Lecture 21 | Toxicology

Toxins, Disease, Pollution vs Contamination, Point Source & Non-Point Source, Common Pollutants, Dose Response Curves, Acute vs Chronic Toxicity, Risk Assessments

Case Study | Why can’t we completely avoid chemical exposure?

we live in a chemical soup

Toxin

poisonous to living things

Toxicology

study toxins in the environment and their effects on living things

What are the two perspectives of toxicology?

how toxins behave in their environment, what they do to the organism

How are toxins synergistic?

effects are worse when combined with something else

Disease

impairment of an individual’s ability to function

Provide examples of a serious vs a mild disease:

cancer vs headache

Why is disease sometimes hard to identify?

what impairs someone depends on the individual

Why is it impossible to make it through life without encountering any disease?

disease is everywhere

Pollution

unwanted change in environment from introducing unwanted materials

Contamination

when pollution renders an environment unfit for intended use

You can _______ an environment without ________ it

pollute, contaminating

Describe river pollution versus river contamination:

dumping waste is pollution, when pollution kills the fish it’s contamination

Pollution can be _____ and ______

natural, manmade

Describe an example of natural pollution:

volcanic lake releasing co2 that suffocated a town

Point-Source Pollution

comes from 1 specific location, easy to identify

Non-Point Source Pollution

comes from many sources, cannot identify 1 specific source

What are some examples of point source pollution?

smoke from smokestack, waste from water pipe

What are some examples of non-point source pollution?

nutrient polluted pond, sedimented river, air pollution in the city

What is the difference between regulating point source and non-point source pollution?

point source is easy to point blame, non-point is harder because little bits add up

What are the 4 types of pollutants?

ihop: infectious agents, heavy metals, organic pollutants, persistent organic pollutants

Infectious Agents

cause illnesses, biological pollutant, common in water

Heavy Metals

rcra 8, toxic in low concentrations, don’t break down

RCRA 8

abcclmss: arsenic, barium, cadmium, chromium, lead, mercury, selenium, silver

Organic Pollutants

btex, pcbs, build up in concentration, creation of new chemicals

BTEX

benzene, toluene, ethyle benzene, xylene, soluble components of gasoline

Persistent Organic Pollutants (POPs)

DDT, dioxins, last forever in environments, treated differently than regular organics, effective pesticides

What are some less common environmental pollutants?

nuclear radiation, thermal pollution, particulate matter, electromagnetic fields, noise pollution, light pollution

How do asbestos and particulate matter affect the environment?

small particles & fibers, lung issues

How can light pollution affect the environment?

disrupts species that use light as a sense of direction

What does “the dose makes the poison” mean?

anything can be poisonous in the wrong amount

What makes everything have the potential to be dangerous?

concentration, too much or too little

Dose-Response Curve

indicates how beneficial or harmful a substance is based on concentration

Describe the progression of the dose-response curve:

too little is harmful, increasing benefits, maximum benefit plateau, decreasing benefit, too much is harmful

How can we determine how much of a substance is safe for humans?

dose-response curves

LD-50

how much of a toxin it takes to kill 50% of a given population

What is NOT used to determine safety levels of chemicals in the environment?

ld-50s

What are LD-50s used for?

compare toxicity of chemicals

New chemicals must undergo ____ and ______ to determine their LD-50

research, development

A _____ LD-50 is safer

higher

Acute Exposure

exposed to high concentrations over short time frame

Chronic Exposure

exposed to low concentrations over long time

The effects of acute exposure and chronic exposure differ for the same chemical. Describe how acute versus chronic exposure differs for chromium:

acute lung corrosion, chronic cancer and decrease in fertility

Risk Assessment

determine the potential adverse health effects of pollutants & toxins

What are the steps of a risk-assessment?

ider: identify hazard, dose-response assessment, exposure assessment, risk characterization

What is the purpose of each risk-assessment step?

ider: determine exposure pathways, what concentration the substance is toxic, how many people exposed, all potential outcomes