Bisphenols and phthalates in Australian wastewater: A statistical approach for estimating contributions from diffuse and point sources

Chemicals associated with plastics, such as bisphenols and phthalates, enter sewerage from both diffuse (domestic/commercial) and point (industrial) sources. In this study, we aimed to devise a conservative, statistical baseline to estimate contributions from these source types when sampling of specific sources is not possible. Population-normalised mass loads of two bisphenols and nine phthalates were estimated in wastewater samples from 22 sewage treatment plants (STPs) in 2019. Two multiday (10 and 7 day) pools were created for each STP. Baseline (diffuse) release thresholds were set at the mean of the first quartile (Q1) plus 10 times the standard deviation (STDV) of this quartile [Q1 mean + (10 x STDV)], with contributions over this considered to come from point sources. Chemicals with at least one population-normalised mass load more than three times their baseline were classified as point-source dominant and the remaining as diffuse-source dominant. Eleven of the twelve chemicals examined were detected above limits of quantification in all wastewater samples. Bisphenol A (BPA), bisphenol S (BPS), di-isononyl phthalate (DiNP) and di-methyl phthalate (DMP) were classified as point-source dominant chemicals. The total annual mass loads entering STPs across Australia were estimated to be 4.2 tonnes/year from diffuse sources and 4.5 tonnes/year from point sources for bisphenols, and 47 tonnes/year from diffuse sources and 5.9 tonnes/year from point sources for phthalates.

Genotoxic impact of di-n-butyl phthalate on DNA: A comparative study of three generations in the neuronal tissue of Wistar rats

Di-n-butyl phthalate (DBP), one of the plasticizers, is considered a ubiquitous environmental contaminant due to its widespread application in personal-care products and serves as a raw material in many industries for the generation of many plastic products. Several scientific investigations have shown that DBP caused embryotoxicity and cognitive impairments. However, there is less understanding of the genotoxic potential of DBP in neuronal tissue when exposure happens continuously for several generations. The present study was undertaken to investigate the impact of DBP on the nucleic acids of neuronal tissue in one-month-old rats by performing a comet assay and biochemical analyses. By oral gavage, the parental generation (F₀) was administered DBP (500 mg/kg/day) during gestation (GD6-20) and lactation, and exposures were continued for three consecutive generations until the pups were grown to one-month-old. The oxidative stress assessments carried out in discrete brain regions isolated from one-month-old rats (F₁-F₃) following DBP exposure indicated significant inhibition in the levels of antioxidant enzymes (superoxide dismutase and catalase) while oxidant status (malondialdehyde) was elevated significantly. The extent of DNA damage using the comet assay, as measured by the olive moment, tail DNA percentage and tail length, was greater in DBP-treated rats compared with the control group, but RNA/DNA content decreased significantly. The results of this study suggested a strong link between oxidative stress and genetic integrity in the neuronal tissue of rats exposed to DBP generationally. To summarise, DBP exposure during pregnancy caused oxidative stress, which resulted in genetic instability in specific discrete brain regions of the third generation.

Phthalate diversity in eggs and associations with oxidative stress in the European herring gull (Larus argentatus)

Phthalates are plastic-derived contaminants that are ubiquitous in natural environments and function as pro-oxidants. The extent to which phthalates bioaccumulate in wild animals and associations with oxidative stress are poorly understood. Here, we describe relationships between maternally-derived phthalates, lipid peroxidation (malondialdehyde, MDA) and the dietary antioxidant α-tocopherol in eggs of European herring gulls (Larus argentatus) in Cornwall, UK. Up to six phthalate parent compounds and four phthalate metabolites were detected. Egg concentrations of MDA were positively associated with dicyclohexyl phthalate (DCHP) and negatively associated with α-tocopherol, suggesting that DCHP is associated with oxidative stress in gulls. The consequences of phthalate exposure in ovo for offspring development warrants study.

Combining metabolomics with bioanalysis methods to investigate the potential toxicity of dihexyl phthalate

Dihexyl phthalate (DHP) is one of the most commonly used phthalate esters in various plastic and consumer products. Human are inevitably exposed to DHPs. Although several animal and human experiments have revealed that DHP can cause multiple toxicities, few studies have previously assessed the effects of DHP exposure by liquid chromatography mass spectrometry (LC-MS) analysis combine with molecular biology methods on human cells. Therefore, the purpose of our study was to investigate the effect of DHP on human cell metabolism by systems biology methods. In this study, U₂ OS cancer cells were treated with 10 μM DHP for metabolomics analysis and apoptosis analysis at indicate time. Metabolomic study of the metabolic changes caused by DHP in U₂ OS cells was performed for the first time using integrative liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS). To investigate the possible reason of fatty acids level altered by DHP, we measured some key fatty acid synthesis and oxidation-related enzyme expression levels by quantitative real-time PCR (Q-PCR). Apoptotic cells were analyzed by flow cytometry and apoptosis-related gene expressions were measured by Q-PCR. 2',7'-Dichlorofluorescein diacetate (DCFH-DA) staining was used to evaluate ROS content. Partial least squares-discriminate analysis (PLS-DA) clearly showed that significant differences in metabolic profiles were observed in U₂ OS cells exposed to DHP compared with controls. A total of 58 putative metabolites in electrospray ionization source (ESI) + mode and 32 putative metabolites in ESI-mode were detected, the majority of the differential metabolites being lipids and lipid-like molecules. Among them, the altered fatty acids level corresponded to expression levels of genes encoding enzymes related to fatty acids synthesis and oxidation. Moreover, DHP induced reactive oxygen species (ROS) accumulation, promoted cell apoptosis and inflammation, and resulted in a significant increase in apoptosis and inflammation-related gene expression levels compared with controls. In summary, our results suggested that metabolomics combined with molecular bioanalysis methods could be an efficient tool to assess toxic effects, which contribute to explore the possible cytotoxicity mechanisms of DHP, and provide a basis for further research.

Influence of in utero di-n-hexyl phthalate and di-cyclohexyl phthalate exposure on the endocrine glands and T3, T4, and TSH hormone levels of male and female rats: Postnatal outcomes

The present study was designed to evaluate the effects of di-n-hexyl phthalate (DHP) and di-cyclohexyl phthalate (DCHP) on endocrine organs in rats. Oil control, 20-, 100-, and 500 mg/kg dose groups were selected and administered to pregnant rats on gestational days 6-19 by oral gavage. The neonatal stages of rats continued until postnatal day 20 and the- juvenile stages of rats continued until postnatal day of 32. The rats were allowed to mature until the neonatal and juvenile stages and there after, they were divided into four groups corresponding to the treatment levels. Body and organ weights were recorded, serum was collected, and thyroid, pancreas, pituitary gland, and adrenal gland were removed. There was a decrease in body weights in the 20- and 500mg/kg DHP and in the 20-mg/kg DCHP dose groups in neonatal male rats. In contrast, for female rats, there was an increase in body weights in the 100-mg/kg DCHP dose group and there was a decrease in body weights in the 500-mg/kg DHP dose group. Body weights were increased at 20 and 500 mg/kg in the DHP-exposed juvenile male rats. Serum thyroid-stimulating hormone (TSH) levels were increased in neonatal male rats, while they were increased in the 100-mg/kg DHP group of neonatal and juvenile female rats. Serum triiodothyronine (T3) levels were increased at the high dose of DHP for neonatal male rats and at the low and high dose levels of DCHP for female rats. Serum thyroxine (T4) levels were increased in neonatal rats for DHP. Also, some histopathological changes were observed in the thyroid, pancreas, adrenal, and pituitary gland. In conclusion, it was shown that DHP and DCHP caused negative effects on T3, T4, and TSH hormone levels.

A strategy to validate a selection of human effect biomarkers using adverse outcome pathways: Proof of concept for phthalates and reproductive effects

Human biomonitoring measures the concentrations of environmental chemicals or their metabolites in body fluids or tissues. Complementing exposure biomarkers with mechanistically based effect biomarkers may further elucidate causal pathways between chemical exposure and adverse health outcomes. We combined information on effect biomarkers previously implemented in human observational studies with mechanisms of action reported in experimental studies and with information from published Adverse Outcome Pathways (AOPs), focusing on adverse reproductive effects of phthalate exposure. Phthalates constitute a group of chemicals that are ubiquitous in consumer products and have been related to a wide range of adverse health effects. As a result of a comprehensive literature search, we present an overview of effect biomarkers for reproductive toxicity that are substantiated by mechanistic information. The activation of several receptors, such as PPARα, PPARγ, and GR, may initiate events leading to impaired male and female fertility as well as other adverse effects of phthalate exposure. Therefore, these receptors appear as promising targets for the development of novel effect biomarkers. The proposed strategy connects the fields of epidemiology and toxicology and may strengthen the weight of evidence in observational studies that link chemical exposures to health outcomes.

Genotoxic, histologic, immunohistochemical, morphometric and hormonal effects of di-(2-ethylhexyl)-phthalate (DEHP) on reproductive systems in pre-pubertal male rats

Di-(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer and people are exposed to various amounts on a daily basis. This study was designed to evaluate the genotoxic, histologic, immunohistochemical, morphometric and hormonal effects of DEHP (100, 200 and 400 mg kg-1 per day DEHP) administered daily to rats by oral gavage for 28 days. The rats were divided into five groups including oil control, positive control (MMS) and treatment groups (100, 200 and 400 mg kg-1 per day DEHP). They were euthanized at the end of the experiment, organ and body weights were recorded and serum was collected for biochemical and hormone analysis. The genotoxic effect was measured in blood and sperm using the Comet assay. The testes, epididymis, prostate gland and seminal vesicle were collected and stained with hematoxylin and eosin for histopathologic analysis. Epithelial height, luminal and tubular diameters (μM) in seminiferous tubules were also measured. Moreover, the study revealed an increase in the DNA damage level in both blood lymphocytes and sperm. At the end of the experiment, the tail intensity showed a significant increase in the 100 mg kg-1 per day (p = 0.032), 200 mg kg-1 per day (p = 0.019) and 400 mg kg-1 per day (p = 0.012) dose groups compared to the control group in blood. Furthermore, testosterone was decreased in all treatment groups compared to the control group. Besides, DEHP caused a significant decrease in the leukocyte levels (p = 0.017) and hemoglobin content, as well as an increased mean cell volume (MCV) count (p = 0.029) in the 400 mg kg-1 per day group when compared to the control values. It is important to indicate that there were apoptotic cells seen in the lumen of testes in the 200 and 400 mg kg-1 per day dose groups using the Tunel method. Therefore, with this study, it has been illustrated that DEHP caused DNA damage in blood and sperm and concrete negative effects on the reproductive system in rats from the pre-pubertal period to the pubertal period. This is a unique study since there has not been any other study that presents the indicated level of DNA damage while considering the genotoxic, histologic, immunohistochemical, morphometric and hormonal effects of DEHP.

Assessing the concentration of phthalate esters (PAEs) and bisphenol A (BPA) and the genotoxic potential of treated wastewater (final effluent) in Saudi Arabia

Plasticizers such as phthalate esters (PAEs) and bisphenol A (BPA) are highly persistent organic pollutants that tend to bio-accumulate in humans through the soil-plant-animal food chain. Some studies have reported the potential carcinogenic and teratogenic effects in addition to their estrogenic activities. Water resources are scarce in Saudi Arabia, and several wastewater treatment plants (WTPs) have been constructed for agricultural and industrial use. This study was designed to: (1) measure the concentrations of BPA and six PAEs, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), bis (2-ethylhexyl) phthalate (DEHP) and dioctyl phthalate (DOP), in secondary- and tertiary-treated wastewater collected from five WTPs in three Saudi cities for four to five weeks and (2) test their potential genotoxicity. Three genotoxicological parameters were used: % tail DNA (%T), tail moment (TM) and percentage micronuclei (%MN). Both DBP and DEHP were detected in all treated wastewater samples. DMP, DEP, BBP, DOP, and BPA were found in 83.3, 84.2, 79, 73.7 and 97.4% of the samples, respectively. The levels of DMP (p<0.001), DOP (p<0.001) and BPA (p=0.001) were higher in tertiary- treated wastewater than secondary-treated wastewater, perhaps due to the influence of the molecular weight and polarity of the chemicals. Both weekly sampling frequency and WTP locations significantly affected the variability in our data. Treated wastewater from Wadi Al-Araj was able to induce DNA damage (%T and TM) in human lymphoblastoid TK6 cells that was statistically higher than wastewater from all other WTPs and in untreated TK6 cells (negative control). %MN in samples from both Wadi Al-Araj and Manfouah did not differ statistically but was significantly higher than in the untreated TK6 cells. This study also showed that the samples of tertiary-treated wastewater had a higher genotoxicological potential to induce DNA damage than the samples of secondary-treated wastewater. BPA and some PAEs in the treated wastewater might have the potential to induce genetic damage, despite their low levels. Genotoxicity, however, may also have been due to the presence of other contaminants. Our preliminary findings should be of concern to Saudi agriculture because long-term irrigation with treated wastewater could lead to the accumulation of PAEs and BPA in the soil and ultimately reach the human and animal food chain. WTPs need to remove pollutants more efficiently. Until then, a cautious use of treated wastewater for irrigation is recommended to avoid serious health impacts on local populations.

Influence of in utero di-n-hexyl phthalate and dicyclohexyl phthalate on fetal testicular development in rats

This study investigated the effects of di-n-hexyl phthalate (DHP) and dicyclohexyl phthalate (DCHP) on male reproductive development in utero. Pregnant rats were exposed to DHP and DCHP at doses of 0 (vehicle), 20, 100 and 500mg/kg/day, by gavage, on gestational days (GD) 6-19. A significant decrease in the anogenital distance (AGD) of male fetuses was observed at all doses of DHP and DCHP. The AGD/cube root of body weight ratio in male fetuses was also significantly reduced compared to control group. The litters with resorption, percentage of resorptions and inhibin B levels increased in treatment groups. Moreover, testosterone and MIS/AMH levels in all treatment groups decreased. Although FSH and inhibin B levels of male pups exposed to DHP and DCHP increased, FSH/inhibin B ratio decreased in treatment groups. Reduced testosterone production in response to DHP and DCHP exposure appeared to be related to changes in testosterone metabolism, as shown by decreased 3β-HSD immunoexpression. The percentages of large Leydig clusters increased after exposure to DHP and DCHP in utero. Histopathological examination of the testis on GD20 revealed changes at all doses. Relative integrated immunodensities of 3β-HSD, MIS/AMH, PCNA and AR decreased after DHP and DCHP exposures. Altered fetal Sertoli cell development and function may be caused by disrupted PMC function revealed by reduced AR production in these cells in treatment groups.

Cytotoxicity and genotoxicity of butyl cyclohexyl phthalate

Butyl cyclohexyl phthalate (BCP) is frequently used in personal care products, medical and household applications. The aim of this study is therefore to evaluate possible cytotoxicity and genotoxicity of BCP using in vitro and in vivo assays. The in vitro cytotoxic effect of BCP was investigated on mouse fibroblastic cell line (L929 cells) by MTT assay. The result showed that BCP inhibits cell proliferation in a concentration-dependent manner (IC50 value = 0.29 µg/mL). For genotoxicity assessment, tested concentrations of BCP demonstrated mutagenic activity in the presence of S9 mix with the Salmonella strain TA100 in the Ames test. Results showed that BCP is a secondary mutagenic substance even in low concentrations. The data obtained from 28-days repeated toxicity tests on mice revealed that BCP caused abnormalities of chromosome number, in a dose-dependent manner. Additionally, DNA damage, particularly DNA strand breaks, was assessed by Comet assay. The test result shows that BCP seemed to have genotoxic potential at a high level of exposure.

Genotoxicity of phthalates

Many of the environmental, occupational and industrial chemicals are able to generate reactive oxygen species (ROS) and cause oxidative stress. ROS may lead to genotoxicity, which is suggested to contribute to the pathophysiology of many human diseases, including inflammatory diseases and cancer. Phthalates are ubiquitous environmental chemicals and are well-known peroxisome proliferators (PPs) and endocrine disruptors. Several in vivo and in vitro studies have been conducted concerning the carcinogenic and mutagenic effects of phthalates. Di(2-ethylhexyl)-phthalate (DEHP) and several other phthalates are shown to be hepatocarcinogenic in rodents. The underlying factor in the hepatocarcinogenesis is suggested to be their ability to generate ROS and cause genotoxicity. Several methods, including chromosomal aberration test, Ames test, micronucleus assay and hypoxanthine guanine phosphoribosyl transferase (HPRT) mutation test and Comet assay, have been used to determine genotoxic properties of phthalates. Comet assay has been an important tool in the measurement of the genotoxic potential of many chemicals, including phthalates. In this review, we will mainly focus on the studies, which were conducted on the DNA damage caused by different phthalate esters and protection studies against the genotoxicity of these chemicals.