Question

Assume a factory releases a continuous flow of wastewater into a local stream, resulting in an in-stream carcinogen concentration of 0.72 mg/L just below the outfall. Suppose this carcinogen has an oral potency factor of 0.45 (mg/kg-day)-1 and that it is degradable with a reaction rate coefficient k of 0.23/day. To keep the problem simple, assume that the stream is uniform in cross section, flowing at the rate of 2 mph, and that there is no other sources or sinks for this carcinogen. At a distance of 150 miles downstream, a town uses this stream as is only source of water. Estimate the individual residential lifetime cancer risk caused by drinking this water.

Answer 1

Answer:

Calculate the individual residential lifetime cancer risk.  

Risk = Potential factor x CDI  …… (1)

Calculate the value of C  

C =  $C_{o} * e^{-kt}$

t = d / v

t = 150 miles / 2 mile per hrs.

t = 75 hrs

t = 75/24

t = 3.13 days

Substitute the obtained value in (2).

C = $C_{o} * e^{-kt}$

C = 0.72 x e^(-0.1*3.13)

C = 0.72 x 0.7313  

C = 0.526 mg/L

Substitute the obtained value in (1).

Risk = Potential factor x CDI

Risk = 0.30kg.d/mg x 0.526mg/L x 2L/d x 350day/365days

Risk = 0.3026