Polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls in human milk in Osaka City, Japan

The potential health risks of exposure to environmental chemicals - Global implications for future generations

In 2001, we launched the Hokkaido Study, the first prospective birth cohort study in Japan. We are currently tracking the effects of environmental chemicals, using a life course approach. The study examines life circumstances after birth, and the longest follow-up to date is 20 years of age. We have measured prenatal exposure to dioxins, organochlorine pesticides, per- and polyfluoroalkyl substances, plasticizers such as di(2-ethylhexyl) phthalate, and bisphenol A. Our findings have mostly revealed that increased exposure to these environmental chemicals is linked to increased risk of lower birth size, effects on thyroid and steroid hormones, adipokine levels, as well as disruption of neurodevelopment, including causing asthma and respiratory symptoms. However, it should be noted that our findings also include protective or null findings, which may be due to low chemical concentrations or differences in prenatal or postnatal exposure. We would like to emphasize the importance of long-term continuation of the cohort, effective utilization of the data, and application of the results to environmental and health policies.

Serum dioxin concentrations in military workers at three dioxin-contaminated airbases in Vietnam

An estimated 91,998,400 L of herbicides were stocked at three US airbases in Vietnam between 1962 and 1971. These herbicides were contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-tetraCDD). In 2017, we sampled blood from 120 male Vietnamese military workers in the three dioxin-contaminated airbases (Bien Hoa, Da Nang, and Phu Cat) and from 20 workers at an uncontaminated airbase. 2,3,7,8-tetraCDD concentrations were highest in samples from Bien Hoa (18.2 pg/g lipid), followed by samples from Da Nang (9.2 pg/g lipid), Phu Cat (3.7 pg/g lipid), and the reference base (2.1 pg/g lipid). In Bien Hoa, 31 of the 50 subjects had blood 2,3,7,8-tetraCDD levels in the range of 10-100 pg/g lipid and four subjects had 2,3,7,8-tetraCDD levels that exceeded 100 pg/g lipid. In Da Nang, almost half of the subjects had blood 2,3,7,8-tetraCDD concentrations in the range of 10-100 pg/g lipid. These findings suggest that military workers at contaminated bases are the population most vulnerable to dioxin exposure, especially at Bien Hoa.

Birth cohorts in Asia: The importance, advantages, and disadvantages of different-sized cohorts

Asia contains half of the world's children, and the countries of Asia are the most rapidly industrializing nations on the globe. Environmental threats to the health of children in Asia are myriad. Several birth cohorts were started in Asia in early 2000, and currently more than 30 cohorts in 13 countries have been established for study. Cohorts can contain from approximately 100-200 to 20,000-30,000 participants. Furthermore, national cohorts targeting over 100,000 participants have been launched in Japan and Korea. The aim of this manuscript is to discuss the importance of Asian cohorts, and the advantages and disadvantages of different-sized cohorts. As for case, one small-sized (n=514) cohort indicate that even relatively low level exposure to dioxin in utero could alter birth size, neurodevelopment, and immune and hormonal functions. Several Asian cohorts focus prenatal exposure to perfluoroalkyo substances and reported associations with birth size, thyroid hormone levels, allergies and neurodevelopment. Inconsistent findings may possibly be explained by the differences in exposure levels and target chemicals, and by possible statistical errors. In a smaller cohort, novel hypotheses or preliminary examinations are more easily verifiable. In larger cohorts, the etiology of rare diseases, such as birth defects, can be analyzed; however, they require a large cost and significant human resources. Therefore, conducting studies in only one large cohort may not always be the best strategy. International collaborations, such as the Birth Cohort Consortium of Asia, would cover the inherent limitation of sample size in addition to heterogeneity of exposure, ethnicity, and socioeconomic conditions.

Prenatal exposure to dioxin-like compounds is associated with decreased cord blood IgE and increased risk of wheezing in children aged up to 7years: The Hokkaido study

INTRODUCTION

In utero exposure to dioxin-like compounds (DLCs) may cause imbalance of immune development in early infancy. However, there are few epidemiological studies into the effects of in utero exposure to DLCs on allergies and infections during childhood. This study evaluates associations between concentrations of maternal DLCs and cord blood immunoglobulin (Ig) E, as well as allergies and infections during childhood.

METHOD

We recruited 514 pregnant women in a maternity hospital in Sapporo, Japan, and measured concentrations of DLCs in 426 maternal blood samples using high-resolution gas chromatography/high-resolution mass spectrometry. We examined the relationship between concentrations of maternal DLCs and cord blood IgE at birth (n=239), as well as for allergies and infections in children at 3.5 (n=327) and 7 (n=264) years, using regression analysis adjusted for confounding variables.

RESULTS

We found a positive association between maternal DLC concentrations and frequency of wheezing in children aged up to 7years [odds ratio (OR); 7.81 (95% confidence interval (CI), 1.42 to 42.9)]. At 3.5years, boys showed inverse associations between maternal DLC concentrations and cord blood IgE [partial regression coefficient; -0.87 (95% CI), -1.68 to -0.06], and frequency of wheezing [OR; 0.03 (95% CI), 0.00 to 0.94] but girls did not.

DISCUSSION

As one reason for the significant association observed at 7 but absent at 3.5years, we suggest that allergic symptoms are more obvious in older children due to matured immune function.

CONCLUSION

The findings suggest that prenatal exposure to DLCs may modify offspring immune responses and result in increased risk of allergy among children of school age.

Dioxins and Nonortho PCBs in Breast Milk of Vietnamese Mothers Living in the Largest Hot Spot of Dioxin Contamination

Bien Hoa Air Base is the largest dioxin contamination hot spot in Vietnam. In 2012, we recruited 216 mothers who were living in 10 communities around Bien Hoa Air Base and had delivered newborns at a prefecture hospital, and we investigated recent exposure levels of dioxins and nonortho PCBs in their breast milk. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-tetraCDD) was present at 2.6 pg/g lipid in primiparae and 2.2 pg/g lipid in multiparae. Among multiparae and total subjects, significant high prevalence of 2,3,7,8-tetraCDD≥5 pg/g lipid and 2,3,7,8-tetraCDD contribution≥40% were observed in mothers living in the five communities closest to Bien Hoa Air Base. The TEQ for nonortho PCBs was 1.6 pg-TEQ/g lipid for primiparae, and this was even lower than that in the unsprayed area. The length of residency was a strong factor to increase dioxins, including 2,3,7,8-tetraCDD. Residency in the five communities with the highest exposure was a specific risk factor for increased 2,3,7,8-tetraCDD in breast milk. Food intake might contribute partly to the increased levels of dioxin congeners other than 2,3,7,8-tetraCDD in breast milk. These results suggest that Bien Hoa Air Base has led to elevated 2,3,7,8-tetraCDD levels in breast milk of mothers in nearby areas even in the recent years.

Maternal risk factors associated with increased dioxin concentrations in breast milk in a hot spot of dioxin contamination in Vietnam

This study looked to identify determinants of exposure to dioxin in breast milk from breast-feeding women in a hot spot of dioxin exposure in Vietnam. Breast milk was collected from 140 mothers 1 month after delivery. The risk factors investigated included length of residency, drinking of well water and the frequency of animal food consumption. Cluster analysis was performed to identify dietary patterns of fish and meat portions, fish variety and egg variety. Residency, age and parity were clearly associated with increased dioxin levels. Drinking well water and the consumption of marine crab and shrimps were related to higher levels of furans in breast milk. The consumption of quail eggs also appeared to be associated with increased levels of some dioxin isomers in this area. Some mothers who ate no or less meat than fish and mothers who consumed more freshwater fish than marine fish had lower levels of dioxins in their breast milk. However, the type of water and the eating habits of mothers contributed only partly to the increased dioxin levels in their breast milk; the length of residency was the most important risk factor associated with increased dioxin body burdens of mothers.

Polychlorinated biphenyls and organochlorine pesticides in human milk samples from two regions in Croatia

We analyzed 20 polychlorinated biphenyls (PCBs) and seven organochlorine pesticides (OCPs) in milk samples collected during 2009-2011 from primiparae living in two different regions in Croatia. p,p'-DDE is the dominant organochlorine pesticide. α-HCH/γ-HCH and p,p'-DDE/p,p'-DDT ratios indicate that there is fresh input of γ-HCH in investigated population on both locations, while this is not applicable to p,p'-DDT. The PCB profile was dominated by higher chlorinated congeners. Non-ortho PCB congeners which have the highest TEF values were not detected in any of individual samples. Toxic equivalents for mono-ortho substituted PCB congeners indicated higher exposure to toxic PCBs in Zadar, but estimated daily intakes for both locations indicate that infants consuming mother's milk are not at risk of adverse effects caused by PCBs and OCPs. Our study builds on the previous research of human milk samples collected in Zagreb and reveals that over 10-year period, levels of investigated organochlorine compounds decreased significantly.

Levels and profiles of PCDD/Fs, PCBs in mothers' milk in Shenzhen of China: estimation of breast-fed infants' intakes

Sixty breast milk samples were collected in Shenzhen, China from July to November in 2007. The samples were analyzed of the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs). The range of upper-bound for ∑TEQ-(PCDD/Fs+PCBs) in the samples was 4.10-35.3 pg TEQ g(-1) lipid (median: 10.6 pg TEQ g(-1) lipid; mean: 11.9 pg TEQ g(-1) lipid). The levels of the measured contaminants in the breast milk had significant correlations with the length of inhabitation period in Shenzhen (r=0.487, p<0.05 for PCDD/Fs, r=0.431, p<0.05 for PCBs and r=0.478, p<0.05 for ∑TEQ-(PCDD/Fs+PCBs)), and the consumption rate of fish (r=0.366, p<0.05 for PCDD/Fs, r=0.486, p<0.05 for PCBs and r=0.416, p<0.05 for ∑TEQ-(PCDD/Fs+PCBs)), respectively. Moreover, significant positive correlations were also detected between the participant's age (r=0.305, p<0.05 for ∑TEQ-PCBs and r=0.275, p<0.05 for ∑TEQ-(PCDD/Fs+PCBs)) and the body burdens of these contaminants respectively. It is estimated that the daily intake (EDI) of the sum of PCDD/Fs and DL-PCBs by the breast-fed infants was 5.60-161 pg TEQ kg(-1) bw per day (mean: 48.2 pg TEQ kg(-1) bw per day; median: 42.2 pg TEQ kg(-1) bw per day). The result showed that both the body burdens of PCDD/Fs and PCBs of the recruit population and the calculated EDI of the breast-fed infants were higher than those in the non-exposed areas in mainland China. This suggests that continuous surveillance on PCDD/Fs and PCBs levels in human milk is critical to more precisely evaluate the human health risk posed by the negative environmental impact in Shenzhen in the future.

PCDD, PCDF, PCB and PBDE concentrations in breast milk of mothers residing in selected areas of Slovakia

The concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyls (dl-PCBs) and polybrominated diphenylethers (PBDEs) in 33 breast milk samples collected in 2006-2007 from primipara mothers close to four industrial areas of Slovak Republic were determined. The total PCDDs/PCDFs and dl-PCBs expressed as TEQ based on WHO TEFs 1998 in breast milk samples varied from 5.0 to 51.8 pg g(-1) fat (median: 13.1 pg g(-1) fat; mean: 18.0 pg g(-1) fat). The measurements of seven PBDE congeners (IUPAC No. 28, 47, 99, 100, 153, 154, and 183) were performed for the first time in human milk from Slovakia. PBDE levels ranged between 0.22 and 1.62 ng g(-1) fat, with median and mean value of 0.43 ng g(-1) fat and 0.57 ng g(-1) fat respectively. No statistically significant differences were observed between studied areas in total PBDE concentrations. Furthermore, this study presents first results concerning the daily intake (DI) of PCDDs/PCDFs and dioxin-like compounds for the most vulnerable breast-fed infant population in Slovakia. The total PCDD/PCDF and dl-PCB DI for an infant during the first 2 months of life was estimated in a range from 14.4 to 230 pg TEQ kg(-1)b.w., with a median value of 58.9 pg TEQ kg(-1)b.w.. The DI values substantially exceeded the tolerable daily intake (TDI) 1-4 pg TEQ kg(-1)b.w. recommended by WHO. The dietary infant intake concerning PBDEs was estimated to be between 0.69 and 7.1 ng kg(-1)b.w.d(-1), with median value of 1.7 ng kg(-1)b.w.d(-1).

PCDD/Fs and dioxin-like PCBs in human milk and estimation of infants' daily intake: a review

This paper reviews the recent scientific literature on PCDDs, PCDFs and dioxin-like PCBs in human milk. All the papers reporting levels of these contaminants in human breast milk published from January 2000 to January 2009 and available on the www.sciencedirect.com web site were identified and included. The aim was (1) to study levels of PCDDs, PCDFs and PCBs in human milk in mothers from different geographical areas and assess infant exposure to these contaminants; (2) to study the effect of variables such as the mother's age, number of deliveries, dietary and smoking habits and her own nutrition in infancy, and the environment, on levels of the contaminants in breast milk; (3) to study time patterns, and (4) to identify data gaps.

A survey of dietary intake of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like coplanar polychlorinated biphenyls from food during 2000-2002 in Osaka City, Japan

Studies of the dietary intake of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like coplanar polychlorinated biphenyls (dioxin-like PCBs), collectively referred as dioxins, were conducted using the total diet study (TDS) method with food purchased in Osaka City, Japan during 2000-2002. The daily intake of dioxin-TEQ (toxic equivalent) from food per adult person was estimated respectively as 104.24 pg TEQ/person/day in 2000, 72.73 pg TEQ/person/day in 2001, and 87.28 pg TEQ/person/day in 2002, corresponding to 2.08, 1.45, and 1.74 pg TEQ/kg body weight (bw)/day for an adult weighing 50 kg. The highest contribution ratio to the total intake of dioxin-TEQ was from fish and shellfish (group 10) in each year, accounting for 77-92%. The next highest contributor was meat and eggs (groups 11-A and 11-B). An annual decrease of the intake of dioxin-TEQ was not observed clearly. Otherwise, the dietary intake of non-2,3,7,8-substituted PCDDs/PCDFs were estimated together. The intake of 1,3,6,8-TeCDD came mostly from intake of fish and shellfish (group 10), green vegetable (group 7), and the other vegetables, including mushrooms and seaweed (group 8). In addition, the intake of 1,3,6,8-TeCDF, which reportedly antagonizes 2,3,7,8-TeCDD-mediated aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (EROD) induction activities, was an insufficient amount to suppress 2,3,7,8-TeCDD-mediated activities. Furthermore, we discussed different TEQ compositions of PCDDs/PCDFs to dioxin-like PCBs from food intake and in human samples and inferred that the difference was caused by low bioaccumulation properties of 3,3',4,4',5-PeCB (PCB 126).

[Levels and distribution of PCBs and organochlorine pesticides in the air, pine needles, and human milk]

This review presents the findings on the distribution and levels of 20 congeners of polychlorinated biphenyls (PCBs) and 7 organochlorine pesticides (OCPs) all over the world, based on measurements in samples of air, human milk and pine needles. The Institute for Medical Research and Occupational Health has been conducting research in all three matrices for many years, and this review summarises its results too. Significant decrease in concentrations of organochlorine compounds has been seen after the legal ban of their use, but that decresing trend has been slowed down and they are still found in all samples. In general, higher PCB levels are found in samples from urban locations, pesticides levels are higher in samples from locations where has been their probable usage in agriculture, while HCB levels are usually indicator of industrial activity.γ-HCH has been found in the highest concentration in air and pine needles samples, while in humans DDE and β-HCH are the most abundant compounds. Indicator PCB congeners are also differently present in environment and humans: in air and pine needles lower-chlorinated, more volatile PCB congeners have higher concentrations while in humans that goes for more persistent higher-chlorinated PCB congeners. Among toxic ortho-substituted PCB congeners in human and environmental samples the most abundant is PCB-118 while three non-ortho substituted congeners (PCB-77, PCB-126 and PCB-169) that are the most toxic ones are rarely detected. From organochlorine pesticides, DDD is found in lowest concentrations in all samples.

The effect of waste combustion on the occurrence of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) in breast milk in Italy

Levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were measured in the breast milk of mothers living in Giugliano (Campania, Italy), an area at increased risk of PCDD and PCDF exposure caused by recent and serious open-air waste-combustion accidents. Polychlorinated biphenyls (PCBs) in milk samples were also studied. Breast milk was also monitored in two cities in northern Italy, Milan and Piacenza, which were selected as controls. Other variables, such as diet and age of the mothers, were also studied. PCDD/F and PCB levels and congener profiles in breast-milk samples were similar in all these cities, though total PCDD/F and DL-PCB TEQs in samples from Giugliano were significantly lower than those in Milan and Piacenza (8.65 pg WHO-TEQ in Giugliano vs. 11.0 and 9.94 pg WHO-TEQ in Milan and Piacenza respectively). Thus no direct correlations were found between PCDD/F and PCB levels in breast milk and the suspected increased exposure through open-air waste combustion in Giugliano. Diet did not seem to affect PCDD/F and PCB levels, whereas a significant correlation was observed between the mother's age and an increased concentration of PCDDs/Fs and PCBs in milk. Comparison of these findings with those of previous surveys in Italy in 2000-2001 showed a marked reduction of PCDD/F (about 60%) and DL-PCB (about 20%) levels in breast milk occurring over the last 10 years. This might well be a result of well functioning legislation, for example European Directives on of the reduction of the emission limits of PCDDs/Fs and PCBs from waste incineration set by EU Directive 2000/76/EC implemented in 2000, or Commission Regulations such as (EC) No. 466/2001 and 1881/2006 setting maximum levels for certain contaminants in foodstuffs.

Effects of maternal dioxin exposure on newborn size at birth among Japanese mother-infant pairs

OBJECTIVE

Maternal exposure to dioxins [polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (DFs)] during pregnancy is known to affect infant growth and neurodevelopment in humans and animals. The aim of this study was to investigate the relationship between newborn size and the concentration of dioxin isomers in breast milk and to subsequently evaluate the potential toxicity of each dioxin isomer among mothers living in sea coast areas who are at a high risk of contamination due to a high consumption of fish.

METHODS

A total of 75 milk samples were obtained within 1 month of delivery from Japanese mothers living in the coastal areas of the Japan Sea. The relationships between the levels of seven dioxins and ten furan isomers in maternal breast milk, measured by high-resolution-gas chromatography/mass spectrometry, and the birth size of newborns, which is related to fetal growth, were investigated after adjustment for confounding factors.

RESULTS

The concentrations of 1,2,3,6,7,8-HxCDD (hexachlorodibenzo-p-dioxin), 2,3,4,7,8-PeCDF (pentachlorodibenzofuran), 2,3,4,6,7,8-HxCDF, and three dioxin toxic equivalent (TEQ) levels (PCDDs-TEQ, PCDFs-TEQ, and total-TEQ) in maternal breast milk were inversely correlated to newborn length even after adjustment for gestational weeks, infant sex, and maternal age and height. These isomers were abundant among the 17 isomers tested and reflected the TEQ levels. Only 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), the most toxic isomer, was negatively correlated with newborn head circumference, even after adjustment for gestational weeks, infant birth weight, and other confounding factors.

CONCLUSIONS

Based on our results, fetal growth may be influenced by maternal total exposure to dioxins, but only exposure to 2,3,7,8-TCDD would appear to possibly affect fetal head size during pregnancy.

Concentrations of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls in blood and breast milk collected from 60 mothers in Sapporo City, Japan

We measured the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), non-ortho polychlorinated biphenyls (non-ortho PCBs), and mono-ortho polychlorinated biphenyls (mono-ortho PCBs) in paired samples of blood and breast milk collected from 60 mothers in Sapporo City, Hokkaido Prefecture, Japan. The present study is one of the few studies in which PCDDs, PCDFs, and dioxin-like PCBs have been measured in blood and breast milk collected from 60 same mothers. Of these 60 mothers, 30 were primipara (mean: 30.1 years, median: 28.0 years) and 30 were multipara (mean: 32.2 years, median: 32.5 years). The arithmetic mean TEQ concentrations of PCDDs, PCDFs, non-ortho PCBs, and mono-ortho PCBs in blood and breast milk of the primiparous mothers were 9.0, 3.3, 5.7, and 0.4 pg TEQ g(-1) lipid, respectively, and 5.2, 2.2, 4.5, and 0.4 pg TEQ g(-1) lipid, respectively, with the total TEQ concentrations of these dioxin-like compounds being 9.3-42.9 (mean: 18.4, median: 17.3) and 7.0-41.1 (mean: 12.3, median: 11.4) pg TEQ g(-1) lipid, respectively. In the case of multiparous mothers, the arithmetic mean TEQ concentrations of these dioxin-like compounds in blood and breast milk were 7.1, 2.7, 5.3, and 0.4 pg TEQ g(-1) lipid, respectively, and 3.9, 1.7, 3.8, and 0.4 pg TEQ g(-1) lipid, respectively, with the total TEQ concentrations being 3.4-28.1 (mean: 15.5, median: 13.9) and 2.7-20.0 (mean: 9.8, median: 9.2)pg TEQ g(-1) lipid, respectively. The total TEQ concentrations of PCDDs, PCDFs, non-ortho PCBs, and mono-ortho PCBs in blood and breast milk of primiparous mothers in Sapporo City appeared to be generally lower than those recently surveyed throughout the greater area of Japan. Significant correlations were observed between age and the total TEQ concentrations of PCDDs, PCDFs, non-ortho PCBs, and mono-ortho PCBs in the blood of primiparae and multiparae, and significant correlations were also observed between age and the total TEQ concentrations of these dioxin-like compounds in the breast milk of primiparae and multiparae. The total TEQ concentrations of PCDDs, PCDFs, and dioxin-like PCBs in the blood of primiparous mothers showed a close correlation to those in their breast milk and also showed good correlations between the total TEQ concentrations of these dioxin-like compounds in the blood of multiparous mothers and those in their breast milk. The result of a comparison of the arithmetic mean concentrations of each congener of PCDDs, PCDFs, non-ortho PCBs, and mono-ortho PCBs in blood and breast milk indicated that the transfer of octachlorodibenzo-p-dioxin (OCDD) from the blood to the breast milk was lower than those of other congeners. In contrast, among mono-ortho PCBs congeners, the arithmetic mean concentrations of 2,3',4,4',5-pentachlorobiphenyl (PentaCB) (#118) and 2,3,3',4,4'-PentaCB (#105) in the breast milk were slightly higher than those in the blood, which suggested that breast-fed infants may be at higher risk from mono-ortho PCBs.

2,3,7,8-Tetrachlorodibenzo-p-dioxin in maternal breast milk and newborn head circumference

Dioxins are known to affect infant growth and neurodevelopment in both humans and animals. In this study, we examined the relationship between neonatal head circumference, which is related to fetal brain development, and the concentration of dioxins in breast milk as an indicator of maternal exposure. A total of 42 milk samples were obtained on the fifth to eighth postpartum day from mothers in Japan exposed to dioxins in the environment. The levels of seven dioxins and 10 furan isomers were measured in each milk sample using an HR-GC/MS system. The relationships between the concentration of each dioxin isomer and newborn size, including head circumference, were then investigated after adjustment for confounding factors. The concentration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most toxic dioxin isomer, negatively correlated with newborn head circumference, even after adjustment for gestational age, infant sex, parity and other confounding factors. However, there were no significant relationships between the concentration of other dioxin and furan isomers in maternal breast milk and infant height, weight and chest circumference at birth. These facts suggested that fetal brain development might be influenced by maternal exposure to TCDD in the environment.

Recent global trends and physiologic origins of dioxins and furans in human milk

Restrictions on releases of polychlorinated dibenzo-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) to the environment from industrial practices have resulted in an attendant decrease in levels of these compounds in the environment. Continued environmental monitoring and biomonitoring of PCDDs/Fs ensure that exposures do not increase unexpectedly or unnoticed. Perhaps the most highly exposed part of the population, however, is the breastfed infant and a periodic assessment of levels of dioxins and furans in human milk provides exposure information for infants. A previous international review of levels of PCDDs/Fs in human milk based on data from the 1970's to the mid-1990's showed a decline in many countries for which data were available. In this paper, recent (1998-2005) global data on PCDDs/Fs in human milk are described. A comparison of these recent data to pre-1998 data suggests a continuing decline in global levels of PCDDs/Fs in human milk. In addition, this paper explores research on physiological origins of these compounds in human milk (e.g., adipose tissue mobilization, recent dietary exposures). The question of whether the presence of PCDDs/Fs in milk is from the lifetime accumulation of PCDDs/Fs in adipose tissue or current diet (or, as is more likely, a complex combination of both) remains unanswered. Whether diet during lactation has a greater influence on milk levels PCDDs/Fs levels than previously suspected, and whether infant exposures to PCDDs/Fs via breastfeeding could be reduced by changes in diet during lactation, are important--and currently unexplored--lines of inquiry.