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At least 181 records · Page 10Linked to original sources
USGS2019

Predictive analysis using chemical-gene interaction networks consistent with observed endocrine activity and mutagenicity of U.S. streams

In a recent U.S. Geological Survey/U.S. Environmental Protection Agency study assessing >700 organic compounds in 38 streams, in vitro assays indicated generally low estrogen, androgen, and glucocorticoid receptor activities, but identified 13 surface waters with 17β estradiol equivalent (E2Eq) activities greater than the 1 ng/L level of concern for feminization of male fish. Among the 36 samples assayed for mutagenicity in the Salmonella bioassay (reported here), 25% were considered mutagenic (statistically significant slope and at least a two-fold increase in revertants/plate). Endocrine and mutagenic activities of the water samples were well correlated with each other and with the total number and cumulative concentrations of detected chemical contaminants. To test the predictive utility of knowledgebase-leveraging approaches, site-specific predicted chemical-gene (pCGA) and predicted analogous pathway-linked (pPLA) association networks identified in the Comparative Toxicogenomics Database were compared with observed endocrine/mutagenic bioactivities. We evaluated pCGA/pPLA patterns among sites by cluster analysis and principal component analysis and grouped the pPLA into broad mode-of-action classes. Measured E2Eq and mutagenic activities correlated well with predicted pathways. The pPLA analysis also revealed correlations with signaling, metabolic, and regulatory groups, suggesting that other effects pathways may be associated with chemical contaminants in these waters and indicating the need for broader bioassay coverage to assess potential adverse impacts.

Environmental Science & Technology↗
USGS2022

Tapwater exposures, effects potential, and residential risk management in Northern Plains Nations

In the United States (US), private-supply tapwater (TW) is rarely monitored. This data gap undermines individual/community risk-management decision-making, leading to an increased probability of unrecognized contaminant exposures in rural and remote locations that rely on private wells. We assessed point-of-use (POU) TW in three northern plains Tribal Nations, where ongoing TW arsenic (As) interventions include expansion of small community water systems and POU adsorptive-media treatment for Strong Heart Water Study participants. Samples from 34 private-well and 22 public-supply sites were analyzed for 476 organics, 34 inorganics, and 3 in vitro bioactivities. 63 organics and 30 inorganics were detected. Arsenic, uranium (U), and lead (Pb) were detected in 54%, 43%, and 20% of samples, respectively. Concentrations equivalent to public-supply maximum contaminant level(s) (MCL) were exceeded only in untreated private-well samples (As 47%, U 3%). Precautionary health-based screening levels were exceeded frequently, due to inorganics in private supplies and chlorine-based disinfection byproducts in public supplies. The results indicate that simultaneous exposures to co-occurring TW contaminants are common, warranting consideration of expanded source, point-of-entry, or POU treatment(s). This study illustrates the importance of increased monitoring of private-well TW, employing a broad, environmentally informative analytical scope, to reduce the risks of unrecognized contaminant exposures.

North Dakota, South Dakota↗
USGS2020

Skin fungal assemblages of bats vary based on susceptibility to white-nose syndrome

Microbial skin assemblages, including fungal communities, can influence host resistance to infectious diseases. The diversity-invasibility hypothesis predicts that high-diversity communities are less easily invaded than species-poor communities, and thus diverse microbial communities may prevent pathogens from colonizing a host. To explore the hypothesis that host fungal communities mediate resistance to infection by fungal pathogens, we investigated characteristics of bat skin fungal communities as they relate to susceptibility to the emerging disease white-nose syndrome (WNS). Using a culture-based approach, we compared skin fungal assemblage characteristics of 10 bat species that differ in susceptibility to WNS across 10 eastern U.S. states. The fungal assemblages on WNS-susceptible bat species had significantly lower alpha diversity and abundance compared to WNS-resistant species. Overall fungal assemblage structure did not vary based on WNS-susceptibility, but several yeast species were differentially abundant on WNS-resistant bat species. One yeast species inhibited Pseudogymnoascus destructans ( Pd ), the causative agent on WNS, in vitro under certain conditions, suggesting a possible role in host protection. Further exploration of interactions between Pd and constituents of skin fungal assemblages may prove useful for predicting susceptibility of bat populations to WNS and for developing effective mitigation strategies.

ISME Journal↗
USGS2023

Predicted aquatic exposure effects from a national urban stormwater study

A multi-agency study of 438 organic and 62 inorganic chemicals measured in urban stormwater during 50 total runoff events at 21 sites across the United States demonstrated that stormwater discharges can generate localized, aquatic exposures to extensive contaminant mixtures, including organics suspected to cause adverse aquatic-health effects. The aggregated risks to multiple aquatic trophic levels (fish, invertebrates, plants) of the stormwater mixture exposures, which were documented in the national study, were explored herein by calculating cumulative ratios of organic-contaminant in vitro exposure–activity cutoffs (∑ EAR ) and health-benchmark-weighted cumulative toxicity quotients (∑ TQ ). Both risk assessment approaches indicated substantial (moderate to high) risk for acute adverse effects to aquatic organisms across multiple trophic levels (fish, macroinvertebrates, non-vascular/vascular plants) at or near stormwater discharge points across the United States. The results are interpreted as potential orders of magnitude underestimates of actual aquatic risk in stormwater control wetlands or in the immediate vicinity of such discharges to surface-water receptors, because the 438 organic-compound analytical space assessed in this study is orders of magnitude less than the 350 000 parent compounds estimated to be in current commercial use globally and the incalculable chemical-space of potential metabolites and degradates.

Environmental Science: Water Research and Technolo↗
USGS2023

Exposures and potential health implications of contaminant mixtures in linked source water, finished drinking water, and tapwater from public-supply drinking water systems in Minneapolis/St. Paul area, USA

Continued improvements in drinking-water quality characterization and treatment/distribution infrastructure are required to address the expanding number of documented environmental contaminants. To better understand the variability in contaminant exposures from the drinking water resource (surface and groundwater), through the distribution process, to the point-of-use (tapwater), in 2019 a synoptic assessment of broad chemical exposures was conducted in system-specific source waters, finished drinking water and service-area tapwater from 10 drinking water treatment facilities in the greater Minneapolis/St. Paul area of Minnesota, United States. Source water, finished water (collected pre-distribution in the treatment facility), and tapwater samples were analyzed for 465 unique organic compounds, 34 inorganic constituents, and 3 field parameters as well as in vitro estrogen, androgen, and glucocorticoid bioactivities. Mixtures of organic and inorganic contaminants were prevalent in source water, finished water, and tapwater samples, indicating the continued need for broad assessments of mixed contaminant exposures to characterize potential drinking-water human health outcomes. Contaminant concentrations were similar among drinking water sources and no exceedances of Environmental Protection Agency maximum contaminant level(s) (MCL) were observed in any treated sample (finished water or tapwater) in this study. No treated sample contained estrogenic, androgenic, or glucocorticoid activity at concentrations that may cause adverse human health effects. However, there were multiple exceedances of non-enforceable MCL goal(s) (MCLG), and other health advisories combined with frequent exceedances of benchmark-based hazard indices in both finished water and tapwater samples. These results indicate that exposure to contaminant mixtures is a potential public health concern underscoring our continued efforts to assess contaminant mixture exposures at the drinking-water point of consumption using a broad analytical scope.

Minnesota↗
USGS2003

Effects of brevetoxins on murine myeloma SP2/O cells: Aberrant cellular division

Massive deaths of manatees (Trichechus manatus latirostris) during the red tide seasons have been attributed to brevetoxins produced by the dinoflagellate Karenia brevis (formerly Ptychodiscus breve and Gymnodinium breve). Although these toxins have been found in macrophages and lymphocytes in the lung, liver, and secondary lymphoid tissues of these animals, the molecular mechanisms of brevetoxicosis have not yet been identified. To investigate the effects of brevetoxins on immune cells, a murine myeloma cell line (SP2/O) was used as a model for in vitro studies. By adding brevetoxins to cultures of the SP2/O cells at concentrations ranging from 20 to 600 ng/ml, an apparent increase in proliferation was observed at around 2 hours post challenge as compared to the unchallenged cell cultures. This was followed by a drop in cell number at around 3 hours, suggesting an aberrant effect of brevetoxins on cellular division, the cells generated at 2 hours being apparently short-lived. In situ immunochemical staining of the SP2/O cells at 1 and 2 hour post challenge showed an accumulation of the toxins in the nucleus. A 21-kDa protein was subsequently isolated from the SP2/O cells as having brevetoxin-binding properties, and immunologically identified as p21, a nuclear factor known to down-regulate cellular proliferation through inhibition of cyclin-dependent kinases. These data are the first on a possible effect of brevetoxins on the cell cycle via binding to p21, a phenomenon that needs to be further investigated and validated in normal immune cells.

International Journal of Toxicology↗
USGS2007

Evaluating nephrotoxicity of high-molecular-weight organic compounds in drinking water from lignite aquifers

High-molecular-weight organic compounds such as humic acids and/or fulvic acids that are naturally mobilized from lignite beds into untreated drinking-water supplies were suggested as one possible cause of Balkan endemic nephropathy (BEN) and cancer of the renal pelvis. A lab investigation was undertaken in order to assess the nephrotoxic potential of such organic compounds using an in vitro tissue culture model. Because of the infeasibility of exposing kidney tissue to low concentrations of organics for years in the lab, tangential flow ultrafiltration was employed to hyperconcentrate samples suitable for discerning effects in the short time frames necessitated by tissue culture systems. Effects on HK-2 kidney cells were measured using two different cell proliferation assays (MTT and alamarBlue). Results demonstrated that exposure of kidney tissue to high-molecular-weight organics produced excess cell death or proliferation depending on concentration and duration of exposure. Copyright ?? Taylor & Francis Group, LLC.

Journal of Toxicology and Environmental Health, Pa↗
USGS2009

Recovery of cholinesterase activity in mallard ducklings administered organophosphorus pesticides

Oral doses of the organophosphorus pesticides acephate, dicrotophos, fensulfothion, fonofos, malathion, and parathion were administered to mallard ducklings ( Anas platyrhynchos ), and brain and plasma cholinesterase (ChE) activities were determined for up to 77 d after dosing. In vivo recovery of brain ChE activity to within 2 standard deviations of the mean activity of undosed birds occurred within 8 d, after being depressed an average of 25-58% at 24 h after dosing. In vivo recovery of plasma ChE appeared as fast as or faster than that of brain, but the pattern of recovery was more erratic and therefore statistical comparison with brain ChE recovery was not attempted. In vitro tests indicated that the potential for dephosphorylation to contribute to in vivo recovery of inhibited brain ChE differed among chemical treatments. Some ducklings died as a result of organophosphate dosing. In an experiment in which ducklings within each treatment group received the same dose (mg/kg), the brain ChE activity in birds that died was less than that in birds that survived. Brain ChE activities in ducklings that died were significantly different among pesticide treatments: fensulfothion > parathion> acephate > malathion (p < 0.05).

Journal of Toxicology and Environmental Health↗
USGS2019

Estrogen receptor 1 expression and methylation of Esr1 promoter in mouse fetal prostate mesenchymal cells induced by gestational exposure to bisphenol A or ethinylestradiol

Fetal/neonatal environmental estrogen exposures alter developmental programing of the prostate gland causing onset of diseases later in life. We have previously shown in vitro that exposures to 17β-estradiol (E2) and the endocrine disrupting chemical bisphenol A, at concentrations relevant to human exposure, cause an elevation of estrogen receptor α ( Esr1 ) mRNA in primary cultures of fetal mouse prostate mesenchymal cells; a similar result was observed in the fetal rat urogenital sinus. Effects of these chemicals on prostate mesenchyme in vivo are not well understood. Here we show effects in mice of fetal exposure to the estrogenic drug in mixed oral contraceptives, 17α-ethinylestradiol (EE2), at a concentration of EE2 encountered by human embryos/fetuses whose mothers become pregnant while on EE2-containing oral contraceptives, or bisphenol A at a concentration relevant to exposures observed in human fetuses in vivo . Expression of Esr1 was elevated by bisphenol A or EE2 exposures, which decreased the global expression of DNA methyltransferase 3A ( Dnmt3a ), while methylation of Esr1 promoter was significantly increased. These results show that exposures to the environmental estrogen bisphenol A and drug EE2 cause transcriptional and epigenetic alterations to expression of estrogen receptors in developing prostate mesenchyme in vivo .

Environmental Epigenetics↗
USGS2025

Derivation and characterization of environmental hazard concentrations for chemical prioritization: A case study in the Great Lakes tributaries

Ongoing anthropogenic activities and analytical advancements yield continuously expanding lists of environmental contaminants. This represents a challenge to environmental managers, who must prioritize chemicals for management actions (e.g., restriction, regulation, remediation) but are often hindered by resource limitations. To help facilitate prioritization efforts, this study presents several strategies for deriving environmental hazard concentrations using publicly accessible data and open-source computational tools. Using a Great Lakes tributaries aquatic monitoring dataset as a case study, environmental hazard concentrations were obtained or derived for 334 organic chemicals. These concentrations were based on (1) current water quality guidelines; (2) apical screening values; (3) apical and (4) nonapical effect concentrations from the ECOTOXicology Knowledgebase; (5) in vitro effect concentrations from the ToxCast database; (6) cytotoxic burst concentrations collated from the Comptox Dashboard; (7) “estimated screening values” derived from modeled or estimated data and available from various regulatory and nonregulatory agencies; (8) pharmaceutical potency estimates from the MaPPFAST database; and (9) quantitative structure-activity relationship (QSAR)–derived acute toxicity estimates. Environmental fate data included aquatic half-lives and bioconcentration factors collated from the Comptox Dashboard or estimated using QSARs. To identify patterns that could be used for characterization, availability of ecotoxicological concentrations and environmental fate data were evaluated. Furthermore, exceedances of hazard concentrations were evaluated and compared across diverse ecotoxicological data types. Altogether, by providing detailed methodology and practical examples generated with real monitoring data, this study demonstrated that these hazard concentration derivation strategies can be efficiently and effectively used with large, complex datasets and identified critical considerations for future prioritization efforts.

Great Lakes region↗
USGS2025

Potential for biological effects of per- and polyfluoroalkyl substances in Great Lakes tributaries and associations with land cover and wastewater effluent

Surface water concentrations of per- and polyfluoroalkyl substances (PFAS) and potential for resulting biological effects were estimated in a study using polar organic chemical integrative samplers (POCIS) from 60 tributary sites within 20 watersheds in the Great Lakes Basin in 2018. Sites represented a range of urban to agricultural, forested, and wetland land uses and included a gradient of wastewater treatment effluent from zero to 44% of annual streamflow. Several sites also had airport influence. Twenty-one of 32 targeted PFAS compounds were detected in POCIS samplers, of which, 16 had available POCIS sampling rates, enabling time-weighted water concentration estimates and comparison with available effects data. Estimated water concentrations were compared with published water quality guidelines (available for nine PFAS), effect concentrations reported in primary literature within the ECOTOX Knowledgebase for apical endpoints (10 PFAS) and nonapical endpoints (10 PFAS), and in vitro high-throughput screening data from the U.S. Environmental Protection Agency Toxicity Forecaster (ToxCast; 14 PFAS). Based on a conservative evaluation approach that was also weighted for persistence and limitations in available toxicological information, five individual PFAS, including perfluorooctanesulfonic acid, perfluorohexanesulfonic acid, perfluorobutanesulfonic acid, perfluorooctanoic acid, and perfluorononanoic acid were identified as warranting additional investigation. Possible increased potency of PFAS mixtures over individual chemical effects, estimated by summation of exposure-activity ratios (EARs) for chemicals that influence common ToxCast assays and specified gene targets, indicated that EAR values increased up to 5.6-fold over individual chemicals, with up to 14 chemicals contributing to mixture effect predictions. Potential for biological effects from PFAS, as estimated by summed exposure-activity ratios, were correlated with urban land use and the proportion of streamflow contributed by wastewater effluent.

Great Lakes tributaries↗
USGS2025

Prioritizing chemicals of emerging concern in the Great Lakes Basin using covariance of chemical concentrations and diverse biological responses from a variety of species

The Great Lakes Restoration Initiative aims to protect and restore the nation’s largest freshwater resource, in part, by furthering our understanding of the effects of contaminants of emerging concern (CECs) and chemical mixtures on aquatic and terrestrial organisms. To address this goal, an interagency team conducted field studies at sites along the Maumee River in Ohio, USA, in 2016–2017, monitoring CEC levels along with diverse in vitro and in vivo biological effects in ecologically relevant species (fathead minnows, tree swallows, and golden clams). The objective of the present work was to prioritize the CECs in these studies for further monitoring and assessment by determining if there are patterns in chemical–bioeffect relations across data sets, species, and response types that indicate relatively high or low hazard to aquatic life from CEC exposure. Of the 748 monitored chemicals, 425 were detected and were analyzed for covariance with bioeffects. All 748 chemicals were placed into 10 bins based on their frequencies of monitoring, detection, and covariance with bioeffects across studies and species. We describe how chemicals can be prioritized across bins to aid monitoring and assessment efforts. Our approach using effects-based monitoring data is especially useful for prioritizing chemicals with little or no traditional toxicity testing data. Similar evidence-based prioritizations will allow agencies to more efficiently allocate limited resources to improve the ability to protect aquatic and terrestrial organisms from adverse impacts due to contaminant exposure.

Ohio↗
USGS2025

Retrospective stepwise prioritization of chemicals detected in Great Lakes tributaries (2008–2018)

Through the U.S. Great Lakes Restoration Initiative, a 10-year, multiagency chemical monitoring effort was undertaken across the Great Lakes. In this effort, 586 chemicals were monitored and 334 were detected in grab/composite water samples. To help inform potential future actions, a stepwise prioritization framework was used to identify compounds for which publicly accessible water quality guidelines or effects information suggested there was potential aquatic ecotoxicity. Because water quality guidelines were only available for some chemicals, this framework used apical toxicity data collated from publicly accessible databases (e.g., the ECOTOXicology Knowledgebase) and alternative data, including literature-derived non-apical effect concentrations, in vitro bioactivities from high-throughput screening, and modeled ecotoxicity. To account for the diverse levels of confidence in these data, chemicals were prioritized within specific action categories, which suggested potential management or experimental activities that may be considered based on the types of data available for each compound. Overall, 11 detected chemicals were identified as high priority in different action categories. This included four chemicals prioritized for environmental management or targeted risk assessment, three chemicals prioritized for effects-based monitoring, one chemical prioritized for apical effects assessment, and three chemicals targeted for non-apical effects evaluation. This framework also identified 164 low-priority chemicals, among which more than 50% were prioritized based on water quality guidelines or apical effect concentrations (thus could be considered low priority for future risk assessment or management activities). Results aim to help regulatory agencies, environmental managers, and other stakeholders focus available resources on carrying out monitoring, experimental, and risk assessments for the chemicals that display the greatest potential to adversely impact Great Lakes ecosystems.

Great Lakes↗
USGS2019

Conservation genomics in the sagebrush sea: Population divergence, demographic history, and local adaptation in sage-grouse (Centrocercus spp.)

Sage-grouse are two closely related iconic species of the North American West, with historically broad distributions across sagebrush-steppe habitat. Both species are dietary specialists on sagebrush during winter, with presumed adaptations to tolerate the high concentrations of toxic secondary metabolites that function as plant chemical defenses. Marked range contraction and declining population sizes since European settlement have motivated efforts to identify distinct population genetic variation, particularly that which might be associated with local genetic adaptation and dietary specialization of sage-grouse. We assembled a reference genome and performed whole-genome sequencing across sage-grouse from six populations, encompassing both species and including several populations on the periphery of the species ranges. Population genomic analyses reaffirmed genome-wide differentiation between greater and Gunnison sage-grouse, revealed pronounced intraspecific population structure, and highlighted important differentiation of a small isolated population of greater sage-grouse in the northwest of the range. Patterns of genome-wide differentiation were largely consistent with a hypothesized role of genetic drift due to limited gene flow among populations. Inferred ancient population demography suggested persistent declines in effective population sizes that have likely contributed to differentiation within and among species. Several genomic regions with SNPs exhibiting extreme population differentiation were associated with candidate genes linked to metabolism of xenobiotic compounds. In vitro activity of enzymes isolated from sage-grouse livers supported a role for these genes in detoxification of sagebrush, suggesting that the observed interpopulation variation may underlie important local dietary adaptations, warranting close consideration for conservation strategies that link sage-grouse to the chemistry of local sagebrush.

Genome Biology and Evolution↗
USGS1976

Vitamin E and selenium interrelations in the diet of Atlantic salmon (Salmo salar): Gross, histological and biochemical deficiency signs

Either simultaneous or separate dietary deficiencies of vitamin E and selenium in Atlantic salmon during first 4 weeks of feeding caused twice the mortality shown in fish fed both supplemental vitamin E (0.5 IU/g dry diet) and selenium (0.1 µg/g). Subsequent dietary repletion with both vitamin E and selenium significantly reduced mortality during the following 2 weeks. Larger salmon (0.9 g initial mean weight), with vitamin E deficiency with or without selenium resulted in the following deficiency signs: extreme anemia, pale gills, anisocytosis, poikilocytosis, elevated plasma protein, exudative diathesis, dermal depigmentation, in vitro ascorbic acid-stimulated peroxidation in hepatic microsomes, yellow-orange liver color, yellow-brown intestinal contents, enlarged gall bladder distended with dark green bile, low vitamin E in carcass and hepatic tissue, muscular dystrophy, increased carcass fat and water, and a response to handling characterized by a transitory fainting with interruption in swimming. A deficiency of dietary selenium suppressed plasma glutathione peroxidase activity. Supplemental selenium with vitamin E significantly increased tocopherol activity in hepatic, but not carcass tissues. Supplements of both vitamin E and selenium were necessary to prevent muscular dystrophy.

Journal of Nutrition↗
USGS2003

Role of arachidonic acid and protein kinase C during maturation-inducing hormone-dependent meiotic resumption and ovulation in ovarian follicles of Atlantic croaker

The roles of arachidonic acid (AA) and protein kinase C (PKC) during in vitro maturation-inducing hormone (MIH)-dependent meiotic resumption (maturation) and ovulation were studied in ovarian follicles of Atlantic croaker (Micropogonias undulatus). The requirement for cyclooxygenase (COX) metabolites of AA was examined using a nonspecific COX inhibitor, indomethacin (IM), as well as two COX products, prostaglandin (PG) F2?? and PGE2, whereas the role of lipoxygenase (LOX) was investigated using a specific LOX inhibitor, nordihydroguaiaretic acid (NDGA). The involvement of PKC was examined using phorbol 12-myristate 13-acetate (PMA), a PKC activator, as well as GF109203X (GF), a specific inhibitor of PKC and 1-(5-isoquin- olinesulfonyl)-2-methylpiperazine (H7), nonspecific inhibitor of protein kinases. Genomic mechanisms were examined with the transcription-inhibitor actinomycin D (ActD) and the functionality of heterologous (oocyte-granulosa) gap junctions (GJ) with a dye transfer assay. The AA (100 ??M) and PGF2?? (5 ??M) did not induce maturation, and NDGA (10 ??M) did not affect MIH-dependent maturation. However, IM (100 ??M) partially inhibited MIH-dependent maturation. Conversely, AA and both PGs induced, and IM and NDGA inhibited, MIH-dependent ovulation in matured follicles. The PMA (1 ??g/ml) did not induce maturation but caused ovulation in matured follicles, whereas PKC inhibitors (GF, 5 ??M; H7, 50??M) did not affect MIH-dependent maturation but inhibited MIH- and PMA-dependent ovulation. The PMA-dependent ovulation was inhibited by IM but not by NDGA. In addition, ActD (5 ??M) blocked MIH-dependent, but not PMA-dependent, ovulation, and PGF2?? restored MIH-dependent ovulation in ActD-blocked follicles. The AA and PGs did not induce, and GF did not inhibit, MIH-dependent heterologous GJ uncoupling. In conclusion, AA and PKC mediate MIH-dependent ovulation but not meiotic resumption or heterologous GJ uncoupling in croaker follicles, but a permissive role of COX products of AA during maturation is possible. A novel model of MIH-dependent ovulation is proposed in which 1) LOX and COX metabolites of AA are both required for ovulation, but at upstream and downstream sites of the pathway, respectively, relative to PKC, and 2) PKC is downstream of genomic activation.

Biology of Reproduction↗
USGS2006

Toxicity and efficacy of Furanace on channel catfish Ictalurus punctatus (Rafinesque) infected experimentally with Aeromonas hydrophila

The 96-h medium tolerance limit of Furanace (nifurpirinol: P-7138) for channel catfish Ictalurus punctatus at 21°C was 0-94 mg/1. The most effective treatment level for channel catfish, experimentally infected with Aeromonas hydrophila , was 2mg/1 for 6.5 h. Furanace at 0.5 and 1.0 mg/1 in brain heart infusion agar reduced in vitro growth of A. hydrophila and at 2.0 mg/1 growth was completely.

Journal of Fish Diseases↗
USGS2008

Inactivation of Ichthyophonus spores using sodium hypochlorite and polyvinyl pyrrolidone iodine

Chlorine and iodine solutions were effective at inactivating Ichthyophonus spores in vitro. Inactivation in sea water increased directly with halogen concentration and exposure duration, with significant differences (P < 0.05) from controls occurring at all chlorine concentrations and exposure durations tested (1.5-13.3 ppm for 1-60 min) and at most iodine concentrations and exposure durations tested (1.2 ppm for 60 min and 5.9-10.7 ppm for 1-60 min). However, 10-fold reductions in spore viability occurred only after exposure to halogen solutions at higher concentrations and/or longer durations (13 ppm total chlorine for 1-60 min, 5.9 ppm total iodine for 60 min, and 10.7 ppm total iodine for 1-60 min). Inactivation efficacy was greater when halogen solutions were prepared in fresh water, presumably because of combined effects of halogen-induced inactivation and general spore instability in fresh water. The results have practical implications for disinfection and biocontainment in research laboratories and other facilities that handle live Ichthyophonus cultures and/or infected fish.

Journal of Fish Diseases↗