Problems 59
The ACGIH clearly points out that the TLVs should not be used as a relative index of toxicity (see Figure 2-8), should not be used for air pollution work, and cannot be used to as- sess the impact of continuous exposures to toxicants. The TLV assumes that workers are ex- posed only during a normal eight-hour workday.
Every effort must be made to reduce worker exposures to toxicants to below the PEL and lower if possible.
Suggested Reading
Toxicology
Howard H. Fawcett and William S. Wood, eds., Safety and Accident Prevention in Chemical Operations, 2d ed. (New York: Wiley, 1982), ch. 14,15, and 25.
N. Irving Sax, Dangerous Properties of Industrial Materials, 6th ed. (New York: Van Nostrand Reinhold, 1984), sec. 1.
Phillip L. Williams and James L. Burson, eds., Industrial Toxicology: Safety and Health Applications in the Workplace (New York: Van Nostrand Reinhold, 1985).
60 Chapter 2 Toxicology
containing 5% alcohol. The insects were examined and classified one day after spraying.
The obtained data were:
Dose of Number
rotenone of Number
(mg/l) insects affected
a. From the given data, plot the percentage of insects affected versus the natural loga- rithm of the dose.
b. Convert the data to a probit variable, and plot the probit versus the natural logarithm of the dose. If the result is linear, determine a straight line that fits the data. Compare the probit and number of insects affected predicted by the straight-line fit to the ac- tual data.
2-3. A blast produces a peak overpressure of 47,000 N/m2. What fraction of structures will be damaged by exposure to this overpressure? What fraction of people exposed will die as a result of lung hemorrhage? What fraction will have eardrums ruptured? What conclu- sions about the effects of this blast can be drawn?
2-4. The peak overpressure expected as a result of the explosion of a tank in a plant facility is approximated by the equation
log P = 4.2 - 1.8 log r,
where P is the overpressure in psi and r is the distance from the blast in feet. The plant em- ploys 500 people who work in an area from 10 to 500 ft from the potential blast site. Es- timate the number of fatalities expected as a result of lung hemorrhage and the number of eardrums ruptured as a result of this blast. Be sure to state any additional assumptions.
2-5. A certain volatile substance evaporates from an open container into a room of volume 1000 ft3. The evaporation rate is determined to be 100 mglmin. If the air in the room is assumed to be well mixed, how many ft3/min of fresh air must be supplied to ensure that the concentration of the volatile is maintained below its TLV of 100 ppm? The tempera- ture is 77°F and the pressure is 1 atm. Assume a volatile species molecular weight of 100.
Under most circumstances the air in a room cannot be assumed to be well mixed. How would poor mixing affect the quantity of air required?
2-6. In Example 2-1, part c, the data were represented by the normal distribution function
Problems 61
Use this distribution function to determine the fraction of individuals demonstrating a response between the range of 2.5 to 7.5.
2-7. How much acetone liquid (in milliliters) is required to produce a vapor concentration of 200 pprn in a room of dimension 3 X 4 X 10 m? The temperature is 25°C and the pres- sure is 1 atm. The following physical property data are for acetone: molecular weight, 58.1; and specific gravity, 0.7899.
2-8. If 500 workers in a plant are exposed to the following concentrations of ammonia for the given number of hours, how many deaths will be expected?
a. 1000 pprn for 1 hour.
b. 2000 pprn for 2 hours.
c. 300 pprn for 3 hours.
d. 150 pprn for 2 hours.
2-9. Use the NIOSH web site (www.cdc.gov/niosh) to acquire the meaning and definition of IDLH concentration.
2-10. Use the NIOSH web site to determine an escape time period for a person subjected to an IDLH concentration.
2-11. Use the NIOSH web site to determine the number of deaths that occurred in 1992 as a result of asbestos.
2-12. Use the NIOSH web site to determine and compare the PEL and the IDLH concentra- tion of ethylene oxide and ethanol.
2-13. Use the NIOSH web site to determine and compare the PEL, IDLH concentration, and TLV for ethylene oxide, benzene, ethanol, ethylene trichloride, fluorine, and hydrogen chloride.
2-14. Use the NIOSH web site to determine and compare the PEL, IDLH concentration, and LC5(, for ammonia, carbon monoxide, and ethylene oxide.
2-15. The NIOSH web site states that deaths occur as a result of ammonia exposures between 5,000 and 10,000 pprn over a 30-min period. Compare the result to the results from the probit equation (Table 2-5).
2-16. Use the probit equation (Equation 2-5) to determine the expected fatalities for people exposed for 2 hours to each of the IDLH concentrations of ammonia, chlorine, ethylene oxide, and hydrogen chloride.
2-17. Determine the concentration of ethylene oxide that will cause a 50% fatality rate if the exposure occurs for 30 min.
2-18. A group of 100 people is exposed to phosgene in two consecutive periods as follows:
(a) 10 pprn for 30 min and (b) 1 pprn for 300 min. Determine the expected number of fatalities.
2-19. Determine the duration times, in minutes, that a group of 100 people can be exposed to 1500 pprn of carbon monoxide to result in (a) 0% fatalities and (b) 50% fatalities.
2-20. Use Equation 2-7 to convert the TLV in pprn to the TLV in mg/m3 for benzene, carbon monoxide, and chlorine. Assume 25°C and 1 atm.
62 Chapter 2 Toxicology
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2-21. Use a spreadsheet program (such as QuattroPro, Lotus, Excel) to solve Problem 2-4.Break the distance from 10 ft to 500 ft into several intervals. Use a small enough dis- tance increment so that the results are essentially independent of the increment size.
Your spreadsheet output should have designated columns for the distance, pressure, pro- bit values, percentages, and the number of individuals affected for each increment. You should also have two spreadsheet cells that provide the total number of individuals with eardrum ruptures and lung hemorrhage deaths. For converting from probits to percent- ages, use a lookup function or an equivalent function.
4 - 2 2 . Use the results of Problem 2-21 to establish the recommended distance between the control room and the tank if the control room is designed to withstand overpressures of (a) 1 psi and (b) 3 psi.
2-23. Use Equation 2-6 to convert probits of 3.72, 5.0, and 6.28 to percentage affected, and compare with the values shown in Table 2-4.
2-24. Estimate the exposure concentration in pprn that will result in fatalities for 80% of the exposed individuals if they are exposed to phosgene for 4 min.
2-25. Estimate the exposure concentration in pprn that will result in fatalities for 80% of the exposed individuals if they are exposed to chlorine for 4 min.
2-26. Determine the potential deaths resulting from the following exposure to chlorine:
a. 200 pprn for 15 min.
b. 100 pprn for 5 min.
c. 50 pprn for 2 min.
2-27. Determine the potential deaths resulting from the following exposure to chlorine:
a. 200 pprn for 150 min.
b. 100 pprn for 50 min.
c. 50 pprn for 20 min.
2-28. Use Joseph F. Louvar and B. Diane Louvar, Health and Environmental Risk Analysis:
Fundamentals with Applications (Upper Saddle River, NJ: Prentice Hall, 1998), pp. 287- 288, to find the toxicity levels (high, medium, low) for the inhalation of toxic chemicals.
2-29. Use Louvar and Louvar, Health and Environmental Risk Analysis, pp. 287-288, to find the toxicity levels (high, medium, low) for the single dose of a chemical that causes 50%
deaths.
"2-30. Using the following data, determine the probit constants and the LC,,:
Dose of Number Number rotenone of affected (mg/l) insects (deaths)
10.2 50 44
7.7 49 42
5.1 46 24
3.8 48 16
2.6 50 6