Dibutyl phthalate contributes to the thyroid receptor antagonistic activity in drinking water processes.
ABSTRACT It has long been recognized that thyroid hormone (TH) is essential for normal brain development in both humans and animals, and there is growing evidence that environmental chemicals can disrupt the thyroid system. In the present work, we used a two-hybrid yeast assay to screen for agonistic or antagonistic thyroid receptor (TR) mediated effects in drinking waters. We found no TR agonistic, but TR antagonistic activities in all samples from the drinking water processes. The TR antagonistic activities in organic extracts of water samples were then calibrated regarding to a known TR-inhibitor, NH3, and were expressed as the NH3 equivalents (TEQbio). The observed TEQbio in waters ranged from 180.8+/-24.8 to 280.2+/-48.2 microg/L NH3. To identify the specific compounds responsible for TR disrupting activities, the concentrations of potentially thyroid-disrupting chemicals including organochlorine pesticides (OCPs), phenols, and phthalates in organic extracts were quantitatively determined and their toxic equivalents with respect to NH3 (TEQcal) were estimated from their concentration-dependent relationships, respectively, using the same set of bioassays. Based on the TEQ approach, it was revealed that dibutyl phthalate (DBP) accounted for 53.7+/-8.2% to 105.5+/-16.7% of TEQbio. There was no effective removal of these potential thyroid disrupting substances throughout drinking water treatment processes.
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ABSTRACT: The association between spray paint exposure and bone remodeling received little attention despite the high usage of spray paints in automobile industries, steel furniture workshops etc. The present study was aimed at investigating the level of serum markers of bone formation in spray painters. The spray painting subjects were selected from automobile body repair workshops in Chennai region of TamilNadu which constitutes 30% of India's automobile industry. All the study subjects, exposed to spray paint were working in a workshop without standard spraying room and did not wore any aerosol removing respirator. The controls were selected from random population irrespective of occupation. Data relevant to the socioeconomic features and personal history was collected using a questionnaire. The current study included 50 spray painters and 25 control subjects of same age group. We examined the level of serum calcium, serum phosphorus, serum differentiation markers of bone such as alkaline phosphatase (bone specific) and serum osteocalcin in which these levels were found to be high in serum of spray painters. The current study concludes dysregulation in bone remodeling of spray painters exposed to chronic solvents and paint pigments.Indian journal of occupational and environmental medicine 05/2012; 16(2):84-7.
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ABSTRACT: Bio-equivalents (bio-EQs, e.g., 17β-estradiol or dioxin equivalents) are commonly employed to quantify the in vitro effects of complex human or environmental samples. However, there is no generally accepted data analysis strategy for estimating and reporting bio-EQs. Therefore, the aims of the present study are to (I) identify common mathematical models for the derivation of bio-EQs from the literature, (II) assess the ability of those models to correctly predict bio-EQs, and (III) propose measures to reduce uncertainty in their calculation and reporting. We compiled a database of 234 publications that report bio-EQs. From that, we extracted 3 data analysis strategies commonly used to estimate bio-EQs. These models are based on linear or nonlinear interpolation, and the comparison of effect concentrations (ECx ). To assess their accuracy, we employed simulated data sets in different scenarios. The results indicate that all models lead to a considerable misestimation of bio-EQs if certain mathematical assumptions (e.g., goodness of fit, parallelism of dose-response curves) are violated. However, nonlinear interpolation is most suitable to predict bio-EQs from single point estimates. Regardless the model, subsequent linear extrapolation of bio-EQs generates additional inaccuracy if the prerequisite of parallel dose-response curves is not met. Taken together, our evaluation indicates that data analysis introduces a considerable uncertainty in the derived bio-EQs. To improve accuracy and transparency of bio-EQs, we propose a novel data analysis strategy and a checklist on reporting Minimum Information about Bio-equivalent ESTimates (MIBEST). Environ Toxicol Chem © 2013 SETAC.Environmental Toxicology and Chemistry 04/2013; · 2.62 Impact Factor
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ABSTRACT: Some synthetic chemicals, which have been shown to disrupt thyroid hormone (TH) function, have been detected in surface waters and people have the potential to be exposed through water-drinking. Here, the presence of thyroid-active chemicals and their toxic potential in drinking water sources in Yangtze River Delta were investigated by use of instrumental analysis combined with cell-based reporter gene assay. A novel approach was developed to use Monte Carlo simulation, for evaluation of the potential risks of measured concentrations of TH agonists and antagonists and to determine the major contributors to observed thyroid receptor (TR) antagonist potency. None of the extracts exhibited TR agonist potency, while 12 of 14 water samples exhibited TR antagonistic potency. The most probable observed antagonist equivalents ranged from 1.4 to 5.6 µg di-n-butyl phthalate (DNBP)/L, which posed potential risk in water sources. Based on Monte Carlo simulation related mass balance analysis, DNBP accounted for 64.4% for the entire observed antagonist toxic unit in water sources, while diisobutyl phthalate (DIBP), di-n-octyl phthalate (DNOP) and di-2-ethylhexyl phthalate (DEHP) also contributed. The most probable observed equivalent and most probable relative potency (REP) derived from Monte Carlo simulation is useful for potency comparison and responsible chemicals screening.PLoS ONE 01/2013; 8(10):e73883. · 3.73 Impact Factor