Detection of dicofol and related pesticides in human breast milk from China, Korea and Japan

Previously, we demonstrated that the concentrations of DDTs were greater in breast milk collected from Chinese mothers than from Japanese and Korean mothers. To investigate dicofol as a possible source of the DDTs in human breast milk, we collected breast milk samples from 2007 to 2009 in China (Beijing), Korea (Seoul, Busan) and Japan (Sendai, Takarazuka and Takayama). Using these breast milk samples, we quantified the concentrations of dichlorobenzophenone, a pyrolysis product of dicofol (simply referred to as dicofol hereafter), dichlorodiphenyltrichloroethane and its metabolites (DDTs) using GC-MS. Overall, 12 of 14 pooled breast milk samples from 210 mothers contained detectable levels of dicofol (>0.1 ng g⁻¹ lipid). The geometric mean concentration of dicofol in the Japanese breast milk samples was 0.3 ng g⁻¹ lipid and significantly lower than that in Chinese (9.6 ng g⁻¹ lipid) or Korean breast milk samples (1.9 ng g⁻¹ lipid) (p < 0.05 for each). Furthermore, the ΣDDT levels in breast milk from China were 10-fold higher than those from Korea and Japan. The present results strongly suggest the presence of extensive emission sources of both dicofol and DDTs in China. However, exposure to dicofol cannot explain the large exposure of Chinese mothers to DDTs because of the trace levels of dicofol in the ΣDDTs. In the present study, dicofol was confirmed to be detectable in human breast milk. This is the first report to identify dicofol in human samples.     

Comparative survey of levels of chlorinated cyclodiene pesticides in breast milk from some cities of China, Korea and Japan

Exposure of mothers to organochlorine pesticides (OCPs) was assessed by measuring the levels of 20 OCPs in 70 human breast milk samples pooled from 210 individuals from China, Korea and Japan. The OCPs were analyzed using gas chromatography/mass spectrometry (GC/MS) in electron capture negative ionization (ECNI) monitoring. The results showed that β-hexachlorocyclohexane and hexachlorobenzene were one order of magnitude higher in China than in the other nations, whereas chlordanes and polychlorinated biphenyl levels were highest in Japan. Heptachlor epoxide, dieldrin, endrin, toxaphenes and mirex were detected in most samples, and levels of these chemicals were significantly higher in Japan (0.8-4.5 ng g⁻¹ lipid), followed by Korea (0.2-4.7 ng g⁻¹ lipid), and lowest in China (less than 1.0 ng g⁻¹ lipid). α- and β-endosulfans were detected at a range of 0.9-1.5 ng g⁻¹ lipid levels in all samples analyzed, and their levels were higher in Korean than in Chinese samples.     

Organohalogen compounds in human breast milk from mothers living in Payatas and Malate, the Philippines: Levels, accumulation kinetics and infant health risk

Human breast milk samples (n = 33) from primipara and multipara mothers from Payatas a waste dump site, and Malate a reference site in the Phillipines were collected in 2004 and analyzed for eight organohalogen compounds, viz., PCBs, DDTs, CHLs, HCHs, HCB, TCPMe, PBDEs and HBCDs. DDTs and PCBs were predominant in all the samples. Overall mean concentrations of PBDEs found in our study were higher (7.5 ng/g lipid wt.) than those reported for Japan and many other Asian countries. Primipara mothers had significantly higher levels of DDTs, CHLs and HCHs than multipara mothers, but not PBDEs and HBCDs. A few individuals accumulated CHLs close to or even higher than the tolerable daily intake guidelines proposed by Health Canada.     

Geographical distribution and accumulation features of PBDEs in human breast milk from Indonesia

The present study reports concentrations of polybrominated diphenyl ethers (PBDEs) and organochlorines (OCs) in human breast milk from Indonesia covering urban, suburban and rural areas. PBDEs were detected in all the samples of the present study with total concentrations ranging from 0.49 to 13 ng/g lipid wt. Geographical distribution showed that concentrations of PBDEs were relatively uniform (p>0.05) and the levels were in the same order as those in Japan and some European countries, but were one or two order lower than North America. When compared to OCs, the level of total PBDEs was lower. The congener pattern was in accordance with other studies on human matrices, in which BDE-47 was the most abundant congener. Variations of PBDE congeners in human breast milk were further discussed to elucidate the potential exposure source(s) and pathways.     

The occurrence of synthetic musks in human breast milk in Sichuan, China

Human breast milk samples collected from mothers (n = 110) who lived in Chengdu, Sichuan Province, southwestern China in 2009 were analyzed to determine the concentrations of 13 musk compounds. Possible relationships between musk concentrations and some personal characteristics were also studied. Only five target analytes were detected in the milk samples analyzed, with median concentration values of 16.5, 11.5, 7.85, <1.5 and <1.4 ng g⁻¹ lipid weight for AHTN (7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene), HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta[γ]-2-benzopyran), HHCB-lactone (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta[γ]-2-benzopyran-1-one), OTNE ([1,2,3,4,5,6,7,8-octahydro-2,3,8,8-tetramethylnaphthalen-2yl]ethan-1-one) and musk ketone (4-tert-butyl-2,6-dimethyl-3,5-dinitroacetophenone, MK), respectively. Mothers who reported high use of hand-cleaning agents, body-cleaning agents, shampoo and hair conditioners, hair dyes and hair gels had significantly elevated milk concentrations of HHCB whereas elevated milk concentrations of AHTN were observed among mothers reporting high use of body-cleaning agents, body lotions, shampoos, hair dyes and hair gels. Younger age showed a significantly positive effect on milk concentrations of both HHCB and AHTN whereas BMI after delivery, the number of children nursed and place of residence (urban or rural) had no significant effect. The estimated median daily intakes of synthetic musks for breast-fed infants were considerably lower than the current provisional tolerable daily intake amounts suggested for adults.     

Polychlorinated dibenzo-p-dioxins, dibenzofurans and polychlorinated biphenyls levels in human breast milk from different regions of Turkey

Human breast milk offers the optimal nutrition for all infants and have been widely used in biomonitoring programs to assess human exposure to lipophylic environmental contaminants such as polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and polychlorinated biphenyls (PCB). There are no previous reports from Turkey on chemically determined levels of PCDDs, PCDFs, and PCBs in human breast milk expressed as World Health Organization (WHO) toxic equivalents (TEQ). To get an overview of the levels of these contaminants in Turkish human milk, samples from 51 Turkish women living in the Ankara, İstanbul, Antalya, Kahramanmaraş, and Afyon provinces were analyzed by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) throughout 2007. The mean concentrations of WHO_PCDD/F-TEQ and WHO_PCB-TEQ of all samples from the five regions were 7.5 and 3.1 pg g⁻¹ on a lipid basis, respectively. PCDD/F concentrations ranged between 0.78 and 29.3 pg WHO-TEQ g⁻¹ fat (1.7 and 36.2 pg WHO-TEQ g⁻¹ fat, respectively, including PCB). Of the five studied locations, the lowest levels of ∑TEQs (PCDD/F + PCB) were found in the Afyon (6.8 pg WHO-TEQ g⁻¹ fat) and the highest in the Antalya (15.6 pg WHO-TEQ g⁻¹ fat) province. The results have been discussed in terms of regions and PCDD/F and PCBs for which analyses had been made. The mean levels of PCDD/Fs and PCBs in Turkish human milk are comparable to that found in other countries.     

Congener-distribution patterns and risk assessment of polychlorinated biphenyls,dibenzo-p-dioxins and dibenzofurans in Korean human milk

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) were analyzed by high-resolution gas chromatography/high-resolution mass spectrometry in human milk samples from an urban and an industrial area in Korea. All PCB congeners were analyzed to characterize the congener distribution as well as to evaluate the toxic equivalent quotient (TEQ) values and the total concentration. In homologue distributions of PCBs, two distinct patterns were found. The mean concentrations of PCDD/Fs and PCBs were 15.13 and 5.64 TEQ pg/g fat (based on WHO TEF, 1997), respectively. The contamination in Korean human milk is comparable to that found in other countries. From these results a daily intake of 60 TEQ pg/kg/day for an infant was estimated. The assumptions were that the infant breast feeds for 1 year, has an average body weight of 10 kg during this period, and ingests 800 g/day of human milk containing a mean concentration of 20.84 TEQ (PCDD/Fs) pg/g fat (based on primipara mothers).     

Levels of organochlorine pesticides in human milk from central Taiwan

The present study determined the residues of organochlorine pesticides (OCPs) in human milk collected in central Taiwan between December 2000 and November 2001. The OCPs were analyzed by GC/MS for 36 human milk samples from healthy women ranging between 20 and 36 years of age. The predominant OCPs were p,p′-DDE, p,p′-DDT, -CHL, heptachlor epoxide, heptachlor, β-HCH, and γ-HCH, with median levels of 228, 19, 7.4, 4.0, 2.3, 1.2, and 0.8 ng/g lipid, respectively. The residues of OCPs in human milk from central Taiwan were comparable to those described in results from Sweden, the United Kingdom, and Japan, and were significantly lower than those from investigations in Asian countries, including China, Thailand, Indonesia, and Vietnam. Low DDE/DDT ratio (mean = 13.6, SD = 6.54) indicated that residual OCPs in human milk mainly originate from past exposure. A notable decrease in DDT levels (∑ DDT = 333 ng/g lipid) in human milk was found in this study compared to results from the previous two decades (∑ DDT = 3595 ng/g lipid). Hypothetically, the level of -CHL was significantly associated with total TEQ levels in Taiwanese human milk because of the sources of food contaminant, i.e. animal fat. Based on low OCP levels in Taiwanese human milk and low estimated median daily intake of total DDTs for a breastfed infant (1358 ng/kg/day) with the assumption of an infant weighting 4 kg and consuming 699 g milk per day in the first month after birth, the Taiwanese policy of breast-feeding promotion was supported.     

Congener-distribution patterns and risk assessment of polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans in Korean human milk

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) were analyzed by high-resolution gas chromatography/high-resolution mass spectrometry in human milk samples from an urban and an industrial area in Korea. All PCB congeners were analyzed to characterize the congener distribution as well as to evaluate the toxic equivalent quotient (TEQ) values and the total concentration. In homologue distributions of PCBs, two distinct patterns were found. The mean concentrations of PCDD/Fs and PCBs were 15.13 and 5.64 TEQ pg/g fat (based on WHO TEF, 1997), respectively. The contamination in Korean human milk is comparable to that found in other countries. From these results a daily intake of 60 TEQ pg/kg/day for an infant was estimated. The assumptions were that the infant breast feeds for 1 year, has an average body weight of 10 kg during this period, and ingests 800 g/day of human milk containing a mean concentration of 20.84 TEQ (PCDD/Fs) pg/g fat (based on primipara mothers).     

Distribution of polybrominated diphenyl ethers in breast milk from North China: Implication of exposure pathways

The breast milk concentrations of polybrominated diphenyl ethers (PBDEs; sum of eight congeners: BDE-28, 47, 99, 100, 153, 154, 183 and 209) were determined (by high resolution gas chromatographic high resolution mass spectrometry) in samples from primiparous women collected in 2006 in Tianjin, China. Dietary and lifestyle habits of the participants were obtained by questionnaires. The median total PBDE concentration (including BDE-28, 47, 99, 100, 153, 154, 183) was 2500 pg g⁻¹ lipid weight, ranging from 1700 to 4500 pg g⁻¹ lipid weight. These levels were in the same range as those from Europe and Japan but much lower than those from North America. The congener profile in China was also different from other countries. The contribution of BDE-28 was around 15%, much higher than any other country, implying that a different Penta-BDE formulation might be used in the Chinese market. The lower ratio of the sum of BDE-47, 99, and 100 to the sum of BDE-153 and 154 suggested that Octa-products were in more demand in China. A significant correlation was found between a woman’s PBDE concentration and the time she used electronic appliances (h/d). This implies that electronics are a potential source of PBDEs to people. Inhalation or ingestion of particulate matter (such as dust) may also be an important exposure pathway. There was no significant correlation between the PBDE concentration and the consumption of meat, fish, and milk. Further research is needed to determine the specific contribution of each exposure route and their health effects.     

Brominated flame retardants and perfluorinated chemicals, two groups of persistent contaminants in Belgian human blood and milk

We assessed the exposure of the Flemish population to brominated flame retardants (BFRs) and perfluorinated compounds (PFCs) by analysis of pooled cord blood, adolescent and adult serum, and human milk. Levels of polybrominated diphenyl ethers (PBDEs) in blood (range 1.6-6.5 ng/g lipid weight, lw) and milk (range 2.0-6.4 ng/g lw) agreed with European data. Hexabromocyclododecane ranged between <2.1-5.7 ng/g lw in milk. Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) dominated in blood and ranged between 1 and 171 ng/mL and <0.9-9.5 ng/mL, respectively. Total PFC levels in milk ranged between <0.5-29 ng/mL. A significant increase in PBDE concentrations was detected from newborns (median 2.1) to the adolescents and adults (medians 3.8 and 4.6 ng/g lw, respectively). An identical trend was observed for PFOS, but not for PFOA. We estimated that newborn exposure to BFRs and PFCs occurs predominantly post-natally, whereas placental transfer has a minor impact on the body burden.     

母乳与牛乳中微量元素的比较

用ＩＣＰ－ＡＥＳ法对母乳和牛乳中Ｋ、Ｎａ、Ｃａ、Ｍｇ、Ｐ、Ｆｅ、Ａｌ、Ｚｎ、Ｓｒ、、Ｐｂ、Ｍｎ、Ｂａ和Ｃｕ等１３种元素含量进行了测定。结果发现母乳与牛乳的营养成分差异较大。研究了深入探讨微量元素在人体内重要的生理功能提供了有用的参考数据。     

Levels and profiles of PCDDs,PCDFs and cPCBs in Belgian breast milk. Estimation of infant intake

Congener-specific analyses of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and non-ortho (coplanar) polychlorinated biphenyls (cPCBs) were performed on 20 non-pooled breast milk samples collected in or close to an industrial area of Wallonia (Belgium). PCDD/F concentrations ranged between 16.0 and 52.1 pg TEQ/g fat, with a mean value of 29.4 pg TEQ/g fat. If coplanar PCBs (77, 126, 169) are included in TEQ calculations, levels ranged between 22.2 and 100.2 pg TEQ/g fat, with a mean value of 40.8 pg TEQ/g fat. It appears that 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF and PCB-126 account for more than 90% of the TEQ. Estimated PCDD/F dietary intake is 76 pg TEQ/kg body weight (bw)/day. This value is almost 20 times higher than the World Health Organization tolerable daily intake. A value of 103 pg TEQ/kg bw/day represents the intake of PCDDs, PCDFs and cPCBs (no mono-ortho PCBs included).     

Occurrence of co-planar polybrominated/chlorinated biphenyls (PXBs), polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in breast milk of women from Spain

In this study, for the first time, levels and accumulation profiles of eight currently available polybrominated/chlorinated biphenyl congeners (PXBs; XB-77, -105, -118, -126A, -126B, -126C, -156 and -169, named according to IUPAC nomenclature) in human breast milk collected form Spanish women in 2005 were reported. Concentrations and congener specific profiles of polychlorinated biphenyls (PCBs), including co-planar PCBs, (co-PCBs) and polybrominated diphenyl ethers (PBDEs) were also reported.A concentration of 0.45 pg g⁻¹ lipid weight was found for total PXBs, and arithmetic mean concentrations of 125, 25 and 5.5 ng g⁻¹ lipid weight were determined for total PCBs, co-PCBs and total PBDEs respectively. Detectable levels of all congeners investigated, except CB-123 and XB-169 were found. Levels of PCBs were similar to those found in Spanish samples collected after 2000, and lower than those obtained before 2000. CB-138, -153 and -180 were the predominant PCB congeners. PBDE levels, dominated by BDE-47, -99, -100 and -209, were lower than PCB levels. PXB concentrations were the lowest, with XB-156 being the most abundant. The concentration levels of PCBs and PBDEs found in this study were in the same range as those from other European countries. Levels of PXBs were much lower than published values determined in Japan which were the only data found in the literature.     

National survey of the levels of persistent organochlorine pesticides in the breast milk of mothers in China

The occurrence of persistent organochlorine pesticides (OCPs) in breast milk samples collected from mothers from twelve provinces in mainland China was investigated. Dichlorodiphenyltrichloroethanes (DDTs) were the most prevalent agent, followed by HCHs and HCB, whereas levels of chlordane compounds, drins and mirex were lower. The relatively lower DDE/DDT ratio in the Fujian rural area suggested more recent exposure to DDT than in other areas. The mean level of DDTs in breast milk from the southern China was higher than those from northern China (p < 0.05). A positive correlation was observed between concentration of DDTs in human milk and consumption of animal-origin food, suggesting that this parameter could play an important part in influencing OCPs burdens in lactating women. The mean estimated daily intakes of different OCPs for breastfed infants were lower than the tolerable daily intake.     

Determination of chlorinated pesticides, polychlorinated biphenyls, and polybrominated diphenyl ethers in human milk from Bizerte (Tunisia) in 2010

Thirty persistent organohalogen compounds including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were determined in breast milk samples (n = 36) of primipara and multipara mothers from Bizerte in 2010. The analytical procedure involved the application of liquid-liquid extraction and gas chromatography with electron capture detector (GC-ECD) or mass spectrometry detector (GC-MS) for identification and quantification. Organohalogen compounds were found in all the analyzed samples, with predominance of p,p′-DDE, p,p′-DDT, p,p′-DDD, HCB and PCBs. The mean concentration of ∑DDTs in breast milk was 1163.9 ng g⁻¹ lipid wt. The ratio of p,p′-DDE/p,p′-DDT was low, suggesting that there is fresh intake of commercial DDT products in Bizerte. The mean levels of HCB and PCB were 286.8 and 331.2 ng g⁻¹ lipid wt respectively. These results were compared with the levels obtained in a previous study carried out in the same area in 2003. A general decrease of ∑DDTs levels and an increase of PCB levels were observed. Among the 10 PBDE congeners evaluated, BDE-28, BDE-47, BDE-99, BDE-66, BDE-138, BDE-100, BDE-154, BDE-153, and BDE-183 were detected in the analyzed samples at different frequency. The total PBDE concentrations ranged from 2.5 to 22.6 ng g⁻¹ lipid wt in the samples, with a mean and median value of 10.7 and 9.8 ng g⁻¹ lipid wt respectively. To our knowledge, this is the first data of PBDEs in Tunisian human milk. The present study shows that age and parity are factors influencing the levels of some organohalogen compounds in human milk.     

Trend studies of polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans in human milk

Human milk has been used in studies of long-term changes in the concentrations of organochlorine contaminants in mothers from the Stockholm region. The previously observed decline (1972 to 1985) in the levels of polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) seems to have ceased for certain compounds since the levels were about the same in samples collected in 1985 and 1989. Calculating with the proposed toxicity equivalency factors for the different congeners of PCDDs, PCDFs and PCBs it is seen that the congeners of PCBs contribute more to the possible toxicity than those of PCDDs and PCDFs. The mono-ortho substituted congener 2,3′,4,4′,5-pentachlorobiphenyl (IUPAC No. 118) contributes with the largest part.     

Historical trends in human dietary intakes of endosulfan and toxaphene in China, Korea and Japan

Recently, the Stockholm Convention prohibited the use of toxaphene and has been reviewing endosulfan. The historical use of these pesticides may contaminate food and tend to accumulate in the food chain. In this study, to evaluate the spatial and temporal trends of food contamination, the endosulfan and toxaphene levels were measured in pooled 24-h food composite samples from Chinese (n = 10), Korean (n = 10) and Japanese (n = 40) adults in the 1990s and 2007-2009. Endosulfan was detected in 32 of 40 samples from Japan, but its levels (sum of α- and β-isomers) were low in both the 1990s and 2009 (range as geometric mean (geometric standard deviation) [GM (GSD)]: 0.96 (1.6)-1.42 (1.4) ng kg⁻¹ d⁻¹). The dietary intakes of endosulfan in Seoul as GM (GSD) were 38.68 (1.3) ng kg bw⁻¹ d⁻¹ in 1994 and 92.17 (4.4) ng kg bw⁻¹ d⁻¹ in 2007, and significantly higher than those in Japan (p < 0.05). The samples from Beijing showed a 50-fold increase in the endosulfan levels from 1993 (GM: 0.58 ng kg⁻¹ d⁻¹) to 2009 (GM: 24.91 ng kg bw⁻¹ d⁻¹) (p < 0.05). Toxaphene was detected in 33 of 40 samples from Japan. The dietary intake of toxaphene in Japan (sum of Parlars #26, #50 and #62) was 0.32-1.21 ng kg bw⁻¹ d⁻¹ (range as geometric mean) and no temporal trend was observed. The dietary intake of toxaphene in Seoul increased significantly from 0.2 ng kg bw⁻¹ d⁻¹ (GM) in 1994 to 3.6 ng kg bw⁻¹ d⁻¹ (GM) in 2007 (p < 0.05). Only one of 10 pooled samples from Beijing contained a detectable level of toxaphene (0.3 ng kg bw⁻¹ d⁻¹). For the entire population, the risk of adverse health effects from dietary intakes of endosulfan and toxaphene is unlikely. However, the concentrations of endosulfan in several samples exceeded 10% of the acceptable daily intake limit value of 6 μg kg bw⁻¹ d⁻¹ set by the World Health Organization (WHO). It appears important to refine dietary intake estimates targeting food types and source identification to ensure safe food for consumers.     

Dioxin concentration in human milk in Hebei province in China and Tokyo, Japan: potential dietary risk factors and determination of possible sources

Very limited information is available on body burdens and environmental levels of dioxins and dioxin-like PCBs (dl-PCBs) in mainland China. In the current studies, human milk samples were collected from 30 breastfeeding mothers in Shijiazhuang city (industrialized) and 11 in the Tanshan countryside (agricultural) of Hebei Province in northern China. An additional 20 samples were obtained from mothers in Tokyo, Japan. PCDDs, PCDFs, and dl-PCBs in human milk were analyzed by high-resolution gas chromatography/high-resolution mass spectrometry. Our results show that arithmetic means for body burdens of PCDDs/Fs and dl-PCBs in Hebei were 3.6 and 1.9 pg TEQ g⁻¹ fat, respectively, which were only about one fourth of the levels in Japan. In addition, no difference was found in the chemical levels except dl-PCBs between the urban and rural areas. Based on the results of an in-person interview of the Chinese mothers using a 59-item questionnaire, freshwater fish consumption was found to correlate with the body burden of dioxins. Principal component analysis of dioxin congeners revealed that the patterns of dioxins in the Hebei urban and rural areas are quite similar; however, they are clearly different from those in Japan. Collectively, our results suggest that the lower body burdens of dioxin in Hebei may be due in part to the relatively slow industrialization and a lower consumption of marine foods. Finally, the results indicate that comprehensive monitoring of dioxins and dl-PCBs in humans as well as in the environment and foods is necessary in China.     

Partitioning of persistent organic pollutants (POPs) between human serum and breast milk: A literature review

The literature was reviewed to assess the relationship between the lipid adjusted concentration in human serum and breast milk (expressed as the serum/milk ratio) of a broad range of POPs in paired samples. Thirteen studies were identified, including seven studies that reported serum/milk ratios for polychlorinated dibenzo-dioxins and -furans (PCDD/Fs), ten for polychlorinated biphenyls (PCBs), five for polybrominated diphenyl ethers (PBDEs), and five for organochlorine pesticides (OCPs). Mean serum/milk ratios ranged between 0.7 and 25 depending on the compound and congener. For PCDD/Fs, PCBs and PBDEs, a clear trend of increasing mean serum/milk ratio by increasing molar volume, hydrophobicity and number of halogen substitutes was observed. The mean serum/milk ratios reported by the 13 studies summarized here will aid comparison between human POPs exposure studies using either serum or milk samples. More studies are needed to allow a valid comparison between data obtained from analysis of breast milk and serum samples for a broader range of POPs. Furthermore such studies may shed light on compound specific factors as well as other determinants that may affect the partitioning and partition kinetics of POPs between serum and breast milk.