The environmental occurrence of trace organic compounds such as pharmaceuticals, personal care products, pesticides, and hormones, and their potential adverse effects on aquatic and terrestrial life and on human health is an issue that concerns not only scientists and engineers, but also the general public. Such trace organic compounds are being found with increasing frequency in the environment on a global scale (Halling-Sørensen et al., 1998; Kolpin et al., 2002; Ashton et al., 2004; Moldovan, 2006; Gulkowska et al., 2007). Research has shown that there is a wide variety of sources and pathways for these compounds to enter the environment (Campagnolo et al., 2002; Bound and Voulvoulis, 2005; Clara et al., 2005; Glassmeyer et al., 2005; Lindqvist et al., 2005; Brown et al., 2006; Conn et al., 2006; Larsson et al., 2007; Watkinson et al., 2007). Detection capabilities for organic compounds in the environment continue to be refined and detection levels continue to become ever lower. This has lead to the documented presence of many targeted compounds in water resources around the world including in sources of public drinking water (Wiegel et al., 2004; Focazio et al., 2008). Recent studies have focused on questions concerning contaminant environmental fate and behavior (Loffler et al., 2005), as well as wastewater and drinking-water-treatment efficacies (Stackelberg et al., 2004; Westerhoff et al., 2005). As the evidence mounts that some of these contaminants can have human or ecological health effects (Smital, 2008) there is a need for both better understanding of their fate in environmental systems and better communication of what the results of scientific investigations mean to the general public.
This collection of eight papers is focused on contaminants of emerging concern. Each of the papers highlights a specific aspect of this broad topic. The papers were solicited from researchers who participated in the American Water Resources Association summer specialty conference titled “Emerging Contaminants of Concern in the Environment: Issues, Investigations, and Solutions.” The conference was held in Vail, Colorado on June 25-27, 2007. The approximately 250 conference participants were treated to an interdisciplinary forum with more than 120 presentations. The conference provided an overview of the detection and sources of contaminants of emerging concern, their fate and transport in natural and engineered systems, receptors and effects, and social and engineering solutions to problems.
In the first paper, Chalew and Halden (2009) present a synthesis of the toxicological effects that two routinely used synthetic biocides, triclosan and triclocarban, can have on wildlife, laboratory animals, and human cell cultures. They compare these toxicity threshold values to observed concentrations from environmental samples. Data on the endocrine disruption, immunotoxic effects, and growth impairment were too sparse to be included in this analysis. The results indicate triclosan and triclocarban are “frequent contaminants of aquatic and terrestrial environments…” which can occur in concentrations ranging from parts per trillion levels in surface waters to parts per billion levels in biosolids. These concentrations overlap the range of toxicity thresholds reported for algae, crustaceans, and fish.
In the second paper, Sellin et al. (2009) investigate the occurrence of estrogenic compounds in Nebraska streams. They deployed polar organic chemical integrative samplers (POCIS) and caged fathead minnows at control sites and at sites downstream from wastewater-treatment plants (WWTPs). POCIS extracts were analyzed for estrogens and minnows were evaluated for estrogenic effects. Estrogens were detected infrequently at the control sites, but more frequently and at higher concentrations downstream from the WWTPs outfalls. Minnows from the site with the highest concentrations of estrogens measured in POCIS extracts “…experienced a dramatic increase in the expression of the two estrogen-responsive genes measured.”
In the third paper, Kitamura et al. (2009) expose Japanese medaka to estrogenic compounds in a variety of controlled conditions. They determined a lowest observed effect concentration of 5 ng/l as 17Β-estradiol (E2) equivalents. They note estrogenic activity exceeding 5 ng/l E2 equivalents was observed in some Japanese rivers, and suggest “in river water and in treated wastewater, total estrogenic potential needs to be further reduced…to prevent vitellogenin induction.”
In the fourth paper, Wu et al. (2009) use Escherichia coli (E. coli) as a bacterial tracer for water and sediment bound transport of microbial pathogens. They develop and calibrate a watershed scale model that simulates the interaction between water and sediment to better describe the fate of pathogens in the environment. Their analysis of ribogroups of E. coli“…suggested that sediments have an effect on the sources and transport processes of E. coli in the water column.”
In the fifth paper, Phillips and Chalmers (2009), look for organic wastewater compounds (OWCs) in urban runoff, combined sewer overflows (CSOs), and WWTP outfalls in Vermont and New York. They estimated contributions of OWCs from urban runoff and CSOs to Lake Champlain and found them to be significant. Concentrations of some OWCs that are effectively removed through normal wastewater treatment were found to occur at relatively elevated concentrations in untreated urban runoff and CSO discharge. They recommend that “…efforts to decrease the amounts of OWCs entering large receiving waters need to identify and treat waters that bypass normal wastewater-treatment processes.”
In the sixth paper, Guo and Krasner (2009) evaluate caffeine, carbamazepine, primidone, and a N-nitrosodimethylamine formation potential (NDMAFP) test as indicators of potential wastewater impacts on drinking water sources. Samples were collected from streams and/or drinking-water-treatment plant (DWTP) intakes in five states. The indicator compounds were detected at all DWTP intakes, and the NDMAFP was significantly higher in effluent-impacted waters. Their analysis determined carbamazepine and primidone “…can be used as conservative wastewater indicator, whereas the concentration of caffeine did not appear to provide the same degree of information.”
In the seventh paper, Brown et al. (2009) use a Lagrangian sampling strategy to assess inputs and losses of emerging contaminants (ECs) in St. Vrain Creek as it passes through the City of Longmont, Colorado. Samples were analyzed for 61 ECs in 16 chemical categories. The 34 ECs that were detected demonstrated a wide range of behaviors: some were quickly attenuated, while others were more persistent. Their results indicate “…the amount of attenuation observed was not sufficient to prevent aquatic biota from being exposed continuously to a wide range of ECs downstream from the Longmont WWTP and in Boulder Creek near the confluence with St. Vrain Creek.”
In the final paper, Poynton and Vulpe (2009) describe the utility of DNA microarrays for assessing potential effects of ECs. They argue that the application of ecotoxicogenomic methods can help identify the exposure level and mode of action of ECs in the environment. These methods can also be used to determine a no observed transcriptional effect level (NOTEL) for individual ECs and to help separate out the toxicity of complex mixtures. However, they note that use of these tools is “…still in their infancy and further studies are needed to evaluate their potential for water quality monitoring.”