Something in the Water - Part I
- By Jim DiPeso
- Jun 01, 2001
This is the first of two articles addressing arsenic in drinking water. Part I concentrates on the scientific history and research. Part II will peer at the present and future debates concerning the regulations and politics related to this contaminant.
The concern about arsenic in drinking water has made waves across the world -- from Taiwan to the United States to Bangladesh. In 1966, skin cancers were found in Taiwan among people who drank from arsenic contaminated wells. In the 1980s, scientists began finding evidence of arsenic contamination in Bangladesh. There, large amounts of arsenic are in the groundwater- the primary source of drinking water -- under naturally occurring aquifer conditions.
According to a study published by the World Health Organization (WHO) in 2000, Bangladesh is facing the "largest mass poisoning of a population in history." A 2001 report from the U.K. Water Aid Bangladesh concluded more than 25 million people are exposed to arsenic in levels far above 10 parts per billion (micrograms/liter (ppb)) in Bangladesh and close to 10,000 patients with physical effects have been identified.
The poisoning in Bangladesh flows from the creation of millions of wells during the last 20 years inserted in the ground at depths of less than 200 meters. Ironically, many of these wells were constructed as part of a program to provide safe drinking water. At that time, arsenic was not recognized as a problem in water supplies. The alarm was first raised when doctors saw cases of arsenic-induced skin lesions in West Bengal, India in 1983.
A 2001 report from the U.K. Water Aid Bangladesh concluded more than 25 million people are exposed to arsenic in levels far above 10 ppb in Bangladesh.
In the United States, with the Safe Drinking Water Act (SDWA) in place and the maximum contaminant level (MCL) of arsenic at 50 ppb, U.S. Environmental Protection Agency (EPA) considers the American tap water supply one of the safest in the world, while the National Research Council of the National Academy of Sciences (NRC/NAS) estimates one out of 100 people ingesting water containing 50 ppb of arsenic will get cancer.
After decades of regulatory development, public comment, debate, millions of dollars in EPA research and several missed statutory deadlines (in the 1974, 1986 and 1996 SDWAs), EPA issued a lower arsenic standard of 10 ppb in January 2001. This matched the standard held by Japan, the European Union and WHO. More than two months after this final rule was issued, the Bush Administration rescinded the decision. EPA withdrew the standard, stating it needed additional time to seek independent reviews of the science behind the standard and the estimates of costs to communities implementing the rule. They now have until February 22, 2002 to publish a final rule. EPA is challenged "to develop a drinking water standard for arsenic that protects public health in the face of time constraints, scientific uncertainty and incomplete information," (Congressional Research Service Report, Sept. 2000).
Meanwhile, according to the 2001 National Water Quality Consumer Survey (a biennial report sponsored by the Water Quality Association), 49 percent of Americans believe federal drinking water laws are not strict enough and 62 percent of adults interviewed would pay more on their utility bills or on home water treatment to reduce arsenic if it was found to contaminate their water. (This survey was conducted in February 2001.)
As, a Semi-Metal
Arsenic is the 20th most abundant element naturally occurring in the earth's crust and the 12th most common element in the human body. It can combine with other elements to form inorganic and organic arsenicals. While some foods such as fish contain both inorganic and organic arsenicals, primarily inorganic forms are present in water and are of most concern. In the Earth's crust, arsenic is mostly in compounds with oxygen, chlorine and sulfur -- forming inorganic compounds. The U.S. Food and Drug Administration (FDA) estimates, on average, an adult ingests about .053 ppb a day of organic arsenic from dietary sources and NRC estimates that arsenic intake from food is comparable to drinking water containing 5 ppb.
Long-term exposure to low concentrations of arsenic can lead to skin, bladder, lung and prostate cancer and might lead to kidney and liver cancer.
Until the 1940s, inorganic arsenic solutions were widely used for medicinal purposes to assist in curing syphilis and leukemias. Commercially, arsenic has been used in the manufacture of glass and military poison gases, for the hardening of lead and as an insecticide. As a compound with other elements, it is useful as a semiconductor, laser material and a pigment in the manufacture of paints and fireworks.
The most common compound, chromated copper arsenate (CCA), makes up 90 percent of the industrial arsenic in the United States and is used to pressure treat wood for preservation and to prevent termite damage. A recent study by the University of Miami and the University of Florida found an average of 28 parts per million of arsenic in soil sampled from sites across the state of Florida where CCA wood was used for playground equipment. EPA banned most arsenic pesticides years ago but made an exception for pressure-treated wood, concluding that the benefits far outweighed any risks. The wood industry says its studies show the wood is safe.
Drip, Drip, Drip
Most arsenic enters water supplies from erosion of natural deposits in the Earth's crust or from industrial and agricultural pollution. Flood runoff or leaching (removal by a percolating liquid) of old arsenic-containing pesticides from sites where they were heavily used can lead to contamination of groundwater, and the weathering of rocks, burning of fossil fuels, volcanic activity, forest fires, mining and smelting of ores contribute to arsenic in the environment.
In wells, heavy pumping of groundwater has increased arsenic levels, and sometimes heavy groundwater pumping appears to have pulled water out of heavily contaminated layers of rock that were not the primary aquifer being tapped but had not been sealed off from the well. In other cases, possibly because over-pumping appears to have caused groundwater levels to drop, arsenic-bearing rock contact with air increased and thereby increased arsenic leaching. The theory is that the oxidation and subsequent arsenic release from aquifer rock, gravel and finer particle fractions is accelerated when wells are pumped intensively, causing a drawn-down zone around the well where air can periodically and frequently reach previously saturated subsurface rock.
There are contradictory findings surrounding the health effects of arsenic in humans. The International Agency for Research (IARC) has classified arsenic of questionable carcinogenicity in animals, and claims to have sufficient evidence that inorganic arsenic compounds are skin and lung carcinogens in humans. According to a 1999 study in Utah by Lewis et al., a study group drinking water with arsenic concentrations ranging from four to 620 ppb had less risk of bladder, digestive system and lung cancer mortality than the general Utah population. The 1999 study by NRC/NAS claims chronic, long-term exposure to low concentrations of arsenic can lead to skin, bladder, lung and prostate cancer and might lead to kidney and liver cancer. Other studies have found non-cancerous effects of ingesting arsenic acutely, at low levels, to be cardiovascular disease, diabetes and anemia, as well as reproductive and developmental, immunological and neurological effects. It also can cause serious skin problems, harm to th
e central and peripheral nervous systems, heart and blood vessels.
Some experimental animal studies of arsenic's biological activity suggest a potential role for the element as a nutrient in the animals tested. Nutrient roles at very low intakes and toxic effects at higher intakes are not uncommon with environmental elements, but do not ease the need for control of excessive exposures. NAS's report notes that "studies to date do not provide evidence that arsenic is an essential element in humans or that it is required for any essential biochemical process." Any nutrient role would have to be at very low levels. The report maintains that it is highly unlikely that arsenic could ever be regulated to levels so low that any human deficiency for the element would occur.
The latest edition of the WHO Guidelines for Drinking Water Quality (1993) stated the guideline for arsenic of 10 ppb was provisional because of the lack of suitable testing methods.
WHO claims that the dose-response and dose-effect relationships of arsenic in drinking water need to be further explored because knowledge about the health effects of arsenic is incomplete and the situation is complicated by factors such as nutrition and disease.
The 1999 NAC/NAS report assumed that there is a direct, linear relationship between cancer risk and arsenic exposure. The academy noted that arsenic at extremely low doses may, or may not, cause relatively less cancer risk per microgram than it does at high doses. However, the conservative, linear approach used by NAC/NAS follows that if the logic used and assumptions made err, they do so in favor of health protection.
The latest edition of the WHO Guidelines for Drinking Water Quality (1993) stated the guideline for arsenic of 10 ppb was provisional because of the lack of suitable testing methods. It is difficult for testing labs to reliably measure amounts of arsenic below three ppb.
An update of WHO's monograph on arsenic addressing all aspects of risks to human health and the environment is under preparation. Also, a U.N. Synthesis Report on Arsenic in Drinking Water is being prepared which will be a synthesis of the state-of-the-art arsenic knowledge. At the same time, the report will identify current knowledge gaps and research needs. The draft will be made available for public review and comment, and publication of the report is expected mid to late 2001.
NRC/NAS identified several areas for further research including: more epidemiological evaluations to gain a better understanding of how arsenic exposure triggers cancer and other disorders, especially at very low levels; how metabolism, genetic and dietary factors interact with arsenic and affect susceptibility to cancer; and data on how the amount of arsenic to which people are exposed relates to the concentration of arsenic retained in the body. In April 2001, EPA asked the NRC/NAS to perform a specific review of a range of three to 20 ppb in drinking water.
EPA is using its discretionary authority under the 1996 amendments to the SDWA to set the standard at a level that "maximizes health risk reduction benefits at a cost that is justified by the benefits." The potential for significant economic cost and significant uncertainties in the health science surrounding low-level exposure to arsenic make the issue a watery one. After all, according to WHO, "There is no consensus on the definition of arsenic poisoning."
Arsenic Crisis News -- bicn.com/acic
Arsenic - The EQI National Well Water Study -- www.main.nc.us/cleanwaterfundnc/cwlti.htm
Congressional Research Service Report for Congress RS20672: Arsenic in Drinking Water: Recent Regulatory Developments and Issues - www.cnie.org/nle/h2o-40.html
National Research Council's 1999 Report "Arsenic in Drinking Water" - www.nap.edu/catalog/6444.html
American Council on Science and Health, "What's the Story?- Pressure-Treated Wood" -- www.acsh.org/publications/story/wood/index.html
World Health Organization - www.who.int/water_sanitation_health/Arsenic/arsenic.htm
Natural Resources Defense Council's February 2000 Report Arsenic and Old Laws - www.nrdc.org/water/drinking/arsenic/aolinx.asp
NRC/NAS Report on Arsenic in Drinking Water -- books.nap.edu/books/0309063337/html/R1.html
This article originally appeared in the June 2001 issue of Environmental Protection, Vol. 12, No. 6, p. 29.
This article originally appeared in the 06/01/2001 issue of Environmental Protection.
Jim DiPeso is communications director at the Pacific Northwest Pollution Prevention Resource Center, Seattle.