ArsenicWhat is arsenic?
 |
Inorganic – Varying amounts of this form can be found in water (ground and surface) and geologic materials (soils, rocks, aquifer materials)
Organic (arsenic compounds that contain carbon) – Varying amounts of this form are found in animals, plants and seafood.
Inorganic arsenic is of major concern in the desert Southwest due to its ubiquitous presence. Unlike most regions of the U.S., Arizona draws its drinking water from wells (not lakes and rivers). Digging the wells requires penetrating arsenic layers in the subsurface. Inorganic arsenic in the drinking water of millions of people has become a problem of global proportions.
 |
Why do we study arsenic?
It could be reasonably argued that arsenic is the most readily recognized poison to the lay population and the medical professional alike. At the same time, arsenic is one of the most ubiquitous and often identified toxins at sites of environmental contamination worldwide. There are few countries, either developed or underdeveloped, that do not have a documented arsenic contamination issue. Consequently, active arsenic research programs have existed in laboratories around the world for many decades. Environmental regulators have likewise considered arsenic exposure a target of concern and the allowable limits for arsenic exposure, particularly in water, have been steadily reduced in response to the growing body of evidence of deleterious health effects at ever lower doses. Considering this history, it is particularly curious that the human-induced environmental contamination incident impacting the greatest number of humans in the last century is the arsenic in drinking water pandemic now affecting tens of millions of people in the Asian subcontinent. Thousands of shallow tube wells were developed in South and East Asia in an effort to break the path of fecal pathogen exposure in populations that relied on contaminated surface water for drinking and sanitation. However, the wells too often accessed groundwater containing high arsenic concentrations (or, as was sometimes the case, induced release of arsenic into the groundwater). Consequently, an estimated 60 million people in the region are now at risk from high levels of naturally occurring arsenic. This human-induced mass poisoning is largely a result of doing seemingly good deeds without doing good homework. Considering this backdrop, it is even more curious that in the United States we have not chosen to take a precautionary path as we appropriately begin to remove arsenic from our drinking water supplies in unprecedented masses, but then dispose of the removed residues into conditions remarkably similar to those associated with the arsenic mobilization in Asia.*
The revised arsenic in drinking water maximum contaminant level that went into effect in January 2006 required several thousand drinking water utilities in the United States to lower the arsenic level in the water they distribute. This passage of a more stringent arsenic in drinking water standard set by the USEPA mandates the capping of wells or treatment (reducing the amount of the arsenic) from water before it can be used for consumption. Thus, our SBRP emphasizes studies to understand exposures to arsenic, processing of arsenic in the body, low-level toxic effects of arsenic, arsenic cycling in the environment, and remediation techniques to remove arsenic from water and to retain it in deposited residuals.
What types of Biomedical studies are being conducted by UA SBRP investigators?
The biomedical projects aim to:
 A close-up of the bladder showing the cell transformation after exposure to MMA (III) and As (III). |
- Clarify the toxic effects of low-level arsenic in a human bladder model and provide potential biomarkers for arsenic-induced bladder injury. Dr. A. Jay Gandolfi’s laboratory is the first to show that a metabolite of arsenate -monomethylarsonous acid (MMA (III)), transforms human bladder cells into tumor cells, possibly by oxidative stress mechanisms. For more information, please visit Project 1 or SBRP Research Brief 141.
- Understand the cardiovascular effects of arsenic toxicity. Currently, Dr. Richard Vaillancourt’s laboratory has shown that low concentrations of arsenite (inorganic) in drinking water is sufficient to induce hyperglycemia (diabetic state) in mice within 3 days of exposure. For more information, please visit Project 2.
- Evaluate the developmental effects of arsenic in the lung. Dr. Clark Lantz’slaboratory has demonstrated that in utero and early postnatal exposures cause alterations in pulmonary function that cannot be reversed simple by removing the arsenic. This data suggest that children exposed to arsenic during sensitive times would have an increased risk of developing lower respiratory infections. For more information, please visit Project 4.
- Fully characterize the genetic variability of all known genes involved in arsenic biotransformation in diverse populations. Dr. Walt Klimecki’s group has performed the most comprehensive genetic study of human arsenic metabolism to date, testing three genes with documented involvement in arsenic metabolism to determine whether person-to-person genetic variation associates with the way arsenic is metabolized in some people. For more information, please visit Project 5 or SBRP Research Brief 135.
USEPA 18-hour TCLP and California 48-hour WET leaching tests being performed in Dr. Ela's laboratory. For more information about the TCLP test, click on the image above. |
Currently, Dr. Wendell Ela (Project 8) is investigating arsenic treatment technologies, arsenic residuals assessment and arsenic residuals stabilization. The revised arsenic in drinking water maximum contaminant level that went into effect in January 2006 required several thousand drinking water utilities in the United States to lower the arsenic level in the water they distribute. Most of those implementing a removal technology have chosen some form of sorption by an iron-based media, so that the arsenic is transferred from an aqueous to a solid media. The options for disposal of the now arsenic-bearing solid residual (ABSR) are determined by whether it passes the Paint Filter Test, to assess if there is excess free water, and the Toxicity Characteristic Leaching Test (TCLP), to assess if there is excess arsenic leaching. Nearly all of the ABSR generated that are currently used or predicted to be used for arsenic removal from drinking water pass the TCLP and will be disposed of in Municipal Solid Waste (MSW) landfills. However, SBRP supported research has shown that the TCLP significantly under-predicts the release of arsenic from ABSR under MSW landfill conditions.* Thus to the degree possible, it is important to develop economically and technologically viable means to stabilize the current generation of ABSR, while concurrently developing new technologies with less environmentally problematic residuals. For example, Dr. Ela's laboratory has been working on a:
 The graph above shows the effectvieness of encapsulation with 3 different types of ABSR media. Unencapsulated ABSR leach above the TCLP limit. Traditional cement encapsulated ABSR leach arsenic at higher levels than the unencapsulated ABSR. Polymer encapsulation reduces leaching by a factor of 15 or more. Cement has a maximum waste loading of 18% while polymer loading is 60% or higher. |
Polymeric encapsulation technique that can stabilize the current generation of ABSR types. The encapsulation technique has beendeveloped through the proof of concept stage and has been shown to stabilize 60% by weight of most types of ABSR. Encapsulation reduces ABSR leaching by at least two orders of magnitude under both standard and landfill simulation leaching tests. Initial economic analyses suggest the technology is less expensive than the alternative of hazardous waste landfilling.*
 Ferrous arsenate, a stable, low solubility iron-arsenic mineral. This mineral holds promise as an environmentally benign means of sequestering the arsenic. |
Crystallization approach that shows promise as the final home for the arsenic removed from a regenerable media and brine treatment train. It is envisaged that future installations will use this type of process if more holistically benign residuals management is incorporated into the overall process design. The arsenic crystallization occurs at ambient temperature and pressure and decreases the arsenic waste volume to near the minimum theoretical limit. The products are stable minerals that occur naturally in the environment.*
What type of translational activities have occurred to communicate the upcoming challenges of ABSR management?
Dr. Ela describes proactive environmental engineering as an opportunity to “assess and, where appropriate, act ahead of the hazard actually affecting the public’s health”. By collaborating with the US-EPA, Agency for Toxic Substances and Disease Registry (ATSDR), NIEHS SBRP and academia, Dr. Ela was able to organize a series of workshops that provided an interactive public forum to disseminate, and discuss the most recent regulatory and scientific information regarding the assessment and disposal of ABSR. The three workshops organized with SBRP sponsorship on arsenic and landfills represent one useful tool for motivating and focusing the discussion and information transfer among a range of stakeholder groups. This is an important prerequisite to sound decision-making. Such workshops’ effectiveness is proportion to the degree they are able to promote, channel, and distill an open and multi-directional dialogue among all participants.*
Please click on the workshop title below to view a workshop report.
 |
Assessment and Disposal of Arsenic-bearing Solid Residuals
February 28 – March 1, 2005
Washington, DC
Disposal of Arsenic-Bearing Water Treatment Residuals: Assessing the Potential for Environmental Contamination
February 13-14, 2006
Rio Rico, Arizona
Arsenic and Landfills: Protecting Water Quality - white paper is currently under review.
October 3-4, 2006
Boston, Massachusetts
To view all workshop agendas and presentations, please visit the NIEHS webpage entitled: "Research Translation Core Network - Arsenic Connect the Dots".
For more general information about TCE, download the informational brochure entitled:
What is arsenic? or ¿Que es el Arsenico?
*Extracted from the white paper entitled: "ABSR: A Status Summary and Look Forward", written by Wendell P. Ela, 2007.
