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Chapter 14: Environmental Health and Toxicology - Coggle Diagram
Chapter 14: Environmental Health and Toxicology
Environmental Health
Field that assesses environmental factors that influence human health and quality of life Including natural and human-caused factors
Many environmental health hazards exist in the world around us
4 Types of Environmental Hazards
Physical
Exposure to ultraviolet (UV) radiation from sunlight
Earthquakes, volcanoes, fires, floods, droughts
We can’t prevent them, but we can prepare for them
When we remove trees from slopes, we make it easier for landslides to occur, and when we try to control the flow of rivers, we increase the risk of flooding. These actions make us more vulnerable to natural hazards.
We can reduce risk with better environmental choices
Chemical
Synthetic chemicals such as pharmaceuticals, disinfectants, pesticides
Harmful natural chemicals (e.g., venom) also exist and chemicals that we take from nature and process
Biological
Result from ecological interactions
Viruses, bacteria, and other pathogens
Infectious disease = disease occurring when species parasitize humans, fulfilling their ecological roles
Vector = an organism that transfers a pathogen
We can’t avoid risk, but we can reduce infection
Cultural :
Result from where we live, our socioeconomic status, our occupation, our behavioral choices
Smoking, drug use, diet and nutrition, crime, mode of transportation—some we control, others we can not
Health factors (e.g., living near toxic waste) are often correlated with poverty
Toxicology: The Science of Poisons
Poisons are called toxicants
toxicants that come from animals (venoms) are called toxins
Venom vs Poison
Poisons are
ingested
or absorbed through skin- plants, some animals
Venoms
are
injected
- fangs, stinger
Environmental toxicology
focuses on effects of chemical poisons released into the environment
Health effects on humans
Ecotoxicology
Effects on animals and plants and Effects on ecosystems
Toxicity and Dose
The dose makes the poison” At some very low dose even the most potent toxicant is without effect , At very high doses things that are ‘safe’ become toxic
Increasing dose = Increasing effect
Concentration is the amount of a toxicant that an organism comes in contact with
Usually expressed as the amount of toxicant per unit of a medium, such as air or water
Dose-
The dose is the amount of a toxicant taken into the body
Dose is usually expressed as the amount of toxicant per unit of body weight:
Asymptote - Eventually increased dose no effect
Threshold= dose at which response begins below this dose is safe!
Below the threshold there is no observable effect
NOAEL
Above the threshold you start to see effects
LOAEL
Estimate ‘safe’ exposure from NOAEL
Acute
: Short exposure (Single dose to week of exposure), usually at high doses
Acute toxicity: Alcohol poisoning- in one dose it takes about 1 liter of 80 proof liquor to kill a 175 pound man
Cause of Death: paralyzes breathing reflex in brain
Chronic toxicity: 600 ml of 80 proof liquor/week over years in the same man
Cause of Death: Liver damage, pancreatic damage, brain damage, cancer
Acute toxicity often used:
Short exposure times make experiments inexpensive
We care mostly about populations rather than individuals
2 more items...
LD50 :
Used to compare toxicity of two or more compounds- Lower LD50 MORE Toxic
Sometimes used to estimate ‘safe’ exposures in ecotoxicology
Human Health Toxicology- Chronic studies over whole animal lifetimes most often used
Safe’ exposures are ones that are expected to cause NO effect in individuals
**
Toxic Effects
Mutagenesis/ Carcinogenesis
- Many compounds that are mutagenic are also carcinogenic
mutations: changes in DNA
Carcinogenesis
- development of cancer
Teratogenesis
Malformations in offspring caused by effects on developing embryo or fetus
Neurotoxicity
Neurotoxins- affect nerve function
Algal toxins, many snake venoms, sarin
Hypersensitivity
- Allergens = toxicants that overactivate the immune system
Pathway Disruption/Endocrine
Disruption Pathway inhibitors =
toxicants that interrupt vital biochemical processes by blocking one or more steps in pathway
The herbicide atrazine blocks steps in photosynthesis
Endocrine disruptors
= toxicants that affect the endocrine (hormone) system = chemical messenger system
Individuals vary in their responses to hazards
Different people respond differently to hazards
Affected by genetics, surroundings, etc.
People in poor health are more sensitive
Sensitivity also varies with sex, age, and weight
Fetuses, infants, and young children are more sensitive
Toxic Substances and Their Effects on Ecosystems
Toxicants concentrated in the environment can harm the health of many individuals of a species
RESULT - Population size decreases
If the species is a predator, their prey may see population growth
If the species is prey, its predator population may suffer
Cascading impacts can cause changes in the composition of biological communities Can threaten ecosystem functioning
Airborne substances can travel widely - Toxic substances are not evenly distributed in the environment
Chemicals can travel by air
Their effects can occur far from the site of use
Synthetic chemicals are found globally
Pristine lakes in the Canadian wilderness are contaminated with industrial toxicants
Bioaccumulation
= process of toxicants building up in animal tissues to greater concentration than in the environment
Biomagnification
= process that occurs when concentrations of toxicants become magnified in higher levels of the food chain
Social and environmental factors can influence the spread of infectious disease
Risk assessment = the quantitative measurement of risk
Compares risks involved in different activities or substances
Identifies and outlines problems
Risk management = decisions and strategies to minimize risk; incorporates results of risk assessment
Federal agencies manage risk
The United States has the Centers for Disease Control and Prevention (CDC), the EPA, the FDA
Scientific assessments are considered with economic, social, and political needs and values
Comparing costs and benefits is hard
Benefits are economic and easy to calculate
Health risks (costs) are hard-to-measure probabilities of a few people suffering and lots of people not
Two approaches exist for determining safety
We can not know a substance’s toxicity until it is tested
The “innocent-until-proven-guilty” approach assumes a substance is harmless until shown to be harmful
The precautionary principle
Identifies troublesome toxicants before being released
May impede the pace of technology and economic advance
principle approach assumes a substance is harmful until it is shown to be harmless
Federal agencies involved in tracking and regulating synthetic chemicals include:
The FDA: monitors food, food additives, cosmetics, drugs, medical devices
The EPA: regulates pesticides and chemicals not covered by other laws
