Comparative Toxicity of Seven Aqueous Film-Forming Foam to In Vitro Systems and Mus.

The comparative toxicity of six per- and polyfluoroalkyl substance (PFAS)-free and one PFAS-containing aqueous film-forming foam (AFFF) was evaluated in an outbred mouse species as well as several in vitro assays. The in vivo toxicological profile of PFAS-free AFFFs in short-term, high-concentration exposures is different than that of a PFAS-containing AFFF. The PFAS-containing reference product induced increased liver weights, while the PFAS-free AFFFs were linked to either decreased or unaffected relative liver weights. The in vitro toxicological profile across PFAS-free AFFFs was uniform except in the Microtox® assay, where thresholds were variable and spanned several orders of magnitude. This direct comparison of products through short-term toxicity tests and in vitro screenings represents early data to support evaluation of potential regrettable substitutions when selecting alternative PFAS-free AFFFs. Further work in diverse taxa (e.g., aquatic organisms, terrestrial invertebrates, birds) and mammalian studies capturing sensitive life stages will refine and expand this data set across a range of risk-relevant toxicological endpoints. Environ Toxicol Chem 2023;42:2364-2374. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

In vitro and in vivo effects of 5-aminotetrazole (5-AT), an energetic compound.

Perchlorate is an important oxidizer used in propellants, pyrotechnics, and as a gas generator in commercial airbags, fireworks, and roadside flares. It is highly water soluble, interferes with thyroidal iodide uptake and is an environmental contaminant. By changing the reaction chemistry, 5-aminotetrazole (5-AT) and nitrates replace perchlorate in some propellants. The short term toxicity of 5-AT was evaluated. Using a modified Ames assay, 5-AT was not mutagenic with or without S9 metabolic activation. 5-AT was considered "slightly toxic" with an EC50 of 28.8 mg 5-AT/L for a 15 min exposure in Aliivibrio fischeri. In the in vitro sodium iodide symporter test, 5-AT did not inhibit the uptake of iodine. In the acute rat oral test, no adverse effects and no mortalities were observed at the limit dose of 2000 mg 5-AT/kg. In the 14-day sub-acute study, there were no clinical signs of toxicity or morbidity up to 623 mg 5-AT/kg-day; the highest dose tested. No differences were observed in hematology, clinical chemistry, organ weight, body weight, food consumption, histopathology, or DNA damage (peripheral blood micronucleus assay) of treatments compared with controls. The No Observed Adverse Effect Level (NOAEL) was 623 mg 5-AT/kg-day, the highest dose in the subacute oral bioassay.

Morbidity and mortality resulting from acute inhalation exposures to hydrogen fluoride and carbonyl fluoride in rats.

OBJECTIVE: Experiments were undertaken to compare morbidity and mortality from brief inhalation exposures to high levels of hydrogen fluoride (HF) and carbonyl fluoride (COF2). METHODS: Rats from both sexes were exposed for durations of 5 and 10 min to nominal concentrations of 10,000 to 57,000 ppm HF or 500 to 10,000 ppm COF2. Respiration was monitored before, during, and after exposure. Animals were observed up to 6 days post-exposure. Terminal blood samples were collected for routine clinical chemistry and hematology. Post-mortem lung fluoride concentrations and lung weights were measured, and gross pathology noted. RESULTS: Both gases produced respiratory depression independent of concentration or exposure duration with minute ventilation decreasing to approximately 50% of baseline. Estimated mixed-gender HF and COF2 10-min LC50's were 48,661 ppm and 1083 ppm, respectively. HF mortalities were generally delayed 3 to 4 days post-exposure, while COF2 mortalities occurred during or briefly after exposure. Lung fluoride levels increased with COF2 dose, though elevated lung weights occurred only at the mid-level exposures. Lung weights were unaffected in the HF-exposed animals, and their lung fluoride concentrations were variable. Clinical chemistry and hematology had few consistent trends with the exception of hemoconcentration primarily in HF-exposed males. These short-term exposure experiments conclude that COF2 is nearly 45 times more lethal than HF in rats. CONCLUSIONS: These experiments suggest that hydrolysis to HF cannot solely explain COF2 toxicity. Although HF and COF2 may have common injury mechanisms, they are expressed to markedly different degrees and temporal occurrence.

Multiple environmental stressors elicit complex interactive effects in the western fence lizard (Sceloporus occidentalis).

Evaluation of multiple-stressor effects stemming from habitat degradation, climate change, and exposure to chemical contaminants is crucial for addressing challenges to ecological and environmental health. To assess the effects of multiple stressors in an understudied taxon, the western fence lizard (Sceloporus occidentalis) was used to characterize the individual and combined effects of food limitation, exposure to the munitions constituent 2,4,6-trinitrotoluene (TNT), and Plasmodium mexicanum (lizard malaria) infection. Three experimental assays were conducted including: Experiment I--TNT × Food Limitation, Experiment II--Food Limitation × Malaria Infection, and Experiment III--TNT × Malaria Infection. All experiments had a 30 day duration, the malaria treatment included infected and non infected control lizards, food limitation treatments included an ad libitum control and at least one reduced food ration and TNT exposures consisting of daily oral doses of corn oil control or a corn oil-TNT suspension at 5, 10, 20, 40 mg/kg/day. The individual stressors caused a variety of effects including: reduced feeding, reduced testes mass, anemia, increased white blood cell (WBC) concentrations and increased mass of liver, kidney and spleen in TNT exposures; reduced cholesterol, WBC concentrations and whole body, testes and inguinal fat weights given food limitation; and increased WBC concentrations and spleen weights as well as decreased cholesterol and testes mass in malaria infected lizards. Additive and interactive effects were found among certain stressor combinations including elimination of TNT-induced hormesis for growth under food limitation. Ultimately, our study indicates the potential for effects modulation when environmental stressors are combined.

Toxic effects of oral 2-amino-4,6-dinitrotoluene in the Western fence lizard (Sceloporus occidentalis).

The compound 2-amino-4,6-dinitrotoluene (2A-DNT) was evaluated under laboratory conditions in the Western fence lizard (Sceloporus occidentalis) to assess the potential for reptile toxicity. Oral LD(50) values were 1406 and 1867 mg/kg for male and female lizards, respectively. Based on responses from a 14-day subacute study, a 60-day subchronic experiment followed where lizards were orally dosed at 0, 5, 15, 20, 25, 30 mg/kg-d. At day 60, number of days and survivors, food consumption, and change in body weight were inversely related to dose. Signs of toxicity were characterized by anorexia and generalized cachexia. Significant adverse histopathology was observed in hepatic tissue at ≥ 15 mg/kg-d, consistent with hepatocellular transdifferentiation. Based on survival, loss of body weight, diminished food intake, changes in liver, kidney, and testes, and increased blood urea nitrogen, these data suggest a LOAEL of 15 mg/kg-d and a NOAEL of 5 mg/kg-d in S. occidentalis.

Acute, subacute, and subchronic exposure to 2A-DNT (2-amino-4,6-dinitrotoluene) in the northern bobwhite (Colinus virginianus).

2-Amino-4,6-dinitrotoluene (2A-DNT) is a metabolite of the explosive 2,4,6-trinitrotoluene (TNT) which is present in the soil at numerous U.S. Army installations as the result of TNT manufacture or training activities. Although many avian species are known to inhabit areas where 2A-DNT has been found in the environment, no published studies of the effects of 2A-DNT exposure in birds are available. In this study, we conducted an evaluation of the oral toxicity of 2A-DNT in a representative ground foraging species of management concern, the northern bobwhite (Colinus virginianus). Subacute (14 days) and subchronic (60 days) oral gavage exposure studies were conducted following determination of the median acute lethal dose (LD50 = 1167 mg/kg). In the subacute study, survival occurred at 50 mg/kg/day. This helped to determine dose groups for the subchronic study: 0, 0.5, 3, 14, and 30 mg 2A-DNT/kg body weight-d in corn oil. The lowest observed adverse effects level (LOAEL) was determined to be 14 mg/kg/day based on mortality, and the no observed adverse effects level (NOAEL) was determined to be 3 mg/kg/day based on lack of effects at this exposure level.

Toxicological responses of red-backed salamander (Plethodon cinereus) exposed to aged and amended soils containing lead.

The use of lead in military and civilian small arms projectiles is widely acknowledged to have resulted in high soil lead concentrations at many small arms ranges. These ranges are often adjacent to wildlife habitat or have become habitat when no longer used. To assess the potential toxicity of lead to terrestrial amphibians in contaminated areas, we exposed 100 red-backed salamanders (Plethodon cinereus) to either a control soil or one of four soil treatments amended with lead acetate for 28 days. Analytical mean soil concentrations were 14 (control), 553, 1700, 4700, and 9167 mg Pb/kg soil dry weight. An additional 60 salamanders were also exposed for 28 days to one of six field-collected soil samples from a small arms range and a skeet range. The field soil concentrations ranged from 11 (background) to 16,967 mg Pb/kg soil dry weight. Food consisted of uncontaminated flightless Drosophila melanogaster. Salamander survival was reduced in amended soil treatments of 4700 and 9167 mg/kg by 15% and 80%, respectively. Inappetence was observed at 4700 and 9167 mg/kg and growth decreased in the 9167 mg/kg treatment. Total white blood cells decreased 32% at 4700 mg/kg compared to controls and were 22% lower in the 9167 mg/kg treatment. In contrast, survival was 100% for all field-collected soils with no hematological effects. At 16,967 mg/kg there was evidence of soil avoidance and decreased growth. These data suggest marked differences in toxicity and bioavailability of the lead-amended soil in contrast to the field-collected soil containing lead.

Toxicity of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in three vertebrate species.

The explosive, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine or high-melting explosive (HMX), has been found in soils in areas used for testing and training by the military. Many of these areas contain habitat for valued wildlife species. In an effort to better understand the environmental consequences from exposure, a reptilian (western fence lizard [Sceloporus occidentalis]), an amphibian (red-backed salamander [Plethodon cinereus]), and a mammalian species (rabbit [Oryctolagus cuniculus]) were exposed to HMX under controlled laboratory conditions. Lizards and rabbits were exposed to HMX by way of corn oil through gavage, and salamanders were exposed to HMX in soil. Two deaths occurred from acute oral exposures to lizards to 5000 mg HMX/kg BW. Histological and gross pathologic assessment suggested gut impaction as a possible cause of death. Salamanders exposed to concentrations of HMX in soil < or = 1970 mg HMX/kg soil for 10 days did not show adverse effects. Rabbits, however, showed neurologic effects manifested as hyperkinetic events with convulsions at > 24 h after oral exposures. An LD(50) for rabbits was calculated as 93 mg/kg (95% confidence interval 76-117). A subacute 14-day testing regime found a lowest observed effect level of 10 mg/kg-d and a no observed adverse effect level of 5 mg/kg-d based on hyperkinesia and seizure incidence, although changes suggesting functional hepatic alterations were also found. These data suggest that physiologic differences between species, particularly in gastrointestinal structure and function, can affect the absorption of HMX and hence lead to marked differences in toxicity from exposure to the same compound.

Effects of inorganic lead on Western fence lizards (Sceloporus occidentalis).

Although anthropogenic pollutants are thought to threaten reptilian species, there are few toxicity studies on reptiles. We evaluated the toxicity of Pb as lead acetate to the Western fence lizard (Sceloporus occidentalis). The acute lethal dose and sub-acute (14-day) toxicity studies were used to narrow exposure concentrations for a sub-chronic (60-day) study. In the sub-chronic study, adult and juvenile male lizards were dosed via gavage with 0, 1, 10 and 20 mg Pb/kg-bw/day. Mortality was limited and occurred only at the highest dose (20 mg Pb/kg-bw/d). There were statistically significant sub-lethal effects of 10 and 20 mg Pb/kg-bw/d on body weight, cricket consumption, organ weight, hematological parameters and post-dose behaviors. Of these, Pb-induced changes in body weight are most useful for ecological risk assessment because it is linked to fitness in wild lizard populations. The Western fence lizard is a useful model for reptilian toxicity studies.

Physiologically based pharmacokinetic modeling of cyclotrimethylenetrinitramine in male rats.

A physiologically based pharmacokinetic (PBPK) model for simulating the kinetics of cyclotrimethylene trinitramine (RDX) in male rats was developed. The model consisted of five compartments interconnected by systemic circulation. The tissue uptake of RDX was described as a perfusion-limited process whereas hepatic clearance and gastrointestinal absorption were described as first-order processes. The physiological parameters for the rat were obtained from the literature whereas the tissue : blood partition coefficients were estimated on the basis of the tissue and blood composition as well as the lipophilicity characteristics of RDX (logP = 0.87). The tissue : blood partition coefficients (brain, 1.4; muscle, 1; fat, 7.55; liver, 1.2) obtained with this algorithmic approach were used without any adjustment, since a focused in vitro study indicated that the relative concentration of RDX in whole blood and plasma is about 1 : 1. An initial estimate of metabolic clearance of RDX (2.2 h(-1) kg(-1)) was obtained by fitting PBPK model simulations to the data on plasma kinetics in rats administered 5.5 mg kg(-1) i.v. The rat PBPK model without any further change in parameter values adequately simulated the blood kinetic data for RDX at much lower doses (0.77 and 1.04 mg (-1) i.v.), collected in this study. The same model, with the incorporation of a first order oral absorption rate constant (K(a) 0.75 h(-1)), reproduced the blood kinetics of RDX in rats receiving a single gavage dose of 1.53 or 2.02 mg kg(-1). Additionally, the model simulated the plasma and blood kinetics of orally administered RDX at a higher dose (100 mg kg(-1)) or lower doses (0.2 or 1.24 mg kg(-1)) in male rats. Overall, the rat PBPK model for RDX with its parameters adequately simulates the blood and plasma kinetic data, obtained following i.v. doses ranging from 0.77 to 5.5 mg kg(-1) as well as oral doses ranging from 0.2 to 100 mg kg(-1).

Sublethal effects of subacute exposure to RDX (1,3,5-trinitro-1,3,5-triazine) in the northern bobwhite (Colinus virginianus).

Northern bobwhite (Colinus virginianus) were orally exposed via gavage to 0, 0.5, 3, 8, 12, or 17 mg/kg of RDX (1,3,5-trinitro-1,3,5-triazine) in corn oil daily for 14 d to evaluate sublethal effects of this explosive in birds. Mortality occurred at a rates of 100, 67, and 25% for the 17, 12, and 8 mg/kg/d dose groups, respectively. Death was preceded by clonic and tonic convulsions and weight loss caused by gastrointestinal effects. Increases in serum globulin and total leukocytes were observed in the two highest-dose groups. Degeneration of testicular and splenic tissue also was observed. The no-observed-adverse-effects and lowest-observed-adverse-effects levels were determined as 3.0 and 8.0 mg/kg/d, respectively.

Toxicological responses of red-backed salamanders (Plethodon cinereus) to soil exposures of copper.

Copper (Cu) has widespread military use in munitions and small arms, particularly as a protective jacket for lead projectiles. The distribution of Cu at many US military sites is substantial and sites of contamination include habitats in and around military storage facilities, manufacturing, load and packing plants, open burning/open detonation areas, and firing ranges. Some of these areas include habitat for amphibian species, which generally lack toxicity data for risk assessment purposes. In an effort to ascertain Cu concentrations in soil that are toxic to terrestrial amphibians, 100 red-backed salamanders (Plethodon cinereus) were randomly sorted by weight, assigned to either a control soil or one of four treatments amended with copper acetate in soil, and exposed for 28 days. Analytical mean soil concentrations were 18, 283, 803, 1333, and 2700 mg Cu/kg soil dry weight. Food consisted of uncontaminated flightless Drosophila melanogaster. Survival was reduced in salamanders exposed to 1333 and 2700 mg/kg by 55% and 100%, respectively. Mortality/morbidity occurred within the first 4 days of exposure. These data suggest that a Cu soil concentration of and exceeding 1333.3 +/- 120.2 mg/kg results in reduced survival, whereas hematology analyses suggest that a concentration of and exceeding 803.3 +/- 98.4 mg/kg might result in reduced total white blood cell count. No effects were observed at 283.3 +/- 36.7 mg/kg.

Toxic effects of oral hexahydro-1,3,5-trinitro-1,3,5-triazine in the western fence lizard (Sceloporus occidentalis).

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has been widely used as an explosive in munition formulations, resulting in contamination of wildlife habitat on military installations. To estimate health effects for reptilian species, acute, subacute, and subchronic oral toxicity studies were conducted using the Western fence lizard (Sceloporus occidentalis). Estimated oral median lethal doses were 72 (95% confidence interval [CI], 49-106) mg/kg body weight (slope, 3.754) for males and 88 (95% CI, 65-119) mg/kg (slope, 4.525) for females. Toxicity from RDX suggested the neurological system as the critical target tissue. A 14-d subacute study followed with males dosed orally with RDX (corn oil) at 0, 10, 20, 25, 30, 45, and 60 mg/kg/d. Signs of toxicity frequently included a characteristic body posture. A significant dose-survival relationship was seen over the range of doses, with a significant decrease in survival at 20 mg/kg/d. Males in the 60-d subchronic study were dosed at 0, 1, 2.5, 5, 8, and 11 mg/kg/d, and signs of toxicity included lethargy, cachexia, and anorexia. Survival was decreased at 8 and 11 mg/kg/d. Reduced growth rate and food consumption occurred at 5 mg/kg/d. Brain tissue was assayed for RDX when seizures were observed at a residue concentration of at least 18 microg/g. No abnormalities were observed in the hematologic indices, whereas plasma proteins were reduced. Hepatic enlargement and decreased testes mass occurred at 8 and 11 mg/kg/d. Plasma testosterone concentrations, sperm counts, and motility measures were variable for all treatment levels. Based on survival, growth rate, food intake, and testes to brain weight ratios, these data suggest a lowest-observed-adverse effect level of 5 mg/kg/d and a no-observed-adverse effect level of 2.5 mg/kg/d.

Toxicity of oral exposure to 2,4,6-trinitrotoluene in the western fence lizard (Sceloporus occidentalis).

Contamination of the soil with the explosive 2,4,6-trinitrotoluene (TNT) has been found at military sites, many of which are habitats used by reptiles. To provide data useful in assessing ecological risk for reptilian species, acute, subacute, and subchronic oral toxicity studies were conducted with the western fence lizard (Sceloporus occidentalis). Oral median lethal dose (LD50) values for TNT in corn oil were 1,038 and 1,579 mg/kg of body weight for male and female lizards, respectively. Overt signs of toxicity included chromaturia, abdominal enlargement, and tremors. A 14-d subacute study followed in which male lizards were orally dosed with TNT (corn oil) at 0, 33, 66, 132, 263, 525, and 1,050 mg/kg of body weight each day. Clinical signs of toxicity, while similar to the LD50 study, were more subtle and noted in lizards receiving TNT amounts of at least 66 mg/kg/d. Chromaturia was an early consistent sign, often preceding the onset of adverse effects. Male lizards in the 60-d subchronic study were dosed at 0, 3, 15, 25, 35, and 45 mg/kg/d with nearly complete survival (>90%) for lizards in all treatments. Changes in food consumption and body weight were observed at 35 and 45 mg/kg/d. Alterations in hematological end points; blood chemistries (albumin, total protein, alkaline phosphatase, calcium); kidney, spleen, and liver weights; and adverse histopathology were observed in lizards exposed at 25 to 45 mg/kg/d. Testosterone concentration, sperm count, and motility were variable between treatments. Although not significant, incidences of hypospermia and testicular atrophy were observed in some individuals. Together, these data suggest a lowest-observed-adverse effect level of 25 mg/kg/d and a no-observed-adverse effect level of 15 mg/kg/d in S. occidentalis.

Dose-related effects following oral exposure of 2,4-dinitrotoluene on the Western fence lizard, Sceloporus occidentalis.

2,4-dintitrotoluene (2,4-DNT) is an explosive frequently found in the soil of military installations. Because reptiles can be common on these sites, ecological risk assessments for compounds such as 2,4-DNT could be improved with toxicity data specific to reptiles. Western fence lizards, Sceloporus occidentalis, were used to develop a laboratory toxicity model for reptiles. A hierarchical approach was used; acute to subchronic studies were conducted to provide toxicity data relevant to short- and long-term exposures. First, a modified median lethal dose (LD50) study was conducted on male and female lizards using a stage-wise probit model. The LD50 was 577 mg/kg for female and 380 mg/kg for male lizards. Subsequently, a subacute experiment was conducted to further assess 2,4-DNT toxicity to male lizards and to define exposure levels for a longer term, subchronic study. The subchronic study was conducted for 60 consecutive days; male lizards were exposed to 0, 9, 15, 25, 42, 70 mg/kg/d. Dose-dependent mortality was observed in the three highest dose groups (25, 42, and 70 mg/kg/d); all other animals survived the study duration. Benchmark dose model calculations based on mortality indicated a 5% effect level of 15.8 mg/kg/d. At study termination, a gross necropsy was performed, organ weights were taken, and blood was collected for clinical and hematological analysis. Body weight, kidney weight, food consumption, postdose observations, and blood chemistries all were found to be significantly different from controls at doses above 9 mg/kg/d. Also, preliminary results suggest behavioral observations, and reduced food consumption may be a sensitive indicator of toxicity. The present study indicates Sceloporus occidentalis is suitable for evaluating toxicity of compounds to reptilian species.

Effects of subchronic exposure to 2,6-dinitrotoluene in the northern bobwhite (Colinus virginianus).

Explosives and their breakdown products are commonly found in soils at U.S. military installations. Many areas where these compounds are found represent useful habitat for ground-foraging birds. Because these birds likely are exposed to such compounds, we evaluated the oral toxicity of 2,6-dinitrotoluene (DNT) in a representative ground-foraging species of management concern. Adult male and female northern bobwhite (Colinus virginianus) were exposed to either 0, 5, 10, 40, or 60 mg/kg/d via gavage for 60 d (subchronic) following determination of the median acute lethal dose (320 mg/kg). Circulating levels of red blood cells and hemoglobin were significantly decreased in a dose-dependent manner; however, levels remained within normal ranges. Plasma concentrations of total protein, albumin, globulin, aspartate aminotransferase, and potassium, sodium, and chlorine ions were significantly decreased, and circulating levels of uric acid were significantly increased. Decreased body weight, enlarged gallbladders, edematous gastrointestinal tracts, pale kidneys, pale and fibrous livers, and loose stools were consistent observations. The effects found in the clinical chemistries taken together with histopathological abnormalities observed in sections of hepatic and renal tissue suggest that the liver and kidneys are major targets for 2,6-DNT. Oral exposures to 2,6-DNT appear to affect northern bobwhite in a manner similar to that of the other main DNT isomer, 2,4-DNT, but in more subtle ways, adversely affecting the gastrointestinal system and leading to diarrhea and, ultimately, emaciation. The lowest-observed-adverse-effect level is 40 mg/ kg/d based on hematological measures, and the no-observed-adverse-effect level is 10 mg/kg/d based on the absence of results indicative of adverse effects.

Subacute toxicity of oral 2,6-dinitrotoluene and 1,3,5-trinitro-1,3,5-triazine (RDX) exposure to the northern bobwhite (Colinus virginianus).

Military activities associated with training have resulted in soil residues of munition compounds and their breakdown products. Often, these areas are valuable habitats used by birds. To evaluate the possibility of adverse effects in birds, the effects from oral exposures of 2,6-dinitrotoluene (2,6-DNT) and 1,3,5-trinitro-1,3,5-triazine (RDX) were tested using a controlled dosing regime in northern bobwhite (Colinus virginianus). Nine groups of birds of mixed sex received either corn oil or 50, 100, 190, or 350 mg 2,6-DNT/kg body weight/d or 20, 80, 125, or 180 mg RDX/kg body weight/d mixed in corn oil via gavage for 14 d. Etiology of disease was markedly different between compounds. Increased RDX exposure caused an inverse relationship to time of death, symptoms including clonic followed by tonic convulsions, and death shortly thereafter. Brain concentrations of RDX postmortem, however, were relatively consistent (mean +/- standard error, 20.5 +/- 2.9 mg/kg tissue). Observations of 2,6-DNT effects included gastrointestinal distress, dehydration, and a reduction in body mass and feed consumption. Together, these data suggest that RDX is more toxic from short, repeated exposures than 2,6-DNT, resulting in central nervous system-related effects, whereas 2,6-DNT causes gastrointestinal disturbances at higher exposures.

Perchlorate inhibition of iodide uptake in normal and iodine-deficient rats.

Perchlorate-induced inhibition of thyroidal iodide uptake was measured in normal and iodine-deficient female Sprague-Dawley rats. Rats that were made iodine-deficient by long-term restriction of iodine in the diet absorbed a gavage dose of 131I to the thyroid in proportionally greater amounts than rats fed a normal diet. Furthermore, the iodine-deficient rats maintained their high rates of absorption even when challenged by levels of perchlorate in their drinking water sufficient to produce pronounced inhibition of 131I uptake in rats fed a normal diet. Every dose of perchlorate used in this study (1.1, 5.6, and 28 mg/L) produced significant inhibition of iodide uptake in normally fed rats, but only the highest level of perchlorate (28 mg/L) significantly inhibited thyroidal uptake of 131I in the iodine-deficient rats. Taken together, these results demonstrate that iodide-deficient animals exhibit increased resistance to the inhibition of iodine absorption resulting from perchlorate exposure.

Toxicological responses of red-backed salamanders (Plethodon cinereus) to subchronic soil exposures of 2,4-dinitrotoluene.

Dinitrotoluenes are used as propellants and in explosives by the military and as such have been found at relatively high concentrations in the soil. To determine whether concentrations of 2,4-dinitrotoluene (2,4-DNT) in soil are toxic to amphibians, 100 red-backed salamanders (Plethodon cinereus) were exposed to either 1500, 800, 200, 75 or 0mg 2,4-DNT/kg soil for 28 days and evaluated for indicators of toxicity. Concentrations of 2,4-DNT were less than targets and varied with time. Most salamanders exposed to concentrations exceeding 1050 mg/kg died or were moribund within the first week. Salamanders exposed to soil concentrations exceeding 345 mg/kg lost >6% of their body mass though no mortality occurred. Overt effects included a reduction in feed consumption and an increase in bucco-pharyngeal oscillations in salamanders. These results suggest that only high soil concentrations of 2,4-DNT have the potential to cause overtly toxic effects in terrestrial salamanders.

Responses of oral 2,4,6-trinitrotoluene (TNT) exposure to the common pigeon (Columba livia): a phylogenic and methodological comparison.

Considerable concentrations of the explosive, 2,4,6-trinitrotoluene (TNT) have been found in the soil at many installations where explosives have been used, manufactured, assembled, or destroyed. To evaluate risk to avian receptors, measures of exposure are compared with a threshold level of sublethal toxicity. To date, a single feeding study has evaluated the responses of oral TNT exposure to birds with equivocal results regarding sublethal effects. The present study followed a controlled dosing regime comprising four dose groups and a control (200, 120, 70, 20, and 0 mg TNT/kg body weight [bw]-day) in the common pigeon (Columba livia) for 60 days. Overt signs of toxicity occurred with both sexes between 2 and 3 weeks of exposure. Signs included weight loss, neuromuscular effects (e.g., ataxia, tremors, etc.), and scant red feces (chromaturia). Emetic events following dosing were common and proportional to dose; however, attempts to quantify vomitus compound concentration suggests that birds were marginally successful at removing TNT following administration. Eight of 12 and 2 of 12 males and females died or were moribund in the 200 and 120 mg/kg-day groups, respectively. Changes in hematological parameters, liver, kidney, and ovary weights were related to treatment. Dose-related changes in plasma albumin and sodium concentrations were also observed. These results suggest that subchronic exposure to TNT can adversely affect the central nervous system and hematological parameters in birds. Chemical analysis of blood detected concentrations of the two primary reduction metabolites, but not parent compound, suggesting that toxicity may be due to the bioaccumulation of a toxic intermediate.