BIO Topic 2: Environmental Toxicology

Why study environmental toxicology? What is the connection to human health and environmental health?

• Understanding how environmental toxins may affect humans and other organisms 

• Become familiarity with main types of toxins 

• Gain tools for determining real level of concern about a toxin 

• Explain why there are often tradeoffs in the use/disuse of toxins

what does toxic mean?

contains or is a poisonous material, especially when capable of causing death or serious debilitation of an organism

what is toxicology?

the study of toxic substances and their effects

why is it incorrect to say that all chemicals are bad?

Because chemical just means “substance” made up of atoms. Without chemicals like hydrogen and oxygen, there would be no way to make water 

what is a carcinogen?

a substance that causes cancer

• Cancer: uncontrolled growth in cell division 

• Often causes DNA mutation or promotes cell growth 

• Ex: things in cigarettes, alcohol, uv radiation

what is a mutagen?

 a substance that causes changes in genetic code (DNA mutations)

• Ex: uv light (it can damage the structure of a DNA strand, causing mutations when the DNA is copied), radiation, PAHs

• Many mutagens are carcinogens 

what is a teratogen?

a substance that causes developmental deformities (think of birth deformities in babies)

• Ex: alcohol, lead, warfarin (a blood thinner) 

• Critical window: the time where the teratogen has the most effect

what is a neurotoxin?

a substance that affects the function or development of of nerve cells 

• Ex: mercury, lead, pesticides, botox 

what is an endocrine disruptor?

a chemical that affects endocrine signals (hormones) by chemically mimicking a hormone, interfering with a hormone signal receptors, and or changing the amount of hormones secreted 

• Ex: PCBs, pharmaceuticals

what is a pesticide?

Any substance intended for preventing, destroying, repelling, or mitigating any pests.  

what is environmental toxicology?

the study of the health effects of environmental contaminants on organisms or ecosystem

what is a toxin/toxicant?

 a toxic substance. Toxin often refers to a naturally occurring substance and toxicant often refers to something manufactured by humans

what is a contaminant?

hazardous substances, pollutants, pollution, and chemicals that are often found in the environment in amounts higher than what would be there naturally 

• Can be exposed through a variety of residential, commercial, and industrial sources 

• Biological harmful contaminants: mold and toxic algae bloom 

what is an acute affect?

an effect that occurs rapidly after exposure to a large amount of that substance

what is a chronic effect?

results from exposure to small amounts of a substance over a long period of time

what is an allergen?

substances in our environment to which causes an allergic reaction

what is a Letha dose?

in humans have been determined for many substances from information gathered from records of homicides, accidental poisonings, and testing on animals

what is a lethal dose-50% (LD-50)?

a does that is lethal to 50% of a population of test animals 

• Determination of LD-50 is required for new synthetic chemicals in order to give a measure of their toxicity 

• The lower it is, the more toxic the compound

what is an effective dose-50% (ED-50)?

 A dose that causes 50% of a population to exhibit any significant response

• Some toxins have a threshold amount below which there is no apparent effect on the exposed population 

what is a forever chemical (e.g. PFAS)?

substances that are difficult to break down

what is the ozone?

a molecule in which three atoms of oxygen are bonded together. Ozone is relatively unstable and releases its third oxygen atom readily so it oxidizes and burns things more readily than oxygen gas 

• The oxygen gas in the air we breathe has two oxygen atoms bonded together

what is mercury?

 naturally occurring metal, a useful chemical in some products and a potential health risk

• Children born from mothers who are exposed to mercury commonal have motor difficulties, sensory problems, and cognitive deficits   

what is thalidomide?

a sedative drug that was found to cause congenital malformation, especially of the limbs, in children whose mothers took it during early pregnancy to treat morning sickness. It was withdrawn from use in the early 1960s but may now be prescribed, under extremely strict guidelines, to treat certain diseases.

what is arsenic?

a naturally occurring element that is normally present throughout our environment in water, soil, dust, air, and food 

• Levels of arsenic can regionally vary due to farming, industrial activity, and natural geological processes

what is bisphenol A (BPA)?

 a chemical synthesized in large quantities for use primarily in the production of polycarbonate plastics and epoxy resins 

what is lead?

 a metal that occurs naturally in the rocks and soil of the earth’s crust. It is also produced from burning fossil fuels (coal, gasoline, oil, and natural gas), mining, and manufacturing

• Reasonably anticipated to be a human carcinogen 

• Most sensitive body part to be exposed to lead is the central nervous system

what is radiation?

energy given off by atoms and is all around from natural sources like soil, rocks, and the sun

what is radon?

radioactive gas that is naturally occurring, colorless, and odorless. It comes from natural decay of uranium and thorium found in all soils 

• Leading cause of lung cancer among nonsmokers  

what is biomagnification?

 the increasing concentration of persistent, toxic substances in organisms at each successive trophic level

• These are substances that are lipid soluble and are stored in the fat reserves of each organism

what is the precautionary principle?

enables decision-making to adopt precautionary measures when scientific evidence about an environmental or human hazard is uncertain and the stakes are high

what was the US Clean Air Act?

established funding for the study and cleanup of air pollution 

• Much stronger act passed in 1970: Clean Air Act 1970

what is primary air pollutant?

a pollutant that is put directly into the air by human activity. 

Ex: soot from smoke

what is secondary air pollutant?

 when a primary pollutant comes into contact with other primary pollutants or with naturally occurring substances 

Ex: nitrogen oxides

what is smog?

a fog made heavier and darker by smoke and chemical fumes

what is acid rain?

when higher than normal amounts of nitric and sulfuric acids occur in the atmosphere

• Precipitation with a pH below 5.6 

• Includes both wet (rainfall, snow, fog) and dry (particulates) deposition 

• Results from both natural (volcanoes and decaying vegetation) and manmade sources (sulfur dioxide and nitrogen oxides)

what is air particulate matter (PM)?

a complex mixture of small solid particles and liquid droplets in the air

what is persistent organic pollutants?

are a group of organic chemicals, such as DDT, that have been widely used as pesticides or industrial chemicals and released into the environment by human activity.

what is DDT?

Dichlorodiphenyltrichloroethane
• Used primarily as an insecticide
• Mechanism of toxicity to insects:
Causes unregulated neuron firing
(affects neuron sodium levels) leading
to spasms and death.
• Acute toxicity to humans is low.

what is glyphosate?

Kills plants and bacteria, by disrupting a chemical pathway unique to these organisms

what is the Ozone Hole?

not really a “hole” but rather an area where the thickness of the ozone layer is greatly reduced. Has stopped growing since the Montreal Protocol

why is carbon monoxide a concern?

because its presence is a hazard as it blocks oxygen uptake by cells from the blood

In which organism would you expect the effects of biomagnification to be most pronounced? 

birds that eat fish

Which statement best describes the Precautionary Principle?

Regulatory agencies do not need to wait until the science regarding a chemical is well understood.  If there is evidence that there is a problem with a chemical, protective regulatory measures should be taken.

Which is a potential downside of the precautionary principle pointed out by the Goldstein article?

The precautionary principle can be used as an excuse to erect unfair trade barriers.

What does the term "persistent" refer to in the context of Persistent Organic Pollutants (POPs)?

Their resistance to breakdown, lasting for long time periods in the environment

What does the term "Bioaccumulative" refer to in the context of Persistent Organic Pollutants (POPs)?

can accumulate in animals and humans, usually in fatty tissues and largely from the food they consume. As these compounds move up the food chain, they concentrate to levels that could be thousands of times higher than acceptable limits

What does the term "Toxic" refer to in the context of Persistent Organic Pollutants (POPs)?

POPs can cause a wide range of health effects in humans, wildlife, and fish. The deliberate production and use of most POPs have been banned around the world, with some exemptions made for human health considerations