The environmental fate of a set of chemicals is calculated using both Level II and Level III equations for a unit emission rate. Environmental persistence and potential for long-range transport are calculated for each chemical. A bioaccumulation food web model calculates the exposure experienced by a variety of wildlife, domestic livestock, and humans. From the specified critical concentrations and an estimated actual total emission rate, a critical emission rate and risk assessment factor are determined.
This screening level risk assessment model is designed to assist in the assessment and prioritization of chemicals by estimating environmental fate and transport, bioaccumulation and exposure to humans and wildlife for a unit emission rate. The most sensitive risk endpoint is identified and a critical emission rate is then calculated as a result of that endpoint being reached in the most vulnerable compartment or species. Finally, an estimated emission rate (provided by the user) is compared with the critical emission rate as a risk assessment factor (RAF). It is suggested that further study focus on those substances that have the highest RAFs. Chemicals in the set are ranked by their RAF.
Although the model will address ionizing substances, its treatment of these substances is very simplistic and the user is cautioned that the estimation of partitioning, reaction and bioaccumulation of the ionic species can be in considerable error. The model is primarily designed to address non-ionizing substances or those which ionize to only a limited extent.
It is hoped that this model will be useful for identifying and prioritizing 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.
For more information on Level II and Level III calculations, refer to the descriptions of the Level II and Level III models.
This program is based on the following publication:
Arnot, J.A., Mackay, D., Webster, E., Southwood, J. M. 2006. A screening level risk assessment model for chemical fate and effects in the environment. Environ. Sci. Technol. 40 (7): 2316 - 2323.
The required input data are:
A comma separated value (.csv) file containing the following data in the order given below and with the restrictions as listed. A maximum size of a chemical set is 252 chemicals. Chemicals may be entered directly into the RAIDAR software but this is not recommended unless the set is very small.
1. There must be exactly 35 columns (A to AI) in the file.
Either the set of Objective Endpoints, or the Effect Endpoint and LogBCF must be entered. If both are available, both may be entered. (When ranking the chemicals, the Objective and Effect endpoints are considered separately.) The Effect endpoint (for all biota) is the critical water concentration (exposure concentration, mg/L) selected by the user and should be chosen consistently for all chemicals in the set to allow a rational comparison of risk. Data not required may be left blank, or a dash (-) may be inserted as a placeholder for the convenience of the viewer.
2. Each chemical must have a new row.
3. The Chemical Name must appear in both the first and last column.
4. The first row must contain the headings for the columns and the chemical data must start on the second row of the file.
5. Blank rows are not permitted.
6. Major modifications to the chemical data should not be done in the RAIDAR model, but should be made in the spreadsheet program of your choice, the file saved in csv format, and imported. The RAIDAR model is designed to handle only minor modifications to the chemical information and will not work well for major changes or additions.
A single set of biota properties are provided in the model. They can not be changed by the user.
For the Level III calculation, the mode-of-entry must be specified, all chemicals in the set will be evaluated using this mode-of-entry.
Model output includes:
Notes on Environmental Properties:
The surface area of each medium is the same for all Levels, however, the depth of soil for the Level III calculations is twice that of the depth for the Level II calculations. For Level III calculations the soil is sub-divided into pore air and water and solids. The solids account for only half of the total soil volume. For Level II calculations the soil is not sub-divided. Thus the factor of two difference in depth is required for the model results to be comparable between Levels. Similarly the sediment is sub-divided into pore water and solids for Level III. Thus the depth of sediment is five times greater for Level III than for Level II to reflect the 20% solid matter used in the Level III standard environments.
Due to the simple nature of the Level II calculations, varying areas and depths would have no effect, provided volumes remained constant. The surface areas are required only for Level III calculations.
The fish volume fraction and the fish lipid content are required here to maintain continuity with previously exisiting CEMC models such as EQC. They modify, very slightly, the total volume and the Z of the water column. The fish lipid content is used to calculate the fish-water partition coefficient (KFW) in the case of a Type 1 chemical, and the octanol-water partition coefficient (from the KFW) in the case of a Type 2 or 3 chemical. They are not used directly in the foodweb calculations.
Minimum system requirements:
Minimum system requirements are an IBM-compatible PC running Windows 98 or XP. This model will not run under Windows NT or 2000.
The screen resolution should a minimum of 800x600 pixels.
CEMC Home | General Information | Models | Experimental Facilities | Atmospheric Chemistry | Graduate Studies | Contact
Last updated June 12, 2013.