Chronic toxicity of diphenhydramine hydrochloride to a freshwater mussel, Lampsilis siliquoidea, in a flow-through, continuous exposure test system.

Freshwater mussel populations are declining in North America. Potential anthropogenic stressors may be contributing to the declines and may include the continual presence of pharmaceutical compounds in waterways. Diphenhydramine hydrochloride (DH) is an over-the-counter antihistamine marketed under several name brand products including the common U.S. trademarked product, Benadryl™. The toxicity of DH to freshwater mussels was assessed by initiating an unprecedented 28 day, continuous exposure trial with 1 day old mussels. Results indicated that the survival and growth of Lampsilis siliquoidea was not impacted by DH concentrations ≤121 μg/L after 28 days of continuous exposure. With the successful completion of this study, the techniques are now verified to evaluate the toxicity of waterborne compounds initiating 28-day chronic exposures with 1 day old mussels.