Research Breast Milk Dioxins in Hong Kong and Pearl River Delta Anthony J. Hedley,1 Tze Wai Wong,2 Lai Ling Hui,1 Rainer Malisch,3 and Edmund A.S. Nelson 4 1Department of Community Medicine, University of Hong Kong, Hong Kong, People’s Republic of China; 2Department of Community and Family Medicine, Chinese University of Hong Kong, Hong Kong, People’s Republic of China; 3State Institute for Chemical and Veterinary Analysis of Food, Freiburg, Germany; 4Department of Paediatrics, Chinese University of Hong Kong, Hong Kong, People’s Republic of China There are no previous reports from South China on chemically determined polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like poly- chlorinated biphenyls (PCBs) in human breast milk expressed as World Health Organization (WHO) toxic equivalents (TEQs). In a 2002–2003 WHO exposure study, 13 pools of breast milk comprising samples from 316 primiparous women in Hong Kong in 2002 were analyzed by gas chromatography/mass spectrometry for 29 PCDD/F and dioxin-like PCB congeners. Total WHO-TEQs ranged from 8.97 to 16.7 pg/g fat (weighted mean, 12.9 pg; weighted median, 13.4 pg). Variations in TEQs included positive associations with age (R 2 = 0.73, p < 0.0005), higher consumption of dairy products and seafood, and lower TEQs in overseas mothers and ever- smokers. Congener proﬁles indicated geographic speciﬁcity of exposure in Hong Kong, mainland China, and overseas Asian countries, including higher proportions of PCB-TEQs (overseas) and PCDF-TEQs (mainland China). The median TEQs of PCDD/Fs (8.69 pg/g fat) and PCBs (4.73 pg/g fat) in Hong Kong were highest among the ﬁve Asian Paciﬁc countries but lower than the levels for at least half of the European countries that participated in the WHO study. However, future international studies should incorporate mother’s age in the design of the pooling strategy to allow standardization by other exposure factors and valid comparisons among different countries. The findings allow support for the WHO breast-feeding advisory. Trends in human dioxin levels in the region cannot yet be determined, and rigorous controls are needed to reduce emissions of dioxins and human exposure in mainland China. Key words: breast milk, China, dioxin-like polychlorinated biphenyls, Hong Kong, polychlorinated dibenzofurans, polychlori- nated dibenzo-para-dioxins. Environ Health Perspect 114:202–208 (2006). doi:10.1289/ehp.8116 available via http://dx.doi.org/ [Online 13 October 2005] Polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (PCBs) are a group of structurally related chemicals that persist in the environment and may bio- accumulate in animal sources of food and in human tissues. These compounds have been shown to exert a number of toxic responses, including dermal toxicity, neurodevelopmental deﬁcits, immunotoxicity, reproductive effects and teratogenicity, endocrine disruption, and carcinogenicity. As a simpliﬁcation, in this arti- cle the word “dioxin” refers to dioxins and furans. The first measurements of a congener of dioxins, 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD), in biologic tissues came from Asia, based on human milk and fish samples collected in Vietnam in the early 1970s (Baughman and Meselson 1973). In the 1980s, it was recognized that because of their widespread occurrence and the low degradation rate, most people in the world could have measurable levels of these com- pounds in their bodies (Graham et al. 1985). In 1997, the International Agency For Research on Cancer classified TCDD as a group I carcinogen (IARC 1997), and a recent review of both existing and new evi- dence supports this previous controversial decision (Steenland et al. 2004). In 2001, the 202 Joint Food and Agriculture Organisation (FAO)/World Health Organization (WHO) Expert Committee on Food Additives reeval- uated international tolerable intake of diox- ins, furans, and coplanar PCBs and developed a provisional value of 70 pg WHO-toxic equivalents (TEQ)/kg body weight per month (WHO 2002). In the 1990s, Hong Kong closed down four municipal solid waste incinerators that were the dominant source of dioxins in the region, but some incineration facilities (e.g., clinical waste incinerators, crematoria, and a high-temperature incinerator at a chemical waste treatment center) are still in use. The government has invited proposals on the adoption of modern incinerators for munici- pal solid waste treatment, in anticipation of a shortage of waste disposal capacity in Hong Kong. The concentrations of dioxins and related compounds in humans could reﬂect the level of contamination in the environment, so trends estimated from cross-sectional sets of data can guide the development of environ- mental policy on the control of their produc- tion and emissions. The WHO Regional Ofﬁce for Europe (WHO/EURO) initiated a series of international studies on the concen- trations of PCDDs, PCDFs, and PCBs in human breast milk of primiparous women. In comparison with the data collected in 1987–1988 (Yrjanheikki 1989), the levels of PCDDs and PCDFs in breast milk in 1992–1993 (WHO 1996) had decreased by up to 50% in some countries. The decrease was attributed to the legislation aimed at reducing the release of these compounds into the environment in Europe. Internationally comparable data on levels and trends in dioxins are lacking in Hong Kong and South China. There are three pub- lished studies on organochlorine compounds in human milk in Hong Kong (Ip 1983; Ip and Phillips 1989; Wong et al. 2002). None of them determined the toxicity of dioxins and dioxin-like PCBs in terms of WHO- TEQs. The level of dioxin-like compounds in breast milk samples was not determined in Hong Kong by biodetection methods until 1998 (Lai et al. 2004; Soechitram et al. 2003). However, chemically determined levels of either PCDDs or PCDFs and WHO-TEQs in local breast milk samples have not been previously reported. To support and strengthen national strate- gies for both the monitoring and management of dioxins and dioxin-like PCBs, the third round of the WHO-coordinated exposure study was initiated in March 2000. Twenty-six countries/regions [Australia, Belgium, Brazil, Bulgaria, Croatia, Czech Republic, Egypt, Fiji, Finland, Germany, Hong Kong Special Administrative Region (Hong Kong SAR), Hungary, Ireland, Italy, Luxembourg, New Zealand, Norway, the Philippines, Romania, Russia, Slovak Republic, Spain, Sweden, the Netherlands, Ukraine, and the United States] Address correspondence to E.A.S. Nelson, Department of Paediatrics, Chinese University of Hong Kong, 6/F Clinical Science Building, Prince of Wales Hospital, Shatin, Hong Kong. Telephone: 852-26322861. Fax: 852-26360020. E-mail: tony-nelson@cuhk.edu.hk We thank all the mothers who collaborated with the study and donated milk samples. We also thank A. Chiu, S. Leung, and all the nursing staff in Maternity and Child Health Centers for their help in recruitment of the mothers and sample collection. We also thank D. Wong and H. Choi for milk and data collection and C.M. Wong and T.Q. Thach for statistical advice. We thank S.T. Kwok for technical help in the laboratory and M. Chi for secretarial help. This work was supported by the Hong Kong Environment Conservation Fund (grant 8/2000). The authors declare they have no competing ﬁnancial interests. Received 15 March 2005; accepted 12 October 2005. VOLUME 114 | NUMBER 2 | February 2006 • Environmental Health Perspectives