Genotoxicity of maleic hydrazide,acridine and DEHP in Allium cepa root cells performed by two different laboratories

The purpose of this paper was to compare the results of the Allium cepa chromosome aberration assay between two laboratories under the same test protocol and at the same time, use chemicals and onions obtained in their own homeland. For this study three chemicals were selected: di(2-ethylhexyl)phthalate (DEHP), maleic hydrazide, and acridine. Both laboratories found genotoxicity with a positive dose-response relationship for maleic hydrazide and acridine. However, for DEHP the results were quite different--one of the laboratories found this compound not genotoxic but the other found a positive response. Although the comparative study was inconclusive for DEHP, it was successful for the maleic hydrazide, acridine and also for the positive control (methyl methanesulfonate). Further studies need to be performed in the case of DEPH.     

An endogenous prostaglandin enhances environmental phthalate-induced apoptosis in bone marrow B cells: activation of distinct but overlapping pathways

Phthalate esters are ubiquitous environmental contaminants that are produced for a variety of common industrial and commercial purposes. We have shown that mono-(2-ethylhexyl) phthalate (MEHP), the toxic metabolite of di-(2-ethylhexyl) phthalate, induces bone marrow B cell apoptosis that is enhanced in the presence of the endogenous prostaglandin 15-deoxy-Delta((12, 14))-PGJ(2) (15d-PGJ(2)). Here, studies were performed to determine whether 15d-PGJ(2)-mediated enhancement of MEHP-induced apoptosis represents activation of an overlapping or complementary apoptosis pathway. MEHP and 15d-PGJ(2) induced significant apoptosis within 8 and 5 h, respectively, in a pro/pre-B cell line and acted cooperatively to induce apoptosis in primary pro-B cells. Apoptosis induced with each chemical was accompanied by activation of a combination of initiator caspases (caspases-2, -8, and -9) and executed by caspase-3. Apoptosis induced with MEHP and 15d-PGJ(2) was reduced in APAF1 null primary pro-B cells and accompanied by alteration of mitochondrial membranes, albeit with different kinetics, indicating an intrinsically activated apoptosis pathway. Significant Bax translocation to the mitochondria supports its role in initiating release of cytochrome c. Both chemicals induced Bid cleavage, a result consistent with a truncated Bid-mediated release of cytochrome c in an apoptosis amplification feedback loop; however, significantly more Bid was cleaved following 15d-PGJ(2) treatment, potentially differentiating the two pathways. Indeed, Bid cleavage and cytochrome c release following 15d-PGJ(2) but not MEHP treatment was profoundly inhibited by Z-VAD-FMK, suggesting that 15d-PGJ(2) activates apoptosis via two pathways, Bax mobilization and protease-dependent Bid cleavage. Thus, endogenous 15d-PGJ(2)-mediated enhancement of environmental chemical-induced apoptosis represents activation of an overlapping but distinct signaling pathway.     

Inhibition of gap-junctional intercellular communication between Chinese hamster lung fibroblasts by di(2-ethylhexyl) phthalate (DEHP) and trisodium nitrilotriacetate monohydrate (NTA)

Di(2-ethylhexyl)phthalate and trisodium nitrilotriacetate monohydrate, two apparently nongenotoxic carcinogens, were tested for effects on gap-junctional communication between Chinese hamster V79 lung fibroblasts. Both compounds inhibited gap-junctional communication in a concentration-dependent manner. The inhibiting effects of these chemicals on gap-junctional communication in vitro correlate with their tumor-promoting activity. Such results further support the hypothesis that inhibition of gap-junctional communication is an in vitro biomarker for some tumor-promoting chemicals.Abbreviations CAS Chemical Abstracts Service - DEHP di(2-ethylhexyl)phthalate - GJIC gap-junctional intercellular communication - NTA trisodium nitrilotriacetate monohydrate     

The present status of higher plant bioassays for the detection of environmental mutagens

Higher plants provide valuable genetic assay systems for screening and monitoring environmental pollutants. They are now recognized as excellent indicators of cytogenetic and mutagenic effects of environmental chemicals and are applicable for the detection of environmental mutagens both indoor and outdoor. Comparisons between plant and nonplant genetic assay systems indicate that higher plant genetic assays have a high sensitivity (i.e. few false negatives). Two assays which are considered ideal for in situ monitoring and testing of airborne and aqueous mutagenic agents are the Tradescantia stamen hair assay for mutations and the Tradescantia micronucleus assay for chromosome aberrations. Both assays can be used for in vivo and in vitro testing. Other higher plant gentoxicity assys which have a large number of genetic markers and/or data base and are also highly suitable for testing for genotoxic agents include Arabidopsis thaliana, Allium cepa, Hordeum vulgare, Vicia faba, and Zea mays. Since higher plant systems are now recognized as excellent indicators of the cytotoxic, cytogenetic, and mutagenic effects of environmental chemicals and have unique advantages for in situ monitoring and screening it is recommended that higher plant systems be accepted by regulatory authorities as an alternative first-tier assay system for the detection of possible genetic damage resulting from pollution or the use of environmental chemicals. The results from higher platn genetic assays could meke a significant contribution in protecting the public from agents that can cause mutation and cancer. The advantages possessed by higher plant genetic assays, which are inexpensive and easy to handle, make them ideal for use by scientists in developing countries.     

Identification of Thyroid Receptor Ant/Agonists in Water Sources Using Mass Balance Analysis and Monte Carlo Simulation

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.     

Contribution of environmental pollutants to male infertily: a working model of germ cell apoptosis induced by plasticizers

Bisphenol A [2,2-bis(4-hydroxyphenyl)propane] (BPA), 4-nonylphenol (NP) and di(2-ethylhexyl)phthalate (DEHP), and its metabolite mono-2-ethylhexyl phthalate (MEHP) are chemicals found in plastics, which act as endocrine disruptors (EDs) in animals, including human. EDs act like hormones in the endocrine system, and disrupt the physiologic function of endogenous hormones. Most people are exposed to different endocrine disruptors and concern has been raised about their true effect on reproductive organs. In the testis, they seem to preferentially attack developing testis during puberty rather than adult organs. However, the lack of information about the molecular mechanism, and the apparently controversial effect observed in different models has hampered the understanding of their effects on mammalian spermatogenesis. In this review, we critically discuss the available information regarding the effect of BPA, NP and DEHP/ MEHP upon mammalian spermatogenesis, a major target of EDs. Germ cell sloughing, disruption of the blood-testis-barrier and germ cell apoptosis are the most common effects reported in the available literature. We propose a model at the molecular level to explain the effects at the cellular level, mainly focused on germ cell apoptosis.     

Removing environmental organic pollutants with bioremediation and phytoremediation

Hazardous organic pollutants represent a threat to human, animal, and environmental health. If left unmanaged, these pollutants could cause concern. Many researchers have stepped up efforts to find more sustainable and cost-effective alternatives to using hazardous chemicals and treatments to remove existing harmful pollutants. Environmental biotechnology, such as bioremediation and phytoremediation, is a promising field that utilizes natural resources including microbes and plants to eliminate toxic organic contaminants. This technology offers an attractive alternative to other conventional remediation processes because of its relatively low cost and environmentally-friendly method. This review discusses current biological technologies for the removal of organic contaminants, including chlorinated hydrocarbons, focusing on their limitation and recent efforts to correct the drawbacks.     

Evaluation of “Classic” and Emerging Contaminants Resulting from the Application of Biosolids to Agricultural Lands: A Review

The presence of detectable amounts of contaminants in treated sewage sludge (concentrations μg/kg – mg/kg) has led to concerns that land applications of biosolids may result in an accumulation of contaminants in the soil and their subsequent translocation through the food chain. Despite advances in wastewater management (e.g., anaerobic, thermophilic, and mesophilic digestion), many compounds and their metabolites remain intact following treatment. This review looks at the main risk factors relating to the occurrence of “classic” (persistent organic pollutants [POPs]) and emerging pollutants (pharmaceuticals and personal care products) in biosolids. Relevant EU legislation and risk assessment strategies for the control of emerging contaminants are also considered. Organic pollutants regulated under the Stockholm Convention on POPs along with PPCPs were identified as contaminants of concern based on the risk factors: persistence, bioaccumulation, and toxicity (PBT). PPCPs were recognized as being of particular concern as their high transformation/removal rates are compensated by their continuous introduction into the environment. This study highlights the growing concern in relation to emerging contaminants in biosolids and highlights risk assessment strategies that can be used to characterize potential human/environmental risks.     

Chemical Contamination of Aquatic Organisms from an Urbanized River in the New York/New Jersey Harbor Estuary

The lower 6 miles of the tidal Passaic River, part of the New York/New Jersey (NY/NJ) Harbor Estuary system, are contaminated with a variety of organic and inorganic chemicals as a result of more than 150 years of heavy industrialization and urbanization. The River's ecology is substantially degraded due to habitat removal/alteration, and the organisms that reside in or utilize the River are exposed to and bioaccumulate chemicals from sediments and food web interactions. We quantify in this study the extent and magnitude of chemical contamination in several fish species (representing a range of trophic levels) and blue crab (Callinectes sapidus). In addition, the concentration of several contaminants of concern are compared to concentrations in similar organisms from other areas of the NY/NJ Harbor Estuary, as well as available tissue-based toxicological effects benchmarks that are reported in the literature. The results suggest that a variety of contaminants are present at elevated levels in each of the species collected from the River. Several contaminants, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), total DDT (2,2-bis[4-chlorophenyl]1,1-dichloroethene), copper, and mercury are present at average concentrations that exceed those from other waterways in the NY/NJ Harbor Estuary. However, the concentrations of contaminants in the River, with few exceptions do not exceed available toxic effects levels as reported in the literature for these or similar fish and crustaceans. This suggests that toxicological risks from bioaccumulative contaminants in the lower Passaic River are limited to select contaminants and species.     

Genotoxic evaluation of an industrial effluent from an oil refinery using plant and animal bioassays

Polycyclic aromatic hydrocarbons (PAHs) are genotoxic chemicals commonly found in effluents from oil refineries. Bioassays using plants and cells cultures can be employed for assessing environmental safety and potential genotoxicity. In this study, the genotoxic potential of an oil refinery effluent was analyzed by means of micronucleus (MN) testing of Alium cepa, which revealed no effect after 24 h of treatment. On the other hand, primary lesions in the DNA of rat (Rattus norvegicus) hepatoma cells (HTC) were observed through comet assaying after only 2 h of exposure. On considering the capacity to detect DNA damage of a different nature and of these cells to metabolize xenobiotics, we suggest the association of the two bioassays with these cell types, plant (Allium cepa) and mammal (HTC) cells, for more accurately assessing genotoxicity in environmental samples.     

Adenomatous polyposis coli as a predictor of environmental chemical‐induced transgenerational effects related to male infertility

Exposure to toxic environmental chemicals during pregnancy is a ubiquitous threat to health with potentially transgenerational consequences. However, the underlying mechanism of how transgenerational effects occur as part of environmental chemical exposure are not well understood. We investigated the potential molecular changes associated with dibutyl phthalate exposure that induced transgenerational effects, using a rat model. Through the analysis of the Gene Expression Omnibus database, we found some similar studies of environmental exposure induced transgenerational effects. Then, we analyzed one of the studies and our results to identify the adenomatous polyposis coli (APC) gene. This gene participated the most of the pathways and was upregulated in both studies. We used the miRWALK data set to predict the microRNAs which targeted the APC gene. We confirmed the miR‐30 family were significantly downregulated in F3 testis tissues and targeted the APC gene. In conclusion, the miR‐30 family/APC interaction is a potential mechanism for the transgenerational effects induced by the environmental chemical.     

Determination of trace endocrine disruptors in ultrapure water for laboratory use by the yeast estrogen screen (YES) and chemical analysis (GC/MS)

High purity water for endocrine disruptors (EDs) analysis in experimental tests is an indispensable requirement for the preparation of reagents and solutions employed in biological laboratories. Commercial ultrapure water may contain traces of organic compounds, which can interfere with in vitro bioassays carried out to detect the potential estrogen-like activity of pure compounds and complex mixtures. This paper shows that solid-phase extracts of different types of ultrapure water (UPW) purchased or produced in situ for laboratory analysis (mQ-UPW) may contain organic molecules able to antagonize the binding of E₂ to the human estrogen receptor α in the yeast estrogen screen (YES) assay. GC/MS analysis detected the presence of bis(2-ethylhexyl) phthalate (DEHP) (0.033 ppm ± 0.006) in mQ-UPW extracts. The dose–response curve of DEHP in the YES assay showed a relevant antagonist effect of this phthalate. Agreement between content of DEHP chemically detected in UPW extract and the magnitude of biological effects induced was pointed out. It would be appropriate that chemical analyses were complemented by biological tests to establish concentration limits for chemical contaminants in UPW that do not induce biological effects detectable in vitro. The yeast assay used in this study has previously proved to be a sensitive tool in assessing the presence of agonistic/antagonistic chemicals at the ng/l level in complex mixtures and may be successfully used to identify trace amounts of estrogenic/antiestrogenic chemicals, which can represent critical issues influencing the experimental results in environmental testing laboratories.     

Improvement of marine environmental pollution using eco-system: decomposition and recovery of endocrine disrupting chemicals by marine phyto- and zooplanktons

The decomposition and the recovery of endocrine disrupting chemicals (EDCs) using marine phytoplankton were demonstrated as one of the possible bioremediation methods. Bis(2-ethylhexyl)phthalate and bisphenol A tended to gradually accumulate into the plankton cells during incubation. Furthermore, the recovery of bisphenol A from the synthetic seawater was achieved using a marine pollutant collecting model (eco-system) that combined phyto- and zooplanktons.     

Distribution of Phthalate Esters in Sediments of Kaohsiung Harbor,Taiwan

The major objectives of this research are to study the species and concentration of phthalate esters (PAEs), an organic endocrine disruptor, in the sediments of Kaohsiung Harbor, Taiwan. Twenty monitoring stations were installed in the waterways of Kaohsiung Harbor to collect sediment samples for analyzing six species of PAEs. Results of laboratory analyses show that concentrations of ΣPAE₆ in the harbor sediment are between 0.40 and 34.8 mg/kg with an average of 5.02 mg/kg. Among all chemicals, di-(2-ethylhexyl) phthalate (DEHP) is the major species that constitutes 92% of all chemicals found in the sediment. Where the spatial distribution of the chemicals is concerned, all rivers (i.e., Love River, Canon River, and Salt River) show the highest concentrations near the mouth where they discharge into the harbor. This indicates that major sources of pollution originate from the upstream municipal and industrial wastewater discharges. Distributions of PAEs during both wet and dry seasons show that PAEs are more easily disbursed in the receiving sea water, leading to a wider range of chemical distribution, and hence most of the chemicals are accumulated in the harbor water channel. The assessment of ecological toxicity indicates that concentrations of the 88% DEHP found in the sediment are higher than environmental risk limits (ERLs), implying that the Kaohsiung Harbor sediments pose potential risks to the local ecological system. Hence, an effective PAE management and control strategy must be developed and implemented in order to improve the harbor sediment quality, and keep the harbor ecological environment free from the interference of chemicals that interrupt endocrine hormones.     

Sex Steroid Hormone Levels and Reproductive Development of Eight-Year-Old Children following In Utero and Environmental Exposure to Phthalates

In utero exposure to phthalates may adversely affect reproductive development in children due to the anti-androgenic properties of the pthalates. Accordingly, we aimed to determine the effects of in utero and environmental phthalate exposure on the reproductive development of eight-year-old children. We recruited 180 children in central Taiwan during November 2001 and followed them until August 2009 when all children became eight years old. Birth outcomes were collected. Bone age, hormone concentrations, and reproductive developmental stages were determined. Phthalate metabolite levels, including mono-2-ethylhexyl phthalate [MEHP], mono-n-butyl phthalate [MnBP], and mono-benzyl phthalate [MBzP], were assessed. No significant gender differences were found in in utero phthalate exposure. Maternal urinary levels of phthalate metabolites did not correlate significantly with birth outcomes, physical characteristics, and reproductive hormones of the eight-year-old children. Regarding the urinary phthalate metabolite levels of the eight-year-old children, MEHP correlated significantly with serum progesterone levels. MEHP levels in girls correlated significantly with serum progesterone levels. MnBP correlated significantly with serum FSH in all children. In girls, MnBP correlated with serum FSH, and MBzP correlated with serum progesterone and FSH levels. Urinary phthalate metabolite levels did not correlate with female developmental stages or the development of female reproductive organs. Phthalate metabolites did not correlate with the physical characteristics and reproductive hormones in boys. Therefore, environmental exposure to phthalates, as determined by urinary phthalate metabolite levels of eight-year-old children, may affect reproductive hormone levels in children, indicating that further studies on the environmental health effects of phthalates are warranted.     

A generalized physiologically-based toxicokinetic modeling system for chemical mixtures containing metals

Background  

Humans are routinely and concurrently exposed to multiple toxic chemicals, including various metals and organics, often at levels that can cause adverse and potentially synergistic effects. However, toxicokinetic modeling studies of exposures to these chemicals are typically performed on a single chemical basis. Furthermore, the attributes of available models for individual chemicals are commonly estimated specifically for the compound studied. As a result, the available models usually have parameters and even structures that are not consistent or compatible across the range of chemicals of concern. This fact precludes the systematic consideration of synergistic effects, and may also lead to inconsistencies in calculations of co-occurring exposures and corresponding risks. There is a need, therefore, for a consistent modeling framework that would allow the systematic study of cumulative risks from complex mixtures of contaminants.     

Degradation of ethanol plant by-products by <Emphasis Type="Italic">Exophiala lecanii-corni</Emphasis> and <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> in batch studies

By-product emissions from ethanol production facilities have become a public health concern. Many of these by-products are classified as hazardous air pollutants by the USEPA and current treatment methods, mainly thermal-oxidation, for these compounds are costly, energy intensive, and may produce other undesirable by-products. Degradation of these by-products by the fungi Exophiala lecanii-corni and Saccharomyces cerevisiae was explored. Ethanol plant by-products, focused on in this study, included formaldehyde, acetaldehyde, ethanol, methanol, glycerol, acetic acid, and lactic acid. Initial batch studies were conducted to determine degradation rates and whether the contaminants would be toxic to the fungi. These batch studies demonstrated that E. lecanii-corni and S. cerevisiae are able to utilize all but methanol and formaldehyde as sole carbon and energy sources for growth; however, both contaminants were utilized as secondary metabolites by cultures initially fed either ethanol or acetic acid. Growth studies also were conducted using two contaminants simultaneously to determine if the presence of one contaminant inhibited the degradation of another. Growth and contaminant utilization was observed in cultures fed two contaminants simultaneously.     

Zea mays assays of chemical/radiation genotoxicity for the study of environmental mutagens

From a literature survey, 86 chemicals are tabulated that have been evaluated in 121 assays for their clastogenic effects in Zea mays. Eighty-one of the 86 chemicals are reported as giving a positive reaction (i.e. causing chromosome aberrations). Of these, 36 are reported positive with a dose response. In addition, 32 assays have been recorded for 7 types of radiation, all of which reacted positively. The results of 126 assays with 63 chemicals and 12 types of radiation tested for the inductions of gene mutations are tabulated, as well as 63 chemicals and/or radiation in combined treatments. Three studies reported positive results for mutations on Zea mays seed sent on space flights. The Zea mays (2n=20) assay is a very good plant bioassay for assessing chromosome damage both in mitosis and meiosis and for somatic mutations induced by chemicals and radiations. The carcinogenicity and Salmonella assays correlate in all cases. The maize bioassay has been shown to be as sensitive and as specific an assay as other plant genotoxicity assays, such as Hordeum vulgare, Vicia faba, Crepis capillaris, Pisum sativum, Lycopersicon esculentum and Allium cepa and should be considered in further studies in assessing clastogenicity. Tests using Zea mays can be made for a spectrum of mutant phenotypes of which many are identifiable in young seedlings.     

Selenium Was a Time Bomb

At high dietary levels, selenium causes adverse effects in animals. Aquatic birds are among the more sensitive wildlife species, because their reproduction can be impaired when dietary selenium levels exceed about 4?µg/g (dry weight basis). Fish can also be adversely affected at similar dietary exposures. Conversely, low dietary levels of selenium (below about 0.1 to 0.5?µg/g) cause nutritional deficiencies in domestic animals, fish, and wildlife. Selenium became recognized as a significant environmental contaminant for wildlife in 1983, with the discovery of developmental abnormalities and excessive embryonic mortality in aquatic birds at Kesterson Reservoir, California. There are a number of environmental settings in which selenium warrants concern and must be considered carefully in relation to potential effects to fish and wildlife, and there may still be surprises in which it unexpectedly becomes a significant ecological issue. However, if selenium is included among the chemicals of potential ecological concern when ecological risk assessments are planned and conducted, there is enough information to thoroughly evaluate its environmental significance in much the same way as other contaminants. The main difference is that it is essential to have a good understanding of selenium's occurrence, complex biogeochemistry, and ecotoxicology to avoid serious errors.     

Measurement of eight urinary metabolites of di(2-ethylhexyl) phthalate as biomarkers for human exposure assessment.

Human metabolism of di(2-ethylhexyl) phthalate (DEHP) is complex and yields mono(2-ethylhexyl) phthalate (MEHP) and numerous oxidative metabolites. The oxidative metabolites, mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-carboxypentyl) phthalate (MECPP) and mono(2-carboxymethylhexyl) phthalate (MCMHP), have been considered to be better biomarkers for DEHP exposure assessment than MEHP because urinary levels of these metabolites are generally higher than MEHP, and their measurements are not subject to contamination. The urinary levels of the above metabolites, and of three other recently identified DEHP oxidative metabolites, mono(2-ethyl-3-carboxypropyl) phthalate (MECPrP), mono-2-(1-oxoethylhexyl) phthalate (MOEHP), and mono(2-ethyl-4-carboxybutyl) phthalate (MECBP), were measured in 129 adults. MECPP, MCMHP and MEHHP were present in all the samples analysed. MEHP and the other oxidative metabolites were detected less frequently: MEOHP (99%), MECBP (88%), MECPrP (84%), MEHP (83%) and MOEHP (77%). The levels of all DEHP metabolites were highly correlated (p<0.0001) with each other, confirming a common parent. The ? and ?-1 oxidative metabolites (MECPP, MCMHP, MEHHP and MEOHP) comprised 87.1% of all metabolites measured, and thus are most likely the best biomarkers for DEHP exposure assessment. The percentage of the unglucuronidated free form excreted in urine was higher for the ester linkage carboxylated DEHP metabolites compared with alcoholic and ketonic DEHP metabolites. The percentage of the unglucuronidated free form excreted in urine was higher for the DEHP metabolites with a carboxylated ester side-chain compared with alcoholic and ketonic metabolites. Further, differences were found between the DEHP metabolite profile between this adult population and that of six neonates exposed to high doses of DEHP through extensive medical treatment. In the neonates, MEHP represented 0.6% and MECPP 65.5% of the eight DEHP metabolites measured compared to 6.6% (MEHP) and 31.8% (MECPP) in the adults. Whether the observed differences reflect differences in route/duration of the exposure, age and/or health status of the individuals is presently unknown.