Arsenic drinking water regulations in developing countries with extensive exposure
The United States Public Health Service set an interim standard of 50microg/l in 1942, but as early as 1962 the US Public Health Service had identified 10microg/l as a goal which later became the World Health Organization Guideline for drinking water in 1992. Epidemiological studies have shown that about one in 10 people drinking water containing 500microg/l of arsenic over many years may die from internal cancers attributable to arsenic, with lung cancer being the surprising main contributor. A prudent public health response is to reduce the permissible drinking water arsenic concentrations. However, the appropriate regulatory response in those developing countries with large populations with much higher concentrations of arsenic in drinking water, often exceeding 100microg/l, is more complex.
Malnutrition may increase risks from arsenic. There is mounting evidence that smoking and arsenic act synergistically in causing lung cancer, and smoking raises issues of public health priorities in developing countries that face massive mortality from this product. Also, setting stringent drinking water standards will impede short term solutions such as shallow dugwells. Developing countries with large populations exposed to arsenic in water might reasonably be advised to keep their arsenic drinking water standards at 50microg/l (Smith AH and Smith MM. Toxicology, 198(1-3): 39-44, 2004.) .
May 2000: Proposed Revision to Arsenic Drinking Water Standard
EPA (USA) is proposing to reduce the public health risks from arsenic in drinking water. The Agency is proposing to change the current arsenic standard from 50 parts per billion (ppb) to 5 ppb in drinking water. This proposed revision will provide additional protection for 22.5 million Americans from cancer and other health problems, including cardiovascular disease and diabetes, as well as developmental and neurological effects.
Water as a human right features in various international declarations and conventions. Here are a few:
Article 25 of the Universal Declaration of Human Rights (1948) states:
"Everyone has the right to a standard of living adequate for the health and well-being of himself and of his family, including food, clothing, housing..."
Article 12 of the International Covenant on Economic, Social and Cultural Rights (1956) states:
"The states' parties to the present Covenant recognize the right of everyone to the enjoyment of the highest attainable standard of physical and mental health. The steps to be taken . . . to achieve the full realization of this right shall include those necessary for... the prevention, treatment and control of epidemic, endemic, occupational and other diseases." Article 24 of the Convention of the Rights of the Child (1989) provides that a child has the right to enjoy the highest attainable standard of health. Among the measures states are to take to secure this right are measures to: "combat disease and malnutrition . . . through, inter alia, . . the provision of adequate nutritious foods and clean drinking water."
Proposed Arsenic rule (June 22, 2000)
Long term exposure to low concentrations of arsenic in drinking water can lead to skin, bladder, lung, and prostate cancer. Non-cancer effects of ingesting arsenic at low levels include cardiovascular disease, diabetes, and anemia, as well as reproductive and developmental, immunological, and neurological effects. Short-term exposure to high doses of arsenic can cause other adverse health effects, but such exposures do not occur from U.S. public water supplies at the current standard of 50 ppb.
The current standard of 50 ppb was set by EPA in 1975, based on a Public Health Service standard originally established in 1942. A March 1999, report by the National Academy of Sciences concluded that the current standard does not achieve EPA's goal of protecting public health and should be lowered as soon as possible. Under the Safe Drinking Water Act Amendments of 1996, EPA is required to promulgate a final rule by January 1, 2001.
EPA is proposing to change the arsenic standard in drinking water to 5 ppb to more adequately protect public health. The proposed arsenic standard is intended to protect consumers against the effects of long-term, chronic exposure to arsenic in drinking water. The new standard will apply to all 54,000 community water systems, serving approximately 254 million people. A community water system is a system that serves 15 locations or 25 residents year-round (e.g. most cities and towns, apartments, and mobile home parks with their own water supplies). EPA estimates, however, that only 12 percent, or 6,600, of these water systems, serving 22.5 million people, will have to take corrective action to lower the current levels of arsenic in their drinking water. Of the affected systems, 94 percent serve fewer than 10,000 people.
EPA is taking comment on other proposed levels for arsenic. EPA is for the first time proposing a drinking water standard (5 ppb) that is higher than the technically feasible level (3 ppb). The Safe Drinking Water Act (SDWA) requires EPA to determine the health goal, then to set the standard as close to the goal as technically feasible. The 1996 Amendments to SDWA for the first time granted EPA discretionary authority, if it determines that the technically feasible level does not justify the costs, to adjust the standard to a level "that maximizes health risk reduction benefits at a cost that is justified by the benefits.Under this proposal, water systems that serve at least 25 of the same people more than six months per year, such as schools, churches, nursing homes, and factories would be required to notify their consumers if the arsenic levels in their drinking water exceed the new arsenic standard.
EPA is also proposing a public health goal of zero for arsenic. The health goal is the level below which no known or anticipated health effects would occur. EPA sets public health goals at zero for all known carcinogens for which there is no dose considered safe.
Arsenic occurs naturally in rocks and soil, water, air, and plants and animals. It can be further released into the environment through natural activities such as volcanic action, erosion of rocks, and forest fires, or through human actions. Approximately 90 percent of industrial arsenic in the U.S. is used as a wood preservative, but arsenic is also used in paints, dyes, metals, drugs, soaps, and semi-conductors. Burning fossil fuels, paper production, cement manufacturing, and mining can also release arsenic into the environment.
While many systems may not have detected arsenic in their drinking water above 5 ppb, there may be "hot spots" with systems higher than the predicted occurrence for an area. More water systems in western states that depend on underground sources of drinking water have naturally-occurring levels of arsenic at levels greater than 10 ppb than in other parts of the U.S. Parts of the Midwest and New England have some systems whose current arsenic levels range from 2-10 ppb.
Carcinogen Category 1
(Confirmed Human Carcinogen)
CAS RegistNumber: 7440-38-2 Molecula Formula: As (Arsenic), As(+3) (Arsenites), As(+5)(Arsenates)
Arsenic exists in several forms which vary in toxicity and occurrence. Accordingly, for this proposed regulation, it is important to consider those forms that can exert toxic effects and to which people may be exposed. For example, the metallic form of arsenic (0 valence) is not absorbed from the stomach and intestines and does not exert adverse effects. On the other hand, a volatile compound such as arsine (AsH3) is toxic, but is not present in water or food. Moreover, the primary organic forms (arsenobetaine and arsenocholine) found in fish and shellfish seem to have little or no toxicity (Sabbioni et al., 1991). Arsenobetaine quickly passes out of the body in urine without being metabolized to other compounds (Vahter, 1994). Arsenite (+3) and arsenate (+5) are the most prevalent toxic forms of inorganic arsenic that are found in drinking water (EPA June 2000).
2. CHEMICAL AND PHYSICAL PROPERTIES
Arsenic is an element with atomic number of 33. The most common form of the element is a silver-grey brittle crystalline solid. Given below are some of its properties:
Atomic weight 74.9 Specific gravity: 5.73 Melting point 817°C at 28atm Boiling point: 613°C (sublimes) Vapour pressure: 1mm Hg at 372°C
When arsenic is heated in air, it will burn and form a white smoke consisting of arsenic trioxide (As203).
3. MAJOR INDUSTRIAL USES
Elemental or metallic arsenic is utilised as an alloying agent for heavy metals, in special solders, and as a doping agent in silicon and germanium solid state products.
Many arsenic compounds have found commercial applications. The arsenites (trivalent arsenic compounds, for example, calcium arsenite) are important herbicides and wood preservatives. Some arsenates (pentavalent arsenic compounds, for example, calcium arsenate) are used as insecticides and pigments. Many organic compounds have been employed in medicine, or as war gases.
4. GENERAL HEALTH EFFECTS
4.1 Acute Effects
Acute arsenical poisoning due to inhalation is exceedingly rare in the workplace. When it does occur, it produces respiratory tract symptoms (cough, chest pain and dyspnoea), giddiness, headache, and extreme general weakness, followed by gastrointestinal symptoms including epigastric pain, vomiting and diarrhoea.
4.2 Chronic Effects
Chronic signs of toxicity in workers exposed to arsenic compounds are related chiefly to the skin, mucous membranes, gastrointestinal and nervous systems, and far less commonly to disorders of the circulatory system and liver Chronic poisoning from inhalation exposure has been described as having three phases based on signs and symptoms
First phase: The worker complains of weakness, loss of appetite, some nausea, occasional vomiting, a sense of heaviness in the stomach, and some diarrhoea.
Second Phase: The worker complains of conjunctivitis, and a catarrhal state of the mucous membranes of the nose, larynx and respiratory passages. Coryza, hoarseness, and mild tracheobronchitis may occur. Perforation of the nasal septum is common, and is probably the most typical lesion of the upper respiratory tract in occupational exposure to arsenical dust. Skin lesions, eczematoid and allergic in type, are common.
Third Phase: The worker complains of symptoms of peripheral neuritis, initially of hands and feet, which is essentially sensory. In more severe cases, motor paralyses occur; the first muscles affected are usually the toe extensors and the peronei. In only the most severe cases will paralysis of flexor muscles of the feet or the extensor muscles of hands occur.
5. METABOLISM AND ABSORPTION
Airborne arsenic particles deposited in the respiratory tract seem to be rapidly taken up from the lung; however, their absorption rates are not known in humans . Most arsenic derivatives are rapidly excreted in the urine but some of the absorbed arsenic is widely distributed in the tissues including the liver, abdominal viscera, bone, skin, and particularly the hair and nails
Teratogenic effects of arsenic have frequently been reported in laboratory animals exposed to single high doses Schroeder & Mitchener exposed three generations of mice to low doses of arsenic (5mg As/kg diet), but did not find any abnormalities other than reduced litter size.
Human data on the teratogenicity of arsenic are very rare and the data available are usually confounded by variables such as exposure to other metals. However, as inorganic arsenic crosses the human placenta and there is evidence of teratogenesis at high doses in animals, arsenic at high doses should be considered a potential teratogen in humans.
A number of studies have indicated an effect of arsenic on human chromosomes, both in vivo and in vitro. There is evidence that in experimental systems it induces chromosome aberrations and sister chromatid exchanges and that it affects DNA repair mechanisms. However, there is no evidence available to correlate these effects with levels of workplace exposure.
Epidemiological studies clearly indicate that exposure to arsenic increases the incidence of skin, lung, liver and lymphoid cancer in humans . However, as animal studies designed to confirm the carcinogenic potential of arsenic have been largely negative, the question as to whether it is a direct carcinogen is unresolved. It has been proposed that it may be a co-promotor or co-carcinogen (that is, a potentiator of the carcinogenic process).
Lung cancer is the primary cause of concern with chronic inhalation of arsenic in the workplace. An excess of deaths due to respiratory cancer has been observed among workers exposed to inorganic arsenic in the production and use of pesticides, gold mining, and in the smelting of nonferrous metals, especially copper .
The uncertainty involved in estimating past exposure in epidemiological studies makes it difficult to relate risk to exposure levels. However, a number of organisations have undertaken detailed analyses of these studies and have produced the following assessments of elevated risk:
5% per ug As/m3after 30 years exposure
0.8% and 0.6% per ug As/m3after 25 years exposure
0.8% per ug As/m3after 25 years exposure
9. OVERSEAS EXPOSURE STANDARDS
In Bangladesh the standard is 50µg/l. On the basis of risk assessment, both OSHA(U.S.) and NIOSH (U.S.) have recommended an exposure standard of 10ug/m3 (as As) for inorganic arsenic. Ontario (Canada) has adopted a TWA of 10ug/m3 and a 15-minute standard of 50ug/m3 with an exemption for the construction and mining industries. Sweden's standard is set at 50ug/m3. The HSE (U.K.) has adopted a maximum exposure limit of 200ug/m3, pending consideration of the impact of a 50ug/m3 limit on the industry. The ACGIH, in adopting a TLV of 200ug/m3, however, stated that as there was a lack of data on which to unequivocally base an exposure standard, there were insufficient grounds to reduce the TLV (13) . Levels set in a number of other countries are equal to or greater than that set by the ACGIH.
10. RECOMMENDATIONS FOR EXPOSURE STANDARD
After reviewing the relevant data, the Exposure Standards Working Group recommends that arsenic and its soluble compounds be assigned the designation Carcinogen Category 1 (Confirmed Human Carcinogen). The reader is encouraged to review the section on Carcinogens in the Guidance Note on the Interpretation of Exposure Standards for Atmospheric Contaminants in the Occupational Environment, for guidance on the classification system of carcinogens.
The Working Group also recommends a time-weighted average exposure standard of 0.05mg/m3 (as As), believing that according to risk assessment, this level can significantly reduce the number of cases of cancer resulting from exposure to arsenic.
Stakeholder's Meeting: Arsenic in Drinking Water
Tuesday, May 5, 1998, Monterey, California
The Office of Ground Water and Drinking Water (OGWDW) in EPA holds stakeholder meetings to help refocus priorities in the drinking water program and to improve strong, flexible relationships among EPA, States, Tribes, local governments, water utilities, and the public. OGWDW held an arsenic stakeholders meeting in Monterey, California, prior to the semi-annual Association of California Water Agencies (ACWA) meeting. EPA outlined the statutory requirements, research activities, the regulatory approach, policy issues and ongoing arsenic work in order to solicit input and obtain continued stakeholder involvement in the arsenic regulatory development process.
Regulatory History and Future. EPA's primary drinking water regulation for arsenic, the Maximum Contaminant Level (MCL) of 50 g/L, was first used in 1943 by the Public Health Service. In the early 1990's EPA delayed revising the MCL because of cost and risk assessment considerations. In the 1996 amendments to the Safe Drinking Water Act (SDWA), Congress directed EPA to write an arsenic research plan, expand health effects research, and propose a new regulation for arsenic by January 1, 2000. Therefore, EPA will use current and future arsenic research, to the extent available, to meet the statutory deadlines. Focused long-term arsenic research efforts will be applied in future reviews of the regulation, which will be re-evaluated every 6 years (or sooner, if warranted). A meeting participant stated the need for EPA to track on-going research so stakeholders can understand what information will be available.
Arsenic Research Plan
The arsenic research plan is the framework for EPA's in-house and external research and others to improve the basis for regulatory decisions on arsenic health risks. The plan identifies short-term (supporting the January 1, 2000 proposal) and longer-term studies of exposure and susceptibility, analytical methods, cancer and non-cancer health effects, and risk assessment. Short-term risk management research involves studies of arsenic control technologies. Long-term outcomes will be in the areas of bioavailability assessment, dose response interactions, and epidemiological study gaps. The draft plan submitted for peer review in 1998 is now final, and is at www.epa.gov/ORD/WebPubs/final/arsenic.pdf. Stakeholders found out that all research used by EPA, including short-term research, will undergo peer review that meets EPA standards. Stakeholders noted the emphasis on arsenic research, and EPA mentioned research studies of other chemicals. People discussed small system access to hard copies of information and representation in consultations with small entities. Stakeholders expressed interest in reviewing the risk assessment.
EPA Health Effects Research--Current and Future. Arsenic is a known human carcinogen that can also produce non-cancer effects including dermal, neurological, cardiovascular, and reproductive/developmental effects. Risk assessment issues include the determination of a linear or non-linear dose response curve; epidemiology studies to assess exposure, dose-response, and health effects; and better understanding of arsenic metabolism and mode of action. EPA presented ongoing U.S. health and exposure studies and international collaborations which will provide the greatest returns beyond the year 2000 by reducing uncertainties in quantitative estimates and understanding health effect endpoints. Stakeholders asked how international studies related to U.S. populations and what would be peer reviewed in early 1999. Stakeholders commented that the scientific language needed to be made more understandable for the general public.
Analytical Methods and Monitoring. EPA reviewed currently approved analytical methods that measure total arsenic which have performance evaluation data to help derive a practical quantization level (PQL). Analytical capability is only one aspect considered in setting an MCL, so the MCL is not set purely on the basis of the lowest value that can be measured. ORD research involves speciation analysis in water, food, and urine. EPA provided background on current monitoring requirements for arsenic, the standardized monitoring framework for other inorganic chemicals, and chemical monitoring reform (CMR) efforts. Stakeholders asked about previous efforts to redefine PQL, preservation of arsenic valences, trigger values for monitoring under the CMR, alternative monitoring guidelines, private certification of laboratories, cost of methods, and quality assurance and control.
Treatment Technology. EPA presented an overview of seven treatment options, the point-of-use and point-of-entry devices that are now options for small systems, EPA's ORD work on technologies and waste disposal; and granting variances. Future ORD work will include performance evaluation of full scale systems, oxidation of arsenic, and reporting on the February 25 arsenic "state of the science" treatment workshop. ORD's residual disposal studies will complement a new AWWA Research Foundation (AWWARF) residual study. EPA discussed the national level affordability-based variances for small systems. Participants mentioned a few experimental technologies. EPA mentioned local pretreatment programs and state water quality standards. Stakeholders mentioned increased water usage and water costs from adding treatments, increased salinity in ground water recharge, treatment costs, affordability, the small percent used for drinking water, combined cost of compliance of several new MCLs, cost of site acquisition, and blending. Others had questions on levels of treatment and bottled water in the work place.
Occurrence Data. EPA discussed the databases used to draft national arsenic occurrence projections in 1992. New sources of occurrence data include 25 State databases, four industry surveys, and the U.S. Geological Survey (USGS) ambient ground water database (scheduled for release in fall 1998). EPA will evaluate the quality of the data, develop statistical methods, and establish occurrence and exposure projections to assess costs and benefits. Stakeholders were requested to comment on how EPA should combine databases. The group discussed several of the databases and offered to provide additional data. The USGS ambient ground water database will be linked by county to populations served and may also assist in evaluating treatment costs. Stakeholders asked about the USGS analytical method, well depth and concentration analysis, and water use information.
MCLG Development, Revisions, and Peer Reviews. For most people exposure to arsenic is primarily from ingestion of food and water. An increased understanding of arsenic-induced carcinogenesis results from understanding its modes of action and the effect of exposure routes. The National Research Council (NRC) of the National Academy of Sciences (NAS) is reviewing EPA's current human health risk estimates, the Taiwanese data (which were used to derive EPA's surface water criterion and Canada's drinking water standard), and the adequacy of the MCL and surface water quality criteria values. EPA had an expert panel review arsenic's mode of action for EPA's Integrated Risk Information System (IRIS). Stakeholders asked about EPA's DNA methylation research, the new cancer assessment guidelines, exposure from foods and beverages, available databases, and use of long-term research.
Regulatory Development and Public Participation. Several risk management components are considered when developing a drinking water regulation: treatment technologies; analytical; occurrence assessment; and cost/benefit assessments. In the 1996 amendments, Congress directed EPA to use the best available, peer-reviewed science for decision-making; study populations at greater risk; list treatment technologies for small systems; assess incremental costs and benefits; determine whether costs justify the benefits; and establish a national occurrence database by August 6, 1999. EPA must address a number of other statutes and executive orders when issuing a regulation.
EPA seeks to involve all interested parties at all appropriate stages in the development of arsenic regulations. Approaches include having EPA hold additional stakeholder meetings, schedule in-depth meetings, time arsenic meetings to coincide with other EPA or association meetings, utilize the OGWDW website, contribute to trade newsletters, and maintain mailing lists as methods for increasing communication before the comment period on the proposed rule. Consultations with the Science Advisory Board and National Drinking Water Advisory Council are open to the public. A stakeholder expressed interest in commenting on all supporting documents before the proposal is issued. He also suggested that EPA hold another stakeholders' meeting in early 1999 to present more details of MCL development.
Next Steps. The Office of Ground Water and Drinking Water web page lists announcements of future meetings and contains meeting summaries. Stakeholders are encouraged to contact EPA staff who made presentations. People who wish to get copies of EPA manuscripts accepted for publication should contact Irene Dooley, [firstname.lastname@example.org] who will pass the names and addresses on to EPA's ORD scientists.
Low-Dose Exposure To Arsenic Increases Risk For Skin Lesions
Skin cancer is the most common arsenic-related cancer. The most common route of human exposure to arsenic is through ingesting drinking water that is naturally enriched with arsenic. With an estimated 57 million people in Bangladesh having been exposed to high levels of arsenic from drinking water, UNICEF and the Bangladeshi government installed a large number of hand-pumped tube-wells to provide pathogen-free drinking water to the population.
Although local experts have frequently stated that the acceptable WHO level for arsenic in the drinking water at 50mg/Litre was too high, until now, estimates of the health effects associated with low-dose exposure to arsenic in drinking water was based on research from high-dose levels. In a study of more than 11,000 people in Bangladesh, research conducted by Columbia University's Mailman School of Public Health clearly provides evidence that a population exposed to well water with arsenic concentrations of as little as 50 ug/l is at risk for skin lesions. The report also concludes that older, male, and thinner participants were more likely to be affected by arsenic exposure.
The researchars indicate that a unique opportunity exists in Bangladesh to study chronic arsenic exposure measured at the individual level, because the majority of the population use a single well as their primary source of drinking water, while, for example, in the United States, people usually drink water from multiple sources. However, up until now even assessments at the individual level were extremely difficult because exposure measurements were from years past or the Bangladeshi population drank water from multiple sources. Another obvious difference between the rural population of Bangladesh and other studied populations is that this population consumes a large amount of water, as much as 2.5–3 litres per day on average vs. <1 litre in the United States. Moreover, almost 100 percent of the drinking water for this population come from one or two wells with relatively stable concentrations of arsenic.
The team of researchers noted that skin lesions were less of a factor in the study for females participating in the study. This they concluded, may be due to the tendency of women in rural Bangladesh tend to cover their bodies more extensively than men. Joseph Graziano, PhD, Mailman School associate dean for research, professor of Pharmacology & Public Health, and professor of Environmental Health Sciences observed that “it also is possible that hormonal and other biologic differences between men and women could be responsible for part of the gender differences in the skin lesion risks.” The study also found some evidence that participants with a higher body mass index were at lower risk of skin lesions than participants with a lower body mass index. “Lower body mass index reflects poorer nutritional status in rural Bangladesh, which could directly or indirectly influence the effect of arsenic. In particular, poor nutritional status may be associated with lower intake of the antioxidants, folates, and/or dietary proteins necessary for metabolism and detoxification of arsenic in the body, said Dr. Ahsan. The influence by gender, age, and body mass should be considered in future research and policy decisions.”
Because of the wide range of arsenic exposure in the study population and the relatively large sample size, the researchers were able to estimate and report dose-response relations even at the very low end of the arsenic exposure range. In particular, arsenic exposure seems to increase the risk of skin lesions at the low end of exposure in this population,” said Habibul Ahsan, MD, MMedSc, associate professor and director of the Centre for Genetics in Epidemiology in the Department of Epidemiology at the Mailman School of Public Health and principal investigator.
This study builds on some of the activities developed in coordination with the NIEHS-funded Superfund Basic Research Programme, led by Dr. Joseph Graziano, whose primary goal is to elucidate the health effects and geochemistry of arsenic. The work of the Superfund involves studies at four sites in the US, and also focuses on carcinogenic, reproductive, and childhood effects of arsenic exposure in drinking water in Bangladesh (Source: The Bangladesh Observer, June 21, 2006).
Last Modified: July 8, 2006