Arsenic

In general, hair provides a rough estimate of exposure to Arsenic absorbed from food and water. However, hair can be contaminated externally with Arsenic from air, water, dust, shampoos and soap. Inorganic Arsenic, and some organic Arsenic compounds, can be associated with toxicity. Inorganic Arsenic accumulates in hair, nails, skin, thyroid gland, bone and the gastrointestinal tract. Organic Arsenic, such as that derived from shellfish, is rapidly excreted in the urine.

Arsenic can cause malaise, muscle weakness, vomiting, diarrhea, dermatitis, and skin cancer. Long-term exposure may affect the peripheral nervous, cardiovascular and hematopoietic systems. Arsenic is a major biological antagonist to selenium. Common sources of Arsenic are insecticides (calcium and lead arsenate), drinking water, smog, shellfish (arsenobetaine), and industrial exposure, particularly in the manufacture of electronic components (gallium arsenide). Arsenic burden can be confirmed by urine elements analysis. Comparison of urine Arsenic levels pre and post provocation (DMPS, DMSA, D-penicillamine) permit differentiation between recent uptake and body stores.

Having no detectable arsenic levels in hair is generally a positive thing, as arsenic is a toxic element that can have harmful effects on human health. Arsenic exposure, often through contaminated water, food, or environmental sources, has been linked to various health problems, including skin lesions, cardiovascular diseases, neurological issues, and an increased risk of certain types of cancer.

Hair can serve as a medium to assess past exposure to certain elements, including arsenic. However, the absence of detectable arsenic levels in hair doesn't necessarily mean that a person has never been exposed to arsenic, as the levels can vary based on factors like the timing and extent of exposure. It's important to note that a lack of detectable arsenic in hair does not guarantee complete absence of exposure in the past.

Arsenic circulating in the blood will bind to protein by formation of a covalent complex with sulfhydryl groups of the amino acid cysteine. Keratin, the major structural protein in hair and nails, contains many cysteine residues and, therefore, is one of the major sites for accumulation of arsenic. Since arsenic has a high affinity for keratin, the concentration of arsenic in hair is higher than in other tissues. Arsenic binds to keratin at the time of exposure, "trapping" the arsenic in hair. Therefore, hair analysis for arsenic is not only used to document that an exposure occurred, but when it occurred. Hair collected from the nape of the neck can be used to document recent exposure. Axillary or pubic hair is used to document long-term (6 months-1 year) exposure.