Healthy Milk, Healthy Baby
Chemical Pollution and Mother's Milk
BACK TO CHEMICAL OVERVIEW
Hexachlorocyclohexane (HCH) is a commercial insecticide. It is persistent in the environment, and has been noted in breast milk monitoring studies, but it is not one of the chemicals currently included in the International POPs Elimination Treaty. That is a mistake, in the view of environmentalists and health experts.
HCH is made up of a mixture of eight isomers. Isomers are related but different forms of a chemical. A sample of HCH is usually a mixture of at least four different HCH isomers including the alpha, beta, delta and gamma forms.1 The chart below illustrates what a normal HCH mixture would look like. The composition of HCH is important because different isomer forms have different levels of persistence and bioaccumulate in breast milk differently.
The gamma-isomer of HCH, also known as lindane, is used as an insecticide that is directly applied to the body and scalp to treat head and body lice and scabies.
The beta-isomer of HCH is the most persistent and bioaccumulative form. The alpha- and gamma-isomers of HCH are converted into the beta-isomer in living organisms. As a result of this conversion, as much as 90 percent of HCH detected in human tissues and breast milk is the beta-HCH.2
HCH in the Body
The different chemical forms of HCH can move through air once they are released into the environment. The alpha-, beta-, gamma- and delta-isomers can all be present as a vapor or can attach to such small airborne particles as soil and dust. Lindane (the gamma-isomer) can remain in the air for up to 17 weeks, and can travel long distances. Airborne particles with attached HCH may be removed from the air by rain.3
As with many other POPs, HCH attaches to soil and sediment particles. However, fungi and bacteria can break HCH down into less harmful substances. HCH isomers, including lindane, are broken down quickly in water. All HCH isomers can accumulate in the fatty tissue of fish and other animals.
Humans may be exposed to HCH isomers in different ways, including4:
- Eating contaminated foods, including plants grown in HCH-contaminated soils and meat and dairy products from contaminated animals
- Through the skin, when lindane is applied as a lotion or shampoo to control head lice and scabies
- Drinking contaminated water or breathing contaminated air near waste sites, landfills or sites where HCH is produced or used
Controlling Exposure: Bans and Restrictions
As of 2003, HCH had been banned or restricted in 35 countries and had been made illegal for import in 98 countries. Lindane had been specifically banned or restricted in 40 countries, and made illegal for import in 65 countries, but it is often permitted for special uses by exemption.5 For instance, in the United States, mixed HCH has been banned as an insecticide, but lindane may still be used, either as a pesticide or as a pharmaceutical for topical application against head lice and scabies.
Along with other commonly banned pesticides, surplus stockpiles of technical grade HCH and lindane are often exported to developing countries. In Africa and Asia, large quantities of obsolete HCH have been sent to remote locations where their use and storage have endangered drinking water, food sources and humans.6
Assessing the Extent of Exposure: Bans and Restrictions
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. But different agencies may have markedly different levels they consider "safe." These differences usually reflect the agencies' varying perspectives, as well as the kind of data they reviewed in setting levels. In the case of HCH, a number of agencies have established benchmarks, but conclusive evidence demonstrating that any one of these benchmarks is protective or superior to the others does not exist.
For direct human intake of beta-HCH, the Canadian Health Protection Branch has set a tolerable daily intake level (TDI) of 0.3 micrograms per kilogram per day (µg/kg/day).7 The World Health Organization (WHO) has set an acceptable daily intake level (ADI) for lindane of 8 µg/kg.8 The U.S. EPA has set a maximum contaminant level (MCL) of 0.2 parts per billion (ppb) in drinking water.
Breast Milk Monitoring Studies Measuring HCH
Studies looking at HCH contamination of breast milk have been conducted around the world, including reported results in the following countries:
|Czech Republic||Israel||Russia||United Kingdom|
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 HCH residues in breast milk, since this list reflects only those areas where studies have been conducted.
Limitations of Studies Measuring HCH in Breast Milk
It is often difficult to draw conclusions about national and international trends in HCH contamination because of the numerous factors affecting levels and limitations in the way the data is 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.
- Different measurement methodologies. Because HCH contamination can occur in several different isomeric forms, it can be reported either as individual isomer concentrations or as a sum value of total HCH presence. In cases where different individual isomer concentrations are reported, it may be difficult to compare across studies. This is especially relevant since different isomeric forms of HCH have different levels of persistence. Without a measurement of beta-HCH, it may be difficult to assess the full extent of contamination.
- Few studies. Many countries have not conducted multiple studies over a range of time. Instead, the information on HCH residues may just be a snapshot of a particular time. It is difficult, therefore, to draw conclusions about trends or to assess the effects of bans and restrictions.
- Small study populations. Because of the cost and time involved, many studies measuring HCH residue levels in breast milk test only a few people. In instances where the only data on a country's HCH exposure come from studies with small sample sizes, it is difficult to draw reliable conclusions about the entire population's exposure.
- 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 driving average values from the study higher.
Some Important Examples of HCH in Breast Milk
Several useful studies on HCH are available.
Technical grade hexachlorocyclohexane and its isomers have been found in breast milk throughout the world. That said, HCH levels vary widely across the globe, with the highest values found in areas of extensive use.9
Several additional factors may affect the levels of HCH found in breast milk. Like DDT, HCH breaks down more quickly in tropical climate zones than in temperate zones.10 Thus, levels of HCH in the environment, and perhaps in breast milk, are likely to be relatively lower in warm climates if all other factors are equal. Also, as with other persistent organic compounds that bioaccumulate through the food chain, the concentration of HCH in breast milk is strongly related to diet. A German study found that women who followed a low-fat diet had lower beta-HCH levels in their breast milk than women whose diet included large quantities of meat.11
The examples of HCH breast milk studies presented here are divided into three types:
- Time trend examples -- studies that have looked at average levels of HCH 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 and exposure patterns
Especially high levels of HCH in breast milk have been associated with areas of high use. In China and Japan, HCH was commonly used as an insecticide in rice fields, and levels as high as 6,500 ppb of HCH in milk fat have been measured in these countries.12 Since Japan banned HCH in the 1970s, however, levels of the pesticide in breast milk have decreased. Figure 2 shows data measuring average levels of HCH in breast milk in Osaka, Japan, between 1972 and 1998.13 Over the course of the decade studied, levels dropped significantly.
Studies conducted in Hong Kong, China have also shown dramatic decreases in beta-HCH levels in the 15-year period between 1985 and 2000. Beta-HCH levels in breast milk dropped by 94 percent during this period, most likely in response to China's restriction and subsequent ban of all HCH production and use in the early 1990s. Figure 3 shows this decline.14
In general, countries that have monitored breast milk for HCH residues over time have witnessed a steady decrease. Figure 4 demonstrates a clear downward trend in residues in the North Rhine Westphalia region of Germany.15 Figure 5 illustrates a similar downward trend of average lindane levels in Stockholm, Sweden, while Figure 6 shows the same trend for levels of beta-HCH found in Swedish breast milk.16
Figure 7 shows high international variability in beta-HCH levels in breast milk measured in 17 countries during the 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.
Beta-HCH levels measured in India were nearly two orders of magnitude higher than in many of the other nations listed in Figure 7. The study reporting this data was conducted in Delhi, but similarly high beta-HCH levels have been detected elsewhere in India as well.17 Though gamma-HCH (lindane) has been banned for indoor use in India, it is still permitted to be used on field crops for pest control. That is the likely cause of the high levels reported.18
Elevated HCH levels in breast milk in other countries shown in Figure 7 may be a result of the fact that many nations have taken action to ban and restrict HCH very recently, while some nations still allow restricted use of lindane for agricultural pest control or head-lice control. HCH was banned for production and all use in China in 1993,19 and was banned for import in Kazakhstan in 1996, but it has not yet been banned for production or use in Kazakhstan.20 Iran has banned HCH use, production and import,21 but the 1999 national study this data was taken from states that the probable reason for elevated HCH levels in Iran is the continued use of lindane for pest control instead of DDT, so it is likely that the phaseout is not complete.22 Past uses of organochlorine pesticides in the Ukraine are reported to have been high, which may account for the elevated HCH levels shown for the Ukraine in Figure 7, but the status of HCH registration and use in the Ukraine was not available as of 2004.23
National Variations In HCH Levels
Figure 8 shows an example of the kinds of regional variation in contaminant levels within nations that averages can mask. Wetlands surrounding the city of Veracruz, Mexico, have long been treated with such pesticides as DDT and HCH to control the spread of malaria. This difference in local use patterns can clearly be seen in this comparison of 1994-1995 beta-HCH contamination levels in suburban and urban areas of Veracruz. Beta-HCH levels were more than 50 percent higher in the suburban areas.24
Very high levels of HCH have also been found in parts of the former Soviet Union. In the Kola Peninsula, levels were found to be 20 times higher than those in neighboring Norway.25 It is thought that these increased levels may be diet-related because high rates of fish consumption in the circumpolar region have been linked to high levels of other organochlorine compounds.
A 1982 study in Norway, a decade after HCH was banned in that country, found higher levels of the beta-isomer of HCH in women who had immigrated from developing countries. Immigrant women had an average level of 433 ppb beta-HCH in their milk fat, while native Norwegian women had an average of 80 ppb in theirs. The difference was attributed to the likelihood of higher exposures in developing countries.26
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11. 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): pp. 31-39.
13. 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): pp. 571-578.
14. Wong C.K., K.M. Leung, B.H. Poon, C.Y. Lan, and 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): pp. 364-372; Ip H.M, D.J. Phillips, "Organochlorine Chemicals in Human Breast Milk in Hong Kong," Archives of Environmental Contamination and Toxicology, vol. 18: no. 4 (1989) pp. 490-494; Pesticide Action Network Pesticide Registration Database, China, HCH, www.pesticideinfo.org/Detail_Country.jsp?Country=China.
17. Banerjee, B.D., S.S. Zaidi, S.T. Pasha, D.S. Rawat, B.C. Koner, Q.Z. Hussain, "Levels of HCH Residues in Human Milk Samples from Delhi, India," Bulletin of Environmental Contamination and Toxicology 59: no. 3 (1997): pp. 403-406; Sanghi, R., M.K. Pillai, T.R. Jayalekshmi, A. Nair, "Organochlorine and Organophosphorous Pesticide Residues in Breast Milk from Bhopal, Madhya Pradesh, India" Human and Experimental Toxicology 22: no. 2 (2003): pp. 73-76.
22. 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): pp. 444-450.
23. Gladen B.C., S.C. Monaghan, E.M. Lukyanova, O.P. Hulchiy, "Organochlorines in Breast Milk from Two Cities in Ukraine," Environmental Health Perspectives vol. 107no. 6 (1999): pp. 459-462; United Nations Rotterdam Convention Prior Informed Consent (PIC) Database of International Pesticide Registration Status, www.fao.org/pic/Country.htm (August 11, 2003).
24. Waliszewski S.M., V.T. Pardio Sedas, J.N. Chantiri, R.M. Infanzon, J. Rivera, Organochlorine Pesticide Residues in, Bulletin of Environmental Contamination and Toxicology 1996;vol. 57, no.1, p. 22-28.
26. Skaare, J.U., J.M. Tuveng, and H.A. Sande, "Organochlorine Pesticides and Polychlorinated Biphenyls in Maternal Adipose Tissue, Blood, Milk, and Cord Blood from Mothers and Their Infants Living in Norway," Archives of Environmental Contamination and Toxicology 17 (1988): pp. 55-63.
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): pp 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): pp. 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): pp. 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): pp. 364-372.
Czech Republic - Cajka, T. and 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): pp. 913-919.
Germany - 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 vol. 215, no. 1-2 (1998): pp. 31-39.
India - Banerjee, B.D., S.S. Zaidi, S.T. Pasha, D.S. Rawat, B.C. Koner, Q.Z. Hussain, "Levels of HCH Residues in Human Milk Samples from Delhi, India," Bulletin of Environmental Contamination and Toxicology , vol. 59, no. 3 (1997): pp. 403-406.
Indonesia - Burke, E.R., A.J. Holden, I.C. Shaw, A Method to Determine Residue Levels of Persistent Organochlorine Pesticides in Human Milk from Indonesian Women, Chemosphere,2003; vol. 50, no. 4, p. 529-535.
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): pp. 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): pp. 571-578.
Kazakhstan - Lutter, C., V. Iyengar, R. Barnes, T. Chuvakova, G. Kazbekova, T. Sharmanov, Breast Milk Contamination in Kazakhstan: Implications for Infant Feeding, Chemosphere,1998; vol. 37, no. 9-12, p. 1761-1772.
Kenya - Kinyamu, J.K., L.W. Kanja, J.U. Skaare, T.E. Maitho, "Levels of Organochlorine Pesticides in Residues in Milk of Urban Mothers in Kenya, " Bulletin of Environmental Contamination and Toxicology vol. 60, no. 5 (1998): pp. 732-738.
Mexico - Waliszewski, S.M., A.A. Aguirre, R.M. Infanzon, C.S. Silva, J. Siliceo, "Organochlorine Pesticide Levels in Maternal Adipose Tissue, Maternal Blood Serum, Umbilical Cord Serum, and Milk from Inhabitants of Veracruz, Mexico," Archives of Environmental Contamination and Toxicology vol. 40, no. 3 (2001): pp. 432-438.
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): pp. 274.
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): pp. 179-195.
Ukraine - Gladen, B.C., S.C. Monaghan, E.M. Lukyanova, O.P. Hulchiy, Z. A. Shkyryak-Nyzhnyk, J.L. Sericano, R.E. Little. "Organochlorines in Breast Milk from Two Cities in Ukraine," Environmental Health Perspectives , vol. 107, no. 6 (June 1999): pp. 459-462.
United Kingdom - Harris, C.A., 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): pp. 602-606.
last revised 3.25.05