Chapter 5 - Part I Flashcards
Environmental toxicology deals with the harmful effects of chemicals on ecosystems and their components. What modes of effects does this include?
- delivery
- transport
- transformation
- effects of pollutants
How do pollutants enter ecosystems?
- discharges into the atmosphere
- contamination of land
- entry into water
What are pollutants that originate from a known source that can be tracked such as direct discharge from industrial or agricultural industried, waster storage, waste lagoon etc.?
point source
What are pollutants where the direct source is hard or impossible to track such as pesticides , fertilizers, household wastes, etc.?
non-point source
What factor regulates waste disposal, clean-up standards, transportation, and other aspects of waste discharge, clean-up, and environmental protection?
Environmental law
ex. new Georgia Clean Water Act
How are pollutants destroyed?
biodegradation
Which will degrade more rapidly?
hexane
Which will degrade more rapidly?
benzene
Which will degrade more rapidly?
2, 4-D
How can environmental pollutants relocate from their original source?
interface transport processes
What is the theoretical boundary between air and water, air and soil, and soil and water?
interface
plants and animals located here experience adverse effects
Which boundary is this interface inbetween?
top: atmosphere
bottom: soil
What boundary is this interface in between?
top: soil
bottom: ground water
How are contaminants released into the atomosphere?
photolysis
How are contaminants dispersed throughout the soil?
- chemical transformation
- microbial transformation
- organism uptake
- absorption/deabsorption
How do plants release toxins into the atmosphere?
volatilization
e.g. evaporation
How do plants uptake toxins from the soil?
absorption
What is it?
- chlorinated hydrocarbon that was developed in the 1930s by the chemist Paul Muller
- very effective insecticide and did not easily degrade in the environment
- became popular during WWII and was instrumental in the reduction of such disease vectors as typhoid and malaria
- responsible for saving millions of lives
DDT
dichlorodiphenyltrichloroethane
di-chloro-di-phenyl-tri-chloro-ethane
How was the use of DDT adopted on a global scale?
effectiveness and persistence
also cost effective
The use of DDT during the WWII era was rather prevalent because of its…
cost-effectiveness
What does ubiquity mean?
the state of being everywhere, omnipresence
After the wake of DDT and it’s effects on the environment, what publication launched a modern environmental movement?
Silent Spring, 1962
by Rachel Carson
What effects in laboratory animals were shown to be a result of exposure to DDT?
- reproductive
- teratogenic
- neurological
When was DDT banned in the US?
1972
In the environment, what is DDT partially transformed in to?
DDR
dichlorodiphenyldichloroethylene
di-chloro-di-phenyl-di-chloro-ethylene
Does DDE show negative effects similar to DDT?
yes
What has been the result of DDT and DDE on the environment?
related to its ubiquity
Even after almost 40 years after its ban, DDT and DDE are detected in human milk, in Antarctica and Arctic ice, and in remote deserts where DDT has never been used.
What is this structure?
DDT
What is this structure?
DDE
What is this structure?
DDA
What is this structure?
TDE (DDD)
During DDT metabolism, how is DDT transformed into TDE (DDD)?
-Cl/+H
During DDT metabolism, how is DDT transformed into DDE?
-HCl
During DDT metabolism, how is DDT transformed into DDA?
through a series of transformations
DDT->TDE->DDM(U:S)->DDNU->DDOH->intermediate->DDA
-Cl/+H -> -HCl -> +2H -> -HCl -> +HOH -> +2H -> +O
What was a consequence of removing DDT from the world market?
malaria infection rates spiked
infections today: 300 to 500 million
DDT activists vouch for limited reintroduction
- Mercury poisoning in 1956
- linked to local plastics factory that was dumping mercury into the bay
- fish and shellfish consumption resulted in high levels of methylmercury
Minamata Bay
Kyushu, Japan
How is methylmercury formed?
it is formed from mercury via its methylation by ubiquitous microorganisms
What were the health effects on humans following the Minamata Bay mercury incident?
- difficulty walking, swallowing, speaking, and hearing
- loss of brain weight and volume (brain atrophy)
- high rate of birth defects - severe brain damage, mental impairment, and delayed development
How did mercury poisoning enter into the human system following the Mnamata Bay incident?
biomagnification of methylmercury in the marine food chain with humans at the top of the chain
Pollution or Contamination?
- agricultural chemical
- air pollutants
- biological contaminants
- carcinogens
- chemicals
- extremely hazardous substances
- microorganisms
- radiation
- soil contaminants
- toxic substances
pollutants
What is a compound or chemical element present in air, water, food soil, dust, or other environmental media?
environmental chemical
What is the Third National Report on Human Exposure to Environmental Chemicals attempting to do?
quantify exposure to 148 common environmental chemicals
What is an ecosystem?
populations and communities residing in a defined area
aquatic or terrestial
Ecosystems can be composed of what two compartments?
abiotic - air, water, soils, and sediments
biotic - animal and plant life
What are the layers of the atmosphere?
- troposphere
- stratosphere
- mesosphere
- thermosphere
What layer of the Earth is contamination of the most concern?
troposphere
What is the composition of atmospheric air?
- oxygen, nitrogen
- “trace amounts” of chemical such as: carbon monoxide, sulfur dioxide, hydrogen sulfide, nitric acid, ammonia, formaldehyde, lead, oxides of nitrogen, particulates, etc..
- atmospheric water
Which air pollutant do these sources produce?
carbon monoxide
Which air pollutant do these sources produce?
nitrogen oxides
Where do about half of atmospheric pollutants come from?
industrial discharges
How can airborne chemicals enter into chemical reactions?
via oxidation and photolysis
What does this picture respresent?
chemical oxidation in air and formation of acid rain
In what kind of environment is this photolysis occuring?
clean environment
In what kind of environment is this photolysis occuring?
polluted environment
What are the fates of chemicals in the air?
- input
- dispersion
- transport
- reactions
- removal
Water contamination can affect humans directly as well as indirectly. How can contaminations affect humans indirectly?
1) digestion of fish and shellfish
2) decrease of food base in aquatic environments
3) decrease biodiversity in squatic environments
4) impair the cycle of elements in the Biosphere
What are some sources of contaminants?
- industrial waste
- agriculture
- pharmaceuticals
What are some types of contaminants?
- insecticides and herbicides
- heavy metals
- petroleum hydrocarbons
- chlorinated solvents (PCB)
- solluted suspended sediment
- estrogen mimicking compounds
How do chemical contaminats move within water medium?
water turbulence and diffusion
What can chemicals in the water interact with?
- sediments
- suspended particles in water column
- plants and animals residing there
