Environmental Engineering Reference
In-Depth Information
• Decrease in crop diversity
• Increase in pest and disease resilience
• Abnormalities and mutations occurring that would not occur naturally
• Possible species extinctions due to natural species being out-competed by modified ones
Hazardous Chemicals in the Environment
When substances are considered to be
toxins,
or poisonous substance, they are classified based on their poten-
tial health impacts.
Types of Hazardous Waste
Neurotoxins
Neurotoxins target the nervous system, affecting motor control and brain function. Heavy metals
such as lead, cadmium, and mercury are classified as neurotoxins.
Carcinogens
Carcinogens are cancer-causing toxins, such as asbestos, formaldehyde, radioactive sub-
stances, and some organic compounds like benzene.
Teratogens can affect embryo development, harming or killing the fetus. Known teratogens in-
clude alcohol and thalidomide.
Teratogens
Mutagens create mutations in the DNA of organisms and include radiation, nitrous oxide, and
UV light. Many mutagens including benzene are also carcinogens.
Mutagens
Endocrine disruptors alter the hormone (endocrine) system, usually by binding to hormone re-
ceptors in place of the existing, desired hormone or by otherwise blocking hormone effects.
DDT, the pesticide once used in the United States, is an endocrine disruptor.
Endocrine
disruptors
Allergens overactivate the immune system, stimulating a disproportionate response in those
who are allergic. Examples range from pollen and dust mites to peanuts.
Allergens
Biomagnification and Bioaccumulation
Over time, toxins may build up, or
bioaccumulate,
in organisms' muscles, organs, and other tissues. Especially
if a substance is fat- or oil-soluble, it can dissolve into fatty tissues and accumulate in the organism. This accu-
mulation can magnify through the food chain as predators consume organisms, each with accumulated toxins,
which then pass to the predator. Thus, toxin levels tend to increase dramatically with each step higher in the
food chain. The buildup of toxins within an organism through the consumption of other organisms is called
biomagnification.
Treatment and Disposal of Hazardous Waste
Disposal of hazardous chemicals poses a serious threat to human and environmental health. Some hazardous
substances degrade over time until they are no longer dangerous, but some substances
persist,
or remain in the
environment for an extended period of time. Heavy metals, many organic compounds, and radioactive waste
all persist in the environment. Hazardous waste substances can be classified as:
•
Toxic:
Harmful to human health
•
Corrosive:
Can wear away and break down metals
•
Reactive:
Easily react with other substances and can cause a serious reaction such as explosions or toxic
gases
•
Ignitable:
Easily combustible
