Arsenic poisoning is a serious health concern resulting from exposure to elevated levels of arsenic, a naturally occurring metalloid. While arsenic is present in the environment at low levels, excessive intake can lead to adverse health effects. Hair serves as a unique biological indicator for arsenic exposure, providing a historical record due to its ability to incorporate and store the element as it grows.
How Arsenic Accumulates in Hair
Once absorbed, arsenic circulates in the blood and binds to proteins, particularly those rich in cysteine. Keratin, the primary protein in hair and nails, contains numerous cysteine residues, making it a major site for arsenic accumulation. As hair follicles synthesize keratin, arsenic incorporates into the hair shaft.
Hair offers a more permanent record of exposure compared to blood or urine, which reflect more recent intake. Hair grows at about 0.5 inches (1.27 cm) per month, allowing for segmental analysis. This means different sections of hair can indicate exposure levels at various points in time. For example, hair near the scalp reflects recent exposure, while sections further down the shaft can indicate exposure from months prior.
Recognizing Arsenic Poisoning Symptoms
Arsenic poisoning symptoms vary with exposure duration and level. Acute exposure can cause rapid gastrointestinal issues like nausea, vomiting, and diarrhea. Neurological symptoms such as weakness, muscle cramps, and tingling in the fingers and toes (neuropathy) may also develop.
Chronic arsenic exposure, developing over months or years, presents with more distinct signs. Skin changes are common, including hyperpigmentation (darkening of the skin) appearing as diffuse darkening or “raindrop” spots, especially on the chest, back, and limbs. Hyperkeratosis, or hardened skin patches on palms and soles, is also frequent. Hair changes can include diffuse hair loss, while nails may show transverse white bands known as Mee’s lines, appearing about 3-6 weeks after exposure.
Hair Analysis for Detection
Hair analysis is a valuable, non-invasive method for detecting arsenic exposure, especially for chronic or past incidents. Samples are typically collected by cutting a pencil-thick segment of hair, usually from the nape of the neck, beard, mustache, chest, or pubic area. Approximately 0.2 to 0.5 grams are needed for analysis. The root end should be identified for proper interpretation of the exposure timeline.
Once collected, hair samples undergo preparation, often involving washing to remove external contaminants, then digestion using strong acids to break down the hair matrix. The prepared samples are analyzed using highly sensitive techniques like Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) or Atomic Absorption Spectrometry (AAS). These methods quantify trace amounts of arsenic, providing a record of exposure over several months—a longer window than blood or urine tests. Hair arsenic levels above 1.00 micrograms per gram of dry weight may indicate excessive exposure.
Common Sources of Arsenic Exposure
People encounter arsenic from both natural and human-made sources. Naturally, arsenic is found in the Earth’s crust, present in rocks, soil, and groundwater in many global regions, including parts of Argentina, Bangladesh, China, India, Mexico, and the United States. Contaminated drinking water from these natural geological formations is a primary route of exposure worldwide.
Human activities also contribute to arsenic exposure. Industrial processes like mining, metal smelting, and burning fossil fuels release arsenic into the air, water, and soil. Historically, arsenic was used in pesticides, herbicides, and wood preservatives, contaminating agricultural lands and treated wood products. Certain traditional medicines and contaminated food, especially rice grown in arsenic-rich water or soil, can also be sources.
Treatment and Recovery
Managing arsenic poisoning begins with immediately removing the individual from the source to prevent further intake. Medical intervention typically involves supportive care for symptoms like gastrointestinal distress and neurological effects. For instance, fluid and electrolyte replacement can manage severe vomiting and diarrhea.
For significant arsenic intoxication, especially acute poisoning, chelation therapy may be considered. Chelating agents like dimercaprol (BAL), meso-2,3-dimercaptosuccinic acid (DMSA), or sodium 2,3-dimercapto-1-propanesulfonate (DMPS) bind to arsenic, forming complexes readily excreted, primarily through urine. Chelation therapy is most effective when initiated rapidly, within hours of exposure, as its efficacy decreases once arsenic distributes into tissues. Recovery from neuropathy can be slow, sometimes taking years, and complete recovery may not always occur.