There have been claims that toxic chemicals have made their way into our food, clothing, and communities. What are your thoughts regarding this statement? Provide some examples of toxins that have been released into the environment and the related human health and environmental concerns. Discuss what you believe can be done to limit the impacts of toxic chemicals at your workplace, home, or the environment.
UNIT IV STUDY GUIDE
Chemistry of Toxic Substances
Course Learning Outcomes for Unit IV
Upon completion of this unit, students should be able to:
1. Examine chemistry fundamentals.
1.1 Recognize the chemical and physical properties of common toxic materials.
2. Analyze chemical interactions as they relate to control of potential hazards.
2.1 Determine the chemical interactions of some common toxic materials and associated hazards.
5. Research important standards related to hazardous substances.
5.1 Describe workplace-related standards for some common toxic materials.
Course/Unit
Learning Outcomes
1.1
2.1
5.1
Learning Activity
Unit Lesson
Chapter 10, pp. 366440
Unit IV Assessment
Unit Lesson
Chapter 10, pp. 366440
Unit IV Assessment
Unit Lesson
Chapter 10, pp. 366440
Unit IV Assessment
Required Unit Resources
Chapter 10: Chemistry of Some Toxic Substances, pp. 366440
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UNIT x STUDY GUIDE
Unit Lesson
Title
We studied some interesting hazardous materials in Unit III that are found not only in the workplace but also
at home. In Unit IV, we move on to study the chemistry of toxic materials. The term toxic is synonymous with
poison, identified with a skull and crossbones. Toxic materials are
covered in Chapter 10 of our textbook.
You may notice that some of the corrosive hazardous materials that
we covered so far can also be classified as toxic because some
materials can possess multiple hazardous characteristics. When
these hazardous materials are transported, both the primary and
subsidiary U.S. Department of Transportation (DOT) hazard class
or division number must be displayed, if applicable, on the lower
corner of a placard.
Black and white skull and cross bones
(Close, n.d.)
Toxic substances (also known as toxicants or poisons) can cause
injury, illness, or possibly death when the body is exposed to them,
even in small quantities. As such, these substances require special
attention during their manufacture, storage, transport, use, or
emergency response incidents. Toxic materials are not always
encountered in the product or waste form but could also be an
intermediate product that gets formed from the interaction of raw
materials or products. An example of a toxic substance
encountered at fire incidents is carbon monoxide (CO).
Chapter 10 focuses on some common toxic substances that could be present as an environmental health and
safety and fire science professional perform their duties. Some of these substances, which include carbon
monoxide and hydrogen sulfide, are briefly discussed below and are covered in more detail in the textbook.
Warfare agents, such as ricin, are also briefly discussed. As with the previous units, workplace regulations,
transport requirements, and recommended incident response actions are also discussed in the textbook.
Toxicology
To understand toxic materials better, it is important to become familiar with some basic terminologies and
concepts in toxicology. Specifically, toxicology studies the symptoms, mechanisms, treatments, and detection
of poisoning, especially the poisoning of people (Smith, n.d.). Toxicology, which is a field on its own,
investigates how toxic substances adversely affect a living organism, the diseases they may cause, the
concentrations at which the onset of the adverse effect is noted, and ways to prevent or minimize the effect.
Epidemiology
Another term that we need to understand is epidemiology, which is the study of the adverse effects of these
toxic substances and diseases, specifically how, when, and where they occur. It investigates the distribution
of health-related events (World Health Organization [WHO], n.d.).
Exposure Pathways
As you may already know, you can be exposed to toxic substances by inhalation, oral ingestion, and skin
absorption. These exposure pathways are explained in more detail in Section 10.2 of our textbook. Oral
ingestion is swallowing the toxic material by eating or drinking the material. Inhalation is breathing a material,
which can be a gas, vapor, dust, or fumes. In skin absorption, the toxic material can enter the body because
of exposure to the substance through the skin.
You will also review the following common ways that toxic materials can adversely impact health (Meyer,
2020).
Exposure may cause immediate dysfunction, impairment, or death.
Exposure may affect only the site of contact; this is known as the local effect.
Exposure may affect the whole body, so the ailment is not localized; this is called a systemic effect.
OSH 3308, Interactions of Hazardous Materials
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GUIDE
Exposure may target specific organs. There are specific terminologiesUNIT
usedxtoSTUDY
describe
these toxic
substances, which are listed below.
Title
o Hemotoxin is a substance that decreases the function of the bloods hemoglobin and deprives the
tissues of oxygen.
o Hepatotoxin is a substance that causes liver damage.
o Nephrotoxin is a substance that causes kidney damage.
o Neurotoxin is a substance that adversely affects the central nervous system (the brain and spinal
cord).
o Respiratory toxin is a substance that adversely affects the nasal passages, pharynx, trachea,
bronchi, and lungs.
o Reproductive toxin is a substance that adversely affects sexual function and fertility in adults, as
well as development in their offspring.
Toxic substances can also be classified as described below.
Asphyxiant, according to Meyer (2020), is any gas or vapor that dilutes or displaces air when inhaled.
It can cause unconsciousness or death. An asphyxiant interferes with oxygenation of the tissues, and
the affected individual may suffocate. According to Plog (1988), these are generally divided into the
following categories.
o Simple asphyxiant is an inert gas that displaces oxygen, thus reducing its availability for normal
breathing. Examples include helium, hydrogen, methane, and nitrogen.
o Chemical asphyxiant is one that prevents or interferes with the uptake or transport of oxygen
through their chemical action. Examples: Carbon monoxide prevents oxygen transport by
preferentially combining with hemoglobin; hydrogen sulfide paralyzes the respiratory center of the
brain and the olfactory nerve.
Another type of asphyxiant is one that hinders the cells ability to utilize oxygen. An example is hydrogen
cyanide. On this, fresh air may not revive those exposed, but an antidote may be effective.
An irritant is any substance that, on immediate, prolonged, or repeated contact with living tissue,
induces a local inflammatory reaction (Meyer, 2020). Note that irritants are not just gases or vapors.
They can be solids or liquids such as acidic materials.
The harmful effects of toxic substances can be classified as chronic, acute, short-term, and latent health
effects (Meyer, 2020). Since everyone is different, the effects of the toxic substances vary to a certain degree
based on several factors, which include:
amount of toxic substance that is inhaled, ingested, or absorbed;
length of time of exposure;
rate at which the toxic substance is absorbed in the bloodstream;
age, sex, ethnicity, and general health of individuals (for example, the elderly could be more
sensitive); and
individual sensitivities (could be genetic).
According to Meyer (2020), measures of toxicity are classified as shown below.
Lethal dose, 50% kill, or LD50: Dose when 50% of a test group die
Lethal concentration, 50% kill, or LC50: Concentration of the substance that kills 50% of a test group
Threshold limit value-time-weighted average (TLV-TWA): A TWA concentration under which most
people can work consistently for 8 hours a day, day after day, without harmful effects (Plog, 1988)
Permissible and ceiling exposure limit
Short-term exposure limit
Observed adverse effect level
Immediately dangerous to life and health limit
Recommended exposure limit (REL)
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Hazard zones are assigned to gases and liquids based on their LC50s. Emergency
use these
UNIT xresponders
STUDY GUIDE
hazard zones to determine how toxic a material is.
Title
As indicated above, Chapter 10 discusses the chemical properties, production methods, interactions, and
transportation requirements as well as workplace and environmental regulations of the following toxic
materials.
Carbon Monoxide (CO)
CO is commonly found at a fire scene and is the result of incomplete combustion (meaning there is not
enough oxygen/air to burn an organic material, which is not necessarily hazardous completely). CO is an
odorless, colorless, tasteless, and nonirritating gas at ordinary room conditions (Meyer, 2020). Commercially,
CO is produced by coal gasification (refer to Section 7.2-C of the textbook) and is used by the chemical
industry for the production of other chemicals such as methanol. CO is also used to reduce metallic oxides to
their corresponding metals.
Ammonia
Ammonia is another toxic material that is
commercially used and can potentially be
encountered in the workplace. It is used in
household cleaning at low concentrations of 2%
to 5%. If ammonia is used at a workplace, the
Occupational Safety and Health Administration
(OSHA) requires employers to post a sign in the
work area and to limit employee exposure to a
concentration of 50 parts per million (35 mg/m3)
averaged over an 8-hour workday (Meyer, 2020).
Anhydrous ammonia tank
A common use of ammonia is in refrigeration
(Pavelka, n.d.)
systems. Another important use, although
probably not as well-known, is in the control of
NOx emissions from combustion units discussed above. Ammonia is injected in the exhaust stream of the
combustion system that is equipped with a selective or non-selective catalytic reduction (SCR/NSCR) to
convert nitrous oxides (NOx) to nitrogen.
Sulfur Dioxide (SO2)
SO2 is also a colorless and toxic gas that has a sharp pungent odor similar to the smell of burning matches or
tires. Just like CO and hydrogen cyanide (HCN), SO2 is produced and used commercially. It can be available
as a liquefied compressed gas. Some of its commercial uses include a bleaching agent by the pulp and paper
industry and as fumigants in the agricultural business.
It should be noted that SO2 is a criteria air pollutant regulated under the Clean Air Act (CAA). A primary
anthropogenic source is from the combustion of fossil fuels, mainly coal and crude oil. A well-known adverse
effect of SO2 air emissions is the formation of acid rain, which has ecological effects on aquatic environments
and forest health.
Hydrogen Sulfide (H2S)
H2S is a colorless, flammable, and toxic gas that has a rotten egg smell. This smell is detectable by humans
at just 2 ppb concentration (Meyer, 2020). After long-term exposure to low concentrations, workers sense of
smell is deadened to the extent that they become oblivious to the presence of H2S. The temporary inability to
identify the odor of an airborne material is known as olfactory fatigue. OSHA requires employers to limit
employee exposure to 20 parts per million over an 8-hour workday and a maximum concentration of 50 parts
per million in a 10-minute maximum period (OSHA, n.d.).
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NOx
UNIT x STUDY GUIDE
Title
NOx can be defined as oxides of nitrogen, eight of which are known but only two are of concern: nitric oxide
(NO), which is also known as nitrogen monoxide, and nitrogen dioxide (NO 2). When NOx is mentioned, it is
usually referring to NO and NO2. NO is used in hospitals and clinics, while NO2 is used by the aerospace
industry to oxidize rocket fuels (Meyer, 2020). NOx is produced for commercial use, but it is also a criteria air
pollutant resulting mainly from the combustion of fossil fuels at power plants, manufacturing facilities, and
automobiles. As indicated in Unit II, NOx is a precursor to the bad ozone, which is why it is regulated under
the CAA. Hydrocarbons and NOx in the presence of sunlight form ozone.
Asbestos mine remains in Coleraine village
(Rivard, n.d.)
Other toxic materials that are discussed in the textbook that may be encountered are asbestos, hydrogen
cyanide, infectious pathogens and toxins, agricultural pesticides, and carcinogens. Asbestos has been
regulated for some time now but can still be present in old buildings that have not been renovated and in
piping. When asbestos is completely sealed, there is no health hazard. However, if it is in a friable form
(crushed), there is a risk of inhaling airborne fibers.
References
Centers for Disease Control and Prevention. (n.d.). What is epidemiology?
https://www.cdc.gov/careerpaths/k12teacherroadmap/epidemiology.html
Close, C. R. (n.d.). Black and white skull and crossbones skeleton detail print (ID 98473378) [Photograph].
Dreamstime. https://www.dreamstime.com/stock-photo-black-white-skull-cross-bones-skeleton-detailprint-england-uk-image98473378
Meyer, E. (2020). Chemistry of hazardous materials (L. Mauerman, Ed.; 7th ed.). Pearson.
Occupational Safety and Health Administration. (n.d.). Hydrogen sulfide hazards.
https://www.osha.gov/SLTC/hydrogensulfide/hazards.html
Pavelka, T. (n.d.). Anhydrous ammonia tank. Orange, tube (ID 30205079) [Photograph]. Dreamstime.
https://www.dreamstime.com/royalty-free-stock-images-anhydrous-ammonia-tank-warning-signimage30205079
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Plog, B. A. (1988). Fundamentals of industrial hygiene (3rd ed.). National Safety
Council.
UNIT
x STUDY GUIDE
Title
Rivard, L. (n.d.). Asbestos mine remains in Coleraine village (ID 108824670) [Photograph]. Dreamstime.
https://www.dreamstime.com/asbestos-mine-remains-coleraine-village-asbestos-mine-now-closedyou-can-see-installation-coleraine-park-moon-image108824670
Smith, Y. (n.d.). What is toxicology? News Medical Life Sciences. https://www.news-medical.net/health/Whatis-Toxicology.aspx
Suggested Unit Resources
In order to access the following resources, click the links below.
Review the PowerPoint presentation on Chapter 10 to supplement the textbook reading and lesson content.
Access the Chapter 10 PowerPoint Presentation (PDF version of the Chapter 10 presentation).
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.
In order to access the following resources, click the links below.
You are encouraged to engage with the Chapter 10 Flash Card Activity (PDF version of the flash card
activity), which reinforces the concepts presented in the unit lesson and chapter readings.
OSH 3308, Interactions of Hazardous Materials
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