Pesticide Residues in Mother’s Milk - Pesticides: Evaluation of Environmental Pollution - page 557

levels than those reported in other Asian developing countries like China, Indonesia, and
Cambodia but lower levels than those in Japan.
Hedley et al. (2010) studied the concentrations of 24 POPs in 10 pools of human milk
samples, collected at 2-6 weeks postpartum from 238 primiparous women living in Hong
Kong and south China, who participated in the 2002-2003 WHO exposure study. The
mean levels of α-HCH (mean 0.6 ng/g fat), β-HCH (940 ng/g fat), γ-HCH (1.8 ng/g fat), diel-
drin (1.0 ng/g fat), and HCB (21.8 ng/g fat) were much lower than the 1985 estimates. Mean
levels of α-HCH, γ-HCH, dieldrin, cis-heptachlor epoxide (0.7 ng/g fat), sum-chlordane
(6.1 ng/g fat), and trans-nonachlor (12.0 ng/g fat) were comparable to the international
median levels of the 15 other countries participating in the 2002-2003 WHO exposure
study. Continuous monitoring of POPs in human milk, especially β-HCH, is needed for
surveillance and interpretation of time trends and for linkage to strict enforcement of agri-
cultural regulations.
Residues of OCPs in human milk were monitored in central Taiwan between December
2000 and November 2001 by Chao et al. (2006). The OCPs were analyzed by GC/MS for 36
human milk samples from healthy women ranging between 20 and 36 years of age. The pre-
dominant OCPs were p,p′-DDE, p,p′-DDT, α-CHL, heptachlor epoxide, heptachlor, β-HCH,
and γ-HCH, with median levels of 228, 19, 7.4, 4.0, 2.3, 1.2, and 0.8 ng/g lipid, respectively.
The residues of OCPs in human milk samples from central Taiwan were comparable to
those described in the results obtained from Japan and were significantly lower than those
from investigations in Asian countries, including China, Thailand, Indonesia, and Vietnam.
Low DDE/DDT ratio (mean = 13.6, SD = 6.54) indicated that residual OCPs in human milk
mainly originated from past exposure. A notable decrease in DDT levels (ΣDDT = 333 ng/g
lipid) in human milk was found in this study compared to results from the previous two
decades (ΣDDT = 3595 ng/g lipid).
A survey was carried out on the levels of OCPs in human milk from Hmong hill tribes
in northern Thailand (Stuetz et al. 2001). DDT was detected in all samples with a median
and maximum level of 209 and 2012 ng of total DDT isomers per milliliter of milk, respec-
tively. The median and highest percentages of p,p′-DDT were 23.2 and 44.7%, respectively.
In 15 samples, heptachlor was detected in the metabolized form of heptachlor epoxide
with a median value of 4.4 ng/mL. The estimated daily intakes of DDT, heptachlor, and
heptachlor epoxide by the infants exceeded up to 20 times the acceptable daily intakes as
recommended by the FAO and WHO. In nine samples, HCB was detected with a median
value of 5.4 ng/mL; seven of the nine samples also had the highest values of DDT residues.
The γ-isomer of HCH was found only in one sample with 3.6 ng/mL. The mean sum-DDT
residues of 14.96 mg/kg milk fat as well as the estimated daily intake by the infants are
some of the highest reported values in the 1990s. The fact that the mother breast-feeds her
first child and the fact that she originally comes from a region where DDT is still in use as a
vector-control agent, as well as the former use of OCPs in agriculture, seem to be the main
factors for high DDT and other OCP residues in the mother's milk.
Among human breast milk samples from Asian developing countries, levels of DDTs in
Vietnam, China, Cambodia, and Malaysia; HCHs in China and India; and HCB in China
were relatively higher compared with other countries, suggesting again the recent use of
these organochlorine insecticides and fungicides and that these Asian developing countries
may be potential sources of these contaminants to the global environment. In Asian devel-
oping countries, further investigations on human exposure and temporal trends of POPs,
especially organochlorine insecticides, are needed to elucidate future pollution trends.
It has been previously reported that DDTs were predominant in environmental media,
biota, and foodstuff from these Asian developing countries (Tanabe and Kunisue 2007).