The ecotoxicological problem of "Dose": from explosives to little bits

Everyone is welcome to attend this CIVE 615 Environmental Engineering Seminar (part of the Environmental & Water resource engineering seminar series) given by Dr. Geoffrey I. Sunahara, Group Leader, Applied Ecotoxicology, National Research Council Canada.

Traditionally, toxicity is associated with the concentration or the mass-based “dose-metric” exposure to the chemical of concern. Dose-metrics are important in establishing a “cause-effect” relationship, which is used in environmental risk assessment to predict potential hazardous effects of environmental exposure at contaminated sites. Examples will be presented on how ecotoxicity data is generated and used for traditional environmental risk assessment. However, the current standard toxicity test guidelines and ecotoxicological risk assessment methods may not be sufficient to address the ecotoxicological concerns of engineered nanomaterials (ENM) that are being released into the environment. There is much uncertainty amongst nano-ecotoxicologists and environmental risk assessors regarding the choice and use of the dose-metric of ENM whose toxicity is determined by concentration, as well as the nano-size of the chemical. The possible adverse effects of exposure to ENM in the environment have attracted the concern of industry, government regulators, as well as the general public. For example, what are the impacts of the release of ENM used in sunscreen lotions and cosmetics on the environment? Recent laboratory studies have shown that exposure to commercial uncoated nano-TiO₂ particles can cause toxic effects in some aquatic and terrestrial organisms. This presentation will include some of our recent findings describing nano-ecotoxicological responses using dose-metric analysis of a widely-used model nano-toxicant such as nano-TiO₂, but whether this or other engineered nano-contaminants have toxic effects in the environment is not known.

Geoffrey Sunahara has more than 25 years of experience in environmental and biochemical toxicology. He has published >80 research articles in well-respected journals and >200 conference proceedings and book chapters. In 1994, Dr. Sunahara established and was made responsible for the Applied Ecotoxicology group at the National Research Council of Canada. Fields of research include the ecotoxicological characterization of recalcitrant soil contaminants such as the energetic substances (TNT, RDX and HMX) and their metabolites using whole organisms and cultured cell approaches. Toxicological information generated by his laboratory is being used in the establishment of soil quality criteria for explosives-contaminated sites used by the Canadian land forces, as well as those of other countries. Recent research interests include the ecotoxicology of nano-materials, biodiesel and selected bioproducts. In his ecotoxicity studies, a major focus is made upon innovation, ecological relevance, risk assessment, and modes of toxicity. These achievements have led to international recognition, as evidenced by the prestigious international 2010 TTCP Scientific Achievement Award. Dr. Sunahara has also collaborated with other experts to assemble and recently publish a comprehensive book on the Ecotoxicology of Explosives (CRC Press).