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

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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.

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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

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Dose

Nonlineardose-response

Lineardose-response

No threshold

Eff

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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

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Incinerator

Va

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Large fish

De

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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