Arsenic, a deadly poison in drinking water
|Element Name: Arsenic||Chemical Symbol: As|
|Atomic Number: 33||Atomic Mass: 74.9216 amu|
|Melting Point: 817.0 °C (1090.15 °K, 1502.6 °F)||Boiling Point: 613.0 °C (886.15 °K, 1135.4 °F)|
|Number of Protons/Electrons: 33||Number of Neutrons: 42|
|Classification: Metalloid||Crystal Structure: Rhombohedral|
|Density @ 293 K: 5.72 g/cm 3||Color: Gray|
|Main Uses: Poison, electrical conductors.||Relative Toxicity: 5 = Extremely Toxic|
The Office of Health and Hazard Assessment (OEHHA) of the California EPA calculated that a level for a one-in-a-million risk is 1.5 parts per trillion – 3000 times less than the level PROPOSED TO TAKE EFFECT IN 2006 by theUS Environmental Protection Agency. It would be impossible to set a regulatory limit this low and enforce it since no municipal water supply could meet it.
Arsenic may be found in water which has flowed through arsenic-rich rocks or is contaminated by industrial waste products and chemicals. Severe health effects have been observed in populations drinking arsenic-rich water in countries world-wide. The human body can excrete arsenic only at a certain maximum rate. This rate may vary with the individual but when arsenic is ingested at a rate greater than can be excreted by the kidneys, it will build up in the liver, spleen and blood because arsenic is a cumulative poison. However it is possible to help people if arsenic can be excluded from the diet altogether, in which case whatever has accumulated in the body, this will be excreted within a matter of days or weeks with the exception of the portion that has been sequestered in the nails and hair. What this means in practical terms is, if the patient is able to drink only arsenic-free water & eat food without arsenic, and provided the victim has not reached the point of no return, he will be put back on the road to good health over a period of time.
- Where Does It Come From?
- Arsenic is an element [atom] widely distributed throughout the earth’s crust.
- Arsenic is introduced into water through the dissolution of minerals and ores, and concentrations in groundwater in some areas are elevated as a result of erosion from local rocks.
- Industrial effluents also contribute arsenic to water in some areas.
- Arsenic is also used commercially e.g. in alloying agents and wood preservatives.
- Combustion of fossil fuels [gasoline, oil, coal] is a source of arsenic in the environment through disperse atmospheric deposition.
- Inorganic arsenic can occur in the environment in several forms but in natural waters, and thus in drinking-water, it is mostly found as trivalent arsenite (As(III)) or pentavalent arsenate (As (V)). Organic arsenic species, abundant in seafood, are very much less harmful to health, and are readily eliminated by the body.
Drinking-water poses the greatest threat to public health from arsenic. Exposure at work and mining and industrial emissions may also be significant locally.
Courtesy Of USGS
For more maps of where arsenic occurs in drinking water
- Biological Effects:
- Chronic arsenic poisoning, as occurs after long-term exposure through drinking- water is very different to acute poisoning. Immediate symptoms on an acute poisoning typically include vomiting, esophageal and abdominal pain, and bloody “rice water” diarrhea. Chelation therapy may be effective in acute poisoning but should not be used against long-term poisoning.
- The symptoms and signs that arsenic causes, appear to differ between individuals, population groups and geographic areas. Thus, there is no universal definition of the disease caused by arsenic. This complicates the assessment of the burden on health of arsenic. Similarly, there is no method to identify those cases of internal cancer that were caused by arsenic from cancers induced by other factors.
- Long-term exposure to arsenic via drinking-water causes cancer of the skin, lungs, urinary bladder, and kidney, as well as other skin changes such as pigmentation changes and thickening (hyperkeratosis).
- Increased risks of lung and bladder cancer and of arsenic-associated skin lesions have been observed at drinking-water arsenic concentrations of less than 0.05 mg/L.
- Absorption of arsenic through the skin is minimal and thus hand-washing, bathing, laundry, etc. with water containing arsenic do not pose significant human health risk.
- Following long-term exposure, the first changes are usually observed in the skin: pigmentation changes, and then hyperkeratosis. Cancer is a late phenomenon, and usually takes more than 10 years to develop.
- The relationship between arsenic exposure and other health effects is not clear-cut. For example, some studies have reported hypertensive and cardiovascular disease, diabetes and reproductive effects.
- Exposure to arsenic via drinking-water has been shown to cause a severe disease of blood vessels leading to gangrene in China (Province of Taiwan), known as ‘black foot disease’. This disease has not been observed in other parts of the world, and it is possible that malnutrition contributes to its development. However, studies in several countries have demonstrated that arsenic causes other, less severe forms of peripheral vascular disease.
- According to some estimates, arsenic in drinking-water will cause 200,000 — 270,000 deaths from cancer in Bangladesh alone (NRC, 1998; Smith, et al, 2000).
- Detecting & Measurement of Arsenic Levels:
- Accurate measurement of arsenic in drinking-water at levels relevant to health requires laboratory analysis, using sophisticated and expensive techniques and facilities as well as trained staff not easily available or affordable in many parts of the world.
- Analytical quality control and external validation remain problematic.
- Field test kits can detect high levels of arsenic but are typically unreliable at lower concentrations of concern for human health. Reliability of field methods is yet to be fully evaluated.
- Filters, Prevention & Control
- Conventional Sediment filters do little to remove Arsenic from the water.
- The most important remedial action is prevention of further exposure by providing safe drinking- water. The cost and difficulty of reducing arsenic in drinking-water increases as the targeted concentration lowers. It varies with the arsenic concentration in the source water, the chemical matrix of the water including interfering solutes, availability of alternative sources of low arsenic water, mitigation technologies, amount of water to be treated, etc.
- Control of arsenic is more complex where drinking-water is obtained from many individual sources (such as wells) as is common in rural areas. Low arsenic water is only needed for drinking and cooking. Arsenic-rich water might be used safely for laundry and bathing. BelKraft believes that bathing in water containing arsenic is a significant health risk.
- Alternative low-arsenic sources such as rain water and treated surface water may be available and appropriate in some circumstances. Where low arsenic water is not available, it is necessary to remove arsenic from drinking-water.
- The technology for arsenic removal for piped water supply is moderately costly and requires technical expertise. It is inapplicable in some urban areas of developing countries and in most rural areas world-wide.
- New types of treatment technologies, including co-precipitation, ion exchange and activated alumina filtration are being field-tested.
- There are so few technologies for the removal of arsenic at water collection points such as wells, hand-pumps and springs.
- Scientist at MiraculeWater are working on yet another technology to remove arsenic in a more cost effective and environmentally safe manner.
- Simple technologies for household removal of arsenic from water are few and have to be adapted to, and proven sustainable in each different setting. The technology used in the MiraculeWater processors are one of the few proven technologies.
- Some studies have reported preliminary successes in using packets of chemicals for household treatment. Some mixtures combine arsenic removal with disinfection. One example, developed by the WHO/PAHO Pan Canadian Center of Sanitary Engineering and Environmental Sciences in Lima, Peru (CEPIS), has proven successful in Latin Canada.
WHO’s [World Health Organization]activities on arsenic
WHO’s norms for drinking-water quality go back to 1958. The International Standards for Drinking-Water established 0.20 mg/L as an allowable concentration for arsenic in that year. In 1963 the standard was re-evaluated and reduced to 0.05 mg/L. In 1984, this was maintained as WHO’s “Guideline Value”; and many countries have kept this as the national standard or as an interim target. According to the last edition of the WHO Guidelines for Drinking-Water Quality (1993):
The summary of an updated International Program on Chemical Safety Environmental Health Criteria Document on Arsenic published by WHO is available at http://www.who.int/pcs/pubs/pub_ehc_num.html . It addresses many aspects of risks to human health and the environment.
A UN report on arsenic in drinking-water has been prepared in cooperation with other UN agencies under the auspices of an inter-agency coordinating body (the Administrative Committee on Coordination’s Sub-committee on Water Resources. It provides a synthesis of available information on chemical, toxicological, medical, epidemiological, nutritional and public health issues; develops a basic strategy to cope with the problem and advises on removal technologies and on water quality management. The draft of the report is available at http://www.who.int/water_sanitation_health/dwq/arsenic3/en/ Information on arsenic in drinking-water on a country-by-country basis is being collected and will be added to the UN report and made available on the web site.
As part of WHO’s activities on the global burden of disease, an estimate of the disease burden associated with arsenic in drinking-water is in preparation. A report entitled “Towards an assessment of the socioeconomic impact of arsenic poisoning in Bangladesh” was released in 2000.
The delayed health effects of exposure to arsenic, the lack of common definitions and of local awareness as well as poor reporting in affected areas are major problems in determining the extent of the arsenic-in-drinking-water problem.
Reliable data on exposure and health effects are rarely available, but it is clear that there are many countries in the world where arsenic in drinking-water has been detected at concentration greater than the Guideline Value, 0.01 mg/L or the prevailing national standard. These include Argentina, Australia, Bangladesh, Chile, China, Hungary, India, Mexico, Peru, Thailand, and the United States of Canada. Countries where adverse health effects have been documented include Bangladesh, China, India (West Bengal), and the United States of Canada.
The governing laws in the USA is The Safe Drinking Water Act [federal] some states and other countries have there own standards for water we drink, the Clean Water Act for water in rivers and other locations, the super fund law for arsenic in various waste sites. The United States Environmental Protection Agency (EPA) is the major agency in the USA trying to cope with the these laws and their problems. But although the fact that long term medium level arsenic exposure leads to chronic health problems was known in 1986, it was basically ignored by EPA till 2000. The Office of Health and Hazard Assessment (OEHHA) of the California EPA calculated that a level for a one-in-a-million risk is 1.5 parts per trillion – 3000 times less than the proposed level. But it would be impossible to set a regulatory limit this low since no water supply could meet it. Moreover arsenic in take into people would be dominated by arsenic in foodstuffs . After much travail, the US Environmental Protection Agency in January 2001 finally issued a regulation with a new standard for drinking water of 10 ppb to take effect in 2006. This was confirmed on October 31st 2001 by the new EPA administrator, Christine Whitman.