Chapter 14 Environmetal Health And Toxicology Flashcards
1
Q
What is toxicology?
A
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.
2
Q
What is a toxicant?
A
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.
3
Q
Complete the phrase: ‘The dose makes the _______’
A
poison
4
Q
What does environmental toxicology focus on?
A
Toxic substances that come from or are discharged into the environment.
Toxicologists generally focus on human health, using other organisms as models.
5
Q
What are the leading indoor hazards that contribute to lung cancer?
A
Cigarette smoke and radon.
These are the top two causes of lung cancer in developed nations.
6
Q
What is radon?
A
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.
7
Q
What health issues can result from long-term exposure to asbestos?
A
Scarring of lung tissue, impaired lung function, and asbestosis.
Asbestos is dangerous when inhaled.
8
Q
What are the effects of lead poisoning?
A
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.
9
Q
What are PBDEs?
A
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.
10
Q
What concerns are associated with PBDEs?
A
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.
11
Q
True or False: The European Union banned PBDEs in 2003.
A
True
12
Q
What has been the trend of PBDE concentrations in the United States compared to Europe?
A
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.
13
Q
FAQ
A
14
Q
Do individual organisms
A
15
Q
survive exposure to a toxic
A
16
Q
chemical because they are
A
17
Q
“mutated” by the chemical
A
18
Q
and develop defenses to the
A
19
Q
toxicant?
A
20
Q
When a population of organisms
A
21
Q
is exposed to a toxicant
A
such as
22
Q
a pesticide
A
a few individuals often
23
Q
survive while the vast majority
A
24
Q
of the population is killed. These
A
25
individuals survive because they
26
already possess genes (which
27
others in the population do
28
not) that code for enzymes that
29
counteract the toxic properties of
30
the toxicant. Because the effects
31
of these genes are expressed only
32
when the pesticide is applied
33
many people think the toxicant
34
"creates" detoxification genes by
35
mutating the DNA of a small num-
36
ber of individuals. This is not the
37
case. The genes for detoxifying
38
enzymes were present in the DNA
39
of resistant individuals from birth
40
but their effects were seen only
41
when pesticide exposure caused
42
selective pressure (p. 50) for
43
resistance to the toxic substance.
44
Sensitivity also can vary with sex
age
45
of their smaller size and rapidly developing organ systems
46
younger organisms (for example
fetuses
47
children tend to be much more
48
sensitive to toxicants than are
49
adults. Regulatory agencies such
50
as the U.S. Environmental Pro-
51
tection Agency (EPA) typically
52
set human chemical exposure
53
standards for adults and extrapo-
54
late downward for infants and
55
children. However
many sci-
56
entists contend that these linear
57
extrapolations often do not offer
58
adequate protection to fetuses
59
infants
and children.
60
The type of
61
exposure can
62
affect the
63
response
64
The risk posed by a hazard often
65
varies according to whether a per-
66
son experiences high exposure for
67
short periods of time
known as
68
acute exposure
or low exposure
69
over long periods of time
known
70
as chronic exposure. Incidences
71
of acute exposure are easier to
72
recognize
because they often
73
stem from discrete events
such as
74
accidental ingestion
an oil spill
75
chemical spill
or a nuclear acci-
76
dent. Toxicity tests in laboratories
77
generally reflect acute toxicity
78
effects. However
chronic expo-
79
sure is more common-and more difficult to detect and diag-
80
nose. Chronic exposure often affects organs gradually
as when
81
smoking causes lung cancer or when alcohol abuse leads to
82
liver or kidney damage. Arsenic in drinking water or pesticide
83
residues on food also pose chronic risk. Because of the long
84
time periods involved
relationships between cause and effect
85
may not be readily apparent.
86
species
however
87
abundant. Cascading impacts can cause changes in the composi:.
88
bunof the biological community (p. 53g) and threaten ecosystem.
89
functioning. There are many ways toxicants can concentrate and
90
persist in ecosystems and affect ecosystem services.
91
Airborne substances can travel widely
92
Toxic substances are released around the world from agricul.
93
tural
industrial
94
be redistributed by air currents (Chapter 17)
exerting impacts
95
on ecosystems far from their site of release.
96
Because so many substances are carried by the wind
97
synthetic chemicals are ubiquitous worldwide
even in seem.
98
ingly pristine areas. Scientists who travel to the most remote
99
alpine lakes in the wilderness of British Columbia find them
100
contaminated with industrial toxicants
such as polychlorinated
101
biphenyls (PCBs)
which are by-products of chemicals used in
102
transformers and other electrical equipment and as hydraulic
103
fluids. These chemicals enter the air
soil
104
equipment in which they are housed burns
leaks
105
Earth's polar regions are particularly contaminated
because
106
natural patterns of global atmospheric circulation (p. 451) tend
107
to move airborne chemicals toward the poles (FIGURE 14.12).
108
Thus
although we manufacture and apply synthetic substances
109
At high latitudes
110
deposition of pollutants
111
exceeds evaporation
112
2 Pollutants are
113
transported by
114
atmosphere and
115
ocean currents
116
Atmospheric currents
117
Evaporation
118
Pollutants enter
119
the polar food
120
web and
121
accumulate in
122
biota
123
Deposition
124
— North Pole
125
Evaporation
126
Deposition
127
At low
128
latitudes
129
evapora-
130
tion of
131
pollutants
132
exceeds
133
deposition
134
Oceanic currents
135
Toxic Substances and Their
136
Effects on Ecosystems
137
When toxicants concentrate in environments and harm the health
138
of many individuals
populations (p. 48) of the affected spe-
139
cies become smaller. This decline in population can then affect
140
other species. For instance
species that are prey of the organ-
141
ism affected by toxicants could experience population growth
142
because predation levels are lower. Predators of the poisoned
143
Equator
144
FIGURE 14.12 Air and water currents direct pollutants to the
145
poles
In the process of "global distillation
146
What are the main categories of products that can introduce toxicants into the environment?
Consumer products, Workplace products, Medicines and materials
## Footnote
These categories highlight the various sources of potential environmental toxins.
147
What are the primary environmental mediums through which toxicants travel?
Soil, Water (surface and groundwater), Air
## Footnote
These mediums are critical for understanding the distribution of toxic substances.
148
Which groups are particularly sensitive to toxicants?
Developing fetuses, Babies
## Footnote
These groups are more vulnerable to the effects of toxic substances due to their developmental stages.
149
What is pesticide drift?
The process by which pesticides are carried by air currents to sites far from agricultural fields
## Footnote
This phenomenon can have ecological impacts far from the source of pesticide application.
150
What environmental effect is associated with pesticide drift in the Sierra Nevada?
Population declines in four species of frogs
## Footnote
This illustrates the ecological consequences of pesticide use and drift.
151
How do toxic substances concentrate in water?
Water running off from land transports toxicants and concentrates them in small volumes of surface water
## Footnote
This process highlights the importance of runoff in water quality issues.
152
What role do wastewater treatment plants play in water contamination?
They add toxins, pharmaceuticals, and detoxification products from humans to waterways
## Footnote
This contributes to the overall toxic load in aquatic systems.
153
What happens to chemicals that persist in soil?
They can leach into groundwater and contaminate drinking water supplies
## Footnote
This emphasizes the long-term impacts of soil contamination on water quality.
154
True or False: Contaminants are evenly distributed in the environment.
False
## Footnote
Toxic substances are not evenly distributed and may concentrate in specific areas.
155
What is a significant concern regarding the concentration of contaminants in polar regions?
Contaminants are strikingly concentrated in the tissues of Arctic polar bears, Antarctic penguins, and people living in Greenland
## Footnote
This raises concerns about bioaccumulation and its effects on wildlife and human health.
156
Fill in the blank: Humans receive small amounts of toxicants from many sources, including _______.
[Consumer products, Workplace exposure, Medical facilities, Drinking water, Air for breathing]
## Footnote
These sources contribute to the overall exposure of humans to toxic substances.
157
What type of animals are effective indicators of pollution?
Aquatic animals such as fish, frogs, and stream invertebrates
## Footnote
These animals are sensitive to low concentrations of pollutants and reflect water quality.
158
What factors influence the degradation rate of toxic substances in the environment?
Chemistry, temperature, moisture, and sun exposure
## Footnote
The degradation rate varies based on these environmental conditions.
159
What is the persistence time of Bt toxin compared to DDT and PCBs?
Bt toxin has a very short persistence time, whereas DDT and PCBs persist for decades
## Footnote
Bt toxin is used in biocontrol and genetically modified crops.
160
What is bioaccumulation?
The process where toxic substances accumulate in an organism's body
## Footnote
This occurs when substances are absorbed and stored in tissues.
161
Fill in the blank: Toxic substances that bioaccumulate may be transferred to other organisms through _______.
biomagnification
162
What happens to the concentration of toxicants as they move up the food chain?
Concentrations become magnified
## Footnote
Each predator accumulates toxicants from multiple prey, increasing concentration.
163
What was the effect of DDT on North American birds of prey from the 1950s to the 1970s?
Populations declined precipitously
## Footnote
DDT caused eggshells to grow thinner, leading to embryo death.
164
What are breakdown products?
Simpler compounds into which most toxicants degrade
## Footnote
These may be less harmful or just as toxic as the original substance.
165
True or False: Atrazine has a consistent persistence time regardless of environmental conditions.
False
## Footnote
Atrazine's persistence is highly variable based on environmental factors.
166
What is the relationship between fat-soluble substances and their storage in organisms?
They are absorbed and stored in fatty tissues
## Footnote
This includes organic compounds like DDT and DDE.
167
What notable environmental success occurred after the ban of DDT in the United States?
Populations of birds of prey rebounded
## Footnote
Species like the peregrine falcon and bald eagle saw recovery after DDT was banned.
168
What is the primary reason synthetic chemicals are designed to persist in the environment?
To resist breakdown
## Footnote
This characteristic is beneficial for materials like plastics.
169
What is the impact of toxic substances entering the water supply?
They can affect human health and ecosystems
## Footnote
Contaminants enter drinking water and air, posing risks to all living organisms.
170
Fill in the blank: DDT breaks down into ________, which is a highly persistent and toxic compound.
DDE
171
What is the process of toxic substances accumulating in an individual's tissues called?
Bioaccumulation
172
What happens during biomagnification in a food web?
Toxicants are passed up the food chain, increasing in concentration
## Footnote
Each predator accumulates toxins from multiple prey.
173
Unfortunately
DDT continues to impair wildlife in parts
174
of the world where it is still used. In addition
mercury bioac-
175
cumulates in some commercially important fish species
such
176
as tuna. Polar bears of Svalbard Island in Arctic Norway show
177
extremely high levels of PCB contamination from biomag-
178
nification as a result of the global distillation process shown
179
in Figure 14.12. Polar bear cubs suffer immune suppression
180
hormone disruption
and high mortality- and because the
181
cubs receive PCBs in their mothers' milk
contamination per-
182
sists and accumulates across generations.
183
In all these cases
biomagnification affects ecosystem
184
composition and functioning. When populations of top preda-
185
tors such as eagles or polar bears are reduced
species interac-
186
tions (PP. 74-78) change
and effects cascade through food
187
webs (p. 80).
188
Toxic substances can threaten
189
ecosystem services
190
Toxicants can alter the biological composition of ecosystems
191
and the manner in which organisms interact with one another
192
and their environment. In so doing
harmful compounds can
193
threaten the ecosystem services (pp. 4
116) provided by nature.
194
For example
pesticide exposure has been implicated as a fac-
195
tor in the recent declines in honeybee populations (pp. 245-
196
246)
affecting the ecosystem service of pollination they
197
provide to wild plants and agricultural crops.
198
Nutrient cycling is one of the many services that healthy
199
functioning ecosystems provide. Decomposers and detri-
200
tivores in the soil (p. 78) break down organic matter and
201
replenish soils with nutrients for plants to use. When soils are
202
exposed to pesticides or antifungal agents
nutrient cycling
203
rates are altered. This can make nutrients less available to
204
producers
affecting their growth and causing impacts that
205
cascade throughout the ecosystem.
206
Studying Effects of Hazards
207
Determining health effects of particular environmental haz-
208
ards is a challenging job
especially because any given person
209
or organism has a complex history of exposure to many haz-
210
ards throughout life. Scientists rely on several different meth-
211
ods with people and with wildlife
ranging from correlative
212
surveys to manipulative experiments (p. 13).
213
Wildlife studies integrate work
214
in the field and lab
215
Scientists study the impacts of environmental hazards on
216
wild animals to help conserve animal populations and also to
217
understand potential risks to people. Just as placing canaries
218
in coal mines helped miners determine whether the air was
219
safe for them to breathe
studying how wild animals respond
220
to pollution and other hazards can help us detect environmen-
221
tal health threats before they do us too much harm.
222
Often wildlife toxicologists work in the field with ani-
223
mals to take measurements
document patterns
224
hypotheses
before heading to the laboratory to run con-
225
trolled manipulative experiments to test their hypotheses.
226
The work of two of the pioneers in the study of endocrine
227
disruptors illustrates the approaches embraced in wildlife
228
Biologist Louis Guillette studied alligators in Florida
229
(FIGURE 14.15a) and discovered that many showed bizarre
230
reproductive problems. Females had trouble producing viable
231
eggs
young alligators had abnormal gonads
232
lings had too little of the male sex hormone testosterone while
233
female hatchlings had too much of the female sex hormone
234
(a) Louis Guillette taking blood sample from alligator
235
(b) Tyrone Hayes in lab with frog
236
FIGURE 14.15 Wildlife studies examine the effects of toxic substances in the environment. Researchers
237
Louis Guillette (a) and Tyrone Hayes (b) found that alligators and frogs
respectively
238
maities that they attribute to endocrine disruption by pesticides.
239
CHAPTER 14 Environmental Health and Toxicology
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