EVISA Print | Glossary on | Contact EVISA | Sitemap | Home   
 Advanced search
The establishment of EVISA is funded by the EU through the Fifth Framework Programme (G7RT- CT- 2002- 05112).

Supporters of EVISA includes:

Gut bacteria transform inorganic arsenate leading to more toxic arsenic species


Arsenic pollution is a serious global health problem. It is driven by exposure to naturally-occurring sources – especially groundwater and food – and human activities associated with smelting and mining that create dust or liberate the metal from the soil.

High levels of arsenic occur naturally in India, Pakistan, parts of the United States and other hot spots around the world. Exposure to excess arsenic can lead to cancers of the lung, liver, bladder and kidney.

The toxicity of arsenic compounds differ by orders of magnitude depending on the oxidation state of arsenic and the grade of methylation with methylated trivalent species—monomethylarsonous acid (MMAIII), dimethylarsinous acid (DMAIII), and arsenous acid (iAsIII)—being two orders of magnitude more cytotoxic than As acid (iAsV).

The new study:
Fig.1: Human gastrointestinal tract
An international research group now found that bacteria living in human intestines can change arsenic's chemistry, in some cases producing a more toxic form that is linked to cancer. While similar results have been found already in animal studies, this is the first report of arsenic becoming more harmful as it passes through the human digestive tract.

In this study, bacteria from a human intestine were cultured in a specialized system that simulates the digestive system, including the stomach, small intestine and colon. Researchers added either inorganic arsenic or four types of soils with arsenic naturally present. After incubation, the resulting mixtures were analyzed by arsenic speciation analysis using by LC-ICP-MS to determine the arsenic species being present.

They found that the bacteria altered a significant portion of the initial inorganic arsenic through methylation. In addition to the formation of monomethylarsonic acid, they detected the highly toxic monomethylarsonous acid. In this way, the microbes changed the arsenic from a less toxic form to a more toxic variety. The toxic varieties were formed from both pure inorganic arsenic and from inorganic arsenic present in soils, suggesting that this process occurs even with arsenic that adheres to soil particles.

These unexpected results highlight concern about increasing arsenic's toxicity when it is transformed in the gut and suggest that regulators may need to take into account the way exposures occur when determining the health risks associated with arsenic.

The new study

Tom Van de Wiele, Christina M. Gallawa, Kevin M. Kubachka, John T. Creed, Nicholas Basta, Elizabeth A. Dayton, Shane Whitacre, Gijs Du Laing, Karen Bradham, Arsenic Metabolism by Human Gut Microbiota upon in Vitro Digestion of Contaminated Soils, Environ. Health Perspect., 118/7 (2010) 1004-1009. DOI: 10.1289/ehp.0901794

Related studies

K.M. Kubachka, M.C. Kohan, S.D. Conklin, K. Herbin-Davis, J.T. Creed, D.J. Thomas, In vitro biotransformation of dimethylarsinic acid and trimethylarsine oxide by anaerobic microflora of mouse cecum analyzed by HPLC-ICP-MS and HPLC-ESI-MS, J. Anal. At. Spectrom., 24 (2009) 1062–1068. DOI: 10.1039/b817820h

K.M. Kubachka, M.C. Kohan, K. Herbin-Davis, J.T. Creed, D.J. Thomas, Exploring the in vitro formation of trimethylarsine sulfide from dimethylthioarsinic acid in anaerobic microflora of mouse cecum using HPLC–ICP-MS and HPLC–ESI-MS, Toxicol. Appl. Pharmacol., 239/2 (2009) 137–143. DOI: 10.1016/j.taap.2008.12.008

J. Meyer, K. Michalke, T. Kouril, R. Hensel, Volatilisation of metals and metalloids: an inherent feature of methanoarchaea?, Syst. Appl. Microbiol., 31 (2008) 81–87. DOI: 10.1128/AEM.02933-07

M.J. Herbel, J.S. Blum, S.E. Hoeft, S.M. Cohen, L.L. Arnold, J. Lisak, et al., Dissimilatory arsenate reductase activity and arsenate-respiring bacteria in bovine rumen fluid, hamster feces, and the termite hindgut, FEMS Microbiol. Ecol., 41 (2002) 59–67. DOI: 10.1111/j.1574-6941.2002.tb00966.x

L.L. Hall, S.E. George, M.J. Kohan, M. Styblo, D.J. Thomas, In vitro methylation of inorganic arsenic in mouse intestinal cecum, Toxicol. Appl. Pharmacol.,  147 (1997) 101–109. DOI: 10.1016/taap.1997.8269

Related EVISA Resources

Brief summary: ICP-MS: A versatile detection system for speciation analysis

Brief summary: LC-ICP-MS: The most often used hyphenated system for speciation analysis
Link database: Toxicity of arsenic species
Brief summary: Speciation and Toxicity

Related EVISA News (newest first)

May 19, 2010: China: Inorganic Arsenic in Rice - An Underestimated Health Threat ?
May 17, 2010: Uptake of arsenic through human skin depends strongly on its speciation
February 23, 2010: Accumulation or production of arsenobetaine in humans?
February 23, 2010: US EPA opens inorganic arsenic cancer assessment for public review
December 4, 2009: EFSA: Scientific Opinion on Arsenic in Food
May 26, 2009: UK Food Standards Agency releases research on arsenic in rice milk
February 23, 2009: Toenail clippings reveal arsenic exposure
January 31, 2009: Using the right recipe for cooking rice reduces toxic inorganic arsenic content
December 4, 2008: High level of inorganic arsenic in blue mussels from Norwegian Fjords
November 11, 2008: EFSA calls for data on arsenic levels in food and water
September 5, 2008: Exposure to inorganic arsenic may increase diabetes risk
August 8, 2008: Arsenolipids in Fish Oil
July 18, 2008: Experts detail how rice absorbs arsenic from the soil
March 15, 2008: Arsenic in rice milk exceeds EU and US drinking water standards
February 15, 2008: Arsenic speciation in rice: a question of the rice plant species
December 26, 2007: The effect of thermal treatment on the arsenic speciation in food
March 7, 2007: Elevated Arsenic Levels Found In Rice Grown In South Central States of the USA
January 17, 2007: Human metabolism of arsenic is altered by fasting
January 11, 2007: More evidence linking chicken litter and toxic arsenic
June 18, 2008: Bacteria supposed to remove poisonous arsenic from drinking water
January 18, 2006: Hungarians exposed to high arsenic levels in drinking water
December 17, 2005: Seasonal supply of arsenic to Bangladeshi groundwater
October 6, 2005: Two new Thio-Arsenosugars found in Scallops
August 3, 2005: Surprisingly high concentrations of toxic arsenic species found in U.S. rice
July 29, 2005: Arsenic-free water still a pipedream
June 27, 2005: Susceptibility to arsenic toxicity influenced by genes

last time modified: May 20, 2024


Imprint     Disclaimer

© 2003 - 2024 by European Virtual Institute for Speciation Analysis ( EVISA )