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Lecture 20

11:375:101 Lecture Notes - Lecture 20: Tissue Culture, Dementia, Malnutrition

Environmental Sciences
Course Code
Craig Phelps

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Health and Toxicology II
Chapter 17: Environmental HAzards and Human Health
17-3: What Types of Chemicals Hazards Do We Face?
There is growing concern about chemicals in the environment that can cause
cancers and birth defects, and disrupt the human immune nervous, and endocrine
Some Chemicals Can Cause Cancers, Mutations, and Birth Defects
Toxic Chemicals
Chemicals, types of radiation, or certain viruses the cause
or promote cancer
Chemicals or radiation that cause mutations or increase
their frequency
Chemicals that cause harm or birth defects to a fetus or
Case Study: PCBs Are Everywhere - A Legacy from the Past
Class of chlorine-containing compounds
Very stable
Break down slowly in the environment
Travel long distances in the air
Fat soluble
Ends up in food chains and webs
Banned, but found everywhere
Some Chemicals May Affect Our Immune and Nervous Systems
Some natural and synthetic chemicals in the environment can weaken and
Immune system
Some chemicals weaken the immune system
Nervous system
Neurotoxins - PCBs, arsenic, lead, some pesticides
Example - Methylmercury
Some Chemical Affect the Human Endocrine System
Endocrine system
Glands that release hormones that regulate bodily systems and
control sexual reproduction, growth, development, learning,
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Hormonally active agents have similar shapes and bind to hormone
Hormone mimics
Hormone blockers
17-4: How Can We Evaluate Chemical Hazards?
Scientists use live laboratory animals, case reports of poisoning, and
epidemiological studies to estimate the toxicity of chemicals, but these methods
have limitations
Many health scientists call for much greater emphasis on pollution prevention to
reduce our exposure to potentially harmful chemical
Toxicology - study of harmful effects
Toxicity - a measure of a substance's ability to cause harm
Dose - the amount of a substance that a person has been exposed to
Response - damage resulting from exposure
Acute effect - immediate or rapid
Chronic effect - permanent or long-lasting
Many Factors Determine the Harmful Health Effects Of Chemicals
Genetic makeup
Case Study: Protecting Children from Toxic Chemicals
Analysis of umbilical cord blood
180 chemicals found that cause cancers in humans or animals
Infants and children more susceptible
Less well-developed immune systems and body detoxification
Risk unknown
Dose-Response ANalysis
Measure responses at several different doses
Dose-response curve - median lethal dose (LD50)
Nonthreshold dose-response model
Threshold dose-response model
Scientists Use Live Lab Animals and Non-Animal Tests to Estimate Toxicity
Mice and rats
Systems are similar to humans
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