Exposure (toxicology)

**Toxic exposure** means that a toxin (poison) touched or got into a person's body. That person has been **exposed** to the toxin.

When a person is exposed to a toxin, many different things about that person, the toxin, and the exposure affect *toxicity*. Toxicity is how the person reacts to the toxin, including what symptoms they may have.

A person can get exposed to a toxin accidentally or on purpose. People can also use toxins as weapons to try to kill other people (for example, during chemical or biological warfare).

## Anything can be a toxin
Anything can be a toxin if enough of it gets into a person's body. For example, even water can be toxic. If a person drinks enough water (usually more than 6 gallons in one day), they can get water toxicity (also called "water poisoning" or "water intoxication"). This causes the body's cells to swell up with extra water. Swelling in the brain's cells can cause brain damage or death. Smoking is also an example of *chronic* toxic exposure. The exposure is chronic because the smoker is breathing in toxins many times, over a long period of time.

Another inhaled toxin that causes *acute* exposure is smoke from house fires. There are many toxins in this kind of smoke, including carbon monoxide and cyanide. Firefighters or people who were trapped in fires can get cyanide poisoning or carbon monoxide poisoning from breathing in these toxins. This is an example of an acute exposure, because the smoke was not breathed in for more than 24 hours.

### Absorption
If a toxin gets in a person's eyes or on their skin, it can get taken up into the bloodstream. This is called absorption. Absorption through the skin is the most common route of toxic exposure.p.&nbsp;97

The skin is able to keep some toxins from getting into the body. However, if a person has a cut or wound on their skin, any toxin will be able to get into the body through that wound. Also, the toxin will be taken up into the bloodstream more quickly, because it does not have to get absorbed through the skin.

### Ingestion
 from feces. These toxins then cause disease when people drink the water.]]
Ingestion means that a person swallowed the toxin. Some chemicals cannot get into the bloodstream from the gastrointestinal tract. However, others are absorbed through the lining of the intestinal tract into the bloodstream. There are many different toxins that can be carried in water. They can be chemicals, like lead. They can also be biological toxins, like the bacteria that causes cholera, and the viruses that cause Hepatitis A and polio. People ingest these toxins by drinking the contaminated water, or eating food made with the water. The World Health Organization says that about 502,000 people die every year because of toxins in water and the diseases they cause.

### Injection
An injected toxin gets into the body when something carrying the toxin breaks the skin. Injections can go into a vein, a muscle, or just under the skin. Toxins that are injected into a vein have the fastest effects, because the toxin is being put right into the bloodstream. Venom differs from toxins. For example if you bit a snake and got sick, you would be getting sick from a toxin; If a snake bites you and you get sick, it would be from venom. 

An example of a toxin which is often injected on purpose is Botulinum. This can cause botulism. It is also sold under the name "Botox." Many people choose to get Botulinum toxin injected into their faces to get rid of wrinkles. The toxin paralyzes some of the muscles in the face, usually for three to 12 months, and makes the face look smoother.

### More than one route
Some toxins can get into the body through more than one route of exposure. For example, if water is polluted, a person can get exposed to the toxins in the water by drinking it (ingestion) and by showering or swimming in it (absorption).
* Concentration: *How much* of the toxin was the person exposed to?
* Duration: *How long* was the person exposed to the toxin?
* Frequency: *How many times* was the person exposed?

The route of exposure also affects toxicity. 

For example, if it is injected, snake venom can be life-threatening. However, if it is ingested, snake venom is usually not harmful. The effects of this toxin are very different depending on the route of exposure.

### The exposed person
Toxins sometimes affect different people in different ways. This is partly caused by differences in people's bodies. A person's age, gender, genes, hormones, nutrition, and the strength of their immune system all affect toxicity.) If a person ingests a toxin that cannot dissolve into the watery plasma, the toxin will not absorb into the bloodstream through the lining of the gastrointestinal tract. It will pass out of the body through the gastrointestinal tract.

Other toxins are "lipid-soluble" (they dissolve in fats). Instead of getting absorbed into the bloodstream, these toxins get stored in the body's fat. When the person's body burns fat to make energy, these toxins are let out and can poison the person. Examples of fat-soluble toxins include lead, DDT, and mercury.

#### pH
The toxin's pH is also important. For example, if a toxin is a strong acid or a strong base, it can cause severe chemical burns to the eyes and skin.p.&nbsp;100 Toxins that have a more neutral pH can still hurt the body by being absorbed into the bloodstream, but they will not burn the eyes and skin. For example, if a person swims or bathes in water contaminated with cholera toxin, the toxin can still get absorbed through his eyes or skin. However, the water will not burn the eyes or skin.

## Related pages
* Toxin
* Absorption
* Excretion
* Solubility
* pH

## References