The Next Generation Blueprint of Computational Toxicology at the U.S. Environmental Protection Agency.

The U.S. Environmental Protection Agency (EPA) is faced with the challenge of efficiently and credibly evaluating chemical safety often with limited or no available toxicity data. The expanding number of chemicals found in commerce and the environment, coupled with time and resource requirements for traditional toxicity testing and exposure characterization, continue to underscore the need for new approaches. In 2005, EPA charted a new course to address this challenge by embracing computational toxicology (CompTox) and investing in the technologies and capabilities to push the field forward. The return on this investment has been demonstrated through results and applications across a range of human and environmental health problems, as well as initial application to regulatory decision-making within programs such as the EPA's Endocrine Disruptor Screening Program. The CompTox initiative at EPA is more than a decade old. This manuscript presents a blueprint to guide the strategic and operational direction over the next 5 years. The primary goal is to obtain broader acceptance of the CompTox approaches for application to higher tier regulatory decisions, such as chemical assessments. To achieve this goal, the blueprint expands and refines the use of high-throughput and computational modeling approaches to transform the components in chemical risk assessment, while systematically addressing key challenges that have hindered progress. In addition, the blueprint outlines additional investments in cross-cutting efforts to characterize uncertainty and variability, develop software and information technology tools, provide outreach and training, and establish scientific confidence for application to different public health and environmental regulatory decisions.

Screening level assessment of risks due to dioxin emissions from burning oil from the BP Deepwater Horizon Gulf of Mexico spill.

Between April 28 and July 19 of 2010, the U.S. Coast Guard conducted in situ oil burns as one approach used for the management of oil spilled after the explosion and subsequent sinking of the BP Deepwater Horizon platform in the Gulf of Mexico. The purpose of this paper is to describe a screening level assessment of the exposures and risks posed by the dioxin emissions from these fires. Using upper estimates for the oil burn emission factor, modeled air and fish concentrations, and conservative exposure assumptions, the potential cancer risk was estimated for three scenarios: inhalation exposure to workers, inhalation exposure to residents on the mainland, and fish ingestion exposures to residents. U.S. EPA's AERMOD model was used to estimate air concentrations in the immediate vicinity of the oil burns and NOAA's HYSPLIT model was used to estimate more distant air concentrations and deposition rates. The lifetime incremental cancer risks were estimated as 6 × 10(-8) for inhalation by workers, 6 × 10(-12) for inhalation by onshore residents, and 6 × 10(-8) for fish consumption by residents. For all scenarios, the risk estimates represent upper bounds and actual risks would be expected to be less.

Structuring factors in a marine soft bottom community during eutrophication-an experiment with radio-labelled phytodetritus.

The quantitative development and uptake of radio-labelled phytodetritus in benthic macro- and meiofauna was studied in a 5-month experiment in two mesocosms, one of which received a single large nutrient (N and P) addition, while the other served as control. In reponse to the 12-fold increase in phytoplankton biomass noted after 2 weeks and the resulting enhanced accumulation of fresh phytodetritus, the abundance and biomass of the polychaetes Mediomastus ambiseta and Polydora ligni and the mud anemone Cerianthiopsis americanus increased significantly in the enriched tank. The abundances of P. ligni and M. ambiseta increased 37-fold and 12-fold, respectively, within the first two months of the experiment. No other macrofaunal or meiofaunal taxa showed any consistent positive quantitative response to the increased input of phytodetritus. In the control tank no considerable change in the benthic community structure was noted. The measurements of radio-label uptake within the benthic fauna showed that the quantitatively most successful species utilized fresh phytodetritus highly. However, a high degree of utilization of fresh detritus was also shown by taxa that did not respond quantitatively within the 5 month of the experiment, and almost all taxa showed a preference for fresh detritus over older organic material. Within the benthic meiofauna, kinorhynchs and especially foraminiferans showed a remarkably low preference for fresh detritus. A budget calculation comparing the total amounts of labelled organic carbon bound in animal tissue and in the sediment indicated that at any time at least 75% of this carbon was available for assimilation by deposit feeders. These results suggest that factors other than the availability of food, such as competition for space by a few opportunistic macrofauna species, limited the response of other species within this benthic community to the increased input of phytodetritus.