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PRODUCTION ANIMALS
PRODUCTION ANIMALS
An investigation into exposure of pigs to lead from contaminated zinc oxide in 2007–2008 DJ MacLachlan,a* F Dixon,b E Klim,a J Lutze,c M Matisons,d D Moirb and G Smithe
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 noncompliant kidney and liver to enter the human food chain, there was no significant increase in the risk to consumers. Keywords
kidneys; lead; liver; pigs; zinc oxide
Abbreviations AQIS, Australian Quarantine and Inspection Service; DAFF, Australian Government Department of Agriculture, Fisheries and Forestry; DAFWA, Department of Agriculture and Food Western Australia; DHWA, Department of Health Western Australia; FSANZ, Food Standards Australia New Zealand; JECFA, Joint FAO/WHO Expert Committee on Food Additives; ML, maximum level; NRS, National Residue Survey; PTWI, provisional tolerable weekly intake; TF, transfer factor; WA, Western Australia Aust Vet J 2015;93:72–78
doi: 10.1111/avj.12281
I
ntensive livestock industries are more susceptible to feed contamination issues because of their reliance on formulated feeds. The National Residue Survey (NRS) conducts a random monitoring program to detect residues of veterinary drugs, pesticides and contaminants in Australian produce. The survey verifies that production has been in accordance with Good Agricultural Practice and
*Corresponding author. a Australian Government Department of Agriculture, 18 Marcus Clarke Street, Canberra City, Australian Capital Territory 2601, Australia; [email protected] b Department of Agriculture and Food Western Australia, Bunbury, WA, Australia c Australian Pesticides and Veterinary Medicines Authority, Symonston, ACT, Australia d Department of Health, Perth, WA, Australia e Animal Health Laboratories, Department of Agriculture and Food Western Australia, South Perth, WA, Australia
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Australian Veterinary Journal Volume 93, No 3, March 2015
identifies any residue issues that may periodically occur so that they can be rapidly addressed. In the period January to February 2008, lead in excess of the maximum level (ML) of 0.5 mg/kg permitted by the Australia New Zealand Food Standards Code1 was detected in several NRS samples of pig liver from Western Australia (WA). Levels of lead sampled through the NRS rarely exceed 0.01 mg/kg in pig livers. The WA pig industry is relatively small and contained. Production systems include straw-based housing systems, fully or partially slatted intensive systems through to some free-range production operations. Approximately 60% of pigs in WA are produced from multi-site production systems in which independent producers concentrate on only one part of the production chain such as breeding, rearing weaners or finishing pigs.2,3 Weaning in Australia typically occurs when the piglets are 23 days old.3,4 In 2007–08 there were three major suppliers of feed ingredients and premixes and approximately 100 farms that supplied the main pig abattoir in the state.4 This report describes the detection, investigation and management of an incident and to identify ways to improve feed safety systems. Because most Australian pig offal is exported, the incident was potentially harmful to Australia’s reputation as an agricultural exporter. Methods and results Investigations of pig farms and feed suppliers were conducted by staff of the Department of Agriculture and Food, Western Australia (DAFWA) and included interviews with the business managers, review of documents and the collection of samples of blood and tissues from pigs potentially exposed to sources of lead, as well as paint and feed samples that might have contained lead. The number of samples collected was at the discretion of the investigating officer. Samples collected by DAFWA were analysed for lead by ChemCentre, the state government analytical laboratory. The environmental, feed, blood and tissue (liver, muscle) samples were digested in precleaned quartz vessels by microwave-assisted acid digestion.5 Analysis was by inductively coupled plasma-mass spectrometry using internal and external standards. Lead isotope ratios were measured by the CSIRO Division of Exploration and Mining (North Ryde, NSW, Aust) in three liver and two zinc oxide samples using thermal ionisation mass spectrometry. Tissue (liver, stomach (maws), heart, intestine) samples collected for the NRS were analysed for lead by ALS Environmental (Canberra, ACT,Aust). Samples were mineralised by acid digestion (nitric acid) in © 2015 Commonwealth of Australia Australian Veterinary Journal © 2015 Australian Veterinary Association
PRODUCTION ANIMALS
DAFWA developed a simple risk assessment for pig farms to determine the risk of a farm producing pigs with lead levels above the Australian standard. The assessment considered whether the farm was a customer of the supplier of the contaminated ingredient, whether the farm used the contaminated ingredient, lead levels in livers of pigs from the farm (
PRODUCTION ANIMALS
PRODUCTION ANIMALS
An investigation into exposure of pigs to lead from contaminated zinc oxide in 2007–2008 DJ MacLachlan,a* F Dixon,b E Klim,a J Lutze,c M Matisons,d D Moirb and G Smithe
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 noncompliant kidney and liver to enter the human food chain, there was no significant increase in the risk to consumers. Keywords
kidneys; lead; liver; pigs; zinc oxide
Abbreviations AQIS, Australian Quarantine and Inspection Service; DAFF, Australian Government Department of Agriculture, Fisheries and Forestry; DAFWA, Department of Agriculture and Food Western Australia; DHWA, Department of Health Western Australia; FSANZ, Food Standards Australia New Zealand; JECFA, Joint FAO/WHO Expert Committee on Food Additives; ML, maximum level; NRS, National Residue Survey; PTWI, provisional tolerable weekly intake; TF, transfer factor; WA, Western Australia Aust Vet J 2015;93:72–78
doi: 10.1111/avj.12281
I
ntensive livestock industries are more susceptible to feed contamination issues because of their reliance on formulated feeds. The National Residue Survey (NRS) conducts a random monitoring program to detect residues of veterinary drugs, pesticides and contaminants in Australian produce. The survey verifies that production has been in accordance with Good Agricultural Practice and
*Corresponding author. a Australian Government Department of Agriculture, 18 Marcus Clarke Street, Canberra City, Australian Capital Territory 2601, Australia; [email protected] b Department of Agriculture and Food Western Australia, Bunbury, WA, Australia c Australian Pesticides and Veterinary Medicines Authority, Symonston, ACT, Australia d Department of Health, Perth, WA, Australia e Animal Health Laboratories, Department of Agriculture and Food Western Australia, South Perth, WA, Australia
72
Australian Veterinary Journal Volume 93, No 3, March 2015
identifies any residue issues that may periodically occur so that they can be rapidly addressed. In the period January to February 2008, lead in excess of the maximum level (ML) of 0.5 mg/kg permitted by the Australia New Zealand Food Standards Code1 was detected in several NRS samples of pig liver from Western Australia (WA). Levels of lead sampled through the NRS rarely exceed 0.01 mg/kg in pig livers. The WA pig industry is relatively small and contained. Production systems include straw-based housing systems, fully or partially slatted intensive systems through to some free-range production operations. Approximately 60% of pigs in WA are produced from multi-site production systems in which independent producers concentrate on only one part of the production chain such as breeding, rearing weaners or finishing pigs.2,3 Weaning in Australia typically occurs when the piglets are 23 days old.3,4 In 2007–08 there were three major suppliers of feed ingredients and premixes and approximately 100 farms that supplied the main pig abattoir in the state.4 This report describes the detection, investigation and management of an incident and to identify ways to improve feed safety systems. Because most Australian pig offal is exported, the incident was potentially harmful to Australia’s reputation as an agricultural exporter. Methods and results Investigations of pig farms and feed suppliers were conducted by staff of the Department of Agriculture and Food, Western Australia (DAFWA) and included interviews with the business managers, review of documents and the collection of samples of blood and tissues from pigs potentially exposed to sources of lead, as well as paint and feed samples that might have contained lead. The number of samples collected was at the discretion of the investigating officer. Samples collected by DAFWA were analysed for lead by ChemCentre, the state government analytical laboratory. The environmental, feed, blood and tissue (liver, muscle) samples were digested in precleaned quartz vessels by microwave-assisted acid digestion.5 Analysis was by inductively coupled plasma-mass spectrometry using internal and external standards. Lead isotope ratios were measured by the CSIRO Division of Exploration and Mining (North Ryde, NSW, Aust) in three liver and two zinc oxide samples using thermal ionisation mass spectrometry. Tissue (liver, stomach (maws), heart, intestine) samples collected for the NRS were analysed for lead by ALS Environmental (Canberra, ACT,Aust). Samples were mineralised by acid digestion (nitric acid) in © 2015 Commonwealth of Australia Australian Veterinary Journal © 2015 Australian Veterinary Association
PRODUCTION ANIMALS
DAFWA developed a simple risk assessment for pig farms to determine the risk of a farm producing pigs with lead levels above the Australian standard. The assessment considered whether the farm was a customer of the supplier of the contaminated ingredient, whether the farm used the contaminated ingredient, lead levels in livers of pigs from the farm (
