Environmental Quality Guidelines are concentration limits for contaminants or environmental quality characteristics (such as dissolved oxygen or pH) that if exceeded, may affect humans or the environment (CCME 2006). For the POPs Toolkit, the CCME Environmental Quality Guidelines for the protection of human health have been recommended as the principle guidelines for screening purposes.
Like many environmental quality guidelines, the CCME Guidelines are generally based on scientific studies in which animals were exposed to the contaminant in question at various concentrations until a toxic effect was observed. If an animal study is used to represent potential effects to humans, a scaling factor accounting for difference in body weight is used. In addition, safety factors are applied to account for uncertainty, such as the relative sensitivity of animals and humans to a contaminant (CCME 2006).
In the case of guidelines protective of human health, once scaling and safety factors have been taken into consideration, the guideline is calculated from the toxicological reference value (TRV). This is the highest total daily dose or concentration of a given chemical that is considered to not cause a toxic effect in humans when exposed over a lifetime. Guidelines are back calculated from the TRV, by making a number of assumptions about possible exposure scenarios and uptake efficiencies (CCME 2006).
The CCME guidelines provide guidelines addressing most potential exposure scenarios. However CCME does not provide guidelines specific to potential contaminated groundwater exposure.
For contaminants in groundwater, the following screening approaches are recommended, depending on the potential exposure route:
- If the groundwater may be used for drinking water purposes, the Health Canada Guidelines for Canadian Drinking Water Quality (http://www.hc-sc.gc.ca/hecs-sesc/water/index.htm) should be used for screening of COPCs.
- If the groundwater is not used for drinking but may be used for other purposes, then the CCME water quality guidelines that best matches the intended purpose (e.g., livestock watering or to protect aquatic life etc.) should be used (Water Quality Guidelines CCME 2006).
- If the groundwater flows into a stream, lake or pond, it is often assumed that the groundwater will undergo a 10x dilution before discharging. Therefore for screening purposes, it is reasonable to screen groundwater concentrations in this scenario against CCME water quality criteria (for the protection of aquatic life) which have been multiplied by 10.
Additional Documentation and Data
For soil samples, the depth at which samples were collected should be indicated. A map of sampling locations is often helpful to determine if the collected samples reflect the distribution of contaminants across the entire property or just specific areas (Health Canada 2004).
For groundwater, the depth of the water table, flow direction, and travel time are useful data to document.