Bejarano A.C.,Research Planning |
Farr J.K.,National Oceanic and Atmospheric Administration
Environmental Toxicology and Chemistry | Year: 2013
Management decisions aimed at protecting aquatic resources following accidental chemical spills into rivers and coastal estuaries require estimates of toxic thresholds derived from realistic spill conditions: acute pulse exposures of short duration (h), information which often is unavailable. Most existing toxicity data (median lethal concentration or median effective concentration) come from tests performed under constant exposure concentrations and exposure durations in the 24-h to 96-h range, conditions not typical of most chemical spills. Short-exposure hazard concentration estimates were derived for selected chemicals using empirical toxicity data. Chemical-specific 5th percentile hazard concentrations (HC5) of species sensitivity distributions (SSD) from individual exposure durations (6-96h) were derived via bootstrap resampling and were plotted against their original exposure durations to estimate HC5s and 95% confidence intervals (CIs) at shorter exposures (1, 2, and 4h). This approach allowed the development of short-exposure HC5s for 12 chemicals. Model verification showed agreement between observed and estimated short-exposure HC5s (r2 adjusted=0.95, p<0.0001), and comparison of estimated short-exposure HC5s with empirical toxicity data indicated generally conservative hazard estimates. This approach, applied to 2 real spill incidents, indicated hazard estimates above expected environmental concentrations (acrylonitrile), and suggested that environmental concentrations likely exceeded short-exposure hazard estimates (furfural). Although estimates generated through this approach were likely overprotective, these were derived from environmentally realistic exposure durations, providing risk-assessors with a tool to manage field decisions. © 2013 SETAC.
Bejarano A.C.,Research Planning |
Barron M.G.,U.S. Environmental Protection Agency
Environmental Toxicology and Chemistry | Year: 2016
Interspecies correlation estimation (ICE) models were developed for 30 nonpolar aromatic compounds to allow comparison of prediction accuracy between 2 data compilation approaches. Type 1 models used data combined across studies, and type 2 models used data combined only within studies. Target lipid (TLM) ICE models were also developed using target lipid concentrations of the type 2 model dataset (type 2-TLM). Analyses were performed to assess model prediction uncertainty introduced by each approach. Most statistically significant models (90%; 266 models total) had mean square errors <0.27 and adjusted coefficients of determination (adj R2) >0.59, with the lowest amount of variation in mean square errors noted for type 2-TLM followed by type 2 models. Cross-validation success (>0.62) across most models (86% of all models) confirmed the agreement between ICE predicted and observed values. Despite differences in model predictive ability, most predicted values across all 3 ICE model types were within a 2-fold difference of the observed values. As a result, no statistically significant differences (p>0.05) were found between most ICE-based and empirical species sensitivity distributions (SSDs). In most cases hazard concentrations were within or below the 95% confidence intervals of the direct-empirical SSD-based values, regardless of model choice. Interspecies correlation estimation-based 5th percentile (HC5) values showed a 200- to 900-fold increase as the log KOW increased from 2 to 5.3. Results indicate that ICE models for aromatic compounds provide a statistically based approach for deriving conservative hazard estimates for protecting aquatic life. © 2016 SETAC.
Badri M.,Research Planning |
Yang G.,Research Planning |
Al Mazroui K.,United Arab Emirates University |
Mohaidat J.,Abu Dhabi Education Council |
And 2 more authors.
Journal of Biological Education | Year: 2016
This study employed the international Relevance of Science Education questionnaire to survey the interest in biology and the out-of-school experiences of Abu Dhabi secondary school students (median age 17, mean age 17.53 and mode age of 16) in the third semester of 2014. It included 3100 participants. An exploratory factor analysis was used to categorise the items for both interest in biology and out-of-school experience. Ten interest in biology and 12 out-of-school experience factors were extracted. The summated means for each factor indicated that ‘health and fitness’ and ‘disease control’ enjoyed highest interests among students. For out-of-school experiences, the two factors of ‘digital applications’ and ‘medical treatment’ received the highest scores. Multivariate analysis of variance revealed that all factors for both interest in biology and out-of-school experience exhibited significant differences between boys and girls. More girls than boys were interested in disease control, reproduction (human biology), alternative science, health and fitness, zoology, and applied cosmetic biology. No significant differences were observed for the remaining five other categories. Furthermore, analysis of variance revealed significant differences between boys and girls with regard to individual items comprising each of the factors. The highest correlations were between the two factors of out-of-school experiences of ‘the natural world’ and ‘learning through observation’ and the interest in biology factor related to ‘plant and animal farming and agriculture’. Results suggested that more emphasis must be placed on students’ out-of-school experience and their engagement in informal learning in contextual outdoor environments to enhance their interest in learning more about biology and the living environment in general. © 2016 Royal Society of Biology
Bejarano A.C.,Research Planning |
Clark J.R.,HDR |
Environmental Toxicology and Chemistry | Year: 2014
Aquatic toxicity considerations are part of the net environmental benefit analysis and approval decision process on the use of dispersants in the event of an offshore oil spill. Substantial information is available on the acute toxicity of physically and chemically dispersed oil to a diverse subset of aquatic species generated under controlled laboratory conditions. However, most information has been generated following standard laboratory practices, which do not realistically represent oil spill conditions in the field. The goal of the present quantitative review is to evaluate the use of standard toxicity testing data to help inform decisions regarding dispersant use, recognizing some key issues with current practices, specifically, reporting toxicity metrics (nominal vs measured), exposure duration (standard durations vs short-term exposures), and exposure concentrations (constant vs spiked). Analytical chemistry data also were used to demonstrate the role of oil loading on acute toxicity and the influence of dispersants on chemical partitioning. The analyses presented here strongly suggest that decisions should be made, at a minimum, based on measured aqueous exposure concentrations and, ideally, using data from short-term exposure durations under spiked exposure concentrations. Available data sets are used to demonstrate how species sensitivity distribution curves can provide useful insights to the decision-making process on dispersant use. Finally, recommendations are provided, including the adoption of oil spill-appropriate toxicity testing practices. Environ Toxicol Chem 2014;33:732-742. © 2014 SETAC.