levels in the pool consisting of mothers with a long duration of stay in other overseas coun- tries, including Indonesia, Singapore, Vietnam, and Thailand. Such geographic speciﬁcity in congener proﬁles can be more clearly demon- strated by the variation in proportion of PCBs in total TEQs among the countries in the 2002–2003 WHO study (Australia, 34%; Fiji, 34%; Germany, 52%; New Zealand, 36%; Norway, 53%; the Philippines, 38%; Russia, 39%; Sweden, 50%; the United States, 39%) (Malisch and van Leeuwen 2003). Given that > 90% of the dioxin body load is from food, the intercountry differences in food sources and dietary habits might explain most of the observed difference in dioxin profiles in the milk samples of mothers who live in Hong Kong, mainland China, and overseas countries. Dioxin emission in mainland China and Hong Kong. The exposure of the fetus and breast-fed infants to the current background levels of dioxins and dioxin-like compounds may pose health hazards, including reproduc- tive (Egeland et al. 1994; Mocarelli et al. 2000), neurodevelopmental (Jacobson et al. 1990; Patandin et al. 1999; Winneke et al. 1998), and endocrine-related hazards (Nagayama et al. 1998). Continued and enhanced efforts should be directed toward identiﬁcation and elimina- tion of dioxin sources in mainland China. Our survey, as part of the 2002–2003 WHO-coor- dinated exposure study, showed that median levels of dioxins and dioxin-like PCBs in breast milk, from mothers originating around the Pearl River Delta region and other parts of mainland China, were lower than at least half of the other 25 regions participating. However, the public health threat of dioxin contamina- tion in this region remains a concern. The dioxin inventory in mainland China for 2002, the ﬁrst so far, estimated PCDD/PCDF emis- sions to the atmosphere to be 7,144–13,575 g International (I)-TEQ/year (Jun et al. 2004). The China inventory does not include uncon- trolled backyard burning of waste. In Hong Kong, the annual emission was estimated to be 23–33 I-TEQ/year (HKEPD 2000). One main reason for the high dioxin emission in mainland China is the heavy municipal waste manage- ment burden, together with its expanding popu- lation. Most of the municipal waste incinerators in mainland China did not comply with the PCDD/PCDF national emission standard of 1.0 ng I-TEQ/m3, which is less stringent than 0.1 ng I-TEQ/m3 used in developed countries (Jun et al. 2004). The growth of the economy was associated with the development of indus- tries causing dioxin emissions, such as crude steel and chloralkali industries. Active dioxin abatement policies and measures are needed to enforce a more stringent PCDD/PCDF emis- sion standard for incineration, control illegal smuggling of electronics waste (Basel Action Network 2004; Schmidt 2002) for recycling activities (Puckett et al. 2002), and prohibit uncontrolled waste burning and ensure correct disposal of equipment and material containing PCBs. Hong Kong has a land mass of about 1,100 km2 and 6.8 million inhabitants, and most solid waste is disposed of in landfills. Alternative methods of waste management are now being considered, including thermal waste treatment that was abandoned several years ago, because the landﬁlls are almost certain to reach full capacity within the next decade. From a public health perspective, waste man- agement policy in Hong Kong should be based on an assessment of its impact on the envi- ronment and human health. Although a rela- tively low annual PCDD/PCDF emission was estimated in Hong Kong, because of its prox- imity to mainland China that provides most imported food, dioxin exposure in Hong Kong could be inﬂuenced by the mainland environ- ment. Monitoring of dioxin content of food and breast milk in the region would allow intercountry comparisons of exposure, help to identify trends and point sources, and prevent accidental exposure. Safety of breast-feeding in Hong Kong and China. On the basis of a review of the litera- ture and the WHO recommendations, exclu- sive breast-feeding should continue to be strongly supported and promoted. This rec- ommendation takes into consideration the fact that the negative effects of dioxins on child health have been shown to be the result of transplacental rather than lactational transfer of dioxins. Breast-feeding protects infants, including those exposed to transplacental dioxins. The results of the present study, as part of the 2002–2003 WHO exposure study, provide further support for the WHO recom- mendation because dioxin levels have fallen in other regions over the past 20 years, and Hong Kong’s levels are in the lower to middle range of the countries/regions surveyed. Limitations. We attempted to collect hind milk in a uniform manner and reduce within- pool variation in fat contribution by advising mothers to feed their babies 2 hr before milk collection. Our estimates of dioxin assumed an even contribution of fat from each mother in the same pool. However, the fat content of individual samples varied and is a potential source of error in the analysis procedure. Dietary information from the mothers, estimated by our semiquantitative food fre- quency questionnaire, may deviate from actual intakes because of unreliable reporting of either frequencies or amounts consumed. Estimation of dioxin intakes from consumption of other food items such as cereal, vegetables, and fruits not included in the questionnaire could be a source of confounding in the relationship between dioxin load and recorded dietary habits. Environmental Health Perspectives • VOLUME 114 | NUMBER 2 | February 2006 Human dioxin levels in Hong Kong Inclusion of partially breast-feeding moth- ers in this present study might have led to over- estimation of the dioxin levels compared with the countries that were able to strictly follow the protocol of the WHO exposure study. However, analysis of the TEQ value of individ- ual milk samples in our study by the chemically activated luciferase expression (CALUX) bioas- say (Aarts et al. 1996) found that breast-feeding exclusivity was not signiﬁcantly associated with our observed dioxin levels (data not shown). 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