Arsenic, even for a poison, is one nasty brew. Long-term ingestion of the metallic substance can result in thickening and discoloration of the skin, stomach pain, nausea, vomiting, diarrhea, numbness in hands and feet, partial paralysis and blindness. The U.S. Environmental Protection Agency (EPA) classifies inorganic arsenic as a Group A agent, a human carcinogen and, since the 1990s, exposure to it has been linked to an increased risk of diabetes mellitus.
New findings by a group of scientists add support for the theory that there is a link between arsenic and diabetes. Two coauthors of those studies are on an expert panel of the U.S. Department of Health and Human Services National Toxicology Program investigating the link between environmental chemicals and diabetes and obesity. “Our panel of experts, who met last January, concluded there is sufficient evidence to link high arsenic exposure in drinking water to diabetes,” says the study’s principal investigator, Miroslav Stýblo, a biochemist and an associate professor in the department of nutrition, University of North Carolina at Chapel Hill. “With low levels, there is significant uncertainty. Our data also suggests that if you have a certain genetic makeup you are at higher risk.” Stýblo says typical exposure rates in the U.S. are lower than those in most studies that found an association with diabetes.
Arsenic occurs naturally in bedrock and soil, and is released through natural activities like volcanic action. Ninety percent of industrial arsenic in the U.S. is used as a wood preservative. Mining, smelting and agriculture also contribute to arsenic releases. To protect consumers of public water systems from the effects of long-term, chronic exposure to arsenic the EPA lowered the arsenic standard for drinking water from 50 parts per billion to 10 ppb in 2001.
Stýblo and eight other scientists studied populations in the Zimapán and Lagunera regions in Mexico to determine whether exposure to arsenic in drinking water is correlated with an increased prevalence of diabetes. Their research was published in the August issue of the journal Environmental Health, and is “very relevant” for the Native American population, says study coauthor Dana Loomis, Associate Director, Cancer Prevention & Control at the Eppley Cancer Institute, University of Nebraska Medical Center, in Omaha. “Most American Indians are living in the western U.S. It’s in that part of the country that elevated areas of arsenic exposures are found. It’s incorporated into the bedrock geology. Because of the way desert water systems work, the concentrations can be enhanced, especially in arid parts of the West.”
Arizona, Utah, Nevada and California in particular are worrisome areas for arsenic contamination. Another report adds Washington and Alaska to the list.
The Navajo Nation has more than 250,000 federally recognized members living on its sprawling 27,000-square-mile reservation on parts of northeastern Arizona, southeastern Utah and northwestern New Mexico. Water supplies that do not meet U.S. Safe Drinking Water Act standards, particularly in the rural and remote areas of the reservation are of heightened concern. “There are some high contents of arsenic known on the Navajo Nation,” says George Breit, a geologist with the U.S. Geological Survey in Denver, and one of the world’s leading experts on arsenic contamination in groundwater. He cites a study of the area of Hopi Buttes (Tsezhin Bii) that reported several rock samples with more than 100 parts per million.
Breit says all earth materials contain some arsenic; whether it can be transferred to water depends on the reactivity of its binding phase when placed in a different environment. “There are four general environments in which arsenic is present in sufficient concentrations in groundwater to be of concern,” he says. “The Navajo Nation has environments in which all four of these mechanisms may exist.”
The Navajo Tribal Utility Authority (NTUA) is the only provider of drinking water for the reservation that meets the requirements of the Safe Drinking Water Act. Although the utility is extending its system, unregulated water is still the only water source for one quarter of the homes on the reservation. When the Diné Environmental Institute of the Diné College and the University of Nevada, Reno tested unregulated water supplies in 2008, they found that levels of arsenic and other contaminants including uranium exceeded the EPA Maximum Contaminant Levels. For the past four summers the Diné Environmental Institute has tested water supplies in the eastern region of the Navajo Nation. “We typically test water in the livestock wells because a lot of people are still not hooked up to water supplies,” says Diné College science department faculty chair Barbara Klein. “Even though the wells might not be potable, [people] end up drinking from [them].”
The teachers and students choose an area and test livestock wells, artesian wells and springs. “We typically test for bacteria,” Klein says. “Samples are sent for testing for heavy metals. We pay most attention to arsenic and uranium.” She says they’ve found dangerously high levels of uranium in areas where there are a lot of reclaimed and unreclaimed uranium mines.
When the EPA, Indian Health Service, U.S. Department of Health and Human Services, Centers for Disease Control and Prevention (CDC), NTUA and Navajo representatives formed the Navajo Access Workgroup to undertake a 2010 project to map the water infrastructure, their results indicated a funding need for a “Shiprock to Sweetwater” project that would address the problem of high arsenic levels in the source water of 1,001 homes.
Water safety is the focus of Forgotten People, a community development corporation on the Navajo Nation. Program director Marsha Monestersky says their advocacy resulted in the Navajo Nation issuing a Declaration of Public Health State of Emergency in the Black Falls/Box Springs (Arizona) region in the southern portion of the western agency of the Navajo Nation in January of 2010. “We have the EPA test results and the data that show all the water sources in [that region] exceed EPA standards for arsenic and uranium,” she says. Their organization received an Environmental Excellence award from the Navajo Nation EPA in 2009, and a $20,000 environmental justice grant from the U.S. EPA that same year. “Our job is really hard because a lot of people we’re working with have cancer, and there’s a lot of diabetes,” Monestersky says. “Every time they build a dialysis center it can’t accommodate all the patients [because] the need is so great.”
Arsenic is a concern elsewhere. The Fort McDowell Yavapai Nation in Arizona objected to the Southeast Arizona Land Exchange and Conservation Program two years ago in part because the subsequent new mining would expose the tribal community to “abundant deposits of…poisonous arsenic.”
Arsenic got top billing on the Tohono O’odham Nation’s (TON) list of environmental health threats in their Comprehensive Cancer Prevention and Control Plan: 2010-2015 sponsored by the CDC. “All Americans,” said TON’s Environment and Cancer Committee in the report, “including the O’odham are entitled to clean water under the Safe Drinking Water Act. Whether arsenic is linked to illness or cancer is not as critical as the fact that low-level chronic exposure to the human body is not a healthy thing.”
At the time of the report arsenic concentrations in their water ranged from trace amounts to 1,000 ppb. At least 23 of their communities have water with elevated levels of arsenic, and 17 of their 35 public water systems have arsenic levels from 10 ppb up to 32 ppb, above the EPA standard for arsenic but considered low compared to other areas in Arizona. Their report also cites an earlier study linking arsenic exposure through drinking water with a higher prevalence of type 2 diabetes.
TON’s pilot arsenic treatment using iron-oxide adsorption reduced arsenic at a public water system from 33 ppb to less than 1 ppb. TON’s report recommends the Agency for Toxic Substances and Disease Registry and the CDC use their public health authority to ensure funding. They claim that since their report was issued they’ve resolved much of the problem.
In Alaska, some of their high arsenic levels occur naturally, and some are produced by military and mining operations, says Pamela Miller, executive director for the Alaska Community Action on Toxics. “At Kivalina’s Red Dog Mine, there is concern that emissions from the mining operations are transmitted atmospherically,” Miller says. “Fish have elevated levels of arsenic in their muscle and liver. A study found that levels found in fish were higher in Alaska than in California. We’re concerned about the levels of arsenic in groundwater, but we also recognize arsenic can be transported in the air, and deposited in waters and taken in by sea creatures important to tribal subsistence.”
Regardless of the arsenic link to diabetes, Stýblo says that the number-one reason for the diabetes epidemic is U.S. is obesity. “I think it’s fair to say exposures in the U.S. are lower than most studies found to be associated with diabetes. If arsenic contributes, it’s relatively minor. It is possible that arsenic may work with obesogens, but obesity remains the number-one explanation.” Obesogens are environmental contaminants that promote obesity. Diabetogens promote diabetes. Arsenic does not seem to promote obesity, but acts as a direct diabetogen, Stýblo says. Other organic and inorganic compounds are also thought to cause diabetes. “Most of them seem to promote obesity first; diabetes is a secondary effect, i.e. resulting from obesity.”
Although the arsenic levels are low for many people in the U.S., Stýblo says it is still a significant issue, “because we have tens of millions people worldwide who are exposed to high arsenic levels, so it’s still affecting a very large number of people. Arsenic is known as a carcinogen; it’s only recently that people like us became interested in its toxicology.”
Loomis agrees, “Even a minor cause is important when large numbers of people are exposed to it.”