Risk and Toxicology

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Risk and Toxicology

• Chapter 18

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Smoking in the US

• Smoking is the number one killer in the US
• Worldwide, infectious disease is the number one
  killer. (This includes TB, HIV, malaria, flu,
  measles, cholera, and yellow fever.)
• One study shows that adolescents who smoke more
  than 1 cigarette have an 85 chance of becoming
  smokers.

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Risk

• Risk is the possibility of suffering from a
  hazard
• A hazard may cause economic loss, environmental
  loss, injury, disease or death
• Risk exposure X harm

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Hazards

• Cultural diet, drugs, drinking, driving,
  criminal assault, unsafe sex, and poverty
• Chemical harmful chemicals in air, water, food
  and soil. Most people carry around 500 synthetic
  chemicals in their bodies, whose effects are
  currently unknown. (buy organic)
• Physical ionizing radiation, fire, earthquakes,
  floods, volcanoes, hurricanes, etc.
• Biological pathogens, pollens, allergens,
  animals that bite or sting, parasites

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Toxicology

• Toxicity measure of how harmful a substance is.
• Dose the amount substance introduced to the
  body
• Vector - agent of disease transmission
• Not all people are affect the same by the same
  dose

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Number of individuals affected
Very Sensitive
Majority of population
Very Sensitive
0
20
40
60
80
Dose (hypothetical units)
Fig. 16.3, p. 398
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Bioaccumulation

• Some substances are fat or oil soluble (usually
  organic compounds) and can be stored in body
  tissues and cells.
• When a substance is ingested in very small doses,
  but is stored in the body, it accumulates to a
  higher dose over time (bioaccumulation)

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Biomagnification

• When a substance that bioaccumulates is passed up
  the food chain, each trophic level receives a
  higher dose of the substance
• This is biomagnification
• Animals at the top of the food chain can be
  exposed to very high doses and hence are usually
  affected the most (birds and fish)

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DDT in fish-eating birds (ospreys) 25 ppm
DDT in large fish (needle fish) 2 ppm
DDT in small fish (minnows) 0.5 ppm
DDT in zooplankton 0.04 ppm
DDT in water 0.000003 ppm, Or 3 ppm
Fig. 16.4, p. 399
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Major Bioaccumulants

• DDT
• PCBs (a class of oily chemicals used in
  electrical transformers)
• Radioactive isotopes (strontium-90)
• Dioxin
• Other organo-chlorides

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Poison

• A poison is a substance that has an LD50 of 50 or
  less.
• LD50 stands for the lethal dose in milligrams of
  a substance that kills 50 percent of the test
  organisms (usually rats and mice) per kilogram of
  body weight.
• So 50 milligrams of poison will kill 50 percent
  of organisms weighing 1 kilogram

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Fig. 16.5, p. 400
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Dose-response curve

• Different substance act at different rates and at
  different concentrations.
• The data of the response tells a lot about the
  toxicity of a substance
• Substances without threshold levels cause harm
  even at small doses

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Nonlinear dose-response
Nonlinear dose-response
Linear dose-response
Linear dose-response
Effect
Effect
Threshold level
No threshold
Threshold
Fig. 16.6, p. 401
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Toxicity for humans

• Supertoxic less than .01 nerve gas, dioxin
• Extremely toxic less than 5 nicotine, heroin,
  atropine, potassium cyanide, parathion
• Very toxic 5-50 morphine, codeine, mercury
  salts
• Toxic 50 500 Lead salts, DDT, carbon
  tetrachloride, caffeine, sulfuric acid
• Moderately toxic 500 5,000
• Slightly toxic 5,000 15,000

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Chemical Hazards

• Toxic chemicals are those that are fatal to 50
  of the test population at given concentrations
• Hazardous chemicals cause harm by
• Being flammable or explosive
• Irritating or damaging skin or lungs -
  acidic/basic
• Interfering with oxygen uptake - asphyxiants
• Inducing allergic reactions

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Neurotoxins

• Can effect behavioral changes, learning
  disabilities, ADD, paralysis and death
• Examples
• PCBs - Polychlorinated biphenol
• Methyl mercury
• Arsenic
• lead

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Mutagens

• Agents (chemicals or other (ionizing radiation))
  that cause mutations in DNA
• Most mutations are harmless, but mutations in
  sperm or egg cells can cause genetic defects like
  Downs syndrome, hemophilia, sickle cell anemia,
  manic depression and thalasseamia
• Mutations in other cells are not inherited, but
  may still cause harm

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Teratogens

• Agents (chemicals, viruses, radiation) that cause
  birth defects while the human embryo is
  developing
• Especially during first trimester
• PCBs, Thalidomide, Steroid hormones, and metals
  (arsenic, cadmium, lead, and mercury)

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Carcinogens

• Agents that promote growth of malignant tumors
• Cigarette smoke is a major agent in the US
• Usually a lag time of 10 40 years from initial
  exposure to development of cancer
• Usually due to chronic exposure

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Synthetic Chemicals

• Many synthetics can harm the brain and spinal
  cord and peripheral nerves
• Neurotoxins attack the nerve cells
• Chlorinated hydrocarbons (DDT, PCBs, dioxin)
• Organophosphate pesticide
• Formaldehyde
• Compounds of arsenic, mercury, lead, cadmium
• Solvents (trichloroethylene (TCE), toluene and
  xylene

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Chemicals released each year

• The US releases more than 1,000 new synthetic
  chemicals into the marketplace each year
• 99.5 of these chemicals are not regulated by the
  federal government
• Only 2 of 85,000 synthetic chemicals are
  adequetly tested
• Chemicals can interact within the body or
  environment to create new chemicals

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The Bodies Defenses

• Immune system - antibodies and cellular defense -
  fights against disease and harmful substances
• Endocrine system - regulate hormones/growth and
  development
• Hormone mimics disrupt the endocrine sys
• Dioxins, PCBs, DDT, lead, other pesticides
  (especially chloronated hydrocarbons)

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Transmissible diseases

• Transmissible diseases are caused by living
  organisms
• These infectious agents are spread by air, water,
  food, bodily fluid, insects and other vectors
• 80 of illness in developing countries is from
  waterborne infectious diseases (diarrhea,
  hepatitis, typhoid fever, cholera) mainly from
  unsafe drinking water and inadequate sanitation

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7 Deadly Diseases

• According to WHO the seven deadliest infectious
  diseases are
• Acute respiratory infection (pneumonia, flu)
• HIV/ AIDS
• Diarrheal diseases
• TB tuberculosis
• Malaria
• Measles
• Hepatitis B

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Virus vs. Bacteria

• Viral disease
• AIDS
• Ebola
• Influenza
• Rabies
• Avian or bird flu
• West Nile virus
• SARS
• Hepatitus B

• Bacterial disease
• Tuberculosis (TB)
• Lyme disease
• Pneumonia

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Tuberculosis

• A highly infectious bacterial disease
• It is estimated that between 2006 and 2020 25
  million people will die of tuberculosis, most of
  which live in developing countries
• Half of the people infected with TB do not know
  they have it and can infect another 10-15 people
  on average

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Tuberculosis

• Population growth, urbanization, and air travel
  have increased contact with TB
• Luckily four inexpensive drugs in combination can
  cure 90 of cases, but the drugs must be taken
  every day for 6-8 months
• Because symptoms disappear after a few weeks,
  many patients stop taking the medication

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Tuberculosis

• The incidence of TB has increased due to
• Increased size in population
• Increased number of elderly in the population
• Poverty
• World travel
• TB bacterium have developed resistance to
  antiobiotics
• Weakened immune systems (from AIDS and other
  diseases)

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Malaria

• Symptoms come and go and include fever, anemia,
  enlarged spleen, severe abdominal pain,
  headaches, extreme weakness to other diseases
• Kills about 1.5 million each year, most under 5
• Caused by parasitic protozoa (Plasmodium) passed
  on typically by Anopheles mosquitoes

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Reduction in Malaria

• Incidences of malaria were temporarily decreased
  during the mid 1900s
• Draining wetlands/swamps
• Spraying DDT to kill mosquitos
• Use of drugs to kill parasite in patients
• Increased awareness of symptoms for early
  treatment
• Unfortunately, since 1970 malaria has risen due
  to genetic resistance and deforestation

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West Nile Virus

• Transferred to humans by mosquitos
• It arrived in the US in 1999 (estimated)
• Since then has spread coast to coast and infected
  more than 1.2 million people

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SARS

• Severe acute respiratory syndrome
• First appeared in 2002 in China
• Flu-like symptoms that can quickly turn to
  pneumonia (and death)
• Spread quickly in 2003, but was contained by WHO
  and other local agencies

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Lyme Disease

• Spread by deer ticks
• Bacteria that attacks the nervous system
• The bite from the tick leaves a red bulls-eye
  target on the skin
• With immediate antiobiotics the effects are
  minimal

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Poverty

• This is the greatest risk humans face
• Other than poverty, most people face the greatest
  risk from their lifestyle choices
• Avoid risk no smoking, avoid excess sun, low to
  zero alcohol consumption, reduce cholesterol and
  saturated fats, eat a variety of fruits and
  vegetables, exercise, lose excess weight, and use
  safety equipment (seatbelts, helmets, life
  jackets, etc)

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The End

• Stay healthy
• Live long
• Enjoy life!
• ?