Occupational Hygiene

Instructions
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• Try to solve the problems in the space provided using the keyboard.
• Submit your answers as a Word document.
Name: Date:

1. List and describe the five zones of “thermal stress” (2 points).
2. List and describe the factors that affect thermal balance (3 points)

3. Explain the difference between heat stress and heat strain (2 points).

4. Identify the three workplace risk factors that can be used to identify potential heat stress issues. (2 points).

5. List heat-related disorders in increasing level of severity and identify symptoms of each disorder (3 points).

6. Identify classes of worker behaviors that can indicate heat stress issues in a workplace and provide two examples of each (3 points).
   
7. Explain the differences between general and specific controls for heat stress and provide examples (3 points).

8. The air temperature in a warehouse was measured and a dry-bulb reading of 30°C (86°F) was obtained. The amount of water vapor in the air was 21 gH2O/kg air. Using the graph below, calculate the relative humidity. Show your work. (2 points)

9. Temperature measurements were taken on a construction site during a clear, summer day. One employee was monitored during the performance of tasks during the hottest time of the day. The employee was engaged in tying off rebar, and took breaks in an air-conditioned trailer. The job-site supervisor insisted employees take a 15-minute break every 45 minutes and that they drink plenty of water or electrolyte supplement (e.g., Gatorade®). The employee was wearing regular pants and shirt.

Sample Sampling
Period Time
(min) Area
Sampled Activity Readings from Heat Stress Monitor (in °F)
Tg Tdb Tnwb WGBT
1 1:30 to 2:00 30 Foundation Pit Rebar tying – moderate work 99 96 81
2 2:00 to 2:15 15 Foundation Pit Rebar tying – moderate work 100 94 83
3 2:15 to 2:30 15 Break Room Break 75 73 67
4 2:30 to 2:45 15 Foundation Pit Rebar tying – moderate work 101 97 73
5 2:45 to 3:15 30 Laydown Yard Unloading/packing rebar – heavy work 102 96 85
6 3:15 to 3:30 15 Break Room Break 75 74 70

a. Determine the WBGT for each sampling period. Round values to the nearest whole number and enter the results in the table above. Show your work in the space below (3 points).
b. Determine heat stress based on a two-hour time weighted average WBGT. Show your work in the space below. (2 points)
c. Determine the clothing adjustment factor correction that may be required to calculate the effective WBGT. Enter the value in the space below. (1 point)
d. Calculate the metabolic rate for each task on the table above and determine the two-hour time weighted average metabolic rate (TWA-M). Refer to table 12-D in the lecture handout. Show your work in the space below. (3 points)
e. Using the obtained values for TWA-WBGT and TWA-M, determine whether the TLV for heat stress is surpassed using Figure 12-4 in the lecture handout. Enter your final answer and suggestion in English in the space below. (1 point)