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Chemicals: Dioxins and Furans
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Dioxins (the common name for polychlorinated dibenzo-para-dioxins) and furans (polychlorinated dibenzofurans) are two closely related groups of chemical byproducts that are produced throughout the world. Both groups consist of chlorinated compounds that have a range of congeners -- members of the same structural group with different configurations. The congeners differ in terms of the number, position and combination of chlorine atoms on the molecule. There are 75 possible dioxin congeners and 135 possible furan congeners.1 The dioxin and furan congeners thought to be most toxic to humans are the seven dioxins and ten furans with a particular pattern of chlorines known as the 2,3,7,8-congeners. Most studies measuring human exposure to dioxins and furans focus on this group, and the term "dioxin" is often used to refer to this group of 17 congeners.

Dioxins and furans are not produced intentionally. Rather, they are byproducts of a range of chemical, manufacturing and combustion processes including:2

  • production of certain pesticides (i.e. chlorophenol,
    chlorophenoxyacetic acid);
  • paper pulp bleaching;
  • production of certain dyes and pigments;
  • municipal waste incineration;
  • sewage-sludge incineration;
  • hospital-waste incineration;
  • polyvinyl chloride plastic (PVC) production and incineration;
  • diesel-engine exhaust;
  • accidental fires and explosions of chlorine-containing material;
  • metal production; and
  • combustion of wood.

Incineration is believed to be the main route by which dioxins and furans are produced, and is often the area of focus in pollution-prevention efforts.


Health Effects of Dioxins and Furans

Dioxins and furans are among the most hazardous chemicals known, and even extremely tiny doses have been shown to cause negative health effects. These chemicals are listed by several governmental agencies as known causes of cancer in humans. Indeed, studies have linked dioxins and furans to many types of cancer, as well as to reproductive problems, abnormalities in fetal development, immune alterations and disruption of hormones.3 Because dioxins and furans are attracted to fat and are resistant to metabolism, they are notorious for accumulating in the animals humans eat, and by that route accumulating in humans. Within the human body, the highest levels of these chemicals are in fat and breast milk.


Dioxins and Furans in the Body

Some dioxins and furans are extremely persistent in the environment. Once released into the air, dioxins and furans can be transported on air currents to distant places around the globe. For that reason, studies of international pollution patterns have shown that even areas with little or no industry can be contaminated with high dioxin and furan levels.4 For example, people living in remote Inuit villages in the Arctic have significant dioxin levels in their bodies despite their geographic isolation and the lack of dioxin exposure sources in the area.5 Still, higher levels are most commonly associated with industrial areas.

A small share of the dioxins and furans released into the environment are broken down by sunlight, but most persist by attaching to soil particles and sediment in water. Once attached to such particles, they enter the food chain, leading eventually to bioaccumulation in animal fat.6

Human beings can be exposed to dioxins and furans in a number of ways. Eating contaminated food (primarily meat, dairy products and fish) is the major path for dioxin exposure,7 but other, less common, routes of exposure include contact with certain pesticides and herbicides (such as the wood preservative pentachlorophenol and the phenoxy herbicides), living near hazardous waste sites or incinerators that release dioxins and furans or working in industries that produce dioxin and furan byproducts.8

Dietary exposure accounts for more than 90 percent of human dioxin and furan intake.9 Fatty foods usually contain more significant levels because they are higher on the food chain and thus have accumulated more dioxin. Figure 1 demonstrates that the major portion of a person's average dioxin and furan exposure comes from dietary exposure.


Figure 1

Figure 1


Once dioxins and furans have entered animal tissues, they have few avenues of departure, so the chemicals can persist for many years. In lactating women, dioxins and furans may leave the body in breast milk. As with many other persistent chemicals that appear in breast milk, the concentration of dioxins and furans changes with time.10

A number of animal and human studies have looked at the health effects of dioxins and furans on children's health from in utero and postnatal exposure. Health outcomes identified have included low birth weight, hormone fluctuation, neurobehavioral function and altered immune function. Thus far, the studies have not identified any links between these health effects and exposure to dioxins specifically from breast milk. Breast milk contains a mixture of environmental pollutants, many of which may have effects similar to those of dioxin. Moreover, it can be difficult to separate the effects of exposures before birth due to chemicals in the mother's blood, from the effects after birth from breast milk. Thus, it is difficult to link health effects to an individual pollutant in breast milk.

The World Health Organization Working Group on the Assessment of Health Risks for Human Infants from Exposure to PCDDs, PCDFs and PCBs reached two important conclusions11:

  • The incidence of obvious health problems in breast-fed children whose mothers had measurable levels of dioxin in their breast milk was generally within the normal background variation.

  • They found that the benefits of breastfeeding in terms of neurological measures remained, regardless of dioxin exposure via breast milk.

Several other researchers have reinforced this finding showing that breastfeeding will provide health benefits even if dioxin residues are present in the breast milk. Most scientists have concluded that the benefits of breastfeeding are so great as to outweigh the risks associated with dioxin exposure. Such exposure may diminish the benefits of breastfeeding, but not to the point that women should avoid breastfeeding to avoid exposure.12


Controlling Exposure: Bans and Restrictions

Unlike pesticides and other POPs that have specific functions, dioxins and furans are unintentional byproducts of industry, making their production difficult to ban or restrict.

Attempting to ban the formation of dioxins and furans would require fundamental changes in industry practice. Environmentalists and activists have called on local, national and international agencies to reduce dioxin formation. The effort has included local and regional "zero-dioxin" initiatives to force changes in production or the adoption of different methods. Many groups have also called for a halt to all forms of incineration and the phaseout of products whose manufacture and disposal produces dioxin.


Assessing the Extent of Exposure: Limits and Benchmarks

Most chemicals that are either in widespread use or that have caused widespread contamination are subject to national and international benchmark levels, established to protect public health. In the case of dioxins and furans, there is no evidence to show that these benchmarks are protective.

That said, a number of agencies have promulgated a variety of different benchmark values for exposure to dioxins and furans, with little consensus emerging on which should be used as a basis for regulation. The U.S. EPA's Dioxin Risk Assessment in 2000 concluded that there is "no 'safe' level of exposure to dioxin."

Separate benchmarks for dioxin and furan levels in breast milk have not been established. Benchmarks set for "dioxin" are sometimes set for the most toxic congener, 2,3,7,8-TCDD, and sometimes for the combined "toxic equivalencies" (TEQs) of numerous dioxin congeners. In keeping with the science indicating toxicity of dioxin at ever lower levels, many successive Tolerable Daily Intake (TDI) levels have been established, and these have tended to go lower and lower over time. Canada and some European countries have set a TDI level of 10 picograms per kilogram of body weight per day (pg/kg/day). (A picogram is one trillionth of a gram.) The Japanese government has set a TDI of 4 pg/kg/day, and the World Health Organization has recommended a TDI of 2 pg/kg/day. In the United States, the Agency for Toxic Substance and Disease Registry (ATSDR) has established a minimal risk level (MRL) of 1 pg/kg/day. The U.S. EPA's new dioxin reassessment could lead to a TDI significantly lower than any of these.

Many of the countries with measured dioxin in breast milk have average residue levels above these "acceptable levels." For instance, a WHO study found that the estimated average daily intake of dioxin for a breast-fed infant was significantly higher than most established TDIs. The estimated weight-adjusted intake for infants is approximately 10 to 100 times the estimated intake for adults.13


Breast Milk monitoring Studies Measuring Dioxin

Dioxins and furans have been measured in the breast milk of women from at least the following countries:

AlbaniaFaeroe IslandsKazakhstanSouth Africa
AustriaFinlandLithuaniaSpain
BelgiumFranceNetherlandsSweden
CambodiaGermanyNew ZealandThailand
CanadaHungaryNorwayUnited States
CroatiaIndiaPakistanUnited Kingdom
Czech RepublicIsraelPolandUkraine
Denmark JapanRussiaVietnam
EstoniaJordanSlovakia 

Much of this data is from the WHO-coordinated studies conducted in 1986-88 and 1992-93. Most countries have not independently measured dioxin in blood or breast milk.

The majority of the data comes from developed nations or countries that have significant industry. However, the lack of information on dioxin/furan residues in breast milk in African, Latin American and other nations does not mean that dioxin is not a problem there. Rather, current information about dioxin residues in breast milk only tells us about what has been measured thus far. Based on what we know about the widespread nature of dioxin contamination in the food chain and its ability to move great distances, dioxin levels in breast milk are likely a worldwide concern.


Limitations of Studies Measuring Dioxin in Breast Milk

Dioxins and furans rarely occur independently. Rather, they are produced as complex mixtures. Because of this, they are usually measured together. Often, totals of combined furan and dioxin congeners are simply referred to as "dioxins" or "dioxin."

It is often difficult to draw conclusions about national and international trends in dioxin contamination because of the numerous factors affecting levels and limitations in the way the data is reported. Some of these challenges include:

  • Toxic Equivalencies. Unlike many other chemicals, whose toxicity is expressed in terms of a measured concentration, the potential toxicity of dioxins and furans in human tissues is often expressed in terms of "toxic equivalencies" (TEQs). The concept of TEQs was developed to aid in the interpretation and comparison of mixtures of dioxins and furans. A TEQ is calculated by evaluating the relative toxicity of each individual dioxin and furan congener and comparing it to the most toxic dioxin congener -- 2,3,7,8-tetrachlorinated dibenzo-para-dioxin (TCDD). A congener's relative toxicity is multiplied by the detected concentration to get a TEQ value. The final reported value, referred to as the dioxin TEQ, is the sum of all individual TEQs. It is this final sum that is used in the comparison of dioxin and furan values in breast milk.14

    Several different conventions have been devised for conversion to toxic equivalencies, put forward by Nordic, the U.S. EPA and WHO. The most common is WHO's International TEQ, or I-TEQ.15 But some studies use other toxic equivalency calculation schemes. In such cases, it is difficult to compare these with studies using I-TEQs.

  • Congener Detection. Another problem in comparing studies of dioxin/furan levels in breast milk is the different methods of detection. TCDD is considered the most toxic of the dioxins and is almost always measured. However, different researchers may measure different assortments of the remaining 16 dioxins and furans. For WHO-coordinated studies, all 17 must be measured so that data are comparable. Other researchers, however, may not follow the WHO protocol.

    Related to this are regional variations in common dioxin congeners. Because different industrial processes produce different mixtures of dioxins and furans, dioxin pollution patterns are not uniform.16 As a result, it can be difficult to compare regions with exposure to different pollution sources, since their congener patterns will differ.

  • Separating Out Specific Congener Trends. When values are simply given as an I-TEQ value, another set of challenges can occur. Analyzing only the sum I-TEQ values may give a general idea of the total level of contamination, but data trends seen in the summed values may be different if the data is separated into specific trends for different dioxin congeners. Changes in the congener composition of the contamination may not be noticed if only the summed value is available. Such changes can be important because they could be the result of changes in industrial practices and pollution patterns and may therefore have different implications, depending on the toxicity and longevity of the increasing congeners.

  • Pooling Samples. Because of the expense of the analytical techniques and the relatively large quantities of breast milk needed for detecting dioxins and furans in breast milk, most studies look at only pooled samples. That is, a group of women may all donate samples that are then combined into one sample for analysis. This means that individual levels, and the variability (range) of dioxin levels, may not be known. Not knowing the range can be problematic because outliers (extremely high or low values) can indicate unique exposure scenarios.

  • Small Number of Studies. Relatively few studies measuring dioxins in breast milk have been performed over time, so it is not possible in most cases to draw definitive time trends or make conclusions about how levels are changing.


Some Important Examples of Dioxin in Breast Milk

Because of their persistence, dioxins and furans are found throughout the environment, making human intake, and their presence in breast milk, extremely common. Dioxins/furans have been found in breast milk in every country tested, and are likely present in countries that have not yet been tested.

The general time trend in many countries seems to be toward a slight decrease of dioxin levels in breast milk over the past decade. In some countries, the decrease has been quite dramatic, with levels reduced by as much as 50 percent.17 However, despite this downward trend in some countries, trend lines elsewhere may be going up.18

A report on dioxin in breast milk in the European Union showed that between 1988 and 1993, average levels among women in European Union nations decreased. Some regional differences emerged, but the average decrease was approximately 35 percent.19


Dioxins in Breast Milk in the European Union

 19881993Change
Rural28.217.737% decrease
Urban29.519.235% decrease
Industrial35.92433% decrease

As would be expected, industrial areas generally have higher levels.20 Populations exposed to such local sources of dioxin emission as waste incinerators may have even higher values. Data illustrating trends in breast milk dioxin levels as well as unique exposure situations are presented below. The examples are divided into four types:

  • Time trend examples -- studies that have looked at average levels of dioxins and furans in breast milk in a location over a number of years

  • Differences in average levels among different countries

  • Comparisons and differences within countries

  • Occupational exposure to dioxins and furans


Time Trends

Coordinated WHO studies in Europe have provided data over the seven-year period from 1986 to 1993. During this period, average dioxin levels appear to have decreased in many countries.21 Figure 2 reflects this data.


Figure 2

Figure 2


Researchers have also demonstrated a nearly 70-percent decrease in combined dioxin and furan levels in New Zealand breast milk between 1988 and 1998, shown in Figure 3.22 The study procedures and selection criteria for the 1988 study were replicated a decade later to test the breast milk of a very similar group of women in the same four areas of New Zealand. The principle objective of the 1998 study was to test whether a number of New Zealand regulatory measures -- all of which went into effect either not long before the first study or during the period between the two studies -- helped reduce exposures to organochlorine pollutants, as they were intended to. The regulatory measures included:

  • Production of a widely used herbicide (2,4,5-trichlorophenoxyacetic acid) that contained the most toxic dioxin congener (2,3,7,8-TCDD) was stopped in 1987.

  • Pentachlorophenol (PCP), a lumber treatment chemical that contained a wide range of furan compounds, was deregistered in 1991.

  • New Zealand's pulp and paper plants began to stop using elemental chlorine in their paper-processing operations during this decade.

  • Several aging and heavily polluting medical waste incinerators and metal smelters were decommissioned.

  • PCBs were prohibited for import in 1986, and storage of PCBs within the country was prohibited in 1995.

  • DDT, dieldrin and gamma-HCH (lindane) were deregistered in 1992, and chlordane was deregistered in 1992; these pesticides may contain dioxins as impurities.

Figure 3 demonstrates an important decrease in dioxin and furan levels between 1988 and 1998. Of course, it would be very difficult to prove that reductions resulted directly or solely from these regulatory actions, since a number of other factors, including nonregulatory incentives and subtle differences in the study population, could have contributed to these results. However, the study is valuable because it shows that it may be possible for countries to make progress in decreasing dioxin and furan levels through regulatory efforts, despite the difficulties faced in attempting to ban or restrict byproduct compounds.23


Figure 3

Figure 3


Scientists also gathered extensive data measuring dioxin in breast milk in Sweden. The research, presented in Figure 4, shows a downward trend in average breast milk levels over the last 25 years.24


Figure 4

Figure 4


Data from the North Rhine Westphalia region of Germany has also shown a downward trend in breast milk dioxin levels.25 The data from this series of studies is presented in Figure 5.


Figure 5

Figure 5


In many other countries, it has been difficult to make a national assessment of whether levels are going down because different regions have shown different trends. For instance, in Croatia, average breast milk levels of dioxin in Krk decreased between 1986 and 1988, while in Zagreb, they increased.26 Similarly, findings in Finland and Kazakhstan showed different trend lines for different regions.27


International Comparisons

Figure 6 shows high international variability in combined dioxin and furan levels in breast milk measured in 21 countries during the late 1980s and 1990s. The data from various international studies in this graph reflect the most recent research and are the product of similar methodologies and adequate sample sizes. That said, international comparisons of contaminants in breast milk are difficult to make because of wide variations in data-collection and reporting methods, because few studies were conducted in the same year and because some of the sample populations may reflect higher or lower exposure levels than the national averages.

Several of the studies compared in Figure 6 are examples of unique or particularly high dioxin and furan exposure. The levels shown for Belgium, Jordan, Kazakhstan, Russia and Vietnam are significantly higher than national averages, and the circumstances researchers suspect caused these elevated results are discussed below.

The breast milk samples from Belgium and Russia were from women living in and around the highly industrialized regions of Wallonia in Belgium and the Irkutsk region of Russian Siberia. Dioxin and furan byproducts of industrial processes are thought to enter local food supplies at higher rates in these areas than in less industrialized regions.

The samples taken from Jordan were from five different cities, but one of the cities had particularly high dioxin and furan levels as a result of differences in the food supply. In this city, the diet consisted almost completely of locally produced food. Public bakeries used diesel and/or a mixture of diesel and motor oil for heating the ovens in which they bake bread. Thus, the bread served as a major local exposure pathway for furans, and also for dioxins, albeit to a lesser degree.28 On the other hand, many of the women in this study had given birth to more than one child, some as many as eight. Normal protocol is to use only milk from women nursing their first child. This difference may have decreased or eliminated the upward bias created by the food supply, since breast milk pollutant concentrations have been shown to decrease significantly over time nursed and number of children nursed.29

The breast milk samples used for the Kazakhstan and Vietnam data were from women living in areas with histories of heavy use of chemical defoliants. In central Vietnam, where the samples for this data were collected, the United States conducted numerous Agent Orange spraying missions during the Vietnam War. In southern Kazakhstan, chemical defoliants were used beginning in the 1950s, and cotton fields were aerially sprayed for two decades. Research suggests this resulted in direct exposure and significant contamination of the region's food supply. These studies are described in greater detail in the section on national variations in dioxin and furan levels.


Figure 6

Figure 1



Unique Exposure Scenarios: The Effect of Diet

Despite the higher-than-average exposures shown for some countries, Figure 6 helps to illustrate that dioxin and furan exposures occur principally through bioaccumulation in the food chain and human consumption of foods rich in animal fat. In nations such as the Netherlands, Finland, South Korea and Japan, where the diet has a higher proportion of fatty fish, red meat and dairy products, elevated dioxin and furan concentrations in breast milk may be an indication of higher dietary exposure than in such nations as China and Vietnam, where diets generally have a lower fat content.

In many studies, diet emerges as the single most important factor in dioxin exposure.30 But the effects of lifelong accumulation of dioxin must be considered, not just recent exposures. Usually, the levels of dioxin found in breast milk that come from diet are a combination of all of the exposures a woman has had over her lifetime.

A study in South Africa demonstrates the point. The study looked at dioxin in breast milk in both black and white women and found that white women had higher levels of dioxin. Industrial pollution in South Africa is pervasive or worse in areas where black women were likely to live, so the disparity could not have been due to location. Eventually, the difference was attributed to diet: the white women in the study were from a higher socioeconomic class than the black women, and were therefore more likely to eat meat, milk, eggs, cheese and fish.31 Black women were more likely to eat grains and vegetables than meat and dairy products. Foods derived from animals or animal products have been shown to be much higher in dioxin content. Thus, exposure was much higher for the white women in this study population.

Similarly, researchers have found lower levels of dioxin in breast milk in vegetarian mothers in Germany compared to breast milk of women who ate a diet rich in meat.32 Vegetarians consume only 2 percent of the dioxin load of the general population because their diet is dominated by foods low on the food chain.33

Sometimes congener patterns of dioxins in breast milk can help to identify the source of exposure. In Finland, significant differences in the congener makeup of dioxins in breast milk emerged in different regions of the country. Researchers eventually traced the differences to the types of fish consumed in these regions. Different species of fish were contaminated with different congener combinations.34


National Variations in Dioxin and Furan Concentrations

As noted, concentrations of dioxins in breast milk in Vietnam were especially high after intensive aerial spraying of Agent Orange between 1965 and 1970 in southern and central Vietnam.35 In addition to the aerial spraying, the United States had several military bases in the Aluoi Valley, where Agent Orange spills of up to 7,500 gallons occurred during the war. Agent Orange was highly contaminated with dioxin, and studies of the region's soil, fish fat, duck fat and human blood and breast milk show that it bioaccumulated in the food chain to high concentrations.36 Figure 7 shows that dioxin and furan levels in breast milk collected between 1996 and 1999 from women in the Aluoi Valley in central Vietnam were about six times higher than those in breast milk collected in 1988 in the city of Hanoi in northern Vietnam, where no Agent Orange was sprayed.37 The reported difference between these two regions might have been even greater if they had both been taken at the same time, since contaminant levels from past exposure decrease over time.


Figure 7

Figure 7


A similar pattern of exposure was in evidence in Kazakhstan, where especially high levels of dioxins in breast milk resulted from exposure to chemical defoliant spray.38 In southern Kazakhstan, women were found to have some of the world's highest levels of the most toxic form of dioxin (2,3,7,8-TCDD) in their breast milk. Between 1994 and 1996, researchers measured levels three times greater in women from rural areas than in women from urban areas in this region. Extensive use of chemical defoliants on cotton crops in this region began in the 1950s, and crops were aerially sprayed between 1965 and 1985. In 1997, researchers recruited all first-time mothers in and surrounding the region shown to be most contaminated in the 1994-1996 study, in order to better understand the highest exposures. Figure 8 shows that women in Zone A, living adjacent to a large lake that served as the catchment for all the agricultural runoff in the region, had 57-percent higher contamination levels than women in Zone B, which was farther away from the lake. Further, women in Zone A had worked picking cotton for an average of twice the number of years during the aerial spraying period that women in Zone B worked. Since dioxin levels in the fish from the lake were not tested, it is not possible to say with certainty whether food contamination or occupational exposure increased breast milk contamination levels by a larger amount, but the levels in Zone A are far higher than those documented in other populations.39


Figure 8

Figure 8


The complexities of regional dioxin and furan contamination are further demonstrated by Figure 9, which shows breast milk concentrations of dioxins and furans in two regions in Canada. Samples taken from women across southern, industrialized Canada in 1992 show levels that are 67 percent higher than those taken from indigenous residents in northern Canada's District of Keewatin in 1997. The District of Keewatin is on the west coast of Hudson's Bay. Some of this difference could be because the southern samples were obtained five years earlier than the northern samples. Or the difference could be due to the nonindustrial nature of the Keewatin region. However, without data on dioxin and furan levels in food it is difficult to fully explain this discrepancy.40


Figure 9

Figure 9



Occupational Exposure

In addition to exposure through the diet, some studies strongly suggest that occupational exposures are capable of affecting concentrations of dioxins and furans in the body as well. For example, researchers have conducted several studies measuring breast milk and blood concentrations of dioxins and furans in the Irkutsk Region of Russian Siberia. The Irkutsk Region is located northwest of Lake Baikal, and it has been of particular interest for research because it is a very highly industrialized area. Three of the larger towns in the region collectively employ more than 60,000 workers in their numerous petrochemical, chemical, biochemical and pharmaceutical facilites and two hazardous waste incinerators are operated in the area as well.41

Figure 10 shows the results from a recent study that compared blood dioxin and furan levels in residents of the Irkutsk Region with those in workers in two of the region's largest organochlorine chemical factories. Pooled breast milk samples from women in four other regions of Russian Siberia were collected a decade earlier by the same researcher, and they are included in Figure 10 to permit a comparison between exposure levels in less intensively industrialized areas. Samples of breast milk and blood can be compared in this case because all samples were adjusted for the amount of fat per gram of fluid.42

The chemical workers averaged 37 percent higher blood dioxin and furan levels than the Irkutsk Region residents. Similarly, the chemical workers' dioxin and furan levels were about 70 percent higher than were found in the pooled breast milk samples from the other four regions, indicating that workplace exposure may be an important pathway for human contamination in this region. The Irkutsk residents' blood levels were about 53 percent higher than those in the earlier pooled breast milk samples, showing that in addition to workplace exposures, the Irkutsk Region appears to have significantly higher dioxin and furan exposure levels overall.


Figure 10

Figure 10


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Notes

1. IARC, Polychlorinated Dibenzo-para-dioxins and Polychlorinated Dibenzofurans, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, ed. W.H.O.I.A.f.R.o., Cancer, Vol. 69. Lyon (1997).

2. Ibid.

3. U.S. EPA, Exposure and Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds, U.S. Environmental Protection Agency: Washington DC (2000).

4. ATSDR, ToxFAQs for Chlorinated Dibenzo-p-Dioxins (CDDs), ATSDR (1999).

5. Dewailly, E., et al. "Exposure of Remote Maritime Populations to Coplanar PCBs," Environmental Health Perspectives Journal 102(Suppl 1) (1994): pp. 205-209.

6. ATSDR, ToxFAQs for Chlorinated Dibenzo-p-Dioxins (CDDs), ATSDR (1999).

7. Ibid.

8. Ibid.

9. Brouwer, A., et al. "Report of the WHO Working Group on the Assessment of Health Risks for Human Infants from Exposure to PCDDs, PCDFs and PCBs," Chemosphere 37(9-12) (1998): pp. 1627-1643.

10. WHO, Levels of PCBs, PCDDs and PCDFs in Human Milk, WHO European Centre for Environment and Health: Bilthoven (1996);Schecter, A., et al. Dioxins, "Dibenzofurans and Selected Chlorinated Organic Compounds in Human Milk and Blood from Cambodia, Germany, Thailand, the U.S.A., the U.S.S.R., and Vietnam," Chemosphere 23 (1991) pp. 1903-1912; Alawi, M.A., et al. "Dioxins and Furans in the Jordanian Environment, Part 2: Levels of PCDD and PCDF in Human Milk Samples from Jordan," Chemosphere 33(12) (1996): pp. 2469-74.

11. Brouwer, A., et al. "Report of the WHO Working Group on the Assessment of Health Risks for Human Infants from Exposure to PCDDs, PCDFs and PCBs," Chemosphere 37(9-12) (1998) pp. 1627-1643.

12. Rogan, W.J., et al. "Should the Presence of Carcinogens in Breast Milk Discourage Breast Feeding?" Regulatory Toxicology and Pharmacology 13 (1991): pp. 228-240.

13. Schecter, A., et al. "Congener-specific Levels of Dioxins and Dibenzofurans in U.S. Food and Estimated Daily Toxic Eequivalent Intake," Environmental Health Perspectives Journal 102(11) (1994) pp. 962-966.

14. IARC, Polychlorinated Dibenzo-para-dioxins and Polychlorinated Dibenzofurans, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, ed. W.H.O.I.A.f.R.o., Cancer, Vol. 69. Lyon (1997).

15. Ibid.

16. Schecter, A., et al. "Chlorinated Dioxins and Dibenzofurans in Human Tissue from General Populations: A Selective Review," Environmental Health Perspectives Supplements 102(Supple 1) (1994): pp. 159-171.

17. Dewailly, E., et al. "Exposure of Remote Maritime Populations to Coplanar PCBs," Environmental Health Perspectives Journal 102(Suppl 1) (1994): pp. 205-209.

18. Peterson, A., Compilation of European Union Dioxin Exposure and Health Data Task 5 - Human Tissue and Milk Levels, 1999, European Commission Environment and UK Department of the Environment, Transport and the Regions: Oxfordshire.

19. Ibid.

20. Ibid.

21. Yrjanheikki, E.J., Levels of PCBs, PCDDs and PCDFs in Breast Milk: Results of WHO Coordinated Interlaboratory Quality Control Studies and Analytical Field Studies, 1989: Copenhagen; Clench-Aas, J., et al. "PCDD and PCDF in Human Milk from Scandinavia, with Special Emphasis on Norway," Journal of Toxicology and Environmental Health 37 (1992): pp. 73-83; Startin, J.R., M. Rose, and C. Offen, "Analysis of PCDDs and PCDFs in Human Milk from the UK," Chemosphere 19 (1989): pp. 985-88; Wearne, S.J., et al. "Time Trends in Human Dietary Exposure to PCDDs, PCDFs and PCBs in the UK," Organohalogen Compounds 31: (1996): pp. 1-6.

22. Bates, M.N., B. Thomson, N. Garrett, "Reduction in Organochlorine Levels in the Milk of New Zealand Women," Archives of Environmental Health vol. 57, no. 6 (November/December 2002): pp. 591-597.

23. Ibid.

24. Lunden, A. and K. Noren, "Polychlorinated Naphthalenes and Other Organochlorine Contaminants in Swedish Human Milk, 1972-1992," Archives of Environmental Contamination and Toxicology 34 (1998): pp. 414-23; Noren, K. and D. Meironyte, "Certain Organochlorine and Organobromine Contaminants in Swedish Human Milk in Perspective of Past 20-30 Years," Chemosphere 40 (2000): pp. 1111-1123.

25. WHO, Levels of PCBs, PCDDs and PCDFs in Human Milk, WHO European Centre for Environment and Health: Bilthoven (1996); Deml, E., I. Mangelsdorf, and H. Greim, "Chlorinated Dibenzodioxins and Dibenzofurans (PCDD/F) in Blood and Human Milk of Non-occupationally Exposed Persons Living in the Vicinity of a Municipal Waste Incinerator," Chemosphere 33 (1996): pp. 1941-1950; Beck, H., A. Dross, and W. Mathar, "Dependence of PCDD and PCDF Levels in Human Milk on Various Parameters in Germany II," Chemosphere ; 25 (1992): pp. 1015-20; Beck, H., et al. "Dependence of PCDD and PCDF Levels in Human Milk on Various Parameters in the Federal Republic of Germany," Chemosphere ; 18 (1989): pp. 1063-66; Beck, H., A. Dross, and W. Mathar, "PCDD and PCDF Exposure and Levels in Humans in Germany," Environmental Health Perspectives Journal 102(Suppl 1) (1994): pp. 173-185; Frommberger, R., "Polychlorinated Dibenzo-p-dioxins and Polychlorinated Dibenzofurans in Cumulative Samples of Human Milk from Baden-Wurttemberg, FRG," Chemosphere , 20 (1990): pp. 333-42; Papke, O. "PCDD/PCDF: Human Background Data for Germany, a 10-Year Experience," Environmental Health Perspectives Journal 106(Suppl 2) (1998): pp. 723-731; Furst, P., et al. "PCDD and PCDF Levels in Human Milk -- Dependence on Period of Lactation," Chemosphere 18 (1989): pp. 439-44.

26. WHO, Levels of PCBs, PCDDs and PCDFs in Human Milk, WHO European Centre for Environment and Health: Bilthoven (1996); Yrjanheikki, E.J., Levels of PCBs, PCDDs and PCDFs in Breast Milk: Results of WHO Coordinated Interlaboratory Quality Control Studies and Analytical Field Studies, Copenhagen (1989).

27. Ibid; Hooper, K., et al. "Analysis of Breast Milk to Assess Exposure to Chlorinated Contaminants in Kazakhstan: Levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in Agricultural Villages of Southern Kazakhstan," Environmental Health Perspectives Journal 106(12) (1998): pp. 797-806; Hooper, K., et al. "Analysis of Breast Milk to Assess Exposures to Chlorinated Contaminants in Kazakhstan: Sources of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) Exposure in an Agricultural Region of Southern Kazakhstan," Environmental Health Perspectives Journal 107(6) (1999): pp. 447-456; Petreas, M., et al. "Analysis of Human Breast Milk to Assess Exposure to Chlorinated Contaminants in Kazakhstan," Organohalogen Compounds 30 (1996): pp. 20-23.

28. Alawi, M.A., et al. "Dioxins and Furans in the Jordanian Environment, Part 2: Levels of PCDD and PCDF in Human Milk Samples from Jordan," Chemosphere 33(12) (1996): pp. 2469-74.

29. Schecter, A, J.J. Ryan, O. Papke. "Decrease in Levels and Body Burden of Dioxins, Dibenzofurans, PCBs, DDE, and HCB in Blood and Milk in a Mother Nursing Twins Over a Thirty-Eight Month Period," Chemosphere vol. 37, no. 9-12 (1998): pp. 1807-1816. Iida, T., H. Hirakawa, T. Matsueda, S. Takenaka,J. Nagayama, "Polychlorinated Dibenzo-p-dioxins and Related Compounds in Breast Milk of Japanese Primiparas and Multiparas," Chemosphere vol. 38, no. 11 (1999): pp. 2461-2466.

30. Brouwer, A., et al. "Report of the WHO Working Group on the Assessment of Health Risks for Human Infants from Exposure to PCDDs, PCDFs and PCBs," Chemosphere 1998; 37(9-12): p. 1627-1643.

31. Schecter, A., et al. "Chlorinated Dioxins and Dibenzofurans in Human Tissue from General Populations: A Selective Review," Environmental Health Perspectives Supplements 102(Supple 1) (1994)" pp. 159-171.

32. Somogyi, A., "Nuturing and Breast-feeding: Exposure to Chemicals in Breast Milk," Environmental Health Perspectives Journal 101(Suppl 2) (1993): pp. 45-52.

33. Schecter, A., et al. "Congener-specific Levels of Dioxins and Dibenzofurans in U.S. Food and Estimated Daily ToxicEequivalent Intake," Environmental Health Perspectives Journal 102(11) (1994): pp. 962-966.

34. Vartiainen, T., et al. "PCDD, PCDF, and PCB Concentrations in Human Milk from Two Areas in Finland," Chemosphere 34(12) (1997): pp. 2571-2583.

35. . Lutter, C., et al. "Breast Milk Contamination in Kazakhstan: Implications for Infant Feeding," Chemosphere 37(9-12) (1998): pp. 1761-72.

36. Dwernychuk, L.W., H.D. Cau, C.T. Hatfield, T.G. Boivin, T.M. Hung, P.T. Dung, N.D. Thai. "Dioxin Reservoirs in Southern Vietnam - A Legacy of Agent Orange," Chemosphere vol. 47, no. 2 (November/December 2002): pp.117-137.

37. Dai, et al. "Remarks On the Dioxin Levels in Human Pooled Blood from Various Localities of Viet Nam," Organohalogen Compounds vol. 26 (1995): pp. 161.; Schecter A. "A Selective Historical Review of Congener-Specific Human Tissue Measurements as Sensitive and Specific Biomarkers of Exposure to Dioxins and Related Compunds," Environmental Health Perspectives vol. 106, Supp. 2 (April1998): pp. 737-742.

38. Hooper, K., et al. "Analysis of Breast Milk to Assess Exposures to Chlorinated Contaminants in Kazakhstan: Sources of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) Exposure in an Agricultural Region of Southern Kazakhstan," Environmental Health Perspectives Journal 107(6) (1999): pp. 447-456.

39. Hooper, K., T. Chuvakova, G. Kazbekova, D. Hayward, A. Tulenova, M.X. Petreas, T.J. Wade, K. Benedict, Y.Y. Cheng, J. Grassman, "Analysis of Breast Milk to Assess Exposures to Chlorinated Contaminants in Kazakhstan: Sources of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) Exposure in an Agricultural Region of Southern Kazakhstan," Environmental Health Perspectives Journal vol. 107, no. 6 (June 1999): pp. 447-456; Hooper, K., M.X. Petreas, T, Chuvakova, G. Kazbekova, N. Druz, G. Seminova, T. Sharmanov, D. Hayward, J. She, P. Visita, J. Winkler, M. McKinney, T.J. Wade, J. Grassman, R.D. Stephens. "Analysis of Breast Milk to Assess Exposure to Chlorinated Contaminants in Kazakhstan: High Levels of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) in Agricultural Villages of Southern Kazakhstan," Environmental Health Perspectives vol. 106, no. 12 (December 1998): pp. 797-806.

40. Newsome, W.H. and J.J. Ryan, "Toxaphene and Other Chlorinated Compounds in Human Milk from Northern and Southern Canada: A Comparison," Chemosphere vol. 39, no. 3 (1999): pp. 519-526.

41. Schecter, A., M. Pavuk, D.A. Amirova, E.I. Grosheva, O. Papke, J.J. Ryan, J. Adibi, A.L. Piskac, "Characterization of Dioxin Exposure in Firefighters, Residents, and Chemical Workers in the Irkutsk Region of Russian Siberia," Chemosphere ; vol. 47, no. 2 (2002): pp. 147-156.

42. Schecter et al., "Characterization of Dioxin Exposure in Firefighters, Residents, and Chemical Workers in the Irkutsk Region of Russian Siberia," Chemosphere vol. 47, no. 2 (2002): pp. 147-156; Schecter, A. A.L. Piskac, E.I. Grosheva, N.I. Matorova, J.J. Ryan, P. Furst, O. Papke, J. Adibi, M. Pavuk, A. Silver, S. Ghaffar, "Levels of Dioxins and Dibenzofurans in Breast Milk of Women Residing in Two Cities in the Irkutsk Region of Russian Siberia Compared with American Levels," Chemosphere vol. 47, no. 2 (2002): pp. 157-164.



Cites for International Studies Used in Comparison Chart

Belgium - Yang, J., D. Shin, S. Park, Y, Chang, D, Kim, M.G. Ikonomou, "PCDDs, PCDFs, and PCBs Concentrations in Breast Milk from Two Areas in Korea: Body Burden of Mothers and Implications for Feeding Infants, " Chemosphere vol. 46: no.3 (2002): pp. 419-428.

Brazil - Paumgartten, F.J., C.M. Cruz, I. Chahoud, R. Palavinskas, W. Mathar, C.M. Cruz, I. Chahoud, R. Palavinskas, W. Mathar, "PCDDs, PCDFs, PCBs, and Other Organochlorine Compounds in Human Milk from Rio de Janeiro, Brazil," Environmental Research Section A vol. 83, no. 3 (2000): pp. 293-297.

Canada - Ryan, J.J., R. Lizotte, L.G. Panopio, C, Shewchuk, D.A. Lewis, W.F. Sun, "Polychlorinated Dibenzo-p-dioxins (PCDDs) and Polychlorinated Dibenzo-furans (PCDFs) in Human Milk Samples Collected Across Canada in 1986-87," Food Additives and Contaminants vol. 10, no. 4 (1993): pp. 419-428.

China - Schecter, A., K. Jiang, O. Papke, P. Furst,C. Furst, "Comparison of Dibenzodioxin Levels in Blood and Milk in Agricultural Workers and Others Following Pentachlorophenol Exposure in China," Chemosphere vol. 29 no. 9-11, (Nov-Dec, 1994): pp. 2371-2380.

Czech Republic - Bencko, V., Z. Skulova, M. Krecmerova, A.K. Liem, "Selected Polyhalogenated Hydrocarbons in Breast Milk," Toxicology Letters vol. 96/97 (Aug. 1998): pp. 341-345.

Finland - Kiviranta, H., R. Purkunen, T. Vartiainen, "Levels and Trends of PCDD/Fs and PCBs in Human Milk in Finland," Chemosphere vol. 38, no. 2 (1999): pp. 311-323.

France - Gonzalez, M.J., B. Jimenez, L.M. Hernandez, M.F. Gonnord, "Levels of PCDDs and PCDFs in Human Milk from Populations in Madrid and Paris," Bulletin of Environmental Contaminants and Toxicology 1996; vol. 56, no. 2, p. 197-204.

Germany - Papke, O., "PCDD/PCDF: Human Background Data for Germany, a 10-Year Experience," Environmental Health Perspectives vol. 106, Supp. 2, (1998): pp. 723-731.

Japan - Iida T, H. Hirakawa, T. Matsueda, S. Takenaka, J. Nagayama, "Polychlorinated Dibenzo-p-dioxins and Related Compounds in Breast Milk of Japanese Primiparas and Multiparas," Chemosphere vol. 38, no. 11 (1999): pp. 2461-2466.

Jordan - Alawi, M.A., H. Wichmann, W. Lorenz, M. Bahadir, "Dioxins and Furans in the Jordanian Environment, Part 2: Levels of PCDD and PCDF in Human Milk Samples from Jordan," Chemosphere vol. 33, no. 12, (1996): pp. 2469-2474.

Lithuania - Becher, G., J.U. Skaare, A. Polder, B. Sletten, O.J. Rossland, H.K. Hansen, J. Ptashekas, "PCDDs, PCDFs, and PCBs in Human Milk from Different Parts of Norway and Lithuania," Journal of Toxicology and Environmental Health vol. 46, no. 2 (1995): pp. 133-148.<

b> Netherlands - Tuinstra, T.G., M. Huisman, E.R. Boersma, "The Dutch PCB/Dioxin. Contents of Dioxins, Planar and Other PCBs in Human Milk for Rotterdam and Groningen Area," Chemosphere vol. 29, no. 9-11 (1994): pp. 2267-2277.

New Zealand - Bates, M.N., B. Thomson, N. Garrett, "Reduction in Organochlorine Levels in the Milk of New Zealand Women," Archives of Environmental Health vol. 57, no. 6 (2002): p. 591-597.

Norway - Becher, G., J. U. Skaare, A. Polder, B. Sletten, O.J. Rossland, H.K. Hansen, J. Ptashekas, "PCDDs, PCDFs, and PCBs in Human Milk from Different Parts of Norway and Lithuania," Journal of Toxicology and Environmental Health vol. 46, no. 2 (1995): pp. 133-148.

Russia - Schecter, A., A.L. Piskac, E.I. Grosheva, N.I. Matorova, J.J. Ryan, P. Furst, O. Papke, J. Adibi, M. Pavuk, A. Silver, S. Ghaffar., "Levels of Dioxins and Dibenzofurans in Breast Milk of Women Residing in Two Cities in the Irkutsk Region of Russian Siberia Compared with American Levels," Chemosphere vol. 47, no. 2 (2002): pp. 157-164.

South Korea - Yang, J., D. Shin, S. Park, Y. Chang, D. Kim, M.G. Ikonomou, "PCDDs, PCDFs, and PCBs Concentrations in Breast Milk from Two Areas in Korea: Body Burden of Mothers and Implications for Feeding Infants," Chemosphere vol. 46, no. 3 (2002): pp. 419-428.

Spain - Schuhmacher, M., J.L. Domingo, J.M. Llobet, H. Kiviranta, T. Vartiainen, PCDD/F Concentrations in Milk of Nonoccupationally Exposed Women Living in Southern Catalonia, Spain, Chemosphere, 1999; vol. 38, no. 5, p. 995-1004.

Sweden - Noren, K. and D. Meironyte, "Certain Organochlorine and Organobromine Contaminants in Swedish Human Milk in Perspective of Past 20-30 Years," Chemosphere vol. 40, no. 9-11 (2000): pp. 1111-1123.

United States - Schecter, A.,A.L. Piskac, E.I. Grosheva, N.I. Matorova, J.J. Ryan, P. Furst, O. Papke, J. Adibi, M. Pavuk, A. Silver, S. Ghaffar, "Levels of Dioxins and Dibenzofurans in Breast Milk of Women Residing in Two Cities in the Irkutsk Region of Russian Siberia Compared with American Levels," Chemosphere vol. 47, no. 2 (2002): p. 157-164.

Vietnam - Dwernychuk, L.W., H.D. Cau, C.T. Hatfield, T.G. Boivin, T.M. Hung, P.T. Dung, N.D. Thai, "Dioxin Reservoirs in Southern Vietnam - A Legacy of Agent Orange," Chemosphere vol. 47, no. 2 (2002): pp. 117-137.

last revised 3.25.05

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