1. a) DDT has a potency factor of 0.34 (kg-day/mg). For an incremental lifetime
ID: 1005343 • Letter: 1
Question
1.
a) DDT has a potency factor of 0.34 (kg-day/mg). For an incremental lifetime risk cancer risk of one in a million, what is the acceptable concentration in drinking water? Assume an average consumption of 2 L/day and that each person weighs 70 kg?
b) Lifetime dose is used for what kind of toxins? options- carcinogenic, non carcinogenic, acute.
c) You look up a toxin and find an oral potency factor. From this you can deduce that the toxin is considered: options- non carcinogenic, non toxic, carcinogenic.
Explanation / Answer
Incremental life time risk = Chronic daily intake (CDI) * Potency factor (PF)
Given incremental lifetime risk = 1/106 = 10-6
CDI = Average daily dose (mg/ day) / Body weight (kg) = [DDT concentration (mg/L) * 2 L/day]/70 kg
Potency factor = 0.34 kg.day/mg
10-6 = [DDT concentration (mg/L) * 2 L/day]/70 kg * 0.34 kg.day/mg
10-6 / 0.34 kg.day/mg = ( DDT concentration * 2 L/day ) / 70 kg
DDT concentration = 1.029*10-4 mg/L
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b. Lifetime dose is used for carcinogenic toxins.
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c. Oral potency factor is measured for a carcinogenic toxin.
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