Aquatic Toxicity of Chemical Road Dust Suppressants to Freshwater Organisms.

Unpaved roads make up at least 14 million kilometers of the worldwide road network. Although investigations of road runoff often are focused on paved roads, unpaved roads contribute large volumes of runoff to roadside aquatic habitats and introduce unique constituents to runoff, such as chemical dust suppressants. At least 200 products across five chemical categories are commercially available for road dust suppression and are typically applied at rates up to 4.5 L/m2. Many of these products are poorly described and are lacking basic information on environmental transport, fate, and potential toxicity to roadside organisms. We characterized the aquatic toxicity of 27 commercially available dust control products, including 13 biobased products from the U.S. Department of Agriculture BioPreferred catalog, using juvenile rainbow trout. Acute toxicity varied by more than 1000-fold among products, with 96-h LC50 values ranging from 1.7 to > 16,000 mg/L. Toxicity was not well-predicted by product category. Testing with selected products after simulated weathering under UV radiation did not provide evidence of photoenhanced toxicity. Additional tests with freshwater mussels, juvenile crayfish, pond snails, and amphibian larvae indicated that juvenile rainbow trout were reasonable surrogates for these organisms for a subset of products. This effort represents one of the first comparative studies of dust suppressant toxicity and provides important information for assessing risk to aquatic resources from a widely used but understudied class of contaminants in road runoff.

Toxicity of Cadmium, Copper, and Zinc to the Threatened Chiricahua Leopard Frog (Lithobates [Rana] chiricahuensis).

The Chiricahua leopard frog (Lithobates chiricahuensis) is in decline throughout the western United States, and is particularly sensitive to physical, chemical and biotic changes in their habitat. Acute toxicity tests revealed that among the metals detected in Chiricahua leopard frog habitat, copper was toxic at concentrations lower than those observed in the environment. Developing tadpoles were chronically exposed for 60 days to cadmium, copper and zinc because of the potential for long term exposure to these metals during early development. Cadmium was toxic, but at concentrations above observed environmental levels. Copper was especially toxic to this species at concentrations of about 10% of concentrations observed in their habitats. The onset of toxicity occurred within a few days of exposure, thus pulsed exposures from rain events could potentially be acutely toxic to tadpoles of this species. Zinc did not appear to have a negative impact during the acute or chronic exposures.

Acute toxicity of runoff from sealcoated pavement to Ceriodaphnia dubia and Pimephales promelas.

Runoff from coal-tar-based (CT) sealcoated pavement is a source of polycyclic aromatic hydrocarbons (PAHs) and N-heterocycles to surface waters. We investigated acute toxicity of simulated runoff collected from 5 h to 111 days after application of CT sealcoat and from 4 h to 36 days after application of asphalt-based sealcoat containing about 7% CT sealcoat (AS/CT-blend). Ceriodaphnia dubia (cladocerans) and Pimephales promelas (fathead minnows) were exposed in the laboratory to undiluted and 1:10 diluted runoff for 48 h, then transferred to control water and exposed to 4 h of ultraviolet radiation (UVR). Mortality following exposure to undiluted runoff from unsealed asphalt pavement and UVR was ≤10% in all treatments. Test organisms exposed to undiluted CT runoff samples collected during the 3 days (C. dubia) or 36 days (P. promelas) following sealcoat application experienced 100% mortality prior to UVR exposure; with UVR exposure, mortality was 100% for runoff collected across the entire sampling period. Phototoxic-equivalent PAH concentrations and mortality demonstrated an exposure-response relation. The results indicate that runoff remains acutely toxic for weeks to months after CT sealcoat application.

Derivation of soil-screening thresholds to protect the chisel-toothed kangaroo rat from uranium mine waste in northern Arizona.

Chemical data from soil and weathered waste material samples collected from five uranium mines north of the Grand Canyon (three reclaimed, one mined but not reclaimed, and one never mined) were used in a screening-level risk analysis for the Arizona chisel-toothed kangaroo rat (Dipodomys microps leucotis); risks from radiation exposure were not evaluated. Dietary toxicity reference values were used to estimate soil-screening thresholds presenting risk to kangaroo rats. Sensitivity analyses indicated that body weight critically affected outcomes of exposed-dose calculations; juvenile kangaroo rats were more sensitive to the inorganic constituent toxicities than adult kangaroo rats. Species-specific soil-screening thresholds were derived for arsenic (137 mg/kg), cadmium (16 mg/kg), copper (1,461 mg/kg), lead (1,143 mg/kg), nickel (771 mg/kg), thallium (1.3 mg/kg), uranium (1,513 mg/kg), and zinc (731 mg/kg) using toxicity reference values that incorporate expected chronic field exposures. Inorganic contaminants in soils within and near the mine areas generally posed minimal risk to kangaroo rats. Most exceedances of soil thresholds were for arsenic and thallium and were associated with weathered mine wastes.

Reconstructing high fidelity digital rock images using deep convolutional neural networks.

Imaging methods have broad applications in geosciences. Scanning electron microscopy (SEM) and micro-CT scanning have been applied for studying various geological problems. Despite significant advances in imaging capabilities, and image processing algorithms, acquiring high-quality data from images is still challenging and time-consuming. Obtaining a 3D representative volume for a tight rock sample takes days to weeks. Image artifacts such as noise further complicate the use of imaging methods for the determination of rock properties. In this study, we present applications of several convolutional neural networks (CNN) for rapid image denoising, deblurring and super-resolving digital rock images. Such an approach enables rapid imaging of larger samples, which in turn improves the statistical relevance of the subsequent analysis. We demonstrate the application of several CNNs for image restoration applicable to scientific imaging. The results show that images can be denoised without a priori knowledge of the noise with great confidence. Furthermore, we show how attaching several CNNs in an end-to-end fashion can improve the final quality of reconstruction. Our experiments with SEM and CT scan images of several rock types show image denoising, deblurring and super-resolution can be performed simultaneously.

Behavioral effects of copper on larval white sturgeon.

Early-life stage white sturgeon are sensitive to copper (Cu), with adverse behavioral responses observed during previous studies. The objectives of the present study were to quantify the effects of Cu exposure on white sturgeon swimming and feeding behaviors and determine their time to response. Larval sturgeon (1-2, 28, or 35 d posthatch [dph]) were exposed to Cu (0.5-8 µg/L) for 4 to 14 d. Abnormal behavioral changes were observed within the first few days of exposure including loss of equilibrium and immobilization. Digital video tracking software revealed decreased swimming activity with increasing Cu concentration. Significant changes in behavior and mortality occurred at concentrations of Cu between 1 and 8 µg/L. Juvenile white sturgeon, 58 dph, exposed to 12 µg/L Cu consumed 37 to 60% less food than controls after 3 d of exposure. The present results indicate that behavioral endpoints were more sensitive than some standard toxicity test endpoints and can effectively expand the sensitivity of standard toxicity tests for white sturgeon. Swimming behavior was impaired to the extent that survival in the field would likely be jeopardized. Such data would provide managers a useful metric for characterizing the risks of Cu contamination to white sturgeon. Environ Toxicol Chem 2019;38:132-144. Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Multiple stressors in amphibian communities: effects of chemical contamination, bullfrogs, and fish.

A leading hypothesis of amphibian population declines is that combinations of multiple stressors contribute to declines. We examined the role that chemical contamination, competition, and predation play singly and in combination in aquatic amphibian communities. We exposed larvae of American toads (Bufo americanus), southern leopard frogs (Rana sphenocephala), and spotted salamanders (Ambystoma maculatum) to overwintered bullfrog tadpoles (R. catesbeiana), bluegill sunfish (Lepomis macrochirus), the insecticide carbaryl, and ammonium nitrate fertilizer in 1000-L mesocosms. Most significantly, our study demonstrated that the presence of multiple factors reduced survival of B. americanus and A. maculatum and lengthened larval periods of R. sphenocephala. The presence of bluegill had the largest impact on the community; it eliminated B. americanus and A. maculatum and reduced the abundance of R. sphenocephala. Chemical contaminants had the second strongest effect on the community with the insecticide, reducing A. maculatum abundance by 50% and increasing the mass of anurans (frogs and toads) at metamorphosis; the fertilizer positively influenced time and mass at metamorphosis for both anurans and A. maculatum. Presence of overwintered bullfrogs reduced mass and increased time to metamorphosis of anurans. While both bluegill and overwintered bullfrog tadpoles had negative effects on the amphibian community, they performed better in the presence of one another and in contaminated habitats. Our results indicate that predicting deleterious combinations from single-factor effects may not be straightforward. Our research supports the hypothesis that combinations of factors can negatively impact some amphibian species and could contribute to population declines.

Toxicity of cobalt-complexed cyanide to Oncorhynchus mykiss, Daphnia magna, and Ceriodaphnia dubia. Potentiation by ultraviolet radiation and attenuation by dissolved organic carbon and adaptive UV tolerance.

BACKGROUND: Cobalt cyanide complexes often result when ore is treated with cyanide solutions to extract gold and other metals. These have recently been discovered in low but significant concentrations in effluents from gold leach operations. This study was conducted to determine the potential toxicity of cobalt-cyanide complexes to freshwater organisms and the extent to which ultraviolet radiation (UV) potentiates this toxicity. Tests were also conducted to determine if humic acids or if adaptation to UV influenced sensitivity to the cyanide complexes. METHODS: Rainbow trout (Oncorhynchus mykiss), Daphnia magna, and Ceriodaphnia dubia were exposed to potassium hexacyanocobaltate in the presence and absence of UV radiation, in the presence and absence of humic acids. Cyano-cobalt exposures were also conducted with C. dubia from cultures adapted to elevated UV. RESULTS: With an LC50 concentration of 0.38 mg/L, cyanocobalt was over a 1000 times more toxic to rainbow trout in the presence of UV at a low, environmentally relevant irradiance level (4 microW/cm2 as UVB) than exposure to this compound in the absence of UV with an LC50 of 112.9 mg/L. Toxicity was immediately apparent, with mortality occurring within an hour of the onset of exposure at the highest concentration. Fish were unaffected by exposure to UV alone. Weak-acid dissociable cyanide concentrations were observed in irradiated aqueous solutions of cyanocobaltate within hours of UV exposure and persisted in the presence of UV for at least 96 hours, whereas negligible concentrations were observed in the absence of UV. The presence of humic acids significantly diminished cyanocobalt toxicity to D. magna and reduced mortality from UV exposure. Humic acids did not significantly influence survival among C. dubia. C. dubia from UV-adapted populations were less sensitive to metallocyanide compounds than organisms from unadapted populations. CONCLUSIONS: The results indicate that metallocyanide complexes may pose a hazard to aquatic life through photochemically induced processes. Factors that decrease UV exposure such as dissolved organic carbon or increased pigmentation would diminish toxicity.

Sensitivity of lake sturgeon (Acipenser fulvescens) early life stages to 2,3,7,8-tetrachlorodibenzo-P-dioxin and 3,3',4,4',5-pentachlorobiphenyl.

The aquatic food web of the Great Lakes has been contaminated with polychlorinated biphenyls (PCBs) since the mid-20th century. Threats of PCB exposures to long-lived species of fish, such as lake sturgeon (Acipenser fulvescens), have been uncertain because of a lack of information on the relative sensitivity of the species. The objective of the present study was to evaluate the sensitivity of early-life stage lake sturgeon to 3,3',4,4',5-pentachlorobiphenyl (PCB-126) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure. Mortality, growth, morphological and tissue pathologies, swimming performance, and activity levels were used as assessment endpoints. Pericardial and yolk sac edema, tubular heart, yolk sac hemorrhaging, and small size were the most commonly observed pathologies in both TCDD and PCB-126 exposures, beginning as early as 4 d postfertilization, with many of these pathologies occurring in a dose-dependent manner. Median lethal doses for PCB-126 and TCDD in lake sturgeon were 5.4 ng/g egg (95% confidence interval, 3.9-7.4 ng/g egg) and 0.61 ng/g egg (0.47-0.82 ng/g egg), respectively. The resulting relative potency factor for PCB-126 (0.11) was greater than the World Health Organization estimate for fish (toxic equivalency factor = 0.005), suggesting that current risk assessments may underestimate PCB toxicity toward lake sturgeon. Swimming activity and endurance were reduced in lake sturgeon survivors from the median lethal doses at 60 d postfertilization. Threshold and median toxicity values indicate that lake sturgeon, like other Acipenser species, are more sensitive to PCB and TCDD than the other genus of sturgeon, Scaphirhynchus, found in North America. Indeed, lake sturgeon populations in the Great Lakes and elsewhere are susceptible to PCB/TCDD-induced developmental toxicity in embryos and reductions in swimming performance. Environ Toxicol Chem 2017;36:988-998. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

The effect of chronic chromium exposure on the health of Chinook salmon (Oncorhynchus tshawytscha).

This study was designed to determine fish health impairment of Chinook salmon (Oncorhynchus tshawytscha) exposed to chromium. Juvenile Chinook salmon were exposed to aqueous chromium concentrations (0-266 microgl(-1)) that have been documented in porewater from bottom sediments and in well waters near salmon spawning areas in the Columbia River in the northwestern United States. After Chinook salmon parr were exposed to 24 and 54 microg Crl(-1) for 105 days, neither growth nor survival of parr was affected. On day 105, concentrations were increased from 24 to 120 microg Crl(-1) and from 54 to 266 microg Crl(-1) until the end of the experiment on day 134. Weight of parr was decreased in the 24/120 microg Crl(-1) treatment, and survival was decreased in the 54/266 microg Crl(-1) treatment. Fish health was significantly impaired in both the 24/120 and 54/266 microg Crl(-1) treatments. The kidney is the target organ during chromium exposures through the water column. The kidneys of fish exposed to the greatest concentrations of chromium had gross and microscopic lesions (e.g. necrosis of cells lining kidney tububules) and products of lipid peroxidation were elevated. These changes were associated with elevated concentrations of chromium in the kidney, and reduced growth and survival. Also, variations in DNA in the blood were associated with pathological changes in the kidney and spleen. These changes suggest that chromium accumulates and enters the lipid peroxidation pathway where fatty acid damage and DNA damage (expressed as chromosome changes) occur to cause cell death and tissue damage. While most of the physiological malfunctions occurred following parr exposures to concentrations > or =120 microg Crl(-1), nuclear DNA damage followed exposures to 24 microg Crl(-1), which was the smallest concentration tested. The abnormalities measured during this study are particularly important because they are associated with impaired growth and reduced survival at concentrations > or =120 microg Crl(-1). Therefore, these changes can be used to investigate the health of resident fish in natural waters with high chromium concentrations as well as provide insight into the mechanisms of chromium toxicity.

Laboratory Production of Biofuels and Biochemicals from a Rapeseed Oil through Catalytic Cracking Conversion.

The work is based on a reported study which investigates the processability of canola oil (bio-feed) in the presence of bitumen-derived heavy gas oil (HGO) for production of transportation fuels through a fluid catalytic cracking (FCC) route. Cracking experiments are performed with a fully automated reaction unit at a fixed weight hourly space velocity (WHSV) of 8 hr(-1), 490-530 °C, and catalyst/oil ratios of 4-12 g/g. When a feed is in contact with catalyst in the fluid-bed reactor, cracking takes place generating gaseous, liquid, and solid products. The vapor produced is condensed and collected in a liquid receiver at -15 °C. The non-condensable effluent is first directed to a vessel and is sent, after homogenization, to an on-line gas chromatograph (GC) for refinery gas analysis. The coke deposited on the catalyst is determined in situ by burning the spent catalyst in air at high temperatures. Levels of CO2 are measured quantitatively via an infrared (IR) cell, and are converted to coke yield. Liquid samples in the receivers are analyzed by GC for simulated distillation to determine the amounts in different boiling ranges, i.e., IBP-221 °C (gasoline), 221-343 °C (light cycle oil), and 343 °C+ (heavy cycle oil). Cracking of a feed containing canola oil generates water, which appears at the bottom of a liquid receiver and on its inner wall. Recovery of water on the wall is achieved through washing with methanol followed by Karl Fischer titration for water content. Basic results reported include conversion (the portion of the feed converted to gas and liquid product with a boiling point below 221 °C, coke, and water, if present) and yields of dry gas (H2-C2's, CO, and CO2), liquefied petroleum gas (C3-C4), gasoline, light cycle oil, heavy cycle oil, coke, and water, if present.

Quantifying Fish Swimming Behavior in Response to Acute Exposure of Aqueous Copper Using Computer Assisted Video and Digital Image Analysis.

Behavioral responses of aquatic organisms to environmental contaminants can be precursors of other effects such as survival, growth, or reproduction. However, these responses may be subtle, and measurement can be challenging. Using juvenile white sturgeon (Acipenser transmontanus) with copper exposures, this paper illustrates techniques used for quantifying behavioral responses using computer assisted video and digital image analysis. In previous studies severe impairments in swimming behavior were observed among early life stage white sturgeon during acute and chronic exposures to copper. Sturgeon behavior was rapidly impaired and to the extent that survival in the field would be jeopardized, as fish would be swept downstream, or readily captured by predators. The objectives of this investigation were to illustrate protocols to quantify swimming activity during a series of acute copper exposures to determine time to effect during early lifestage development, and to understand the significance of these responses relative to survival of these vulnerable early lifestage fish. With mortality being on a time continuum, determining when copper first affects swimming ability helps us to understand the implications for population level effects. The techniques used are readily adaptable to experimental designs with other organisms and stressors.

Metamorphosis of two amphibian species after chronic cadmium exposure in outdoor aquatic mesocosms.

Amphibian larvae at contaminated sites may experience an alteration of metamorphic traits and survival compared to amphibians in uncontaminated conditions. Effects of chronic cadmium (Cd) exposure on the metamorphosis of American toads (Bufo americanus) and southern leopard frogs (Rana sphenocephala) were determined. The two species were reared separately from shortly after hatching through metamorphosis in outdoor mesocosms (1,325-L polyethylene cattle tanks) that simulated natural ponds and enhanced environmental realism relative to the laboratory. Both species exhibited a decrease in survival with increasing initial nominal aqueous Cd concentration. Cadmium treatment did not influence mass at metamorphosis for either species when survival was included as a covariate, but increased the age at metamorphosis for the American toads. The whole body Cd content of metamorphs increased with aqueous Cd treatment level for both species, and the American toads tended to possess more elevated residues. Cadmium quickly partitioned out of the water column and accumulated in and altered the abundance of the tadpoles' diet. Cadmium-contaminated sites may produce fewer metamorphs, and those that survive will metamorphose later and contain Cd. Interspecific differences in the response variables illustrate the importance of testing multiple species when assessing risk.

Multiple sublethal chemicals negatively affect tadpoles of the green frog, Rana clamitans.

Many habitats may be exposed to multiple chemical contaminants, particularly in agricultural areas where fertilizer and pesticide use are common; however, the singular and interactive effects of contaminants are not well understood. The objective of our study was to examine how realistic, sublethal environmental levels of ammonium nitrate fertilizer (0, 10, 20 mg/L and ammonium chloride control) and the common insecticide carbaryl (0 or 2.5 mg/L) individually and interactively affect the development, size, and survival of green frog (Rana clamitans) tadpoles. We reared tadpoles for 95 d in outdoor 1,000-L polyethylene ponds. We found that the combination of carbaryl and nitrate had a negative effect on development and mass of tadpoles compared to the positive effect that either contaminant had alone. Presence of carbaryl was generally associated with short-term increases in algal resources, including ponds exposed to both carbaryl and nitrate. However, with exposure to nitrate and carbaryl, tadpole mass and development were not positively affected as with one chemical stressor alone. The combination of these sublethal contaminants may reduce the ability of amphibians to benefit from food-rich environments or have metabolic costs. Our study demonstrates the importance of considering multiple stressors when evaluating population-level responses.

The effect of soil composition and hydration on the bioavailability and toxicity of cadmium to hibernating juvenile American toads (Bufo americanus).

The soil ecotoxicology literature has focused primarily on a few major taxa, to the neglect of other fossorial organisms such as amphibians. We selected cadmium (Cd) and the American toad (Bufo americanus) as a model contaminant and biological species to assess the impact of soil contamination on amphibian hibernation survival and post-hibernation condition. Soil sand composition (50, 70, 90%) and hydration (100, 150% water holding capacity (WHC)) were manipulated in addition to Cd concentration (0, 56, 165, 483 microg/g) to determine whether these soil properties affect toxicity. Soil Cd concentration significantly reduced survival and locomotor performance, and was correlated negatively with percent mass loss and positively with whole body Cd concentration. Higher sand content resulted in less mass loss and greater Cd uptake. Toads that were hibernated in 50% sand hydrated to 100% WHC had higher survival, less mass loss, and better sprint performance than those hibernated in 50% sand, 150% WHC. This study demonstrates that concentrations of Cd found in soil at highly contaminated sites can be bioaccumulated by hibernating amphibians and may reduce fitness. Differences in microhabitat use may cause species to vary in their exposure and susceptibility to soil contamination. The toxicity of Cd to amphibians could be greater in natural systems where there are multiple stressors and fluctuations in environmental variables.

The effects of chronic cadmium exposure on American toad (Bufo americanus) tadpoles.

American toad (Bufo americanus) tadpoles were exposed to cadmium from shortly after hatching through metamorphosis. Cadmium at 540 microg/L decreased percentage survival and metamorphosis; 5 and 54 microg/L increased growth relative to controls. Amphibians exposed to cadmium as tadpoles may be less tolerant of natural stressors in the terrestrial environment.

The effects of ultraviolet-B radiation on the toxicity of fire-fighting chemicals.

The interactive effects of ultraviolet (UV) and fire-retardant chemicals were evaluated by exposing rainbow trout (Oncorhyncus mykiss) juveniles and tadpoles of southern leopard frogs (Rana sphenocephala) to six fire-retardant formulations with and without sodium ferrocyanide (yellow prussiate of soda [YPS]) and to YPS alone under three simulated UV light treatments. Yellow prussiate of soda is used as a corrosion inhibitor in some of the fire-retardant chemical formulations. The underwater UV intensities measured were about 2 to 10% of surface irradiance measured in various aquatic habitats and were within tolerance limits for the species tested. Mortality of trout and tadpoles exposed to Fire-Trol GTS-R, Fire-Trol 300-F, Fire-Trol LCA-R, and Fire-Trol LCA-F was significantly increased in the presence of UV radiation when YPS was present in the formulation. The boreal toad (Bufo boreas), listed as endangered by the state of Colorado (USA), and southern leopard frog were similar in their sensitivity to these chemicals. Photoenhancement of fire-retardant chemicals can occur in a range of aquatic habitats and may be of concern even when optical clarity of water is low; however, other habitat characteristics can also reduce fire retardant toxicity.

Behavioral response of young rainbow trout (Oncorhynchus mykiss) to forest fire-retardant chemicals in the laboratory.

Fire-retardant chemicals often are applied in relatively pristine and environmentally sensitive areas that are potentially inhabited by endangered or threatened aquatic species. Avoidance of contaminants is an adaptive behavior that may reduce exposure to harmful conditions. We evaluated the avoidance responses of rainbow trout (Oncorhynchus mykiss) to concentrations of fire-retardant chemicals and alternate constituent formulations ranging from 0.65 to 26 mg/L. Countercurrent avoidance chambers were used in a flow-through design with receiving water at each end and a drain at the center to create a distinct boundary between treatment water and reference water. Rainbow trout consistently avoided water treated with retardants at all concentrations tested. The magnitude of the avoidance response did not appear to follow a concentration-response relationship, but rather was an all-or-none response.

Effects of a fire-retardant chemical to fathead minnows in experimental streams.

BACKGROUND: Each year millions of liters of fire-retardant chemicals are applied to wildfires across the nation. Recent laboratory studies with long-term fire-retardant chemicals indicate a significant photoenhanced toxicity of products containing sodium ferrocyanide corrosion inhibitors. Our objective of this study was to determine the toxicity of fire-retardant chemicals to fathead minnows during exposure in experimental outdoor streams. METHODS: Stream tests were conducted to determine the potential toxicity of a pulse of exposure as might occur when fire retardant chemical is rinsed from the watershed by rainfall. Two artificial 55-meter experimental streams were dosed with different concentrations of Fire-Trol GTS-R, or uncontaminated for a control. Replicate groups of fathead minnows were added to screened containers (10 fish per container) and exposed to retardant chemicals in the recirculating flow of the stream for up to 6 hours. RESULTS AND DISCUSSION: Under field conditions toxicity of GTS-R only occurred in the presence of sunlight. When GTS-R was tested on sunny days, 100% mortality occurred. However, when tested during heavily overcast conditions, no mortality occurred. CONCLUSIONS: Lethal concentrations of cyanide were measured when GTS-R with YPS exposures were conducted under sunny conditions, but not under cloudy conditions, indicating that a minimum UV level is necessary to induce toxicity as well as the release of cyanide from YPS. The toxicity observed with GTS-R was likely associated with lethal concentrations of cyanide. Rainwater runoff following applications of this fire-retardant at the recommended rate could result in lethal concentrations in small ponds and streams receiving limited water flow under sunny conditions. RECOMMENDATIONS AND OUTLOOK: In addition to avoiding application to aquatic habitats, it is important to consider characteristics of the treated site including soil binding affinity and erosive properties.