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stockholm convention on persistent organic pollutants comes of age in may 2004 – food safety implications
Persistent Organic Pollutants (POPs), have been in the news recently, following the coming into force on 17 May of the Stockholm Convention on Persistent Organic Pollutants, under the auspices of the United Nations Environment Programme (UNEP). The term “POPs” is used to describe a group of toxic chemicals which are found in the environment. Twelve POPs are named in the Convention as follows: dibenzo‑p‑dioxins (dioxins), dibenzo‑p‑furans (furans), polychlorinated biphenyls (PCBs) and nine individual organochlorine pesticides, namely aldrin, dieldrin, DDT, endrin, chlordane, hexachlorobenzene, mirex, toxaphene and heptachlor. These latter chemicals have been used in the past as insecticides but have now been largely phased out because of their toxicity and persistence, as have the industrially-used PCBs. They are banned in the European Union (EU), including Ireland, but can still be found in the environment due to past use. The dioxins and furans are by-product chemicals, released primarily as a result of the activities of manufacturing industry and burning of household and municipal waste. Under the Convention, national Governments have agreed to ban the use of POPs where such use is currently allowed (not in the EU) and to clean up unwanted and obsolete stockpiles of pesticides and toxic chemicals that contain POPs. The Convention also requires Governments to monitor POPs in the environment, to reduce and eliminate releases of dioxins and furans and to evaluate additional chemicals and pesticides to be added to the initial list of POPs, in addition to other actions. As part of the national food surveillance programme, the Food Safety Authority of Ireland, together with official agencies are monitoring the Irish food chain for contamination by these compounds.
The common characteristic of all these POPs is that they are persistent and fat-soluble, and when released into the environment they enter the food chain and accumulate in fatty tissues. They are also relatively volatile, a property which, coupled with their resistance to breakdown, has resulted in their long range movement through the atmosphere. This means that they may be generated and released in one region of the world, e.g. by developed and industrialised countries, but end up in the environment in another region, such as the Artic or Antarctic. They are therefore distributed ubiquitously and they have been widely detected in biota including in human tissues – “the burden of the past”. The problem was initially identified as a result of observations of decreasing fertility, population declines and malformations in a number of wildlife species including birds, seals and beluga whales. It is now recognised that POPs may cause endocrine disruption, reproductive and immune dysfunction, neurobehavioural disorders and cancer in exposed populations including humans.
How does food safety interface with the POPs Convention? The chemicals currently controlled under the Convention have the potential to accumulate in the food chain, as initially realised with the extremely fat-soluble and persistent pesticide DDT. Although DDT has been largely phased out except for certain identified uses (it is still used to control malaria due to its effectiveness against the mosquito vector for the malaria parasite), traces of it can still be found in the fatty tissues of meat, fish etc. consumed by the general population. The same is true for the other POPs on the list of 12, e.g. dioxins, furans and PCBs, and is also true for more recently used chemicals not yet included in the POPs Convention list, for example the brominated flame retardants (BFRs). Exposure of the general public is thus largely via food, and the traces of these chemicals that can be found in our bodies[1] have come mainly from food rather than water or air pollution.
In order to reduce human exposure to these substances, the European Commission has established Maximum Limits for the dioxins, furans and some of the PCBs in food, and Maximum Residue Limits (MRLs) for all the pesticides listed, except mirex. Member States are required to carry out surveillance of food for the presence of these contaminants, and the Pesticide Control Service of the Department of Agriculture and Food, on behalf of the FSAI, currently analyses for the majority of the pesticide POPs in fruit, vegetables and cereals, and also in fresh meat, milk, dairy products, eggs and honey of Irish origin. The latter analyses also include certain PCBs. The analytical results for 2002 (the last year for which results are available) showed that traces of dieldrin were detectable in a root crop, while dieldrin, a DDT metabolite and hexachlorobenzene were detected in bovine and ovine samples. Overall some 5.4% of the bovine samples analysed contained very low but detectable pesticide or PCB residues. Some 4.6% of samples analysed contained detectable residues of DDT (as metabolite ppDDE) and 0.8% of samples contained a detectable residue of dieldrin. The residue levels detected are shown in Table 1. The levels detected were in trace amounts and were not considered significant from a consumer safety viewpoint.
The results show that traces of POPs can be found in Irish animal products, as is the case virtually all over the world. The Marine Institute has monitored a number of these POPs, including PCBs and toxaphene, in Irish fish and also has found detectable levels, while FSAI has found measurable levels of dioxins, furans and PCBs in a range of food of animal origin (including fish, eggs, milk, meat). The results of these studies have been reported on the FSAI website, www.fsai.ie. In all cases levels were below the MLs or MRLs established at European level, and in comparison with results from other EU Member States shows that the levels of these POP contaminants in Irish food are generally amongst the lowest in Europe. In parallel, an investigation in 2001/2002 into levels of dioxins, furans and PCBs in Irish breast milk undertaken by the FSAI showed that the body burden of these contaminants as measured in breast-feeding Irish mothers was relatively low compared with many other countries participating in this study (Figure 1). This study was part of the World Health Organization’s ongoing study on dioxin levels in human breast milk, and reflects the lower exposure of Irish women to dioxins and furans in food.
In conclusion, as part of the national food surveillance programme, the FSAI, together with official agencies, is monitoring the Irish food chain for contamination with POPs. The FSAI’s monitoring programme will contribute to Ireland’s compliance with the objectives of the Convention. It is anticipated that the Stockholm Convention will save lives and protect the natural environment – particularly in the poorest communities and countries – by banning the production and use of some of the most toxic chemicals known today.
* The Environment Commissioner, Margot Wallström provided us with an example of this recently, when she agreed to have a blood sample taken for chemical screening; this blood sample was subsequently found to contain 28 out of 77 chemicals looked for, including PCB and DDT which have been banned in Europe for several decades.
Figure 1: Levels of Dioxins and Furans in Human Milk, 2001/2002
[PRINTER FRIENDLY VERSION]
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