After your initial review of the operations and safety data sheets (SDS), you have determined the sampling you want to perform at Acme Automotive Parts (AAP). The table below lists hazards you want to sample and the sampling/analytical methods you decide to use. You can access the National Institute for Occupational Safety and Health (NIOSH) methods at https://www.cdc.gov/niosh/nmam/default.html and the Occupational Safety and Health Administration (OSHA) methods at https://www.osha.gov/dts/sltc/methods/toc.html.
Hazard
Possible Method
Occupational Exposure Limits (OEL)
Manganese Fume (Welding)
NIOSH 7302
5 mg/m3 (OSHA Ceiling)
Copper Fume (Welding)
NIOSH 7302
0.1 mg/m3 (OSHA 8-hour TWA)
Lead Fume (Welding)
NIOSH 7302
0.05 mg/m3 (OSHA 8-hour TWA)
1,2,4 trimethylbenzene (Paint)
OSHA 1020
25 ppm (ACGIH 8-hour TWA TLV)
Toluene (Paint)
OSHA 111
50 ppm (ACGIH 8-hour TWA TLV)
Xylene (Paint)
OSHA 1002
100 ppm (OSHA 8-hour TWA)
Metal Working Fluids
NIOSH 5524
0.5 mg/m3 (NIOSH 10-hour TWA REL)
Noise (throughout plant)
None
90 dBA (OSHA 8-hour TWA)
Choose one hazard from the welding area, one hazard from the paint area, and the metal working fluids, and prepare one paragraph for each hazard (three paragraphs in total) answering each of the following questions:
Which sampling media will you be using?
What flow rate will you use?
How will you calibrate the sampling train?
Calculate the minimum sampling time you will require to be able to detect concentrations at the OELs listed in the table. Show your work in calculating the sampling times.
Will you collect personal or area samples? Explain why.
Are there any compounds listed in the method that might interfere with your sample?
Are there any special storage or shipment requirements for your samples?
Prepare one paragraph that concludes how you would evaluate noise exposures in the facility. Discuss what type of sampling instrument you would use, how you would perform calibration, whether you would use personal or area samples, and which areas at the facility you would include in the evaluation.
For this assignment, you will use the formula provided in the Sampling Duration section in Chapter 6 of the textbook. You need to find the limit of detection in the sampling method and choose an occupational exposure limit to use the formula. See the PowerPoint presentation in the study guide for an example.
UNIT III STUDY GUIDE
Evaluating Personal
Exposures in a Workplace
Course Learning Outcomes for Unit III
Upon completion of this unit, students should be able to:
4. Assess methods for performing industrial hygiene workplace analysis.
4.1 Summarize information from published sampling/analytical methods.
4.2 Calculate minimum required sampling times based on chosen sampling/analytical methods.
4.3 Describe industrial hygiene sampling processes.
Reading Assignment
Chapter 6: Gases and Vapors, pp. 119133
Chapter 7: Aerosols, pp. 144154
Chapter 11: Noise, pp. 248250
Chapter 13: Thermal Stressors, pp. 301309
In order to access the following resources, click the links below.
The presentation contains images of equipment that was discussed in the lesson. Reviewing the presentation
may provide a better understanding of the material in the lesson, especially if you have never performed IH
sampling before. The PowerPoint presentation also contains examples of calculations that you might be
required to perform in the unit assignment.
Click here to review the Unit III PowerPoint Presentation. Click here to download the PDF version of the
presentation.
Unit Lesson
After understanding how to anticipate and recognize hazards, the industrial hygienist must decide how to
evaluate the risks associated with the identified hazards. This is the task that most workers associate with the
field of IH. Many workers can remember when an industrial hygienist showed up at the worksite and required
certain employees to wear pumps and other devices for the entire work shift. Even though the sampling is
being performed to decrease employees health risks, this is also the task that many workers will object to
because they view the sampling devices as being intrusive and difficult to wear. In many cases, the most
difficult job the industrial hygienist has is to convince workers of the benefits of wearing a sampling device for
their work shift. In this unit, we will look at the different ways IH sampling can be performed and how to make
sure the data you produce is accurate and precise, in other words useful.
IH Sampling Basics
The essence of IH sampling for chemical hazards is passing a known volume of air through some media to
remove the chemical of interest from the air, thus, collecting it on the media. The media are then sent to a
laboratory where it is removed from the collection media and analyzed to determine the quantity of the
chemical that was collected. The air concentration can then be determined by dividing the quantity of the
chemical that was collected by the volume of air that was pulled through the media (Fuller, 2015). That
sounds simple enough, right? What you must consider is that the results you get from sampling for exposures
in a workplace will rarely be equal to the actual exposures that were present. Why? Because errors can enter
into the process virtually at any step.
OSH 6302, Advanced Industrial Hygiene
1
Therefore, one of the biggest problems you might face is making sure that errors
arex minimized
as much as
UNIT
STUDY GUIDE
possible. Consider what happens if you are off on your determination of the volume
Title of air collected, the
laboratory is off in determining the quantity of the chemical that was collected, someone makes a mistake on
any calculations, or the worker being sampled muddles the sample during the sampling period. Each of these
errors would be cumulative, so if each step introduced only a 5% error, the overall error of the exposure
concentrations could be greater than 25%. The textbook has a good discussion of errors on pages 120121
(Fuller, 2015). Therefore, how do you minimize the error when you evaluate exposures?
Minimizing Errors in Sampling
The first step is making sure you use validated methods for sampling and the laboratory uses validated
methods for analyzing your samples. There are two organizations that publish validated and semi-validated
sampling and analytical methods, the Occupational Safety and Health Administration (OSHA), and the
National Institute for Occupational Safety and Health (NIOSH).
Understanding how the methods are validated can help you understand how errors can enter into the
evaluation process. OSHA has established a procedure for validating sampling and analytical methods. In
order to be validated, research must consider five variables associated with the actual sampling, four
variables associated with the laboratory analysis of the samples, and four variables associated with the
overall method (Eide, Simmons, & Hendricks, 2010).
The variables associated with the actual sampling are sampler capacity, sampler rate, sampling interferences,
extraction efficiency, and the effects of storage (Eide, Simmons, & Hendricks, 2010). Research is conducted
to determine how much of the chemical can be collected on a sampler before 5% of the chemical breaks
through without being collected. The research then identifies a sampling rate or range of sampling rates for
which the collection is the most efficient. Any other chemicals that could interfere with the collection of the
chemical of interest by lowering the collection efficiency must also be identified. Once the chemical is
collected on the sampler, it has to be extracted in order to be analyzed. The amount that can be extracted is
determined and reported as a percentage. OSHA typically likes to see a collection efficiency greater than 90%
(Eide, Simmons, & Hendricks, 2010). Finally, research must be performed to see how long the sampling
device can be stored at specific temperatures before the chemical that was collected starts to degrade.
The variables associated with the analytical procedure are the analytical detection limit, calibration of the
analytical instrument, analytical interferences, and qualitative analysis. Basically, research must determine
what is the lowest quantity of the chemical that can be detected by the analytical method, the standard error
of the analysis (calibration), any chemicals that might interfere with detection of the chemical of interest during
the analytical process, and means that can be used to aid in determining the chemical is present during the
analysis (Eide, Simmons, & Hendricks, 2010).
Overall Sampling Method Accuracy
The variables associated with the overall procedure are the overall detection limit, the reliable quantitation
limit, precision, and reproducibility (Eide, Simmons, & Hendricks, 2010). Basically, this analysis is used to
determine, overall, what is the lowest quantity of the chemical that can be detected and quantified, how
precise the results should be, and how easily the analysis can be reproduced. The detection limit and the
quantitation limit are similar. The difference is that the detection limit is the lowest quantity that can be
detected (i.e., the analysis shows it is there, but may not be able to determine the exact concentration), while
the reliable quantification limit (RQL) is the lowest quantity of the chemical that can be reliably quantified (i.e.,
we can determine the exact concentration). For overall precision, OSHA requires the 95% confidence interval
to be within +25% (Eide, Simmons, & Hendricks, 2010).
You can see that a tremendous amount of effort must be taken to validate a sampling and analytical method
used by an industrial hygienist to evaluate chemical exposures. The result is a method that will hopefully,
determine exposures within + 25% of the actual exposures that are present. Of course, this means the results
will likely not be 100% accurate. This will present difficulties in using the results to compare with occupational
exposure limits (OEL). We will discuss these difficulties in the following unit.
Choosing a Sampling Method
OSH 6302, Advanced Industrial Hygiene
2
For this lesson we will look at the procedures you would use to decide which method
would
use to
UNIT x you
STUDY
GUIDE
evaluate an exposure and then how to use the method in actual practice. For our
Titleexample, we will look at
NIOSH method 2027 to evaluate exposures to acetone. You can access the method using this document.
Notice that the method is titled Ketones and can be used to sample for seven different ketones including
acetone.
The first decision the industrial hygienist must make is what sampling media to use. For ketones, method
2027 indicates that a solid sorbent tube containing two sections of silica gel (one with 500 mg and one with
1000 mg) is used (Ashley & OConnor, 2017). It is common for a sampling tube to contain two or more
sections of an adsorbent. Acetone would be collected on the first section. When acetone is detected on the
second (backup) section, it indicates that breakthrough has occurred. In other words, because either the
concentration of acetone was too high or the flow rate was too high, not all the acetone was collected, and
some broke through the first section. Having more than 5% breakthrough on the tube can invalidate the
sample results.
The chosen sampling method will include a recommended flow rate or range of flow rates. Method 2027
recommends a flow rate between 0.05 liters per minute (l/min) and 0.1 l/min (Ashley & OConnor, 2017). The
recommended flow rate is based on a range of concentrations that were tested during the validation of the
method. In Table 3 of the method, you can see that the range for acetone was 0.0226 milligrams (mg)
collected on the tube (Ashley & OConnor, 2017). With experience, an IH can choose to use higher or lower
flow rates depending on the expected air concentrations of acetone in the work environment. You might
choose to use 0.05 l/min if you expect relatively high concentrations of acetone to be present and to use 0.1
l/min if you expect a fairly low concentration to be present.
After you choose the flow rate, you must calibrate the sampling train (sample pump connected to the
sampling tube) to ensure you are using the correct flow rate. There are two basic levels of calibration devices
you can use: primary calibration devices and secondary calibration devices. A good discussion of the
differences in the two types of calibration devices is present on page 146 of the textbook (Fuller, 2015). In
some cases, industrial hygienists will calibrate a secondary calibration device like a rotameter against a
primary calibration device and use the rotameter to check flow rates periodically in the field during the sampling event.
Collecting an IH Sample
Another important consideration is how long to collect a sample. The method will provide you with some guidance. For example, method 2027 recommends collecting a minimum of 2 liters of air and a maximum of
10 liters of air (Ashley & OConnor, 2017). You can use that recommendation to calculate a minimum and maximum time to collect the samples by using the flow rate you chose. For example, if you chose to use a flow rate of 0.1 l/min and the maximum recommended air volume of 10 L, you would divide the 10 L by 0.1
l/min to get 100 minutes. Understand that the recommended volumes in the method are based on the research with the concentration shown in Table 3 of the method. If you wanted to evaluate the exposures for an employee over an entire eight-hour work shift, you could sample for a longer period if you expected exposure concentrations to be much lower than the concentrations shown in the method. The risk you take in sampling for a longer period is that you could have a breakthrough greater than 5% resulting in an invalid sample. Another approach would be to change out the sampling tube periodically, breaking up a work shift into a series of samples with lower volumes. This approach would result in additional costs for analysis.
It is also important to make sure that you collect an adequate volume of air, so the analytical process can actually quantify a result that is less than the published OEL that you decide to use. For example, if you had a permissible exposure limit (PEL) of 0.1 parts per million (ppm) for a chemical, but you did not collect an adequate volume of air, your reported analytical result could be
