Healthy Milk, Healthy Baby
Chemical Pollution and Mother's Milk
BACK TO CHEMICAL OVERVIEW
DDT (dichlorodiphenyltrichloroethane) is a commercial organochlorine insecticide that has been used in countries around the world. It has been used widely on agricultural crops as well as for "vector control" -- the control of insects that carry such diseases as malaria and typhus.1
In the 1960s, scientists began to notice that DDT could cause damage to wildlife, and that it had the potential to harm human health. Those findings prompted increased international attention to DDT's impact on wildlife and humans, which in turn triggered a number of international restrictions on the pesticide. It also led to increased awareness of the long-term effects of other pesticides and industrial chemicals. Nevertheless, DDT is still used in many parts of the world, and its persistence in the environment poses a danger for ecosystems and human beings.
DDT in the Body
DDT is found in the environment in three forms: the parent compound, DDT and two forms into which DDT degrades once released into the environment, DDE (dichlorodiphenylchloroethane) and DDD (dichlorodiphenyldichloroethane). DDE is DDT's main metabolite and also the most persistent form of the chemical. However, DDD also occurs as a breakdown product, and in some instances is independently used as a pesticide.
Whether used in agriculture or for vector control, once DDT enters the environment, it can remain for many years. DDT can be transported in different ways. In air, DDT degrades very quickly, with breakdown occurring in less than five days. However, people and animals can be directly exposed by air at the time of initial application. DDT is far more persistent in water and soil. In water, it does not easily dissolve, but instead attaches to sediment particles or is broken down by microorganisms into DDE and some DDD. In soil, DDT lasts for a very long time because it binds strongly to soil particles. Once attached, DDT and its byproducts can persist for as long as 15 years. Moreover, when bound to soil particles, DDT can begin to bioaccumulate, building up in plants and in the fatty tissue of the fish, birds and animals that eat the plants.2
The breakdown of DDT into the metabolites DDE and DDD depends on several factors, including climate -- temperature and humidity, for example -- and the presence in soil and water of microorganisms. Thus, country-by-country differences in DDT metabolite levels may emerge, depending on local geography and climate. In some wet, tropical areas, DDT has been found to break down more quickly than in dry regions.3
Humans can be exposed to DDT and its metabolites in several ways. The principle route of exposure is the consumption of foods, particularly leafy and root vegetables, fatty meat, fish and poultry.4 The levels of chemicals absorbed in food usually reflect the contamination present in the country of production.
Although DDT contamination can occur in a variety of food products, the most serious contamination usually occurs in fish and other organisms high on the food chain that themselves have bioaccumulated DDT. Other less common routes of exposure that are considered minor are breathing contaminated air or drinking contaminated water, especially near waste sites and landfills or in recently treated homes; and breathing or swallowing dust or soil particles near waste sites and landfills or in recently treated homes.5
DDT's elimination from the body can take some time; its half-life (the time it takes to eliminate half of a certain dose of the chemical) in humans has been estimated at four years. DDE's half-life is estimated at approximately six years.6 Because of these varying breakdown rates, the proportion of DDT and DDE detected in human tissues can be used as an indication of the length of time since exposure. In areas where DDT exposure has been recent, the DDE/DDT ratio is low, while in areas where substantial time since exposure has passed, the DDE/DDT value is higher. Because DDE is attracted to fat, levels in breast milk are often six to seven times higher in a mother's milk than in her blood.7
Controlling Exposure: Bans and Restrictions
DDT has been banned or restricted in 57 countries, and a total of 102 countries have made it illegal to import DDT.8 In countries with "restricted" use, DDT has often been designated for application in malaria control, even while limitations or bans on agricultural use may have been put in place. The effectiveness of bans and restrictions differs from country to country depending on enforcement efforts. Thus, relying on the official ban date as an indicator for decreasing use can be misleading. Worse still, DDT is often produced, imported, and/or exported to and from countries despite bans and restrictions. For instance, despite a longstanding ban, the United States exported more than 96 tons of DDT in 1991.9 A study by the Foundation for Advancement in Science and Education found that banned chemicals are often exported to countries that also have banned the chemical.10
Bans and restrictions do not immediately yield decreased detection of DDT in breast milk because of the chemical's persistence. However, it is clear that banning DDT use can eventually lead to declines in exposure and drops in detectable residue levels. Since exposure can occur through food, and since global food security relies on the import and export of food crops, a worldwide ban is the only real solution to exposure.
Assessing the Extent of DDT 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 DDT, conclusive evidence demonstrating that any one of these benchmarks is protective or superior to the others does not exist. DDT has also been associated with shortened duration of lactation and difficulty producing breast milk, but the benchmark levels may not protect against adverse effects on lactation.11 Conversely, there are no data linking exposure to DDT via breast milk with specific health outcomes. However, many scientists consider any level of contamination unacceptable and believe that benchmark levels are not protective.
In 1984, the World Health Organization (WHO) established an acceptable daily intake (ADI) level for children's consumption of DDT in milk. This value of 20 micrograms per kilogram per day (µg/kg/day) can be converted into an "acceptable contamination level" of between 5,000-6,000 µg/kg DDT in milk fat.12
Most countries' current (1990) average DDT residue level in breast milk is now below this standard. However, a number of countries and particular regions have average levels well above the WHO standard. An examination of data from periods of heavy DDT use in the 1960s and 1970s shows that many countries' levels surpassed the WHO benchmark at one point or another.
Breast Milk Monitoring Studies and DDT
Researchers around the world have published more than 200 values for detectable levels of DDT in human breast milk. Studies have been conducted in the following countries:
|Belgium||Hong Kong, China||Nigeria||Thailand|
|Canada||India||Papua New Guinea||Turkmenistan|
|Costa Rica||Israel||Rumania||United Kingdom|
|Czech Republic||Italy||Russia||United States|
|El Salvador||Kazakhstan||South Africa||Wales|
Although studies have been conducted in all of these countries, data are not always complete. The following section discusses issues that make it difficult to interpret the data. In addition, countries not on this list may also have detectable levels of DDT residues in breast milk, since the list reflects only those areas where studies have been conducted.
Limitations of Studies Measuring DDT in Breast Milk
It is often difficult to draw conclusions about national and international trends in DDT contamination because of the many factors affecting measured levels, and because of limitations in the way data are reported. Some of these challenges include:
- Absence of standardized methodology. No accepted and standardized method for conducting breast milk monitoring studies has been established. Thus, differences may arise in the sampling time -- when the breast milk is collected or in the birth histories of the mothers -- women who have breast-fed multiple children might be mixed in with women who are breastfeeding for the first time.
- Distinct regional differences in DDT use. Many countries have a clear demarcation between agricultural and urban zones. In such situations, general averages are inadequate because they do not reveal peak levels in areas with heavy agricultural use. The same problem arises in countries where DDT has been used for vector control only in specific regions. Again, average values will not adequately represent the unique exposure situations in these areas.
- Few studies. Many countries do not have multiple studies over a range of time. Instead, the information on DDT residues may be nothing more than a snapshot of a particular time. Where that is the case, it is difficult to generalize about how the conditions in a country have changed over time.
- Small study populations. Because of the cost and time involved, many studies measuring DDT levels in breast milk test only a few people. When the only data for a country are from studies with very small sample sizes, it is difficult to draw conclusions about the entire population.
- Differences in measurement methodology and data reporting. Although many studies look at and report the total concentration of DDT (in all its metabolite forms) in breast milk, some only look at the levels of the metabolite DDE. This complicates data comparisons and may underestimate the effects of recent exposures.
- Bias. The selection of study participants often presents challenges. In many studies, women may have been chosen to participate based on potentially high exposure to the chemical of interest, thereby possibly making some of the numbers higher than the average for the general population.
Some Important Examples of DDT in Breast Milk
Several useful studies on DDT are available.
In general, studies looking at DDT levels in breast milk have shown that as DDT use has declined and changed, detectable levels in breast milk have also declined. Levels are usually much lower in developed nations than in developing countries -- not surprising, since many developed nations restricted or banned DDT in the 1970s, while restrictions in the developing world were not common until the 1980s.
Despite the overall trend of decreasing DDT levels in breast milk, ongoing challenges remain in some areas of the world. In some regions, DDT use for malaria vector control has made exposure common, and has led to high levels in breast milk. In other regions, continued use or disregard of bans and restrictions on agricultural use has led to widespread and high-level exposure.
Although measurements of DDT residues in breast milk have been taken in more than 60 countries, only a few nations have comprehensive trend data (multiple studies over time, large study populations, consistent analysis methods). Among those countries with such comprehensive data are some important environmental success stories.13 After the restriction and ban of DDT in some nations, average breast milk levels have decreased substantially. One study involving a statistical analysis of trend data from around the world found that the average national levels of DDT found in breast milk directly correlate with the time since DDT restriction.14 In other words, the longer DDT was restricted, the lower the average levels of DDT in breast milk.
The examples presented here are divided into four types:
- Time trend examples -- studies that have looked at average levels of DDT in breast milk in a location over a number of years
- Differences in average levels among different countries
- Comparisons and differences within countries depending on different regional use patterns
- Occupational exposure to DDT
Time Trend Examples
Sweden has excellent data from breast milk monitoring studies spanning more than 30 years. DDT levels in breast milk continuously declined from 1967 through 1997. The use of DDT was severely restricted in Sweden in 1970 and completely banned in 1975.15 Figure 1 shows the marked decrease in the average concentrations of DDT found in Swedish women's breast milk.
Germany has also witnessed a rapid decline in average concentrations of DDT in breast milk. Between 1969 and 1995, detectable residue levels decreased 81 percent. DDT was banned in Germany in 1972. However, trend data in Germany is difficult to assess on a national basis because East and West Germany had different use patterns before reunification.16 Figure 2 shows the declining trend of DDT residues in the former West Germany. The decline has been similar in the former eastern state, but the data are far less complete. In addition, the average concentrations in East Germany were much higher during the 1970s, with the highest detected residue levels (~11,500 µg/kg DDT in milk fat) recorded in Greifswald, East Germany, in 1971.17
Other countries where studies have revealed a downward trend include Canada, Denmark, Norway, Switzerland, Turkey, Yugoslavia, Czech Republic, United Kingdom, China (Hong Kong), Israel, India and Japan.
It is difficult to make comparisons between countries because relatively few studies were done at the same point in time. But in order to illustrate the vast differences in exposure from country to country, Figure 3 shows average national levels during the period from 1989 to 2000 for 28 different countries. Many industrialized nations banned or began to restrict the use of DDT during the 1970s, but at about the same time, use of DDT in developing nations was peaking. Thus, concentrations have steadily decreased in many industrialized nations, but exposure hot spots persist in countries where populations are still exposed to DDT through agricultural use, malaria control or contaminated food sources. Nations where DDT is still being used or has only recently been restricted, such as Zimbabwe and Tanzania, show higher concentrations of DDT than those where all DDT use has been phased out.18 Nations showing high concentrations of DDE but relatively low concentrations of DDT, such as Poland and Greenland, may indicate ongoing exposure to DDE through contaminated food sources, since DDT has not been used recently in those nations.19
This figure illustrates the wide variability between countries, although it has limitations in terms of estimating the true average concentrations of DDT in any single country. For some of the countries included in the table, multiple studies may have been conducted in the same time period. Where multiple studies were conducted, the study with the largest study population was included in the figure. Some of the included studies had very limited study populations but were included because no other data for that country existed. In addition, variations in the type of measurement methods used among studies must be considered. For example, Figure 3 shows relatively moderate DDT and DDE concentrations in breast milk in Mexico and Nicaragua, though levels have been shown to be much higher in some regions, given continued DDT use for agriculture and malaria control in both nations. The lower levels observed in the data from Nicaragua may be largely because all samples were pooled together, while milk fat content varied widely, and because the average number of children of women in the study was two, rather than one.20 Normally, breast milk pollutant levels are measured during a woman's first lactation because pollutant concentrations decrease significantly with additional lactations and duration of breastfeeding.21
National Variations in DDT Levels
In the United States, a pooling of all studies done in the last 50 years shows an overall continuous decrease in DDT levels in breast milk. However, distinct differences emerge between different states and regions. For example, regions of the United States with more intensive agriculture, such as the southeastern U.S., commonly had higher levels.22
Levels of DDT found in breast milk are not always higher in rural areas than in urban areas. Figure 4 presents 1989 data from Brazil. This study showed that urban areas had approximately twice the level of contamination as rural populations, likely the result of DDT applications for mosquito abatement in Brazil, particularly in urban areas.23
The difference between areas that currently apply DDT and those that have only the residue of past exposures is particularly evident in the data from Zimbabwe, presented in Figure 5. DDT was banned for agricultural use in Zimbabwe in 1982,24 but national averages for DDT and DDE in breast milk still show moderately high levels (~6,000 µg/kg in milk fat). Exposure is generally in the form of DDE, indicating that exposure to DDT was not recent. However, the Kariba region of Zimbabwe, the only region that still actively employs DDT for malaria control, shows much higher levels of total DDT residues.25 The pesticide's use in the Kariba region is mainly in the rainy season via aerial and ground spraying. DDT likely makes its way into rivers and the lake that is the region's main water source and supplier of fish, and humans are exposed when they eat DDT-contaminated fish.26
Data from Mexico also reveal regional differences in DDT levels found in breast milk. DDT was first restricted in Mexico in 1972. However, the restrictions were mainly put into place in northern Mexico, where pressure from the United States was strongest. DDT use continued in the southern part of the country for many years. DDT was finally restricted to vector control for the entire country beginning in 1990. Through this string of regulations, an overall gradual downward trend was seen in Mexico for DDT in breast milk.27
Despite this downward trend, regional data give cause for concern in those parts of Mexico where DDT continues to be used in malaria control. Figure 6 shows data from a 1998 study28 that showed distinct differences in breast milk levels related to DDT use for vector control. The suburban area of Veracruz City employs frequent malaria control because it is built on swampland. DDT is sprayed at least every six months on indoor surfaces and dwellings. Women from suburban areas of Veracruz have higher levels of DDT in their breast milk than do urban or rural residents of the same area. In addition, the ratio of DDE/DDT is lower in suburban women, suggesting that these women's residue levels stem from recent, direct exposure. In contrast, the women from the urban and rural areas have high DDE/DDT ratios suggesting that their breast milk levels have risen from historical exposures or from exposures through food.29
Occupational Exposure to DDT
Although studies of DDT concentrations based on geographic area are useful, they may obscure hot spots of high DDT concentrations that occur within small geographic areas as a result of occupational exposure. For example, Figure 7 shows a comparison of 1996 DDT and DDE levels in the fat of malaria control workers in Veracruz, Mexico, with DDT and DDE levels in the fat of women in the general population of Veracruz only one year later in 1997. The malaria control workers had 15 times greater concentrations of DDE, and 55 times greater concentrations of DDT than those in the general population, revealing high, ongoing exposures to DDT on the job.30
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Chlordane | DDT | Dieldrin, Aldrin and Endrin | Hexachlorobenzene | Hexachlorocyclohexane | Heptachlor | Mirex | Nitro Musks | Toxaphene | Dioxins and Furans | PBDEs | PCBs | Solvents | Lead, Mercury, Cadmium and Other Metals
11. Longnecker, M.P., W.J. Rogan, and G. Lucier, "The Human Health Effects of DDT (Dichlorodiphenyltrichloroethane) and PCBs (Polychlorinated Biphenyls) and an Overview of Organochlorines in Public Health," Annual Reviews of Public Health, 18 (1997): p. 211-44.
16. Jensen, A.A. and S.A. Slorach, Chemical Contaminants in Human Milk, Boca Raton Ann Arbor Boston: CRC Press, Inc. (1991);Somogyi, A. "Nuturing and Breast-Feeding: Exposure to Chemicals in Breast Milk," Environmental Health Perspectives, 101(Suppl 2) (1993):p. 45-52; Mes, J., et al. "Levels and Trends of Chlorinated Hydrocarbon Contaminants in the Breast Milk of Canadian Women," Journal of Food Additives and Contaminants, 3(4) (1986): p. 313-22; Furst, P., C. Furst, and K. Wilmers, "Human Milk as a Bioindicator for Body Burden of PCDDs, PCDFs, Organochlorine Pesticides, and PCBs," Environmental Health Perspectives Journal, 102 (1994): p. 187-93; Schecter, A.J., et al. "Levels of Polychlorinated Dibenzofurans, Dibenzodioxins, PCBs, DDT and DDE, Hexachlorobenzene, Dieldrin, Hexachlorocyclohexane and Oxychlordane in Humam Breast Milk from the United States, Thailand, Vietnam, and Germany," Chemosphere, (1989): 18: p. 445-54; Schade, G. and B. Heinzow, "Organochlorine Pesticides and Polychlorinated Biphenyls in Human Milk of Mothers Living in Northern Germany: Current Extent of Contamination, Time Trend from 1986 to 1997 and Factors that Influence the Levels of Contamination," The Science of the Total Environment, 215 (1998): p. 31-39.
18. It is important to note that the data for Tanzania and Zimbabwe were published in 1992 and 1991, respectively, which is earlier than most of the other nations by several years. Thus, DDT levels shown may be somewhat upwardly biased. However, DDT is still used in both nations, so the higher DDT/DDE ratios shown in comparison to other nations are most likely an accurate trend.
19. Jaga, K. and C. Dharmani, G"lobal Surveillance of DDT and DDE Levels in Human Tissues," International Journal of Occupational Medicine and Environmental Health,2003; vol. 16, no. 1, p. 7-20; Wong, C.K., K.M. Leung, B.H. Poon, C.Y. Lan, M.H. Wong, "Organochlorine Hydrocarbons in Human Breast Milk Collected in Hong Kong and Guangzhou," Archives of Environmental Contamination and Toxicology, vol. 43, no. 3 (2002): p. 364-372.
20. Jaga, K. et al. "Global Surveillance of DDT and DDE Levels in Human Tissues," International Journal of Occupational Medicine and Environmental Health, 16, no. 1 (2003): p. 7-20; Wong, C.K., et al., Organochlorine Hydrocarbons in Human Breast Milk Collected in Hong Kong and Guangzhou, Archives of Environmental Contamination and Toxicology vol. 43, no. 3, (2002): p. 364-372; Romero, M.L., J.G. Dorea, A.C. Granja. "Concentrations of Organochlorine Pesticides in Milk of Nicaraguan Mothers," Archives of Environmental Health vol. 55, no. 4 (July/August 2000): p. 274.
21. 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): p. 1807-1816.
22. Savage, E.P., T.J. Keefe, and J.D. Tessari, "Pesticides in Human Breast Milk, in Environmental Factors in Human Growth and Development," Banbury Report No. 11, V.R. Hunt, M.K. Smith, and D. Worth, Editors, Cold Spring Harbor Laboratory (1982): p. 77-84.
23. Sant'Ana, L.S., I. Vassilieff, and L. Jokl, "Levels of Organochlorine Insecticides in Milk of Mothers from Urban and Rural Areas of Botucatu," SP, Brazil, Bulletin of Environmental Contamination and Toxicology 42 (1989): p. 911-18.
27. Albert, L., P. Vega, and A. Portales, "Organochlorine Pesticide Residues in Human Milk Samples from Comarca Lagunera, Mexico," 1976, Pesticides Monitoring Journal 15 (1981): p. 135-38.; Gladen, B.C. and W.J. Rogan, "DDE and Shortened Lactation in a Northern Mexican Town," American Journal of Public Health 85 (1995): p. 504-8; Waliszewski, S.M., et al. "Organochlorine Pesticide Residues in Human Breast Milk from Tropical Areas in Mexico," Bulletin of Environmental Contamination and Toxicology 57 (1996): p. 22-28.; Lopez-Carrillo, L., et al. "Is DDT Use a Public Health Problem in Mexico?" [see comments], Environmental Health Perspectives Journal 104(6) (1996): p. 584-8.
Cites for International Studies Used in Comparison Chart
Australia - Quinsey, P.M., D.C. Donohue, J.T. Ahokas, "Persistence of Organochlorines in Breast Milk of Women in Victoria, Australia," Journal of Food and Chemical Toxicology vol. 33, no. 1 (1995): p. 49-56. Brazil - Paumgartten, F.J., 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): p. 293-297.
Canada - 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): p. 519-526. China - Wong, C.K., K.M. Leung, B.H. Poon, C,Y. Lan, M.H. Wong, "Organochlorine Hydrocarbons in Human Breast Milk Collected in Hong Kong and Guangzhou," Archives of Environmental Contamination and Toxicology vol. 43, no. 3 (2002): p. 364-372.
Czech Republic - Cajka. T., J. Hajslova, "Polychlorinated Biphenyls and Organochlorine Pesticides in Human Milk from the Locality Prague, Czech Republic: A Comparative Study," Bulletin of Environmental Contamination and Toxicology vol. 70, no. 5 (2003): p. 913-919.
Egypt - Saleh, M., A. Kamel, A. Ragab, G. El-Baroty, A.K. El-Sebae, "Regional Distribution of Organochlorine Insecticide Residues in Human Milk from Egypt," Journal of Environmental Science and Health March vol. 31, no. 2 (1996): p. 241-255.
Finland - Smeds, A. and P. Saukko, "Identification and Quantification of Polychlorinated Biphenyls and Some Endocrine Disrupting Pesticides in Human Adipose Tissue from Finland," Chemosphere vol. 44, no. 6 (2001): p. 1463-1471.
Germany - Furst, P., C. Furst, K. Wilmers, "Human Milk as a Bioindicator for Body Burden of PCDDs, PCDFs, Organochlorine Pesticides, and PCBs," Environmental Health Perspectives vol. 102, Supp. 1 (Jan 1994): p. 187-193.
Greece - Schinas, V., M. Leotsinidis, A. Alexopoulos, V. Tsapanos, X.G. Kondakis, "Organochlorine Pesticide Residue in Human Milk from Southwest Greece: Associations with Weekly Food Consumption Patterns of Mothers," Archives of Environmental Health vol. 55, no. 6 (2000): p. 411-417.
Greenland - Dewailley, E., G. Mulvad, H.S. Pedersen, P. Ayotte, A. Demers, J.P. Weber, J.C. Hansen, "Concentration of Organochlorines in Human Brain, Liver, and Adipose Tissue Autopsy Samples from Greenland," Environmental Health Perspectives vol. 107, no. 3 (1999): p. 823-828. Iran - Cok, I., A.E. Karakaya, B.L. Afkham, S. Burgaz, "Organochlorine Pesticide Contaminants in Human Milk Samples Collected in Tebriz (Iran)," Bulletin of Environmental Contamination and Toxicology vol. 63, no. 4 (1999): p 444-450.
Japan - Konishi, Y., K. Kuwabara, S. Hori, "Continuous Surveillance of Organochlorine Compounds in Human Breast Milk from 1972 to 1998 in Osaka, Japan," Archives of Environmental Contamination and Toxicology vol. 40, no. 4 (2001): p. 571-578.
Jordan - Alawi, M.A., S. Tamimi, M. Jaghabir, "Storage of Organochlorine Pesticides in Human Adipose Tissues of Jordanian Males and Females," Chemosphere May vol. 38, no. 12 (1999): p. 2865-2873. Kazakhstan - Hooper, K. , K. Hopper, M.X. Petreas, J. She, P. Visita, J. Winkler, M. McKinney, M. Mok, F. Sy, J. Garcha, M. Gill, R.D.Stephens, G. Semenova, T. Sharmanov, T. Chuvakova, "Analysis of Breast Milk to Assess Exposure to Chlorinated Contaminants in Kazakhstan: PCBs and Organochlorine Pesticides in Southern Kazakhstan," Environmental Health Perspectives vol. 105, no. 11 (1997): p. 1250-1254.
Kuwait - Saeed, T., W.N. Sawaya, N. Ahmad, S. Rajagopal, B. Dashti B, S. al-Awadhi, "Assessment of the Levels of Chlorinated Pesticides in Breast Milk in Kuwait," Journal of Food Additives and Contaminants vol. 17, no. 12 (2000): p. 1013-1018.
Mexico - Waliszewski, S.M., A.A. Aguirre, R.M. Infanzon, A. Benitez, J. Rivera, "Comparison of Organochlorine Pesticide Levels in Adipose Tissue and Human Milk of Mothers Living in Veracruz, Mexico," Bulletin of Environmental Contaminants and Toxicology vol. 62, no. 6 (2000): p. 685-690. Nicaragua - Romero, M.L., J.G. Dorea, A.C. Granja, "Concentrations of Organochlorine Pesticides in Milk of Nicaraguan Mothers," Archives of Environmental Contamination and Toxicology vol. 55, no. 4 (July/August 2000): p. 274.
Poland - Ludwicki, J.K. and K. Goralczyk, "Organochlorine Pesticides and PCBs in Human Adipose Tissues in Poland," Bulletin of Environmental Contamination and Toxicology vol. 52, no. 3 (1994): p. 400-403. Russia - Polder, A., J.O. Odland, A. Tkachev, S. Foreid, T.N. Savinova, J.U. Skaare, "Geographic Variation of Chlorinated Pesticides, Toxaphenes, and PCBs in Human Milk from Sub-Arctic and Arctic Locations in Russia," The Science of the Total Environment vol. 306, no. 1-3 (2003): p. 179-195. Saudi Arabia - Schinas, V., et al. "Organochlorine Pesticide Residue in Human Milk from Southwest Greece: Associations with Weekly Food Consumption Patterns of Mothers," Archives of Environmental Health vol. 55, no. 6, (2000): p. 411-417.
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): p. 1111-1123. Tanzania - van der Ven, K., H. van der Ven, A. Thibold, O. Bauer, M. Kaisi, J. Mbura, H.N. Mgaya, N. Weber, K. Diedrich, D. Krebs, "Chlorinated Hydrocarbon Content of Fetal and Maternal Body Tissues and Fluids in Full Term Pregnant Women: A Comparison of Germany vs. Tanzania," Human Reproduction vol. 7, supp. 1 (1992): p. 95-100. Turkey - Schinas, V., et al., "Organochlorine Pesticide Residue in Human Milk from Southwest Greece: Associations with Weekly Food Consumption Patterns of Mothers," Archives of Environmental Health vol. 55, (2000): p. 411-417.
Ukraine - Gladen. B.C., A. J. Schecter, O. Papke, Z.A. Shkyryak-Nyzhnyk, D.O. Hryhorczuk, R.E. Little, "Organochlorines in Breast Milk from Two Cities in Ukraine," Environmental Health Perspectives vol. 107, no. 6 (June 1999): p. 459-462.
United Kingdom - Harris, C.K., S. O'Hagan, G.H. Merson, "Organochlorine Pesticide Residues in Human Milk in the United Kingdom 1997-8," Human and Experimental Toxicology vol. 18, no. 10 (1999): p. 602-606. United States - Stellman, S.D., M.V. Djordjevic, J.A. Britton, J.E. Muscat, M.L. Citron, M. Kemeny, E. Busch, L. Gong, "Breast Cancer in Relation to Adipose Concentration of Organochlorine Pesticides and Polychlorinated Biphenyls in Long Island, New York," Cancer Epidemiol Biomark Prev, vol. 9, no. 11, (2000): p. 1241-1249.
Uzbekistan - Ataniyazova, O.A., R.A. Baumann, A.K. Liem, U.A. Mukhopadhyay, E.F. Vogelaar, E.R. Boersma, "Levels of Certain Metals, Organochlorine Pesticides and Dioxins in Cord Blood, Maternal Blood, Human Milk, and Some Commonly Used Nutrients in the Surroundings of the Aral Sea, (Karakalpakstan, Republic of Uzbekistan)," Acta Paediatrica vol. 90, no. 7 (2000): p. 801-808.
Zimbabwe - Chikuni , O., J.U. Skare, N. Nyazema, A. Polder, "Residues of Organochlorine Pesticides in Human Milk from Mothers Living in the Greater Harare Area of Zimbabwe," Central African Journal of Medicine vol. 37, no. 5, (1991): p. 136-141.
last revised 3.25.05