Once you have reviewed the study guide, please type below the three most important items you took away from the study guide
UNIT VI STUDY GUIDE
Workplace Controls for Health
Hazards: Elimination/Substitution
and Engineering Controls
Course Learning Outcomes for Unit VI
Upon completion of this unit, students should be able to:
7. Recommend controls for industrial health hazards.
7.1 Calculate required flow rates based on hood design.
7.2 Compare and contrast available engineering controls for noise hazards.
7.3 Explain how to gauge the effectiveness of engineering controls.
Reading Assignment
Chapter 1: Introduction to Industrial Hygiene, pp. 13–16
Chapter 11: Noise, pp. 237–255
In order to access the following resources, click the links below.
Occupational Safety and Health Administration. (2016). Recommended practices for safety and health
programs: Hazard prevention and control. Retrieved from
https://www.osha.gov/shpguidelines/hazard-prevention.html
The PowerPoint presentation includes several examples of calculations similar to those you will be required to
perform for this week’s assignment.
Click here to review the Unit VI PowerPoint Presentation. Click here to download the PDF version of the
presentation.
Unit Lesson
Control
The last tenet of industrial hygiene (IH) is control. Once you evaluate the health hazards in a workplace, you
must identify the hazards where controls are required to reduce risk. This introduces two important terms that
the industrial hygienist must understand, hazard and risk. Many publications you read will use the terms
interchangeably. Even the textbook we are using for this class uses the term hazard in a manner that applies
more readily to the term risk on page 13. However, hazard and risk are quite different terms.
Hazard versus Risk
A hazard is anything that has the potential to cause harm to an individual, the environment, or a workplace,
and risk is an assessment of the probability that harm will occur and the severity that would be associated
with that harm (Fuller, 2015). This means that each hazard that is identified in a workplace should be
assessed for risk. When we recommend controls for the identified hazards, the controls are designed to
reduce the risk associated with the hazards. A concept that is important in this process is residual risk.
Residual risk is the risk that remains after you have implemented all feasible controls. You should remember
that if a hazard is present in a workplace, there will always be some level of residual risk present. You cannot
have a hazard present with zero risk. The task of the industrial hygienist is to reduce the residual risk
associated with hazards to an acceptable level (OSHA, 1999).
The question this should raise in your mind is, “what is an acceptable level of risk?” There is no specific
answer to that question. Each industrial hygienist must make a determination of acceptable risk based on
OSH 6302, Advanced Industrial Hygiene
1
published guidelines and the internal policies of the company for which they work.
may think
that the
UNITYou
x STUDY
GUIDE
permissible exposure limits (PELs) established by the Occupational Safety and
Health Administration (OSHA)
Title
represent an acceptable level of risk for exposures. However, as we discussed previously, many of the PELs
are based on outdated scientific research and many have levels of risk that even OSHA does not consider an
acceptable level. This is true because few occupational exposure limits (OELs) have been established in
order to achieve a set level of risk (Wheeler, Park, Bailer, & Whittaker, 2015). OSHA must also consider the
economic and technological feasibility when setting their OELs (Occupational Exposure to Respirable
Crystalline Silica, 2016). So, what does this mean for industrial hygienists trying to evaluate health risks using
sampling data?
Traditionally, risk assessments have been performed using a tool like the risk assessment matrix seen below.
Outcomes
Severity Health
Rating
Likelihood
Very
Likely
Likely
5
4
25
20
Possible
Unlikely
Very
Unlikely
1
5
3
2
Death or
15
10
Permanent
Total
Disability
4
Permanent 20
16
12
8
4
Partial
Disability
3
Injury or
15
12
9
6
3
Illness with
Lost
Workdays
2
Injury or
10
8
6
4
2
Illness with
No Lost
Workdays
1
First Aid
5
4
3
2
1
Only or No
Treatment
By estimating the probability of harm and the associated severity, the industrial hygienist can develop a
semiquantitative risk-assessment result. As you can see, many risk assessment matrices are color coded to
indicate the acceptability of the calculated risk. However, the color coding is not a regulatory result. In other
words, whether you determine a resulting risk score is unacceptable (in red), acceptable (in green), or
somewhere in between (orange or yellow) is a subjective decision. Most industrial hygienists would agree that
a personal exposure that is very likely to occur and that can cause death or permanent total disability would
be unacceptable and that a personal exposure that is very unlikely to occur and that would result in no
treatment or only require first aid if it did occur would be acceptable. What about a personal exposure that is
possible (but not likely) but could cause an illness that would result in the worker missing workdays? Would
that be acceptable or unacceptable? At that level, the industrial hygienist would need to make a judgment call
based on education about the work task, the workers involved in the task, and the potential outcomes of the
exposure. In these cases, you may see different decisions about the acceptability of the risk for different
industrial hygienists working for different companies.
5
The information you can use to evaluate the risk associated with exposures at specific levels would include
existing OELs and an understanding of the toxicological data for the compound(s). Remember, we discussed
many of the toxicological principles in a prior unit. Knowing that one compound is much more acutely toxic
than another compound, by reviewing data such as the Lethal Concentration 50%( LC50), Lowest Observed
Adverse Effect Level (LOAEL), No Observed Adverse Effect Level (NOAEL), Immediately Dangerous to Life
and Health (IDLH) concentrations, carcinogenicity, and mutagenicity, to name a few, may result in you
deciding a risk-assessment result for that compound is unacceptable while the same assessment result for
the second compound may be acceptable.
After you determine that a sample result represents an unacceptable risk, you need to determine which
controls to implement to reduce the risk. In this case, OSHA has established some clear requirements. OSHA
OSH 6302, Advanced Industrial Hygiene
2
requires the use of specific controls be implemented first (or show them to notUNIT
be feasible)
before
other, less
x STUDY
GUIDE
effective controls can be used. The list of controls that OSHA requires to be considered
are commonly called
Title
the hierarchy of controls (OSHA, 2016). The categories of control methods in the hierarchy of controls from
most effective to least effective are elimination/substitution, engineering controls, administrative and work
practice controls, and personal protective equipment (PPE; OSHA, 2016). We will look at
elimination/substitution and engineering controls in this unit and administrative and work-practice controls and
PPE in the following unit.
(Centers for Disease Control and Prevention, 2015)
Elimination and substitution controls are the most effective controls because they completely remove the
hazard of concern from the workplace. By removing the hazard from the workplace, the risk associated with
that hazard is also eliminated (reduced to zero; OSHA, 2016). The primary consideration for substituting an
alternate chemical for the original hazard would be the risk level of the substitute chemical. Substitution is
only effective in reducing risk if the use of the substitute chemical results in a lower health risk to workers than
the original chemical. In order to determine if this is true, the industrial hygienist would have to perform a risk
assessment for both compounds, including a review of toxicological data and perhaps sampling for both
compounds in the workplace. An example of this approach would be if a work task used 100% formaldehyde
for a disinfection process. Since formaldehyde is a known carcinogen, the risk is elevated. If you could find a
chemical that has less potential for harm to workers in the area and it performed the required disinfection
adequately, you could substitute the second chemical for formaldehyde. In practice, elimination/substitution
can be quite difficult to complete because of requirements in the production process. For example, if your
client requires arsine gas to produce computer chips, you could not substitute a nontoxic gas, such as
nitrogen.
The next most effective control method in the hierarchy of controls is engineering controls. These are not as
effective as elimination and substitution because they do not remove the hazard from the work area. Instead,
they are designed to reduce the workers’ exposures to the chemical (OSHA, 2016). Since the hazard is still
present in the work area, some residual risk will remain. The most commonly used engineering control is
ventilation. There are two basic types of ventilation systems: general dilution ventilation and local exhaust
ventilation (Fuller, 2015). The textbook contains a detailed explanation of ventilation systems in Chapter 8.
A general dilution ventilation system simply moves air. The concentration of chemicals in the area are
reduced by bringing in fresh air from outside the area that does not contain any concentration of the chemical
and mixing it with the contaminated air. Some systems will blow air from the work area to areas outside the
OSH 6302, Advanced Industrial Hygiene
3
work area instead. This type of system requires some type of air mover (a fan).
Thexfan
can beGUIDE
as simple as a
UNIT
STUDY
box fan or as complex as a series of fans that pull air from outside the work area
through the ceiling or the
Title
side walls of the building (Fuller, 2015). With this system, the air is typically not filtered or treated in any way.
The air is simply moved from one area to another area, causing uncontaminated air to move into the work
area and reduce the concentrations of contaminants in the area.
Local exhaust ventilation (LEV) systems collect air in an area and move it through some type of treatment or
filtration system or outside through air ducts (Fuller, 2015). The types of filters used or treatments employed
vary depending on the compound(s). For example, particles can typically be collected on filters (or baghouses
with cyclones) placed in the system. Some volatile organic compounds (VOCs) can be adsorbed onto
activated carbon. Acidic aerosols can be passed through a neutralization system. In some cases, isolation
boxes will be included as part of an LEV system. The combination of an isolation device and LEV system are
commonly used in laboratory and medical settings. They are commonly called laboratory hoods or fume
hoods (Fuller, 2015).
If the industrial hygienist recommends a ventilation system, there must be some design work performed. The
textbook shows some examples of the types of calculations that might be required for different types of
ventilation systems. A PowerPoint presentation with more examples is also included for your review. The
calculations are required to make sure the ventilation system design can effectively capture and move air to
the point that employee exposures are reduced as much as is practical. Paying for the installation of a
ventilation system and then discovering that personal exposures were not effectively reduced to an
acceptable risk level can be rather frustrating!
Engineering controls for physical hazards are typically much different than for chemical hazards. Ventilation
systems are ineffective for reducing personal exposures to physical hazards such as noise and radiation.
Engineering controls for physical hazards typically involve installing something to block the exposure before it
reaches the employee. For noise, an effective engineering control is the installation of sound-deadening
material between the noise source and the employee (Fuller, 2015). This can be hanging sound-deadening
curtains or building an isolation box around the noise source using sound-deadening materials. The difficulty
with implementing engineering controls for noise sources is that the sound-deadening materials must be
effective for the primary octave bands of the noise. This may require sampling of the noise using special noise
meters equipped with octave band analyzers. An example that most of you are probably familiar with for
radiation is the installation of lead-lined walls in areas where X-ray machines are used, the lead in the walls
blocks (absorbs) the X-rays to reduce the exposure to workers outside the room.
References
Centers for Disease Control and Prevention. (2015). Hierarchy of controls [Graphic]. Retrieved from
https://www.cdc.gov/niosh/topics/hierarchy/images/HierarchyControls.jpg
Fuller, T. P. (2015). Essentials of industrial hygiene. Itasca, IL: National Safety Council.
Occupational Exposure to Respirable Crystalline Silica, 81 Fed. Reg. 16286 (March 25, 2016) (to be codified
at 29 C.F.R. pts. 1910, 1915, & 1926).
Occupational Safety and Health Administration. (1999). Standard interpretations: Clarification of OSHA’s risk
assessment and approach for setting the asbestos PEL. Retrieved from https://www.osha.gov/lawsregs/standardinterpretations/1999-07-23
Occupational Safety and Health Administration. (2016). Recommended practices for safety and health
programs: Hazard prevention and control. Retrieved from
https://www.osha.gov/shpguidelines/hazard-prevention.html
Wheeler, M. W., Park, R. M., Bailer, A. J., & Whittaker, C. (2015). Historical context and recent advances in
exposure-response estimation for deriving occupational exposure limits. Journal of Occupational and
Environmental Hygiene, 12(Suppl. 1), S7–S17. Retrieved from
https://doi.org/10.1080/15459624.2015.1076934
OSH 6302, Advanced Industrial Hygiene
4
UNIT x STUDY GUIDE
Suggested Reading
Title
In order to access the following resources, click the links below.
The CSU Online Library contains many articles that relate to the Unit VI readings. The following are just a few
of the related articles that can be found in the Academic Search Complete database:
Local exhaust ventilation systems (LEVs) are commonly used in areas where portability is important. Surgical
suites would be one example because of the need to move the LEV depending on where the contaminant
generation occurs. The following article shows how the use of an LEV reduces exposure to both particulate
and volatile organic compounds (VOCs) in a surgical operation.
Lee, T., Soo, J.-C., LeBouf, R. F., Burns, D., Schwegler-Berry, D., Kashon, M., & Harper, M. (2018). Surgical
smoke control with local exhaust ventilation: Experimental study. Journal of Occupational and
Environmental Hygiene, 15(4), 341–350. Retrieved from
https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc
t=true&db=a9h&AN=128834255&site=ehost-live&scope=site
Several variables must be considered when implementing a general dilution ventilation system. One of those
variables is wind velocity. The following article demonstrates how changes in the designed velocity in a
ventilation system can change the protection the ventilation can provide.
Bennett, J., Marlow, D., Nourian, F., Breay, J., Feng, A., & Methner, M. (2018). Effect of ventilation velocity on
hexavalent chromium and isocyanate exposures in aircraft paint spraying. Journal of Occupational
and Environmental Hygiene, 15(3), 167–181. Retrieved from
https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc
t=true&db=a9h&AN=128402085&site=ehost-live&scope=site
There are multiple types of local exhaust ventilation (LEV) systems. The type you use is influenced by the
operation. In some cases, it is better to use a downdraft type LEV. The following article evaluates a mobile
downdraft LEV to determine how well it works at different flow rates.
Lo, L.-M., Hocker, B., Steltz, A. E., Kremer, J., & Feng, H. A. (2017). Performance evaluation of mobile
downflow booths for reducing airborne particles in the workplace. Journal of Occupational and
Environmental Hygiene, 14(11), 839–852. Retrieved from
https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc
t=true&db=a9h&AN=125963641&site=ehost-live&scope=site
The hierarchy of controls shows that elimination/substitution is the most effective control method for reducing
risks associated with health hazards. However, elimination/substitution is not used as often as other control
methods on the hierarchy of controls. The following article summarizes testing that was performed during oil
and gas extraction activities. Toward the end of the article, you will see how these IH professionals
recommended both elimination and substitution controls to reduce the risks during these activities.
Esswein, E. J., Alexander-Scott, M., Snawder, J., & Breitenstein, M. (2018). Measurement of area and
personal breathing zone concentrations of diesel particulate matter (DPM) during oil and gas
extraction operations, including hydraulic fracturing. Journal of Occupational and Environmental
Hygiene, 15(1), 63–70. Retrieved from
https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc
t=true&db=a9h&AN=126995449&site=ehost-live&scope=site
Learning Activities (Nongraded)
Nongraded 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.
OSH 6302, Advanced Industrial Hygiene
5
OSHA considers ventilation to be one of the most important engineering controls.
has devoted
UNITOSHA
x STUDY
GUIDE an
entire section of its website to ventilation. Access the section at
Title
https://www.osha.gov/SLTC/ventilation/index.html. Explore the site to see what information you can find to
assist you in recommending and implementing ventilation controls in a workplace.
OSH 6302, Advanced Industrial Hygiene
6