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Human Resources Management
HRM 3400
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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. Chemical Agents - 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.’ Chemical States - 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 occupies. - 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 problems. 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 o Dusts  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. o Fumes  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. o Smoke  Product of combustion.  Made up of dusts and vapours. o Gas  Materials whose physical state is a gas at room temperatures. o Vapour  Gases formed when liquid evaporates. o Mists  Suspended liquid droplets created when vapour condenses back to a liquid, or during splashing and atomizing. o Fibers  Solid particles having a slender, elongated shape several times as great as their diameter.  Commonly found in construction, mining, friction products, and insulation materials. - Hazard potential of a chemical depends on: o Which form it takes. o Characteristics such as solubility. o Particle size. o Toxic properties. Toxicity - Ability to cause injury to human biological tissue. - Extent to which a toxic substance is an actual health hazard depends on other factors. Toxicology - Toxicology o Scientific study of poisons (traditional definition). o The study of the adverse effects of chemicals or physical agents on living organisms. o Study of chemical-related occupational illnesses. - Xenobiotic 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). - Toxicant 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 venom). - Dose 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. Dose-Response - Health effects of two chemicals as the dose increases. - Carbon monoxide o No effect. o Headache, nausea and dizziness. o Unconsciousness. o Death. - Formaldehyde 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). - Species. - Age - Sex - Ability to be absorbed. - Metabolism. - Distribution within the body. - Excretion. - Presence of other chemicals. Disposition - Definition o The term used to describe the kinetics of a substance in the body. It encompasses:  Absorption.  Distribution and metabolism.  Elimination of a chemical. Routes of Entry - Three main routes o Respiration (inhalation). o Ingestion. o Skin absorption. - Other routes of entry (mainly for medical purposes) o Injection/skin penetration. o Implants. o Eye. o Suppositories. Absorption - 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 exercise). - Absorption can occur at any place with the upper respiratory tract. - The amount absorbed depends on the chemical’s physical form and solubility. Skin (Dermal) - Complex multilayer tissue. - Largest organ of the body. - Represents a barrier to most xenobiotics. - Three main layers. o Epidermis. o Dermis. 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 - distribution 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 membrane). 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 organism. o Two types:  Detoxification • A metabolic process whereby a xenobiotic substance is changed to another product (metabolite) that has lessened toxicity.  Bioactivation • The metabolic process whereby a xenobiotic is chemically changed to another substance with enhanced biological activity. Remember - 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). Chemical Interactions - 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 neuron damage. - 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 behavioural abnormalities. - 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 fetus. - 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 closed c
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