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ENVIRONMENT AND HEALTH

For determining an agricultural and a residential/parkland soil guideline it was assumed that the most appropriate receptor to use would be the preschool toddler due to a large exposure per unit mass. In accordance with the CCME guideline derivation procedures (CCME 2005), a preliminary soil quality guideline was derived for three exposure pathways (ingestion, inhalation, and dermal): BSC ETETIRAFSRAFSIRAF BWSFEDITDI PSQG G S SL HH + ×××+×+× − × × = 2 1 [( ])()() [( ) ] where, PSQGHH = preliminary human health soil quality guideline (mg/kg) TDI = tolerable daily intake (6.0 x 10-4 mg/kg bw/d) (Health Canada 1999) EDI = estimated daily intake for the toddler (7.8 x 10-5 mg/kg bw/d) (based on various data – see Table 17) SF = soil allocation factor of 20%, by default (CCME 2005) BW = body weight for toddler (16.5 kg) (CCME 2005) SIR = soil ingestion rate for toddler (8 x 10-5 kg/d) (CCME 2005) -9 IRS = soil inhalation rate for toddler (7.1 x 10 kg/d) [i.e., inhalation rate for toddler = 9.3 m3 /d x suspended soil dust concentration of 7.6 x 10-10 kg/m3 (Health Canada 2003)] SR = soil dermal contact rate for toddler (6.9 x 10-5 kg/d) [hands surface area of 0.043 m2 (CCME 2005) × soil adherence factor of 0.001 kg/m2 /d plus arms/legs surface area of 0.26 m2 (CCME 2005) × soil adherence factor of 0.0001 kg/m2 /d (CCME 2005)] BSC = background soil concentration (2 mg/kg) (NCRP 1984) AFG = relative absorption factor for soil: water in the gut (100%, assumed by default) AFL = relative absorption factor for soil: water in lung tissue (100%, by default) AFS = relative absorption factor for soil: water on skin (5%) (MDEP 1995) ET1 = exposure term 1 (unitless) – days per week/7 x weeks per year/52 at the site (1.0)

[i.e., 7 days per week, 52 weeks per year assumed at the site (CCME 2005)]

ET2 = exposure term 2 (unitless) – hours per day/24 at the site (1.0) [i.e., 24 hours per day assumed at the site (CCME 2005)] The exposure term, ET1 in the above equation, is the ratio of the defined exposure period for each land use to the maximum exposure period (24 hours/day x 365 days/year). Note that hours per day exposure (ET2) is applied to soil inhalation, but is not considered for soil ingestion or dermal contact, consistent with Health Canada (2004) recommendations, since soil ingestion and dermal contact are not expected to occur at a uniform rate throughout the day. The preliminary human health soil quality guideline (PSQGHH) for uranium in agricultural soil was calculated to be 23 mg/kg. For residential/parkland land uses, the PSQGHH was calculated to be 23 mg/kg.