Hui Zhi successfully defended her PhD in December 2020, toasting with her colleagues in a virtual congratulations celebration. In a normal year, they would have gone out to celebrate—one last goodbye before Zhi left for her new job at Peking University in China.

Her thesis was on the concentrations of pharmaceuticals in a local point-source waterway. She and her advisor, IIHR’s Greg LeFevre, spent over three years collecting samples, identifying chemicals, and determining concentrations of foreign substances in a small stream in Coralville, Iowa. The sampling site sits just downstream of the North Liberty Wastewater Treatment Plant, known for its excellent membrane bioreactor. When the bioreactor was installed in 2008, it was the best money could buy.

Both Zhi and LeFevre stress the high quality of the water coming from the treatment plant. The membrane bioreactor is doing its job—dissolving harmful chemicals from agricultural runoff, human, and natural waste. Even so, there are measurable pharmaceuticals still present in the water.

LeFevre says the resulting effluent—even from the best wastewater treatment plants—will still have residual pharmaceuticals that then impact the local waterways unless the plant is specifically designed to remove them.

He also explains that most of the pharmaceuticals come from everyday use.

“I sprained my wrist the other day and I took an ibuprofen, right? Well, eventually, that gets into the wastewater treatment plant—all the things that we take do. Some of the things that we’ve found are kind of obvious. In the summertime, there’s a really high amount of antihistamines. Well, those are allergy medicines. That’s kind of what you’d expect in Iowa in the summertime.”

Zhi and LeFevre worked closely with teams from the U.S. Geological Survey and the University of Wisconsin-Milwaukee, who are each conducting their own research at the sampling sites. The researchers from UW-Milwaukee are looking into biological effects the pharmaceuticals have on the local fish population by submerging lab-raised fish in the Coralville water. Combined with the information collected on effluent concentrations from the University of Iowa, there could be potential implications for human health.

Zhi believes the associations between human health and the health of fish are important to understand.

“I guess that’s the part people will care [about] most,” she says, “how they impact fish, and we eat fish, and then it can potentially impact us.”

She explains further that, though the pharmaceuticals are found near the wastewater treatment plant, water is mobile, and thus the content of the water from the wastewater treatment plant can transfer to new water sources. When water goes through drinking water treatment plants, the pharmaceuticals cannot be entirely removed, leaving residual pharmaceuticals in Iowa drinking water.