UNIT II STUDY GUIDE
How an Understanding of Toxicology Helps in the Industrial Hygiene Practice
Course Learning Outcomes for Unit II
Upon completion of this unit, students should be able to:
3. Examine the foundational scientific principles for industrial hygiene practices.
3.1 Summarize some of the common terms used in toxicology.
3.2 Determine the risk to employees based on a review of existing toxicological data.
Reading Assignment
Chapter 4: Basic Concepts in Industrial Toxicology, pp. 6593
In order to access the following resource, click the link below.
Dankovic, D. A., Naumann, B. D., Maier, A., Dourson, M. L., & Levy, L. S. (2015). The scientific basis of
uncertainty factors used in setting occupational exposure limits. Journal of Occupational and
Environmental Hygiene, 12(Suppl. 1), S55S68. Retrieved from
https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc
t=true&db=a9h&AN=111071548&site=ehost-live&scope=site
Unit Lesson
Industrial hygienists require at least a basic knowledge and understanding of a number of scientific
disciplines. Toxicology is one of the more important disciplines for the industrial hygienist. A primary mission
of industrial hygiene is to prevent injuries and illnesses by reducing the risks associated with hazards.
Toxicology data are valuable tools for accomplishing that mission.
Many students have never really given the field of toxicology that much thought, or if you took a class in your
studies, you may have come to the conclusion that toxicology is either too difficult or boring. However, if
shown the following picture, most would automatically say Poison, so there is at least some recognition of
toxicology.
OSH 6302, Advanced Industrial Hygiene
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UNIT x STUDY GUIDE
Title
Toxicology is the study of poisons.
(Brutlag, n.d.)
As your textbook has pointed out, the most common definition of toxicology is the study of poisons (Fuller,
2015). This should automatically bring up several questions for the aspiring industrial hygienist. How can
toxicological data be used to help you with your job? Where can you find the data that can help you? How can
you translate this stuff into something you can understand? This lesson will not make you an expert on
toxicology. You will have to take the advanced toxicology class for your masters degree, and that class will
go in depth much more than this one unit. However, this lesson is designed to help you understand where you
can obtain data to assist you with industrial hygiene work and some basic understanding of what the data
mean.
A basic saying in toxicology is the dose makes the poison. Loosely, this means that at a low enough
exposure, chemicals will not cause harm, but as the exposure increases, the risk of harm also increases. You
can reach an exposure level where harm actually occurs. In controlling risk, it would be nice if we could
identify that point and make sure no workers were ever exposed to a chemical at that level. One objective of
toxicology studies is to identify the dose below which harm does not occur. A common way that data is
displayed is the dose-response curve. An example of a dose-response curve can be seen on page 79 of the
textbook (Fuller, 2015).
Dose-Response
The textbook calls the point at which some response occurs (for Figure 4-2 the response is percent of liver
hypertrophy) the threshold dose (Fuller, 2015). Some more commonly used terms in toxicology are lowest
observed adverse effect level (LOAEL) and no observed adverse effect level (NOAEL). The LOAEL
represents the lowest exposure at which some response was recorded (typically from animal studies). The
NOAEL represents the highest dose at which no response was seen. This appears to make it fairly simple to
just say, lets keep the workers exposures less than the NOAEL and then no one will get sick! However, it is
not quite that simple.
First, most NOAELs are generated based on animal studies. Results from animal studies do not translate
directly to humans for various reasons including differences in body sizes (weight) and differences in body
functions (hormones, etc.). Second, there can be wide variations in how individual workers react to an
exposure to a chemical. Differences in gender, weight, age, and even a persons genetic sequences can alter
the concentration at which they would react and the level of the reaction (Wheeler, Park, Bailer, & Whitaker,
2015). For this reason, organizations that establish occupational exposure limits (OELs) typically apply a
safety factor. The level of the safety factor will depend on how serious the health effect may be.
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The dose-response curve can inform us of the level of toxicity compared to other
compounds
the size of
UNIT
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the safety factor that must be applied. When you look at dose-response curves,
you will see many different
Title
slopes to the curves. Some are quite steep, while others are rather shallow. If you think about this, it should
indicate to you that the compounds with a relatively steep slope only take a small increase in dose to greatly
increase the response, while compounds with a shallow curve require a much greater increase in dose to
cause a significant increase in the response.
Other terms that can be important for an industrial hygienist trying to assess the risk to a health hazard
include the LD50 and LC50. These terms represent the dose at which 50 percent of an exposed population die.
LD50 is used when the exposure occurs by ingestion or dermal exposure. LC50 is used when the exposure is
by inhalation. Both of the terms represent acute exposures, meaning they are short-term exposures with
acute effects. In other words, they are not used for chronic exposures resulting in chronic diseases like
cancer. Other results that are not reported as often in safety data sheets (SDS) are TC Lo, TC50, TDLo, and
TD50. These terms are quite similar to the LD50 and LC50 except they identify the dose or concentration where
50 percent of the subjects show some toxic response or the lowest dose or concentration where any subject
shows the toxic response.
Target Organs
Another piece of information that can be important to the industrial hygienist is the target organ. Many
compounds will exert a toxic effect to one or more specific organs of the body. Knowing which organ a
compound could affect can help in determining the best protective measures to use. For example, if a
compound is known to primarily be a lung toxin, reducing personal exposures by inhalation would be
somewhat important.
Some compounds are immunotoxins. These compounds can cause unique problems for the industrial
hygienist. Some compounds, after repeated exposures, can cause a sensitization reaction (allergic response)
in a small percentage of exposed workers. These workers will exhibit future responses to much lower
concentrations of the chemical. The response can be either a respiratory reaction or a dermal reaction. Some
of the common chemicals used in industrial settings that can be immunotoxins are formaldehyde, some of the
isocyanates, some metal fumes, and bisphenol A (BPA). Some plants have had to move workers to other
areas of a facility because of these reactions.
Chronic Health Effects
Another important consideration is whether a compound can cause chronic health effects. Most workers are
highly concerned about a compounds ability to produce cancer. Compounds that can cause cancer are called
carcinogens. Some cancers start as changes in the DNA called mutations. Chemicals that can cause these
mutations are called mutagens. Not all mutations result in cancer. All humans suffer some mutations during
their lifetime. For the most part, the mutations are benign and are eliminated as the body turns over cells in a
process called apoptosis. However, sometimes the mutations result in an uncontrolled growth of cells
resulting in cancer. Also, not all cancers start with a mutation. Asbestos is a good example of a carcinogen
that is not a mutagen. There are several organizations that rate the carcinogenicity of compounds the
industrial hygienist may see. The two that most industrial hygienists refer to the most are the Occupational
Safety and Health Administration (OSHA) and the American Conference of Governmental Industrial
Hygienists (ACGIH). You can generally find the carcinogenic ratings of compounds in Section 11 of the SDS.
Finally, the industrial hygienist should also consider a chemicals ability to affect reproductivity (reproductive
toxins) or the development of a fetus (teratogens). In some settings, this can be rather important to protect
workers. For example, most of the anti-neoplastic drugs used in chemotherapy are also reproductive toxins
and teratogens. There are numerous published studies showing spontaneous abortions in females working in
oncology clinics due to exposures to these drugs. An industrial hygienist working in an oncology clinic would
need to set up a rigorous program to reduce the risk associated with handling these drugs.
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References
UNIT x STUDY GUIDE
Title
Brutlag, C. (n.d.). Poison sign (ID 2863549) [Photograph]. Retrieved from
https://www.dreamstime.com/royalty-free-stock-images-poison-sign-image2863549
Fuller, T. P. (2015). Essentials of industrial hygiene. Itasca, IL: National Safety Council.
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), S7S17. https://doi.org/10.1080/15459624.2015.1076934
Suggested Reading
In order to access the following resources, click the links below.
The CSU Online Library contains many articles that relate to the Unit II readings. The following are just a few
of the related articles that can be found in the Academic Search Complete database.
There are several methods used to establish occupational exposure limits (OELs). The following article looks
at several of the organizations, including a discussion of how toxicological data are used in the process.
Deveau, M., Chen, C.-P., Johanson, G., Krewski, D., Maier, A., Niven, K. J., Niemeier, R. W. (2015). The
global landscape of occupational exposure limitsImplementation of harmonization principles to
guide limit selection. Journal of Occupational and Environmental Hygiene, 12(Suppl. 1), S127S144.
Retrieved from
https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc
t=true&db=a9h&AN=111071550&site=eds-live&scope=site
One concept you were introduced to in this lessson is the use of biomarkers for evaluating the risk associated
with some health hazards. The following article discusses the use of some biomarkers to detect
overexposures at an early stage.
DeBord, D. G., Burgoon, L., Edwards, S. W., Haber, L. T., Kanitz, M. H., Kuempel, E., Yucesoy, B. (2015).
Systems biology and biomarkers of early effects for occupational exposure limit setting. Journal of
Occupational and Environmental Hygiene, 12(Suppl. 1), S41S54. Retrieved from
https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc
t=true&db=a9h&AN=111071547&site=ehost-live&scope=site
Genetic research has made great advances in recent years, including the study of how specific genetic
markers can be used to predict health risks. These studies complement the toxicological data that we studied
in this lesson. The following article summarizes some considerations in using genetic markers.
Schulte, P. A., Whittaker, C., & Curran, C. P. (2015). Considerations for using genetic and epigenetic
information in occupational health risk assessment and standard setting. Journal of Occupational and
Environmental Hygiene, 12(Suppl. 1), S69S81. Retrieved from
https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc
t=true&db=a9h&AN=111071546&site=ehost-live&scope=site
The point of departure (POD) is a variable commonly used when setting OELs. The dose-response
relationship that we learned about in this lesson is important to the POD. The following article describes how
the dose-response relationship and POD are used in setting OELs.
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), S7S17. Retrieved from
https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc
t=true&db=a9h&AN=111071554&site=ehost-live&scope=site
OSH 6302, Advanced Industrial Hygiene
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Learning Activities (Nongraded)
UNIT x STUDY GUIDE
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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.
The National Institute for Occupational Safety and Health (NIOSH) publishes the NIOSH Pocket Guide to
Chemical Hazards. Access the pocket guide at https://www.cdc.gov/niosh/docs/2005-149/pdfs/2005-149.pdf
and search for several chemicals. Look at the columns of information for each chemical, and see if there are
any terms you learned about in Chapter 5. How do you think you can use that information in controlling the
risk to health hazards?
OSH 6302, Advanced Industrial Hygiene
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