Phytotoxicity of Pharmaceuticals and Personal Care Product Ingredients.

Municipal wastewater treatment plant effluents typically contain a variety of pharmaceutical compounds. In arid and semi-arid areas of the U.S. and other countries, reclaimed wastewater (RWW) is often used for irrigation, resulting in exposure of crop plants to pharmaceuticals. Crops irrigated with RWW may take up pharmaceuticals through their roots. However, the likelihood of their bioaccumulation in food crops is still not well understood.  Plants may respond to pharmaceuticals in a concentration-dependent manner that affects their uptake. Furthermore, the possibility exists that some pharmaceuticals may exert toxicity on plants. The limited overlap in molecular receptors between plants and vertebrates complicates a priori prediction of phytotoxic effects. 

We investigated responses of the model plant Arabidopsis thaliana to a range of pharmaceuticals commonly found in RWW including anticonvulsants, antidepressants, β-blockers, anti-histamines, and others.  A. thaliana was selected because it matures rapidly, its genome has been fully sequenced, and a variety of mutants are available. We screened 18 pharmaceuticals for uptake and translocation to above-ground tissues and found that carbamazepine, diphenhydramine, propranolol, trimethoprim, fluoxetine, and amitriptyline were among the compounds taken up to the largest extent in aerial tissues. We evaluated a subset of the pharmaceuticals for effects on A. thaliana.  Initial studies have focused on inhibition of root elongation in seedlings. These studies represent a first step toward determining molecular responses of A. thaliana to pharmaceuticals.