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CEE 350 - Korshin - Winter 2012 - Homework 5(1)

# CEE 350 - Korshin - Winter 2012 - Homework 5(1) - CEE 350...

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1 CEE 350 Homework 5 Solutions Problem 1 (textbook 4.5) Suppose a 70-kg individual drinking 2 L/day of water containing 0.1 mg/L of 1,1-dichloroethylene for 20 years. a. Find the hazard coefficient for this exposure b. Find the cancer risk c. If the individual drinks this water 30 years instead of just 20, recomputed the hazard coefficient and the cancer risk. The RfD value for this contaminant is 0.009 mg/(kg·day) (Table 4.11, p. 156 in the textbook). The cancer potency via the oral route is 0.58 kg·day/mg (Table 4.9, p. 150 in the textbook). a. Accordingly, the hazard coefficient for a 20-year exposure to this chemical can be calculated using the average daily dose: ± ² ± ² ± ² ± ² 1 1 · · 0029 . 0 70 / 1 . 0 / 2 ³ ³ u day kg mg kg L mg d L ADD The hazard index is therefore 32 . 0 009 . 0 0029 . 0 RfD ADD HI b. The chronic daily exposure for a 70-year average lifespan and a 20-year exposure to this chemical can be calculated as ± ² ± ² ± ² ± ² ± ² ± ² ± ² ± ² 1 1 · · 00082 . 0 365 70 70 365 20 / 1 . 0 / 2 ³ ³ u u u u u day kg mg day year kg day year L mg d L CDI The cancer risk is therefore 4 10 · 7 . 4 58 . 0 00082 . 0 ³ u u PF CDI Risk c. Drinking this water 30 years instead of 20 does not change the hazard coefficient but it does change the chronic daily intake, which is now ± ² ± ² ± ² ± ² ± ² ± ² ± ² ± ² 1 1 · · 00122 . 0 365 70 70 365 30 / 1 . 0 / 2 ³ ³ u u u u u day kg mg day year kg day year L mg d L CDI The resulting risk is 4 10 · 1 . 7 58 . 0 00122 . 0 ³ u u PF CDI Risk

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2 Problem 2 (textbook 4.16) A man works in an aluminum smelter for 10 years. The drinking water in the smelter contains 0.070 mg/L arsenic and 0.56 mg/L methylene chloride. His only exposure to these chemicals in water is at work. a. What is the hazard index associated with this exposure? b. Does the HI indicate this is a safe level of exposure? c. What is the incremental lifetime cancer risk for the man due solely to the water he drinks at work and does it seem to be an acceptable risk according to EPA? a. The RfD values for arsenic and methylene chloride are 0.0003 and 0.060 mg/(kg·day), respectively. Accordingly, the ADD and HI values can be calculated as ± ² ± ² ± ² ± ² 1 1 · · 002 . 0 70 / 07 . 0 / 2 ³ ³ u day kg mg kg L mg d L ADD As ± ² ± ² ± ² ± ² 1 1 · · 016 . 0 70 / 56 . 0 / 2 3 ³ ³ u day kg mg kg L mg d L ADD Cl CH 67 . 6 0003 . 0 002 . 0 As As As RfD ADD HI 27 . 0 060 . 0 016 . 0 3 3 3 Cl CH Cl CH Cl CH RfD ADD HI b. The total HI for this exposure is the sum of all risks, and this value is 6.94. This is a very high hazard index indicating that the water is very unsafe. c. The incremental cancer risks can be established based on the values of chronic daily exposures calculated for an average 70 year lifespan: ± ² ± ² ± ² ± ² ± ² ± ² ± ² ± ² 1 1 · · 000098 . 0 365 70 70 250 10 / 07 . 0 / 1 ³ ³ u u u u u day kg mg day year kg day year L mg d L CDI As The potency risk of arsenic is 1.75 kg·day/mg (Table 4.9, p. 150 in the textbook).
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