Pharmaceuticals in the Aquatic Environment: Steroids and Anti-Steroids as High Priorities for Research

Many human pharmaceuticals, with many modes of action, are present in the aquatic environment. It is very difficult to know which of these might pose a threat to aquatic organisms, and which are of no environmental concern. Hence, it is difficult to design a research strategy that most effectively maximizes the possibility of identifying those pharmaceuticals that do pose the greatest risk. We consider that steroidal pharmaceuticals, and drugs that inhibit the actions of endogenous steroids, merit more research than they have yet received so far. We analyzed a comprehensive U.K. database covering all prescriptions of pharmaceuticals to determine the annual usage of all steroid and anti-steroid pharmaceuticals. We found that both progestogens and glucocorticoids are used in much greater amounts than estrogens, whereas androgens are used in similar amounts to estrogens. There is also very significant use of anti-estrogens, anti-androgens, and anti-mineralocorticoids. All these pharmaceuticals are likely to be constantly entering the aquatic environment in effluents from sewage treatment works. River concentrations of these pharmaceuticals will be very low; probably in the ng or sub-ng/l range. However, such low concentrations mat still pose a threat to aquatic organisms, especially fish.