Environmental samples can include any physical matrix that might have been contaminated as a result of a chemical being released. Common samples collected supporting a risk assessment include:
- Dust (e.g., from inside buildings)
- Animal tissue (fish, chicken, ducks, crabs, snails)
- Vapor (if applicable)
Environmental samples provide two types of exposure information (Health Canada 2004):
- The magnitude of chemical concentration in individual samples; and
- The geographical extent of the contamination (i.e., how far from the original source has the chemical traveled? And what is the total spatial area contaminated?)
Both the magnitude and extent are used to formulate the exposure scenario and to calculate the overall exposure level. In some cases, concentrations in one matrix are estimated from another. For instance, contaminant concentrations in groundwater or food items can be estimated from soil concentrations. Contaminant Transport/Transfer Models are utilized for these calculations (Health Canada 2004).
Contaminant Transport/Transfer Models
Models may be necessary to estimate the concentrations of contaminants in groundwater, surface water, air, fruits, vegetables, fish, meat or other environmental media through which receptors may be exposed. If used for a Preliminary Quantitative Risk Assessment (PQRA), mass transfer models should be fairly simple.
Concentrations of Contaminants of Potential Concern (COPC) in groundwater and in surface water may be obtained from the methods described by the Canadian Councils of Ministers of the Environment (CCME 1996). For estimating COPC concentrations in fruits or vegetables, methods presented by the CCME (1996) or the Oak Ridge National Laboratory (ORNL) (1998) may be used.
For estimating COPC concentrations in fish and wildlife, simple bioaccumulation/ biomagnification factors may be used (Health Canada 2004). More complicated modelling is usually not necessary, but may be used in a more detailed preliminary qualitative risk assessment.
For more information on properly collecting environmental samples, go to the Field Sampling Procedures section of the toolkit.