RISK ASSESSMENT  Tests/exams

                Download the Excel spreadsheet here (NOW with completed cells)

The assessment has been carried out on a self-sufficient population

of subsistence farmers who have been exposed to contaminated food

and water for 30 years.

(The BCF (Bioconcentration factor : 2x) has been factored in at column 6)

1.   Complete the chart by filling in the missing blank (white) values (Note: the

dark shaded cells have no data)

2.   What is the total combined carcinogenic risk (water + food) for this exposure?  ... 3.72E-05

3.   What is the LEAST number of chemicals to be targeted and removed for the

combined exposure to not exceed de minimis levels?   .........FOUR

4.   Now assume that a new deep artesian well can supply clean water, leaving only

the contaminated soil for growing food.  Will the de minimis level still be exceeded

if residents use uncontaminated water, but continue to use the same contaminated

soil for their food supply?  YES, the risk is 2.21E-05

5.   If de minimis is STILL exceeded by the food, advise the residents how they should

alter their food intake from this home grown supply so as to be acceptably safe.

This is >22 times too high.  They should reduce their intake of THESE FOODS to no more

than 45 g per day and find another source of food

6.   What was the combined non-carcinogenic hazard index for these people BEFORE

the water was replaced?     .... 1.8

7.   After the water is replaced, does the food exposure represent a level above what

is acceptable, or is the level approximately satisfactory? 

                 It is now 1.006, approximately at the acceptable HI of 1.00

Please note that the answers to Q3B and 3C (marked * and **) were originally transposed

when I first prepared the above page.  The correct values were used in marking the papers

so no adjustment is necessary.   The values shown are now correctly placed.

END OF TEST PAPER:  =================================================================