Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p3
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 3/10)
Character Range: 1446691–1449692

Toxicity data is normalised to a reference soil of 10% organic matter and 25% clay. The equations used to normalise the toxicity data (that is, normalisation equations) are based on the studies by Lexmond et al. (1986) and Van Straalen and Denneman (1989), where background levels of contaminants showed a positive relationship with organic matter and/or clay. Intervention values are designed to protect 50% of the species. In other words, the permitted concentration is hazardous to 50% of species and hence referred to as the HC50. Target values are equal to the HC5 (that is, the concentration that should permit only 5% of species to be affected) divided by 100. This factor 100 is applied to take into account combination toxicity (Crommentuijn 2000a).

If limited toxicity data is available, equilibrium partitioning (EqP) methods are used to derive soil screening values by extrapolation of aquatic toxicity data. If no data is available, the Dutch guidelines use QSARs to estimate toxicity data from contaminants that have the same mechanism of action.

Intervention and target values have been set for 75 contaminants and a further 20 contaminants have target values and/or indicative levels of serious contaminant levels (VROM 2000).

5.1.3         A3:  Canada
The Canadian SQGs were developed by CCME to assess in-place contaminants in soil (CCME 1999, 2006) and can be found at: www.ccme.ca/publications/list_publications.html#link2.

SSQs and the level of protection for terrestrial species and soil processes depend on land use (that is, agriculture, residential/parkland, commercial and industrial sites). Using potential exposure scenarios, ecological receptors that sustain the primary activities for each land use are identified. These include soil invertebrates, soil nutrient cycling processes, plants, wildlife for all four land uses, soil and food ingestion by herbivores and consumers (including biomagnification) for residential and agricultural, and crops and livestock for agricultural land use.

SSQs were derived using laboratory and field-based toxicity data. This data measures the effects that undermine a species' ability to survive and reproduce under normal living conditions for soils that represented typical Canadian soils. The preferred measures of toxicity are 25% effect concentrations (IC25 or EC25). A second option is to use LOECs divided by an uncertainty factor (safety factor) if there is insufficient 25% effect data (SSD method). A third option is to use median effect data (LC50 or EC50) divided by an uncertainty factor (for agricultural and residential/parkland only, not for commercial and industrial sites). Depending on the quantity of toxicity data available, the weight-of-evidence (SSD) approach, LOEC method or median effects method was used to obtain SQGs. SSD was the preferred methodology if sufficient data was available. The output from the SSD might be divided by an uncertainty factor, depending on the type and amount of toxicity data