Occupational Health & Safety Management
HRM 3400 – Winter 2012 – Anna Blake
Lecture 2 – Chemical/Biological Agents – Jan 16
WHMIS Class – D
- D – Poisonous and infectious material
o D1 – materials causing immediate and serious toxic effects.
o D2 – materials causing other toxic effects.
o D3 – biohazardous infectious material.
- 70,000 chemical agents used in N.A.
- 800 new ones introduced each year.
- No toxicity data on about 80% of the chemicals.
- 80% of occupational illnesses are a result of chemical exposures.
o Cancer, lung diseases, blood abnormalities, nervous system disorders,
birth defects, skin problems and sterility.
Relevant Legislative Requirements
- Ontario occupational health and safety act
o Sections 33, 35, 37-39.
- WHMIS regulation
- Ontario regulation 490/09 – designated substances.
- Regulation respecting control of exposure to biological or chemical agents
o Provides that employers shall take ‘all measures reasonably necessary in
the circumstances to protect workers from exposure to a hazardous
biological or chemical agent because of the storage, handling, processing
or use of such agent in the workplace.’
- Chemicals exist in three natural states
o Solid – has a definite shape and volume regardless of the container into
which it is placed.
o Liquid – a quantity of liquid has a definite volume, but takes on the shape
of its container.
o Gas – a quantity of gas has the shape and volume of the container it
- State is determined by temperature and pressure.
- Chemicals have different melting, freezing and boiling points.
- Liquid and gas/vapour states result in the majority of chemical – related health
Aerosols - Airborne respirable contaminants, such as liquid droplets, solid particulate, or
vapours dispersed in air that are of a fine enough particle size (0.01 to 100
micrometres) to remain suspended for a period of time.
- Setting rate.
o The time in seconds that it takes for an airborne particle to fall one foot.
The larger the suspended particle the smaller the settling rate.
Seven Types of Aerosols
Solid particles generated by handling, crushing, grinding, impacting,
detonation and breaking apart by heating materials.
Respirable dust means the particles are in a size range that permits
them to penetrate deep into the lungs upon inhalation.
Volatile solids that condense when they contact air.
Very small, solid particles created when hot vapour reacts with the
air to form oxides.
Often associated with welding operations.
Product of combustion.
Made up of dusts and vapours.
Materials whose physical state is a gas at room temperatures.
Gases formed when liquid evaporates.
Suspended liquid droplets created when vapour condenses back to
a liquid, or during splashing and atomizing.
Solid particles having a slender, elongated shape several times as
great as their diameter.
Commonly found in construction, mining, friction products, and
- Hazard potential of a chemical depends on:
o Which form it takes.
o Characteristics such as solubility.
o Particle size.
o Toxic properties.
- Ability to cause injury to human biological tissue.
- Extent to which a toxic substance is an actual health hazard depends on other
Toxicology - Toxicology
o Scientific study of poisons (traditional definition).
o The study of the adverse effects of chemicals or physical agents on living
o Study of chemical-related occupational illnesses.
o General term used to describe a foreign substance taken into the body.
o Includes those that
Produce beneficial effects (pharmaceuticals).
May be toxic (lead).
o Material that causes adverse biological effects.
o Other terms: toxin, poison, toxic agent, toxic substance, toxic chemical.
o May be chemical (cyanide), physical (radiation), or biological (snake
o The amount of a substance administered at one time.
Two Types of Toxic Substances
- Systemic toxin
o Affects the entire body of many organs rather than a specific site.
E.g. potassium cyanide affects virtually every cell and organ in the
body by interfering with the cell’s ability to utilize oxygen.
- Specific organ toxin
o Affects only specific tissues or organs.
o Sites are called target organs or target tissue.
E.g. Benzene is primarily toxic to the blood-forming tissues.
E.g. lead has three target organs: central nervous system, kidney
and hematopoietic (blood) system.
- Health effects of two chemicals as the dose increases.
- Carbon monoxide
o No effect.
o Headache, nausea and dizziness.
o No effect.
o Slight irritation of the eyes and nose.
o Tearing of the eyes.
o Difficult breathing, serious inflammation of the breathing passages.
o Pulmonary edema (fluid in the lungs).
o Death. Lethal Dose
- LD (0ethal dose 0%) or Threshold
o The estimated dose at which none of the population is expected to die.
- LD (10thal dose 10%)
o The estimated dose at which 10% of the population is expected to die.
- LD (50thal Dose 50%)
o The estimated dose at which 50% of the population is expected to die.
Exposure vs. Toxicity
- Acute exposure.
- Chronic exposure.
- Acute toxicity.
- Chronic toxicity.
Factors Influencing Toxicity
- Dose characterized by the number of doses, concentration of the toxin,
frequency and total time period.
- Form and innate chemical activity.
- Exposure route (determines absorption and distribution pathways).
- Ability to be absorbed.
- Distribution within the body.
- Presence of other chemicals.
o The term used to describe the kinetics of a substance in the body. It
Distribution and metabolism.
Elimination of a chemical.
Routes of Entry
- Three main routes
o Respiration (inhalation).
o Skin absorption.
- Other routes of entry (mainly for medical purposes)
o Injection/skin penetration.
o Implants. o Eye.
- The process whereby a substance moves from outside the body into the body.
- Factors that affect the likelihood a chemical will be absorbed.
o Route of exposure.
o Concentration of the substance at the site of contact.
o Chemical and physical properties of the substance.
Inhalation – Respiratory System
- Average human breathes 8 litres of air/minute while at rest (increases with
- Absorption can occur at any place with the upper respiratory tract.
- The amount absorbed depends on the chemical’s physical form and solubility.
- Complex multilayer tissue.
- Largest organ of the body.
- Represents a barrier to most xenobiotics.
- Three main layers.
o Subcutaneous tissue.
- Skin absorption depends on:
o Chemistry of the chemical.
Size of the molecules.
Polarity (electric charge)
Solubility of the chemical
o Condition of the skin.
o Location of the skin.
Ingestion – Gastrointestinal Tract
- Three main factors affect absorption within GI tract.
o Type of cell at specific site.
o Period of time the substance remains at site.
o pH of stomach or intestinal contents.
Distribution and Metabolism
o Movement of a substance from the site of entry to other parts of the body.
o Ultimately determines the sites where toxicity occurs.
o Major determinant of damage to a cell is lipid solubility (ability to penetrate
o Typical storage sites: fat tissue, liver, kidney, and bone. - Bioaccumulate
o The buildup of a substance in a biological organism such that the level in
the organism is greater than in the environmental source of the substance.
- Body burden
o The concentration of a substance that has accumulated in the body.
- Biotransformation (Metabolism)
o Conversion of a chemical from one form to another by a biological
o Two types:
• A metabolic process whereby a xenobiotic substance is
changed to another product (metabolite) that has lessened
• The metabolic process whereby a xenobiotic is chemically
changed to another substance with enhanced biological
- A highly toxic chemical which is poorly absorbed may be no more of a hazard
than a substance of low toxicity that is highly absorbed.
- Two substances with equal toxicity and absorption may differ in hazard
depending on the nature of their biotransformation. A substance biotransformed
into a more toxic metabolite (bioactivated) is a greater hazard than a substance
that is biotransformed into a less toxic metabolite (detoxified).
- The effect that one chemical has on the toxic effect of another:
o Additivity – a combination of two or more chemicals is the sum of the
expected individual responses.
o Antagonism – exposure to one chemical results in a reduction in the effect
of the other chemical.
o Potentiation – exposure to one chemical result in the other chemical
producing an effect greater than if given alone.
o Synergism – exposure to one chemical causes a dramatic increase in the
effect of another chemical.
Classification of Toxicants by Effect on the Body
- Irritant – produces damage at point of contact.
o Inhaled irritants.
o Contact irritants.
- Asphyxiants – interferes with oxygen supply.
o Simple asphyxiants.
o Chemical asphyxiants (results in tissue hypoxia).
- Anesthetics and Narcotics – affects the central nervous system. - Systemic poisons – damage to one or more internal organs as well as cell and
- Liver toxicants (hepatoxin) – chemicals that have direct damage to the liver.
- Kidney toxicants (nephrotoxin) – chemicals that cause damage to the kidneys.
- Neurotins – materials that affect the nerve cells and may produce emotional or
- Sensilizers – cause the body’s immune system to respond abnormally to produce
antibodies against a chemical allergic reaction.
- Lung toxicants – irritate or damage the lung tissue and cause a variety of
diseases from simple pneumoconiosis to cancer.
- Mutagens – lead to changes or mutations in DNA.
- Teratogens – cause damage to germ cells or create defects in a developing
- Carcinogens – cause or promote the formations of cancers.
Characteristics and Properties of Chemicals
- Vapour pressure
o The pressure exerted by a saturated vapour above its own liquid in a