what naturally accurring substances are harmful to humans
Poisons and toxins
Photo by: Bill Frische
A poison is whatsoever chemical that kills or injures an organism. The term toxin refers to a poison produced by a living organism, such equally a microorganism, a institute, or an animal. In everyday practice, the terms poisonous substance and toxin are oftentimes used interchangeably.
Information technology is important to understand that any chemical is potentially poisonous. All that is required for a chemical to cause toxicity is a dose large plenty to cause some harmful effect. For instance, water could be considered toxic if a person drank iv gallons of information technology all at once. In such a case, the water would cause serious actual harm—even death. In a large quantity, then, h2o could be classified as a toxicant.
Toxicity
The term toxicity is used to express how poisonous a chemical is. Scientists distinguish between 2 kinds of toxicity: acute and chronic. Acute toxicity refers to the amount of damage caused by a chemical later on a brusque-term exposure to a large dose of the chemical. For case, a person might accidentally consume a tablespoon of rat poisonous substance. The effects caused by that accident would be described equally the chemical's acute toxicity.
Scientists have various means of measuring the acute toxicity of a chemical. Perhaps the most common is chosen LD 50 . The abbreviation LD fifty stands for "lethal dose, fifty per centum." It is the corporeality of the chemical required to kill i-half of a population of organisms in a short period of time.
Words to Know
Acute toxicity: A poisonous effect produced by a single, short-term exposure to a toxic chemical, resulting in obvious wellness effects and even decease of the organism.
Chronic toxicity: A poisonous effect that is produced by a long period of exposure to a moderate, less-than-acute dose of some toxic chemical.
Exposure: The concentration of a chemical in the environment or the accumulated dose that an organism encounters.
LD fifty : The amount of a chemical required to kill one-half of a population of organisms in a short period of time.
Some chemicals cause furnishings that are difficult to notice over a curt period of time. These effects are referred to every bit chronic toxicity. For instance, a person who works with the mineral asbestos runs the hazard of developing various respiratory disorders tardily in his or her life. Such disorders include emphysema, chronic bronchitis, and lung cancer. These disorders may not bear witness up for many years after exposure to asbestos. Thus, they are known equally chronic effects of exposure to a toxicant.
In humans and other animals, long-term chronic toxicity can occur in the form of increased rates of birth defects, cancer, organ damage, and reproductive bug, such every bit spontaneous abortions. In plants, chronic toxicity tin often be recognized in terms of decreased productivity (in comparing with plants that are non chronically exposed to the toxic chemicals in question). Because they develop over very long periods of time and are frequently difficult to recognize in their early stages, chronic toxicities are much more difficult to detect than are astute toxicities.
LD l Value for Various Chemicals
| Chemical | LD 50 Value* |
| * In milligrams of chemical per kilogram of torso weight. | |
| TCDD (a grade of dioxin) | 0.01 |
| Tetrodotoxin (globefish toxin) | 0.01 |
| Saxitoxin (shellfish toxicant) | 0.8 |
| Carbofuran (a pesticide) | 10 |
| Phosphamidon (an insecticide) | 24 |
| Nicotine | 50 |
| Caffeine | 200 |
| Dichloro-diphenyl-trichloroethane (an insecticide) | 200 |
| 2,4–D (an herbicide) | 370 |
| Mirex (an insecticide) | 740 |
| Acetylsalicylic acid (aspirin) | 1,700 |
| Malathion (an insecticide) | ii,000 |
| Sodium chloride (tabular array table salt) | 3,750 |
| Glyphosate (an herbicide) | iv,300 |
| Ethanol (drinking alcohol) | 13,700 |
| Sucrose (table sugar) | xxx,000 |
For every poisonous substance, in that location is a certain threshold of tolerance beneath which no harmful effect is likely to occur. For example, the threshold for a detail chemic might be v milligrams of the chemical per kilogram of body weight. If a person is exposed to less than 5 milligrams of the chemic per kilogram of body weight, no harmful event is likely to occur. If the exposure exceeds that amount, then the symptoms of poisoning brainstorm to appear.
Some naturally occurring poisons
Many poisonous chemicals are present naturally in the environment. For example, naturally occurring elements such as arsenic, mercury, pb, and cadmium are toxic in various concentrations to both plants and animals. Areas where these elements occur in large concentrations are ordinarily barren of plants and animals.
Other naturally occurring toxins are substances produced by plants and animals. In many cases, these toxins are part of a plant or brute'south natural defence organisation, protecting them from other plants and animals that prey on them. Ane such case is the chemical tetrodotoxin, synthesized by the Japanese globefish ( Spheroides rubripes ). Tetrodotoxin is extremely toxic even if ingested in tiny amounts. Only slightly less toxic is saxitoxin, synthesized past species of marine phytoplankton but accumulated by shellfish. When people eat these shellfish, a deadly syndrome known every bit paralytic shellfish poisoning results. There are numerous other examples of deadly biochemicals such as snake and bee venoms, toxins produced by disease-causing microorganisms, and mushroom poisons.
Poisons produced past human applied science
In the modern globe, humans are responsible for many of the toxic chemicals that are now existence dispersed into the environment. In some cases, human being actions cause toxic damage by emitting large quantities of chemicals that likewise occur naturally, such as sulfur dioxide, hydrocarbons, and metals. Release of these chemicals as the outcome of homo activities only increases the severity of problems that may already exist because of the natural presence of these chemicals.
Humans, however, also produce and release to the environment large quantities of chemicals that do non occur naturally. These synthetic (made in a lab) chemicals include thousands of dissimilar pesticides, medicines, and various kinds of industrial chemicals, all of them occurring in complex mixtures of various forms. Many of these chemicals impact humans and other organisms directly, as is the case with many pesticides. In other cases, toxicity occurs indirectly. An case is the form of compounds known as the chlorofluorocarbons (CFCs). Normally these chemicals are quite inert (inactive). However, when they find their way to the upper atmosphere, they break apart into simpler chemicals that consume ozone, the gas that protects life on Globe from harmful ultraviolet radiation. As a result, the hazard of disorders such as skin cancers, cataracts, and immune disorders greatly increases.
In an endeavor to command the effect of highly toxic chemicals, 122 nations met in tardily 2000 and agreed to a treaty calling for the global elimination of 12 chemical pollutants. Environmentalists have called these the "muddied dozen." The twelve include eight pesticides (aldrin, chlordane, Ddt, dieldrin, endrin, heptachlor, mirex, and toxaphene), two types of industrial chemicals (hexachlorobenzene and polychlorinated biphenyls or PCBs), and two types of industrial byproducts (dioxins and furans). These toxic pollutants were chosen not because they are the most dangerous, only considering they are the most widely studied. The treaty must be ratified by fifty nations before information technology can have outcome.
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Source: http://www.scienceclarified.com/Ph-Py/Poisons-and-Toxins.html
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