Analysis, Fate and Behavior of Contaminants
Session Summaries from SETAC Barcelona
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- Challenges and Opportunities in Protecting Human and Ecosystem Health: Understanding the Fate, Transport and Toxicity of Wastewater-borne Contaminants
Gurpal Toor (University of Florida) and April Z. Gu (Northeastern University)
Domestic wastewater is treated for mostly biological oxygen demand (BOD) and nutrients using centralized systems in developed countries, and it is often not treated or only minimally treated before discharging to receiving waters in many developing countries. In addition to organic matter and nutrients, domestic wastewater also contains various pollutants such as metals, pathogens and contaminants of emerging concern (CECs) that originate from industrial and other anthropogenic uses. Wastewater-born contaminants such as pathogens and metals are still the leading cause of many widespread problems in Africa and South Asia, while the goal of much of the research effort in other regions, such as North America and Europe, is on managing CECs. The goal of this session was to bring together researchers from various disciplines – environmental chemistry, engineering, ecology, hydrology, public health and toxicology – to discuss the current and protuberant issues related to the effect of wastewater-born contaminants on ecological integrity and human health.
Twelve platform presentations were delivered in the session, with three presentations focusing on advances in modeling the chemicals’ fate in various media in the environment. The improved ability to predict environmental concentrations of pollutants is crucial for risk assessment and regulation or policy formation. Several studies introduced novel or alternative approaches for bioaccumulation toxicity and ecological impact evaluation using stable isotope labeling or new high-throughput bioassays for endocrine disrupting effect screening of wastewater. Field monitoring case studies of pollutants and their transformation products were presented, highlighting the challenges and importance in effectively monitoring the fate and transport of not only the CECs but also their environmentally relevant transformation products, which may pose unexpected risks higher than that of the parent compound. For example, a presentation investigated the transformation products of sulfamethoxazole in Swedish river waters and demonstrated that there are persistent transformation products that likely exhibit different, or even higher, harmful effects compared to their parent chemical. Three presentations addressed the impacts of wastewater from centralized systems on plasticizers in Spanish river waters, PAHs in French river sediments, and seasonal variability of CECs in a German urban river. It is recognized that the large number of wastewater-born contaminants of concern pose great challenges in the monitoring, regulation and control of these contaminants in wastewater effluents. One presentation described successful stories on the proactive approach of setting numerical limits on a wide range of CECs adopted by the EU, which will initiate action towards identifying and minimizing the sources in the Rhine river.
Together, these 12 platform presentations demonstrated that wastewater-born contaminants present different challenges around the world. In some regions, the challenges arise due to the sub-optimal treatment of wastewater causing problems with the “classic” contaminants, while in other areas the “new” contaminants are of larger concern, and a considerable amount of research is underway to better understand the fate, transport and toxicity of wastewater-born contaminants. Even in developed countries, where we have a good handle on managing “classic” contaminants such as nutrients, there are situations such as onsite-wastewater treatment systems (or septic systems) where these “classic” contaminants can lead to contamination of water supplies and expose rural populations to contaminants. Wastewater was a major theme at the conference, and this session was very well attended. The session also included 24 posters that further added value and reinforced the challenges presented by wastewater-born contaminants. Overall, both platform and poster sessions contributed to enhancing our knowledge base on wastewater-born contaminants and provided new insights on what’s going on with this subject in different parts of the world.
Authors’ contact information: firstname.lastname@example.org and email@example.com
- Contaminants of Emerging Concern in Food Webs: Impacts on Non-Target Organisms
Elena Nilsen (US Geological Survey), Lutz Ahrens (Swedish University of Agricultural Sciences), Kelly Smalling (US Geological Survey), Karina Miglioranza (National University of Mar del Plata), Yolanda Picó (University of Valencia) and Meritxell Gros (Swedish University of Agricultural Sciences)
Numerous studies have been carried out over the last decade focused on contaminants of emerging concern (CECs) in various matrices including air, water, sediment, soil, biosolids, biota etc. This session highlighted the current state-of-the-art science of CECs in the aquatic environment to improve our understanding regarding their sources, environmental fate, bioaccumulation and effects on aquatic organisms. Contaminant residues in tissues of non-target organisms demonstrate exposure and may serve as a metric that can be linked to biological and ecological endpoints. Furthermore, effects of CECs have not been widely examined in combination with other stressors such as temperature, pH, habitat, disease, etc. The session featured submissions from around the world and focused on the occurrence of CECs in the environment, in tissues of organisms, and the effects of these compounds on non-target organisms and food webs.
Five platform presentations and three poster spotlight presentations were delivered during the session on topics including environmental occurrence and accumulation of CECs in non-target organisms; movement and fate of these compounds from environmental media into food webs; toxicity to and effects on aquatic organisms and populations; sources, environmental fate, replacement chemicals, risk assessment and public health implications; and toxicity of CECs in combination with additional stressors such as dissolved oxygen. The session also featured 14 posters covering topics such as the formation of degradation products, contaminant accumulation in and effects on invertebrates and fish, contaminant uptake by plants and effects on mammals, effects of exposure to municipal and hospital effluent on fish, pharmaceutical toxicity to fish, neonicotinoid and pyrethroid effects on food webs and organisms, and multi-stressor impacts of chemical mixtures and physical-chemical parameters such as dissolved oxygen and salinity.
The session was well attended with more than one hundred attendees for several presentations. The key points for the platform presentations include:
- CECs, including antibiotics and anti-psychotic drugs, accumulate in a diversity of aquatic organisms such as algae, bivalves and fish at low but measurable levels (eight species from six water bodies in five countries tested). Pharmaceuticals and endocrine disrupting compounds (EDCs) were prioritized for threats to human consumption based on their occurrence and frequency of detection. Based on the results, the authors also concluded that bivalves were good indicators of pharmaceuticals and EDCs in the environment.
- Cyclic volatile methyl siloxanes can have diffuse and variable sources. They bioaccumulate to levels of concern in fish tissues and appear to have increased persistence in low temperature environments. Bed sediments are the key driver of their entry into food webs.
- The hazard and exposure assessment of perfluorophosphonates (PFPAs) and perflororphosphinates (PFPiAs) revealed evidence for concern in terms of their hazardous properties and exposure in the environment, and they have been thus far overlooked and understudied. Some replacement compounds such as these have higher toxicity to aquatic species and different modes of action, and they require further assessment, especially with regard to their toxicokinetics and toxicodynamics.
- The addition of multiple stressors can increase toxicity of CECs several-fold. Diltiazem toxicity in juvenile Pimephales promelas increased under decreasing dissolved oxygen (DO) levels. Thus, laboratory studies performed at elevated DO concentrations may underestimate environmental hazards of diltiazem.
- Contaminated habitats in the Pacific Northwest of North America were implicated, in combination with other stressors, in the population declines of an ancient species, the Pacific lamprey (Entosphenus tridentatus).
Overall, the body of work presented in the platforms and posters provides novel information on the occurrence and transformations of chemicals of emerging concern and their toxicity and reproductive and genetic impacts on invertebrates, fish, mammals and food webs.
Authors’ contact information: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, Yolanda.Pico@uv.es and firstname.lastname@example.org
- Pollution Sourcing: Molecular Markers in the Field
John Harwood (Tennessee Technological University), Hideshige Takada (Tokyo University of Agriculture and Technology), Michèle Gourmelon (Ifremer), Emilie Jardé (University of Rennes) and Anna-Maria Hokajärvi and Tarja Pitkanen (Finland National Institute for Health and Welfare)
Chemical molecular marker methodology was presented in one platform and three poster spotlight presentations. Hideshige Takada presented a comprehensive survey of artificial sweeteners present in sewage receiving waters in nine African and Asisan countries. John Harwood presented the important refinement of using liquid chromatography–mass spectrometry (LC–MS) in analysis of bile acids and fecal sterols to source agricultural organic inputs to streams and rivers. Discrimination of agricultural sources of pollution by analysis of fecal stanols has been the focus of work by Emilie Jardé and colleagues. Michèle Gourmelon presented this work, and additional results focused on RNA and DNA markers to distinguish human source waste, which may indicate the presence of human pathogens in waters. Digging deeply into DNA and RNA analyses, Anna-Maria Hokajärvi presented work performed with Tarja Pitkänen to explore how the microbiome in river waters can reveal sources of pollution.
To assess the utility of artificial sweeteners as molecular markers, 386 water samples from Africa and Asia were analyzed by LC–MS/MS coupled with online solid-phase extraction. Among four artificial sweeteners, acesulfame (ACE) was most frequently detected (69% of the samples) due to its wide usage and low detection limit; sucralose was less frequently detected (13%) due to a higher detection limit (100 ng/L) and less usage in some low-income countries. Saccharin (SAC) and cyclamate (CYC) were also frequently detected in surface waters despite their biodegradable nature. ACE, SAC and CYC concentrations in the river water showed positive correlation with those of the other molecular markers of anthropogenic pollution, i.e., human antibiotics, coprostanol and linear alkylbenzenes.
Host-associated Bacteroidales markers and faecal stanols assigned at least one similar pollution source in 109 Brittany water samples. Bacteroidales and fecal stanol assigned a bovine origin in 54% of the samples and a human origin in 39% of the samples. The porcine fecal contamination of the water has been assigned in 7% of the samples analyzed.
The transmission pathways of waterborne pathogens and their markers were studied in the Kokemäenjoki River water course in Finland. Pathogen-specific viral and bacterial analyses as well as deep sequencing (NGS) of 16S genes (rDNA) and transcripts (rRNA) of microbial communities were conducted. Microbiome structures could clearly distinguish surface water and industrial and municipal sewage effluents. Host-specific marker analyses revealed gulls as one source of fecal contamination and Campylobacter spp. in surface water. Human-specific pathogens, such as noroviruses and consumer chemicals including artificial sweeteners, were detected in the surface water sites.
A simple, sensitive LC–MS method to analyze stanols and bile acids was found sufficient to distinguish among sources of animal pollution. The method uses a C-8 column, gradient elution with 0.2 mM ammonium acetate and 80:20 acetonitrile:methanol mobile phases, and the APCI LC–MS interface. By combining LC–MS analysis of human and agricultural source markers with identification of natural organic matter (fulvic acids), rapid assessment of common sources of dissolved organic carbon may now be achieved.
The sweetener acesulfame has proved to be the most sensitive and reliable marker to assess sewage inputs to surface waters in Asian and African countries. Combination of multiple markers increased ability and reliability of the detection of sewage contamination and provided further information on types of sewage.
A molecular source tracking toolbox, which includes three host-associated real-time polymerase chain reaction (PCR) Bacteroidales markers and fecal stanols, is effective in distinguishing human and agricultural animals (bovine and porcine) as sources of pollution in river water. Detection of PCR and chemical markers do not always coincide, and it may be that the two types of markers can be applied in a complementary fashion. Besides being more specific than the traditional bacterial marker E. coli, in some cases the Microbial Source Tracking (MST) markers are found to indicate pollution where E. coli is not measurable.
Pathogen- and host-specific analyses confirm the link between wastewater discharges and pathogenicity detected in Kokemäenjoki River water. However, the characterization of the environmental water microbiome structure shows that factors other than human-impacted loading may affect most of the active members of microbiome.
LC–MS can greatly reduce sample preparation time and effort in the analysis of chemical markers of sewage and animal sources of organic pollution.
Over the past thirty years, much research has identified chemical markers which can reliably identify sewage inputs and common animal inputs in sourcing organic pollution in waters. PCR and LC–MS analyses greatly facilitate this science. For pollution source allocation to be widely used by researchers and regulators, it seems a good time to establish a standard set of markers and standard analytical methodology.
Authors’ contact information: email@example.com, firstname.lastname@example.org, Michele.Gourmelon@ifremer.fr, email@example.com, firstname.lastname@example.org and email@example.com
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