Spring 2007

UW Water Resources Research

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Researchers Examine Drinking Water for Signs of Endocrine Disruptors

By Brian Sweeney

The female sex hormone estrogen is found naturally in humans and animals, but it and other estrogenic endocrine disruptors (EEDs) are showing up all over the environment due to drugs like birth control pills and industrial products like plasticizers and surfactants. Funded by the UW Water Resources Institute, a group of researchers from the Wisconsin State Laboratory of Hygiene examined whether EEDs are entering the state’s groundwater, the source of drinking water for seventy percent of the population.

Estrogen and other EEDs have been linked to endocrine disruption in fish like smallmouth bass and carp, both in the U.S. and abroad, causing the production of female proteins and even eggs in males. While environmental EEDs have not been linked to effects in adult humans, they could pose a threat to reproduction and development, said Jocelyn Hemming, an environmental toxicologist who worked on the study.

“The concern is that estrogens do have strong effects on growth, reproduction and development, and so additional sources of estrogens have the potential to cause adverse effects,” she said.

Many researchers believe that EEDs are linked to decreased sperm count, breast cancer, and certain birth defects.

Hemming and her colleague Miel Barman worked with the Department of Natural Resources to identify areas in Wisconsin at high risk for EED contamination. Those areas include communities using high-capacity municipal wells where nearby surface waters contain EEDs.

When high-capacity wells rapidly deplete groundwater aquifers, surface water can leak into aquifers faster and in greater volume, possibly carrying contaminants with it. In cooperation with local hydrologists, the researchers gathered samples from highcapacity municipal water supply wells and nearby surface waters. They used a highly sensitive bioassay called E-screen to measure EED levels in the samples.

The study found that all of the surface waters tested, with one exception, had some level of EED activity, but those levels were very low. Levels in the groundwater drawn from highcap wells were even lower, with most below the level of detection for the assay.

The researchers also looked at another situation in which groundwater might be susceptible to EED contamination, this time in rural areas where municipal wells and sewers aren’t available. One-third of Wisconsin households use private onsite wastewater treatment systems, commonly known as septic systems.

These systems collect waste in a holding tank, where solids settle out from liquid effluent. While bacteria break down the solids, the effluent flows or is pumped into a leaching field where it gradually soaks into the soil. The researchers examined whether effluent from these systems is contributing to EEDs in the groundwater.

Some newer types of septic systems pretreat the effluent before releasing it into the leach field, most often with sand filtration or aerobic treatments. The study found that the mean EED level of non-treated waste from traditional septic systems was about 23 times that of pretreated septic effluent in the newer types of systems. Both sand filtration and aerobic pretreatments removed about 98 percent of estrogen, which is comparable to what municipal treatment systems remove.

Despite the higher EED levels found in septic systems not using a pretreatment method, no EEDs were detected in the groundwater beneath these systems. That’s good news for many Wisconsin homeowners. However, the researchers stressed that all of their samples were collected from new housing developments, and regular monitoring is needed to ensure that EEDs do not eventually make their way into the groundwater.

While EEDs do not appear to pose an immediate threat to people in Wisconsin, Hemming says other states might be well advised to test their groundwater for EEDs.

“In the locations we tested, I would say we are safe at this time, but other locations with higher population densities and a more arid climate — for example, some places in the western U.S. — will need to conduct similar studies to evaluate their drinking water sources,” Hemming said. “I don’t think we know enough yet about other sources, livestock waste, for example, and that is what we should be focusing on next.”

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