Kristine Wammer

Kristine Wammer and Her Students Take on a Major Source of Environmental Pollutants

I am a “farm kid.” I grew up on a corn and soybean farm in southern Minnesota that truly was the middle of nowhere, with the nearest town (Butternut) having a population that hovered around a dozen. Having no kids nearby meant that my brother Todd and I had to come up with creative – if slightly dangerous – ways to entertain ourselves, including bicycle polo and constructing tree platforms of questionable structural integrity. Other days we “bean walked” with my father and grandfather; bean walking was walking through row after row of soybeans keeping our trained eyes peeled for invading weeds. Volunteer corn from last year’s crop rotation? Knock it down with the garden hoe you’ve carried along. Buttonweed? Pull it out by the roots and set it on its head or it will grow back. By the time I was a teenager, we were sitting on the front of a tractor versus walking the rows. Squirt wand in hand and a big tank of pesticide behind us, we gave weeds a spray as we drove by.

My college years found me at St. Olaf College in Northfield, Minn., where I did work in chemistry and environmental studies. My motivation stemmed from my interest in, and concern about, the practices that are used to grow crops and raise animals. I wanted to learn more about how human activities are impacting our environment, particularly freshwater sources like those impacted by the runoff from my family’s farm.

I moved to Princeton University for my graduate work. There, I studied pollutants called polycyclic aromatic hydrocarbons (PAHs), which are components of oils and tars and byproducts when fossil fuels are burned. My work contributed to our understanding of how quickly bacteria can break these molecules down in the environment. I examined how easily various PAHs can get into the bacterial cell and be transformed by enzymes within the cell. I returned to Minnesota to perform postdoctoral work at the University of Minnesota; in an interdisciplinary project (with advisers in chemistry, civil engineering and environmental health sciences), my work focused on a class of contaminants of relatively recent concern – pharmaceuticals and personal care products (PPCPs).

At St. Thomas, my work has continued to focus on PPCPs. Numerous studies have reported the occurrence of pharmaceuticals at low levels in surface waters, and interest in this topic has moved beyond the scientific literature to the popular press. For example, a story by the Associated Press highlighted the occurrence of pharmaceuticals in the  drinking water supply of at least 41 million Americans. Extensive research is ongoing to determine the potential effectiveness of various treatment processes for removing pharmaceuticals in waste-water treatment plants. Legislation has been proposed both at the state and national levels to regulate use or disposal of pharmaceuticals; a bill recently passed by the Minn. House and Senate will regulate pharmaceutical disposal while a current bill in the U.S. Congress would restrict the use of antibiotics for agricultural purposes. While the environmental occurrence of these compounds clearly has spurred interest in both the scientific community and the public realm, major gaps still remain in our understanding of their significance and potential health and ecological impacts; therefore, the critical question of which PPCPs are of the most concern is still largely unanswered.

The primary goal of my research group is to elucidate some of this needed information about what happens to PPCPs (fate) and what kind of impacts they may have (effects) in the environment. Our research projects are designed to efficiently identify PPCPs of likely concern to focus future monitoring campaigns, treatment strategies and regulatory efforts. We have been directing most of our effort to date toward one subset of PPCPs: antibiotics. This is due to concern about the potential threat of development of enhanced antibacterial resistance due to long-term exposure to low levels of antibiotics.

We have completed several projects designed to understand the role sunlight plays in breaking down antibiotics in sunlit surface waters; this is called photodegradation, and the resultant transformation products are called photoproducts. We are particularly interested in potential biological activity of photoproducts. Identifying all photoproducts for all antibiotics found in natural waters does not seem a practical goal, especially when it is anticipated that the majority of these products will not have ecological significance. It is also not acceptable, however, to ignore the potential for products to have impacts; therefore, we use a bacterial assay as a screening tool to identify those compounds for which photoproducts may retain antibacterial activity. This allows us to focus efforts for comprehensive product identification on those compounds for which it is necessary, and to provide valuable information as to which compounds may be of the most long-term concern. In related projects over the past few years, we have expanded beyond looking at reactions due to natural sunlight and begun studying reactions that occur during water-treatment processes. As is the case for photochemical transformations in natural systems, a major interest of ours is in understanding the significance of transformation products. We wish to efficiently determine whether water treatment strategies may be creating molecules that retain biological activity. While all of our published work in environmental fate of PPCPs has involved antibiotics, we recently have expanded into examining potential endocrine disruptors. In collaboration with Dr. Dalma Martinovic-Weigelt from the University of St. Thomas Biology Department, we are using breast cancer cell assays to assess whether photoproducts of UV-filter molecules used in sunscreens are likely to have significant estrogenic activity.

On the effects side, we are very interested in the potential for the low, subtherapeutic antibiotic concentrations that are found in natural waters to result in proliferation of antibacterial resistance among environmental bacteria. Resistant environmental bacteria are of concern because they can serve as a reservoir for antibiotic resistance genes that can potentially be transferred to pathogenic strains. Our work to date primarily has focused on the impacts of triclosan, a commonly used topical antibacterial compound (e.g. handsoap, toothpaste), on bacterial communities in natural waters from Lake Superior to the San Francisco bay area to local waters impacted by waste-water treatment plants (WWTPs). In our most recent project, we are looking at several classes of antibiotics in collaboration with researchers at the University of Minnesota and Gustavus Adolphus College. We are measuring antibiotic concentrations and antibiotic resistance among bacterial communities at several sites and hoping to elucidate the relative impacts of agricultural and human-based sources. Our study sites are in a portion of the Minnesota River basin and include those same drainage ditches I fished in when taking a break from bean walking as a child.

I have conducted all of my projects at St. Thomas in collaboration with my incredibly able and fun group of undergraduate research students. My six current group members range from freshmen to seniors; all work full time during the summer and squeeze in as many hours as they can during the academic year. They learn so much from this part of their St. Thomas experience: how to communicate their findings clearly, orally and in writing; how to design experiments and refine those experiments as they learn more; and how to fail and keep trying until they succeed. My group alumni have done well with their post-St. Thomas ventures. Three are in graduate school, with three more headed that way next fall. Two are in medical school, two are working as chemists and one as a high school chemistry teacher. I couldn’t be more proud of all of these wonderful students with whom I have had the privilege to work, and I am excited to keep discovering important information about contaminants in our waters with future generations of Tommies.

Kristine Wammer is associate professor of chemistry at the College of Arts and Sciences.

 From Exemplars, a publication of the Grants and Research Office.