Arsenic poisoning occurs when arsenic, a naturally occurring element found in soil, water, and certain foods, builds up in the body to toxic levels. It can happen suddenly from a single large dose or gradually over months and years of low-level exposure. Arsenic is classified as a known human carcinogen, and chronic exposure raises the risk of lung, bladder, and kidney cancer for decades after the exposure stops.
How Arsenic Damages Your Cells
Arsenic exists in two main forms, and each one attacks your body’s energy production through a different route. The first form mimics phosphate, a molecule your cells need to generate energy. Because arsenic looks so chemically similar to phosphate, your cells mistakenly use it in place of the real thing. The result is an unstable, useless product that quickly falls apart, bypassing the step where your cells would normally produce ATP, the molecule that powers virtually every function in your body. This same substitution happens inside your mitochondria, the energy factories within each cell, further draining your energy supply.
The second form of arsenic targets sulfur-containing groups on key enzymes. These groups act like on-switches for enzymes involved in cellular respiration. When arsenic binds to them, it shuts those enzymes down. One well-studied target is pyruvate dehydrogenase, a critical enzyme in the energy cycle. With this enzyme disabled, your cells can’t efficiently convert food into usable energy. Notably, when arsenic is processed (methylated) inside the body, the resulting compounds are even more potent at shutting down these enzymes than the original form.
Symptoms of Acute Poisoning
A large single dose of arsenic, typically from ingestion, produces symptoms within 30 minutes to several hours. The earliest signs are a burning sensation in the lips, tightness in the throat, intense thirst, and a metallic or garlic-like taste in the mouth. Severe abdominal pain, nausea, and vomiting follow quickly.
The hallmark of acute arsenic poisoning is a distinctive watery diarrhea sometimes called “rice water” stools, caused by inflammation and tissue death in the lining of the digestive tract. This diarrhea can become bloody. The rapid fluid loss leads to dangerous drops in blood pressure, electrolyte imbalances, and shock. Heart rhythm abnormalities, including dangerously fast or irregular heartbeats, can develop as the cardiovascular system destabilizes. Without treatment, severe acute poisoning can be fatal.
Signs of Chronic Exposure
Long-term, low-level arsenic exposure produces a different set of symptoms that develop slowly and can be easy to miss at first. The skin is often the first place chronic poisoning shows up. Patchy dark brown pigmentation can appear anywhere on the body, and when pale spots are scattered within the darkened areas, the pattern is sometimes described as “raindrops on a dusty road.” This distinctive appearance is considered a hallmark of chronic arsenic exposure.
Thickened, rough skin on the palms and soles is another characteristic sign. These growths, called keratoses, appear as small corn-like bumps typically 0.4 to 1 centimeter across. The fingernails may develop horizontal white lines known as Mees’ lines, which can appear weeks after a significant exposure event or accumulate over time with ongoing low-level contact.
Beyond the skin, chronic exposure can damage the nervous system, causing numbness and tingling in the hands and feet. It also raises the risk of type 2 diabetes, cardiovascular disease, and several types of cancer.
Cancer Risk Persists for Decades
Arsenic’s connection to cancer is one of its most alarming features. A landmark study tracked residents of a region in northern Chile where drinking water was heavily contaminated with arsenic for roughly two decades before levels were reduced. Even 40 years after exposure dropped, lung and bladder cancer death rates in that population remained dramatically elevated. Men had more than three times the lung cancer mortality and nearly five times the bladder cancer mortality compared to the rest of the country. Women fared even worse for bladder cancer, with over six times the expected death rate. Kidney cancer rates were also roughly double.
These findings show that arsenic-related cancer risks have extremely long latency periods. The damage done during years of exposure can take decades to manifest as disease, even after the arsenic source is removed.
Common Sources of Exposure
The most widespread source of arsenic exposure globally is contaminated groundwater. Arsenic occurs naturally in rock and soil, and it leaches into underground water supplies. In parts of South and Southeast Asia, over 60% of wells have been found to exceed the World Health Organization’s limit of 10 micrograms per liter. The U.S. Environmental Protection Agency sets the same maximum for public water systems at 0.010 milligrams per liter (equivalent to 10 micrograms per liter), though the agency’s stated goal is zero.
Rice is a significant dietary source because rice plants absorb arsenic from soil and water more readily than most other crops. Rice grown in areas with naturally arsenic-rich soil, or in fields previously treated with arsenic-containing pesticides, can contain elevated levels of inorganic arsenic, the more toxic form. Other foods that may carry meaningful amounts include seafood, fruits, and vegetables grown in contaminated soil.
Industrial exposure also contributes. Burning coal releases arsenic into the air, and certain pesticides and herbicides have historically contained arsenic compounds. Workers in mining, smelting, and wood preservation industries face higher exposure risks.
How Arsenic Poisoning Is Diagnosed
Diagnosing arsenic poisoning relies on measuring arsenic levels in blood and urine. Normal blood arsenic should not exceed 50 micrograms per liter. In confirmed poisoning cases, blood levels commonly range from several hundred to several thousand micrograms per liter. A 24-hour urine collection is also useful: total arsenic excretion above 50 micrograms in 24 hours is considered abnormal and can both confirm a diagnosis and help monitor whether treatment is working.
If you suspect chronic exposure, your doctor may also look for the characteristic skin changes, nail lines, and nerve symptoms described above. These physical findings, combined with lab results and a history that suggests an arsenic source, form the basis of diagnosis.
Treatment Options
The most important step in any arsenic poisoning case is identifying and eliminating the source of exposure. For acute ingestion, the priority is stabilizing fluid loss and cardiovascular symptoms in a hospital setting.
Chelation therapy is the main medical treatment. Chelating agents are drugs that bind to arsenic in the bloodstream so the body can excrete it through urine. The currently recommended agents are DMPS and DMSA, which can be taken orally and have fewer side effects than older alternatives. Timing matters enormously: chelation is most effective when given within hours of ingestion. In animal studies, effectiveness drops sharply as the gap between exposure and treatment widens.
There are important limits to what chelation can do. It works best for acute poisoning caught early. If arsenic exposure has already caused nerve damage, chelation will not reverse it. All chelating agents carry their own side effects, so they’re used only when the poisoning is confirmed and significant enough to justify the risks.
For chronic low-level exposure, the treatment is primarily removing the arsenic source, whether that means switching to a filtered or alternative water supply, changing dietary patterns, or leaving a contaminated work environment. Skin changes from chronic exposure may persist even after arsenic levels normalize, and the long-term cancer risk, as the Chile data shows, can remain elevated for decades.