Pesticide Residues in Mother’s Milk - Pesticides: Evaluation of Environmental Pollution - page 549

17.5 Methods for Analysis of Organochlorine Pesticides in Mother's Milk
The literature describes several preparation methods to measure OCPs in mother's
milk ( Table 17.3 ). The standard method consists of three steps: extraction, cleanup, and
estimation. Gas chromatography (GC) with electron capture detection (ECD) has been
frequently used for the determination of OCPs, due to its high sensitivity, excellent sep-
aration efficiency, and speed of analysis. Extraction and enrichment steps are always
necessary prior to instrumental determination because of the large-scale dilution of con-
taminants in biological fluid samples. In addition, a cleanup step is necessary in order
to obtain clean solutions and to eliminate interfering compounds that limit the perfor-
mance of capillary columns and analysis. A crucial aspect, in current biological studies
at trace levels, is that the identity of analytical results must be categorically established
in order to avoid false-positive results. However, this technique cannot differentiate coe-
luted compounds.
Gas chromatography with mass spectrometry can resolve the problem of coelution and
avoid the misidentification of analytes if operated in the selected ion monitoring mode.
However, the concentrations of some OCPs in the general population are too low for quan-
tification by gas chromatography with an electron capture detector or gas chromatography
with mass spectrometry. Mass spectrometry allows quantification by isotope dilution. Gas
chromatography-high-resolution mass spectrometric analysis with an isotope dilution
method enables better identification and quantification than the other methods mentioned
here. To increase the sensitivity, the selected ion monitoring mode is also used during gas
chromatography-high-resolution mass spectrometric analysis.
17.6 Residues in Human Milk
Human breast milk could be used as a sort of indicator for understanding the biological
specificity in the accumulation of organochlorines in the tropical environment as well as
assessing the extent of environmental pollution. Monitoring of human milk is important
from two standpoints. First, pesticides tend to accumulate in the fat tissue and are rela-
tively easy to isolate and measure; second, their potential risks to infants, who rely solely
on mother's milk for a substantial period, need to be evaluated. Residues of these com-
pounds in human milk have been reported from different parts of the world and from
India.
17.6.1 Pesticide Residues in the General Population
Everybody has OCP residues in the body. Irrespective of the age, gender, socioeco-
nomic status, and country, these pesticides and their metabolites are detectable in
blood or tissue, although the exposure levels differ according to various factors. The
concentrations of these pesticides in human milk show regional differences because
of the regional variations in their use and the different times of discontinuation. The
concentration of organochlorine molecules in mother's milk mainly depends on their
accumulation in the maternal fatty tissue and their subsequent mobilization (Campoy
et al. 2001b).