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Environmental Toxicants: Types, Sources & Effects

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  • 0:05 Toxic Agents of the…
  • 0:51 Types of Toxicants
  • 3:21 Sources of Toxicants
  • 5:24 Lesson Summary
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Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

In this video lesson, you will identify different types of environmental toxicants. You will also learn about the harmful effects of these toxicants and how they travel from various sources.

Toxic Agents in the Environment

Poison ivy. Just hearing those words makes some people start itching. Poison ivy contains a toxin that causes severe reactions in many people, so we tend to steer clear of it. Now think of doing your laundry. You probably use detergent in the wash to get your clothes clean, right? You may not put poison ivy and laundry soap in the same category, but environmental toxicologists do.

They study toxicants, which are toxic substances in the environment. Toxicants come in all shapes and sizes, and while they can come from both natural and human-made sources, this lesson will focus on human-made toxicants and their effects on human and environmental health.

Types of Toxicants

As mentioned before, there's a wide variety of toxicants in the environment. To better understand them, we can put them into specific categories that are based on the types of problems they cause. Carcinogens are probably the best-known toxicant because these are cancer-causing chemicals. Cigarette smoke falls into this category as it contains over 4,000 chemicals, many of which cause cancer.

Mutagens are mutation-causing chemicals. When organisms are exposed to a mutagen, it literally mutates their DNA, leading to cancer and other disorders. X-rays are well known mutagens. Teratogens are chemicals that cause harm to unborn babies. The name of this toxicant comes from the Greek word teras, which means monster.

These chemicals cause birth defects during development in the womb. Thalidomide was used in the 1950s as a sleeping pill and to prevent nausea during pregnancy, but turned out to be a very harmful teratogen. Even a single dose is powerful enough to cause severe birth defects in children.

Allergens are chemicals that stimulate overactivity in the immune system. When you are exposed to allergens, your body goes into overdrive, triggering an immune response to try and get rid of the allergen. This is why pollen and dust cause symptoms that are similar to being sick.

Neurotoxins are chemicals that attack the nervous system. These include heavy metals, like lead and mercury, as well as pesticides and chemical weapons. Neurotoxins can lead to symptoms like slurred speech, loss of muscle control and even death.

Endocrine disrupters are chemicals that disrupt the endocrine system in organisms and most often come from prescription drugs and chemicals in plastics. The endocrine system is also known as the hormone system, and this part of your body is what regulates growth, development, sexual maturity, brain function and even appetite.

Toxicants that disrupt hormone functioning can lead to some serious problems because they so closely resemble real hormones in your body. Reptiles and amphibians are especially sensitive to endocrine disrupters and exposure often leads to feminization of male animals. This may seem like a lot to remember! But if you look closely, you'll see that the name of the toxicant describes the effect it has on organisms, which helps us understand these toxicants better.

Sources of Toxicants

We are surrounded by synthetic chemicals and encounter them countless times on a daily basis. Plastics, household cleaners, solvents, detergents, cosmetics and perfumes are all toxicants. So are antibiotics, prescription drugs, steroids, food additives, preservatives and other things we ingest. Pesticides, herbicides and fertilizers are also toxicants.

Though toxicants come from many sources, they tend to move through the environment in certain ways. Toxicants may find their way into aquatic systems as they get carried away by runoff from large areas of land. Because the water systems are smaller than the land that supplied the contaminants, the toxicants tend to get concentrated in the water.

Once in surface water, toxicants can leach down into groundwater and contaminate sources of drinking water. Many chemicals are quite water-soluble, which means that they are easily dissolved by water. Because most organisms need water, this also means that we are most susceptible to these toxicants.

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