From: Emily Sohn, Discovery News
Published May 22, 2009 09:51 AM

Sweeteners Linger in Groundwater

After tickling the tongue, artificial sweeteners pass through our bodies and end up in wastewater virtually unchanged. Some sweeteners are particularly widespread in the environment, according to a new study, making them ideal markers for following pollution from treatment plants and other sources into the environment.

"Groundwater can be polluted by several sources, and it's sometimes not clear where that pollution comes from," said Ignaz Buerge, an environmental chemist at the Swiss Federal Research Station in Schloss. "We now have a marker of domestic wastewater which can be used in tracing pollution."

Contaminated groundwater is both an environmental and public health issue. Once run-off gets into the environment, though, it can be hard to know whether it came from industry, agricultural fields, traffic, homes or other sources. Scientists have been looking for marker molecules that might help them track down and possibly reduce some of these inputs.

Previous candidates for markers have included caffeine, pharmaceuticals and components of personal care products. Most of these chemicals, however, either break down quickly, appear in quantities too small to easily detect, or seep out of the water and into the soil.

Buerge and colleagues wondered if artificial sweeteners might work. People consume large quantities of them, for one thing. And previous work suggested that the chemicals pass through the human body unchanged and end up in untreated wastewater.

The scientists collected both treated and untreated samples from 10 wastewater treatment plants. They also collected urban groundwater, tap water, and water from four rivers and eight lakes near Zurich and from a remote alpine lake.

In each sample, the researchers looked for evidence of four sweeteners: Acesulfame K, saccharin, sucralose, and cyclamate. All four are commonly used in the United States except cyclamate, which is banned.

Results, published in Environmental Science & Technology, found evidence of all four sweeteners in untreated wastewater. In treated water, 90 percent of saccharine and 99 percent of cyclamate were eliminated. Sucralose endured, but concentrations were small.

When it came to acesulfame, a significant amount survived the treatment process unharmed. The scientists measured the equivalent of 10 milligrams per person per day of the sweetener in untreated waters, Buerge said, and the same concentrations in treated waters, which often ended up in lakes and rivers.

"These concentrations are astronomically high," said Bruce Brownawell, an environmental chemist at Stony Brook University in New York. "If I had to guess, this is the highest concentration of a compound that goes through sewage treatment plants without being degraded."

While the team found no sweeteners in the remote alpine lake, levels of acesulfame increased proportionately in bodies of water as nearby human population sizes went up. The sweetener also showed up in 65 out of 100 groundwater samples and even made its way in small amounts into tap water, suggesting that acesulfame remains stable as it moves with wastewater.

Levels were too low to be of concern to human health and far too low to make the affected water taste sweet. But the fact that acesulfame is easily detected in groundwater makes it a promising tool for determining whether contamination comes from domestic sources, Buerge said.

"We basically proved," he said, "that these sweeteners can be used quantitatively as a marker."

One thing that scientists still don't know is whether acesulfame has any impact on fish or the environment. Those tests haven't yet been done.