Polychlorinated biphenyls and organochlorine pesticides in milk and blood of Canadian women during lactation

Human risk associated with exposure to mixtures of antiandrogenic chemicals evaluated using in vitro hazard and human biomonitoring data

BACKGROUND

Scientific evidence for underestimated toxicity from unintentional exposure to chemical mixtures is mounting. Yet, harmonized approaches on how to assess the actual risk of mixtures is lacking. As part of the European Joint programme 'Human Biomonitoring for Europe' we explored a novel methodology for mixture risk assessment of chemicals affecting male reproductive function.

METHODOLOGY

We explored a methodology for chemical mixture risk assessment based on human in vitro data combined with human exposure data, thereby circumventing the drawbacks of using hazard data from rodents and estimated exposure intake levels. Human androgen receptor (hAR) antagonism was selected as the most important molecular initiating event linked to adverse outcomes on male reproductive health.

RESULTS

Our work identified 231 chemicals able to interfere with hAR activity. Among these were 61 finally identified as having both reliable hAR antagonist and human biomonitoring data. Calculation of risk quotients indicated that PCBs (118, 138, 157), phthalates (BBP, DBP, DIBP), benzophenone-3, PFOS, methylparaben, triclosan, some pesticides (i.e cypermethrin, β-endosulfan, methylparathion, p,p-DDE), and a PAH metabolite (1-hydroxypyrene) contributed to the mixture effect. The major chemical mixture drivers were PCB 118, BBP, PFOS, DBP, and the UV filter benzophenone-3, together contributing with 75% of the total mixture effect that was primarily driven by high exposure values.

CONCLUSIONS

This viable way forward for mixture risk assessment of chemicals has the advantages of (1) being a more comprehensive mixture risk assessment also covering data-poor chemicals, and (2) including human data only. However, the approach is subjected to uncertainties in terms of in vitro to in vivo extrapolation, it is not ready for decision making, and needs further development. Still, the results indicate a concern for adverse effects on reproductive function in highly exposed boys, especially when considering additional exposure to data-poor chemicals and chemicals acting by other mechanisms of action.

Partitioning of hexachlorobenzene between human milk and blood lipid

In epidemiological studies on the toxic effects of prenatal exposure to hexachlorobenzene (HCB), researchers report HCB concentrations, either as wet-weight or per lipid weight basis, in matrices like breast milk, and maternal and cord blood. Conversion of exposures across matrices is needed for comparisons of concentrations and dose effect across cohorts. Using data from a birth cohort study in eastern Slovakia, we derived the maternal blood to cord blood HCB concentration ratio utilizing measured concentrations in 1027 paired maternal and cord blood samples, on a per-lipid basis. In addition to data from the Slovak study, the maternal milk to maternal serum ratio was summarized from 23 published studies on partitioning of HCB between human milk lipid and blood lipid. We identified two distinct groups of milk:blood ratios, those ≤0.45 and those ≥0.85. We assumed that using partition ratios ≤0.45 will underestimate HCB exposure estimates. Taking into account this precautionary measure, we suggest a conversion ratio of 1.21, which is the median of the 16 ratios identified in our literature review. We consider our estimate as conservative and providing appropriate safety in risk analysis.

Aldrin and Dieldrin Residues in Human Fat, Milk and Blood Serum Collected from Delhi

1 Aldrin and dieldrin residues were monitored in the fat, breast milk and blood serum from female residents of Delhi.

2 The average aldrin and dieldrin contents were 0.048 and 0.099 ppb in adipose tissue, 0.003 and 0.060 ppb in breast milk and 0.004 and 0.002 ppb in blood serum, respectively.

3 The older donors contained higher levels of aldrin and dieldrin in their adipose tissue.

4 Primagravidae contained more of these chemicals in their breast milk.

5 A positive correlation was observed between the aldrin concentration in adipose tissue and breast milk, and that in adipose tissue and blood serum. Similarly, a significant correlation was found between dieldrin in adipose tissue and blood serum.

6 The levels of aldrin and dieldrin were low in samples from residents of Delhi when compared to those in developed countries.

Analysis of organochlorine pesticide residues in human and cow's milk in the towns of Asendabo, Serbo and Jimma in South-Western Ethiopia

The level of some OCPs in human and cow milk collected from Asendabo, Serbo and Jimma in South-West Ethiopia were analyzed using GC-ECD. Results of the analysis indicated that all samples contained detectable quantities of p,p'-DDT and its metabolites, p,p-DDE and p,p-DDD, but none of the other OCPs analyzed. Mean levels of total DDT in the human and cow milk samples in the three areas were 12.68 and 0.389 μg g(-1) respectively. The distributions of p,p-DDT, p,p-DDE and p,p-DDD in the human milk samples from the three locations followed the same trend in which the proportion of p,p-DDT was the highest in all the three cases, comprising 55-71% of total DDT, followed by p,p-DDE, 26-39%, and the least, p,p-DDD of 2-5%. The mean ratio of DDT/DDE concentration for the three areas was calculated to be 2.01. This value was much higher than the values reported from other countries in earlier studies and indicates the existence of a higher quantity of DDT from a fresh input in the three study areas. The mean estimated daily intake of DDT by infants from mother's milk in the three locations was found to be 62.17 μg kg(-1) body weight, which is about three times higher than the acceptable daily intake set by WHO/FAO for total DDT, 20 μg kg(-1) of body weight. This alarmingly high daily intake value is a cause for concern, since children are highly susceptible to effects from such environmental contaminants. The study has revealed that people in the study areas are facing exposure to DDT from recent use. The observed contamination of mother's milk and the possible transfer of the contaminant from mother to child is an obvious risk associated with breast-feeding in the study areas and possibly in other parts of the country too.

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.

Environmental chemicals: from the environment to food, to breast milk, to the infant

Food is a source of exposure to many environmental chemicals found in human milk and other biological specimens. Ingestion of foods containing high amounts of animal fat is the main route of human exposure to lipophilic chemicals, such as persistent organic pollutants, which tend to bioaccumulate in the lipid compartment. Bioaccumulation results in increased exposure of these chemicals for humans, but particularly to breastfeeding infants, who are at the top of the food chain. The extent to which food contributes to a person's overall exposure depends on individual dietary habits and the concentrations of chemical residues in the food. These, in turn, are affected by (1) application methods, (2) properties and amounts of the chemical, and (3) preparation, handling, and the properties of the food. Once the food is ingested by the lactating woman, the chemical's pharmacokinetics and the transport mechanisms producing the movement of solutes across mammary alveolar cells determine the passage of chemicals from the blood to the milk. Thus, several factors affect the presence in human milk of environmental chemicals from dietary sources.

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.

Technical workshop on human milk surveillance and research on environmental chemicals in the United States: an overview

Interest in human milk research and monitoring for environmental chemicals is growing, and as studies of chemicals in human milk are initiated, it is of the utmost importance that these studies be conducted using harmonized methods. Due to numerous limitations in previous studies and the fact that few studies on environmental chemicals in human milk have been conducted in the United States, there is a growing need for a human milk sampling and analysis protocol in this country. The Technical Workshop on Human Milk Surveillance and Research on Environmental Chemicals in the United States was organized to develop state-of-the-science protocols describing the various aspects of such a program. An expert panel, comprised of specialists in the fields of pediatrics, family medicine, nursing, lactation, human milk sampling, analytical chemistry, epidemiology, pharmacology, toxicology, nutrition, and risk evaluation and communication, was assembled to participate in a 2-day workshop at the Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine. The expert panel was tasked with carefully describing and defining the components of well-conducted human milk surveillance and research studies, including participant selection, sample collection and analysis techniques, questionnaire development, chemical selection, and data reporting and interpretation, especially for use in the United States. The articles that follow this overview describe the results of the expert panel's deliberations on the components of human milk surveillance and research programs.

Residue levels of DDE and PCBs in the blood serum of women in the Port Said region of Egypt

An investigation was conducted to detect residues of 1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE) and polychlorinated biphenyls (PCBs) in blood serum samples collected from a cohort of fasting females attending the health insurance outpatient clinic at Port Said between July 1999 and July 2000. Females involved in the study included 43 females diagnosed with invasive adenocarcinoma of the breast, 21 female suffering benign breast disease, and 11 normal healthy females. Serum was separated and its contents of DDE and PCBs were extracted and determined, using gas chromatography, equipped with electron capture detector. Mean residues of DDE detected in the three examined groups of females were 41+/-5.2, 48+/-6.2 and 31+/-2.5ng/g for breast cancer cases, benign breast disease cases and controls, respectively, indicating some significantly less residues in blood serum of control females. While PCBs residues detected were 54+/-17, 59+/-23 and 61+/-21ng/g, for the three groups, respectively. Residues of DDE detected in all females alike in the present study are about 15 times higher than residues detected in Canada and The Netherlands.

Factors affecting organochlorine contaminant concentrations in milk and blood of northern fur seal (Callorhinus ursinus) dams and pups from St. George Island, Alaska

Levels of organochlorine contaminants in blood of northern fur seal (Callorhinus ursinus) pups and the blood and milk of their dams early in the lactation period are reported here. The contaminants included 15 selected individual polychlorinated biphenyl (PCB) congeners and DDT metabolites identified through high-performance liquid chromatography. Congeners CB-77, -81, -126, -169 and -189 were below the limits of detection in milk and blood samples analyzed. Congener-specific concentrations of PCBs in the blood of pups were compared based on the age of their dam (< or = 5 years or > 7 years). Pups of young (presumably primiparous) dams had significantly elevated levels of CBs-101, -118, -128, -138, -153/87, -170/194, and -180 than pups of older (multiparous) dams. Congeners CB-128 and -170/194 were detected in the blood of pups of young dams but not in the blood of pups of older dams nor in any of the dams blood. Additionally, pups had higher blood levels in seven of 10 detected PCB congeners as compared to the levels measured in milk when adjusted for lipid content. Levels of DDT metabolites and toxic equivalency quotients of dioxin-like congeners followed similar trends. Lipid-normalized concentrations of CB-101 and total PCBs were significantly higher in the blood of dams than in their milk. CB-128, -156, -157, -170/194, p,p'-DDT, o,p'-DDT, p,p'-DDD and o,p'-DDD were not detected in dam blood samples, but were detected in milk samples. Calculation of 'biomagnification factors' from milk to pup blood indicated a biomagnification of CB-101, -105, -118, -138, -153/87, and -180. Significant mean accumulation factors ranged from 1.5 to 7.5. Inter-annual differences in exposure levels and specific congener concentrations in both milk and blood were apparent. Northern fur seal pups, especially first-born, have a substantial exposure to organochlorine contaminants at a critical developmental stage.

Relationship of dietary intake to DDE residues in breast milk of nursing mothers in Beirut

Milk samples were collected from 32 nursing mothers living in the Beirut area, Lebanon. Dietary intakes of participating mothers were obtained from data of their diet histories, 24 h dietary recalls and food frequency questionnaires. Milk samples were screened for the presence of organochlorine pesticide residues and DDE levels were estimated using gas chromatographic techniques. The relationship between consumption of various food groups and DDE content of milk was investigated. A positive correlation was found between the consumption of either/or high fat meat, tuna fish and DDE levels in milk. Consumption of poultry products showed a weak correlation with DDE content of milk, whereas consumption of vegetable oils showed a negative correlation.

Behavioral impairment produced by low-level postnatal PCB exposure in monkeys

The preponderance of evidence in humans suggests that polychlorinated biphenyl (PCB)-induced behavioral deficits result from prenatal exposure rather than exposure through breast milk, although a recent study reported lower psychomotor scores during infancy associated with PCB concentration in breast milk. In the current study, monkeys were dosed from birth to 20 weeks of age with a PCB congener mixture representative of the PCBs found in human breast milk. Blood and fat levels of PCB-exposed monkeys at the end of the dosing period were within the range observed in the general human population, while levels in control monkeys were below averages observed in humans in industrialized countries. Behavioral assessment on a series of tasks was performed when monkeys were between 2.5 and 5.0 years of age. Robust deficits were observed on spatial delayed alternation, fixed interval, and differential reinforcement of low rate performance. No group differences were observed for the number of errors on a series of nonspatial and spatial discrimination reversal tasks. Behavioral deficits included retarded learning, perseverative behavior, and inability to inhibit inappropriate responding. These results have implications for the potential contribution of exposure to PCBs through breast milk to behavioral impairment.

Effects of postnatal exposure of monkeys to a PCB mixture on concurrent random interval-random interval and progressive ratio performance

Behavioral impairment as a consequence of PCB exposure beginning in utero has been reported in both humans and animals. The present study assessed the behavioral consequences of postnatal exposure to PCBs. Male monkeys (Macaca fascicularis) were dosed from birth to 20 weeks of age with 7.5 microg/kg/day of a PCB mixture representative of the PCBs typically found in human breast milk (eight monkeys) or vehicle (four monkeys). Blood PCB levels at 20 weeks of age were 0.30-0.37 ppb for control and 1.84-2.84 ppb for treated monkeys, and fat levels were 50-198 and 1694-3560 ppb for the two groups, respectively. Beginning at about 5.0 years of age, monkeys performed under concurrent schedules of reinforcement in which separate random intervals were in effect on two buttons independently. After steady-state performance was reached, the relative reinforcement ratio on the buttons was changed a total of four times, and performance both during transition and steady state was examined. There was no evidence for treatment-related differences in performance across the series of changes in schedule contingencies. The negative results failed to support the hypothesis that performance on an intermittent schedule, combined with the requirement for shifting response strategy, would prove particularly sensitive to postnatal PCB exposure. Following the concurrent schedules, monkeys were tested under a progressive ratio (PR) schedule preceded by a training procedure consisting of a within-session series of increasing fixed ratios. PCB-treated monkeys emitted more responses than controls over the first few sessions of the PR, which may be indicative of retarded acquisition of their steady-state PR performance. These results extend previous studies in these monkeys on the characterization of PCB-induced behavioral deficits.

Effect of postnatal exposure to a PCB mixture in monkeys on multiple fixed interval-fixed ratio performance

Behavioral impairment as a consequence of PCB exposure beginning in utero has been reported in both humans and animals. The present study assessed the behavioral consequences of postnatal exposure to PCBs. Male monkeys (Macaca fascicularis) were dosed from birth to 20 weeks of age with 7.5 microgram(s)/kg/day of a PCB mixture representative of the PCBs typically found in human breast milk (eight monkeys) or vehicle (four monkeys). At 4 years of age, performance under a multiple fixed interval (FI)-fixed ratio (FR) schedule of reinforcement was assessed. The FI component was more sensitive to disruption as a result of PCB exposure than was the FR component. PCB-exposed monkeys displayed shorter mean interresponse times (IRTs) than controls, particularly during the earlier sessions of the experiment. Similarly, the increase in pause time characteristic of the acquisition of typical FI performance emerged more slowly across sessions in the PCB-treated group. However, the number of short IRTs (less than 5 s) remained greater in the treated group compared to controls over the 48-session duration of the experiment. On the FR component, control monkeys decreases the mean pause time across sessions whereas the PCB-treated group did not; there were no differences between groups for absolute value of average IRT or pause time. The results of this study extend previous research in this cohort of monkeys, and provide further evidence that PCB exposure limited to the early postnatal period and resulting in environmentally relevant body burdens produces long-term behavioral effects.

Persistence of organochlorines in breast milk of women in Victoria, Australia

Existing information on the exposure of Australian infants to environmental contaminants through maternal milk is inadequate for assessing the safety of breast feeding. This study was undertaken to determine the extent of organochlorine (OC) contamination in the milk of mothers resident in Victoria, to monitor OC elimination by the nursing mother and to estimate the infant's daily intake of OCs from breast milk. Organochlorines were extracted from the lipophilic fraction of the breast milk samples and analysed by selected ion monitoring on a gas chromatograph-mass spectrometer (GC-MS). There was widespread contamination of milk with dichlorodiphenyltrichloroethane (p,p'-DDT) and its metabolite dichlorodiphenyldichloroethene, hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), oxychlordane and hexachlorocyclohexane, with p,p'-DDT and HCB being found in nearly all samples. Dieldrin and heptachlor epoxide were detected in 43 and 30% of samples respectively. PCBs were detected in 79% of samples and chlordane in 76%. A number of infants had daily intakes above the acceptable daily intake for total chlordane, total DDT, dieldrin, heptachlor epoxide and total PCBs. These findings have implications for strategies for the reduction of environmental contamination.

PCBs and other organochlorines in human tissue samples from the Welsh population: II--Milk

Polychlorinated biphenyl (PCB) and SigmaDDT (i.e. p,p'-DDT + p,p'-DDE = p,p'-DDD) concentrations were determined from the analysis of 115 Welsh breast milk samples collected in 1990 and 1991. Fifty PCB congeners were screened, of which 24 were identified in most samples. The PCB congener pattern was consistent between individual milk samples, with IUPAC congeners 28, 138, 153 and 180 being the most abundant and accounting for an average of 50% of the SigmaPCB concentrations determined. PCB concentrations varied between 2 and 70 ng g(-1) whole milk, were positively correlated with age, and negatively correlated with the total lactation period and with the percent lipid content of the milk. PCB pattern distributions differed between milk and adipose tissue samples. Human milk had a higher proportion of tri- (18 and 28), tetra- (44, 52 and 66) and pentachlorinated biphenyls (101) compared to human adipose tissue. SigmaDDT concentrations ranged from 0.3 to 71 ng g(-1) of whole milk, with p,p'-DDE contributing towards an average of 92% of the SigmaDDT concentrations. SigmaDDT levels were also positively correlated with age and negatively associated with the lactation period, though these correlations were rather weak. No significant differences in the SigmaPCB and SigmaDDT concentrations were noted between milk samples from donors living in rural and urban locations, or between the subjects' body weight, smoking habits or diet.

Temporal changes in some chlorinated hydrocarbon residue levels of Canadian breast milk and infant exposure

Between 1967 and 1986, five national surveys were carried out to determine organochlorine residues in Canadian breast milk. In these surveys the number of samples, their geographic sampling distribution and fat content changed over the years. In addition, the number of samples obtained from younger mothers decreased, while those from older mothers (31-40 years) increased. Total DDTs showed the most consistent decline of all declining residues, while PCBs only decreased after 1982. Levels of oxychlordane and trans-nonachlor remained constant. Ratios of p,p'-DDE/p,p'-DDT gradually increased from 3.1 to 10.0 over the same period of time. With few exceptions, regional trends in residue levels followed those observed for the whole country. Although the number of reported chemicals increased since 1967, this was not necessarily reflected in the total accumulated residues in breast milk. By 1986, the daily intakes of all compounds at 8 weeks of nursing were well below the established acceptable daily intakes.

Assessment of human exposure to chemical contaminants in foods

One of the most important factors in assessing risk to human health from potentially harmful chemicals in foods is the availability of good data on the exposure of the public to such substances. The means of acquiring these data generally involves monitoring programmes using appropriate sampling procedures and reliable analytical methods for measuring the compounds of concern in a variety of substrates. Two approaches are generally employed: a biological monitoring programme which measures substances in human fluids and tissues, and a food analysis monitoring programme, preferably a total diet study, wherein food is prepared for consumption prior to analysis. The choice of approach to use and chemicals to monitor depend on the situation within a particular country. The analysis of food has the advantage of short term impact since problems can be identified relatively quickly and control measures established. Biological monitoring on the other hand tends to indicate both accumulated and current exposure from all sources, including air, water and food. In Canada both approaches have been used for a number of years with major surveys of human milk and adipose tissue, and the total diet study, being conducted approximately every five years. Details of these programmes together with some of the pertinent findings are presented.

Abrogation of graft-versus-host reaction by dieldrin in mice

Sublethal exposure to the organochlorine pesticide, dieldrin, decreased the T-cell immune response in mice. Indeed, a transient inhibition of the mixed lymphocyte reactivity (MLR) was noted at 7 days after intraperitoneal exposure to 0.6 LD50 dieldrin. The present study was undertaken to further investigate the effects of dieldrin on the T-cell immune response, using the graft-versus-host reaction (GVHR) as a model, in order to assess T-cell subset efficiency. Lymphoid cells of A/J mice injected intraperitoneally 7 days earlier with 36 mg/kg body weight dieldrin were transferred into H-2-incompatible F1 hybrids. With this model, known to induce a marked GVHR, we have observed that dieldrin inhibited the potential of parental cells to induce a GVHR in hybrid mice. This effect could not be attributed to a direct cell cytotoxicity, nor to the modulation of major T-cell subsets as shown by thymic and peripheral T-cell subpopulation analysis. Collaboration processes between these cellular subsets seem to represent a potential site for the dieldrin-induced suppression.

Determinants of polychlorinated biphenyls (PCBs) in human milk

In a longitudinal pilot study on the course of the PCB concentration in human milk during six months of lactation, some important PCB determinants could be studied in 23 women and their infants. PCB values were within the range of those found in the literature. Pearson correlation coefficients were calculated to investigate the association of the mean PCB concentration over the first half year of lactation with maternal parameters, such as age, height, weight, previous lactation period, education, occupation, residence, smoking, drinking and dietary habits as well as the infant parameters gestational age, birthweight and weight gain in the first six months of life. Since the PCB concentration on fat basis and the fat content of the milk were strongly inversely related, statistical analyses were carried out both on fat and on milk basis. In univariate analyses the PCB concentration on fat basis was most strongly associated with pre- versus post-pregnancy weight gain, age and occupation. After multiple regression analysis PCB concentration on fat basis remained significantly associated with weight gain changes and remained borderline (p less than 0.10) significantly related with occupation. The pre-pregnancy Quetelet Index of the mother (height/weight) and the estimated PCB content of the diet (primarily fish) were strongly correlated with the PCB concentration on milk basis. Only the Quetelet Index remained significantly related after multiple regression analysis.

Organochlorine pesticides in human milk from different areas of Kenya 1983-1985

Residue levels of the chlorinated hydrocarbons p,p'-DDT (2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane), p,p'-DDE (2,2-bis(p-chlorophenyl)-1,1-dichloroethane), hexachlorobenzene (HCB), alpha-, beta-, and gamma-hexachlorocyclohexane (HCH), aldrin, dieldrin, and polychlorinated biphenyls (PCBs) were determined in human milk of Kenyan mothers living in different areas of Kenya. The main organochlorine contaminants found in all the milk samples analyzed were p,p'-DDT and p,p'-DDE. Great regional differences were found, and mean levels of sum DDT and DDT/DDE ratio ranged from 1.1 to 18.7 mg/kg milk fat and from 0.7 to 5.7, respectively. In general, relatively low residue levels of HCB, alpha-HCH, beta-HCH, aldrin, and dieldrin were detected in 59, 37, 27, 37, and 19%, respectively, of all the milk samples analyzed. Quantifiable residue levels of PCBs and alpha-HCH were not found. The results were examined in relation to differences in living conditions with regard to agricultural activities, dietary habits, and reported use of pesticides in the various sampling areas.

Polychlorinated biphenyls (PCBs) and dichlorodiphenyl dichloroethene (DDE) in human milk: effects of maternal factors and previous lactation

The authors measured polychlorinated biphenyls (PCBs) and dichlorodiphenyl dichloroethene (DDE) in maternal serum, cord blood, placenta, and serial samples of breast milk from 868 women. Almost all samples of breast milk showed detectable levels of both chemicals. Overall, values for DDE in this study are within the range of those found previously, whereas those for PCBs are somewhat higher. Possible causes of variation in levels were investigated. For DDE, older women, Black women, cigarette smokers, and women who consumed sport fish during pregnancy had higher levels; only age and race showed large effects. For PCBs, older women, women who regularly drink alcohol, and primiparae had higher levels. In addition, both chemicals showed modest variation across occupational groupings. Casual exposure to a PCB spill did not result in chemical levels different from background. In general, women have higher levels in their first lactation and in the earlier samples of a given lactation, and levels decline both with time spent breast-feeding and with number of children nursed. These striking declines are presumably a measure of exposure to the child.