What makes arsenic poisonous

If arsenic binds to the sulfur at these sites, the enzymes can begin to behave in abnormal ways or lose their ability to function.

Arsenic, in the form of arsenate, can also resemble phosphate, which is used by cells for energy and signaling. By displacing phosphate in enzymes or signaling proteins, arsenic can block energy production and normal cell signaling. At lower chronic exposures, such as in most environmental or occupational exposures, arsenic appears to indirectly modify the way cells communicate.

Recent studies at Dartmouth suggest that arsenic may act as an endocrine disrupter by binding to hormone receptors, interfering with normal cell signaling of hormones through those receptors. Disruption of these endocrine receptors by arsenic in this way may contribute to the development of diabetes, cancer and vascular disease.

Other Dartmouth researchers have found that arsenic may interfere with molecular signals that prompt the cells lining heart and blood vessels to grow. The subsequent build-up of these cells can narrow the passage inside blood vessels, restricting the flow of blood. This may be one of the mechanisms that enable arsenic to contribute to cardiovascular disease and other blood vessel diseases. Dartmouth researchers are also trying to understand other ways in which arsenic increases the risk of certain kinds of cancer.

Unlike many other known chemical carcinogens, arsenic does not cause damage to DNA or cause mutations in genes. Instead, it appears to indirectly modify the way cells behave in ways that increase their probability of becoming cancer cells, perhaps in combination with other carcinogens such as cigarette smoke or other environmental contaminants.

The effect arsenic has on living things is strongly governed by its form or species. Although metals are simple elements, metal atoms can combine into different forms that vary in chemical and biological properties. Some forms of arsenic are highly toxic; others are essentially non-toxic.

The reasons are rooted in basic chemistry. Atoms are made up of a nucleus — a mixture of positively charged particles called protons and neutral particles called neutrons — around which negatively charged particles called electrons orbit. Atoms can gain or lose electrons to change their ionic charge, and the sharing of electrons is primarily how atoms bond together to form molecules.

These two forms can be readily converted back and forth both in nature and inside our bodies depending on the local chemical environment — such as changes in acidity pH , the presence of oxygen or iron, and what other molecules are present. Arsenite is believed to be slightly more toxic than arsenate, but since they are so easily inter-converted, both forms are considered a health risk.

When arsenic binds to elements such as sulfur, oxygen, and chlorine it forms molecules known as inorganic compounds; when arsenic binds to molecules containing carbon it forms organic compounds. Inorganic forms of arsenic are, in general, more toxic to humans since they are less stable and may allow arsenic to interact with important cellular molecules.

Both the inorganic and organic forms of arsenic are readily eliminated from the body through the urine. When we are exposed to inorganic arsenic, the body routinely changes, or metabolizes, it into one or more organic forms by successively adding carbon atoms to it.

Scientists once believed that this process — known as methylation — was a natural arsenic detoxification process for both humans and other animals. But new findings have challenged that idea. Animal species that do not methylate arsenic are not only able to excrete inorganic arsenic efficiently but appear to be no more sensitive to its toxic effects than animals that methylate.

More recently, scientists have found that a simple methylated form of arsenic called mono-methylarsenic III can cause cancer in animals. So although fish may have high amounts of arsenic in them, it is primarily in a form that is not a health risk to humans.

There is evidence that humans and other animals can build up tolerance to the toxic effects of arsenic. Rasputin was reported to regularly ingest arsenic to build tolerance and to protect himself from poisoning.

Like any other poison, whether an exposure to arsenic is harmful largely depends on its chemical and physical form and how one is exposed. Toxicologists use the terms dose, duration and route of exposure, meaning the amount of a substance taken in, the period of time the exposure lasts, and the way the substance enters the body.

One way of being exposed to arsenic is by breathing it in as a dust. This primarily occurred in workplace settings where arsenic or products containing arsenic were used, and before new knowledge led to the development of modern worker safety measures. There is normally little or no uptake of arsenic through the skin at environmental levels, though it was of concern in previous workplace exposures such as long-term use of arsenic-containing pesticides or through use of arsenic-containing medications applied directly to the skin.

The route of exposure of most concern today is ingesting arsenic, particularly through drinking water contaminated by inorganic arsenic. The concentrations of arsenic found in the heavily contaminated drinking water of Bangladesh are between and micrograms per liter A microgram is a millionth of a gram.

By contrast, a person would have to ingest more than 70, micrograms of arsenic all at once to be fatally poisoned by a single dose. Nevertheless, exposure over a long period of time to concentrations of arsenic such as those found in Bangladesh is associated with a wide range of illnesses. Few studies have examined the effects of lower doses on people over long periods of time.

Dartmouth researchers are conducting epidemiological studies to determine the health effects of drinking water containing arsenic at the elevated levels found in certain regions of the United States. These levels -typically between 50 and micrograms per liter — are much lower than those of Bangladesh but are still considered high enough to be of concern.

On the one hand, arsenic is one of a handful of chemicals that is well established as a human carcinogen based on direct evidence in human populations. On the other hand, arsenic has been shown to be effective as a cancer chemotherapy drug and can be used to induce complete cures in certain forms of cancer. Surprisingly, it has been difficult to demonstrate that arsenic can increase the incidence of cancer in animals despite the strong human epidemiological data.

This is also true of several other carcinogenic metals including chromium, cadmium and nickel. The reasons are unclear, but one view is that these agents act indirectly, by increasing the risk of cancer from other factors.

This would not be evident in experiments in which animals are raised in a relatively pristine laboratory environment and exposed only to the metal in question. Beginning around the s, the Chinese began to systematically experiment with the use of arsenic to treat certain cancers. It is also used:. Some people are more likely to be exposed to arsenic, but it can occur in anyone.

Factors that may increase your chance of arsenic exposure include:. In addition, children may be more susceptible than adults to the health effects of arsenic.

There is some evidence that arsenic exposure may harm pregnant women and their unborn babies. Ingesting high levels of arsenic can result in death. Arsenic has also been linked to increased risks of cancer of the lung , skin , bladder , liver , kidney , and prostate. Symptoms of acute arsenic exposure generally occur within minutes after ingestion. These may include:.

You will be asked about your symptoms and medical history. A physical exam will be done. It can be difficult to make a diagnosis of arsenic poisoning because symptoms are so varied. If you have concerns about arsenic causing symptoms in yourself or a family member, talk to your doctor.

There is no effective treatment for arsenic toxicity. There is increasing evidence that chelation therapy may benefit some people who were poisoned with arsenic.

Chelation therapy involves putting a chemical called a chelating agent into the bloodstream. The chelating agent combines with a toxin to help remove it from the body. Chelating agents may be given by pill or by injection. If chelation is not indicated or is ineffective, your treatment will be designed to help manage and control your symptoms. Treatment may include IV hydration, for example. Agency for Toxic Substances and Disease Registry website. Accessed January 29, Some studies have shown that garlic can treat arsenic poisoning, but we suggest heading to the hospital before the pantry.

Got a question? Send us an email and we'll look for an expert who can crack it. Arsenic is a heavy metal which is a natural component of the earth's crust. It exists in compounds that may be organic or inorganic. It is highly toxic in its inorganic form. Poisoning can occur by ingestion, inhalation and dermal absorption.

Elemental arsenic is the least toxic. Trivalent arsenic is well absorbed through the skin and is 60 times more toxic than pentavalent arsenic, which is well absorbed by the gut. Toxicity is due to arsenic's effect on many cell enzymes, which affect metabolism and DNA repair. Arsenic is excreted in urine but can also accumulate in many body tissues. Arsenic has been used in many medicines and was widely used to treat syphilis until the mid 20th century. It is currently used to treat acute promyelocytic leukaemia and other myeloproliferative disorders.

It shares many toxic features with the other heavy metals like mercury and lead. It is used in the production of glass and semiconductors.

It is found naturally in some water supplies and, in its least toxic form, in fish and seafood. In Victorian times arsenic was famous as a homicidal or suicidal poison; it is now thankfully much harder to obtain. Health and safety at work have also improved so that, in the UK, both acute and chronic arsenic poisoning are rare.

Geological contamination of underground water supplies occurs in parts of: [ 4 , 5 ]. Occupational exposure [ 9 ] This can occur in:.

Note that organic arsenics found in fish and seafood are non-toxic and not a cause of arsenic poisoning. Similarly, the long-term exposure with the cutting and burning of wood preserved with copper chrome arsenate leads to elevated blood levels but no signs or symptoms of toxicity.