Download z0117HumanHealth HazardsShort

Environmental Hazards and
Human Health
© Cengage Learning 2015
Types of hazards—
Biological hazards—pathogens, pollen & allergens, animals
Chemical hazards—harmful chemicals in the air, water, soil,
and food
Physical (Natural) hazards—ionizing radiation (gamma,
X-ray, UV), fire, earthquake, flood, tornadoes, etc.
Cultural hazards—unsafe working conditions, smoking, poor
diet, unsafe sex, driving, poverty, etc.
© Cengage Learning 2015
There are three primary ways that a
hazard can enter the body:
Ingestion- substance enters through mouth/ is eaten.
Substance enters digestive tract then the substance is either
(a) absorbed into the bloodstream or (b) not absorbed so
passes through digestive track and is excreted in the feces.
Inhalation- substance is breathed into the lungs. The inside
surface of the lungs is very large and is a poor chemical
barrier. Therefore, many chemicals can easily and quickly
enter the bloodstream.
Skin absorption - substance moves through skin. The skin is
a good barrier and provides protection, but some
substances can penetrate the skin and enter bloodstream.
© Cengage Learning 2015
Toxicity—measure of how harmful a substance is
• Potential harm is dependent on
o Dose- the specific amount of a chemical that enters the
body…… “The dose makes the poison”
o Bioaccumulation—some molecules are absorbed & stored
in specific organs or tissues at levels higher than normally
would be expected
o Biomagnification—levels of some toxins in the environment
are magnified as they pass through a food chain
DDT, PCBs, Heavy metals (Pb, Hg, As, Cd), some radioactive
isotopes
o Chemical interactions that can decrease or multiply the
effects of a toxin
-Decrease effect: Vitamins A & E interact to reduce body’s
response to carcinogens
-Increase effect: Asbestos workers who smoke increase
chances of lung cancer 400x
© Cengage Learning 2015
• Poison/toxin—chemical that has an LD50 of 50 mg or less per kg of
body weight
LD50—median lethal dose- The amount of chemical that in
one dose that kills exactly 50% of the animals in a test
population within a 14 day period
-Acute effect- sudden and severe reaction
-Chronic effect – long-lasting or permanent reaction
© Cengage Learning 2015
• Poison/toxin—chemical that has an LD50 of 50 mg or less per kg of
body weight
LD50—median lethal dose- The amount of chemical that in
one dose that kills exactly 50% of the animals in a test
population within a 14 day period
Dose-response curves—shows the effects of various dosages of
a toxin on a group of test organisms
Which of these two different
toxins is the most toxic?
LD50 = 2 mg/kg
or
LD50 = 200 mg/kg
© Cengage Learning 2015
• Poison/toxin—chemical that has an LD50 of 50 mg or less per kg of
body weight
-Acute effect- sudden and severe reaction
-Chronic effect – long-lasting or permanent reaction
© Cengage Learning 2015
• Toxicity Testing
Laboratory investigations- usually involves test animals
Case reports- studying people’s adverse health effects/or death
after exposure to toxin
Study populations of humans exposed to certain chemical or
diseases
© Cengage Learning 2015
Chemical Hazards
Toxic chemicals—substances that are fatal to more than 50% of test
animals (LD50) at given concentrations
o Arsenic, Lead, Mercury, Vinyl chloride, PCB’s, Benzene,
Cadmium, DDT (#13)
o The Dirty Dozen – POP –
Hazardous chemicals — cause harm by being flammable, irritating or
damaging to skin or lungs, inducing allergic reactions, or toxic.
o Acids, bases, ammonia, diesel exhaust, hydrogen sulfide(H2S)
Carcinogens — chemicals, ionizing radiation, or viruses (HIV, HPV) that may
cause cancer. Cancer is caused by mutations to DNA.
o Arsenic, Asbestos, Benzene, BPA, PCB’s, Vinyl chloride,
Tobacco smoke. {All carcinogens are also mutagens}
Mutagens — chemical or radiation that increase the frequency of
mutations to DNA molecules; many mutations cause cancer
o Ionizing radiation, Nitrous acid(Nitrite preservatives), lead
© Cengage Learning 2015
Chemical Hazards
Teratogens — chemicals, ionizing radiation, or viruses that may cause
birth defects in a human embryo or fetus.
o Pb, Hg, PCB’s, alcohol, tobacco smoke
Neurotoxins — chemicals that cause harm to the human nervous
system (brain, nerves, spinal cord)
o Chlorinated hydrocarbons (DDT, PCB’s, dioxins)
o Heavy metals (arsenic, mercury, lead, cadmium)
o Industrial solvents (methanol, toluene, xylene)
Hormonally active agents(HAAs) or Endocrine disruptors - have shape
similar to hormones so able to attach to receptors
Estrogen mimics
o Pesticides, Chlorinated hydrocarbons (DDT, PCB’s, dioxins),
bisphenol-A(BPA), mercury
© Cengage Learning 2015
Biological Hazards
• Nontransmissible diseases—not caused by living things & do not
spread from person to person
o Cardiovascular diseases, cancers, diabetes, asthma, etc
• Transmissible diseases—caused by living things and can be spread
from person to person
o Pathogens are spread via air, water, food, body fluids, or
insects vectors
o Vectors - an animal (mosquito, ticks, fleas, flies) that carries
a disease and can transmit the disease by biting
© Cengage Learning 2015
Vector - an animal that carries a
disease (but doesn’t “catch” it)
and can transmit the disease by
biting another animal;
mosquito, ticks, fleas, flies.
Host - the animal that contracts
the disease; The host provides
shelter and nutrition.
Pathogen - the disease-causing
organism; virus, bacteria,
protozoan, fungi
Vector-borne diseases are infections transmitted by the bite of
infected arthropod species, such as mosquitoes, ticks, fleas,
sandflies, and blackflies.
© Cengage Learning 2015
Vector-borne diseases are infections transmitted by the bite of infected arthropod species, such as
mosquitoes, ticks, sandflies, and blackflies. Arthropod vectors are cold-blooded (ectothermic) and thus
especially sensitive to climatic factors. Weather influences survival and reproduction rates of vectors, in
turn influencing habitat suitability, distribution and abundance; intensity vector activity (particularly
biting rates) throughout the year; and rates of development, survival and reproduction of pathogens
within vectors. However, climate is only one of many factors influencing vector distribution, such as
© Cengage Learning 2015
habitat
destruction, land use, pesticide application, and host density.
Biological Hazards
• Nontransmissible diseases—not caused by living things & do not
spread from person to person
o Cardiovascular diseases, cancers, diabetes, asthma, etc
• Transmissible diseases—caused by living things and can be spread
from person to person
o Pathogens are spread via air, water, food, body fluids, or
insects vectors
o Vectors - an animal (mosquito, ticks, fleas, flies) that carries
a disease and can transmit the disease by biting
o Epidemic – a large-scale outbreak of an infectious disease
o Pandemic – a global epidemic such as AIDS, & Spanish Infuenza
© Cengage Learning 2015
• WHO’s seven deadliest infectious diseases
o Acute respiratory infections (Pneumonia & Flu)—3.7 million/yr
o HIV/AIDS—2.6 million/yr
o Diarrheal diseases—2.5 million/yr
o Tuberculosis—2 million/yr
o Malaria—1.5 million/yr
o Measles—1 million/yr
o Hepatitis B—1 million/yr
© Cengage Learning 2015
Influenza (Flu)
Flu is a highly contagious respiratory illness caused by influenza viruses.
Colds and flu are caused by viruses. There are over 100 different viruses that cause the cold, but
only influenza virus types A, B, and C cause the flu. Type A and B viruses cause the large seasonal
outbreaks; the flu vaccine can help protect you from types A and B. Type C usually causes milder
respiratory symptoms; there is no immunization for type C virus.
The flu can cause mild to severe illness. Serious outcomes can result in hospitalization or death. Some
people, such as older people, young children, and people with certain health conditions, are at high
risk for serious flu complications.
Flu viruses are spread mainly by respiratory droplets made when people with flu cough, sneeze or talk.
These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into
the lungs. Less often, a person might also get flu by touching a surface or object that has flu virus on it
and then touching their own mouth or nose.
Sinus and ear infections are examples of moderate complications from flu, while pneumonia is a
serious flu complication that can result from either influenza virus infection alone or from co-infection
of flu virus and bacteria. Other possible serious complications triggered by flu can include inflammation
of the heart (myocarditis), brain (encephalitis) or muscle (myositis, rhabdomyolysis) tissues, and multiorgan failure (for example, respiratory and kidney failure). Flu virus infection of the respiratory tract
can trigger an extreme inflammatory response in the body and can lead to sepsis, the body’s lifethreatening response to infection. Flu also can make chronic medical problems worse. For example,
people with asthma may experience asthma attacks while they have the flu, and people with chronic
heart disease may experience a worsening of this condition triggered by flu.
The best way to prevent the flu is by getting vaccinated each year
© Cengage Learning 2015
Other infectious diseases
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Cholera
SARS
Lyme disease
West Nile virus
Zika
Avian Flu
Ebola virus
Yellow fever
© Cengage Learning 2015
Lyme disease
Lyme disease is caused by the bacterium Borrelia burgdorferi and
is transmitted to humans through the bite of infected blacklegged ticks (deer
tick). The tick’s host are primarily mice and deer. Ticks can attach to any part of
the human body but are often found in hard-to-see areas such as the groin,
armpits, and scalp. The tick must be attached for 36 to 48 hours or more before
the Lyme disease bacterium can be transmitted. Most humans are infected
through the bites of immature ticks called nymphs. Nymphs are tiny (less than 2
mm) and difficult to see; they feed during the spring and summer months. In
general, adult ticks are approximately the size of a sesame seed and nymphal
ticks are approximately the size of a poppy seed. Ticks can't fly or jump.
Instead, they wait for a host, resting on the tips of grasses and shrubs, when
host brushes the spot where a tick is waiting, it quickly climbs aboard.
Typical symptoms include fever, headache, fatigue, and skin rash. If left
untreated, infection can spread to joints, the heart, and the nervous system.
Lyme disease can be treated successfully with a few weeks of antibiotics. Steps
to prevent Lyme disease include using insect repellent, removing ticks
promptly, applying pesticides, and reducing tick habitat.
© Cengage Learning 2015
Treatments for infectious diseases
o Bacterial & protozoan diseases are treated with antibiotic
drugs
o Viral disorders are treated with vaccines before infection
© Cengage Learning 2015
Factors affecting the spread of transmissible diseases
o Immigration from country to country
o Increased international air travel
o Urbanization - Migration to urban areas
o Migration to uninhabited rural areas
o Deforestation of tropical areas in developing nations
o Global warming
o Accidental introduction of insect vectors(exports/imports)
o Flooding
o Hunger & malnutrition
o Increased rice cultivation (mosquito breeding)
© Cengage Learning 2015
Factors that contribute to the emergence of new diseases
or the re-emergence of old diseases
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Increased population density in humans
Genetic resistance to antibiotics
Genetic resistance to pesticides
Humans living closer to forested areas so increase likelihood
of contact with infected animal
o Destruction of habitat leads to decrease in mosquito
predators
o Global warming
o Lack of pathogen-free drinking water
© Cengage Learning 2015
Risk—probability of suffering harm from a hazard that can cause
injury, disease, economic loss, or environmental damage
Risk assessment — Identifying hazards & evaluating their associated risk
Risk management — Determining options & making decisions about
reducing or eliminating risk
• Greatest risks in terms of reduced life span is poverty followed by
personal choices
• Reducing risk
o Not smoking, Not drink alcohol, Eat healthy, Exercise
regularly, Lose excess weight, Avoid excess sunlight
© Cengage Learning 2015
Chemical Hazards
Teratogens — chemicals, ionizing radiation, or viruses that may cause
birth defects in a human embryo or fetus.
o Pb, Hg, PCB’s, alcohol, tobacco smoke
Neurotoxins — chemicals that cause harm to the human nervous
system (brain, nerves, spinal cord)
o Chlorinated hydrocarbons (DDT, PCB’s, dioxins)
o Heavy metals (arsenic, mercury, lead, cadmium)
o Industrial solvents (methanol, toluene, xylene)
Hormonally active agents(HAAs) or Endocrine disruptors - have shape
similar to hormones so able to attach to receptors
Estrogen mimics
o Pesticides, Chlorinated hydrocarbons (DDT, PCB’s, dioxins),
bisphenol-A(BPA), mercury
© Cengage Learning 2015
BPA – bisphenol A
https://www.youtube.com/watch?v=8mXosTkwtYs
© Cengage Learning 2015
DDT
PCB
(polychlorinated biphenyls)
Dioxins
© Cengage Learning 2015
How many times more are people likely to die from
cancer than ischaemic heart disease?
© Cengage Learning 2015
The World’s 10 Leading Causes of Death
1. Ischaemic heart disease
Global deaths: 7 million
aka coronary heart disease
2: Stroke
Global deaths: 6.2 million
When the blood supply to part of the brain is cut off
3: Lower respiratory infection
Global deaths: 3.2 million
Include flu, pneumonia and tuberculosis (TB).
© Cengage Learning 2015
4: Chronic obstructive pulmonary disease
Global deaths: 3 million
Chronic obstructive pulmonary disease, or COPD, diseases of the
aka: asthma, emphysema and bronchitis.
5: Diarrhoeal diseases
Global deaths: 1.9 million
The second largest killers of children under five globally, with
Mostly caused by poor sanitation and contaminated drinking water.
6: HIV/AIDS
Global deaths: 1.6 million
– conditions that cause progressive failure of the immune system
© Cengage Learning 2015
7: Respiratory cancers
Global deaths: 1.5 million
aka: Tracheal, bronchial and lung cancers
Lung cancer is the leading cause of cancer death in the U.S.
8: Diabetes mellitus
Global deaths: 1.4 million
There are two kinds of diabetes – type one and type two.
9: Road injury
Global deaths: 1.3 million
91% of road deaths take place in low and middle-income countries.
10: Prematurity
Global deaths: 1.2 million
Low-income countries, babies born prematurely are 10 times more
likely to die than babies born in wealthy, high-income countries.
© Cengage Learning 2015