Envi Sci (Chapters 14 + 22): Toxic Chemicals & Waste Review

1. Who wrote Silent Spring and what was its significance?

2. How did Chemical Companies react to the book?

3. How did the Government react to the book?

1. Rachel Carson showed DDT’s risks to people, wildlife, and ecosystems by gathering data and presenting scientific studies and medical cases

2. They challenged the book and attacked Carson’s scientific and personal reputation

3. The government banned it in the US, but it was still made and exported to countries who wanted to control disease (like Malaria)

Toxic Substance Type: Carcinogen

substances that cause cancer

• cells grow uncontrollably, damaging the body

• prevalence of environmentally induced cancer has been underestimated

• Hard to identify because of the long time between exposure and onset of cancer and because not everyone exposed gets cancer

Toxic Substance Type: Mutagen

substances that cause DNA mutations

• most mutations have no effect, but some can cause cancer

• if they occur in sperm or eggs, they can impact offspring

Toxic Substance Type: Teratogen

chemical that causes birth defects in embryos (unborn)

• Thalidomide was used to help women sleep and reduce nausea when pregnant, but ended up causing birth defects and was banned in the 1960s

Toxic Substance: Neurotoxin

toxicants that assault the nervous system

• animal venoms, heavy metals (lead + mercury), pesticides, and chemical weapons

• results in slurred speech, loss of muscle control, sudden fits of laughter, and death

Toxic Substance: Allergens

toxicants that over-activate the immune system

• cause an immune response when one is not needed

• increase in asthma in recent years may be due to increased prevalence of allergenic chemicals

• not universally considered toxicants since they only affect some people and not others

Toxic Substance: Pathway Inhibitors

toxicants that interrupt vital biochemical processes by blocking one or more steps in pathway

• the herbicide atrazine blocks steps in photosynthesis

• Cyanide stops important steps in generation of energy for mitochondria, so cells die

Toxic Substance: Endocrine Disruptors

toxicants that affect the endocrine (hormone) system (aka chemical messenger system)

• some are hormone-disruptors that break down hormones at an accelerated rate

• some “mimic” real hormones and interact with receptor molecules in place of the real hormone

Why is it hard to identify endocrine disruptors? Carcinogens?

• Endocrine disruptors: oftentimes fall under the category of other toxic substance types and are left undetected/unidentified. Unconventional dose-response curves are hard to study or use to set safety standards

• Carcinogens: hard to identify because not everyone exposed to them ends up getting cancer, and those who do, experience it later on so it’s hard to tell if the cancer is a direct result of the toxic carcinogen.

1. What is BPA?

2. Why is BPA bad?

1. Bisphenol A: an industrial chemical found in polycarbonate plastics and epoxy resins

2. BPA is used to make hard plastics found in hundreds of products such as cans, utensils, baby bottles, laptops, and toys, and therefore leaches into food, water, air, and bodies. Negative effects such as cancer, nerve damage, and miscarriages occur at extremely low doses. BPA mimics estrogen (female hormone). Even though some have found no reason to be concerned, public and scientific opinion propose regulating BPA especially in baby bottles (babies are pre-polluted).

Pesticide Drift

airborne transport of pesticides to land near agricultural fields

• Central Valley, CA is agriculturally active and uses a lot of pesticides to grow crops. But pesticide spray drifts to the mountains of Sierra Nevada where they cause a decline in 4 different types of frog species

Which regulated pesticides: FDA or EPA?

EPA: regulated pesticides and chemicals not covered by other laws (FDA monitors food, food additives, cosmetics, drugs, and medical devices)

1. What is the Toxic Substance Control Act & what does it regulate?

2. What do health advocates think of the TSCA?

1. allows the EPA to monitor thousands of chemicals made in or imported into the US & allows the EPA to ban substances that pose excessive risk.

2. they think it’s too weak (only 5 of 83,000 chemicals have been restricted & only 10% of chemicals have been tested for toxicity)

What was the goal of the Stockholm Convention and what did it accomplish?

aims to end the use and release of the 12 POPs + set guidelines for phasing out the “dirty dozen” (12 most dangerous Persistent Organic Pollutants) + encouraged transition to safer alternatives

• because contaminants (chemicals) often cross international borders, an international treaty seemed the best way to deal with this transboundary pollution

Case Study Overview: Pesticides and Child Development in Mexico’s Yaqui Valley

Elizabeth Guillette wanted to examine the effects of pesticides on young children by applying new methods of observation. She went to Yaqui Valley in Mexico, where she observed child development of indigenous Yaqui peoples. Synthetic pesticides arrived in the area in the ‘40s. As farmers, some Yaqui in the valley sprayed their crops with pesticides to increase their yields, but the farmers in surrounding foothills only used traditional farming methods on their crops. Pesticides were found in the breast milk of mothers and blood of umbilical cords in babies. Guillette studied 50 preschoolers who underwent an half-hour exam, and physical and mental tests. Children were measured for their height and weight. It was found that Valley children lacked the coordination, physical endurance, long-term memory, and fine motor skills found in Foothill children.

Synergistic Effects

interactive impacts that are greater than the sum of their constituent’s effects

• New impacts may arise from mixing toxicants

• DDE may cause or inhibit sex reversal, depending on the presence of other chemicals

• interactive effects of most chemicals are unknown

Why are children and fetuses more susceptible to higher-sensitivity responses when introduced to toxic chemicals?

Their organs are still developing

Explain PBDE and the European Union’s effect on its prevalence

Polybrominated diphenyl ethers are a group of chemicals with fire-retardant properties used in computers, televisions, plastics, and furniture. They persist and accumulate in living tissue, mimic hormones, and affect the brain and nervous system development by causing cancer. Concentrations are rising in breast milk. The Europian Union banned them in Europe, leading to decreased concentrations in breast milk. Ths US has not addressed the issue.

What can endocrine disruptors do to humans/animals?

create reproductive abnormalities and effects development, immune functions, and nervous systems

• Even though evidence of these negative effects are present in humans, the are strongest in non-human animals

Radon Gas

• a highly toxic, radioactive gas that is colorless and undetectable

• often builds up in basements poorly-ventilated

• seeps through the ground in areas with certain types of bedrock

• leading cause of lung cancer

1. bioaccumulation + example

2. biomagnification + example

1. process of toxicants building up in animal tissues to greater concentration than in the environment (methylmercury being stored in muscle tissue)

2. process that occurs when concentrations of toxicants become magnified in higher levels of the food chain (falcon + bald eagle populations decline bc DDT increases higher in food chain)

1. Acute Exposure

2. Chronic Exposure

1. high exposure to a hazard for short periods of time

   1. easy to recognize

   2. stems from discrete events: ingestion, oil spills, nuclear accident, etc.

2. low exposure for long periods of time

   1. more common but harder to detect and diagnose

   2. affects organs gradually,: lung cancer, liver damage

   3. cause and effect may not be easily apparent due to time between onset of exposure and symptoms

What kind of toxic substance is Mercury pollution? Where can methylmercury be found?

Neurotoxin; fish absorb methylmercury as it passes over their gills because mercury is tightly bound to proteins in all fish tissue (bioaccumulation occurs)

3 Dose Response Curve Types

1. Linear: The percentage of animals killed rises steadily with the dosage given

2. Linear-Threshold: Linear curve with a threshold dose, below which doses have no effect

3. Unconventional: U-shaped, J-shaped, or inverted curves as seen in endocrine disruptors

LD50

lethal dose for 50% of individuals

1. What is the largest source of unregulated hazardous waste?

1. What is the largest source of regulated hazardous waste?

1. Households

2. Industries

How are sanitary landfills developed?

Located away from wetlands & earthquake-prone faults 20 ft above the water table, waste is buried in the ground or piled into a large, engineered mound that decomposes and compresses under its own weight to make more space while also preventing contamination and health risks. Soil is layered to reduce odor, speed decomposition, and reduce infestation by pests. Borrom and sides are lined with plastic and clay.

How do sanitary landfills prevent groundwater contamination?

Liquid from trash is dissolved by rainwater and collected in a series of pipes and treated, but it can escape of the liner is punctured. Once closed, it must be capped and maintained, and groundwater must be monitored for contamination.

E-waste: recycling & production facts

• ¼ of all devices in America are made from recycled material

• 67% of the 300 million devices discarded/yr in America are still in working order

• Hazardous waste, but not deemed as waste

• contain heavy metals and toxic flame retardants

• recycling keeps these out of landfills

• recycling E-waste requires dismantling the devices - there are health concerns for those who do the recycling

1. Love Canal

2. Times Beach

1. families evacuated after toxic chemicals buried by a company and the city in past decades rose to the surface. Contaminated homes and an elementary school in Niagara Falls, NY.

2. evacuated and its buildings demolished after being contaminated in the ‘70s by dioxin from waste oil sprayed on its roads

Resource Conservation and Recovery Act

regulates municipal landfills & establishes how states must manage waste

4 Types of Hazardous Waste

1. Ignitable: easily catches on fire (natural gas, alcohol)

2. Corrosive: corrodes metals in storage tanks or equipment (strong acids, bases)

3. Reactive: chemically unstable and readily reacts with other compounds, often explosively or by producing noxious fumes

4. Toxic: harms human health when inhaled, ingested, or touched to human skin (pesticides, heavy metals)

Brownfields

lands whose reuse or development is complicated by the presence of hazardous materials

What Act is Superfund from? What year was it made?

The Comprehensive Environmental Response Compensation and Liability Act put together Superfund in 1980 to clean up US sites polluted with hazardous waste