Environmental Engineering Reference
In-Depth Information
burden in lactating women (Behrooz et al. 2009). Zhou et al. (2011) found that no statisti-
cal difference was found in the residual level of DDTs in breast milk between rural and
urban areas in China. In China, with its rapid urbanization and industrialization in rural
areas, the difference in the level of environmental contamination between rural areas and
urban areas has narrowed gradually. The highest level of DDTs in breast milk was from
the Hubei rural area, followed by Shanghai urban area and Hubei urban area. The levels
of DDTs from Ningxia rural and urban areas and Heilongjiang rural and urban areas were
notably lower than those from other provinces. Concentrations of DDTs were significantly
higher in southern areas (761.7 ng/g lipid) than those in northern areas (434.1 ng/g lipid), if
the twelve provinces were divided into two groups from the Yangtze River (Changjiang),
indicating considerable exposure to DDTs in southern areas. No significant correlations
were found to total DDT in the function of age and parity in Brazilian human breast milk
(Azeredo et al. 2008). A recent study confirmed that point sources such as dicofol and
direct technical DDT usage from antifouling paint may have contributed DDTs to soil,
freshwater sediment, and freshwater fish species.
The mean level of HCHs in breast milk samples from urban areas was higher than those
from rural areas in China. Different patterns of food composition and food consumption
between urban and rural areas may be responsible for the variation of HCHs in breast milk
(Sudaryanto et al. 2006). A significant difference in the levels of HCHs in breast milk between
the southern part of the country and the northern part of the country was not observed.
Residual levels of HCHs in breast milk samples from the Hubei urban area were the
highest, followed by the Liaoning rural area and Shanghai urban area. The levels of HCHs
in breast milk samples from the Shanxi rural and urban areas were the lowest. The major
isomer of HCHs found in samples was β-HCH, with a mean value of 220.4 ng/g lipid that
accounted for 95.08% of the total HCH. The highest level of HCB in breast milk was from
the Liaoning rural area, followed by Hubei rural area and Hebei urban area. The lowest
level of HCB was from the Jiangxi urban area. A significant difference in the concentra-
tions of HCB and other OCPs between urban areas and rural areas as well as between the
southern part of the country and the northern part of the country were not observed.
It is known that adult females excrete lipophilic contaminants such as OCs during lacta-
tion, thus reducing the body burden of such contaminants. Minh et al. observed higher
concentrations of OCs in human breast milk of primiparous mothers as compared to mul-
tiparas mothers. In both groups, strong correlations between contaminant levels and age
were observed. However, only DDT levels of the multiparous group in Ho Chi Minh City
significantly correlated with age (Minh et al. 2004). Nevertheless, slopes of the regression
lines for DDTs and mother's age are quite similar regardless of the differences in groups
and areas. This result would probably be interpreted as an evidence of similar intake rates
of DDTs in Vietnamese mothers. In addition, it should be noted that other factors such
as the length of lactation, time of sampling during breast-feeding, etc. could also influence
the OC levels in women. Nevertheless, the available data from this study probably indicate
that parity and age play important roles in controlling the OC burden in humans.
Age and exposure to persistent contaminants usually generate a positive correlation.
Therefore, the lower the average age, the less the individual is likely to be exposed to
contaminants. No significant correlation was found in this study between age and POP
concentrations, neither were the differences between age classes statistically significant,
even though the 35-40 age class showed the highest concentrations of OC compounds on
average.
No significant relationship between the number of childbirths and concentrations of
HCB, HCH, dieldrin, and p,p′-DDT was found (Ennaceur et al. 2007). These results support
Search WWH ::
Custom Search