Industrial Hygiene Case Study

OSH 4301, Industrial Hygiene 1

Course Learning Outcomes for Unit IV Upon completion of this unit, students should be able to:

5. Explore health hazards in the workplace. 5.1 Describe sampling methods to be used for evaluating health hazards in the workplace.

6. Perform basic calculations related to industrial hygiene. 6.1 Calculate the volume collected for personal sampling using the flow rate and sampling time. 6.2 Calculate the concentration of a sample given the laboratory analytical result and sample

volume. 6.3 Calculate sample results from mg/m3 to ppm.

Reading Assignment To access the following resources, click the links below: Ashley, K., & O'Connor, P. F. (2016). Purpose, scope and use of the NIOSH manual of analytical methods. In

K. Ashley & P. F. O'Connor (Eds.), NIOSH manual of analytical methods (5th ed., pp. PS-1–PS-9). Retrieved from http://www.cdc.gov/niosh/docs/2014-151/pdfs/chapters/chapter-ps.pdf

Eide, M., Simmons, M., & Hendricks, W. (2010). Validation guidelines for air sampling methods utilizing

chromatographic analysis. Retrieved from https://www.osha.gov/dts/sltc/methods/chromguide/chromguide.pdf

Kennedy, E. R., Fischbach, T. J., Song, R., Eller, P. M., Shulman, S. A., & Hull, R. D. (2016). Development

and evalution of methods. In K. Ashley & P. F. O'Connor (Eds.), NIOSH manual of analytical methods (5th ed., pp. ME-1–ME-19). Retrieved from http://www.cdc.gov/niosh/docs/2014- 151/pdfs/chapters/chapter-me.pdf

Course/Unit Learning Outcomes

Learning Activity

5.1

Unit IV Lesson Article: “Purpose, scope and use of the NIOSH manual of analytical methods” Article: “Validation guidelines for air sampling methods utilizing chromatographic analysis”

6.1

Unit IV Lesson Article: “Development and evaluation of methods” Article: “General considerations for sampling airborne contaminants” Unit IV Case Study

6.2 Unit IV Lesson Article: “General considerations for sampling airborne contaminants” Unit IV Case Study

6.3 Unit IV Lesson Article: “General considerations for sampling airborne contaminants” Unit IV Case Study

UNIT IV STUDY GUIDE

Evaluating Exposures to Gases and Vapors

OSH 4301, Industrial Hygiene 2

UNIT x STUDY GUIDE

Title

McCammon, C. S., & Woebkenberg, M. L. (2016). General considerations for sampling airborne contaminants. In K. Ashely & P. F. O'Connor (Eds.), NIOSH manual of analytical methods (5th ed., pp. SA-1–SA-23). Retrieved from https://www.cdc.gov/niosh/docs/2014-151/pdfs/chapters/chapter- sa.pdf

Unit Lesson Another important task performed by the industrial hygienist is evaluating exposures to health hazards. The image most associated with an industrial hygienist is one of sampling personal hazard exposures in a work location. This image is simplistic and does not represent the work required to complete an accurate evaluation of employee exposures. The process is much more complicated than most people realize. One important decision is determining which sampling and analytical method(s) to use. Sampling and analytical methods are highly dependent on the type of health hazard. Methods for evaluating gases and vapors differ greatly from methods for particulates, noise, and radiation. It is common to use sorbent tubes or badges for gases and vapors, but not for particulates. An industrial hygienist must understand the differences in chemical states in order to accurately evaluate exposures. In this unit, we will look at the subject of evaluating exposures to gases and vapors. One of the first questions is whether the samples will be personal samples or area samples. Personal samples are collected by placing a sampling device on the individual worker for a specified period of time. An area sample is placed in an area of the workplace and not directly on a worker. Personal sampling is the preferred method for evaluating employee exposures and determining OSHA compliance. However, in some cases, placing a sampling train on an individual can create an additional hazard that may result in an unacceptable risk to the employee. If this is the case, area samples will be used. In some regulations, OSHA specifies that the exposure monitoring will be made from breathing zone air samples (OSHA, 1970b). In other regulations, OSHA does not specifically state that the samples must be collected in the breathing zone, but that they must be representative of each employee’s exposure (OSHA, 1970c). Another important consideration is the time period of the sampling. One variable that affects the sampling length is the type of occupational exposure limit (OEL) that exists for the health hazard. OSHA publishes legally enforceable OELs called permissible exposure limits (PELs). NIOSH publishes recommended exposure limits (RELs), and the American Conference of Governmental Industrial Hygienists (ACGIH) publishes threshold limit values (TLVs). These are often more stringent than the established OSHA PELs but are not legally enforceable by OSHA. All three of the entities use three types of OELs: time-weighted average (TWA) OELs, short-term exposure limits (STELs), and ceiling concentrations (C). Some health hazards will only have a TWA OEL, some only a STEL, some only a C, and some will have a combination of all three OELs. Each of the three types of OELs may require a different sampling length. TWA OELs represent an exposure for an 8-hour work shift during a 40-hour workweek. Sampling for health hazards with a TWA OEL requires a full-shift sample. It is often not feasible to sample for the whole work shift because employees have time at the start and close of the work shift where they get ready for work and get ready to go home. Additionally, when a number of samples are necessary, it takes time to place sampling devices on all the workers. Therefore, full-shift samples will typically be for a time period between seven and eight hours. OSHA specifies that a full-shift sample must be collected for at least seven continuous hours (OSHA, 1970d). OSHA may also publish a substance-specific standard that contains an action level. The action level also represents a TWA exposure that, if exceeded, requires the employer to take specific actions (OSHA, 1970e). Short-term exposure limits (STELs) should not be exceeded for a shorter time period, typically 15 minutes, as long as the 8-hour TWA OEL is also not exceeded for the work shift. OSHA does not use STELs in Tables Z- 1, Z-2, or Z-3. OSHA has established some STELs in substance-specific standards (OSHA, 1970g). Some of the terminology OSHA uses for short-term limits may be confusing. For example, in some substance-specific standards, OSHA uses the term excursion limit, which is defined the same way as a STEL (OSHA, 1970f). The ACGIH assigns STELs for many more health hazards than OSHA. According to the definition of STEL, samples collected to evaluate short-term exposures are collected for only 15 minutes (or another time limit set by OSHA).

OSH 4301, Industrial Hygiene 3

UNIT x STUDY GUIDE

Title

The third type of OEL, the ceiling concentration, represents an exposure not to be exceeded at any time during the work shift. OSHA does include ceiling limits for some health hazards in Tables Z-1 and Z-2 and in some substance-specific standards. Evaluating exposures with an established ceiling concentration can be difficult. Most laboratory analytical methods are not designed to detect chemicals instantaneously. For some compounds, instantaneous monitoring can be performed using a direct-reading meter; however, sensors have not been developed for many of the chemicals with an established ceiling concentration. Therefore, OSHA specifies that a 15-minute sample can be used to evaluate the exposure (OSHA, 1970a). The choice of a sampling and analytical method will determine the sensitivity and accuracy of the sampling to be performed. If the industrial hygienist chooses an incorrect method, the laboratory may not be able to detect the compound in a 15-minute sample at the level that has been set as a STEL or ceiling concentration. Receiving a lab result of 3.0 ppm for formaldehyde for a 15-minute sample would not help an industrial hygienist evaluate an employee’s exposure when the OSHA STEL for formaldehyde is 2.0 ppm. Fortunately, there are two organizations that publish analytical methods for industrial hygiene sampling. Visit https://www.osha.gov/dts/sltc/methods/index.html for OSHA’s guide, Sampling and Analytical Methods. Visit http://www.cdc.gov/niosh/docs/2003-154/default.html for the National Institute for Occupational Safety and Health (NIOSH) Manual of Analytical Methods (NMAM). Both of these references contain validated sampling and analytical methods for evaluating health hazards. Any industrial hygienist who regularly performs sampling for health hazards will be familiar with both references. As an example, access http://www.cdc.gov/niosh/docs/2003-154/pdfs/1501.pdf for the NIOSH method 1501 for aromatic hydrocarbons. In the section labeled “Sampling,” the industrial hygienist is instructed to use a coconut shell charcoal tube with 100 mg in the front section and 50 mg in the back-up section (NIOSH, 2003). The back-up section is analyzed along with the front section to determine if any breakthrough of the compound occurred during the sampling. If the back-up section contains an excess amount of the compound, the sample may be invalidated. These sampling tubes can be purchased commercially from several sources, and most industrial hygiene analytical laboratories will also provide the tubes free of charge if their lab is going to perform the analysis. The “Sampling” section also contains a range of flow rates and volumes. NIOSH method 1501 is validated for multiple aromatic hydrocarbons as shown in Table 3 (NIOSH, 2003). In Table 3 for the health hazard benzene, the method recommends using a flow rate of <0.2 liters per minute (L/min) and collecting between 5 and 30 liters of air during the sampling period. Using these values, it is easy to calculate that the recommended sampling time is between 25 minutes and 150 minutes using a flow rate of 0.2 L/min or between 50 minutes and 300 minutes using a flow rate of 0.1 L/min. The flow rates are recommended values based on the validation of the method at the lab (NIOSH, 2003). The industrial hygienist can employ professional judgment and sample for a longer time period if the level in the workplace is expected to be much lower. The results from sampling are only as accurate as the process used to collect the sample. It is typical to calibrate the sampling pumps prior to and after the sampling event. If the differences between the pre- and post-calibrations are too great (10% is commonly used), the sample may be invalidated. One important task is the calibration of the sampling train. The most accurate calibration method uses a primary calibration device. Industrial hygienists who have been performing sampling for a long time remember using a soap-bubble flow meter to calibrate sampling pumps. While very accurate, these devices were fairly time consuming and not portable. Several primary calibration devices have been created over the years that are much more portable, allowing calibration with a primary device to be performed in the field.

An industrial hygienist can calculate the total volume of air collected during a sampling event by multiplying the average flow rate by the sampling time.

For example, if the pre-sampling calibration showed a flow rate of 0.12 L/min and the post-sampling calibration showed a flow rate of 0.10 L/min, the average flow rate would be 0.11 L/min. If you ran the sample for 300 minutes the volume you report to the lab would be (0.11 L/min) X (300 minutes) = 33 Liters. The rest of NIOSH method 1501 shows how the laboratory analyzes the sample. The lab will usually report the final exposure concentration as either milligrams of the compound per cubic meter of air collected (mg/m 3) or parts per million (ppm). Gases and vapors are usually reported as ppm and particulates as mg/m3 (NIOSH, 2003). The industrial hygienist should know how these values were calculated to check the accuracy of the report. Section 14 on page 3 of NIOSH method 1501 contains the formula for the calculation (NIOSH, 2003). The

OSH 4301, Industrial Hygiene 4

UNIT x STUDY GUIDE

Title

results of the analysis of the front and back sections of the sample tube are added together, and the results of the front and back sections of a field blank are added together. The results from the field blank are subtracted from the results of the sample tube. That result is then divided by the volume of the sample that was calibrated. As an example, if the lab reported that the total amount of benzene in a sample was 20 micrograms (µg) and there was no detectable level of benzene on the field blank, using the 33 liters of air we calculated for our sample above, the resulting TWA concentration would be 20 µg/33 L = 0.61 µg/L. This does not look like either the mg/m3 or the ppm results discussed earlier, so one must also understand how to convert results. Below the formula in section 14 of NIOSH 1501 is the note µg/L = mg/m3 (NIOSH, 2003). Therefore, we know our result can also be expressed as 0.61 mg/m3.

Results expressed as mg/m3 can be converted to ppm by knowing the molecular weight of the compound.

Let’s say that the samples were collected at standard temperature and pressure (STP). If the temperature and pressure are different from STP, we would have to make some different calculations to account for the differences. The molecular weight of benzene is approximately 78.1. At STP to convert 0.61 mg/m3 to ppm, multiply by the ideal gas constant (24.45) and divide by the molecular weight. Thus (0.61 mg/m3) X (24.45) = 14.91/78.1 = 0.19 ppm. The OSHA PEL for benzene is 1 ppm as an 8-hour TWA exposure, so our result is less than the OSHA TWA PEL. Note that the NIOSH REL for benzene is 0.1 ppm as an 8-hour TWA exposure, and the ACGIH TLV for benzene is 0.5 ppm as an 8-hour TWA exposure. Sometimes, deciding which of the three OELs to use is as important as how the samples were collected.

References

National Institute for Occupational Safety and Health. (2003). Hydrocarbons, aromatic: Method 1501. In P. M. Eiler & M. E. Cassinelli (Eds.), NIOSH manual of analytical methods (4th ed.). Retrieved from https://www.cdc.gov/niosh/docs/2003-154/pdfs/1501.pdf

Occupational Safety and Health Administration. (1970a). Occupational safety and health standards: Toxic and

hazardous substances (Standard No. 1910.1000). Retrieved from https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9991

Occupational Safety and Health Administration. (1970b). Occupational safety and health standards: Toxic and

hazardous substances (Standard No. 1910.1001). Retrieved from https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=standards&p_id=9995

Occupational Safety and Health Administration. (1970c). Occupational safety and health standards: Toxic and

hazardous substances (Standard No. 1910.1017). Retrieved from https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10021

Occupational Safety and Health Administration. (1970d). Occupational safety and health standards: Toxic and

hazardous substances (Standard No. 1910.1025). Retrieved from https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10030

Occupational Safety and Health Administration. (1970e). Occupational safety and health standards: Toxic and

hazardous substances (Standard No. 1910.1027). Retrieved from https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10035

Occupational Safety and Health Administration. (1970f). Occupational safety and health standards: Toxic and

hazardous substances (Standard No. 1910.1047). Retrieved from https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10070

OSH 4301, Industrial Hygiene 5

UNIT x STUDY GUIDE

Title

Occupational Safety and Health Administration. (1970g). Occupational safety and health standards: Toxic and hazardous substances (Standard No. 1910.1048). Retrieved from https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10075

Suggested Reading To access the following resources, click the links below: The NIOSH and OSHA standards are primarily used in the United States. Other countries also publish analytical methods for industrial hygiene sampling. The following article, written by one of the contributors to the NMAM, discusses efforts to harmonize the methods in NMAM with other analytical methods. Ashley, K. (2015). Analytical performance issues: Harmonization of NIOSH sampling and analytical methods

with related international voluntary consensus standards. Journal of Occupational and Environmental Hygiene, 12(7), D107–D115. Retrieved from https://libraryresources.waldorf.edu/login?auth=CAS&url=http://search.ebscohost.com.libraryresource s.waldorf.edu/login.aspx?direct=true&db=bxh&AN=BACD201500375763&site=ehost-live&scope=site

Direct-reading meters are available to obtain nearly instantaneous air concentrations for certain compounds. Some meters will provide readings for specific chemicals, while other meters provide a more generic reading (e.g., for total volatile organic compounds). The accuracy, precision, and specificity of the direct-reading meters can vary greatly. The following study compared several direct-reading meters using a validated method with laboratory analysis. Coffey, C., LeBouf, R., Lee, L., Slaven, J., & Martin, S. (2012). Effect of calibration and environmental

condition on the performance of direct-reading organic vapor monitors. Journal of Occupational and Environmental Hygiene, 9(11), 670-680. Retrieved from https://libraryresources.waldorf.edu/login?auth=CAS&url=http://search.ebscohost.com.libraryresource s.waldorf.edu/login.aspx?direct=true&db=a9h&AN=82827420&site=ehost-live&scope=site

Learning Activities (Nongraded) Non-graded Learning Activities are provided to aid students in their course of study. You do not have to submit them. If you have questions, contact your instructor for further guidance and information. Look through the list of chemical methods and access several for common vapors and gases. Determine which sampling media you would use for that specific method, the range of sampling flow rates, and sampling times. See if you can rate the difficulty of using each of the methods you accessed. Eiler, P. M., & Cassinelli, M. E. (Eds.). (1994). NIOSH manual of analytical methods (4th ed.). Retrieved from

https://www.cdc.gov/niosh/docs/2003-154/default.html