Acute toxicity to rats and trout with a focus on inhalation and aquatic exposures

Due to limitations in toxicity data, extrapolations are often performed within and between species. In this context, median lethal concentration (LC(50)) and dose (LD(50)) for 231 chemicals, along with physicochemical factors, were log-transformed and compared across several exposure routes in rats (i.e., oral, dermal, intraperitoneal, inhalation, intravenous, subcutaneous) and rainbow trout (i.e., aquatic, oral, dermal, intraperitoneal). Molecular weight (MW), octanol-water partition coefficient (K(ow)), vapor pressure (VP), and water solubility (S) were intercorrelated (Bonferroni P<0.05). MW (7 of 10 cases) and K(ow) (3 of 10 cases) were inversely correlated to toxicity endpoints, whereas VP (5 of 10 cases) was positively correlated (Bonferroni P< 0.05). Interspecies correlations were observed in toxicity endpoints over multiple exposure routes (10 of 24 cases), in addition to intraspecies correlations within rat (13 of 15 cases) and within trout (3 of 5 cases) (Bonferroni P<0.05). It was hypothesized that rat inhalation LC(50) and trout LC(50) would be associated, since air and water exposures correspond to each organism's respiratory medium. This hypothesis was supported by their correlation (r=0.68, Bonferroni P<0.05), characterized by a median molar ratio near 1, and further analyzed via regression methods. Comparison of acute toxicity endpoints can, therefore, assist in identifying appropriate extrapolations, likely based on similar toxicokinetics.     

Ecotoxicological study of arsenic and lead contaminated soils in former orchards at the Hanford site,USA

The purpose of this study was to assess ecotoxicity of former orchard soils contaminated with lead arsenate pesticides at the Hanford Site in Washington state (USA). Surface soil, plant, and invertebrate samples were collected from 11 sites in former orchard areas. Mean (standard deviation [SD]) for As and Pb in soil were 39.5 (40.6) and 208 (142) mg/kg dry wt, respectively (n = 11). These concentrations exceeded Hanford background levels but were similar to orchard soils elsewhere. In our study, As and Pb soil concentrations were positively and significantly correlated (r = 0.87, Bonferroni P < 0.05). Speciation of total inorganic As in soil (n = 6) demonstrated that As+5 was the dominant form (>99%). Mean (SD) for As and Pb in cheatgrass were 3.9 (7.9) and 12.4 (20.0) mg/kg dry wt, respectively (n = 11), while mean (SD) for As and Pb in darkling beetles were 5.4 (2.6) and 3.9 (3.0) mg/kg dry wt, respectively (n = 8). Linear regressions were constructed to estimate soil to cheatgrass and soil to darkling beetle uptake for As and Pb. These were significant (Bonferroni P < 0.05) only for cheatgrass versus soil (As) and darkling beetle versus soil (Pb). Standardized lettuce seedling and earthworm bioassays were performed with a subset of soil samples (n = 6). No significant effects (P > 0.05) were observed in lettuce survival or growth nor in earthworm survival or sublethal effects. Based on these bioassays, unbounded no observed effect concentrations (NOECs) in soil for As and Pb were 128 and 390 mg/kg dry wt, respectively. However, our range of soil concentrations generally overlapped a set of ecotoxicological benchmarks reported in the literature. Given uncertainty and limited sampling related to our NOECs, as well as uncertainty in generic benchmarks from the literature, further study is needed to refine characterization of As and Pb ecotoxicity in former orchard soils at the Hanford Site. © 2011 Wiley Periodicals, Inc. Environ Toxicol 29: 10–20, 2014.     

Cardiovascular Reactivity in Type A and B Males to Mental Arithmetic and Aerobic Exercise at an Equivalent Oxygen Uptake

Cardiovascular hyperreactivity (i.e., response in excess of metabolic requirements) to psychological stress has been implicated in the development of coronary heart disease. The purpose of this study was to evaluate cardiovascular hyperreactivity to psychological stress in Type A and B subjects. Fifteen Type A and 15 Type B young men performed mental arithmetic and cycle ergometry tasks. Linear regressions were calculated for each dependent variable during exercise with oxygen uptake serving as the independent variable. All cardiovascular variables were significantly correlated (p less than .0001) with oxygen uptake during exercise. The regression equations obtained during exercise were then used to predict the value of each cardiovascular variable at the oxygen uptake level obtained during mental arithmetic for each person. Repeated measures ANOVA compared responses observed during arithmetic with responses predicted from exercise at an equivalent oxygen uptake in Type A and B subjects. Heart rate, total peripheral resistance, and mean arterial pressure were significantly greater (p less than .0001) and stroke volume was significantly lower (p less than .0002) during arithmetic than during exercise, while Heather index, cardiac output, and arteriovenous oxygen difference did not differ significantly. No significant differences were found between Type A and B males. Results demonstrated that cardiovascular hyperreactivity was equally robust across Type A and B subjects.     

Comparisons of Acute Toxicity of Selected Chemicals to Rainbow Trout and Rats

Median lethal concentration (LC₅₀) and dose (LD₅₀) for 217 chemicals were compared over several exposure routes in rainbow trout and rats. Data were compiled primarily from on-line databases and included octanol–water partition coefficient (K_ow), trout LC₅₀, and trout and rat LD₅₀for oral, dermal, and intraperitoneal (IP) routes.K_owand molar lethality data were log-transformed for correlation and regression analyses. Median ratios (rat oral LD₅₀/trout LC₅₀=156, rat/trout oral LD₅₀= 0.80, rat/trout dermal LD₅₀=0.43, rat/trout IP LD₅₀=0.55) demonstrated the effect of similar versus dissimilar exposure routes on lethality, reflecting toxicokinetic differences. Simple linear regressions revealed significant correlations (BonferroniP<0.05) for trout LC₅₀versus rat oral LD₅₀and for trout LD₅₀versus rat LD₅₀when matched on exposure route. WhenK_owwas included with multiple regression to consider the effect of hydrophilic/lipophilic partitioning on uptake and toxicity, correlations improved only for trout LC₅₀versus rat oral LD₅₀and for trout IP LD₅₀versus rat IP LD₅₀. Stratification of data into pesticides and nonpesticides failed to refine prediction of trout LC₅₀from rat oral LD₅₀. Simple regressions reported here and in the literature relating fish LC₅₀and rat oral LD₅₀exhibited varying degrees of correlation (r=0.26–0.99), reflecting differences in interspecies sensitivity, chemical group evaluated, and experimental methodologies.     

Radiological risk from consuming fish and wildlife to Native Americans on the Hanford Site (USA)

Historical operations at the Hanford Site (Washington State, USA) have released a wide array of non-radionuclide and radionuclide contaminants into the environment. As a result of stakeholder concerns, Native American exposure scenarios have been integrated into Hanford risk assessments. Because its contribution to radiological risk to Native Americans is culturally and geographically specific but quantitatively uncertain, a fish and wildlife ingestion pathway was examined in this study. Adult consumption rates were derived from 20 Native American scenarios (based on 12 studies) at Hanford, and tissue concentrations of key radionuclides in fish, game birds, and game mammals were compiled from the Hanford Environmental Information System (HEIS) database for a recent time interval (1995-2007) during the post-operational period. It was assumed that skeletal muscle comprised 90% of intake, while other tissues accounted for the remainder. Acknowledging data gaps, median concentrations of eight radionuclides (i.e., Co-60, Cs-137, Sr-90, Tc-99, U-234, U-238, Pu-238, and Pu-239/240) in skeletal muscle and other tissues were below 0.01 and 1 pCi/g wet wt, respectively. These radionuclide concentrations were not significantly different (Bonferroni P>0.05) on and off the Hanford Site. Despite no observed difference between onsite and offsite tissue concentrations, radiation dose and risk were calculated for the fish and wildlife ingestion pathway using onsite data. With median consumption rates and radionuclide tissue concentrations, skeletal muscle provided 42% of the dose, while other tissues (primarily bone and carcass) accounted for 58%. In terms of biota, fish ingestion was the largest contributor to dose (64%). Among radionuclides, Sr-90 was dominant, accounting for 47% of the dose. At median intake and radionuclide levels, estimated annual dose (0.36 mrem/yr) was below a dose limit of 15 mrem/yr recommended by the United States Environmental Protection Agency (USEPA), as well as below a dose limit of 100 mrem/yr proposed by the International Commission on Radiation Protection (ICRP). Similarly, lifetime cancer risk (1.7E−5), calculated with median inputs, was below risk levels corresponding to these dose limits. However, our dose and risk estimates apply to only one pathway within a multidimensional exposure scenario for Native Americans. On the other hand, radiation dose and risk corresponding to onsite tissue concentrations were not significantly different from those corresponding to offsite (background) concentrations. Recognizing uncertainties in exposure and toxicity assessments, our results may facilitate informed decision making and optimize resource allocation within a risk assessment framework at the Hanford Site.     

A physiological and nutritional profile of young female figure skaters.

This study was undertaken to develop a physiological and nutritional profile of 13 female figure skaters, aged 9-17 years. Compared with previous published data, skaters in this study were younger and smaller with a higher percent body fat. Skaters in this study were less experienced and trained less than skaters in other studies but attained similar levels of maximal oxygen uptake (VO2max), handgrip strength, and vertical jump power. Relative VO2max (ml/kg/min) was significantly negatively correlated (p less than 0.0033) with body weight and percent body fat, while body weight was significantly positively correlated (p less than 0.0003) with handgrip strength and vertical jump power. In terms of nutritional recommendations, skaters in this study consumed comparatively high amounts of fat and protein with low amounts of carbohydrate, calcium, and iron. Despite suboptimal nutrition and a relatively low training volume, skaters in this study exhibited physiological characteristics similar to those reported for female figure skaters in the literature.