Chapter 14 Environmetal Health And Toxicology Flashcards
What is toxicology?
The study of chemical hazards and the effects of poisonous substances on humans and other organisms.
Toxicologists assess and compare substances to determine their toxicity.
What is a toxicant?
A toxic substance, or poison, that can inflict harm if ingested or exposed to in sufficient quantities.
Any chemical substance may exert negative impacts if the quantity is large enough.
Complete the phrase: ‘The dose makes the _______’
poison
What does environmental toxicology focus on?
Toxic substances that come from or are discharged into the environment.
Toxicologists generally focus on human health, using other organisms as models.
What are the leading indoor hazards that contribute to lung cancer?
Cigarette smoke and radon.
These are the top two causes of lung cancer in developed nations.
What is radon?
A highly toxic radioactive gas that is colorless and undetectable without specialized kits.
Radon seeps up from the ground in certain areas and can accumulate indoors.
What health issues can result from long-term exposure to asbestos?
Scarring of lung tissue, impaired lung function, and asbestosis.
Asbestos is dangerous when inhaled.
What are the effects of lead poisoning?
Damage to the brain, liver, kidney, and stomach; learning problems; anemia; hearing loss; and even death.
Lead poisoning among U.S. children has greatly declined due to educational campaigns.
What are PBDEs?
Polybrominated diphenyl ethers, chemicals used as fire retardants in various consumer products.
PBDEs persist and accumulate in living tissue and have been linked to health issues.
What concerns are associated with PBDEs?
They act as hormone disruptors and may affect thyroid hormones, brain development, and potentially cause cancer.
Studies have shown increasing concentrations of PBDEs in breast milk.
True or False: The European Union banned PBDEs in 2003.
True
What has been the trend of PBDE concentrations in the United States compared to Europe?
Rising concentrations in the U.S. with little movement to address the issue, unlike Europe where concentrations have fallen substantially.
The dangers posed by PBDEs have raised questions about flammability standards.
FAQ
Do individual organisms
survive exposure to a toxic
chemical because they are
“mutated” by the chemical
and develop defenses to the
toxicant?
When a population of organisms
is exposed to a toxicant
such as
a pesticide
a few individuals often
survive while the vast majority
of the population is killed. These
individuals survive because they
already possess genes (which
others in the population do
not) that code for enzymes that
counteract the toxic properties of
the toxicant. Because the effects
of these genes are expressed only
when the pesticide is applied
many people think the toxicant
“creates” detoxification genes by
mutating the DNA of a small num-
ber of individuals. This is not the
case. The genes for detoxifying
enzymes were present in the DNA
of resistant individuals from birth
but their effects were seen only
when pesticide exposure caused
selective pressure (p. 50) for
resistance to the toxic substance.
Sensitivity also can vary with sex
age
of their smaller size and rapidly developing organ systems
younger organisms (for example
fetuses
children tend to be much more
sensitive to toxicants than are
adults. Regulatory agencies such
as the U.S. Environmental Pro-
tection Agency (EPA) typically
set human chemical exposure
standards for adults and extrapo-
late downward for infants and
children. However
many sci-
entists contend that these linear
extrapolations often do not offer
adequate protection to fetuses
infants
and children.
The type of
exposure can
affect the
response
The risk posed by a hazard often
varies according to whether a per-
son experiences high exposure for
short periods of time
known as
acute exposure
or low exposure
over long periods of time
known
as chronic exposure. Incidences
of acute exposure are easier to
recognize
because they often
stem from discrete events
such as
accidental ingestion
an oil spill
chemical spill
or a nuclear acci-
dent. Toxicity tests in laboratories
generally reflect acute toxicity
effects. However
chronic expo-
sure is more common-and more difficult to detect and diag-
nose. Chronic exposure often affects organs gradually
as when
smoking causes lung cancer or when alcohol abuse leads to
liver or kidney damage. Arsenic in drinking water or pesticide
residues on food also pose chronic risk. Because of the long
time periods involved
relationships between cause and effect
may not be readily apparent.
species
however
abundant. Cascading impacts can cause changes in the composi:.
bunof the biological community (p. 53g) and threaten ecosystem.
functioning. There are many ways toxicants can concentrate and
persist in ecosystems and affect ecosystem services.
Airborne substances can travel widely
Toxic substances are released around the world from agricul.
tural
industrial
be redistributed by air currents (Chapter 17)
exerting impacts
on ecosystems far from their site of release.
Because so many substances are carried by the wind