CHRONIC TOXICITY OF DIPHENHYDRAMINE HYDROCHLORIDE TO LAMPSILIS SILIQUOIDEA IN A FLOW-THROUGH, CONTINUOUS EXPOSURE TEST SYSTEM

Jeffery R. Meinertz, Theresa M. Schreier, Karina R. Hess, and Jeffry A. Bernardy
USGS Upper Midwest Environmental Sciences Center, La Crosse WI

Pharmaceuticals and personal care products (PPCP) are a group of compounds that include prescription and over-the-counter drugs, detergent by-products, fragrances, and cosmetics. These compounds are continually introduced into the aquatic environment largely through wastewater treatment plants. Many PPCP have been documented in streams throughout the U.S. (Kolpin et al. 2002). To assess the potential impacts of PPCP on aquatic invertebrate organisms in the St. Croix National Scenic Riverway, a comprehensive project titled, "Demonstration of an approach to assess the impact of emerging contaminants on aquatic invertebrates in national parks: A project for the St. Croix National Scenic Riverway" was launched. The objectives of the project were to (1) determine the occurrence and concentration of PPCP in water and sediments of the Riverway, (2) evaluate the effects of PPCP found in the Riverway on chronically exposed Daphnia, and (3) evaluate the effects of PPCP on chronically exposed juvenile freshwater mussels. Diphenhydramine hydrochloride (DH; trade name, Benadryl™, an over-the-counter antihistamine, sedative, and hypnotic) was found in the effluent from the St. Croix Falls, WI wastewater treatment plant and in water samples downstream from the plant. The toxicity of DH to chronically exposed aquatic invertebrate organisms had not been characterized until our lab recently conducted a study with Daphnia magna. Results from this study indicated that D. magna were negatively impacted by chronic exposure to DH at concentrations >71µg/L. In this presentation we report the effects of DH on a chronically exposed juvenile mussel species native to the Riverway.

We assessed the toxicity of DH to juvenile Lampsilis siliquoidea continuously exposed for 28 d using a test system and techniques (consideration given to ASTM 2005) developed by our research staff initiating the trial with 1-day post transformation mussels. The study design included a control group and 5 groups exposed to DH at nominal concentrations of 0.5, 2.5, 12.5, 50, or 100 µg/L (concentrations based on results from the Daphnia trial). Each treatment group consisted of 10 test chambers (250 mL beakers, water volume, 200 mL, containing a 4-mm layer of silica sand), each stocked with 40 1-day post transformation L. siliquoidea. Water flow through each test chamber was continuous. A food suspension prepared daily with various algae flowed through each chamber continuously. Chambers assigned to the exposure treatment groups had solutions of DH flowing through them continuously for 28 days. After 28 d, the numbers of surviving mussels were assessed. Percent survival in the control group was 85%. Percent survival in the exposed groups ranged from 76% in the 12.5 µg/L treatment group to 86% in the 2.5 µg/L treatment group. In conclusion, the survival of L. siliquoidea was not impacted by DH concentrations as high as a nominal concentration of 100 µg/L. Analyses assessing the effect of DH on mussel growth are in progress.

References

American Standards for Testing and Materials Designation E 2455-05. 2005. Standard guide for conducting laboratory toxicity tests with freshwater mussels. ASTM International, West Conshokocken, Pennsylvania.

Kolpin, D.W., E.T. Furlong, M.T. Meyer, E.M. Thurman, S.D. Zaugg, L.B. Barber, and H.T. Buxton. 2002. Pharmaceuticals, hormones, and other organic wastewater contaminants in U.S. streams, 1999-2000: A national reconnaissance. Environmental Science and Technology, 36:1202-1211.