Chemical Hazards Flashcards
Advantages and disadvantages of chemicals
-Advantages:
-Chemicals are essential for development and
everyday life:
-Modern fertilizers and pesticides have been a boon
to agriculture and help feed our growing populations.
-Chemicals have served medicine in many ways, from
pharmaceuticals to equipment and materials used in
hospitals.
-From transportation to information technology to
entertainment, our quality of life would not be the
same without a chemical manufacturing industry.
-Disadvantages:
-Chemicals are implicated in diseases, including
cancer, birth defects, reproductive and
neurobehavioral disorders, and impaired immune
systems:
-Thousands of accidental poisonings result from
inappropriate use of toxic pesticides.
-Chemicals help deplete the ozone layer, accumulate
in poorly managed stockpiles, and waste sites, &
pollute air, water, soil.
-Many persist in the environment leading to
increasing levels in humans and wildlife.
Definition of chemical toxicity
The inherent capacity of a substance to cause injury to a living organism (animal, plant, or human).
Toxicokinetic processes (and definitions) that take place after exposure to a toxicant occurs
-Absorption – main routes of exposure (inhalation,
ingestion, dermal) are the primary routes of absorption
into the body.
-Distribution – occurs via the bloodstream to organs
and tissues.
-Metabolism – the toxicant undergoes
biotransformation, wherein it is detoxified or
undergoes increased toxicity.
- Excretion – the toxicant is eliminated from the body:
1) by the kidneys via urine
2) by the liver and GI tract via feces
3) by the pulmonary system via exhaled air
4) by breast milk.
Biotransformation (i.e., including detoxification and bioactivation)
Absorbed chemicals undergo biotransformation in the liver where they may undergo detoxification or bioactivation (increased toxicity).
Definition of persistent organic pollutants
-Organic, often highly chlorinated compounds that
degrade slowly over many years, accumulate in food
chains, and are toxic to living organisms.
-POPs include pesticides, dielectric and hydraulic fluids,
combustion products, by-products of manufacturing,
and waste incineration products.
Definition of endocrine disrupting chemicals
Chemicals that either mimic, antagonize, or disrupt the action of endogenous hormones, or alter the synthesis or metabolism of natural hormones in human or animal systems.
Animal feeding operations and confined animal feeding operations
-Animal feeding operations (AFOs) are agricultural
enterprises where animals are kept and raised in
confined situations. AFOs congregate animals, feed,
manure and urine, dead animals, and production
operations on a small land area. Feed is brought to the
animals rather than the animals grazing or otherwise
seeking feed in pastures, fields, or on rangeland.
There are approximately 450,000 AFOs in the United
States.
-Concentrated animal feeding operations (CAFOs) are a
relatively small number of AFOs that are regulated by
the EPA.
-Manure and wastewater from AFOs have the potential
to contribute pollutants such as nitrogen and
phosphorus, organic matter, sediments, pathogens,
heavy metals, hormones, antibiotics, and ammonia to
the environment.
-Excess nutrients in water (i.e., nitrogen and
phosphorus) can result in or contribute to low levels of
dissolved oxygen (anoxia), eutrophication, and toxic
algal blooms.
Integrated pest management
-Pesticide concerns have fostered the development of
integrated pest management (IPM) that uses a variety
of controls, to include:
-conservation of natural enemies
-crop rotation, intercropping
-cultivation of pest-resistant varieties.
-Pesticides may be used but only selectively and in
reduced quantities.
Definition of organic agriculture
Uses composted manure and other natural materials and crop rotation rather than synthetic fertilizers and pesticides that can pollute soil with excess of nitrogen and phosphorous causing runoff and pollution of ground water and larger bodies of water.
