1. A small community gets its water from wells that tap into an old, large aquif
ID: 2908598 • Letter: 1
Question
1.A small community gets its water from wells that tap into an old, large aquifer. Recently an environmental risk assessment study found toxic concentration in the ground water due to improperly disposed chemicals from a near by manufacturing plant. Estimates are available of the contamination levels of the various chemicals. Each contaminant’s concentration (C) in the water is measured in microgram per liter. The Cancer Potency Factor (CPF) for each chemical is uncertain. The population risk assessment must account the variability of body weights (BW) and volume of water consumed (WC) by the individuals in the community per day. A simple equation including all these factors for calculating population risk (PR) is given as :
Using the table given below, identify the expected, median and maximum population risk. And also determine the 90% confidence interval for the number of people at risk out of a population of 1 million.
Parameter
Distribution
Min.
Max.
Mean/Mode
STD
Concentration of contaminates (C), mg/liter
Triangle
80
120
110
-
CPF
Lognormal
-
-
0.03
0.02
Water consumption (WC), Liter/day
Normal
-
-
2
1
Body Weigths (BW), kg
Normal
-
-
70
10
Parameter
Distribution
Min.
Max.
Mean/Mode
STD
Concentration of contaminates (C), mg/liter
Triangle
80
120
110
-
CPF
Lognormal
-
-
0.03
0.02
Water consumption (WC), Liter/day
Normal
-
-
2
1
Body Weigths (BW), kg
Normal
-
-
70
10
Explanation / Answer
round water contamination is nearly always the result of human activity. In areas where population density is high and human use of the land is intensive, ground water is especially vulnerable. Virtually any activity whereby chemicals or wastes may be released to the environment, either intentionally or accidentally, has the potential to pollute ground water. When ground water becomes contaminated, it is difficult and expensive to clean up. To begin to address pollution prevention or remediation, we must understand how surface waters and ground waters interrelate. Ground water and surface water are interconnected and can be fully understood and intelligently managed only when that fact is acknowledged. If there is a water supply well near a source of contamination, that well runs the risk of becoming contaminated. If there is a nearby river or stream, that water body may also become polluted by the ground water
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