Complete

A suspected carcinogen appears in L.A. water at an estimated concentration of 0.2 mg/l.

1. What assumptions must you make in estimating dose?

2. What is the daily dose to a 60 kilogram female adult with average water intake?

3. What is the average lifetime dose (D) for this individual?

4. In toxicological tests with this chemical, 20 of 200 rats die from cancer. In the control group,10 of 200 rats die from cancer. Is this difference statistically significant?

5. Using Abbot's correction, what are the upper and lower limits (98% confidence) of the excess risk (Pe' and Pe")?

6. The excess risk given above is at a dose of 116 gm in rats. What is the unit risk factor (R) for this chemical?

7. At the human dose calculated in question #3 (a much lower dose), what is the excess risk (P) for this exposure?

8. What is the excess number of cancer cases (E.C.) if 10 million people in greater Los Angeles (not the entire population) are exposed to this pesticide in the drinking water?

 

 

Answers

1. C: all water supplies have the same concentration, no other sources of exposure

I: intake is a default value and only through ingestion

T: lifetime exposure (worst case)

F: no safety factors

W: no dose scaling

L: no latency

assume that the agent causes cancer!

 

2. D = [C* I * 70 * T * (78 - L) * 365] / [F * W * (E - L)]

= C * I * T

C = 0.2 mg/l

I = 2.5 l/day (p.29)

T = 78 * 365 = 28,470 days

 

daily C * I = 0.2 mg/l * 2.5 l/day

dose = 0.5 mg/day

 

3. life C * I * T = 0.2 * 2.5 * 28,470

dose = 14.2 gm

 

4. test: Xt = 20 Nt = 200 Pt = 0.1

control: Xc = 10 Nc = 200 Pc = 0.05

p = 0.075 q = 0.925