Carla Ng | University of Pittsburgh (original) (raw)

Papers by Carla Ng

Environment International, 2022

Per- and polyfluoroalkyl substances (PFAS) accumulation and elimination in both wildlife and huma... more Per- and polyfluoroalkyl substances (PFAS) accumulation and elimination in both wildlife and humans is largely attributed to PFAS interactions with proteins, including but not limited to organic anion transporters (OATs), fatty acid binding proteins (FABPs), and serum proteins such as albumin. In wildlife, changes in the biotic and abiotic environment (e.g. salinity, temperature, reproductive stage, and health status) often lead to dynamic and responsive physiological changes that alter the prevalence and location of many proteins, including PFAS-related proteins. Therefore, we hypothesize that if key PFAS-related proteins are impacted as a result of environmentally induced as well as biologically programmed physiological changes (e.g. reproduction), then PFAS that associate with those proteins will also be impacted. Changes in tissue distribution across tissues of PFAS due to these dynamics may have implications for wildlife studies where these chemicals are measured in biological matrices (e.g., serum, feathers, eggs). For example, failure to account for factors contributing to PFAS variability in a tissue may result in exposure misclassification as measured concentrations may not reflect average exposure levels. The goal of this review is to share general information with the PFAS research community on what biotic and abiotic changes might be important to consider when designing and interpreting a biomonitoring or an ecotoxicity based wildlife study. This review will also draw on parallels from the epidemiological discipline to improve study design in wildlife research. Overall, understanding these connections between biotic and abiotic environments, dynamic protein levels, PFAS levels measured in wildlife, and epidemiology serves to strengthen study design and study interpretation and thus strengthen conclusions derived from wildlife studies for years to come.

Carla Ng - Assistant Professor, Department of Civil and Environmental Engineering, University of ... more Carla Ng - Assistant Professor, Department of Civil and Environmental Engineering, University of Pittsburgh and secondary appointment in Environmental and Occupational Health, Graduate School of Public Health. Per- and polyfluorinated alkyl substances (PFAS) are a global environmental and public health problem, now known to contaminate drinking water, food, wildlife and humans. Their unique physicochemical properties and extreme persistence have made them incredibly challenging to study and difficult to remove from contaminated sites. As more is discovered about their toxicological impacts, diverse chemistries, and widespread use, there is an urgent need to develop better methods to track their impacts and remove them from the environment. In this talk I will discuss my group’s strategies to investigate PFAS fate and effects through the lens of their interactions with proteins in biological systems, and how these interactions may be exploited in the design of biologically inspired remediation techniques.Ope

Results of this limited-scope project confirmed the potential of protein-based sorbents for per-a... more Results of this limited-scope project confirmed the potential of protein-based sorbents for per-and polyfluorinated alkyl substances (PFAS) remediation by identifying, through a complementary model-experiment approach, proteins that associate strongly with both long-and short-chain PFAS. Of particular benefit is the ability we identified to tune an adsorbent, by incorporating multiple proteinbased moieties and/or by use of strategic changes in feed composition (ionic strength, pH), to address a wide variety of PFAS structures. The combination of molecular modeling and batch testing used here thus forms the basis of a robust and powerful design framework for developing protein-based sorbents for PFAS water treatment. 15. SUBJECT TERMS Bioinspired sorbents, filter media, PFAS water treatment 16. SECURITY CLASSIFICATION OF: Unclassified Unlimited 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON

Toxicological Sciences, 2021

Predictive toxicology is increasingly reliant on innovative computational methods to address pres... more Predictive toxicology is increasingly reliant on innovative computational methods to address pressing questions in chemicals assessment. Of importance is the evaluation of contaminant impact differences across species to inform ecosystem protection and identify appropriate model species for human toxicity studies. Here we evaluated 2 complementary tools to predict cross-species differences in binding affinity between per- and polyfluoroalkyl substances (PFAS) and the liver fatty acid-binding protein (LFABP): the Sequence Alignment to Predict Across Species Susceptibility (SeqAPASS) tool and molecular dynamics (MD). SeqAPASS determined that the structure of human LFABP, a key determinant of PFAS bioaccumulation, was conserved in the majority of vertebrate species, indicating these species would have similar PFAS bioaccumulation potentials. Level 3 SeqAPASS evaluation identified several potentially destabilizing amino acid differences across species, which were generally supported by ...

Environmental Science: Processes & Impacts, 2020

Systematic description of more than 200 uses of PFAS and the individual substances associated wit... more Systematic description of more than 200 uses of PFAS and the individual substances associated with each of them (over 1400 PFAS in total).

Environmental Science & Technology, 2020

Fluoropolymers are a group of polymers within the class of per-and polyfluoroalkyl substances (PF... more Fluoropolymers are a group of polymers within the class of per-and polyfluoroalkyl substances (PFAS). The objective of this analysis is to evaluate the evidence regarding the environmental and human health impacts of fluoropolymers throughout their life cycle(s). Production of some fluoropolymers is intimately linked to the use and emissions of legacy and novel PFAS as polymer processing aids. There are serious concerns regarding the toxicity and adverse effects of fluorinated processing aids on humans and the environment. A variety of other PFAS, including monomers and oligomers, are emitted during the production, processing, use, and end-of-life treatment of fluoropolymers. There are further concerns regarding the safe disposal of fluoropolymers and their associated products and articles at the end of their life cycle. While recycling and reuse of fluoropolymers is performed on some industrial waste, there are only limited options for their recycling from consumer articles. The evidence reviewed in this analysis does not find a scientific rationale for concluding that fluoropolymers are of low concern for environmental and human health. Given fluoropolymers' extreme persistence; emissions associated with their production, use, and disposal; and a high likelihood for human exposure to PFAS, their production and uses should be curtailed except in cases of essential uses.

Environmental Toxicology and Chemistry, 2020

Reports of environmental and human health impacts of per- and polyfluoroalkyl substances (PFAS) h... more Reports of environmental and human health impacts of per- and polyfluoroalkyl substances (PFAS) have greatly increased in the peer-reviewed literature. The goals of this review are to assess the state of the science regarding toxicological effects of PFAS, and to develop strategies for advancing knowledge on the health effects of this large family of chemicals. Currently, much of the toxicity data available for PFAS are for a handful of chemicals, primarily legacy PFAS such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Epidemiological studies have revealed associations between exposure to specific PFAS and a variety of health effects, including altered immune and thyroid function, liver disease, lipid and insulin dysregulation, kidney disease, adverse reproductive and developmental outcomes, and cancer. Concordance with experimental animal data exists for many of these effects. However, information on modes of action and adverse outcome pathways must be expanded, and profound differences in PFAS toxicokinetic properties must be considered in understanding differences in responses between sexes and among species and life stages. With many health effects noted for a relative few example compounds, and hundreds of other PFAS in commerce lacking toxicity data, more contemporary and high throughput approaches such as read across, molecular dynamics, and protein modeling are proposed to accelerate the development of toxicity information on emerging and legacy PFAS, individually and as mixtures. Additionally, an appropriate degree of precaution, given what is already known from the PFAS examples noted here, may be needed to protect human health. This article is protected by copyright. All rights reserved.

Polycyclic aromatic hydrocarbons (PAHs) are a diverse group of environmental contaminants release... more Polycyclic aromatic hydrocarbons (PAHs) are a diverse group of environmental contaminants released during combustion of organic materials and the production and utilization of fossil fuels. Once released, PAHs deposit in soil and water bodies where they are subject to environmental transport and transformations. As they degrade, intermediate transformation products may play an important role in their environmental impact. However, studying the effects of these degradation products has proven challenging due to the complexity, transience, and low concentration of many intermediates. Herein, a novel integration of a pathway prediction system and network theory was developed and applied to a set of four PAHs to demonstrate a possible solution to this challenge. Network analysis techniques were employed to refine the thousands of potential outputs and elucidate compounds of interest. Using these tools, we determined correlations between PAH degradation network data and intermediate metabolite structures, gaining information about the chemical characteristics of compounds based on their placement within the degradation network. Upon applying our developed filtering algorithm, we are able to predict up to 48% of the most common transformation products identified in a comprehensive empirical literature review. Additionally, our integrated approach uncovers potential metabolites which connect those found by past empirical studies but are currently undetected, thereby filling in the gaps of information in PAH degradation pathways.

Environmental Science: Processes & Impacts, 2020

Grouping strategies are needed for per- and polyfluoroalkyl substances (PFAS), in part, because i... more Grouping strategies are needed for per- and polyfluoroalkyl substances (PFAS), in part, because it would be time and resource intensive to test and evaluate the more than 4700 PFAS on the global market on a chemical-by-chemical basis.

A high-quality parameter set is essential for reliable stormwater models. Model performance can b... more A high-quality parameter set is essential for reliable stormwater models. Model performance can be improved by optimizing initial parameter estimates. Parameter sensitivity analysis is a robust way to distinguish the influence of parameters on model output and efficiently target the most important parameters to modify. This study evaluates efficient construction of a sewershed model using relatively low-resolution (e.g., 30 meter DEM) data and explores model sensitivity to parameters and regional characteristics using the EPA’s Storm Water Management Model (SWMM). A SWMM model was developed for a sewershed in the City of Pittsburgh, where stormwater management is a critical concern. We assumed uniform or log-normal distributions for parameters and used Monte Carlo simulations to explore and rank the influence of parameters on predicted surface runoff, peak flow, maximum pipe flow and model performance, as measured using the Nash–Sutcliffe efficiency metric. By using the Thiessen pol...

Environment International, 2020

Environmental Science & Technology, 2019

A recent OECD report estimated that more than 4000 per-and polyfluorinated alkyl substances (PFAS... more A recent OECD report estimated that more than 4000 per-and polyfluorinated alkyl substances (PFASs) have been produced and used in a broad range of industrial and consumer applications. However, little is known about the potential hazards (e.g., bioactivity, bioaccumulation, and toxicity) of most PFASs. Here, we built machine-learning-based quantitative structure−activity relationship (QSAR) models to predict the bioactivity of those PFASs. By examining a number of available molecular data sets, we constructed the first PFAS-specific database that contains the bioactivity information on 1012 PFASs for 26 bioassays. On the basis of the collected PFAS data set, we trained 5 different machine learning models that cover a variety of conventional models (e.g., random forest and multitask neural network (MNN)) and advanced graph-based models (e.g., graph convolutional network). Those models were evaluated based on the validation data set. Both MNN and graph-based models demonstrated the best performance. The average of the best area-under-the-curve score for each bioassay is 0.916. For predictions on the OECD list, most of the biologically active PFASs have perfluoroalkyl chain lengths less than 12 and are categorized into fluorotelomer-related compounds and perfluoroalkyl acids and their precursors.

Environmental Toxicology and Chemistry, 2019

Perfluorooctane sulfonate (PFOS) is a member of the anthropogenic class of per-and polyfluorinate... more Perfluorooctane sulfonate (PFOS) is a member of the anthropogenic class of per-and polyfluorinated alkyl substances (PFASs), and is one of the most frequently detected PFAS in water, humans, mammals, and fish around the world. The zebrafish (Danio rerio), is a small freshwater fish considered an appropriate vertebrate model for investigating the toxicity of compounds. Previous investigations showed tissue-specific bioaccumulation and alterations in the expression of fatty acid binding proteins (fabps) in male and female zebrafish, potentially due to interactions between PFAS and fatty acid transporters. In addition, a number of neurological impacts have been reported as a result of human and animal exposure to PFAS. Therefore, this comprehensive study was designed to investigate whether PFOS exposure affects the expression of genes associated with fatty acid metabolism (fabp1a, fabp2, and fabp10a) in zebrafish liver, intestine, heart, and ovary and genes involved in the nervous system (ChAT, ngf, bdnf, AChE, and hdac6) in brain and muscle. Results indicate alterations in expression of genes associated with fatty acid metabolism and neural function that vary with both exposure concentration and sex. Additionally, our findings highlight that the expression of these genes differ according to exposure duration. Our results extend the knowledge base on PFOS effects to other tissues less often studied than the liver. The findings of this investigation provide a basis for future studies on the potential risks of PFOS as one of the most abundant PFAS in the environment.

Because of the extreme persistence of per- and polyfluoroalkyl substances (PFASs) and their assoc... more Because of the extreme persistence of per- and polyfluoroalkyl substances (PFASs) and their associated risks, the Madrid Statement argues for stopping their use where they are deemed not essential or when safer alternatives exist. To determine when uses of PFASs have an essential function in modern society, and when they do not, is not an easy task. Here, we: 1) develop the concept of “essential use” based on an existing approach described in the Montreal Protocol, 2) apply the concept to various uses of PFASs to determine the feasibility of elimination or substitution of PFASs in each use category, and 3) outline the challenges for phasing out uses of PFASs in society. In brief, we developed three distinct categories to describe the different levels of essentiality of individual uses. A phase-out of many uses of PFASs can be implemented because they are not necessary for the betterment of society in terms of health and safety, or because functional alternatives are currently availa...

Organohalogen Compounds, 2012

Introduction Over the last few decades, land under agricultural activity within the Great Barrier... more Introduction Over the last few decades, land under agricultural activity within the Great Barrier Reef (GBR) catchment area has increased to around 12,000 km 2 (2.8%) 1 , and is confined within a narrow, fertile strip along the coastal flood plains of Queensland, Australia. This increase in agricultural land brought along an increase in pesticide use 2 , which consequently resulted in a ubiquitous contamination of the agricultural land 3 , seawater 4 and sediment 5

Environmental science & technology, Jan 20, 2015

Methods to predict the bioaccumulation potential of per- and polyfluorinated alkyl substances (PF... more Methods to predict the bioaccumulation potential of per- and polyfluorinated alkyl substances (PFAS) are sorely needed, given the proliferation of these substances and lack of data on their properties and behavior. Here, we test whether molecular docking, a technique where interactions between proteins and ligands are simulated to predict both bound conformation and interaction affinity, can be used to predict PFAS binding strength and biological half-life. We show that an easy-to-implement docking program, Autodock Vina, can successfully redock perfluorooctanesulfonate (PFOS) to human serum albumin with deviations smaller than 2 Å. Furthermore, predicted binding strengths largely fall within one standard deviation of measured values for perfluorinated alkyl acids (PFAAs). Correlations with half-lives suggest both membrane partitioning and protein interactions are important, and that serum albumin is only one of a number of proteins controlling the fate of these chemicals in organis...

Atmospheric Pollution Research, 2012

Science of The Total Environment, 2012

► Multimedia environmental fate model for tropical river catchment. ► Importance of rainfall on m... more ► Multimedia environmental fate model for tropical river catchment. ► Importance of rainfall on mobilisation of diuron from soil. ► Twofold decrease of diuron in seawater after restricted diuron use.

Global Change Biology, 2010

Climate change will have substantial impacts on biodiversity, particularly for aquatic species. W... more Climate change will have substantial impacts on biodiversity, particularly for aquatic species. Warming temperatures and changing weather patterns will also remobilize and modify chemical partitioning. Holding millions of cubic yards of sediments contaminated with persistent legacy chemicals such as polychlorinated biphenyls (PCBs) and dioxins, the Laurentian Great Lakes are a laboratory for observing interactions between biological and chemical responses to climate change. They provide a wide range of habitat to a variety of species, from littoral forage fish to deep-water predators. In this paper, we couple bioenergetic and bioaccumulation models to investigate the biological and chemical effects of climate change in the Great Lakes. We consider three species: round goby, a warm-water invasive forage fish; mottled sculpin, a cool-water native forage fish; and lake trout, a cold-water native predator. Using our coupled models, we calculate the accumulation of a representative persistent chemical, PCB-77, under four climate scenarios for Lake Erie and Lake Superior. Predator-prey (lake trout-round goby) interactions and food availability (high-low) are incorporated into our simulations. For cool-to cold-water species (sculpin, lake trout) we find that warm temperatures limit growth. For warm-water species (round goby) cold temperatures limit growth. The impact of climate warming on growth depends on the winter lows as well as the summer highs of the scenario, in combination with the species' critical upper and lower thermal limits. We find conditions for high growth and consumption rates generally lead to high bioaccumulation. However, this can be confounded by predator-prey dynamics, as mismatches in the temperature preferences of predator and prey can lead to mismatches in relative growth and uptake rates. As predator-prey dynamics are expected to undergo substantial shifts with changing climate, these relative thermal sensitivities will be key in determining the implications of climate change for bioaccumulation, particularly in top predator species.

Environmental Toxicology and Chemistry, 2012

Multimedia environmental fate models are valuable tools for investigating potential changes assoc... more Multimedia environmental fate models are valuable tools for investigating potential changes associated with global climate change, particularly because thermodynamic forcing on partitioning behavior as well as diffusive and nondiffusive exchange processes are implicitly considered. Similarly, food-web bioaccumulation models are capable of integrating the net effect of changes associated with factors such as temperature, growth rates, feeding preferences, and partitioning behavior on bioaccumulation potential. For the climate change scenarios considered in the present study, such tools indicate that alterations to exposure concentrations are typically within a factor of 2 of the baseline output. Based on an appreciation for the uncertainty in model parameters and baseline output, the authors recommend caution when interpreting or speculating on the relative importance of global climate change with respect to how changes caused by it will influence chemical fate and bioavailability.

Environment International, 2022

Per- and polyfluoroalkyl substances (PFAS) accumulation and elimination in both wildlife and huma... more Per- and polyfluoroalkyl substances (PFAS) accumulation and elimination in both wildlife and humans is largely attributed to PFAS interactions with proteins, including but not limited to organic anion transporters (OATs), fatty acid binding proteins (FABPs), and serum proteins such as albumin. In wildlife, changes in the biotic and abiotic environment (e.g. salinity, temperature, reproductive stage, and health status) often lead to dynamic and responsive physiological changes that alter the prevalence and location of many proteins, including PFAS-related proteins. Therefore, we hypothesize that if key PFAS-related proteins are impacted as a result of environmentally induced as well as biologically programmed physiological changes (e.g. reproduction), then PFAS that associate with those proteins will also be impacted. Changes in tissue distribution across tissues of PFAS due to these dynamics may have implications for wildlife studies where these chemicals are measured in biological matrices (e.g., serum, feathers, eggs). For example, failure to account for factors contributing to PFAS variability in a tissue may result in exposure misclassification as measured concentrations may not reflect average exposure levels. The goal of this review is to share general information with the PFAS research community on what biotic and abiotic changes might be important to consider when designing and interpreting a biomonitoring or an ecotoxicity based wildlife study. This review will also draw on parallels from the epidemiological discipline to improve study design in wildlife research. Overall, understanding these connections between biotic and abiotic environments, dynamic protein levels, PFAS levels measured in wildlife, and epidemiology serves to strengthen study design and study interpretation and thus strengthen conclusions derived from wildlife studies for years to come.

Carla Ng - Assistant Professor, Department of Civil and Environmental Engineering, University of ... more Carla Ng - Assistant Professor, Department of Civil and Environmental Engineering, University of Pittsburgh and secondary appointment in Environmental and Occupational Health, Graduate School of Public Health. Per- and polyfluorinated alkyl substances (PFAS) are a global environmental and public health problem, now known to contaminate drinking water, food, wildlife and humans. Their unique physicochemical properties and extreme persistence have made them incredibly challenging to study and difficult to remove from contaminated sites. As more is discovered about their toxicological impacts, diverse chemistries, and widespread use, there is an urgent need to develop better methods to track their impacts and remove them from the environment. In this talk I will discuss my group’s strategies to investigate PFAS fate and effects through the lens of their interactions with proteins in biological systems, and how these interactions may be exploited in the design of biologically inspired remediation techniques.Ope

Results of this limited-scope project confirmed the potential of protein-based sorbents for per-a... more Results of this limited-scope project confirmed the potential of protein-based sorbents for per-and polyfluorinated alkyl substances (PFAS) remediation by identifying, through a complementary model-experiment approach, proteins that associate strongly with both long-and short-chain PFAS. Of particular benefit is the ability we identified to tune an adsorbent, by incorporating multiple proteinbased moieties and/or by use of strategic changes in feed composition (ionic strength, pH), to address a wide variety of PFAS structures. The combination of molecular modeling and batch testing used here thus forms the basis of a robust and powerful design framework for developing protein-based sorbents for PFAS water treatment. 15. SUBJECT TERMS Bioinspired sorbents, filter media, PFAS water treatment 16. SECURITY CLASSIFICATION OF: Unclassified Unlimited 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON

Toxicological Sciences, 2021

Predictive toxicology is increasingly reliant on innovative computational methods to address pres... more Predictive toxicology is increasingly reliant on innovative computational methods to address pressing questions in chemicals assessment. Of importance is the evaluation of contaminant impact differences across species to inform ecosystem protection and identify appropriate model species for human toxicity studies. Here we evaluated 2 complementary tools to predict cross-species differences in binding affinity between per- and polyfluoroalkyl substances (PFAS) and the liver fatty acid-binding protein (LFABP): the Sequence Alignment to Predict Across Species Susceptibility (SeqAPASS) tool and molecular dynamics (MD). SeqAPASS determined that the structure of human LFABP, a key determinant of PFAS bioaccumulation, was conserved in the majority of vertebrate species, indicating these species would have similar PFAS bioaccumulation potentials. Level 3 SeqAPASS evaluation identified several potentially destabilizing amino acid differences across species, which were generally supported by ...

Environmental Science: Processes & Impacts, 2020

Systematic description of more than 200 uses of PFAS and the individual substances associated wit... more Systematic description of more than 200 uses of PFAS and the individual substances associated with each of them (over 1400 PFAS in total).

Environmental Science & Technology, 2020

Fluoropolymers are a group of polymers within the class of per-and polyfluoroalkyl substances (PF... more Fluoropolymers are a group of polymers within the class of per-and polyfluoroalkyl substances (PFAS). The objective of this analysis is to evaluate the evidence regarding the environmental and human health impacts of fluoropolymers throughout their life cycle(s). Production of some fluoropolymers is intimately linked to the use and emissions of legacy and novel PFAS as polymer processing aids. There are serious concerns regarding the toxicity and adverse effects of fluorinated processing aids on humans and the environment. A variety of other PFAS, including monomers and oligomers, are emitted during the production, processing, use, and end-of-life treatment of fluoropolymers. There are further concerns regarding the safe disposal of fluoropolymers and their associated products and articles at the end of their life cycle. While recycling and reuse of fluoropolymers is performed on some industrial waste, there are only limited options for their recycling from consumer articles. The evidence reviewed in this analysis does not find a scientific rationale for concluding that fluoropolymers are of low concern for environmental and human health. Given fluoropolymers' extreme persistence; emissions associated with their production, use, and disposal; and a high likelihood for human exposure to PFAS, their production and uses should be curtailed except in cases of essential uses.

Environmental Toxicology and Chemistry, 2020

Reports of environmental and human health impacts of per- and polyfluoroalkyl substances (PFAS) h... more Reports of environmental and human health impacts of per- and polyfluoroalkyl substances (PFAS) have greatly increased in the peer-reviewed literature. The goals of this review are to assess the state of the science regarding toxicological effects of PFAS, and to develop strategies for advancing knowledge on the health effects of this large family of chemicals. Currently, much of the toxicity data available for PFAS are for a handful of chemicals, primarily legacy PFAS such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Epidemiological studies have revealed associations between exposure to specific PFAS and a variety of health effects, including altered immune and thyroid function, liver disease, lipid and insulin dysregulation, kidney disease, adverse reproductive and developmental outcomes, and cancer. Concordance with experimental animal data exists for many of these effects. However, information on modes of action and adverse outcome pathways must be expanded, and profound differences in PFAS toxicokinetic properties must be considered in understanding differences in responses between sexes and among species and life stages. With many health effects noted for a relative few example compounds, and hundreds of other PFAS in commerce lacking toxicity data, more contemporary and high throughput approaches such as read across, molecular dynamics, and protein modeling are proposed to accelerate the development of toxicity information on emerging and legacy PFAS, individually and as mixtures. Additionally, an appropriate degree of precaution, given what is already known from the PFAS examples noted here, may be needed to protect human health. This article is protected by copyright. All rights reserved.

Polycyclic aromatic hydrocarbons (PAHs) are a diverse group of environmental contaminants release... more Polycyclic aromatic hydrocarbons (PAHs) are a diverse group of environmental contaminants released during combustion of organic materials and the production and utilization of fossil fuels. Once released, PAHs deposit in soil and water bodies where they are subject to environmental transport and transformations. As they degrade, intermediate transformation products may play an important role in their environmental impact. However, studying the effects of these degradation products has proven challenging due to the complexity, transience, and low concentration of many intermediates. Herein, a novel integration of a pathway prediction system and network theory was developed and applied to a set of four PAHs to demonstrate a possible solution to this challenge. Network analysis techniques were employed to refine the thousands of potential outputs and elucidate compounds of interest. Using these tools, we determined correlations between PAH degradation network data and intermediate metabolite structures, gaining information about the chemical characteristics of compounds based on their placement within the degradation network. Upon applying our developed filtering algorithm, we are able to predict up to 48% of the most common transformation products identified in a comprehensive empirical literature review. Additionally, our integrated approach uncovers potential metabolites which connect those found by past empirical studies but are currently undetected, thereby filling in the gaps of information in PAH degradation pathways.

Environmental Science: Processes & Impacts, 2020

Grouping strategies are needed for per- and polyfluoroalkyl substances (PFAS), in part, because i... more Grouping strategies are needed for per- and polyfluoroalkyl substances (PFAS), in part, because it would be time and resource intensive to test and evaluate the more than 4700 PFAS on the global market on a chemical-by-chemical basis.

A high-quality parameter set is essential for reliable stormwater models. Model performance can b... more A high-quality parameter set is essential for reliable stormwater models. Model performance can be improved by optimizing initial parameter estimates. Parameter sensitivity analysis is a robust way to distinguish the influence of parameters on model output and efficiently target the most important parameters to modify. This study evaluates efficient construction of a sewershed model using relatively low-resolution (e.g., 30 meter DEM) data and explores model sensitivity to parameters and regional characteristics using the EPA’s Storm Water Management Model (SWMM). A SWMM model was developed for a sewershed in the City of Pittsburgh, where stormwater management is a critical concern. We assumed uniform or log-normal distributions for parameters and used Monte Carlo simulations to explore and rank the influence of parameters on predicted surface runoff, peak flow, maximum pipe flow and model performance, as measured using the Nash–Sutcliffe efficiency metric. By using the Thiessen pol...

Environment International, 2020

Environmental Science & Technology, 2019

A recent OECD report estimated that more than 4000 per-and polyfluorinated alkyl substances (PFAS... more A recent OECD report estimated that more than 4000 per-and polyfluorinated alkyl substances (PFASs) have been produced and used in a broad range of industrial and consumer applications. However, little is known about the potential hazards (e.g., bioactivity, bioaccumulation, and toxicity) of most PFASs. Here, we built machine-learning-based quantitative structure−activity relationship (QSAR) models to predict the bioactivity of those PFASs. By examining a number of available molecular data sets, we constructed the first PFAS-specific database that contains the bioactivity information on 1012 PFASs for 26 bioassays. On the basis of the collected PFAS data set, we trained 5 different machine learning models that cover a variety of conventional models (e.g., random forest and multitask neural network (MNN)) and advanced graph-based models (e.g., graph convolutional network). Those models were evaluated based on the validation data set. Both MNN and graph-based models demonstrated the best performance. The average of the best area-under-the-curve score for each bioassay is 0.916. For predictions on the OECD list, most of the biologically active PFASs have perfluoroalkyl chain lengths less than 12 and are categorized into fluorotelomer-related compounds and perfluoroalkyl acids and their precursors.

Environmental Toxicology and Chemistry, 2019

Perfluorooctane sulfonate (PFOS) is a member of the anthropogenic class of per-and polyfluorinate... more Perfluorooctane sulfonate (PFOS) is a member of the anthropogenic class of per-and polyfluorinated alkyl substances (PFASs), and is one of the most frequently detected PFAS in water, humans, mammals, and fish around the world. The zebrafish (Danio rerio), is a small freshwater fish considered an appropriate vertebrate model for investigating the toxicity of compounds. Previous investigations showed tissue-specific bioaccumulation and alterations in the expression of fatty acid binding proteins (fabps) in male and female zebrafish, potentially due to interactions between PFAS and fatty acid transporters. In addition, a number of neurological impacts have been reported as a result of human and animal exposure to PFAS. Therefore, this comprehensive study was designed to investigate whether PFOS exposure affects the expression of genes associated with fatty acid metabolism (fabp1a, fabp2, and fabp10a) in zebrafish liver, intestine, heart, and ovary and genes involved in the nervous system (ChAT, ngf, bdnf, AChE, and hdac6) in brain and muscle. Results indicate alterations in expression of genes associated with fatty acid metabolism and neural function that vary with both exposure concentration and sex. Additionally, our findings highlight that the expression of these genes differ according to exposure duration. Our results extend the knowledge base on PFOS effects to other tissues less often studied than the liver. The findings of this investigation provide a basis for future studies on the potential risks of PFOS as one of the most abundant PFAS in the environment.

Because of the extreme persistence of per- and polyfluoroalkyl substances (PFASs) and their assoc... more Because of the extreme persistence of per- and polyfluoroalkyl substances (PFASs) and their associated risks, the Madrid Statement argues for stopping their use where they are deemed not essential or when safer alternatives exist. To determine when uses of PFASs have an essential function in modern society, and when they do not, is not an easy task. Here, we: 1) develop the concept of “essential use” based on an existing approach described in the Montreal Protocol, 2) apply the concept to various uses of PFASs to determine the feasibility of elimination or substitution of PFASs in each use category, and 3) outline the challenges for phasing out uses of PFASs in society. In brief, we developed three distinct categories to describe the different levels of essentiality of individual uses. A phase-out of many uses of PFASs can be implemented because they are not necessary for the betterment of society in terms of health and safety, or because functional alternatives are currently availa...

Organohalogen Compounds, 2012

Introduction Over the last few decades, land under agricultural activity within the Great Barrier... more Introduction Over the last few decades, land under agricultural activity within the Great Barrier Reef (GBR) catchment area has increased to around 12,000 km 2 (2.8%) 1 , and is confined within a narrow, fertile strip along the coastal flood plains of Queensland, Australia. This increase in agricultural land brought along an increase in pesticide use 2 , which consequently resulted in a ubiquitous contamination of the agricultural land 3 , seawater 4 and sediment 5

Environmental science & technology, Jan 20, 2015

Methods to predict the bioaccumulation potential of per- and polyfluorinated alkyl substances (PF... more Methods to predict the bioaccumulation potential of per- and polyfluorinated alkyl substances (PFAS) are sorely needed, given the proliferation of these substances and lack of data on their properties and behavior. Here, we test whether molecular docking, a technique where interactions between proteins and ligands are simulated to predict both bound conformation and interaction affinity, can be used to predict PFAS binding strength and biological half-life. We show that an easy-to-implement docking program, Autodock Vina, can successfully redock perfluorooctanesulfonate (PFOS) to human serum albumin with deviations smaller than 2 Å. Furthermore, predicted binding strengths largely fall within one standard deviation of measured values for perfluorinated alkyl acids (PFAAs). Correlations with half-lives suggest both membrane partitioning and protein interactions are important, and that serum albumin is only one of a number of proteins controlling the fate of these chemicals in organis...

Atmospheric Pollution Research, 2012

Science of The Total Environment, 2012

► Multimedia environmental fate model for tropical river catchment. ► Importance of rainfall on m... more ► Multimedia environmental fate model for tropical river catchment. ► Importance of rainfall on mobilisation of diuron from soil. ► Twofold decrease of diuron in seawater after restricted diuron use.

Global Change Biology, 2010

Climate change will have substantial impacts on biodiversity, particularly for aquatic species. W... more Climate change will have substantial impacts on biodiversity, particularly for aquatic species. Warming temperatures and changing weather patterns will also remobilize and modify chemical partitioning. Holding millions of cubic yards of sediments contaminated with persistent legacy chemicals such as polychlorinated biphenyls (PCBs) and dioxins, the Laurentian Great Lakes are a laboratory for observing interactions between biological and chemical responses to climate change. They provide a wide range of habitat to a variety of species, from littoral forage fish to deep-water predators. In this paper, we couple bioenergetic and bioaccumulation models to investigate the biological and chemical effects of climate change in the Great Lakes. We consider three species: round goby, a warm-water invasive forage fish; mottled sculpin, a cool-water native forage fish; and lake trout, a cold-water native predator. Using our coupled models, we calculate the accumulation of a representative persistent chemical, PCB-77, under four climate scenarios for Lake Erie and Lake Superior. Predator-prey (lake trout-round goby) interactions and food availability (high-low) are incorporated into our simulations. For cool-to cold-water species (sculpin, lake trout) we find that warm temperatures limit growth. For warm-water species (round goby) cold temperatures limit growth. The impact of climate warming on growth depends on the winter lows as well as the summer highs of the scenario, in combination with the species' critical upper and lower thermal limits. We find conditions for high growth and consumption rates generally lead to high bioaccumulation. However, this can be confounded by predator-prey dynamics, as mismatches in the temperature preferences of predator and prey can lead to mismatches in relative growth and uptake rates. As predator-prey dynamics are expected to undergo substantial shifts with changing climate, these relative thermal sensitivities will be key in determining the implications of climate change for bioaccumulation, particularly in top predator species.

Environmental Toxicology and Chemistry, 2012

Multimedia environmental fate models are valuable tools for investigating potential changes assoc... more Multimedia environmental fate models are valuable tools for investigating potential changes associated with global climate change, particularly because thermodynamic forcing on partitioning behavior as well as diffusive and nondiffusive exchange processes are implicitly considered. Similarly, food-web bioaccumulation models are capable of integrating the net effect of changes associated with factors such as temperature, growth rates, feeding preferences, and partitioning behavior on bioaccumulation potential. For the climate change scenarios considered in the present study, such tools indicate that alterations to exposure concentrations are typically within a factor of 2 of the baseline output. Based on an appreciation for the uncertainty in model parameters and baseline output, the authors recommend caution when interpreting or speculating on the relative importance of global climate change with respect to how changes caused by it will influence chemical fate and bioavailability.