1. A worker is exposed to four different airborne contaminants in the workplace. Samples have already been taken and the exposure concentrations for each of the four contaminants has been determined. The table below presents the results of these calculations. Determine the combined effect of these simultaneous exposures to determine if the worker exposure has exceeded the PEL. (6 points)
Table 1. Data for Problem #1
|
Substance |
Observed Concentration |
OSHA PEL for Substance |
|
A |
60 ppm |
225 ppm |
|
B |
25 ppm |
40 ppm |
|
C |
161 ppm |
275 ppm |
|
D |
67 ppm |
75 ppm |
What is the equivalent exposure for this mixture of 4 substances? ____________________
Is this mixed exposure within acceptable limits, according to the OSHA PEL? __________
2. Cresols are widely occurring natural and manufactured aromatic organic compounds having a yellowish to brownish red tint, a distinctive “coal tar” aroma, and melting points near room temperature. The name cresol (creosol) reflects their traditional source, creosote. One isomer (m-Cresol) is a precursor to two commercially and widely used pesticides. A worker in the bagging plant for a pesticide manufacturer is exposed to airborne particulates containing cresol. (14 points)
The worker works five 8-hour days each week. An air monitoring device that sampled air in the breathing zone was attached to the worker during a typical work day and produced the results illustrated in Table 3.
Find the applicable occupational exposure limits (OELs) for creosol (all isomers) on the OSHA Annotated PELs table and populate Table 2.
Table 2. OELs for Creosol (all isomers)
|
Substance |
CAS No. |
Regulatory Limits |
Recommended Limits |
|||
|
|
|
OSHA PEL |
Cal-OSHA PEL |
NIOSH REL |
ACGIH TLV |
|
|
ppm |
mg/m3 |
8-hour TWA |
Up to 10-hour TWA |
8-hour TWA |
||
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|
|
|
|
|
||
Calculate the 8-hour time-weighted average (TWA) of worker exposure based on the information provided below to determine if the worker has been exposed above the OEL.
Table 3. Calculating the Time-Weighted Average
|
Time Period |
Period Duration |
Contaminant Concentration |
Calculate Dose for each Time Period |
|
1 |
90 minutes |
19 mg/m3 |
|
|
2 |
30 minutes |
32 mg/m3 |
|
|
3 |
15 minutes |
39 mg/m3 |
|
|
4 |
120 minutes |
23 mg/m3 |
|
|
5 |
180 minutes |
20 mg/m3 |
|
|
6 |
45 minutes |
21 mg/m3 |
|
|
Sum of Exposures |
min |
mg/m3 |
min x mg/m3 |
Use the TWA Calculation to determine the 8-hour TWA for this creosote exposure.
Was this worker exposed to this chemical above the OSHA PEL?
Was this worker exposed to this chemical above the TLV®-TWA?
Which time period(s) would you want to evaluate further? _______________________________
3. During painting operations, keeping oil-based paints the proper consistency is often accomplished through the addition of a thinning liquid. There are a variety of paint thinners, each utilizing a different mixture of solvents. During the mixing process and during application, particularly when an air applicator is used, there is the potential for workers to be exposed to vapors. A worker uses a combination of three different paint thinning agents; naphthalene, dimethylformamide (DMK), and ethylbenzene. The worker then applies the paint using a pneumatic spray gun inside a room that has been closed off from adjoining rooms by plastic sheets to prevent overspray and migration of odors, as well as to keep dust from entering the room. The observed concentrations of each thinning agent are identified in Table 4. (6 points)
Table 4: Finding the OSHA PEL Values in the Annotated Tables
|
Substance |
Observed Concentration |
OSHA PEL-TWA for Substance |
|
Naphthalene |
5 ppm |
|
|
Dimethylformamide |
6 ppm |
|
|
Ethylbenzene |
48 ppm |
|
Perform the required calculations using the OSHA PEL-TWA values to determine the combined (mixture) effect so you will know if the worker was exposed above the PEL.
Was the worker’s exposure greater than the PEL? _____________________________
4. You reviewed a Safety Data Sheet for a new product and the main ingredient is toluene. (4 points)
Find the applicable occupational exposure limits (OELs) for toluene on the OSHA Annotated PELs table (Table Z-2) and populate the table shown below.
Table 2. OELs for Toluene
|
Substance |
CAS No. |
Regulatory Limits |
Recommended Limits |
|||
|
|
|
OSHA PEL |
Cal-OSHA PEL |
NIOSH REL |
ACGIH TLV |
|
|
ppm |
mg/m3 |
8-hour TWA |
Up to 10-hour TWA |
8-hour TWA |
||
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|
|
|
|
|
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Sampling media: Charcoal Tube Maximum volume: 12 Liters Maximum flow rate: 0.05 L/min
How many minutes do you need to sample for to obtain the maximum allowed volume using the maximum allowed flow rate?
_________ min
How many samples will you need to take to represent an 8-hour (480 minute) work day?
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