RECIPE FOR DISASTERA Review of Persistent Organic Pollutants in Food
EXECUTIVE SUMMARY Persistent organic pollutants (POPs) are a group of chemicals which are very resistant to natural breakdown processes and are therefore extremely stable and long-lived. POPs are not only persistent in the environment but many are also highly toxic and build up (bioaccumulate) in the tissues of animals and humans. Most do not occur in nature but are synthetic chemicals released as a result of anthropogenic activities. Vast amounts of POPs have been released into the environment and due to long-distance transport on air currents, POPs have become widespread pollutants and now represent a global contamination problem. Certain POPs have been responsible for some catastrophic effects in wildlife, ranging from interference with sexual characteristics to dramatic population losses. POPs are suspected of causing a broad range of adverse health impacts in humans and there is evidence that current levels of POPs in women in the general population of some countries is sufficient to cause subtle undesirable effects in their babies due to transfer of these contaminants across the placenta and via breast milk. There are numerous POPs which pollute the environment. Some of those which have given rise for particular concern are persistent organochlorines. A meeting of the UNEP's governing Council in 1995 identified a list of 12 POPs as substances of clear concern in accordance with the precautionary principle. These chemicals are all organochlorines. They include dioxins and furans (PCDD/Fs), which are produced as unwanted by-products of several industrial processes including incineration and PCBs and HCB, which have several uses and are also formed as unwanted by-products. DDT, chlordane, heptachlor, aldrin, dieldrin, endrin, toxaphene and mirex, which are pesticides complete the list. The major route of exposure to POPs in humans is through consumption of food. Most of the 12 POPs listed by UNEP are widespread pollutants and are found in foodstuffs from all over the world. Since POPs are soluble in fats (lipophilic) the highest levels are usually found in fatty foods such as meat, fish and dairy products, but POPs can also be found in vegetables, fruit and cereals. In addition to the general contamination of foods by POPs, there have also been accidents in which foodstuffs have become highly contaminated. Greenpeace has issued this report to highlight the contamination of the human food chain by POPs. The report sources material from the published scientific literature. It identifies many instances where regulatory limits for foods are exceeded throughout the world and discusses accidents and industrial activities that have led to high level food contamination.
Environmental pollution has led to the contamination of human food with POPs. Discharges and deposition of POPs to the aquatic environment ultimately results in fish becoming contaminated with POPs. Similarly, atmospheric deposition of POPs on soil and plants leads to their contamination and subsequent consumption by, for instance, cows, results in contamination of milk and meat. In addition, the direct application of organochlorine pesticides leads to residues on crops. Contamination of the human food chain has also occurred when contaminated wastes have been mixed with livestock feedstuffs or directly with food intended for human consumption.
In an attempt to protect public health, regulatory agencies have set permissible levels in specific foods, Maximum Residue Limits (MRLs), which should not be exceeded. For levels of organochlorines in diet, the Food and Agricultural Organisation (FAO) and World Health Organisation (WHO) have set levels which are deemed to be "safe", called Tolerable Daily Intakes (TDIs) or Acceptable Daily Intakes (ADI). These regulatory limits are set using toxicity data from studies in laboratory animals and sometimes also data from human studies. However, the process of risk assessment which is used in deriving the ADIs/TDIs, is a process that is fraught with uncertainties. Furthermore, endpoints of toxicity testing in animals may be inappropriate for detecting certain health effects, potentially leaving health effects undetected. The process of risk assessment assumes that there is a threshold dose of a chemical below which there are no health impacts and therefore "acceptable" levels of exposure are set. However, for some POPs there may be no threshold doses and usually people are exposed to mixtures of chemicals. Therefore it is unlikely that ADIs and TDIs set for organochlorines in diet are truly protective of human health. A review of the scientific literature revealed that in general, levels of PCBs and dioxins in food of industrialised countries are higher than in less industrialised countries due to greater past production, use and discharge of these chemicals together with present emissions. There are also far more data available documenting levels and dietary intakes of persistent organochlorines from industrialised countries. However, available data for less industrialised countries show that there are numerous instances in which levels of pesticides in food exceed permissible limits, such as levels of DDT in several foodstuffs in India and Mexico.
Some populations are exposed to particularly high levels of POPs in their diet. Indigenous Peoples of the Arctic who consume a traditional diet containing sea mammals have a high intake of some organochlorines. This is because sea mammals accumulate high levels of organochlorines and the long-distance transport of POPs towards polar regions has caused contamination of the Arctic. Populations who have a high fish consumption from contaminated waters, such as the Great Lakes or parts of the Baltic Sea, have a high intake of some organochlorines. Children can have a higher intake of organochlorines than adults because of their comparatively high food intake. Moreover, the nursing infant has a particularly high intake of organochlorines because POPs are present as contaminants in breast milk. Exposure of the developing young is of great concern because the developing stages of life are most vulnerable to the toxic effects of POPs.
A number of government and other scientific studies have estimated the daily intake of organochlorine contaminants resulting from diet in various countries. For intake studies of dioxins and furans and dioxin-like PCBs, data is limited to a few industrialised countries only. For organochlorine pesticides, studies are also limited in number.
WHO have set a TDI for dioxins and furans and dioxin-like PCBs of 1-4 pg TEQ kg-1 day-1. WHO experts acknowledge that subtle effects on health from the current intake of dioxins and furans and dioxin-like PCBs might already be occurring in the general population of industrialised countries and efforts should be made to ensure that intakes are in the lower end of the TDI range. Studies show that dietary intake in some countries is within the TDI set by WHO. However, it is of great concern that the TDI is exceeded in Spain and is exceeded by children classed as "high level consumers" in the UK. Furthermore, intake of foods containing particularly high levels of dioxins and furans and PCBs, such as seafood, could have a large impact on the TDI in all countries. It is most alarming that consumption of some fish oils as dietary supplements alone could also cause exceedance of the WHO TDI. Children have different dietary habits and a lower body weight than adults which may cause them to have higher intakes of dioxins and furans and dioxin-like PCBs than adults. This is of concern regarding health impacts because it is a crucial time when their physical and mental capabilities are developing. Moreover, due to high levels of dioxins and furans and dioxin-like PCBs in human milk - which stems from lifetime exposure, mainly through food, - breast-fed infants have an intake which is 1-2 orders of magnitude higher than that of adults. Estimates from the Netherlands and the US clearly show that the TDI is greatly exceeded by nursing infants. Given that the infant is especially vulnerable to toxic insult from chemicals because it is a time when the body is developing, it is particularly worrying that infants have such a high intake. The application of a TDI or ADI to the breast fed infant is questionable because TDIs are designed to prevent adverse health effects over a whole lifetime exposure in a 70 kg adult. Nevertheless, given the vulnerability of the infant, it has been proposed that TDIs should be lower for infants, and therefore, current TDIs should not be exceeded by breast-fed infants. Presently, this is clearly not the case. For total PCBs, a TDI recommended by International Agencies was exceeded by the Italian diet. People of the Faroe Islands who have an average consumption of pilot whale blubber would also exceed the TDI for PCBs. This is because marine mammals accumulate high levels of organochlorine contaminants. Indigenous Peoples of the Arctic, such as Inuit from Broughton Island, Canada, who consume a traditional diet that includes sea mammals exceed the TDI for PCBs. It is of concern that intakes of DDT are very high in India, China and Vietnam in comparison with industrialised countries in the Northern Hemisphere even though the FAO/WHO ADI was not exceeded. Moreover, the ADI was exceeded for intake of aldrin and dieldrin in India, mainly due to high levels present in dairy products. An estimated average consumption of pilot whale blubber by Faroe Islanders also caused in an intake of dieldrin which is in exceedance of the ADI. The consumption of a traditional seafood diet by Arctic Inuit was found to result in an intake of toxaphene that exceeded the ADI.
Organochlorines have been detected in foodstuffs worldwide. Many studies have been conducted to assess the concentration of persistent organochlorines in various food types, but data can nevertheless be considered to be limited. Most studies have been conducted in industrialised nations and data is generally more limited for less industrialised countries and is particularly sparse for Africa. Permitted levels of organochlorines in the foods (maximum residue limits, MRLs) have been set by some national authorities and by FAO/WHO for various food types, but there are no FAO/WHO MRLs for fish.
Fish For marine fish, consumption of fatty fish from the Baltic around the south coast of Sweden resulted in significantly higher levels of dioxins and furans in the blood of consumers. Input of dioxins and furans to the marine environment from industry caused particularly high level contamination of crabs in a Norwegian fjord, in Newark Bay and New York Bight in the US, and in fish from Tokyo Bay, Japan. For freshwater fish, studies on various rivers showed that in Spain, heptachlor epoxide exceeded the WHO/FAO MRL and in Australia, PCBs and chlordane exceeded WHO/FAO MRLs. Fish taken from the St. Lawrence River and rivers in British Colombia, Canada, had higher concentrations of dioxins and furans and dioxin-like PCBs than proposed limits due to discharges from industry. In south Taiwan, the WHO TDI for dioxins was exceeded for fish taken from a river and culture ponds as a result of industrial activities in the area. High levels of DDT were found in meat from Thailand and the FAO/WHO MRL was exceeded for meat in Vietnam and in Mexico. For dioxins and furans, veal is the most highly contaminated meat due to a high proportion of milk in the calf diet. Second to this is beef. In India, a high proportion of milk samples tested were highly contaminated with DDT and HCH and some exceeded national limits. High levels of DDT were apparent in milk in Hong Kong and Argentina. Residues of aldrin and dieldrin were also reported to be high in milk from these countries and levels of heptachlor and heptachlor epoxide exceeded FAO/WHO MRLs in Hong Kong, Argentina and Mexico.
The contribution of vegetables and cereals to intakes of dioxins and furans in the diet of some countries, such as the USA, has been reported to be very small with greater than 90% of the intake coming from meat, fish and dairy products. However, a study on the Mediterranean diet in Spain reported that cereals, pulses, fruits and vegetables can have a significant contribution (45%) to PCDD/F intake. For total PCBs, intake in many countries is predominantly from meat and fish but in less industrialised, tropical countries such as Vietnam, cereals and vegetables can be the main source. DDT residues have been found in tea and coffee. A 1994 study reported that levels in vegetables from Australia suggested recent application on crops despite the existing ban on use. Wheat stored in gunny sacks in India was found to be contaminated with DDT and HCH at levels greater than the FAO/WHO MRL. This was due to spraying of residential areas for vector control. A general decline in the levels of some organochlorines in foods and in human milk has been reported in recent years. For instance, organochlorines in fish from the Great Lakes are still high although levels have generally declined in recent years. DDT levels in meat have been reported to have fallen in Australia and Canada. There have been some regional declines in PCBs in marine fish but a global decline is not expected in the next few years. DDT levels have generally decreased in marine fish but levels in areas of the tropics indicate continued input to the marine environment. In human milk, concentrations of dioxins and furans have not increased in Western countries in recent years and levels in some European countries have declined. A decreasing trend has been observed for DDT and HCB in Europe where DDT is banned, but not in Mexico where it is still used. Levels of PCBs and chlordane in human milk do not appear to have declined in countries where levels have been monitored. These examples show that although some compounds have declined, others remain stable due to persistence and/or continued input into the environment.
There have been a number of food contamination incidents involving dioxins and furans and PCBs. Some have occurred from local sources of pollution, such as incinerators, and others have occurred after waste or toxic products have been mixed with food for human or animal consumption. Incinerators of all types emit dioxins, furans and PCBs. There have been several instances in Europe during the 1990s in which emissions from municipal waste or hazardous waste incinerators have resulted in depositions on nearby grazing land for cows leading to contamination of milk. Incidences in the Netherlands, Austria and UK have been recorded in which levels of dioxins and furans in milk exceeded regulatory limits and resulted in bans on the sale of milk. Reclamation of copper from cables causes the release of dioxins, furans and PCBs from burning of the PVC plastic coatings on the cables. In south Taiwan, fish from aquaculture ponds were found to be highly contaminated due to the burning of electrical cables and credit cards nearby. Fish from the area is an important local source of food and it was found to greatly exceed the WHO TDI for dioxins and furans and dioxin-like PCBs. Two accidental PVC fires in Germany in 1992 and 1996 also caused localised contamination with dioxins and furans. Subsequently, a number of bans on the sale of vegetables and animal products had to be implemented.
Various incidents have occurred in which cooking oil for human consumption has been contaminated by PCB oil. The "Yusho" incident occurred in Japan in 1968 and the "Yu-Cheng" incident occurred in Taiwan in 1979, both affecting around 2000 people. Increased mortality rates were recorded following the incidents and a broad spectrum of health effects were reported. Children exposed in utero were severely affected. More recently there have been two incidents in which animal feeds have become contaminated. In Belgium, in early 1999, PCBs oils got into animal feedstuffs. This resulted in chickens becoming highly contaminated, for example, at levels that were 10 to 5000 times levels in milk standards. Not all of the chickens were for human consumption as some were for breeding. Eggs also became contaminated and restrictions on the sale of chickens and other meats were implemented due to possible contamination. The incident had a major economic impact on the Belgian food industry with world-wide exports of food being affected. It is of concern that there was a 4 month delay between the first illness symptoms occurring in the chickens and restrictions being placed on foods resulting in unnecessary human exposure. Use of contaminated citrus pulp pellets from Brazil in animal feed caused contamination of milk with dioxins in Germany towards the end of 1997 and beginning of 1998. Some milk had levels greater than nationally permitted. The citrus pulp was also used as animal feed in a total of 12 EU countries. They may have caused elevated levels in milk in countries other than Germany, although data are not available. A total of 92,000 tons of citrus pulp pellets had to be disposed of. The source of the contamination in the feed was found to arise from dioxin contaminated waste lime produced as a by-product by Solvay in Brazil. The waste lime is converted into a form which is then added to citrus pulp for animal feed. Subsequent EC legislation has set a maximum limit for dioxins in citrus pulp pellets to protect European food sources from any possible further contamination. However, there are no limits for dioxins in other types of animal foodstuffs.
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