In your workplace, you are exposed to two toxic pollutants: X and Y. The health
ID: 295794 • Letter: I
Question
In your workplace, you are exposed to two toxic pollutants: X and Y. The health standard for exposure to X is 1 ppmv for 8 hours per day, 5 days per week. The standard for Y is one ppbv for 1 hour per day, 5 days per week. Exposure to X or Y at the standard concentration would produce a risk of cancer of 1 in 1 million after 30 years. You test air from your workplace and have it analyzed for X and Y. It is found to contain 3 ppmv of X and 1.5 ppbv of Y. If you want to keep your overall risk of contracting cancer from workplace exposure to 1 in 1 million or less, (a) how many years could you work here before you would have to quit? Assume the risk from each toxin increases directly in proportion to the total exposure over time, and that risks are additive (not synergistic). (b) Which toxin is causing the larger risk to your health?
Explanation / Answer
Weeks in one year = 52.1428
therefore, weeks in 30 years would be = 1564.29 weeks
Health standard exposure of x = 1 ppmv for 8 hours per day, 5 days per week
This is equivalent to = 1 x 8 x 5 ppmv per week = 40 ppmv per week
This is equivalent to = 40 x 1564.29 = 62,571.6 ppmv in 30 years
Similarly for Y, Health standard exposure = 1 x 1 x 5 x 1564.29 = 7,821.45 ppbv in 30 years
(a)
Now, the workplace concentration = 3 ppmv of X.
In one week the concentration of X would be (working for 8 hours) = 3 x 8 x 5 = 120 ppmv per week
Therefore a person can work for = (62,571.6 / 120) = 521.43 weeks = (521.43 / 52.1428) = 10 years
Similarly for pollutants Y:
In one week the concentration of Y would be (working for 8 hours) = 1.5 x 8 x 5 = 60 ppbv per week
Therefore a person can work for = (7,821.45 / 60) = 130.3575 weeks = (130.3575 / 52.1428) = 2.5 years
(b)
The toxic "Y" is causing larger risk to our health beacuse we are seeing the health standard for exposure to Y is one ppbv for 1 hour per day, 5 days per week and since less concentration of Y is causing serious health hazards that means "Y" is more toxic as compared to "X".