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Biomarkers of exposure to complex environmental mixtures

Maternal exposure to genotoxic chemicals may produce a variety of adverse birth
outcomes. Depending on the dose and duration of exposure, adverse birth outcomes can
range from premature or low-birth weight, to congenital abnormalities including neural
tube defects (NTDs). The research described in this dissertation focused on several rural
counties in Shanxi province, China. Shanxi has one of the highest rates of NTDs in the
world. In 2005, the incidence of NTDs in the study counties ranged from 8 to 24 cases
per 1,000 births. While some of these birth defects are likely to be related to nutrition, it
is also suggested that environmental factors play a significant role. One such factor
includes polycyclic aromatic hydrocarbon (PAH) exposure as a result of combustion of
coal for indoor heating and cooking. Human populations in Shanxi depend heavily on
coal as their main source of energy. This study determined the concentrations of PAHs
in house dust, venous blood and placenta of study participants. Dust was collected from
homes in the study site. Carcinogenic PAH levels in dust collected from kitchen floors
ranged from 12 to 2,000 µg/m2. The genotoxic potential of dust was confirmed by shortterm
bioassays. Median concentrations of total PAHs in placenta from children born
with NTDs were elevated compared to matched controls and appeared to be associated
with the risk of having a child with a NTD. Tobacco smoking was not associated with
elevated levels of PAH biomarkers in this study population. Levels of bulky DNA
adducts in placenta have also been quantified using 32P-postlabeling. Adduct levels do
not appear to be significantly different between cases and controls and were not
associated with deletions in enzymes GSTM1 or GSTT1. These data suggest that
children born with NTDs may be at increased risk due to exposure to genotoxic PAHs. Studies with a larger number of subjects are needed to further elucidate the relationship
between PAH exposure and adverse birth outcomes.

Identiferoai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-3284
Date15 May 2009
CreatorsNaufal, Ziad Sami
ContributorsDonnelly, Kirby C., McDonald, Thomas J.
Source SetsTexas A and M University
Languageen_US
Detected LanguageEnglish
TypeBook, Thesis, Electronic Dissertation, text
Formatelectronic, application/pdf, born digital

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