Residues in human milk

Substances not naturally occurring in human milk are not only undesirably from the hygienic point of view, but are of particular importance, because oftheir potential health significance for nursed babies. Residues of xenobiotics in human milk normally result from the burden or contamination of the maternal organism. Hence, from the various routes of exposure the uptake of substances by the mothers may occur via skin, inhalation and by oral ingestion. Chemicals are transferred from the maternal organism into the milk according to their partitioning coefficients between maternal serum and milk and may even accumulate due to possible active secretion. Table 1 lists the most important groups ofchemicals, which can be detected in human milk. The exposure of the mothers to part of these substances is more or less avoidable. However, the intake of other groups of chemicals is practically unavoidable, because oftheir ubiquitous occurrence and/or entrance into the food chain.

Table 1. Possible residues in human milk_

medicinal drugs mycotoxins cosmetics/fragrances heavy metals stimulants (alcohol, caffeine, nicotine) nitrate, nitrite, nitrosamines polycyclic aromatic hydrocarbons (PAH) volatile organochlorine substances (solvents) persistent organochlorine substances polybrominated biphenyls (flame retardants)

Of greatest concern are so-called persistent chemicals. Among these are chlorinated or halogenated aromatic hydrocarbons ( Figure 1), which, due to their high stability and low biodegradation persist in the environment and hence can be detected ubiquitously.

OC-Pesticides Biphenyls(PCB)Dioxins(PCDD) Furans(PCDF)

OC-Pesticides Biphenyls(PCB)Dioxins(PCDD) Furans(PCDF)

dt/dde agricultural technical use use no specific use, unintended by-products

Figure 1. Persistent organochlorine substances

To these belong organochlorine pesticides (OCP), which had been used in agriculture, and polychlorinated biphenyls (PCB), which had been widely used in various industrial applications. They have been regulated in many of the industrialised countries during the past decades, which means that commercial production and use has been discontinued or banned. Further, polychlorinated dibenzodioxins and dibenzofurans (PCDD/PCDF) belong to this group of chemicals. They have never been intentionally produced, but are generated predominantly by incineration and other thermic processes and as by-products during fabrication ofspecial chemical compounds. OCPs and PCBs - by means of certain indicator-congeners - can be determined by routine analytical methods, whereas the determination of PCDD/PCDF requires much more demanding analytical methods, which were not developed before the mid 80ties, when PCDD/PCDF were detected in human milk for the first time.

From the various sources of exposure (soil, water, air) the intake via food - predominantly from fat of animals' origin - contributes more than 95% to the human exposure and burden of such contaminants. Due to their persistence, low biodegradability and lipophilicity these substances accumulate in the food chain (Figure 2). Human milk can be conceived as a bioindicator, for the extent and time course ofhuman contamination.

Human Milk Feeding The Animals
Figure 2. Pathwaysfor human exposure and burden to PCBs and dioxins
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