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OBJECTIVE - To determine if exposure to disinfection by-products (DBPs) during gestation increases the risk of adverse birth outcomes, specifically term small for gestational age (SGA) birth, preterm birth (PTB), and very PTB (<32 weeks' gestation).
METHODS - We used weekly measurements total trihalomethanes (TTHMs), five haloacetic acids (HAA5), and total organic halides (TOX) collected from two distribution systems to evaluate the associations between DBP concentrations and term SGA, PTB, and very PTB using logistic regression.
RESULTS - We found no associations between DBPs and term-SGA. In the site with higher concentrations of bromine-containing DBPs, we found an association between TOX and PTB; this association was larger, though less precise, for very PTB.
CONCLUSIONS - Our results do not support an association between TTHMs or HAA5 and the birth outcomes investigated, but an association was found between increased TOX and PTB.
Concerns about the carcinogenic and endocrine-disrupting characteristics of organochlorine pesticides (OCPs) have led to a global ban on OCP use. However, OCPs persist in the environment for decades because of their long half-life. We evaluated serum levels of OCPs and their correlations with usual dietary intake and other lifestyle factors among 250 healthy women who participated as controls in the Shanghai Breast Cancer Study. Serum levels of hexachlorocyclohexane isomers (alpha-HCH, beta-HCH, gamma-HCH), dichloro-di-phenyl-trichloroethane (DDT) isomers (p,p'-DDE and p,p'-DDT), hexachlorobenzene (HCB), trans-nonachlor (TNC), and eight polychlorinated biphenyls (PCB) congeners (IUPAC no. 74, 118, 138, 153, 170, 180, 183, and 187) were measured. Lifestyle factors and usual dietary habits over the past 5 years were assessed through an in-person interview. With the exception of PCB, total OCP levels in our study population were significantly higher than those observed in other countries. Age, income, body mass index, waist-to-hip ratio, number of pregnancies, and/or total duration of breastfeeding were all significantly correlated with all types of OCPs. Of the 20 food groups evaluated, correlations with serum total OCPs were observed for eggs (r=0.13), fresh beans (r=-0.17), tea (r=0.14), and animal fat (r=0.18). Multiple regression analyses showed that age and animal fat intake were positively associated with serum total level OCPs, while leafy vegetable and fresh bean consumption was negatively associated with OCPs level. Our study suggests that dietary intake may be an important contributor of serum levels of OCPs in Chinese women.
The role of human cytochrome P-450 IIE1 (P-450 IIE1) in the oxidation of a number of suspect carcinogens was examined by using a variety of approaches, including (1) selective inhibition of catalytic activity in human liver microsomes by diethyldithiocarbamate, which was found to be a selective mechanism-based inactivator of P-450 IIE1, (2) correlation of rates of different catalytic activities with each other and with chlorzoxazone 6-hydroxylation, an indicator of P-450 IIE1, in human liver microsomes, (3) demonstration of catalytic activity in reconstituted systems containing purified human P-450 IIE1, and (4) immunoinhibition of catalytic activity in human liver microsomes with rabbit anti-human P-450 IIE1. The results collectively indicate that P-450 IIE1 is a major catalyst of the oxidation of benzene, styrene, CCl4, CHCl3, CH2Cl2, CH3Cl, CH3CCl3, 1,2-dichloropropane, ethylene dichloride, ethylene dibromide, vinyl chloride, vinyl bromide, acrylonitrile, vinyl carbamate, ethyl carbamate, and trichloroethylene. Levels of P-450 IIE1 can vary considerably among individual humans--the availability of chlorzoxazone as a noninvasive probe of human P-450 IIE1 and of disulfiram (oxidized diethyldithiocarbamate) as an inhibitor may facilitate discernment of the in vivo significance of human P-450 IIE1 as a factor in the bioactivation and detoxication of these cancer suspects. Further, many investigations with diethyldithiocarbamate, disulfiram, and ethanol in humans and experimental animals may be interpreted in light of mechanisms involving P-450 IIE1.