COLUMBIA, Mo. - A recent Associated Press report revealing the presence of drugs in many municipal water supplies has raised questions about the risks to humans of long-term exposure to small amounts of pharmaceutical compounds. While it is believed that most of the drugs originate from human medications, University of Missouri researchers are investigating the impact of livestock pharmaceuticals and developing best practices to protect the environment.

MU scientists are looking at simple, low-cost techniques that farms and animal-feed operations might use to trap and neutralize antibiotics in animal waste. "We want to be able to help farmers in the state do what they need to feed the population and continue to be good stewards of the environment," said Keith Goyne, a soil scientist with MU's School of Natural Resources.

Many livestock producers use antibiotics to treat sick animals. Healthy livestock may also receive antibiotics in their feed in order to promote growth. Thirty to 80 percent of any given dose of antibiotic may end up excreted as waste rather than absorbed by the animal. When manure is used to fertilize croplands, antibiotics in the manure may get into the soil and eventually end up in streams, lakes or rivers.

"The amounts are relatively low," said Goyne. But no one knows much about the long-term effect these compounds might have on humans, animals and the environment. "I think we should be concerned but not alarmed."

According to Goyne, a tiny dose in our tap water is not the only potential problem. Antibiotics, which are designed to kill disease-causing bacteria, could wreak havoc on microbial communities in the soil. One consequence might be the emergence of antibiotic-resistant bacteria that could infect humans, livestock and wildlife.

Antibiotics also might disrupt essential biological activity in the soil. "Microorganisms are essential to life on earth," said Goyne. "They conduct processes such as nutrient cycling, organic matter decomposition and a variety of other functions. Without them behaving as they should, agriculture would change substantially."

Goyne is collaborating with MU assistant professor of forestry Chung-Ho Lin, professor of soil science Steven Anderson and two USDA soil scientists based at MU, Robert Lerch and Robert Kremer. They are investigating the use of vegetative buffers to control the spread of antibiotics in surface runoff from fields treated with manure.

Studies by MU soil scientists have already shown that grass buffers in croplands can help contain nutrients and herbicides by reducing runoff and degrading the chemical compounds.

"We're fairly confident that these buffers will work well for antibiotics, but it's yet to be tested," said Goyne.

Vegetative buffers serve as a filter for surface runoff. Placing buffers between rows of crops allows the buffers to intercept runoff as it flows downhill. Using the right plants in buffers is important. All plants change the physical, chemical and biological properties of the soil in which they grow. Using specific plant species can make the soil a more effective filter by increasing its ability to physically trap sediment and by promoting a diverse community of microorganisms that can decompose certain chemical compounds.

"We're looking at buffers that have just grass species as well as tree-grass buffers, which we call agroforestry buffers," he said.

In field tests at the MU Bradford Research and Extension Center, the researchers are dousing small plots with a rainfall simulator to test the effectiveness of different buffer designs in reducing concentrations of antibiotics in surface runoff. In the laboratory they are applying antibiotics to soil samples and analyzing the results: Using high-performance liquid chromatography, the scientists can measure parts-per-billion levels of antibiotics in solution. A technique called infrared spectroscopy allows researchers to detect the infrared wavelengths absorbed by the soil samples. This combination of wavelengths serves as a "fingerprint" for identifying changes in the organic-matter composition of the soil induced by different plant species in the buffer.

"Noting such changes will improve understanding of how the buffers influence retention of the antibiotics in soil," Goyne said.

Preliminary results have shown promise. "We're seeing that soil that has been extracted from the root zone of a poplar tree is enhancing the degradation of at least one of the antibiotic drugs we're looking at," said Goyne. "That shows us that the microorganisms in the soil where the poplar tree is growing are helping to break this compound down, which will prevent it from remaining in the environment for long periods of time or moving on to surface water resources."

The research is funded by the University of Missouri Center for Agroforestry. For more information about the center, go to http://www.centerforagroforestry.org.