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Risk, Toxicology, and Human HealthRisk, Toxicology, and Human Health
Ch 17Ch 17
Dr. Richard ClementsChattanooga State Technical Community CollegeDr. Richard ClementsChattanooga State Technical Community College
Key ConceptsKey Concepts
Types of hazards people face Types of hazards people face
Methods of toxicology Methods of toxicology
Types and measurement of chemical hazards Types and measurement of chemical hazards
Types and effects of biological hazards Types and effects of biological hazards
Risk estimation, management, and reduction Risk estimation, management, and reduction
Risk and ProbabilityRisk and Probability
Risk - the possibility of suffering harm from exposure to a hazard that can cause injury, disease, economic loss, or environmental damage.
probability: a mathematical statement about how likely it is that some event or effect will occur.
Risk - the possibility of suffering harm from exposure to a hazard that can cause injury, disease, economic loss, or environmental damage.
probability: a mathematical statement about how likely it is that some event or effect will occur.
Risk assessment involves using data, hypotheses, and
models to estimate:
a. What is the hazard?
b. Probability that harm will occurc. How much damage is likely to occur
Risk assessment involves using data, hypotheses, and
models to estimate:
a. What is the hazard?
b. Probability that harm will occurc. How much damage is likely to occur
Risk and ProbabilityRisk and Probability
Risk management - making decisions bya. Comparing with other risksb. Assessing how risk can be
reduced if neededc. Calculating financial commitment
necessary
Risk management - making decisions bya. Comparing with other risksb. Assessing how risk can be
reduced if neededc. Calculating financial commitment
necessary
HazardsHazards
Cultural hazards - such as unsafe working conditions, diet, drugs, drinking, poverty
Cultural hazards - such as unsafe working conditions, diet, drugs, drinking, poverty
Chemical hazards - from harmful chemicals (such as, in the air, water, soil).
Chemical hazards - from harmful chemicals (such as, in the air, water, soil).
Physical hazards - (ex: ionizing radiation, fire, hurricanes).
Physical hazards - (ex: ionizing radiation, fire, hurricanes).
Biological hazards - from pathogens (disease causing organisms such as bacteria, viruses & parasites), allergens (such as pollen, mold), and animals (such as bees, poisonous snakes).
Biological hazards - from pathogens (disease causing organisms such as bacteria, viruses & parasites), allergens (such as pollen, mold), and animals (such as bees, poisonous snakes).
ToxicologyToxicology
Toxicity - measure of how harmful a substance is.
Toxicity - measure of how harmful a substance is.
Dosage - The amount of a potentially harmful substance that a person has ingested, inhaled, or absorbed through the skin
Dosage - The amount of a potentially harmful substance that a person has ingested, inhaled, or absorbed through the skin
© 2004 Brooks/Cole – Thomson Learning
Verysensitive
Majorityof population
Veryinsensitive
0 20 40 60 80
Dose (hypothetical units)
Nu
mb
er o
f in
div
idu
als
affe
cted
ResponseResponseThe resulting type and amount of damage to
health
Depends on:
a. size of the dose over a period of time
b. how often exposure occursc. who is exposed (ex: child, adult)d. How well liver, lungs and kidneys work to
detoxify the substancee. Genetic makeup that determines an
individuals sensitivity
ToxicologyToxicology
Bioaccumulation - an increase in the concentration of a chemical in specific organs or tissues at a level higher than would normally be expected.
Bioaccumulation - an increase in the concentration of a chemical in specific organs or tissues at a level higher than would normally be expected.
BiomagnificationThe levels of some toxins stored in body fat can also be magnified as they pass through food chains and webs. Ex: DDT – pesticide, PCB’s – oily chemicals used in electrical transformers, some radioactive isotopes
BiomagnificationThe levels of some toxins stored in body fat can also be magnified as they pass through food chains and webs. Ex: DDT – pesticide, PCB’s – oily chemicals used in electrical transformers, some radioactive isotopes
Persistence of substance – resistance to breakdown determines how long it will persist in the environment or body. Ex: CFC’s and chlorinated hydrocarbons have a long-lasting affect on people and wildlife.
DDT in fish-eatingbirds (ospreys)
25 ppm
DDT in largefish (needle fish)2 ppm
DDT in smallfish (minnows)0.5 ppm
DDT inzooplankton0.04 ppm
DDT in water0.000003 ppm,Or 3 ppt
ToxicologyToxicologySynergism -Chemical interactions can decrease or multiply harmful effects:Antagonistic interactions – reduce harmful response Ex: vitamins A & E reduce response of some carcinogens.Synergistic interactions – increase harmful response Ex: asbestos exposure and cigarette smoking together increase chances of getting lung cancer above each substance alone.
Synergism -Chemical interactions can decrease or multiply harmful effects:Antagonistic interactions – reduce harmful response Ex: vitamins A & E reduce response of some carcinogens.Synergistic interactions – increase harmful response Ex: asbestos exposure and cigarette smoking together increase chances of getting lung cancer above each substance alone.
Acute effect - immediate harmful reactionAcute effect - immediate harmful reactionChronic effect - permanent or long lasting effect.
Chronic effect - permanent or long lasting effect.
PoisonsPoisons
Poison - chemical that has an LD50 of 50 milligrams or less per kilogram of body weight.
Poison - chemical that has an LD50 of 50 milligrams or less per kilogram of body weight.
LD50 - median lethal dose, or amount of a
chemical received in one dose that kills exactly 50% of the animals in a test population within a 14-day period.
LD50 - median lethal dose, or amount of a
chemical received in one dose that kills exactly 50% of the animals in a test population within a 14-day period.
100
75
50
25
02 4 6 8 10 12 14 16
Per
cen
tag
e o
f p
op
ula
tio
n k
illed
by
a g
iven
do
se
Dose (hypothetical units)
LD50
© 2004 Brooks/Cole – Thomson Learning
How much is too much?How much is too much?Threshold level – below this amount, harmful effects are
insignificant. Why?
1. Human body has ways of breaking down (usually by liver enzymes), diluting or excreting small amts. of most toxins to keep them from reaching harmful levels.
2. Individual cells have enzymes that can repair damage to DNA and proteins.
3.Cells in some parts of the body (ex: skin, intestines) reproduce fast enough to replace damaged cells. But exposure to carcinogens accelerates cell growth and creates tumors.
4.Detection methods have become increasingly more sensitive – in 1980 chemists could detect concentrations in ppm (parts per million), in 1990 in ppb (ppbillion), and today ppt (pptrillion) or sometimes ppq (ppquadrillion).
Dose-Response CurvesDose-Response Curves
Nonthreshold - any dose of a toxic chemical or ionizing radiation has a certain risk of causing harm.
Nonthreshold - any dose of a toxic chemical or ionizing radiation has a certain risk of causing harm.
Threshold there is a threshold dose below which no detectable harmful effects occur, presumably because the body can repair the damage caused by low doses of some substances.
Threshold there is a threshold dose below which no detectable harmful effects occur, presumably because the body can repair the damage caused by low doses of some substances.
© 2004 Brooks/Cole – Thomson LearningE
ffec
t
Dose
Nonlineardose-response
Lineardose-response
No threshold
Eff
ect
Nonlineardose-response
Lineardose-response
Threshold
Thresholdlevel
Dose
Chemical HazardsChemical Hazards
Types of Hazardous chemicalsTypes of Hazardous chemicals
Mutagens - are agents, such as chemicals and radiation, that cause mutations, or changes in the DNA molecules found in the cells. Mutations to gametes can cause diseases such as bipolar disorder, cystic fibrosis, hemophilia, sickle-cell anemia, susceptibility to some types of cancers in offspring. Most mutations are actually harmless and some play a vital role in microevolution.
Mutagens - are agents, such as chemicals and radiation, that cause mutations, or changes in the DNA molecules found in the cells. Mutations to gametes can cause diseases such as bipolar disorder, cystic fibrosis, hemophilia, sickle-cell anemia, susceptibility to some types of cancers in offspring. Most mutations are actually harmless and some play a vital role in microevolution.
Chemical HazardsChemical Hazards
Types of Hazardous chemicalsTypes of Hazardous chemicals
Teratogens - are chemicals, radiation, or viruses that cause birth defects while the human embryo is growing and developing during pregnancy, especially during the first 3 months.
Carcinogens - are chemicals, radiation, or viruses that cause or promote the growth of malignant tumor, in which certain cells multiply uncontrollably.
Teratogens - are chemicals, radiation, or viruses that cause birth defects while the human embryo is growing and developing during pregnancy, especially during the first 3 months.
Carcinogens - are chemicals, radiation, or viruses that cause or promote the growth of malignant tumor, in which certain cells multiply uncontrollably.
Chemical HazardsChemical Hazards
NeurotoxinsEx:
1. chlorinated hydrocarbons (DDT, PCBs, dioxins)
2. organophosphate pesticides3. formaldehyde, compounds of arsenic, mercury, lead, and cadmium4. some widely used industrial solvents such as trichloroethylene (TCE), toluene, and xylene.
NeurotoxinsEx:
1. chlorinated hydrocarbons (DDT, PCBs, dioxins)
2. organophosphate pesticides3. formaldehyde, compounds of arsenic, mercury, lead, and cadmium4. some widely used industrial solvents such as trichloroethylene (TCE), toluene, and xylene.
Case Study: PCBs Are Everywhere—Case Study: PCBs Are Everywhere—• Class of chlorine-containing compounds (Polychlorinated
Biphenyl )– can enter the air as vapor– Were widely used as lubricants, hydraulic fluids, electrical
insulators in transformers, in paints, pesticides, fire retardants in fabrics, preservatives, adhesives.
– Carcinogen, also affects reproductive, nervous, endocrine, immune system.
– Banned in 1979 in the U.S.– Highly persistent, Fat soluble – Biomagnification
• Banned, but found everywhere
Science Focus: Mercury’s Toxic Effects (2)Science Focus: Mercury’s Toxic Effects (2)
How are humans exposed?– Inhalation: vaporized Hg or particulates of
inorganic salts– Eating fish with high levels of methylmercury
Effects of Hg on humans – Neurotoxin that causes brain damage, esp in developing fetuses
Case Study – Minimata Bay, Japan
Fig. 17-A, p. 450
WINDS PRECIPITATION WINDS PRECIPITATION
Hg and SO2 Hg2+ and acids Hg2+ and acids
Photo-chemical oxidation
Human sources Elemental mercury vapor (Hg)
Inorganic mercury and acids
(Hg2+)
Inorganic mercury
and acids (Hg2+)
Coal-burning plant
De
po
sitio
n
Incinerator
Va
po
rizatio
n
Large fish
De
po
sit
ion
De
po
sit
ion
Small fish BIOMAGNIFICATION IN FOOD CHAIN
Zooplankton Phytoplankton
Bacteria and acidsElemental
mercury liquid (Hg)
Oxidation Inorganic mercury
(Hg2+)
Organic mercury (CH3Hg+)Bacteria
Settles out
Settles out
Settles out
SEDIMENT
Runoff of Hg2+ and acids
Fig. 17-B, p. 451
SOLUTIONS
Mercury PollutionPrevention ControlPhase out waste incineration Sharply reduce mercury
emissions from coal-burning plants and incineratorsRemove mercury from
coal before it is burned
Tax each unit of mercury emitted by coal-burning plants and incinerators
Switch from coal to natural gas and renewable energy resources such as wind, solar cells, and hydrogen
Require labels on all products containing mercury
Convert coal to liquid or gaseous fuel
Phase out use of mercury in batteries, TVs, compact fluorescent lightbulbs, and all other products unless they are recycled
Collect and recycle mercury-containing electric switches, relays, and dry-cell batteries
Bisphenol ABisphenol A
• Used in plastic food containers (#7)• Many studies find no effects• Precautionary principle
Chemical HazardsChemical HazardsHormonally active agents (HAA’s) Low levels of synthetic chemical agents that can mimic and disrupt effects of natural hormones. Ex: PCBs, DDT Hormone mimics - are estrogen-like chemicals that disrupt the endocrine system by being able to attach to estrogen receptor molecules. Hormone blockers - disrupt the endocrine system by preventing hormones (such as androgens) from attaching to their receptors.
thyroid disruptors and cause growth,
weight gain, and behavioral disorders.
Hormonally active agents (HAA’s) Low levels of synthetic chemical agents that can mimic and disrupt effects of natural hormones. Ex: PCBs, DDT Hormone mimics - are estrogen-like chemicals that disrupt the endocrine system by being able to attach to estrogen receptor molecules. Hormone blockers - disrupt the endocrine system by preventing hormones (such as androgens) from attaching to their receptors.
thyroid disruptors and cause growth,
weight gain, and behavioral disorders.
Hormone
Receptor
Cell
Normal Hormone Process Hormone Mimic Hormone Blocker
Estrogen-like chemical Antiandrogen chemical
Figure 11-7Page 234Figure 11-7Page 234
What should we do?What should we do?
Precautionary principle1. Emphasizes pollution prevention!2. When we are uncertain about potentially serious harm from something, decision makers should act to prevent harm to humans and the environment. (“better safe than sorry”3. New chemicals and technologies would be assumed guilty until proven innocent those proposing to introduce a new chemical or technology would bear the burden of establishing it’s safety
Precautionary principle1. Emphasizes pollution prevention!2. When we are uncertain about potentially serious harm from something, decision makers should act to prevent harm to humans and the environment. (“better safe than sorry”3. New chemicals and technologies would be assumed guilty until proven innocent those proposing to introduce a new chemical or technology would bear the burden of establishing it’s safety
Biological Hazards: DiseasesBiological Hazards: Diseases
Nontransmissible diseaseNontransmissible diseaseTransmissible diseaseTransmissible diseasePathogensPathogensVectorsVectorsAntibiotic resistanceAntibiotic resistance
See Case Study p. 241See Case Study p. 241
MalariaMalariaAIDSAIDS
Figure 11-12Page 243Figure 11-12Page 243
Malaria-free areas Malaria largely eliminated Malaria transmission areas
Risk AnalysisRisk Analysis
Risk analysisRisk analysis
Comparative riskanalysis
Comparative riskanalysis
Cost-benefitanalysis
Cost-benefitanalysis
Risk managementRisk management
Risk perceptionRisk perception Fig. 11-17p. 247