SG 5 Flashcards
Describe the field of toxicology and its subfield environmental toxicology.
“Dose makes the poison”
Recognize the basic principles of toxicology. Does the dose always make the poison? Explain your answer.
No, EDC we can see harmful effects at a low dose but not at a higher dose. Effects can be subtle.
Be able to list and describe factors influencing the toxicity of a chemical.
Factors Influencing Toxicity
Chemical and physical properties
-e.g., structure, solubility…
Dose amount
-Amount of an agent that comes into contact with a living organism or a part of a living organism
Dose frequency - how often exposure occurs
-e.g., daily, weekly, 5 days out of 7, etc…
Dose duration - how long or the total period of time exposure occurs
-e.g., a week, a month, a year, a lifetime
Route of exposure
-Ingestion, inhalation, dermal (skin contact)
Fate in the body
-Absorption, distribution, metabolism, storage, excretion
Individual characteristics - age, sex, body weight, genetics
Health status - preexisting health problems,
physical stresses
Interactions with other chemicals
-e.g., additive, synergistic or antagonistic
Describe some of the vital functions of the endocrine system. What are hormones?
Stimulate growth and development, sexual maturity, appetite. Main system in the body that uses hormones to communicate to the organs which are chemical messengers throughout the body.
What is an endocrine disrupting chemical or EDC? How can EDCs affect the function of hormones?
Endocrine disruptors are toxins that interfere with the endocrine system which are chemical messengers or hormones that travel through the bloodstream. It can affect hormones by “mimicking” hormones to trick your brain and some EDC’s block the effects of hormones.
Be able to name and describe the adverse effects of several widespread EDCs. Give examples of the products or processes in which they are or have been used.
Some effects of EDC’s are birth defects, breast cancers, reduced sperm count, and other adverse effects. they have been linked to phthalates (perfumes), also widely used in children’s toys.
When did widespread synthetic chemical production begin to take place? What have been its consequences in terms of the extent of exposure?
It began with DDT which was a pesticide that was sprayed so liberally everywhere to protect crops from insects. Rachel Carson exposed risks in 1962 with her book ‘Silent Spring”
the extent of the exposure has lead to the thinning of birds egg shells and when the mother roosts she breaks the eggs, we have seen other consequences.
How do toxicants travel through the environment and describe the extent to which they are found?
They can travel via the wind, it can take them long distances. It can also move through surface water when spraying crops as well as run-off.
What influences the breakdown or degradation of chemicals in the environment?
Moisture, temperature, sun exposure, and microbes. But it can take decades to breakdown some of these chemicals. Most just break down into a simpler less toxic form.
What are persistent organic pollutants or POPs? Give some examples.
POPs are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. Because of their persistence, POPs bioaccumulate with potential significant impacts on human health and the environment.
DDT and PCBs.
Describe and be able to distinguish between bioaccumulation and biomagnification.
Bioaccumulation is Fat-soluble chemicals are stored and accumulated ex: DDT and PCBs
When bioaccumulated chemicals are passed up the food web and their concentration magnifies that is called Biomagnification.
Describe how the effects of toxic substances are studied. Be able to distinguish between natural versus manipulated (controlled) experiments. Why are manipulative experiments not generally used in human toxicology?
Observational seen in nature.
Controlled is exposing something to see the results.
Lab rats
human cells
What is epidemiology? What are some advantages and disadvantages of this type of research?
is the study of patterns of illness including rates of occurrence, distribution, and control in human populations.
Advantages: Realistic and all real-life factors are included.
Disadvantages: Statistical correlations and does not prove causation.
Understand dose response analysis and be able to interpret dose response curves. How are the results from dose response analyses used?
Dose response analysis : determining toxicity of a substance by measuring the response of different doses to the substance.
Dose response curve : we do this to know dose response relationship and establishes causality.
Backwards J-shaped, U-shaped and
inverted dose response curves seen with endocrine disruptors
Describe the types of studies conducted by toxicologists. Distinguish between acute and chronic exposure studies.
Acute toxicity describes the adverse effects of a substance that result either from a single exposure.
Chronic is long term exposure.
