8.1 - Sources of Pollutants

Point vs. Nonpoint Pollutant Sources

• Point Source

  • Pollutant that enters the environment form an easily identified and confined place

  • You can “point” 👉 to it

• Nonpoint Source

  • Pollutants entering the environment from many places at once. Difficult to “point” to one individual source

Must-Know Pollution Examples

• Point Source Examples

  • Animal waste runoff from a CAFO (ammonia (N), fecal coliform bacteria)

  • Emissions from smokestack of a coal power plant (CO2, NOx, SO2, PM)

  • BP Oil Spill (hydrocarbons, benzene)

• Nonpoint Source Examples

  • Urban runoff (motor oil, nitrate fertilizer, road salt, sediment)

  • Pesticides sprayed on agricultural fields; carried by wind and washed off large agricultural regions ino bodies of water

  • Estuaries and bays are polluted by many nonpoint pollution sources from the large watersheds that empty into them

Pollutants vs. Pollution

• Pollutants

  • Specific chemicals or groups of chemicals from specific sources with specific env. & human health effects

  • Much more likely to earn you FRQ credit

• Pollution

  • Vague, nondescript term for any substance that is harmful to the environment

  • Never acceptable on an APES FRQ

    • Exceptions:

      • Specific categories of pollution: thermal pollution, noise pollution, sediment pollution

8.2 - Human Impacts on Ecosystems

Range of Tolerance

• Organisms have range of tolerance for abiotic conditions in their habitat

  • pH, temperature, salinity (saltiness), sunlight, nutrient levels (ammonia, phosphate)

• Organisms also have range of tolerance for pollutants that human activities release into their habitats

  • Pollutants cause physiological stress such as

  • Limited growth

  • Limited reproductive function

  • Difficulty respiring (breathing), potentially asphyxiation (suffocation)

  • Hormonal disruption

  • Death (if concentration of pollutant is high enough)

Environmental Effects of Acid Rain

• pH Tolerance

  • As pH decreases (more acidic) outside optimal range for a species, pop. declines

    • When pH leaves range of tolerance, they cannot survive at all, due to:

      • Aluminum toxicity

      • Disrupted blood osmolarity (Na+/Cl- balance disrupted at low pH)

  • Indicator species can be surveyed and used to determine conditions of an ecosystem (soil, water, etc.)

    • Ex: high whitemoss/filamentous algae pop. indicates pH < 6.0

    • High crustacean pop. indicates pH > 6.0

Temperature Tolerance of Reef Algae

• Coral reef = mutualistic relationship between coral & photosynthetic algae called zooxanthellae; algae supply sugar & coral supply CO2 + detritus (nutrient containing org. matter.)

• Algae have narrow temperature tolerance and leave the reef when temp. rises

  • Pollutants from runoff (sediment, pesticides, sunscreen) can also force algae from reef

• Coral lose color & become stressed and vulnerable to disease without algae (main food source)

Human Impacts on Coral Reef

• Humans disrupt coral reef ecosystems via greenhouse gas emissions

  (warming ocean temp. & bleaching coral)

• Overfishing decreases fish populations in coral reef ecosystems & bottom trawling can break reef structure and stir up sediment

• Urban and agricultural runoff also damages coral reef ecosystems

  • Sediment pollution: sediment carried into the ocean by runoff makes coral reef waters more turbid, reducing sunlight (photosynthesis)

  • Toxicants: chemicals in sunscreen, oil from roadways, pesticides from ag. runoff

  • Nutrients (P/N): ammonia from animal waste, nitrates/phosphates from ag. or lawn fertilizers

Oil Spill Effects

• Hydrocarbons in crude oil (petroleum) are toxic to many marine organisms and can kill them, especially if they ingest (eat) the oil or absorb through gills/skin

• Other physiological effects:

  • Decreased visibility and decreased photosynthesis due to less sunlight penetrating water surface

  • Oil sticking to bird feathers

  • Oil sinking to bottom and killing bottom-dwellers due to: direct toxicity or suffocation

• Oil can wash ashore and decrease tourism revenue and kill fish, decreasing fishing industry revenue, hurt restaurants that serve fish

  • Oil can settle deep in root structures of estuary habitats like mangroves or salt marshes

    • Can be toxic to salt marsh grasses, killing them and loosening their root structure, leading to coastline erosion

      • Can remove habitats used by fish & shellfish for breeding grounds

Oil Spill Clean Up

• Oil spills can occur when an underwater oil well explodes/blows out (BP Gulf Spill) or when a tanker runs into a rock/iceberg and is punctured (Exxon Valdez)

  • Cleanup can involve booms on surface to contain spread and ships with vacuum tubes to siphon oil off of the surface or devices to skim it off

  • Physical removal of oil from beach sand and rocks with towels, soaps, shovels

  • Chemical dispersants sprayed on oil slicks to break up and sink to the bottom

    • Clears up surface, but can smother bottom-dwellers

    • Dispersant chemicals may be harmful

  • Burning oil off the surface

8.8 - Biomagnification

Bioaccumulation

• Absorption and concentration of compounds (especially fat-soluble ones like POPs) in the cells & fat tissues of organisms

  • B/c fat-soluble compounds like POPs and methylmercury don’t dissolve easily in water, they don’t enter blood easily & don’t leave the body in urine easily

    • Instead they build up in fat tissue

    • This leads to them building up to reach higher and higher concentrations in the organism over time

Biomagnification

• Increasing concentrations of fat-soluble compounds like methylmercury and POPs in each level up the trophic pyramid or food web/chain

• Biomagnification begins with POPs or methylmercury in sediments or plants in an ecosystem (phytoplankton, grass)

  • Primary consumers (zooplankton, bottom-feeding fish, insects) take in POPs by eating producers, causing bioaccumulation of POPs in their tissues

  • Secondary consumers eat primary consumers and take in the POPs in their tissues

    • Because of the 10% rule, organisms at each successive trophic level need to eat more and more biomass to receive enough energy, leading to higher and higher POP levels over their lifetimes

    • Large predators like salmon, dolphins, and whales have the highest POP/methylmercury levels

DDT Biomagnification

• DDT was banned in many developed nations, but still persists in sediments of many bodies of water

  • Taken in by bottom feeders/zooplankton & biomagnified at higher trophic levels

  • Reach highest levels in top predators, esp. predatory birds like eagles & osprey

    • Causes thinning of the eggshells in these birds

    • Linked to massive pop. decline of bald eagle in US, which prompted the passage of the Endangered Species Act (73’)

Methylmercury Biomagnification

• Mercury is emitted from burning coal & by volcanoes, carried by wind, and deposited in water where bacteria convert it into toxic methylmercury

  • Taken in by phytoplankton & biomagnified at higher trophic levels

  • Reach highest levels in top predators, tuna, sharks, whales

    • Neurotoxicant: damages the central nervous system of animals

  • Human exposure to methylmercury & POPs comes from eating large predatory fish like tuna & salmon (and other seafood)

    • Damage to human nervous system (esp. developing fetus) and disrupt the reproductive system

8.3 - Endocrine Disruptors and Industrial Water Pollutants

Endocrine Disruptors

• Chemicals that interfere with the endocrine (hormonal) systems of animals

• Bind to cellular receptors meant for hormones, blocking the hormone from being received, or amplifying its effects

  • Human medications that pass through urine & into sewage or are flushed down toilet are a common source (meant to influence human hormones, so they can also disrupt animals’)

• Example:

  • atrazine (herbicide) binds to receptors of cells that should convert estrogen into testosterone in male frogs, leading to: high estrogen in males, low sperm count, even feminization (development of eggs in the testes or ovary formation)

Endocrine Disruptors

• Atrazine

  • broad-spectrum herbicide used to control weeds & prevent crop loss

    • Applied to ag. fields, runs off into local surface or groundwater or is carried by wind

    • Can contaminate human well-water, or enter body via unwashed produce

• DDT

  • broad-spectrum insecticide that was phased out, but still persists in env.

    • Applied to ag. fields, runs off into local surface or groundwater or is carried by wind

• Phthalates

  • compounds used in plastic and cosmetic manufacturing

    • Enter surface & groundwater via intentional dumping of trash, or chemical waste from plastic/cosmetic factories improperly disposing of waste, landfill leaching

    • Also found in some cosmetics & plastic food containers (#3 plastic & “fragrance”)

• Lead, arsenic, mercury

  • heavy metals

• Many human medications that enter sewage via human urine or flushed meds

Mercury

• mercury: naturally occurring in coal, released by anthropogenic activities:

  • Coal combustion, trash incineration, burning medical waste, heating limestone for cement

    • Attaches to PM released by burning & deposits in soil/water wherever PM settles

    • Can be released if coal ash stored in ponds overflow & runoff

  • Endocrine disruptor: inhibits estrogen & insulin (interferes with menstrual cycle & ovulation)

  • Teratogen: (chemical harmful to developing fetuses) can accumulate in fetus brain

    • Pregnant women can reduce risk by eating less seafood

• Mercury itself isn’t toxic, but bacteria in water sources convert it to methylmercury which is highly toxic to animals (neurotoxicant that damages central nervous system)

Arsenic and Lead

• arsenic: naturally occurring element in rocks underground that can dissolve into drinking water; Natural release into groundwater can be worsened by mining

  • Anthropogenic sources: formerly in pesticides applied to ag. Fields (can still linger in soil, wood treatment chemicals to prevent rot, coal combustion & ash

    • Carcinogenic: (lungs, bladder, kidneys) & endocrine disrupting

    • Endocrine disruptor: (specifically glucocorticoid system)

      • Can be removed with water filters

• lead: found in old paint (in homes), old water pipes, and soils contaminated by PM from vehicle exhaust before lead was phased out of gas in 70s

  • Also released in fly ash (PM) of coal combustion

    • Neurotoxicant (damages central nervous system, especially in children)

    • Endocrine disruptor

      • Can be removed with water filters

Coal Ash

• Coal ash can be a source of mercury, lead, and arsenic

  • Can attach to fly ash (PM) from smokestack and be carried by wind, deposited in ecosystems far away

  • Both fly and bottom coal ash are often stored on site in ponds, dug into soil & lined with plastic (sometimes)

    • Ponds can leach into groundwater, contaminating it with arsenic, lead, mercury

    • Ponds can overflow & runoff into nearby surface waters & agricultural fields

8.4 - Human Impacts on Wetlands and Mangroves

Wetlands

• An area with soil submerged/saturated in water for at least part of the year, but shallow enough for emergent plants

• Wetland plants have adapted to living with roots submerged in standing water (cattails, lily pads, reeds)

• Ecosystem Services of Wetlands

  • Provisioning: habitat for animal & plant foods

  • Regulating: groundwater recharge, absorb. of floodwater, CO2 sequestration

  • Supporting: H2O filtration, pollinator habitats, nutrient cycling, pest control

  • Cultural: tourism revenue, fishing license, camping fees, ed/med research

Threats to Wetlands

• Pollutants: nutrients (N/P), sediment, motor oil, pesticides, endocrine disruptors

• Development: wetlands can be filled in or drained to be developed into homes, parking lots, stores, or agricultural land

• Water diversion upstream for flood control, agriculture, or drinking water can reduce water flow and dry up wetlands (ex: Everglades) ⬇

  • Dam construction for flood control/hydroelect. reduces water & sediment (N/P) flow to wetlands

• Overfishing: disrupts food web of wetlands (decrease in fish predators, increase in prey)

8.5 - Eutrophication

Eutrophication Process

• B/c they’re limiting nutrients in aq. ecosystems, extra input of N & P lead to eutrophication (excess nutrients) which fuels algae growth

  • Algae bloom covers surface of water, blocking sunlight & killing plants below surface

  • Algae eventually die-off; bacteria that break down dead algae use up O2 in the water (b/c decomp. = aerobic process)

  • Lower O2 levels (dissolved oxygen) in water kills aquatic animals, especially fish

  • Bacteria use up even more O2 to decompose dead aq. animals

  • Creates pos. feedback loop: less O2 → more dead org. → more bacterial decomposition → less O2

Cultural Eutrophication

• Anthropogenic nutrient pollution (N & P) that leads to eutrophication

  • Algae bloom due to increase of N/P → decreased sunlight → plants below surface die → bacteria use up O2 for decomp. → hypoxia (low O2) & dead zones

• Major N/P sources:

  • Discharge from sewage treatment plants (N/P in human waste & phosphates in soaps/detergents)

  • Animal waste from CAFOS

  • Synthetic fertilizer from ag. fields & lawns

Oligotrophic Waterways

• Waterways with low nutrient (N/P) levels, stable algae pop, and high dissolved oxygen

  • Can be due to lack of nutrient pollution, or age of the body of water

  • Aquatic ecosystems naturally undergo succession

    • Sediment buildup on bottom (benthic zone) leads to higher nutrient levels

    • Overtime, ponds naturally shift from oligotrophic, to mesotrophic, to eutrophic

Dissolved Oxygen and Dead Zones

• Decrease in dissolved oxygen (hypoxia) is what causes a dead zone

  • All aq. life requires DO (dissolved oxygen) in water for respiration

  • As DO decreases, fewer species can be supported

    • Most fish require at least 3.0 ppm to survive, 6.0 ppm to reproduce

8.6 - Thermal Pollution

Solubility of Oxygen and Temperature

• Solubility: the ability of a solid/liquid/gas to dissolve into a liquid (oxygen dissolving into water in this case)

• Inverse relationship between water temp & oxygen solubility

  • As water temp. ⬆ DO (dissolved oxygen) ⬇

• Thermal pollution: when heat released into water has negative effects on organisms living in the water

  • Heat increases respiration rate of aquatic organisms (thermal shock)

  • Hot water also has less O2

    • This can lead to suffocation without enough O2 to support respiration

Sources of Thermal Pollution

• Power plants use cool water from surface/ground water sources nearby to cool steam used to turn a turbine back into water to reuse

  • Steel mills, paper mills, and other manufacturing plants also use cool water to cool down machinery & return warmed water to local surface waters

  • Urban stormwater runoff can also cause thermal pollution due to heat from blacktop/asphalt

• Nuclear power plants require especially large amounts of cool water to cool steam back into water & to cool the reactor core

Cooling Towers

• Cooling towers/ponds are used to cool steam back into water & to hold warmed water before returning to local surface water

  • Already standard in nuclear power plants, but can be optimized to cool water better or hold it longer before returning to nearby surface waters

8.7- Persistent Organic Pollutants (POPs)

POPs

• Persistent (long-lasting) Organic (carbon-based) Pollutants

• Synthetic (human-made) compounds that do not easily breakdown in the environment; accumulate and build-up in water & soil

  • Fat-soluble, meaning they also accumulate and persist in animals’ fat tissue instead of passing through the body (don’t easily dissolve into blood/urine)

    • Can slowly be released from fatty tissue into bloodstream and impact brain & other organs over time (esp. reproductive system)

Examples and Sources of POPs

• Examples

  • DDT (outdated insecticide)

  • PCBs (plastic/paint additive)

  • PBDEs (fire-proofing)

  • BPA (plastic additive)

  • Dioxins (fertilizer production & combustion of waste and biomass)

  • Phthalates (Plastics)

  • Perchlorates (rocket/missile fuel, fireworks)

• Pesticides

  • DDT was widely used as an insecticide before phaseout in most dev. nations

  • Still persists in soils & sediments in aq. ecosystems and builds up in food webs

• Medications (Pharmaceutical compounds)

  • Steroids, reproduct. hormones, antibiotics, that pass through human bodies & into sewage release from treatment plants

  • Persist in streams/rivers & disrupt aq. organisms’ endocrine function

• Dioxins

  • Byproduct of fertilizer production & burning of medical waste, FFs, biomass

  • 90% of human dioxin exposure comes from animal fats (meat, dairy, fish) since dioxins buildup in animal fat tissue

Examples and Transport of POPs

• PCBS

  • Additives in paint and plastics, released into aquatic ecosystems by industrial wastewater

  • Toxic to fish, causing spawning failure and endocrine disruption

  • Reproductive failure & cancer in humans

    • Human exposure comes through animal products

• Perchlorate

  • Given off by rockets, missiles, and fireworks

  • Especially common near military testing sites or rocket launch pads

  • Remain in soil and can leach into groundwater or runoff into surface waters

• POPs travel long distances through wind & water, impacting ecosystems far away

  • Wastewater release from industrial processes, leachate from landfills or improperly buried industrial waste, fertilizer/pesticide production, emissions from burning waste/biomass

  • Enter soil/water, eaten by animals, stored in their fat, eaten by humans or taken in via drinking water

8.9- Solid Waste Disposal

Solid Waste Types and Sources

• Municipal Solid Waste (MSW)

  • Solid waste from cities (households, businesses, schools, etc.

  • Waste “stream” refers to flow of solid waste to recycling centers, landfills, or trash incineration (burning) facilities

  • Aka - trash, litter, garbage, refuse

  • ~ ⅓ paper

  • ~ ⅔ organics (compostable)

• E-Waste

  • Old computers, TVs, phones, tablets

  • Only ~2% of MSW; is considered hazardous waste due to metals like cadmium, lead, mercury, and PBDEs (fireproof chemicals)

  • Can leach endocrine-disrupting chemicals out of landfills if thrown away with regular MSW (should be disposed of at special facilities that recycle parts)

Sanitary Landfills

• APES lingo for “landfills” or where developed nations dispose of trash; different than “dumps” which are just areas where trash is dumped, without the features below

• Clay/plastic bottom liner: layer of clay/plastic on the bottom of a hole in the ground; prevents* pollutants from leaking out into soil/groundwater

• Leachate Collection System: System of tubes/pipes at bottom to collect leachate (water draining through waste & carrying pollutants) for treatment & disposal

• Methane Recovery System: System of tubes/pipes to collect that methane produced by anaerobic decomposition in the landfill

  • Methane can be used to generate electricity or heat buildings

• Clay Cap: Clay-soil mixture used to cover the landfill once it’s full; keeps out animals, keeps in smell, and allows vegetation to regrow

Landfill Contents and Decomposition

• Landfills generally have very low rates of decomposition due to low O2, moisture, and organic material combination

  • Since these 3 factors are rarely present together in landfills, little decomp. occurs and landfills typically remain about the same size as when they were filled

• Things that should NOT be landfilled:

  • Hazardous waste (antifreeze, motor oil, cleaners, electronics, car batteries)

  • Metals like copper & aluminum (should be recycled)

  • Old tires; often left in large piles that hold standing water ideal for mosquito breeding

• Things that SHOULD be landfilled:

  • Cardboard/food wrappers that have too much food residue & can’t be recycled

  • Rubber, plastic films/wraps

  • Styrofoam

    • Food, yard waste, and paper can and do go in landfills, but should be recycled or composted

Landfill Issues

• Landfills have environmental impacts like groundwater contamination and release of GHGs

  • Groundwater can be contaminated with heavy metals (lead, mercury), acids, medications, and bacteria if leachate leaks through lining into soil/groundwater beneath

  • Greenhouse gases (CO2 and CH4 - methane) are released from landfills due to decomposition; both contribute to global warming & climate change

• NIMBY (Not In My Back Yard): idea that communities don’t want landfills near them for several reasons

  • Smell & sight

  • Landfills can attract animals (rats, crows)

  • Groundwater contamination concerns

    • Landfills should be located far from rivers & streams and neighborhoods to avoid H2O cont.

• Landfills are often placed near low-income or minority communities that don’t have the resources or political power to fight against these decisions

Waste Incineration and Ocean Dumping

• Waste can be incinerated (burned) to reduce the volume that needs to be landfilled; since most waste (paper, plastic, food) = hydrogen, carbon, and oxygen, it easily combusts at high temp.

  • Can reduce volume by 90%, but also releases CO2 and air pollutants (PM, SOx, NOx)

    • Bottom ash may contain toxic metals (lead, mercury, cadmium) & is stored in ash ponds, then taken to special landfills

    • Toxic metals can leach out of storage ponds or be released into atmosphere

• Can be burned to generate electricity

• Illegal ocean dumping occurs in some countries with few environmental regulations or lack of enforcement

  • Plastic especially collects into large floating garbage patches in the ocean

  • Can suffocate animals if they ingest (eat) it or entangle them so they can’t fly or swim and may starve

8.10- Waste Reduction

Reduce, Reuse, Recycle

• The Three Rs

  • Reducing consumption is the most sustainable because it decreases natural resources harvesting and the energy inputs to creating, packaging, and shipping goods

    • Ex: Metal/reusable water bottle to reduce plastic use Riding bike or walking to reduce gasoline use

      • Reusing: the next most sustainable b/c it doesn’t require additional energy to create a product

    • Ex: Buying second hand clothes, using old wood pallets for furniture, washing plastic takeout food containers and reusing

• Recycling: processing and converting solid waste material into new products

  • Ex: Glass being turned into glass again (closed-loop), plastic water bottles being turned into fabric for clothes/jackets (open loop)

    • Least sustainable of the three Rs due to the amount of energy it requires to process and convert waste materials

Recycling Pros and Cons

• Pros of Recycling

  • Reduces demand for new materials, especially metals and wood which cause habitat destruction & soil erosion when harvested

    • Reduces energy required to ship raw materials and produce new products (fewer FF comb, less CC)

    • Reduces landfill volume, conserving landfill space & reducing need for more landfills

• Cons of Recycling

  • Recycling is costly and still requires significant energy

    • Cities that offer recycling services need to process, sort, and sell collected materials; prices change rapidly, leading to “recycled” materials often being thrown away

      • When citizens recycle items that shouldn’t be recycled (wrappers with food, styrofoam, etc.) it increases the cost for cities to sort & process

Composting

• Org. matter (food scraps, paper, yard waste) being decomposed under controlled conditions

  • Reduces landfill volume and produces rich organic matter that can enhance water holding capacity, nutrient levels of agricultural or garden soil

    • Produces valuable product to sell (compost)

  • Reduces the amount of methane released by anaerobic decomposition of organic matter in landfills

  • Should be done w/proper mix of “browns” (Carbon) to “greens” (N) ~ 30:1

    • Should also be aerated and mixed to optimize decomposition (bacteria need O2 for decomp.)

• Potential drawbacks include the foul smell that can be produced if not properly rotated & aerated and rodents or other pests that may be attracted

E-Waste

• Waste from electronics (phones, computers, etc.) that often contain heavy metals (lead, merc, cadmium)

  • Can leach these toxic metals into soil & groundwater if disposed of in landfills or open dump

• Can be recycled and reused to create new electronics, but often sent to developing nations for recycling due to health hazards, more strict env. & worker protection laws in developing nations

  • Can be dismantled and sold to countries that extract valuable metals (gold, silver, platinum) from motherboards

  • Often burned or dumped due to less strict env. regulations or lack of enforcement in developing nations

Waste to Energy

• Waste can be incinerated (burned) to reduce the volume & also generate electricity; most waste (paper, plastic, food) = hydrogen, carbon, and oxygen so it easily combusts at high temp.

  • Same process as burning coal, NG, biomass

  • Heat → water → steam → turbine → generator → ⚡

• Methane gas produced by decomposition in landfill can be collected with pipes & burned to generate electricity

  • Heat → water → steam → turbine → generator → ⚡

  • Reduces landfill volume

  • Produces electricity without fracking or mining for FFs

8.11- Sewage Treatment

Water Treatment Process

• Primary Treatment

  • Physical removal of large debris (TP, leaves, plastic, sediment) with a screen or grate

• Secondary Treatment

  • Biological breakdown of organic matter (feces) by bacteria; aerobic process that requires O2

• Tertiary Treatment

  • Ecological or chemical treatments to reduce pollutants left after primary & secondary (N, P, bacteria)

• Disinfectant

  • UV light, ozone, or chlorine is used to kill bacteria or other pathogens, such as e. Coli (considered part of 3)

• Effluent: liquid waste (sewage) discharged into a surface body of water, typically from a wastewater treatment plant

Primary and Secondary Treatment

• Primary

  • Screens or grates filter out large solids (paper, plastic)

  • Grit chamber allows sediment (sand, gravel)

    to settle out & be removed

• Secondary

  • O2 is bubbled into aeration tank filled with bacteria that break down org. matter into CO2 and nutrients like N & P

  • Secondary treatment removes 70% of P and 50% of N DOES NOT remove POPs such as medications or pesticides

• Sludge: inorganic, solid waste that collects at the bottom of tanks in primary and secondary treatment

  • Water is spun/pumped off to concentrate it further

  • Dry, remaining physical waste is collected to be put in landfill, burned, or turned into fertilizer pellets

• After primary & secondary treatment, some plants go directly to disinfectant (UV, ozone, chlorine) & discharge into surface water, while some will use tertiary treatment to remove more nutrients before discharge

Tertiary Treatment

• Tertiary treatment uses chemical filters to remove more of the nitrates & phosphates from secondary treatment discharge

• Critical step because effluent that is discharged into surface waters with elevated nitrate/phosphate levels leads to eutrophication

• Expensive and not always used

Sewage Treatment Issues

• Combined sewage and stormwater runoff systems can cause wastewater treatment plants to flood during heavy rains, releasing raw sewage into surface waters

• Beneficial b/c it treats stormwater runoff normally, but causes overflow during heavy rains

• Raw sewage release contaminates surface waters with:

  • E. coli

  • Ammonia

  • Nitrates

  • Phosphates

  • Endocrine disruptors (medications)

• Even treated wastewater effluent released into surface water often has elevated N/P levels and endocrine disruptors (medications passed through the body)

8.12 and 8.13- LD50 and Dose-Response Curve

Dose-Response Studies and LD50

• Studies that expose an organism to different doses of concentrations of a chemical to measure the response (effect) of the organism

• Independent variable = concentration of the chemical (added to food, water, or air)

• Dependent variable = response measured in org. (usually death or impairment)

• LD50 refers to the dose or concentration of the chemical that kills 50% of the population being studied (ex: arsenic LD50 in mice = 13 mg/kg)

  • LD50 data are usually expressed as:

    • mass (g, mg)/body unit mass (kg)

    • ppm - parts per million (in air)

    • mass/volume (in water of blood)

Dose-Response Curve

• The data from a dose-response study, graphed with percent mortality or other effect on the y-axis and dose concentration of chemical on x-axis

• Lowest dose where an effect (death, paralysis, cancer) starts to occur is called the threshold or toxicity threshold

• Dose-response curves are usually “S-shaped” - low mortality at low doses, rapid increase in mortality as dose increases, level off near 100% mortality at high dosage

ED50 and Other Dose Responses

• ED50 refers to the dose concentration of a toxin or chemical that causes a non-lethal effect (infertility, paralysis, cancer, etc.) in 50% of the population being tested

  • Ex: the concentration of atrazine in water that causes 50% of frogs to become infertile

  • Same general “s-shape” as LD50 dose-response curve, but at lower dose concentrations

Dose-Response Data and Human Health

• Dose-response studies for toxic chemicals are not done on humans; data from other mammals (mice, rats) are used to simulate human toxicity

• To determine maximum allowable levels for humans, we generally divide LD50 or ED50 dose concentration by 1,000 for extreme caution

• Acute vs. Chronic studies: Most dose-response studies are considered acute, since they usually only measure effects over a short period of time; they’re also isolated to a lab, so they don’t measure ecological effects of organisms dying (trophic cascades)

  • Chronic studies are longer-term and follow developmental impacts

    • Ex: study of fish from hatchlings to adults to study sexual maturation

8.14 Pollution and Human Health

Routes of Exposure & Synergism

• It’s difficult to establish exactly how toxic different pollutants are to humans because we have so many routes of exposure to so many different pollutants, that studying the effects of just one pollutant is difficult.

• Routes of Exposure

  • Ways that a pollutant enters the human body

    • Lead → water pipes & paint chips

    • Mercury → seafood (tuna)

    • CO → indoor biomass comb.

    • PM → pollen, dust, etc.

    • Arsenic → rice, groundwater

• Synergism

  • The interaction of two or more substances to cause an effect greater than each of them individually

    • Ex: Asthma caused by PM from coal PPs and COVID-19 damaging lungs

    • Carcinogenic effect of asbestos combined with lung damage from smoking

  • Synergisms make it especially hard to pinpoint the exact effects of one specific pollutant on humans

Dysentery

• ⛰Bacterial infection caused by food or water being contaminated with feces (often from sewage release into rivers & streams used for drinking water)

• Causes intestinal swelling and can result in blood in feces

  • Results in severe dehydration due to diarrhea (fluid loss)

  • Kills 1.1 million people annually, mostly in developing countries with poor sanitation and limited access to water filtration

• Can be treated with antibiotics that kill the bacteria causing the infection and access to treated/filtered water that can rehydrate

Mesothelioma (asbestos)

• A type of cancerous tumor caused by exposure to asbestos, primarily affecting the lining (epithelium) of the respiratory tract, heart, or abdominal cavity

• Asbestos exposure comes primarily from old insulation materials used in attics, ceiling and flooring boards; when the insulation becomes physically disturbed, asbestos particles are released into the air & inhaled

• Removal of asbestos-containing insulation material should be done by professionals with proper training and equipment that protects them from inhaling the asbestos

  • The area where asbestos is removed from should be sealed off from other areas in the building and well-ventilated during the removal process

  • Insulation without asbestos should be used to replace it

Tropospheric Ozone (O3)

• Worsens respiratory conditions like asthma, emphysema, bronchitis, COPD

• Limits overall lung function

  • Irritates muscles or resp. tract causing constriction of airways & shortness of breath

  • Irritates eyes

  • Sources: photochemical breakdown of NO2 (car exhaust, coal & NG combustion)

• ONLY HARMFUL IN TROPOSPHERE (beneficial in the stratosphere)

8.15 Pathogens and Infectious Diseases

Pathogens and Vectors

• Pathogen

  • A living organism (virus, bacteria, fungus, protist, worm) that causes an infectious disease

    • Infectious diseases are capable of being spread or transmitted (HIV, ebola, Covid-19); noninfectious diseases are not transmissible (heart disease, asthma, cancer, diabetes)

    • Pathogens adapt and evolve to take advantage of humans as hosts for their reproduction and spread (Covid-19 is a SARS-associated coronavirus that evolved to become especially effective at surviving and reproducing in humans)

  • Vectors

    • A living organism (rat, mosquito) that carry and transmit infectious pathogens to other organisms

      • Climate change is shifting equatorial climate zones north and south away from the equator; this brings warmer temperatures to subtropical and temperate regions

      • Warmer temperatures allow pathogens and their vectors (mosquitos) to spread north & south to parts of the world previously too cold

        • Many pathogenic bacteria and viruses survive and replicate better in warmer weather

Infectious Disease and Development

• Less developed, poorer countries typically have higher rates of infectious disease

• Less sanitary waste disposal; pathogens can reproduce in open waste areas where children may play or animals may scavenge & pass to humans

• Less access to healthcare facilities and antibiotic medications to treat infectious diseases cause by bacteria & other pathogens

• Lack of treatment/filtration for drinking water & sewage treatment exposes people to bacterial and viral pathogens in water, often from human waste

• Tropical climates & more open-air living can expose people to vectors like mosquitoes; less money for vector eradication (spraying mosquito breeding grounds)

Plague

• Bacterial (pathogen) infection transmitted by fleas (vector) that attach to mice & rats (vectors as well)

  • Transmitted by flea bite, rodent contact or contaminated human fluids

  • Aka “bubonic” or “black” plague; modern antibiotics are highly effective against it, but some isolated instances still occur

Tuberculosis (TB)

• Bacterial (pathogen) infection that targets the lungs

  • Transmitted by breathing bacteria from body fluids (resp. droplets) of an infected person, which can linger in air for hours

  • Causes night sweats, fever, coughing blood; treatable in developed nations with access to powerful antibiotics

  • Leading cause of death by disease in the developing world ~ 9 million cases per year and 2 million deaths (for comparison ~ 2.8 million global deaths from Covid-19)

Malaria

• parasitic protist (pathogen) infection caused by bite from infected mosquitoes (vector)

  • Most common in sub-Saharan Africa (& other tropical regions of Middle East, Asia, South & Central America; recurring flu-like symptoms; kills mostly children under 5

  • Can be combated with insecticide spraying that kills mosquitoes; US eradicated in 1951

West Nile

• Virus (pathogen) infection caused by bite from infected mosquitoes (vector)

  • Birds are the main host, but the virus can be transmitted to humans by mosquitoes that bite infected birds and then bite humans

  • Causes brain inflammation, which can be fatal

Zika Virus

• Virus (pathogen) infection caused by bite from infected mosquitoes (vector) & sexual contact

  • Causes babies to be born with abnormally small heads and damaged brains; can be passed from mother to infant

  • No known treatment currently, so prevention is focused on eliminating mosquito populations

Severe Acute Respiratory Syndrome (SARS)

• Coronavirus (pathogen) infection caused by respiratory droplets from infected person

  • Primarily transmitted by touching or inhaling fluids from an infected person

  • Causes a form of pneumonia

  • Initial outbreak was in Southeast Asia

  • SARS-CoV-2 is the virus that causes the disease COVID-19

Middle East Respiratory Syndrome (MERS)

• Virus (pathogen) respiratory infection transmitted from animals to humans

  • Originated on Arabian peninsula

Cholera

• Bacterial (pathogen) infection caused by drinking infected water

  • Vomiting, muscle cramps and diarrhea; can cause severe dehydration

  • Can be introduced by water contaminated with human feces or undercooked seafood