Health Effects of Hazardous Materials

Health Effects of Hazardous Materials Toxicology • The study of poison & substances that cause harmful effects to living things • Toxic effects can range from minor irritation to lethal effects • Toxins are poisons produced by living organisms (naturally occurring) • Toxicants are manufactured by humans Toxicology • Dose differentiates a poison and a remedy • Harmful substances are tested on animals • How a chemical affects genetic material is determined using microorganisms (i.e bacteria) Toxicity • Relative ability of a substance to cause harmful effects to living things • What quantity does it take to cause damage • Determined by the chemical makeup, what elements it contains and how they are combined, how readily it is absorbed and how the body metabolizes it Dose • Actual amount of chemical that enters and reacts with body systems to cause harm, measured in mass per unit time (mg/kg/day) [milligram of substance per kilogram of tissue per time of exposure] Exposure • The amount of toxic chemical our body comes in contact with • In the air we breathe, the food we eat and our skin is exposed to • The higher the concentration of the exposure the larger the dose • The longer the exposure the larger the dose • Protective clothing, equipment and containment can break the exposure chain Routes of Exposure • • • • Dermal absorption Oral (Ingestion) Inhalation Injection • Inhalation and injection are the most rapid Dermal • May cause itching, redness, burns, and solvents may dissolve skin oils leaving skin more susceptible to the absorption of chemicals • The eyes are especially susceptible to harm Ingestion • Not common in the workplace, but issues of facial cleanliness, and eating are concerns • Is a serious problem at home with children i.e lead paint chips Injection • Greatest risk in medical facilities, or from microbial exposure from nail puncture • Biological sources of toxins as well; insects, scorpions, spiders and snakes! We Will Come Back to Inhalation later • It senses pressure, pain and temperature and regulates the body’s temperature through blood flow and sweat glands • Corrosive chemicals can dissolve naturally protective coatings and/or react with the skin • Some chemicals, like solvents that` dissolve fats, are absorbed directly into the bloodstream Carcinogenicity • The tendency for cancer to occur • Cancer is the uncontrolled growth and spread of abnormal cells • It is first indicated by malignant tumors which tend to invade the surrounding tissue and then spread to distant sites within the body • During the 1970’s the public became aware of the potential for chemicals to cause cancer • Studies of chemicals indicate that only a small number in commercial use cause cancer • One in three people will develop cancer during their lifetime • Yet only 10 – 15% of these are from occupational exposure to chemicals • There are 30 chemicals considered to be human carcinogens and 200 that are suspect based on animal studies Mutagenicity • The ability of a substance to cause damage to genetic material • A substance that is a carciogen is usually a mutagen • But not all mutagens cause cancer Teratogenicity • A substances tendency to interfere with the development of an unborn child • A teratogen causes birth defects Determining Carcinogenicity • Epidemiological studies are retrospective and look at past exposures to a sample group and compare this with their health history • Lifestyle risk contributors like smoking, alcohol consumption and obesity are considered • A prospective study maintains environmental data as well as exposure and medical records on workers as they are exposed • These studies are difficult in companies where there is a large turnover of employees because the latency period of many cancers is over 20 years Animal testing • Usually performed on rodents using procedures endorsed by regulatory agencies like the EPA • Animals are given doses likely to yield maximum incidence of tumor formation then statistical analysis is used to estimate the cancer risk of low doses in humans Risk Management • Government policy is determined by the public’s opinion of acceptable risk and is based on political considerations – Definition of risk – What defines acceptable risk • Risk assessment uses scientific methods to determine the actual level of risk Risk/Benefit Analysis • Used by regulatory agencies in the decision making process • Subjective concerns such as politics, lifestyles, freedoms, economics and progress are considered Perception of Risk • We tend to perceive voluntary risks as less perilous than those we are forced to take i.e smoking Risk Assessment • Evaluating the toxic properties of a substance and the conditions of human exposure to determine • The likelihood that exposed humans will be adversely affected • And describe the nature of the effects they may experience National Research Council Guidelines 1983 • Hazard evaluation - determining the toxic properties of the substance • Dose-response relationships - how much it takes to cause negative effects • Exposure assessment - how much the public is exposed to and for how long • Risk characterization – determining a numerical risk factor Risk Assessment II • Risk assessments are required by regulatory agencies when contaminants have been released into the environment • Aids in determining acceptable cleanup levels [...]... Result of short term exposure • Causes effects that are felt at the time of exposure or soon thereafter • Most toxic effects don’t cause permanent, irreversible damage (acute & chronic) Chronic toxicity • Due to long-term exposure • Effects appear after months or years of exposure • Cancer, emphysema, or nervous system damage caused by heavy metals, drugs and alcohol are examples of some chronic health effects. .. ill effects Lethal Dose 50 (LD50) • Dose at which 50% of the test population dies • Used with dermal and oral toxicity • LC50 - Lethal Concentration used for toxicity from inhalation Effects other than death! • The dose or concentration to produce toxic effects in 50% of the population • Toxic Dosage 50 - TD50 • Toxic Concentration - TC50 Toxic Effects • Local Effects – damage caused at the site of. .. assume that the effects of two chemicals together is equal to the sum of each alone Antagonism • A subtractive effect • One substance reduces the effects of another Synergism • Two chemicals can interact within the body to produce an effect different from the effect of either chemical alone, and greater than their sum • A pack of cigarettes a day or exposure to asbestos increases the chance of lung cancer... diet, state of health, use of medication, drugs, alcohol and pregnancy • Includes Allergies – Some people are affected by a very low dose of a substance (i.e bee stings) – Substances that initiate allergic responses are called sensitizers Respiratory System • Exchange of gases, oxygen in, carbon dioxide out • The air we breathe contains 78% nitrogen, 21% oxygen, and 1% trace gases • Evaporation of liquids... million tiny air sacs where air is exchanged • Oxygen is transferred to hemoglobin within the red blood cells of the bloodstream and carbon dioxide is released Fibrosis • Some particles cause a build up of fibrous connective tissue – Emphysema is an example of this type of effect • Hampers the transfer of oxygen to the bloodstream • Silica from mining, quarrying and pottery glazing, coal dust and asbestos... resultant harmful effects • Some effects take a long time to manifest themselves • For some chemicals, effects may not appear for 30 or 40 years – Example is asbestos Interaction • Chemicals can combine with toxicants and alter their behavior Reaction • Chemicals can combine and form new harmful substances • i.e bleach plus drain cleaner = chlorine gas and hydrochloric acid Additive Effect • Most health and... of first contact with toxicant (eyes, nose, throat, lungs, skin) • Systemic Effects – Damage done by toxicants carried by the bloodstream to vital organs (liver, kidneys, heart, nervous and reproductive system Additional factors associated w/ Toxic Effects • Local effects provide warning that exposure has occurred • Systemic effects may occur without being felt or sensed Accumulation • Chronic, or long... trace gases • Evaporation of liquids such as gasoline or formaldehyde allows them to enter the body Inhalation (Back to Routes of Exposure) • Most critical route of entry for most workers handling toxic chemicals • Quick entry and absorption into the bloodstream • Ability of some toxic agents to accumulate in the respiratory system itself • The nose and mouth warm and humidify the air we breathe •... the alveoli forming acids • Ammonia and chlorine gas can dissolve in the mucus of the lungs creating caustic solutions • Injured lung tissue allows liquids to move from the capillaries into the alveoli causing pulmonary edema • A person can literally drown in their own fluids Smell • Our sense of smell does not always warn of exposure • Carbon monoxide is odorless • We can become desensitized to some... Cardiovascular system • The heart and blood vessels transport oxygen and nutrients to all parts of the body • The heart and brain are especially sensitive to a lack of oxygen • Waste products are picked up and carried to the lungs and kidneys Hemoglobin • An iron containing protein in red blood cells which carry oxygen to the rest of the body • Some chemicals (i.e.CO) interfere with this process causing chemical