1
CEE 350 Homework 5 Solutions
Problem 1 (textbook 4.5) Suppose a 70kg individual drinking 2 L/day of water
containing 0.1 mg/L of 1,1dichloroethylene 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 20year 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 70year average lifespan and a 20year
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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