Health Effects of Hazardous Materials

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Health Effects of Hazardous Materials
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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

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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)

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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

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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

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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

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Routes of Exposure

• Dermal absorption
• Oral (Ingestion)
• Inhalation
• Injection
• Inhalation and injection are the most rapid

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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

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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

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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

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Acute toxicity
Back to toxicity

• Result of short term exposure
• Causes effects that are felt at the time of
  exposure or soon thereafter
• Most toxic effects dont cause permanent,
  irreversible damage (acute chronic)

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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

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Relative toxicity

• As the dose of a toxic substance increases the
  harmful effects are generally expected to
  increase
• Dose-Response Relationship
• LOAEL Lowest Observable Adverse Effect Level -
  or the lowest dose that causes a lethal effect
• NOAEL - No Observable Adverse Effect Level

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Threshold level

• The lowest concentration that could produce a
  harmful effect (doesnt necessarily mean lethal)
• Varies among people exposed depending upon their
  sensitivity
• A safety factor is used to reduce the allowable
  concentration to assure no ill effects

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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

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Effects other than death!

• The dose or concentration to produce toxic
  effects in 50 of the population
• Toxic Dosage 50 - TD50
• Toxic Concentration - TC50

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Toxic Effects

• Local Effects damage caused at the site 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

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Additional factors associated w/ Toxic Effects

• Local effects provide warning that exposure has
  occurred
• Systemic effects may occur without being felt or
  sensed

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Accumulation

• Chronic, or long term exposure is particularly
  dangerous because some chemicals build up in the
  body
• The body does not get a chance to repair itself

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Latency Period

• The delay between the exposure and the 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

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Interaction

• Chemicals can combine with toxicants and alter
  their behavior

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Reaction

• Chemicals can combine and form new harmful
  substances
• i.e. bleach plus drain cleaner chlorine gas and
  hydrochloric acid

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Additive Effect

• Most health and safety regulations assume that
  the effects of two chemicals together is equal to
  the sum of each alone

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Antagonism

• A subtractive effect
• One substance reduces the effects of another

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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 by
  six times
• The two exposures together increases ones risk
  by 90 times!

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Sensitivity

• Individuals vary in how they react
• Age, sex, inherited traits, 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

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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 such as gasoline or
  formaldehyde allows them to enter the body

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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

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• The nose and mouth warm and humidify the air we
  breathe
• The bronchial tubes lead to alveoli, 300 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

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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

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Inhaling dusts or mists

• Harmful particles may be deposited in the bronchi
  or the alveoli
• Larger particles may be coughed up but smaller
  ones remain to cause lung damage
• Particles less than 10 microns penetrate deeper
  into the lungs causing bronchitis
• Low level long term exposure to smoke, vehicle
  exhaust can trigger chronic bronchitis and
  emphysema

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• Sulfur dioxide and nitrogen oxides combine with
  water vapor in 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

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Smell

• Our sense of smell does not always warn of
  exposure
• Carbon monoxide is odorless
• We can become desensitized to some smells after
  exposure olfactory fatique
• Example is H2S (page 81)

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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

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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 asphyxiation
• Hemoglobin has a much greater affinity for CO
  than oxygen (300 times greater)

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Digestive and Filtration Systems

• Food and water supply the body with materials for
  maintenance and repair and a source of energy
• The digestive system breaks down large molecules
  like proteins, complex carbohydrates and fats

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Liver

• Processes chemicals found in the blood traveling
  from the intestine
• Converts foods into other chemicals, destroys
  toxins, manufactures protein and stores glucose

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Liver Disease

• Severe liver disease prevents the organ from
  rendering toxic chemicals harmless, some which
  may be normal body chemicals
• When they reach the brain they may cause tremors,
  confusion or coma

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• Some chemicals are stored in the liver
• The liver can destroy toxic substances like
  alcohol and nicotine
• If exposure is chronic and long term, cells may
  be damaged and replaced by fibrous tissue, a
  condition called cirrhosis

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Bloodstream and Kidneys

• Our body fluids must maintain a balanced amount
  of potassium, sodium, chloride and calcium ions
  and blood acids
• The kidneys maintain this balance and filter out
  waste materials

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• The body must remain hydrated for the kidneys to
  perform their function
• If the body loses more that 10 of its weight in
  water cells will no longer function and the
  result is coma death
• Kidney malfunction causes toxic chemicals to
  build up in the bloodstream which can result in
  coma and death

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• Kidney cancers are known to be associated with
  exposure to some industrial chemicals
• Mercury in waterways is converted to methyl
  mercury, which is ingested by fish
• If the fish are eaten the chemical inhibits the
  kidneys ability to balance the bodys chemicals
  which blocks nerve transmissions, Minimata
  Disease

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Nervous System and Sensory Organs

• Brain, spinal cord are considered the central
  nervous system and process signals from the
  peripheral nervous system
• The two types of nerves are motor and sensory
• The autonomic nervous system takes care of all
  the bodily functions which are in the background

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• Pesticides and metals, such as lead and mercury,
  can interfere with the chemical transfer of
  information
• This may cause tremors, paralysis, loss of
  reflexes and/or feeling
• Mercury caused Mad Hatters Disease

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Brain

• Must receive a continuous supply of oxygen
• See chart on page 86 for symptoms of oxygen
  deficiency

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Eyes

• Inflammation and infection of the mucus-membrane
  lining of the eyelids and eyeballs can be caused
  by irritation from chemical pollutants
• Acids and bases are corrosive and can penetrate
  to the interior of the eye very quickly i.e. lime
  in wall plaster
• Methyl or wood alcohol can cause total blindness
  from damage to the optic nerve

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Skin

• Made up of three layers, the epidermis, the
  dermis and subcutaneous tissue
• The dermis, or live skin, contains blood vessels,
  nerves, nerve receptors, hair follicles and sweat
  and oil glands
• The skin protects against the invasion of
  bacteria, the suns rays and the loss of moisture

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• It senses pressure, pain and temperature and
  regulates the bodys 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

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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

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• During the 1970s 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

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• 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

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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

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Teratogenicity

• A substances tendency to interfere with the
  development of an unborn child
• A teratogen causes birth defects

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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

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• 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

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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

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Risk Management

• Government policy is determined by the publics
  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

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Risk/Benefit Analysis

• Used by regulatory agencies in the decision
  making process
• Subjective concerns such as politics, lifestyles,
  freedoms, economics and progress are considered

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Perception of Risk

• We tend to perceive voluntary risks as less
  perilous than those we are forced to take i.e.
  smoking

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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

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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

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Risk Assessment II

• Risk assessments are required by regulatory
  agencies when contaminants have been released
  into the environment
• Aids in determining acceptable cleanup levels