The U.S. Department of Agriculture (USDA) has awarded a University of Delaware researcher a $400,000 grant to study the fate and transport of hormones and antibiotics in runoff from agricultural watersheds.
The grant was awarded to Shreeram Inamdar, an associate professor of bioresources engineering in UD's College of Agriculture and Natural Resources, through the competitive 2009 Agricultural and Food Research Initiative program on water and watersheds. Diana Aga, who is an associate professor with the Department of Chemistry at the University at Buffalo (N.Y.) is a co-principal investigator on the project.
The occurrence of hormones and antibiotics in the environment has received considerable attention in both the scientific and mainstream media. Synthetic and natural steroidal hormones are considered endocrine disrupting chemicals (EDCs) because they can cause physiological and reproductive disorders in aquatic and wildlife species, Inamdar said.
While the concentrations of hormones in surface waters are typically small -- parts per billion or parts per trillion levels -- they are effective enough to cause impairment, especially when aquatic and wildlife species are continuously exposed to a cocktail of such chemicals over long periods of time, Inamdar said.
The environmental contamination by pharmaceutical residues, especially antibiotics, may promote antibiotic resistance in pathogenic microorganisms and contribute to phytotoxicity, he said.
Inamdar and Aga will evaluate the fate, persistence, transport, and potency of animal hormones and antibiotics, including their transformation products, in an agricultural watershed receiving land-application of poultry litter.
The target hormones include estrone, estradiol, estriol, and their sulfate and glucuronide conjugates. The target antibiotics that will be studied include chlortetracycline, representing the tetracycline class of antibiotics, and sulfamethazine, representing the sulfonamide class of antibiotics.
Sources of hormones in agricultural watersheds include runoff from agricultural land receiving applications of poultry litter or animal manure; discharge from concentrated animal feeding operations; and runoff from cattle grazing lands, Inamdar said.
While hormones are produced naturally by poultry, cattle, and swine and are excreted in urine and feces, he said, they are also introduced anthropogenically when used for growth promotion, for increased egg and milk production, and for disease prevention in animal agriculture.
Residues of human and veterinary pharmaceuticals are introduced into the environment via a number of pathways, Inamdar said, but primarily from discharges of sewage or wastewater treatment plants or land application of sewage sludge and animal manure. Most antibiotics are transformed only partially in the body and thus are excreted into the animal waste as a mixture of parent compounds and metabolites.
In the United States, he said, more than 50 million pounds of antibiotics are produced each year and approximately 40 percent of these are used in animal industry for treating diseases and for growth promotion.
Inamdar and Aga will conduct their research in agricultural watersheds located adjacent to the St. Andrew's School in Middletown, Del. UD, through the College of Agriculture and Natural Resources, has initiated a research and education partnership with the St. Andrew's School to demonstrate sustainable watershed management practices and to educate students and the broader community about these practices.
Recent field-scale studies conducted by Inamdar, Aga and Tom Sims T. A. Baker Professor of Soil and Environmental Chemistry and associate dean of the College of Agriculture and Natural Resources, at the St. Andrew's watersheds indicated that the concentrations of hormones in runoff from plots receiving poultry litter were fairly low and below environmental thresholds for concern. The concentrations were even lower for plots that received poultry litter in pelletized form, Inamdar said.
He said these results are encouraging because they suggest adoption of best management practices can help reduce the threat of contaminants. Results from this study are currently in review with a leading scientific journal.
Inamdar said this newly funded project “will further our understanding of hormones and antibiotics beyond the field-scale to the larger watershed-scale and investigate how landscape features such as riparian forests, wetlands, and vegetated filter strips impact the transport and fate of these contaminants.”
These landscape features are also important best management practices recommended for watershed protection and management, he said.
“This study will be conducted over a period of three years and thus also evaluate the influence of seasons and storm events on the persistence and transport of these chemicals in the watershed,” Inamdar said.