Exposure (toxicology)

concept in 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").[1] This causes the body's cells to swell up with extra water. Swelling in the brain's cells can cause brain damage or death.[1] Water, in normal amounts, helps keep us alive; but if a person is exposed to enough of it, it becomes a toxin, and it can kill the person.

The dose of something which is fatal in 50% of cases is measured in weight of the toxin per kg of body fat in humans. This is called the LD50.

Types of exposure


There are two major types of exposure: acute and chronic.

An acute exposure happens only one time. Chronic exposure happens many times, over a long period of time.

The United States Centers for Disease Control and Prevention (CDC) defines these types of exposure this way:[2]p. 105

  • An acute exposure lasts 24 hours or less
  • A chronic exposure lasts for more than three months

Routes of exposure


Toxins can get into the body in four different ways. These are called "routes of exposure." The route of exposure is one of the many things that affects toxicity.


Poison gases were used often during World War I as chemical weapons. This picture shows British soldiers who died after inhaling a toxin, probably phosgene, in a German gas attack.

Toxins can get into the body through inhalation (the person breathes in the toxin). If a toxin is a gas, inhalation is usually the way it gets into the body.[3]p. 1

When a toxin is inhaled, it may injure the airways and the lungs. Also, some toxins can go from the lungs into the bloodstream. The bloodstream then delivers blood - with the toxin in it - to all of the organs in the body. The toxin can then damage those organs.[3]p. 1

Inhalation is one of the easiest and fastest ways for toxins to get into the body. The lining of the respiratory tract absorbs toxins into the bloodstream very quickly.[2]p. 99

Examples of inhaled toxins


An example of a commonly inhaled toxin is cigarette smoke. There are over 100 toxins in cigarette smoke, including formaldehyde, arsenic, and hydrogen cyanide.[4] 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.[5] This is an example of an acute exposure, because the smoke was not breathed in for more than 24 hours.



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.[2]p. 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.[2]p. 98

Examples of absorbed toxins


Exposure by absorption often happens in workplaces where people work with toxins. For example, if a person who works at a gas station spills gasoline on himself, the body will quickly absorb the gasoline into the bloodstream.[2]p. 98 Some chemical weapons like sarin, a nerve gas, can also be absorbed through the skin and the eyes, along with being inhaled.[6]


Educational poster showing how groundwater can get contaminated with pathogens 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.[2]p. 100

Examples of ingested toxins


Ingestion of toxins is very common in developing countries, where many people do not have safe drinking water.[7] There are many different toxins that can be carried in water. They can be chemicals, like lead.[8] They can also be biological toxins, like the bacteria that causes cholera, and the viruses that cause Hepatitis A and polio.[9][10][11] 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.[7]

Toxins in water can be killed by heating them up to boil at a high enough temperature. Boiled water can be more safe to drink.

Food poisoning is also caused by ingestion of toxins, like E. coli bacteria, which can live in foods like meat and poultry.[12]



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.[3]p. 2

Examples of injected toxins


Some snakes, scorpions, and spiders carry venom. If they bite or sting a person, they are injecting a toxin into the body.[13] 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.[14]

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).[7]

Things that affect toxicity


Once a person has been exposed to a toxin, there are many things that affect toxicity. This article talks about only a few.

The exposure


Many things about a person's exposure affect toxicity. Three of the most important things are:[3]

  • 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.[15] 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.[3] For example, infants, young children, and the elderly are more likely to get sick from lower concentrations of toxins, which might not make a healthy adult sick.[3]

People with health problems


Some health problems can affect toxicity. For example, inhaling toxins is especially dangerous for people who already have lung diseases, like emphysema. If the lungs are already damaged, breathing in toxins is likely to cause even more damage, and puts the person at risk for respiratory failure.[2]p. 99

Also, once a toxin gets into the bloodstream, the body immediately starts trying to get rid of it through excretion. The main organs involved with excretion are the kidneys, liver, and lungs. If a person has damage to any of these organs (like kidney failure or cirrhosis of the liver), they will be unable to get rid of the toxin as fast as a healthy person will. Because of this, a toxin may shut down the liver or kidneys. The chemical will stay in their body longer, and have more toxic effects.[2]p. 103

The type of toxin


Many things about the type of toxin a person was exposed to affect toxicity. Two examples are solubility and pH.



A toxin's solubility is its ability to mix into a liquid. If a toxin is not water-soluble (it cannot dissolve in water), it cannot absorb into the bloodstream. (Plasma, the liquid part of blood, is made mostly of water.[16]) 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.[2]pp. 102–103

However, many toxins are water-soluble and will get absorbed into the bloodstream. For example, the Vibrio cholerae bacteria is water-soluble. If a person ingests water or food that has this toxin in it, they can get cholera.[13][17]

Example of a burn caused by a strong acid

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.[18]

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.[2]p. 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.



  1. 1.0 1.1 Gill M; McCauley M 2015 (2015). "What Do Psychiatric Patients, Marathon Runners and Ravers Have in Common? A Case Report on the Consequences of Water Intoxication". European Psychiatry. 30 (Supplement 1). European Psychiatric Association: 1922. doi:10.1016/S0924-9338(15)31471-1. S2CID 77529504.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 Agency for Toxic Substances and Disease Registry (2002). "Module 2: Routes of Exposure". A Toxicology Curriculum for Communities Trainer's Manual (PDF). United States Centers for Disease Control and Prevention.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 "Toxicology and Exposure Guidelines" (PDF). University of Nebraska-Lincoln Environmental Health Services. University of Nebraska-Lincoln. January 2003. Retrieved February 7, 2016.
  4. "2010 Surgeon General's Report: Chemicals in Tobacco Smoke". CDC.gov. United States Centers for Disease Control and Prevention. March 21, 2011. Retrieved February 7, 2016.
  5. Alarle Y 2002 (2002). "Toxicity of fire smoke". Critical Reviews in Toxicology. 32 (4): 259–89. doi:10.1080/20024091064246. PMID 12184505. S2CID 23858610.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  6. "Facts About Sarin". Emergency Preparedness and Response. United States Centers for Disease Control and Prevention. May 20, 2013. Archived from the original on April 14, 2003. Retrieved February 7, 2016.
  7. 7.0 7.1 7.2 World Health Organization (2014). Preventing Diarrhoea Through Better Water, Sanitation, and Hygiene: Exposures and impacts in low- and middle-income countries (PDF) (Report). WHO Press. p. ix. ISBN 978-92-4-156482-3. Retrieved February 7, 2015.
  8. Cotruvo, Dr. J; Fawell, J.K.; et al. (2011). Lead in Drinking-water: Background document for development of WHO Guidelines for Drinking-water Quality (PDF) (Report). World Health Organization. Retrieved February 7, 2016.{{cite report}}: CS1 maint: multiple names: authors list (link)
  9. "Water-related Diseases: Cholera". WHO.int. World Health Organization. 2016. Archived from the original on January 26, 2016. Retrieved February 7, 2016.
  10. "Water-related Diseases: Hepatitis". WHO.int. World Health Organization. 2016. Archived from the original on February 19, 2016. Retrieved February 7, 2016.
  11. "Poliomyelitis (polio)". WHO.int. World Health Organization. 2016. Retrieved February 7, 2016.
  12. "E. coli (Escherichia coli)". Division of Foodborne, Waterborne, and Environmental Diseases. United States Centers for Disease Control and Prevention. Retrieved February 7, 2015.
  13. 13.0 13.1 World Health Organization (2004). Guidelines on the Prevention of Toxic Exposures: Education and public awareness activities (PDF) (Report). WHO Press. ISBN 92-4-154611-5.
  14. "Botox Injections". The Mayo Clinic. Mayo Foundation for Medical Education and Research. February 6, 2013. Retrieved February 7, 2016.
  15. "Frequently Asked Questions About Venomous Snakes". Department of Wildlife Ecology & Conservation, UF Wildlife – Johnson Lab. University of Florida. May 2, 2012. Retrieved February 7, 2016. Venoms are generally not toxic if swallowed, and must be injected under the skin (by snakes, spiders, etc.) into the tissues that are normally protected by skin in order to be toxic. However, we do NOT recommend drinking venom!
  16. "Plasma components". NHS Choices. National Health Service of the United Kingdom. September 16, 2014. Retrieved February 7, 2016.
  17. "Product Information: Cholera Toxin from Vibrio cholerae" (PDF). sigmaaldrich.com. Sigma-Aldrich Co. LLC. 2007. Archived from the original (PDF) on August 29, 2017. Retrieved February 7, 2016.
  18. Lerner, K. Lee; Lerner, Brenda Wilmoth (October 9, 2007). "Biomagnification". Gale Encyclopedia of Science (4th ed.). Gale. ISBN 978-1414428772.