M3 AM Ecological Risk Assessment (Part 1)
Monday, 14 November 2005: 8:00 AM - 11:40 AM in Ballroom 3

(ARN-1117-740007) A screening level risk assessment model for chemical fate and effects in the environment.

Arnot, J¹, Mackay, D¹, Webster, E¹, Southwood, J², ¹ Trent University, Peterborough, ON, Canada² Golder Associates, Ottawa, ON, Canada

ABSTRACT- A screening level risk assessment model is developed and described that seeks to assess and prioritise chemicals by estimating environmental fate and transport, bioaccumulation and exposure to humans and wildlife for a unit emission rate to identify the most sensitive risk endpoint. A critical emission rate is then calculated as a result of that endpoint being reached. Finally, an estimated emission rate is compared with the critical emission rate as a risk assessment factor. This "back tracking" process avoids the use of suspect emission rate data as model input. To illustrate its applicability the model is applied to four chemicals for detailed discussion and to a group of 70 chemicals drawn from the Canadian Domestic Substances List. It is shown that both the simple Level II and the more complex Level III models can be used to "bin" substances into categories of similar probable risk. The model brings together information on chemical partitioning, reactivity, environmental fate and transport, bioaccumulation, exposure, objective or effect levels and emission rates in a coherent system for assessing risk at a screening level. It is hoped that the approach may be useful for identifying and prioritising those chemicals of commerce that are of greatest potential concern. Following such an assessment, selected chemicals can be more fully and accurately evaluated using monitoring data in conjunction with models describing chemical fate and effects in more detail in real regional environments and food webs.

Key words: screening level, risk assessment, model, integrated