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November / December 2002 Cover


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Arsenic has an Accomplice?

Photo Illustration by Toby Hollis


Arsenic has an Accomplice?
Research reveals the toxin that contaminates wells may get assistance from a newly discovered microbe

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They live a dark, unassuming existence, going about their quiet, microscopic lives in underground waterways. But now University of Maine researchers are questioning whether the lifestyle of these microbes is inadvertently poisoning our groundwater, contaminating it with elevated amounts of arsenic.

In the laboratory, UMaine environmental engineer Jean MacRae and a team of researchers have isolated a previously unknown species of bacteria. Given the right conditions, the microbes can speed up the normally slow chemical processes that release arsenic from bedrock into groundwater.

If confirmed through additional research in the field, MacRae's findings could contribute to our knowledge about how arsenic gets into Maine's groundwater.

The possible breakthrough comes none too soon. Arsenic is a naturally occurring chemical element in rock and soil the 20th most common in the Earth's crust. Bedrock is one of the most significant sources of arsenic in water, as demonstrated in research by UMaine scientist Andrew Reeve and other geologists. In addition, arsenic contamination can come from manufactured products such as treated wood and pesticides.

Knowing how arsenic seeps out of Maine's bedrock and into wells could help landowners keep it out of the water, MacRae says, and could aid in reducing a long-term health threat.

At high levels in drinking water, arsenic can kill quickly; at lower levels, it can cause cancer of the skin, bladder, kidney, lung and liver, and it can affect blood circulation. Even at very low levels, new evidence suggests that arsenic can affect reproduction and contribute to diabetes.

MacRae's interest in the toxin stems from her awareness of just how severe the problem can be. In Bangladesh, millions of people suffer from health problems caused by drinking arsenic-laced water. According to the World Health Organization, more than 200,000 people could die of arsenic-related cancers in Bangladesh.

In Maine, arsenic levels in some wells are similar to those found in South Asia, but the problem is far less widespread. Nevertheless, the State Drinking Water Program estimates that 10 percent of homes with private wells have unsafe levels of arsenic in their water. Instead of being evenly spread out across Maine, these homes tend to occur in clusters, such as the Bayside community in Northport, and along Green and Branch lakes near Ellsworth.

"Arsenic levels are high in parts of Maine, and they are hard to explain in terms of the geology," says MacRae, who this year was awarded a National Science Foundation Career Award in support of her research. "One home may have a high level, while a neighboring home is low. That made me think that we have either a patchy situation where the geology is affecting (the levels), or we've got different cultural practices and land uses that make it a problem in one area and not in another."

While the bulk of arsenic research has focused on geology, the role of bacteria has remained largely unexplored. "Everywhere we look there's an important role for microorganisms in cycling (elements) in the environment. I think the likelihood of microbial involvement in cycling (arsenic) in the subsurface is great. Chemical reactions in the environment happen slowly, but you can get things to speed up if you add some microbial action," says MacRae, who combines her engineering expertise with a master's degree in microbiology.

With a grant from the U.S. Geological Survey through UMaine's Senator George J. Mitchell Center for Watershed and Environmental Research, MacRae and Kevin McCaffery, a master's student, collected water samples in 2001 from two wells with high arsenic levels, one in Bayside and the other near Ellsworth.

In the lab, they isolated some bacteria that could have an effect on arsenic compounds in the water, transforming a less toxic form into a more toxic, mobile form. The next step is to prove bacteria are making this transformation in the environment.

This year, MacRae received a $375,000 five-year grant from the National Science Foundation to continue her research on bacteria and arsenic. Working with her will be engineering graduate students Ingrid Lavine and Erin McCormick. They will work respectively on refining techniques to identify the presence of arsenic-transforming bacteria and to determine what factors affect the rate of leaching. MacRae also is planning to involve public school students and teachers in using the subject for meeting Maine's Learning Results goals in the classroom.

In addition to contributing knowledge about how arsenic gets into groundwater, MacRae may be breaking new ground in microbiology. When she and McCaffery took a closer look at the identity of the Northport bacteria species, they found that it was not described in the scientific literature. The species they found is new to science.

Geochemists and microbiologists are increasingly teaming up to consider the role that microbes play in the environment. For MacRae, such collaborations offer the potential for solutions to environmental problems. "I got interested in environmental engineering because it was closer to finding a solution that would happen in my lifetime," she says.

"Once you get a sense of how things are actually working in the environment, then you have more angles on how to fix a problem. If we find that these organisms are responsible for speeding up the release of arsenic from bedrock or from the groundwater environment, then we can start looking at land-use factors, such as septic field maintenance or the addition of manure to fields," she adds. Under some circumstances, such activities could promote the growth of bacteria underground and make a small arsenic problem worse.

by Nick Houtman
November-December, 2002

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