Rakesh Kanda

Wildlife and domesticated animals are exposed to a wide range of natural and synthetic chemicals throughout their life span. Many of these chemicals possess endocrine-disrupting properties which have the potential to disrupt reproductive and developmental process in certain animals. Organochlorine compounds, used as pesticides or in industrial and consumer products in the 1950s, were one of the earliest examples of synthetic endocrine-disrupting chemicals to be linked with adverse reproductive effects in animals. These legacy chemicals have since been restricted for use but continue to persist in the environment and threaten reproductive health of top predators, including porpoises, dolphins and whales. Newer chemicals, including some that were made to replace legacy chemicals and in use today, have been reported to also have endocrine-disrupting properties. These chemicals are manufactured for a wide range of uses, covering a broad range of chemically diverse substances, which include brominated flame retardants, plasticizers and pharmaceutically active ingredients among many other classes of chemicals. When present in the environment, they have been collectively termed emerging contaminants and have been linked with many adverse effects in animals, including impairments in reproduction and development. Whilst exposure to individual chemicals receives regular regulatory interest, there remains a particular concern about wildlife exposures to cocktails of endocrine-disrupting chemicals, which, combined with other stressors, may play a significant role in reproductive disorders that cannot be reproduced in laboratory experiments with single- or multi-chemical exposures. Regulation of chemicals, including restriction on the use of some chemicals, affords some protection to animals of the adverse effects of exposure to some EDCs, but there are presently no specific regulations on a holistic cross-government discharge limit for EDCs into the environment that would significantly reduce or eliminate animal exposure to EDCs.

In this study, it was hypothesised that UV-absorbing disinfection byproducts (DBPs) may include compounds, such as halofuranones, prioritized as candidates for explaining the increased risk of bladder cancer associated with the consumption of chlorinated water highlighted by epidemiological studies. Hence, UV spectroscopy was used as a screening method to identify conditions forming stable UV-absorbing DBPs from 10 phenolic precursors at various pH levels, chlorine and bromide doses. Subsequently, high performance liquid chromatography coupled to high resolution mass spectrometry (Orbitrap^TM) was used to elucidate the chemical formulas of 30 stable DBPs, 12 of which were tentatively identified as furan-like structures, including trichlorofuran-2-carboxylic acid, dichlorofuran-2-carboxylic acid, 3,4-dichlorofuran-2,5-dicarbaldehyde, 4-chloro-5-(dichloromethyl)furan-2,3-dione, 5-formyl-2-furancarboxylic acid, chloro-5-methyl-2-furancarboxylic acid, 2-acetylchlorofuran-5-one and bromo-2-furancarboxylic acid. Eleven of the furan-like structures are previously unknown as DBPs. A novel pathway was proposed to explain their formation, involving the opening of the oxidised phenolic ring followed by the formation of a 5-membered ring by intramolecular nucleophilic addition. Of the 12 furan-like DBPs identified, eight and three were respectively predicted to be mutagens and bladder carcinogens, using a quantitative structure-activity relationship theoretical model. The findings indicate the formation of furan-like DBPs from natural organic matter surrogates is more widespread than previously appreciated. Moreover, this class of DBPs may be toxicologically significant for the urinary bladder.

This study analysed the spatial and temporal occurrence of 29 disinfection by-products (DBPs) formed by chlorination and chloramination.

The developing foetus represents a highly sensitive period of exposure to endocrine disrupting compounds (EDCs). However, risk assessment of EDCs is hampered by the lack of data on direct in utero exposure. In this study we developed a robust analytical methodology for the identification of a wide range of known and unknown EDCs in full-term amniotic fluid (AF). First, a method for extraction and fractionation of a broad range of polar and non-polar EDCs was developed and validated. Maximal recoveries of reference compounds and minimal interference from the matrix were achieved with a combination of solid phase extraction and dispersive liquid/liquid extraction. Bioassay analysis using cell-based reporter gene assays revealed estrogenic, androgenic and dioxin-like activity in AF extract corresponding to 1.4 nmol EEQ/L, 76.6 pmol DHT-EQ/L and 10.1 pmol TEQ/L, respectively. Targeted analysis revealed 13 xenobiotics, phytoestrogens and endogenous hormones in the AF extract that partly contributed to the bioassay activity. Separation of the complex mixture of chemicals in the AF extract with reversed-phase chromatographic fractionation and subsequent bioassay analysis revealed activity in fractions over a wide range of polarity, indicating diverse (unidentified) substances with potential ED activity. The method developed here represents the first methodological step in an effect-directed analysis approach to identify unknown biologically active compounds in the foetal environment.

Wildlife is exposed to a diverse range of natural and man-made chemicals. Some environmental chemicals possess specific endocrine disrupting properties, which have the potential to disrupt reproductive and developmental process in certain animals. There is growing evidence that exposure to endocrine disrupting chemicals plays a key role in reproductive disorders in fish, amphibians, mammals, reptiles and invertebrates. This evidence comes from field-based observations and laboratory based exposure studies, which provide substantial evidence that environmental chemicals can cause adverse effects at environmentally relevant doses. There is particular concern about wildlife exposures to cocktails of biologically active chemicals, which combined with other stressors, may play an even greater role in reproductive disorders than can be reproduced in laboratory experiments. Regulation of chemicals affords some protection to animals of the adverse effects of exposure to legacy chemicals but there continues to be considerable debate on the regulation of emerging pollutants.

TAML activators enable homogeneous oxidation catalysis where the catalyst and substrate (S) are ultradilute (pM–low μM) and the oxidant is very dilute (high nM–low mM). Water contamination by exceptionally persistent micropollutants (MPs), including metaldehyde (Met), provides an ideal space for determining the characteristics and utilitarian limits of this ultradilute catalysis. The low MP concentrations decrease throughout catalysis with S oxidation (k_II) and catalyst inactivation (k_i) competing for the active catalyst. The percentage of substrate converted (%Cvn) can be increased by discovering methods to increase k_II/k_i. Here we show that NaClO extends catalyst lifetime to increase the Met turnover number (TON) 3-fold compared with H₂O₂, highlighting the importance of oxidant choice as a design tool in TAML systems. Met oxidation studies (pH 7, D₂O, 0.01 M phosphate, 25 °C) monitored by ¹H NMR spectroscopy show benign acetic acid as the only significant product. Analysis of TAML/NaClO treated Met solutions employing successive identical catalyst doses revealed that the processes can be modeled by the recently published relationship between the initial and final [S] (S₀ and S_∞, respectively), the initial [catalyst] (Fe_Tot) and k_II/k_i. Consequently, this study establishes that ΔS is proportional to S₀ and that the %Cvn is conserved across all catalyst doses in multicatalyst-dose processes because the rate of the k_II process depends on [S] while that of the k_i process does not. A general tool for determining the Fe_Tot required to effect a desired %Cvn is presented. Examination of the dependence of TON on k_II/k_i and Fe_Tot at a fixed S₀ indicates that for any TAML process employing Fe_Tot < 1 × 10^–6 M, small catalyst doses are not more efficient than one large dose.

Endocrine Disrupting Compounds pose a substantial risk to the aquatic environment. Ethinylestradiol (EE2) and estrone (E1) have recently been included in a watch list of environmental pollutants under the European Water Framework Directive. Municipal wastewater treatment plants are major contributors to the estrogenic potency of surface waters. Much of the estrogenic potency of wastewater treatment plant (WWTP) effluents can be attributed to the discharge of steroid estrogens including estradiol (E2), EE2 and E1 due to incomplete removal of these substances at the treatment plant. An evaluation of the efficacy of wastewater treatment processes requires the quantitative determination of individual substances most often undertaken using chemical analysis methods. Most frequently used methods include Gas Chromatography-Mass Spectrometry (GCMS/MS) or Liquid Chromatography-Mass Spectrometry (LCMS/MS) using multiple reaction monitoring (MRM). Although very useful for regulatory purposes, targeted chemical analysis can only provide data on the compounds (and specific metabolites) monitored. Ecotoxicology methods additionally ensure that any by-products produced or unknown estrogenic compounds present are also assessed via measurement of their biological activity. A number of in vitro bioassays including the Yeast Estrogen Screen (YES) are available to measure the estrogenic activity of wastewater samples. Chemical analysis in conjunction with in vivo and in vitro bioassays provides a useful toolbox for assessment of the efficacy and suitability of wastewater treatment processes with respect to estrogenic endocrine disrupting compounds. This paper utilizes a battery of chemical and ecotoxicology tests to assess conventional, advanced and emerging wastewater treatment processes in laboratory and field studies.