I noticed that Arsenic is in the water here in Prescott, AZ, so I am looking into it as a possible cause for my health problems.
Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. Arsenic is a metalloid. It can exist in various allotropes, although only the gray form has important use in industry.
The main use of metallic arsenic is for strengthening alloys of copper and especially lead (for example, in car batteries). Arsenic is a common n-type dopant in semiconductor electronic devices, and the optoelectronic compound gallium arsenide is the most common semiconductor in use after doped silicon. Arsenic and its compounds, especially the trioxide, are used in the production of pesticides, treated wood products, herbicides, and insecticides. These applications are declining, however.[6]
A few species of bacteria are able to use arsenic compounds as respiratory metabolites. Trace quantities of arsenic are an essential dietary element in rats, hamsters, goats, chickens, and presumably many other species, including humans. However, arsenic poisoning occurs in multicellular life if quantities are larger than needed. Arsenic contamination of groundwater is a problem that affects millions of people across the world.
Medical use
During the 18th, 19th, and 20th centuries, a number of arsenic compounds were used as medicines, including arsphenamine (by Paul Ehrlich) and arsenic trioxide (by Thomas Fowler).[55] Arsphenamine, as well as neosalvarsan, was indicated for syphilis and trypanosomiasis, but has been superseded by modern antibiotics.
Arsenic trioxide has been used in a variety of ways over the past 500 years, most commonly in the treatment of cancer, but in medications as diverse as Fowler's solution in psoriasis.[56] The US Food and Drug Administration in the year 2000 approved this compound for the treatment of patients with acute promyelocytic leukemia that is resistant to all-trans retinoic acid.[57]
Recently, new research has been done in locating tumors using arsenic-74 (a positron emitter). The advantages of using this isotope instead of the previously used iodine-124 is that the signal in the PET scan is clearer as the body tends to transport iodine to the thyroid gland producing signal noise.[58]
In subtoxic doses, soluble arsenic compounds act as stimulants, and were once popular in small doses as medicine by people in the mid-18th to 19th centuries.[9]
Essential trace element in higher animals
There is evidence for the essentiality of arsenic as a trace mineral in birds (chickens), and in mammals (rats, hamsters, and goats). However, the biological mechanism for its essential function is not known.[75]
Heredity
Arsenic has been linked to epigenetic changes, heritable changes in gene expression that occur without changes in DNA sequence. These include DNA methylation, histone modification, and RNA interference. Toxic levels of arsenic cause significant DNA hypermethylation of tumor suppressor genes p16 and p53, thus increasing risk of carcinogenesis. These epigenetic events have been studied in vitro using human kidney cells and in vivo using rat liver cells and peripheral blood leukocytes in humans.[76] Inductively coupled plasma mass spectrometry (ICP-MS) is used to detect precise levels of intracellular arsenic and its other bases involved in epigenetic modification of DNA.[77] Studies investigating arsenic as an epigenetic factor will help in developing precise biomarkers of exposure and susceptibility.
The Chinese brake fern (Pteris vittata) hyperaccumulates arsenic present in the soil into its leaves and has a proposed use in phytoremediation.[78]
Biomethylation
Inorganic arsenic and its compounds, upon entering the food chain, are progressively metabolized through a process of methylation.[79][80] For example, the mold Scopulariopsis brevicaulis produces significant amounts of trimethylarsine if inorganic arsenic is present.[81] The organic compound arsenobetaine is found in some marine foods such as fish and algae, and also in mushrooms in larger concentrations. The average person's intake is about 10–50 µg/day. Values about 1000 µg are not unusual following consumption of fish or mushrooms, but there is little danger in eating fish because this arsenic compound is nearly non-toxic.[82]
Environmental issues
Exposure
Other naturally occurring pathways of exposure include volcanic ash, weathering of arsenic-containing minerals and ores, and dissolved in groundwater. It is also found in food, water, soil, and air.[83] Arsenic is absorbed by all plants, but is more concentrated in leafy vegetables, rice, apple and grape juice, and seafood.[84] An additional route of exposure is through inhalation.[85]
Occurrence in drinking water
Main article: Arsenic contamination of groundwater
Extensive arsenic contamination of groundwater has led to widespread arsenic poisoning in Bangladesh[86] and neighboring countries. It is estimated that approximately 57 million people in the Bengal basin are drinking groundwater with arsenic concentrations elevated above the World Health Organization's standard of 10 parts per billion (ppb).[87] However, a study of cancer rates in Taiwan[88] suggested that significant increases in cancer mortality appear only at levels above 150 ppb. The arsenic in the groundwater is of natural origin, and is released from the sediment into the groundwater, owing to the anoxic conditions of the subsurface. This groundwater began to be used after local and western NGOs and the Bangladeshi government undertook a massive shallow tube well drinking-water program in the late twentieth century. This program was designed to prevent drinking of bacteria-contaminated surface waters, but failed to test for arsenic in the groundwater. Many other countries and districts in Southeast Asia, such as Vietnam and Cambodia have geological environments conducive to generation of high-arsenic groundwaters. Arsenicosis was reported in Nakhon Si Thammarat, Thailand in 1987, and the Chao Phraya River is suspected of containing high levels of naturally occurring dissolved arsenic, but has not been a public health problem owing to the use of bottled water.[89]
In the United States, arsenic is most commonly found in the ground waters of the southwest.[90] Parts of New England, Michigan, Wisconsin, Minnesota and the Dakotas are also known to have significant concentrations of arsenic in ground water.[91] Increased levels of skin cancer have been associated with arsenic exposure in Wisconsin, even at levels below the 10 part per billion drinking water standard.[92] According to a recent film funded by the US Superfund, millions of private wells have unknown arsenic levels, and in some areas of the US, over 20% of wells may contain levels that exceed established limits.[93]
Low-level exposure to arsenic at concentrations of 100 parts per billion (i.e., above the 10 parts per billion drinking water standard) compromises the initial immune response to H1N1 or swine flu infection according to NIEHS-supported scientists. The study, conducted in laboratory mice, suggests that people exposed to arsenic in their drinking water may be at increased risk for more serious illness or death in response to infection from the virus.[94]
Some Canadians are drinking water that contains inorganic arsenic. Private dug well waters are most at risk for containing inorganic arsenic. Preliminary well water analyses typically does not test for arsenic. Researchers at the Geological Survey of Canada have modelled relative variation in natural arsenic hazard potential for the province of New Brunswick. This study has important implications for potable water and health concerns relating to inorganic arsenic.[95]
Epidemiological evidence from Chile shows a dose-dependent connection between chronic arsenic exposure and various forms of cancer, in particular when other risk factors, such as cigarette smoking, are present. These effects have been demonstrated to persist below 50 ppb.[96]
Analyzing multiple epidemiological studies on inorganic arsenic exposure suggests a small but measurable risk increase for bladder cancer at 10 ppb.[97] According to Peter Ravenscroft of the Department of Geography at the University of Cambridge,[98] roughly 80 million people worldwide consume between 10 and 50 ppb arsenic in their drinking water. If they all consumed exactly 10 ppb arsenic in their drinking water, the previously cited multiple epidemiological study analysis would predict an additional 2,000 cases of bladder cancer alone. This represents a clear underestimate of the overall impact, since it does not include lung or skin cancer, and explicitly underestimates the exposure. Those exposed to levels of arsenic above the current WHO standard should weigh the costs and benefits of arsenic remediation.
Early (1973) evaluations of the removal of dissolved arsenic by drinking water treatment processes demonstrated that arsenic is very effectively removed by co-precipitation with either iron or aluminum oxides. The use of iron as a coagulant, in particular, was found to remove arsenic with efficiencies exceeding 90%.[99][100] Several adsorptive media systems have been approved for point-of-service use in a study funded by the United States Environmental Protection Agency (US EPA) and the National Science Foundation (NSF). A team of European and Indian scientists and engineers have set up six arsenic treatment plants in West Bengal based on in-situ remediation method (SAR Technology). This technology does not use any chemicals and arsenic is left as an insoluble form (+5 state) in the subterranean zone by recharging aerated water into the aquifer and thus developing an oxidation zone to support arsenic oxidizing micro-organisms. This process does not produce any waste stream or sludge and is relatively cheap.[101]
Another effective and inexpensive method to remove arsenic from contaminated well water is to sink wells 500 feet or deeper to reach purer waters. A recent 2011 study funded by the US National Institute of Environmental Health Sciences' Superfund Research Program shows that deep sediments can remove arsenic and take it out of circulation. Through this process called adsorption in which arsenic sticks to the surfaces of deep sediment particles, arsenic can be naturally removed from well water.[102]
Magnetic separations of arsenic at very low magnetic field gradients have been demonstrated in point-of-use water purification with high-surface-area and monodisperse magnetite (Fe3O4) nanocrystals. Using the high specific surface area of Fe3O4 nanocrystals the mass of waste associated with arsenic removal from water has been dramatically reduced.[103]
Epidemiological studies have suggested a correlation between chronic consumption of drinking water contaminated with arsenic and the incidence of all leading causes of mortality.[104] The literature provides reason to believe arsenic exposure is causative in the pathogenesis of diabetes.[105]
Hungarian engineer László Schremmer has recently discovered that by the use of chaff-based filters it is possible to reduce the arsenic content of water to 3 µg/L. This is especially important in areas where the potable water is provided by filtering the water extracted from the underground aquifer.[106]
San Pedro de Atacama
For several centuries, the people of San Pedro de Atacama in Chile have been drinking water that is contaminated with arsenic, and it is believed that they may have developed some immunity to the ill effects of consuming it.[107][108][109]
Toxicity and precautions
Main articles: Arsenic poisoning and Arsenic toxicity
Arsenic and many of its compounds are especially potent poisons.
Classification
Elemental arsenic and arsenic compounds are classified as "toxic" and "dangerous for the environment" in the European Union under directive 67/548/EEC. The International Agency for Research on Cancer (IARC) recognizes arsenic and arsenic compounds as group 1 carcinogens, and the EU lists arsenic trioxide, arsenic pentoxide and arsenate salts as category 1 carcinogens.
Arsenic is known to cause arsenicosis owing to its manifestation in drinking water, "the most common species being arsenate [HAsO2−
4; As(V)] and arsenite [H3AsO3; As(III)]".
Legal limits, food, and drink
In the United States, since 2006, the maximum concentration in drinking water allowed by the Environmental Protection Agency (EPA) is 10 ppb[128] and the FDA set the same standard in 2005 for bottled water.[129][130][unreliable source?] The Department of Environmental Protection for New Jersey set a drinking water limit of 5 ppb in 2006.[131] The IDLH (immediately dangerous to life and health) value for arsenic metal and inorganic arsenic compounds is 5 mg/m3. The Occupational Safety and Health Administration has set the permissible exposure limit (PEL) to a time-weighted average (TWA) of 0.01 mg/m3, and the National Institute for Occupational Safety and Health (NIOSH) has set the recommended exposure limit (REL) to a 15-minute constant exposure of 0.002 mg/m3.[132] The PEL for organic arsenic compounds is a TWA of 0.5 mg/m3.[133]
In 2008, based on its ongoing testing of a wide variety of American foods for toxic chemicals,[134] the U.S. Food and Drug Administration set 23 ppb as the "level of concern" for inorganic arsenic apple and pear juices based on non-carcinogenic effects, and began refusing imports and demanding recalls for domestic products exceeding this level.[129] In 2011, the national Dr. Oz television show broadcast a program highlighting tests performed by an independent lab hired by the producers. Though the methodology was disputed (it did not distinguish between organic and inorganic arsenic) the tests showed levels of arsenic up to 36 ppb.[135] In response, FDA testing of the worst brand from the Oz show showed much lower levels, and its ongoing testing found 95% of apple juice samples were below the level of concern. Later testing by Consumer Reports showed inorganic arsenic at levels slightly above 10 ppb, with the organization urging parents to reduce consumption.[136] In July 2013, after taking into account consumption by children, chronic exposure, and carcinogenic effect, the FDA established an "action level" of 10 ppb for apple juice, the same as the drinking water standard.[129]
Concern about arsenic in rice in Bangladesh was raised in 2002, but at the time only Australia had a legal limit for the level found in food (one milligram per kilogram).[137][138] The People's Republic of China has a food standard of 150 ppb for arsenic, as of 2011.[139] Further concern was raised about people who were eating U.S. rice exceeding WHO standards for personal arsenic intake in 2005.[140]
In the United States in 2012, testing by separate groups of researchers at the Children's Environmental Health and Disease Prevention Research Center at Dartmouth College (early in the year, focusing on urinary levels in children)[141] and Consumer Reports (in November)[142][143] found levels of arsenic in rice which resulted in calls for the FDA to set limits.[130] The FDA released some testing results in September 2012,[144][145] and as of July 2013 is still collecting data in support of a new potential regulation. It has not recommended any changes in consumer behavior.[146] Consumer Reports recommended that the EPA and FDA eliminate arsenic-containing fertilizer, drugs, and pesticides in food production; that the FDA establish a legal limit for food; that industry change production practices to lower arsenic levels, especially in food for children; and that consumers test home water supplies, eat a varied diet, and cook rice with excess water which is drained off (reducing inorganic arsenic by about one third along with a slight reduction in vitamin content).[143] Evidence-based public health advocates also recommend that, given the lack of regulation or labeling for arsenic in the U.S., children should eat no more than 1.5 servings per week of rice and should not drink rice milk as part of their daily diet before age 5.[147] They also offer recommendations for adults and infants on how to limit arsenic exposure from rice, drinking water, and fruit juice.[147]
A 2014 World Health Organization advisory conference will consider limits of 200–300 ppb for rice.[143]
Biological mechanism
The high affinity of arsenic(III) oxides for thiols is usually assigned as the cause of the high toxicity. Thiols, usually in the form of cysteine residues, but also in cofactors such as lipoic acid and coenzyme A, are situated at the active sites of many important enzymes.[6]
Arsenic disrupts ATP production through several mechanisms. At the level of the citric acid cycle, arsenic inhibits lipoic acid, which is a cofactor for pyruvate dehydrogenase. In addition, by competing with phosphate, arsenate uncouples oxidative phosphorylation, thus inhibiting energy-linked reduction of NAD+, mitochondrial respiration and ATP synthesis. Hydrogen peroxide production is also increased, which, it is speculated, has potential to form reactive oxygen species and oxidative stress. These metabolic interferences lead to death from multi-system organ failure. The organ failure is presumed to be from necrotic cell death, not apoptosis, since energy reserves have been too depleted for apoptosis to occur.[151]
Although arsenic causes toxicity it can also play a protective role.[152]
Exposure risks and remediation
Occupational exposure and arsenic poisoning may occur in persons working in industries involving the use of inorganic arsenic and its compounds, such as wood preservation, glass production, nonferrous metal alloys, and electronic semiconductor manufacturing. Inorganic arsenic is also found in coke oven emissions associated with the smelter industry.[153]
The ability of arsenic to undergo redox conversion between As(III) and As(V) makes its availability in the environment more abundant. According to Croal, Gralnick, Malasarn and Newman, "[the] understanding [of] what stimulates As(III) oxidation and/or limits As(V) reduction is relevant for bioremediation of contaminated sites (Croal). The study of chemolithoautotrophic As(III) oxidizers and the heterotrophic As(V) reducers can help the understanding of the oxidation and/or reduction of arsenic.[154] It has been proposed that As (III) which is more toxic than Arsenic (V) can be removed from the ground water using baker's yeast Saccharomyces cerevisiae.[155]
Treatment
Treatment of chronic arsenic poisoning is possible. British anti-lewisite (dimercaprol) is prescribed in doses of 5 mg/kg up to 300 mg every 4 hours for the first day, then every 6 hours for the second day, and finally every 8 hours for 8 additional days.[156] However the USA's Agency for Toxic Substances and Disease Registry (ATSDR) states that the long-term effects of arsenic exposure cannot be predicted.[85] Blood, urine, hair, and nails may be tested for arsenic; however, these tests cannot foresee possible health outcomes from the exposure.[85] Excretion occurs in the urine and long-term exposure to arsenic has been linked to bladder and kidney cancer in addition to cancer of the liver, prostate, skin, lungs, and nasal cavity.[157]
Conclusion:
Avoid drinking water, and eating food, that are contaminated with high levels of arsenic.
