Effect of Changes in Excretion of Persistent Organochlorine Compounds with Human Breast Milk on Related Exposure of Breast-Fed Infants K. Czaja, J. K. Ludwicki, K. Go ´ralczyk, P. Strucin ´ski Department of Environmental Toxicology, National Institute of Hygiene, Chocimska 24, 00-791 Warsaw, Poland Received: 29 May 1998/Accepted: 6 December 1998 Abstract. This study was an attempt to identify if there are any trends in excretion of 1,2,3,4,5,6-hexachlorocyclohexane (HCH) isomers a-, b-, and g-, hexachlorobenzene (HCB), [1,1,1- trichloro-2,2-bis(4-chlorophenyl)ethane] (p,p8-DDT), [1,1- dichloro-2,2-bis(4-chlorophenyl)ethane] (p,p8-DDD), [1,1- dichloro-2,2-bis(4-chlorophenyl)ethylene] (p,p8-DDE), and polychlorinated biphenyls (PCBs) with human milk during lactation. The shortest lactation studied took 16 weeks, and the longest 84 weeks. Three hundred fifty-two milk samples, collected from each donor once a week, were examined. The analysis of the result showed individual differences in the excretion of the compounds. The findings from this study are not conclusive enough to claim that there are consistent trends showing a decrease or increase in the excretion of the com- pounds under examination. Thus, one cannot claim that the infants’ exposure to those compounds decreases or increases as breast-feeding continues. Mother’s milk is the most favorable means of nutrition for infants. It includes easily absorbable nutrients, perfectly tai- lored to the child’s needs. It also secures immunity bodies, appropriate temperature, and sterility (Goldman and Goldblum 1983; Goldman and Garza 1987; Neville et al. 1988). This opinion is also shared by the World Health Organization, which recommends breast feeding at all times unless the doctor prescribes otherwise (WHO 1994). Unfortunately, human breast milk is not devoid of com- pounds that may adversely affect the child’s health. These include persistent organochlorine compounds found in human breast milk all over the world. Occasionally, infants can be exposed to significant levels of these compounds (Jensen and Slorach 1991; Banerjee et al. 1997). The growing human organism is especially susceptible to toxic substances due to the not-yet-developed detoxification mechanisms and the tissue distribution for these compounds, which differs from that of grown-up individuals. Any distemper in the development of organs undergoing intensive growth in the early childhood can have long-term implications for the operation of the entire human organism. Persistent organochlorine compounds found in human breast milk have very high bioavailability and can be almost fully absorbed from the infants’ alimentary canal (McLachlam 1993; Abraham et al. 1994). The infant is exposed to the compounds in question through- out the breast-feeding period. The exposure may vary depend- ing on many factors, such as the mother’s age, number of deliveries and lactations, place of residence (Czaja et al. 1997a, 1997b), changes in the mother’s weight during lactation, or the means of nutrition (Jensen and Slorach 1991; Ramos et al. 1997). These factors have a direct impact on the exposure of infants to the organochlorine compounds from mothers’ milk. Understanding how such compounds are excreted throughout the lactation period can have significant implications for assessing the related exposure of breast-fed infants. The few papers on this topic remain inconclusive about trends indicating a decrease or increase in the concentration of the compounds examined during lactation (Noren 1983; Yakushiji et al. 1984; Greve and van Zoonen 1990; Skaare and Polder 1990; Jensen and Slorach 1991; Vaz et al. 1993; Duarte et al. 1994; Gonza ´lez et al. 1995). The inconclusiveness of the findings can be attributed, among others, to difficulties in ensuring the continu- ity of material for analysis and to the fact that milk samples were taken at different times after delivery. This research was an attempt to monitor the levels of a-, b-, and g-HCH, HCB, p,p8-DDT, p,p8-DDD, p,p8-DDE, and PCBs in the milk of eight mothers during lactation to determine if there are any changes in the infant’s exposure to these xenobiotics, knowing that such an infant takes in a given milk quantity regardless of the fat content in the milk. Correspondence to: K. Czaja Table 1. The donors’ profiles Number of Donor Age (years) Delivery Duration of Lactation (weeks) 1 31 Second 16 2 34 Third 21 3 29 First 46 4 32 Second 35 5 36 First 84 6 33 Second 75 7 27 First 42 8 29 Second 33 Arch. Environ. Contam. Toxicol. 36, 498–503 (1999) ARCHIVESOF E nvironmental Contamination and T oxicology r 1999 Springer-Verlag NewYork Inc.
Transcript
Effect of Changes in Excretion of Persistent Organochlorine Compoundswith Human Breast Milk on Related Exposure of Breast-Fed Infants
K. Czaja, J. K. Ludwicki, K. Go´ralczyk, P. Strucin´ski
Department of Environmental Toxicology, National Institute of Hygiene, Chocimska 24, 00-791 Warsaw, Poland
Received: 29 May 1998/Accepted: 6 December 1998
Abstract. This study was an attempt to identify if there are anytrends in excretion of 1,2,3,4,5,6-hexachlorocyclohexane (HCH)isomers a-, b-, and g-, hexachlorobenzene (HCB), [1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane] (p,p8-DDT), [1,1-dichloro-2,2-bis(4-chlorophenyl)ethane] (p,p8-DDD), [1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene] (p,p8-DDE), andpolychlorinated biphenyls (PCBs) with human milk duringlactation. The shortest lactation studied took 16 weeks, and thelongest 84 weeks. Three hundred fifty-two milk samples,collected from each donor once a week, were examined. Theanalysis of the result showed individual differences in theexcretion of the compounds. The findings from this study arenot conclusive enough to claim that there are consistent trendsshowing a decrease or increase in the excretion of the com-pounds under examination. Thus, one cannot claim that theinfants’ exposure to those compounds decreases or increases asbreast-feeding continues.
Mother’s milk is the most favorable means of nutrition forinfants. It includes easily absorbable nutrients, perfectly tai-lored to the child’s needs. It also secures immunity bodies,appropriate temperature, and sterility (Goldman and Goldblum1983; Goldman and Garza 1987; Nevilleet al. 1988). Thisopinion is also shared by the World Health Organization, whichrecommends breast feeding at all times unless the doctorprescribes otherwise (WHO 1994).
Unfortunately, human breast milk is not devoid of com-pounds that may adversely affect the child’s health. Theseinclude persistent organochlorine compounds found in humanbreast milk all over the world. Occasionally, infants can beexposed to significant levels of these compounds (Jensen andSlorach 1991; Banerjeeet al. 1997). The growing humanorganism is especially susceptible to toxic substances due to thenot-yet-developed detoxification mechanisms and the tissuedistribution for these compounds, which differs from that ofgrown-up individuals. Any distemper in the development oforgans undergoing intensive growth in the early childhood canhave long-term implications for the operation of the entire
human organism. Persistent organochlorine compounds foundin human breast milk have very high bioavailability and can bealmost fully absorbed from the infants’ alimentary canal(McLachlam 1993; Abrahamet al.1994).
The infant is exposed to the compounds in question through-out the breast-feeding period. The exposure may vary depend-ing on many factors, such as the mother’s age, number ofdeliveries and lactations, place of residence (Czajaet al.1997a,1997b), changes in the mother’s weight during lactation, or themeans of nutrition (Jensen and Slorach 1991; Ramoset al.1997). These factors have a direct impact on the exposure ofinfants to the organochlorine compounds from mothers’ milk.Understanding how such compounds are excreted throughoutthe lactation period can have significant implications forassessing the related exposure of breast-fed infants. The fewpapers on this topic remain inconclusive about trends indicatinga decrease or increase in the concentration of the compoundsexamined during lactation (Noren 1983; Yakushijiet al. 1984;Greve and van Zoonen 1990; Skaare and Polder 1990; Jensenand Slorach 1991; Vazet al.1993; Duarteet al.1994; Gonza´lezet al. 1995). The inconclusiveness of the findings can beattributed, among others, to difficulties in ensuring the continu-ity of material for analysis and to the fact that milk sampleswere taken at different times after delivery.
This research was an attempt to monitor the levels ofa-, b-,andg-HCH, HCB, p,p8-DDT, p,p8-DDD, p,p8-DDE, and PCBsin the milk of eight mothers during lactation to determine ifthere are any changes in the infant’s exposure to thesexenobiotics, knowing that such an infant takes in a given milkquantity regardless of the fat content in the milk.
Correspondence to:K. Czaja
Table 1. The donors’ profiles
Numberof Donor
Age(years) Delivery
Duration ofLactation (weeks)
1 31 Second 162 34 Third 213 29 First 464 32 Second 355 36 First 846 33 Second 757 27 First 428 29 Second 33
Arch. Environ. Contam. Toxicol. 36, 498–503 (1999) A R C H I V E S O F
EnvironmentalContaminationa n d Toxicologyr 1999 Springer-Verlag New York Inc.
Materials and Methods
The study material were samples of human breast milk measured forthe content ofa-, b-, and g-HCH, HCB, p,p8-DDT, p,p8-DDD,p,p8-DDE, and total PCB. Three hundred fifty-two (352) human milksamples out of eight women were studied. The samples were collectedin a uniform, strictly specified fashion so that the impact of thecollection approach was minimized:
1. Once a week—always on the same day of the week;2. At the same time;3. After 4 min of feeding, a child was brought to the other breast, while
approximately 20 ml of milk was collected from the first breast foranalysis.
The shortest lactation studied took 16 weeks, and the longest 84 weeks.The donors completed a detailed survey regarding (among other
things) their age, number of deliveries, health condition, diet, fluctua-tions in body weight, stress situations passed, and so on. All themothers came from the same region, Warsaw, where they had livedcontinuously for over 10 years. They would not smoke, with theirundifferentiated diet reflecting the same mix of fish, meat, and dairyproducts. All the donors and their children were healthy. No significantchanges in their body weight were observed during lactation. Thedonors’ profiles are shown in Table 1.
The milk samples were kept frozen at218°C until analysis. Afterdefrosting, the samples were deproteinized with acetone and extractedwith n-hexane; the resulting extract was cleaned up using concentratedsulphuric acid. The purified extracts were then analyzed by GLC-ECDfor organochlorine insecticides and HCB.
Following the detection of organochlorine insecticides and HCB,further analysis focused on quantitation of total PCBs. The hexaneextracts collected were concentrated to a 1-ml volume and dehydrochlo-rinated using a 2.5% potassium hydroxide solution in a 96% ethanol.Following extraction with n-hexane, the samples were oxidized usingan oxidizing agent (1.6 g of potassium dichromate, 18.5 ml of distilledwater, and 100 g of concentrated sulphuric acid). PCBs were deter-mined in the hexane layer by GLC-ECD.
The concentration of persistent organochlorine compounds in thehuman breast milk studied was expressed as mg/L of the milk. Theaverage concentrations of compounds were stated as the arithmeticmean of concentrations in all of the samples from each donor. Theevolution of concentrations in the compounds studied during thelactation in each woman is illustrated as a trend line. The resulting datawere analyzed using polynomial regression.
Quality Assurance
The research was based on a validated analytical method for which thefollowing parameters were reported: limit of detection, linearity,
precision, repeatability, and reproducibility. The abovementioned pa-rameters differ across the compounds and amount to: the limit ofdetection from 0.0002 to 0.0010 mg/L; the repeatability relativestandard deviation from 1% to 5%, and the reproducibility relativestandard deviation from 10% to 25%.
The laboratory uses the method as part of international proficiencytesting organized by the Food Analysis Performance AssessmentScheme by the U.K. Ministry of Agriculture, Food, and Fisheries. Inaddition, the certified reference materials are analyzed and ownfortified samples studied as part of a routine, internal analytical qualityassurance procedure.
Results
The average concentrations of persistent organochlorine com-pounds in human breast milk during lactation are shown inTable 2.
The analysis of the results indicated individual differences inthe excretion pattern of the compounds. The concentrations ofPCBs, p,p8-DDE, p,p8-DDT, HCB, andb-HCH varied signifi-cantly from one another, although some consistent patternscould also be found. For example, the concentrations tended tobe the highest in p,p8-DDE and lower, in descending order, inPCBs, p,p8-DDT, b-HCH, and HCB. The concentrations ofa-HCH,g-HCH, and p,p8-DDD in most samples did not exceedthe detection limit of the analytical method.
The evolution of the p,p8-DDE and total PCB concentrationsin the human breast milk during lactation is illustrated for eachwoman in Figures 1 and 2.
The samples collected during lactation showed significantvariances in compound concentrations. The evolution of thoseconcentrations was different for each of the women underexamination. However, no conclusive trends were reported thatwould indicate a decrease or increase in the excretion of thesecompounds during lactation.
Discussion
In the course of lactation, persistent organochlorine compoundsdissolved in milk fat are removed from a woman’s body. The fatcontent in human milk can vary from 1.2 to 12% (Jensen 1983).The fat concentration fluctuates highly throughout the lactationperiod, can vary from day to day or even during a singlefeeding. It must be noted that the concentrations of thesecompounds vary, too. This greatly hinders the estimate of theinfants’ intake of such compounds if the findings are translated
Table 2. The average concentrations of persistent organochlorine compounds in human milk during eight lactations observed (mg/L of milk6 SD)
Fig. 1. Trends in p,p8-DDE excretion with milk during lactation
500 K. Czajaet al.
Fig. 2. Trends in total PCB excretion with milk during lactation
501Persistent OC Compounds in Human Breast Milk
into the fat content in the milk, as the quantity of milk absorbedby an infant does not depend on the fat content of such milk(Bushet al.1985; Quinseyet al.1995). Therefore, in this study,we decided to express the results of our findings as concentra-tions in whole milk.
This study was an attempt to identify if organochlorinecompounds undergo significant changes in concentrations dur-ing lactation and how the infants are exposed to those com-pounds from the beginning of feeding to the end of lactation. Inaddition, the objective of the study was to test the validity ofcomparing earlier findings that are based on milk samplescollected at various times after delivery. In earlier studies(Czajaet al. 1997a), the average concentrations of persistentorganochlorine compounds in mature milk (collected startingfrom the third week of lactation, at the earliest) were comparedwith those in milk collected on the fourth day after delivery.Higher concentrations of PCBs andb-HCH were reported inmature milk. The levels of other compounds under examinationdid not vary significantly.
At the beginning of lactation, the so-called transitory milk issecreted for approximately 10 to 15 days.
According to Jensen and Slorach (1991), the concentrationsof organochlorine compounds in the colostrum tend to be lowerthan those at a later time. In mature milk, in turn, the levels ofcompounds under examination were reported to decrease aslactation continued (Duarte Davidsonet al. 1994; Jensen andSlorach 1991; Meset al.1984; Noren 1983; Skaare and Polder1990).
The findings from this study are not conclusive enough toclaim that there are consistent trends indicating a decrease orincrease in the excretion of the compounds under examination,even though one of the eight lactations was observed for as longas 84 weeks. The concentrations evolved differently for eachdonor. It is worth noting that on occasion subsequent milksamples collected once a week from the same woman differedmarkedly. This phenomenon was observed in all donors. Thiscan be accounted for by person-specific constraints in metabo-lism and the related excretion of organochlorine compoundsthat are freed from the mothers’ tissue deposits. The levels ofsuch compounds excreted with milk are reported to exceedsignificantly the daily intakes of those compounds by breast-feeding women (Jensen and Slorach 1991). Time-driven vari-ances in the concentrations of the compounds were also foundby Vazet al.(1993). Other researchers (Fooken and Butte 1987;Mes and Marchand 1987) did not report significant changes inthe levels of organochlorine compounds excreted during lacta-tion. Greve and van Zoonen (1990), in turn, found an increasein the levels of HCB,b-HCH, and PCBs, and a decrease inp,p8-DDE. However, these changes were marginal. Skaare andPolder (1990) reported a decrease in the PCBs and HCBconcentrations during lactation. Decreasing PCBs levels in thesamples examined during lactation was also reported byYakushijiet al.(1984). The findings of other authors (Gonza´lezet al.1995; Vazet al.1993) were inconclusive. Such divergentstudy findings from different authors are due to difficulties inensuring the continuity of material for analysis, the inability tomonitor lactation for a longer period, and variances in theconcentrations of the compounds examined in each woman.
The monitoring of organochlorine compounds excreted dur-ing lactation, as conducted in this study, is inconclusive inindicating general trends. Thus, one cannot claim that the
infant’s exposure to those compounds decreases or increases asbreast-feeding continues. Significant variances in the concentra-tions of these compounds during lactation are difficult toaccount for. They can be supposed, however, to stem fromperson-specific changes in metabolic or hormonal activity ineach donor. The lack of consistent trends that would indicate adecrease or increase in the excretion of the compounds makesvalid the comparison of study findings for mature milk samplescollected at different times after delivery. Therefore, there is noneed to identify the precise time at which the samples arecollected for examination. It must be kept in mind, though, thatthe findings from one sample may not reflect average concentra-tions for the entire lactation period. The relatively highconcentrations of compounds studied in human breast milk canbe accounted for by interrelations with the mothers’ tissuedeposits, rather than their daily intake with food (Jensen andSlorach 1991). Such is also the conclusion of our earlierresearch, which indicated that the concentrations of organochlo-rine compounds in the human adipose tissue follow the samedescending order as shown in this milk research (Ludwicki andGoralczyk 1994). It must be noted that in the light of the currentknowledge, the advantages of natural breast-feeding outweighthe potential risk of negative implications for a child, resultingfrom toxic compounds in human breast milk (WHO 1994).
Acknowledgments.The authors acknowledge the skillful technicalassistance of Mrs. Danuta Z˙ urek and Mrs. Graz˙yna Korzybska.
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