, there was no significant increase in the risk to consumers.