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1. Levels of organochlorine compounds
The obtained anamnestical data were related to the PCB levels in breast milk samples. It is well known that the primiparae milk generally shows significantly higher levels of persistent lipophilic substances, such as polychlorinated dibenzodioxins and dibenzofuranes, than the multiparaes. The applicability of this phenomenon for PCB was investigated. In the investigated group, 78 % of donors were primiparae, 13 o/Ð were secondiparae, and 9 % gave birth to 3 or more children. We have compared the mean PCB level between these groups of donors. The mean PCB level in the milk of women in their first lactation was 0,462 mg per kg, in the second lactation 0,210 mg/kg , and in the third lactation it was 0,243 mg/kg on fat basis. In the questionnaires, 35 % of donors claimed the reduction of their body weight during lactation. For this reason we have decided to compare the PCB levels in the milk of women which have reduced their body weight during lactation with those who have not. In the milk of the first group we have found the mean PCB level of 0,512 mg/kg and in the second group of 0,354 mg per kg on fat basis. The higher PCB Ievel in the milk of women reducing body weight in the time of lactation can be explained by increased mobilisation of fat deposits by weight reduction.
The source of mother milk contamination may be occupational, but in general, it is often assumed that meat consumption is an important factor. However, in our study the levels of organochlorine compounds did not differ significantly in the milk of lactovegetarians and nonvegetarians. This is in a good agreement with Jensen's thesis about more diffuse sources for contamination.
2. Acceptable Daily Intake
The methodology for determining Acceptable Daily Intake (ADI) is based primarily on dose-response experiments in test animals, or less commonly on well - documented exposures in humans. In the United States, the ADI approach developed by FDA was adapted to regulatory standard-setting in other areas of environmental health. The ADI methodology was also carried over into other regulatory sectors of EPA, including air quality standards and management of toxic wastes. However, the lack of a uniform guideline for ADI usage across the various regulatory offices of EPA lead to serious inconsistencies in the methodological approaches for ADI determination.
Daily intake of selected contaminants in comparison to their ADI values
(mg per kg.day) - median levels
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| 28 |
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| 52 |
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| 101 |
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| 138 |
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| 153 |
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| 180 |
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For PCB's calculation of daily intake in the table. was based either on the 6 indicator congeners individually, or on their sum in relation to an infant weighing 5 kg with a daily intake of 800 g of milk. The average daily intake based on the sum of indicator congeners was found to be 2,56 m g/kg.day and that from baby formulas at the level of 0.85 m g/kg.day. The average as well as median daily intake from mother milk exceeded the value of ADI which is 1 m g/kg.day. From this point of view bottle feeding would seem to be more advantageous, since the PCB levels are significantly lower in baby formulas. The frequency distribution shows that the daily intake coming from the majority (80 % ) of samples of baby formulas was lower than the Acceptable Daily Intake. On the other hand, the daily intake coming from breast milk shows a shifting towards higher levels. The daily intake below 1 m g/kg.day could be achieved only with 40 % of breast milk samples.
Fig. 1: Frequency distribution of daily PCB intake (in m
g/(kg per day))
3. Permissible Levels
As mentioned above, no complete system for the evaluation of the influence of chlorinated compounds on the sensitive infant's organisms has been presented to date. Therefore we decided to use an evaluation procedure based on a comparison of measured levels with the permissible levels (PL).
We have used a modificated approach according to the approach first published in the report Residues and Contaminants in Human Milk of the German Scientific Foundation. This approach is based on the value of No Observed Effect Levels (NOEL). Due to the uncertainties in interspecies extrapolation of the NOEL from test animals to humans, and because of the individual variability in human sensitivity to the effects of toxic agents, a safety factor must be introduced which reduces the NOEL value to a lower level of exposure that ensures the safety of most individuals in the human population. By convention, a cumulative safety factor of 100 is generally considered sufficient to account both for the uncertainties in interspecies extrapolation from animals to humans and for the intraspecies variations. Even before the ADI approach was formalised, the concept of a 100 - fold safety factor had been proposed as an "adequate margin of safety". The safety factor may be increased in some cases with an additional so called "children factor". The permissible level (PL) were calculated from the known NOEL, average body weight (BW) in the group under investigation, and the mean weight of the ingested milk fat (FW) per day using various safety factors (SF).
PL = (NOEL * BW * FV) / (SF * FW)
PL: Permissible Level ( mg per kg)
NOEL: No Observed Effect Level (mg/(kg.day) )
FV: factor relating to the weight of test animals and weight
of ingested feed ( rate: 0,05 dog: 0,02)
BF: Safety Factor
FW: weight of the ingested milk fat per day
The mean age of the infants in the studied group was 4 weeks. Their average body weight was 3.7 and they ingested daily in average 532 ccm of breast milk which corresponds to 0.018 kg of milk fat daily. With respect to this the permissible level may be calculated as follows:
PL =205.5 *(NOEL * FV) / SF
The permissible level depends on the NOEL for compound under study and on the safety factor as well. Higher safety factor used in the calculation of Permissible Level results in stricter i.e. lower PL.
Using a methodology derived principally from the above mentioned GSF Report, we have calculated the permissible levels for each compound with known NOEL using Safety Factor of 10, 100, and 1000 separately. The permissible levels obtained in this way were then compared to the determined real concentration.
NOEL.FV values used for calculation of permissible levels (mg/kg)
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| BHC | 0.006 |
| alpha-HCH | 0.5 |
| beta-HCH | 0.1 |
| gamma-HCH | 1.0 |
| DDT total | 0.5 |
| PCB | 0.1 |
| 1,2-Dichlorobenzene | 2.5 |
| Pentaehlorobenzene | 0.66 |
Comparison of permissible levels with real concentrations of monitored
substances in human milk ( mg per kg on fat basis)
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| 1,2-Dichlorobenzene |
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51.375 |
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| Pentachlorobezene |
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13.563 |
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| BHC |
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1.233 |
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| alpha - HCH |
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10.275 |
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| beta - HCH |
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2.055 |
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| gamma - HCH |
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20.555 |
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| DDT total |
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10.275 |
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| PCB |
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2.056 |
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Comparing the levels in the table three different kinds of interpretation may be used:
In the case of hexachlorobenzene as well as polychlorinated biphenyl’s, 10 % and 8 % of determined contamination levels are over the PL calculated using SF 10. The levels of these contaminants were considered unacceptable and we have consulted the paediatrician. On the other hand, the international NOEL value for polychlorinated biphenyl’s used in this study was not set for individual indicator congeners (Nrs. 28, 52,101,138,152,180) but it pertains generally on PCB. This may lead to many misunderstandings in the interpretation and comparison. When PCB's are released into the environment, the original isomer distribution pattern of any PCB's formulation may be altered probably due to a combination of circumstances e.g. different degradation pathways of individual congeners with different toxicological characteristics in animals. Thus, it is important to consider not only the total PCB's amount, but to characterise the distribution of individual PCB's congeners in each sample as well.