Reason for pig meat crisis has to be identified
ANALYSIS: The pig meat debacle is a huge blow to consumer confidence, irrespective of how dangerous the toxins involved are to health
THE FOOD Safety Authority and the Department of Agriculture and Food during routine surveillance identified a pig with residue of polychlorinated biphenyls (PCBs) in excess of the permissible levels. The sample was taken on November 19th and the result was reported on November 28th. This triggered an investigation on the farm at which the pig had originated. Initially, it was thought something untoward must have occurred on this farm.
Once the result was known, no pigs from the farm were allowed into the food chain and further pigs were sampled, as were all the components of the ration being fed to the animals. One ingredient in the pigs' diet tested positive, which led the investigation to the source of this ingredient, a mill in Carlow, where bread and confectionery was being recycled into animal feed. More samples were taken from the mill, and all the farms supplied from it were immediately identified and locked up, and samples were taken from them.
Eight other pig farms were identified. These were shut and pigs from the farms were tested. The testing requires the pigs to be slaughtered, and samples of kidney fat taken for analysis. Testing for these chemicals takes time and initial results only give the family of chemicals. Further analysis is required to identify the specific chemical and quantities present. Samples from Ireland had to be forwarded to a laboratory in England for definitive identification. The preliminary results were shared with competent authorities in other EU member states.
Irish pig meat and pig fat is exported to the EU and farther afield. One food processor in Belgium, which provides pig fat to the manufacturing industry, noticed an increase in PCBs in composite samples containing pig fat from several member states since September, and was trying to identify from which country the contaminated fat was coming.
On Saturday the results of dioxin tests from the English laboratory became available, and the Irish authorities took the decision to order a total recall of all Irish pig meat processed since September 1st.
A small number of additional pig farms which bought breeding stock, or weaners, from the nine implicated farms are currently being identified, and they will also be locked up and their stock sampled.
Once pig meat enters the processing sector and is turned into sausages and processed meats, traceability to the processor and perhaps the day of production may be possible, but not back to the individual farm. Because the regulatory authorities in Ireland had no way of knowing which meat came from the nine farms, they initiated a recall on all pig meat. There are 400 pig producers in Ireland and although only nine pig farms fed the contaminated ration, meat from the other 391 is also caught up in the recall.
The term dioxin refers to a group of chemical compounds that share certain similar structures and mode of action on the body. Over 30 of these compounds exist and are members of three closely related chemical families; the chlorinated dibenzo-p-dioxins (CDDs), chlorinated dibenzofurans (CDFs) and certain PCBs.
In the past PCPs were widely used in the manufacture of coolants and lubricants, but their manufacture was banned in 1979. However, they are still generated unintentionally as byproduct of certain processes. Simply burning rubbish can generate them, and they are also produced when pulp and paper are bleached with chlorine. Certain chemical manufacturing and other industrial processes can all generate small quantities of dioxins.
These dioxins differ in their ability to cause harm to living organisms. To compare the toxic potential of different dioxins, the scientists who study these compounds have developed Toxic Equivalent Factors so that when a mixture of compounds are implicated, the total toxicity can be calculated in terms of its Toxic Equivalent Quantity (TEQ).
Data demonstrating the adverse health effects of dioxins comes principally from four sources: 1) Industrial accidents where there has been a massive release of dioxins; 2) occupational exposures of workers in industries where these compounds have been generated; 3) a study of US Vietnam veterans who were exposed to Agent Orange, a chemical used to clear foliage in the Vietnam War; and 4) experiments where laboratory animals have been exposed to large doses.
Follow-up studies have been undertaken for 30 years on people exposed to an industrial accident in West Virginia, while the US veterans exposed to Agent Orange and residents of Seveso in Italy, who were exposed in a 1976 industrial accident, have been followed up for 15 years. Acute symptoms are seen in animals, but only a small number of humans have developed long-term adverse effects associated with major exposure.
One of the big questions being asked by everyone in Ireland who has eaten Irish pork, along with those abroad who have done so, is "What, if any, adverse health effects can we expect?" The answer the public health professionals can give is that they don't know. Only a subset of Irish pork was contaminated, and estimates are being undertaken to calculate how much an average individual might have eaten. On the basis of a very similar incident in Belgium in 1999, where livestock were fed a contaminated ration and no adverse effects were seen, Ireland can expect no illnesses.
The European Food Safety Authority - a consumer protection agency created in the aftermath of the BSE crisis and the Belgian dioxin crisis to pool scientific resources within the EU - is convening its panel of experts on dioxins to undertake a risk assessment for all the member states, including Ireland.
These chemicals are not permitted in the food chain, and irrespective of the level of risk they pose to public health, this crisis is a huge blow to consumer confidence in the safety of the food supply.
The question of how this was allowed to happen will have to be answered.
• Dr Patrick Wall is associate professor of public health at University College Dublin and a former chairman of the European Food Safety Authority