Linking Trace Organic Contaminants in On-Site Wastewater-Treatment Discharge with Biological Effects.

Around the globe, on-site wastewater-treatment systems (OWTSs) are critical for rural communities without access to a municipal sewer system. However, their treatment efficiency does not match that of modern wastewater-treatment plants. The impact of OWTS discharge on nearby aquatic ecosystems and their resident fish species is poorly understood. In the present study, larval and adult fathead minnows (Pimephales promelas) and adult sunfish (Lepomis macrochirus) were exposed for 21 days to two trace organic contaminant (TOrC) mixtures replicating water chemistry derived from a previous environmental study. Larval fathead minnows were assessed for survival, growth, predator avoidance, and feeding efficiency. Adult fathead minnows and sunfish were assessed for a suite of physiological endpoints (condition indices, vitellogenin, glucose), histological changes, and fecundity. The only observed effect of TOrC mixture exposure on larval fathead minnows was a decrease in feeding efficiency. Effects were mixed in exposed adult fishes, except for male sunfish which realized a significant induction of vitellogenin (p < 0.05). The consequences of TOrC mixture exposure in the present controlled laboratory study match effects observed in wild-caught sunfish in a corresponding field study. The present study begins to bridge the gap by connecting nonpoint OWTS pollution with biological effects observed in resident lake fish species. Given the effects observed despite the brevity of the laboratory mixture exposure, longer-term studies are warranted to understand the full impacts of OWTS discharge to nearby aquatic ecosystems.  Environ Toxicol Chem 2021;40:3193-3204. © 2021 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Prioritizing potential endocrine active high resolution mass spectrometry (HRMS) features in Minnesota lakewater.

Liquid chromatography high-resolution mass spectrometry (LC-HRMS) shows great potential for expanding our understanding of relevant unknown chemical components present within complex environmental mixtures. This study identified potentially endocrine active components within Minnesota lakewater by prioritizing LC-HRMS features uniquely present at sunfish spawning habitats where male fish showed signs of estrogen agonism. Porewater samples from four locations within the same lake were analyzed using liquid chromatography quadrupole time of flight mass spectrometry (LC-QToF/MS) with positive (ESI+) and negative (ESI-) electrospray ionization. Plasma vitellogenin concentrations of captured male sunfish was used to designate sites as either endocrine active (ACT; 2 sites) or reference (REF; 2 sites). Assuming unique chemical presence at active sites contributed to endocrine activity, features at significantly higher intensities (p-value < 0.05, t-value > t-critical, log-fold change > 0.1; equal variance t-test of log2 transformed data) in ACT sites were then compiled into a suspect search list for feature identification. Adducts and isotopes of prioritized features were deprioritized using pattern recognizing algorithms using mass, retention time, and intensity. Feature identities were reported according to established confidence metrics using spectral libraries and elemental composition algorithms. This LC-HRMS approach identified a number of features omitted by targeted analysis with higher relative abundances in ACT sites, including plant essential oils, fatty acids, and mycotoxins. Multivariate analysis determined whether features were either present at both sites (AB) or unique to individual ACT sites (A or B). Detection frequency across datasets indicated bias in feature prioritization influenced by the chosen sampling method and sample acquisition mode. The majority of features prioritized by this workflow remain tentatively identified or unidentified masses of interest, reflective of current limitations in shared spectral libraries for soft ionization analyses. Strategies similar to this workflow have the potential to reduce bias in database-driven toxicological prioritization frameworks.

Trace organic contaminant (TOrC) mixtures in Minnesota littoral zones: Effects of on-site wastewater treatment system (OWTS) proximity and biological impact.

On-site wastewater treatment systems (OWTSs) are an international wastewater management strategy for rural and semi-rural communities without access to centralized sewage treatment. These systems are a suspected source of trace organic contaminants (TOrCs) that may be responsible for endocrine disrupting effects to resident fish species in Minnesota Lakes. This study assessed localized porewater concentrations of TOrCs in near-shore environments across five Minnesota Lakes. Sampling sites were designated as either likely (HOME) or unlikely (REF) to receive OWTS discharges based on their proximity to shoreline households. Sampling sites also served as sunfish spawning habitats concurrently studied for biological impacts to resident adult males. Two-group hypothesis tests demonstrated significantly (p = .02) higher total TOrC concentrations in HOME (Mean = 841 ng/L) versus REF (Mean = 222 ng/L) sites. HOME sites also contained a wider suite of TOrC detections relative to REF sites. The distance to the nearest household (most proximal distance; MPD) negatively correlated (r = -0.62) with total TOrC concentrations. However, 2,4-D and DEET were major contributors to these total concentrations, suggesting that anthropogenic influence from households may not be exclusively attributed to OWTS discharges. Further, TOrC presence and elevated nitrogen concentrations in REF site porewater suggest additional, non-household TOrC discharges to these lakes. Significantly higher blood concentrations of vitellogenin (p = .03) and 11-ketotestosterone (p = .01) were observed in adult male sunfish captured from HOME versus REF sites. Comparisons between chemical and biological data indicate enhanced bioactive effects of co-contaminants. The findings from this study demonstrate multiple diffuse transport pathways contribute to the presence of biologically active TOrC mixtures in Minnesota Lakes, and mitigation efforts should consider minimizing residential inputs of chemicals associated with both outdoor and OWTS activity.