Solid & Hazardous Wastes
Solid waste—any unwanted or discarded material that is not a liquid or gas
 US generates about 33% of all solid waste with only 4.5% of the world’s population
 98.5% of solid wastes come from mining, oil & natural gas production, agriculture, & industrial activities to produce
consumer goods
 1.5% is municipal solid waste
 Average annual production of 440 billion pounds
 Averages 1600 pounds per person in US
 Fate of municipal solid wastes:
 Dumped into landfills—55%
 Recycled or composted—30%
 Burned in incinerators—15%
 EPA ranking of the most environmentally sound strategies for MSW
 Source reduction (including reuse and dematerialization)
 Recycling and composting
 Disposal in combustion facilities and landfills
Hazardous waste—legally defined as any discarded solid or liquid material that:
 contains one or more of 39 toxic, carcinogenic, mutagenic, or teratogenic compounds at levels that exceed established limits
 flammability (catches fire easily)
 reactivity (is reactive or unstable enough to explode or release toxic fumes)
 corrosiveness (is capable of corroding metal containers such as tanks, drums, & barrels)
 Does NOT include (excluded from regulation)
 Radioactive wastes
 Household disposal of hazardous compounds
 Mining wastes
 Hazardous waste laws do not regulate 95% of the US hazardous wastes
Love Canal, New York (1970s)—
 More than 20,000 tons of toxic wastes were buried in the 1940s through the 1950s
 Sold by the Hooker Chemical Company to the School Board for $1
 A school, playground and housing community developed
 1970s – higher than normal rainfall, raised the water table
 Chemicals began leaking into storm sewers, basements, and playgrounds (~1976)
 Serious medical problems arose including miscarriages, birth defects, and cancers (leukemia, liver cancer)
 1978 – government buyout of homes began (Lois Gibbs organized the town)
 Approximate final clean up cost – ~275 million dollars
 Leachate pumped out, soil was replaced, a new clay cap was installed
 Led to CERCLA (1980 Superfund Act)
 Oxychem was required to pay back ~130 million to the US and ~100 million to the state of New York
 June 1990—EPA declared the area safe and allowed selling of the homes again (Black Creek Village)
 Residents had to sign a waiver releasing the government of any responsibility should any illness occur as a result of living in
the area
Dealing with Solid & Hazardous Wastes
 Waste management
 Attempts to reduce environmental harm of producing wastes
 Burying wastes
 Burning wastes
 Shipping wastes to other places (Case Study – Khian Sea, led to the Basel Convention in 1989)
 Time required for waste material to decompose
 Organic wastes—1-2 weeks
 Paper—10-30 days
 Wood—10-15 years
 Tin, aluminum, & metal cans—100-500 years
 Plastics—1 million years
 Preventing pollution & wastes – Low Waste Approach
 Reduce waste & pollution
 Reuse as many things as possible
 Recycle and compost as much waste as possible
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Reducing wastes
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Chemically or biologically treat or incinerate waste that cannot be reduced, reused, or recycled
Bury what is left in state-of-the-art landfills
Decreasing consumption
Doing more with less (redesigning manufacturing processes to use less materials and energy)
Developing products that are easy to reuse, manufacture, and recycle
Designing products to last longer (tires)
Eliminating or reducing unnecessary packaging
Ecoindustry—use of resource exchange webs joining different industries in recycling wastes & products
Using trash taxes
 Pay-as-you-throw system
Reuse—form of waste reduction that:
 Extends resource supplies
 Keeps high-quality matter resources from being reduced to low-matter-quality waste
 Reduces energy use & pollution
 Most efficient method of reclaiming materials
 Refillable glass beverage bottles (reused up to 15 times)
 Only about 7% of the beer and soft drink market
 Shift from using disposable diapers to cloth diapers
Recycling—
 Primary (closed-loop) recycling—wastes discarded by consumers (post-consumer wastes) are recycled to
produce new products of the same type
 Reduces use of virgin resources & saves energy
 Secondary (open-loop) recycling—waste materials are converted into different and usually lower-quality
products
 Reduces energy requirements to produce product
 Recycling aluminum cuts energy use by 95%
 Materials-recovery Facilities—collection of mixed urban waste and machine separation to recover valuable
materials for sale to manufacturers as raw materials
 Can produce electricty
 Expensive
 Can emit toxic air pollution (addressed by wet scrubbers, electrostatic precipitators, sorbants)
 Produces toxic ashes after incineration of leftover trash
 Requires a high input of garbage to be financially successful
 Aluminum
 US gets 60% of its aluminum from virgin ore
 In 1999, 74% of all aluminum cans were recycled in the US
 Plastics
 Various types of polymer molecules made by chemically linking monomers of petrochemicals
produced from oil and natural gas
 Accounts for 22% of all MSW by volume
 Burning plastics releases dioxins (carcinogenic & toxic by-product of plastic manufacturing)
 Biodegradable & photodegradable plastics are made to break down into smaller pieces
o Affects more organisms in different trophic levels
 Problems in recycling plastics
o Plastics are difficult to isolate from other wastes
o Price of oil is so low that the cost of virgin plastic resins is about 40% lower than that of
recycled resins (has more become more economical as oil prices rise and as oil becomes
more scarce)
Incineration of Solid Wastes
 Reduces impact on landfills, but expensive to build
 Reduces volume of wastes by up to 80-90%
 Kills pathogens
 Leads to increased air pollution (lead, mercury, cadmium, sulfur oxides, etc.)
Sanitary Landfills—solid wastes are spread out in thin layers, compacted, & covered daily with clean soil
 Lined with clay and plastic before being filled with garbage
 Second impermeable layer collects leachate (rainwater contaminated as it percolates through the solid wastes)
 Leachate is pumped from bottom of landfill and sent to sewage treatment plants
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When full, landfills are covered with clay, sand, gravel, and topsoil to prevent water from seeping in
Network of pipes to collect landfill gas (methane & carbon dioxide)
86% of all older landfills have contaminated groundwater
Detoxification of Hazardous Wastes
 Bioremediation—microorganisms & enzymes are used to destroy toxic or hazardous substances or convert them to harmless
compounds
 Exxon Valdez – used microbes to help clean –up shoreline contamination
 Works well for organic wastes (pesticides, gasoline, diesel fuel, PCBs)
 Does not work well for toxic metals
 Phytoremediation—using natural or genetically engineered plants to filter and remove contaminants
 Sunflowers remove 95% of lead contamination in soils
 Canola plants soak up selenium from soil
 Advantages & disadvantages of phytoremediation
o Inexpensive
o Reduces erosion
o Aesthetically pleasing
o Can reduce the amount of material dumped into landfills
o Slow and effective only at depths reached by roots
o Contaminated plants may be eaten by wildlife
o Plant material may have to be disposed of in a hazardous waste landfill
Disposal of Hazardous Wastes
 Deep-well disposal—liquid hazardous wastes are pumped under pressure through a pipe into dry, porous geologic formations
far beneath aquifers
 Surface impoundments—excavated depressions, ponds, or lagoons into which liquid hazardous wastes are drained and stored
 EPA estimates that 90% of all surface impoundments threaten groundwater
 Secure hazardous-waste landfills
 Storage in drums and carefully buried
 NIMBY consequences
 Aboveground buildings—built of reinforced concrete & create a negative pressure to prevent the release of
toxic gases
Environmental Risk, Toxicology, & Human Health
Risk—probability of suffering harm from a hazard that can cause injury, disease, economic loss, or environmental damage
Risk assessment—involves identifying a real or potential hazard, determining the probability of its occurrence, and assessing the
severity of its impact
 Influenced by the information a person has, personal experience, media, etc.
 EPA—acceptable risk is 1:1 million
Types of hazards—
 Cultural hazards—unsafe working conditions, smoking, poor diet, unsafe sex,driving, poverty, etc.
 Chemical hazards—harmful chemicals in the air, water, soil, and food
 Physical hazards—ionizing radiation, fire, earthquake, flood, tornadoes, etc.
 Biological hazards—pathogens, pollen & allergens, animals
Toxicology—measure of how harmful a substance is
 Potential harm is dependent on
 Dosage
 Bioaccumulation—some molecules are absorbed & stored in specific organs or tissues at levels higher than
normally would be expected
 Biomagnification—levels of some toxins in the environment are magnified as they pass through a food web
 DDT, PCBs, & some radioactive isotopes
 Chemical interactions that can decrease or multiply the effects of a toxin
 Antagonistic interaction—reduce the harmful response
o Vitamins A & E interact to reduce body’s response to carcinogens
 Synergistic interaction—multiplies harmful effects
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Asbestos increase chances of lung cancer, but asbestos workers who smoke increase
chances of lung cancer 400x
Poison—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
Toxicity Testing
 Dose-response curves—shows the effects of various dosages of a toxic agent on a group of test organisms
 X-axis plot concentration of toxin & y-axis plots response
 Usually follows an S-shaped curve
 Epidemiology—study of the patterns of disease or other harmful effects from toxic exposure within defined
groups of people to figure out why some people get sick and other do not
Chemical Hazards
 Toxic chemicals—substances that are fatal to more than ½ of test animals (LD50) at given concentrations
 Hazardous chemicals—cause harm by being flammable, irritating or damaging to skin or lungs, interfering with oxygen
uptake, or inducing allergic reactions
 Mutagens—agents that cause random mutations to DNA molecules
 Most mutations are harmless due to repair mechanisms
 Teratogens—chemicals, radiation, or viruses that cause birth defects while the human embryo is growing & developing
during pregnancy
 PCBs, thalidomide, steroid hormones, arsenic, cadmium, etc.
 Carcinogens—chemicals, radiation, or viruses that cause or promote the growth of malignant tumors in which cells multiply
uncontrollably
 Metastasis—malignant cells break off from tumors and travel in body fluids to other parts
 10-40 years between exposure and symptom development
 Effects of Chemicals on Human Body Systems
 Immune system—HIV, ionizing radiation, malnutrition, & synthetic chemicals
 Nervous system—Neurotoxins
 Chlorinated hydrocarbons (DDT, PCBs, dioxins)
 Organophosphate pesticices
 Formaldehyde
 Chemicals of arsenic, mercury, lead, & cadmium
 Industrial solvents (toluene, xylene)
 Endocrine system—synthetic chemicals called hormonally active agents disrupts effects of hormones
Biological Hazards
 Nontransmissible Diseases—not caused by living things & do not spread from person to person
 Cardiovascular diseases, cancers, diabetes, etc
 Transmissible diseases—caused by living things and can be spread from person to person
 Pathogens are spread via air, water, food, body fluids, insects
 Four biosafety levels of pathogens
 Level 1—agents that do not usually cause human disease
 Level 2—Limited transmission with antibiotic & vaccine treatments (Measles, Hepatitis, etc)
 Level 3—Potential for serious or potentially lethal infection (TB, HIV)
 Level 4—exotic agents with no vaccine or therapy (Ebola)
 WHO’s seven deadliest infectious diseases
 Acute respiratory infections (pneumonia & flu)—3.7 million/yr
 HIV/AIDS—2.6 million/yr
 Diarrheal diseases—2.5 million/yr
 Tuberculosis—2 million/yr
 Malaria—1.5 million/yr
 Measles—1 million/yr
 Hepatitis B—1 million/yr
 Treatments for infectious diseases
 Bacterial & protozoan diseases are treated with antibiotic drugs
 Viral disorders are treated with vaccines before infection
 Factors affecting the spread of transmissible diseases
 Increased international air travel
 Migration to urban areas
 Migration to uninhabited rural areas & deforestation of tropical developing nations
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 Hunger & malnutrition
 Increased rice cultivation (mosquito breeding)
 Global warming
 High winds or hurricanes
 Accidental introduction of insect vectors
 Flooding
Epidemiological transition—infectious diseases of childhood and the chronic diseases of adulthood become more important
in causing mortality
 Infectious & parasitic diseases cause 43% of deaths in developing nations but only 1% in developed nations
Risk Analysis
 Identifying hazards & evaluating their associated risk (Risk Assessment)
 Ranking risks
 Determining options & making decisions about reducing or eliminating risk (Risk Management)
 Cost-benefit analysis
 Informing decision makers and public about risk
 Greatest risks in terms of reduced life span, exposure, etc is poverty followed by personal choices
 Reducing risk
 Not smoking
 Avoid excess sunlight
 Not drink alcohol
 Reduce consumption of foods containing cholesterol
 Eat a variety of fruits & vegetables
 Exercise regularly & lose excess weight
 Drive less and more safely