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APES Toxics Wastes and Agriculture Exam Study Guide
Environmental Health
❖ Risk Assessment: Assesses environmental factors that influence human health and quality of life.
❖ Risk Management: Seeks to prevent adverse effects on human health and ecological systems. Contains
environmental toxicology within
its scope.
➢ Risk = the mathematical
probability that some
harmful outcome will
result from a given
action, event, or
substance
➢ In the U.S., most risk
management is
conducted by federal and
state agencies like the
EPA. FDA and OSHA
(Occupational Health and Safety Administration) for workplace hazards
❖ TSCA: Toxic Substances Control Act (regulates: pesticides, industrial chemicals, and any synthetic chemicals not
covered by other agencies)
➢ EPA is charged with monitoring 75,000 industrial chemicals.
➢ Too many chemicals, too little time, people, resources
➢ Only 10% of chemicals on the market are thoroughly tested.
➢ Only 2% are screened for carcinogens, mutagens, teratogens.
➢ <1% are government regulated.
➢ ~0% are teste
➢ d for endocrine, nervous, or immune effects.
❖ FIFRA: Federal Insecticide, Fungicide and Rodenticide Act
➢ Pesticides to be introduced to market in the U.S. need to be registered with the EPA.
➢ Registration involves risk assessment and risk management.
➢ EPA assesses research from the manufacturer along with any outside research.
➢ EPA can set restrictions on use, or even ban a product.
❖ “Innocent until proven guilty”:
➢ Assume harmless until shown to be harmful
➢ Industry can introduce any products it wants.
➢ Industry has pressured government to take an “innocent-until-proven-guilty” approach
❖ Precautionary principle:
➢ Assume harmful until shown to be harmless
➢ Industry cannot introduce a product until it is very thoroughly tested and shown convincingly to be
harmless.
➢ Environmental advocates have pressured government to follow the precautionary principle.
❖ Threats Include:
➢ Physical hazards (floods, blizzards, landslides, radon, UV exposure)
➢ Chemical hazards (disinfectants, pesticides)
➢ Biological hazards (viruses, bacterial infections)
➢ Cultural or lifestyle hazards (drinking, smoking, bad diet, crime in neighborhood)
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❖ Disease- in a communicable or transmissible disease, a pathogen attacks a host or either directly or through a
vector (e.g., mosquito that transfers a malaria parasite to hosts)
➢ Infectious disease causes 25% of deaths in the world and nearly half of deaths in developing nations.
➢ 6 diseases account for 80% of infectious disease deaths
❖ Indoor Health Hazards include:
➢ Substances in plastics and consumer products
➢ Lead in paint and pipes
➢ Radon
➢ Asbestos
➢ PBDE fire retardants
❖ Of the 100,000 synthetic chemicals on the market today, very few have been thoroughly tested for harmful
effects.
❖ Silent Spring and Rachel Carson
➢ Carson’s 1962 book alerted the public that DDT and other pesticides could be toxic to animals and
people.
➢ Further research led the EPA to ban DDT in 1973.
➢ These developments were central to the modern environmental movement.
Toxicity
Toxicology (The study of poisonous substances and their effects on
humans and other organisms, Toxicologists assess and compare toxic
agents, or toxicants, for their toxicity, the degree of harm a substance
can inflict, Environmental toxicology focuses on effects of chemical
poisons released into the environment)
❖
Toxicant Types:
➢
Teratogens (Ex. The drug thalidomide, used to relieve nausea
during pregnancy, turned out to be a potent teratogen, and caused
thousands of birth defects before being banned in the 1960s.)
➢
Carcinogens: cause cancer
➢
Mutagens: cause mutations in
DNA
➢ Allergens: cause unnecessary immune response
➢ Neurotoxins: damage nervous system
➢ Endocrine disruptors: interfere with hormones
❖ Airborne Toxicants: Volatile chemicals can travel long distances on
atmospheric currents. PCBs are carried thousands of miles from developed
nations of the temperate zone up to the Arctic, where they are found in tissues
of polar bears and seals
➢ Some chemicals are more stable than others, persisting for longer in
the environment.
■ DDT and PCBs are persistent.
■ Bt toxin in GM crops is not persistent.
➢ Most toxicants degrade into simpler breakdown products. Some of
these are also toxic, Temperature, moisture, sun exposure, etc., affect
rate of degradation.
➢ (DDT breaks down to DDE, also toxic.)
➢ Fat-soluble ones are stored.
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■ DDT is persistent and fat soluble which builds up in tissues
Bioaccumulation- chemicals may be passed on to animals that eat the organism—up the food chain
Biomagnification- At each trophic level, chemical concentration increases
❖ Dose Response Analysis: Method of determining toxicity of a substance by measuring response to different doses
which uses lab animals
➢ Mice and rats breed quickly, and give data relevant to humans
because they share mammal physiology with us
➢ Responses to doses are plotted on a dose-response curve
➢ LD50 = dose lethal to 50% of test animals
➢ Threshold = dose at which response begins
➢ By extrapolating the curve out to higher values, we can predict
how toxic a substance may be to humans at various concentrations.
❖ Human Epidemiology
➢ Human Studies rely on: Case history= observation and analysis
of individual patients
■ Not all people are equal. Sensitivity to toxicant can vary with sex, age, weight, etc.
■ Exposure types include: acute = high exposure in short period of time, and chronic = lower
amounts over long period of time
➢ Epidemiological Studies= long term, large scale comparisons of different groups of people
■ These studies prove correlation only and it takes many years to get results
➢ ***Mixes of toxicants may cause effects greater than the sum of their individual effects.
■ These are called synergistic effects.
❖ Endocrine Disruptors: (hormone system) chemicals, once inside the bloodstream, can “mimic” hormones. If
molecules of the chemical bind to the sites intended for hormone binding, they cause an inappropriate response.
❖ Overall: We will never attain complete knowledge of risks.
Waste
Types:
❖ Municipal solid waste = from homes, institutions, small
businesses
❖ Industrial solid waste = from production of consumer goods,
mining, petroleum extraction, agriculture
❖ Hazardous waste = toxic, chemically reactive, flammable, or
corrosive
❖ Wastewater = water used in homes, businesses, etc., and
drained or flushed, plus runoff from streets
Waste Management includes: Source Reduction (Reducing the
amount of waste entering the waste stream; this is the best method),
Recovery (Recycling and composting; this is the next best); Disposal
❖ Paper is the biggest source of waste in the US (35.2%)
❖ AVG waste per person:
➢ United States, 2.0 kg/day (The U.S. wastes 2.7 times
what it did in 1960.)
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➢ Canada, 1.7
➢ The Netherlands, 1.4
Landfills:
❖ In modern sanitary landfills, waste is buried or piled up
so as to avoid contamination of the environment.
❖ The Resource Conservation and Recovery Act
(RCRA) specifies guidelines for how waste should be
added to a landfill
❖ Landfills can excrete leachate.
➢ Trash rots VERY slowly in landfills.
➢ Paper products take up 40% of landfill space.
➢ Plastic packaging is overrated as a waste
problem.
❖ Bacterial decomposition inside landfills produces
methane, the main component of natural gas. This way,
Greenhouse gas methane is prevented from reaching
atmosphere
❖ Source reduction, or preventing waste in the first place, is a better option than disposal.
❖ Reusing items is a powerful way to reduce one’s waste.
❖ Each year U.S. industries generate 7.6 billion tons of total waste.
Incineration:
❖
A controlled process of burning mixed solid waste at
extremely high temperatures
❖
Reduces volume by 90% and Remaining ash disposed of
at landfill
❖
can create new chemical compounds and emit toxic
chemicals from the stacks
❖
Waste to energy (WTE) facilities use heat from furnaces
to boil water. Steam turns turbines and generators
Composting: The conversion of organic waste into mulch or
humus by encouraging natural processes of decomposition
Recycling:
❖ Collecting materials that can be broken down and reprocessed in order to manufacture new items and Diverts ~55
million tons of materials away from disposal each year
❖ items are taken to materials recovery facilities (MRFs), where workers prepare them for reprocessing.
❖ Waste is generated at several points in the life cycle of products
❖ The less waste produced per item manufactured, the more efficient the process is, from a physical standpoint, But
it may not mean it is economically efficient.
Hazardous waste
❖ Ignitability: substances catch fire
❖ Corrosivity: substances corrode metals
❖ Reactivity: substances are chemically unstable and react with other chemicals in dangerous ways
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❖ Toxicity: substances are known to be harmful to human health
❖ Hazardous Wastes can include heavy metals ((mercury, lead, chromium, arsenic, cadmium, tin, copper — from
industry, mining, consumer products)
➢ and Organic Compounds ((synthetic pesticides, petroleum products, rubber, solvents, preservatives…))
❖ Disposal Methods:
➢ Surface impoundments: Ponds lined with plastic and clay. Liquid hazardous waste evaporates, leaving
residue. Really only for temporary storage; not ideal because waste may overflow, blow out, vaporize, or
leak
➢ Deep-well injection: Hazardous waste is pumped deep underground into porous and stable rock
formations, away from aquifers, can leak into groundwater
➢ Unscrupulous individuals or businesses sometimes illegally dump hazardous waste to avoid disposal fees.
❖ Radioactive waste is s special type of hazardous waste, it's especially dangerous and is produced by military and
hospitals; some by research institutions
❖ Cleanups:
➢ 1980: Comprehensive Environmental Response Compensation and Liability Act (CERCLA) established
Superfund, administered by EPA (Budget from Congress plus trust fund from tax on chemicals, Tries to
charge responsible parties for cleanup through polluter-pays principle)
Agriculture
Global Food Production:
❖ World agricultural production has risen faster than
human population
❖ the world still has 850 million hungry people, largely
due to inadequate distribution
❖ Global food security is a goal of scientists and
policymakers worldwide.
Nutrition
❖ Undernourishment = too few calories (especially
developing world)
❖ Overnutrition = too many calories (especially developed world)
❖ Malnutrition = lack of nutritional requirements (causes numerous diseases, especially in developing world)
The Green Revolution
❖ Techniques to increase crop output per unit area of cultivated land (since world was running out of arable land)
including a technology transfer to developed world in 1940s–80s: Norman Borlaug began in Mexico, then India.
❖ Special crop breeds (drought-tolerant, salt-tolerant, etc.) are a key component, they enable food production to
keep pace with population
❖ Intensification of agriculture causes environmental harm:
➢ Pollution from synthetic fertilizers
➢ Pollution from synthetic pesticides
➢ Water depleted for irrigation
➢ Fossil fuels used for heavy equipment
❖ ***without the green revolution, much more land would have been converted for agriculture, destroying forests,
wetlands, and other ecosystems
❖ Begun in U.S. and other developed nations; exported to developing nations like India and those in Africa.
❖ Intensified agriculture meant monocultures, vast spreads of a single crop, This is economically efficient, but
increases risk of catastrophic failure (“all eggs in one basket”). They’ve reduced crop diversity.
❖ 90% of all human food now comes from only 15 crop species and 8 livestock species
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Pesticides
❖ Artificial chemicals have been developed to kill insects (insecticides), plants (herbicides), and fungi (fungicides).
These poisons are collectively called pesticides
❖ Many pests evolve resistance to pesticides. Those few pests that survive pesticide applications because they
happen to be genetically immune will be the ones that reproduce and pass on their genes to the next generation.
Synthetic chemicals can pollute and be health hazards
❖ Biological control (biocontrol)
➢ entails battling pests and weeds with other organisms that are natural enemies of those pests and
weeds.
➢ Most biocontrol agents are introduced from elsewhere. Some may turn invasive and become pests
themselves!
❖ Integrated pest management (IPM) Combines biocontrol, chemical, and other methods
➢ Biocontrol, Pesticides, Close population monitoring, Habitat
modification, Crop rotation, Transgenic crops, Alternative
tillage, Mechanical pest removal
❖ Sustainable agriculture
➢ Does not deplete soils faster than they form nor does it
reduce healthy soil, clean water, and genetic diversity
essential for long-term crop and
livestock production
➢ Low-input agriculture = small amounts of pesticides,
fertilizers, water, growth hormones, fossil fuel energy, etc
➢ Organic agriculture = no synthetic chemicals used. Instead,
biocontrol, composting, etc
■ Studies have shown organic farm fields to have
deeper topsoil and greater earthworm activity, both
signs of healthy soil
■ Through community-supported agriculture,
consumers pay farmers for a share of their yield.
Pollination
❖ In many plants, animals transfer pollen to pollinate female plants, in
mutualistic interaction to obtain nectar or pollen.
❖ Pollinating insects are vital for many of our crop plants
❖ Overuse of pesticides can backfire by killing beneficial pollinators.
GMO’s
❖ Manipulating and engineering genetic material in the lab may
represent the best hope for increasing agricultural production further
without destroying more natural lands
➢ Genetic engineering (GE) = directly manipulating an organism’s genetic material in the lab by adding,
deleting, or changing segments of its DNA
➢ Genetically modified (GM) organisms = genetically engineered using recombinant DNA technology
➢ Recombinant DNA = DNA patched together from DNA of multiple organisms (e.g., adding diseaseresistance genes from one plant to the genes of another)
➢ Genes moved between organisms are transgenes, and the organisms are transgenic
➢ These efforts are one type of biotechnology, the material application of biological science to create
products derived from organisms.
❖ Genetic engineering vs. traditional breeding
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➢ Similarities: We have been altering crop genes (by artificial selection) for thousands of years, There is no
fundamental difference: both approaches modify
organisms genetically
➢ Differences: GE can mix genes of very different species,
GE is in vitro lab work, not with whole organisms, GE
uses novel gene combinations that didn’t come together
on their own.
❖ Examples: Golden Rice, StarLink Corn, Sunflowers and
superweeds
❖ Two-thirds of U.S. soybeans, corn, and cotton are now
genetically modified strains.
➢ 17 nations plant GM crops on 200 million acres, but
most are grown by 5 nations
➢ Europe: has followed precautionary principle in approach to GM foods. Governments have listened to
popular opposition among their citizens.
➢ U.S.: GM foods were introduced and accepted with relatively little public debate
❖ Native cultivars of crops are important to preserve, in case we need their genes to overcome future pests or
pathogens. Diversity of cultivars has been rapidly disappearing from all crops
throughout the world
❖ Feedlots:
➢ Increased meat consumption has led to animals being raised in feedlots (factory
farms), huge pens that deliver energy-rich food to animals housed at extremely high
densities
➢ Immense amount of waste produced, polluting air and water nearby, Intense
usage of chemicals (antibiotics, steroids, hormones), some of which persist in
environment
■ However, if all these animals were grazing on rangeland, how much more natural
land would be converted for agriculture?
❖ Food choices = energy choices, Energy is lost at each trophic level. When we eat
meat from a cow fed on grain, most of the grain’s energy has already been spent on
the cow’s metabolism
Aquaculture (The raising of aquatic organisms for food in controlled environments)
❖ Provides 1/3 of world’s fish for consumption
❖ The fastest growing type of food production
❖ Global aquaculture has been doubling about every 7 years
❖ Benefits Include:
➢ Provides reliable protein source for people, increases food security, Can be small-scale, local, and
sustainable.
➢ Reduces fishing pressure on wild stocks, and eliminates bycatch.
➢ Uses fewer fossil fuels than fishing and Can be very energy efficient
❖ Problems include:
➢ Density of animals leads to disease, antibiotic use, risks to food security, It can generate large amounts of
waste
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➢ Sometimes animals are fed fish meal from wild-caught fish. Farmed animals may escape into the wild and
interbreed with, compete with, or spread disease to wild animals
***We must shift to sustainable agriculture if our planet is to support 9 billion people by mid-century without further
environmental degradation
Agriculture
❖ We have converted 38% of Earth’s surface for
agriculture, the practice of cultivating soil,
producing crops, and raising livestock for human
use and consumption.
❖ Croplands (for growing plant crops) and
rangelands (for grazing animal livestock) depend
on healthy soil
❖ Europe’s land is most degraded because of its long
history of intensive agriculture, But Asia’s and
Africa’s soils are fast becoming degraded.
❖ Most soil degradation is caused by:
➢ Livestock Overgrazing
➢ Deforestation
➢ Cropland agriculture
❖ Subsistence agriculture = family produces only enough for itself, Intensive traditional agriculture = family uses
animals, irrigation water, and fertilizer to produce enough to sell at market
➢ Modern intensive agriculture demands that vast fields be planted with single types of crops, aka
Monoculture (uniform planting of a single crop)
❖ Industrialized agriculture is displacing traditional farming, just as traditional farming displaced hunting and
gathering.
Soil
Soil is a complex mixture
of organic and inorganic
components.
❖ Parent material:
starting material affects
composition of the
resulting soil.
❖ It can include
bedrock, the solid rock
that makes up the Earth’s
crust
❖ Weathering: the
processes that break down rocks and minerals, and the first step in soil
formation.
❖ Erosion: the movement of soil from one area to another.
Soil Profile: Consists of layers called horizons
❖ Simplest consists of A (topsoil), B (subsoil), and C (parent material) But must have O, A, E, B, C, and R
➢ O Horizon: Organic or litter layer
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➢ A Horizon: Topsoil; mostly inorganic minerals with some organic material and humus mixed in; crucial
for plant growth
➢ E Horizon: Eluviation horizon; loss of minerals by leaching, a process whereby solid materials are
dissolved and transported away
➢ B Horizon: Subsoil; zone of accumulation or deposition of leached minerals and organic acids from above
➢ C Horizon: Slightly altered parent material
➢ R Horizon: Bedrock
❖ Soil can be characterized by color and several other traits, Like: Texture,
Structure, pH
❖ Soil Texture is determined by size of particles. There’s:
➢ Clay = particles < 0.002 mm diameter
➢ Silt = particles 0.002–0.05 mm diameter
➢ Sand = particles 0.05–2.0 mm diameter
❖ Best for plant growth is loam, an even mix of these three types.
❖ Soil pH: the degree of acidity or alkalinity, which influences a soil’s
ability to support plant growth
➢ Soil and soil profiles vary from place to place, with implications for
agriculture.
❖ Erosion = removal of material from one place and its transport
elsewhere by wind or water
➢ Caused by Over Cultivating, too much plowing, poor planning,
Overgrazing rangeland with livestock, Deforestation, especially on slopes.
Humans are over 10 times more influential at moving soil than are all other
natural processes combined.
Deposition = arrival of eroded material at a new
location
Desertification: A loss of more than 10% productivity
due to: Erosion, Soil compaction, Forest removal,
Overgrazing, Drought, Salinization, Climate change,
Depletion of water resources
As a result of the Dust Bowl, U.S. Soil Conservation
Act of 1935 and the Soil Conservation Service (SCS)
were
created. SCS: local agents in conservation
districts worked with farmers to disseminate scientific
knowledge and help them conserve their soil
Several farming strategies to prevent soil degradation:
➢ Crop rotation (Alternating the crop planted
(e.g., between corn and soybeans) can restore
nutrients to soil and fight pests and disease.)
➢ Contour farming (Planting along contour lines
of slopes helps reduce erosion on hillsides)
➢ Intercropping (Mixing crops such as in strip cropping can provide nutrients and reduce erosion)
➢ Terracing (Cutting stairsteps or terraces is the only way to farm extremely steep hillsides without causing
massive erosion. It is labor-intensive to create, but has been a mainstay for centuries in the Himalayas and
the Andes.)
➢ Shelterbelts (Rows of fast-growing trees around crop plantings provide windbreaks, reducing erosion by
wind.)
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➢ Conservation tillage (No-till and reduced-tillage farming leaves old crop residue on the ground instead of
plowing it into soil. This covers the soil, keeping it in place)
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Irrigation
The artificial provision of water to support agriculture, 70% of all freshwater used by humans is used for
irrigation, Irrigated land globally covers more area than all of Mexico and Central America combined.
Over Irrigation can raise the water table high enough to suffocate plant roots with waterlogging
Salinization (buildup of salts in surface soil layers) is a more widespread problem, Evaporation in arid areas
draws water up through the soil, bringing salts with it. Irrigation causes repeated evaporation, bringing more salts
up
In conventional irrigation, only 43% of the water reaches plants. Efficient drip irrigation targeted to plants
conserves water, saves money, and reduces problems like salinization.
Fertilizers
Inorganic fertilizers = mined or synthetically manufactured
mineral supplements
Organic fertilizers = animal manure, crop residues, compost,
etc.
❖ Over Applied fertilizer can run off into local water
bodies, infiltrate into aquifers, and evaporate into air.
❖ Overgrazing: When livestock eat too much plant cover
on rangelands, impeding plant regrowth
❖ Not all grazing is harmful. Responsible ranchers
maintain the productivity of their soil and grass
Logging
❖ Careless forestry practices can also cause erosion and
soil degradation
❖ The U.S. has continued to pass soil conservation legislation in recent years:
➢ Food Security Act of 1985
➢ Conservation Reserve Program, 1985
➢ Freedom to Farm Act, 1996
➢ Low-Input Sustainable Agriculture Program, 1998