"measured in quantities of parts per billion or trillion" I don't think we have a lot to worry about.
If you read the whole article, you will see that scientists and even a director for a major pharmaceutical company would beg to differ:
"But at a conference last summer, Mary Buzby - director of environmental technology for drug maker Merck & Co. Inc. - said: 'There's no doubt about it, pharmaceuticals are being detected in the environment and there is genuine concern that these compounds, in the small concentrations that they're at, could be causing impacts to human health or to aquatic organisms.'
Recent laboratory research has found that small amounts of medication have affected human embryonic kidney cells, human blood cells and human breast cancer cells. The cancer cells proliferated too quickly; the kidney cells grew too slowly; and the blood cells showed biological activity associated with inflammation." (bold added by me)