New Swedish research has confirmed earlier reports that residues from human contraceptives in lakes, rivers and sea water may threaten fish reproduction.
Scientists at the universities in Umeå and Gothenburg filled aquariums with water that had passed through three different sewage treatment plants – including the biggest one in Stockholm – and let rainbow trout live there for two weeks, when blood samples were taken and analysed.
According to an article in Stockholm daily Dagens Nyheter, 21 of 25 substances the researchers were looking for were found in the samples, including concentrations of levonorgestrel that were even higher than for women on oral contraceptives.
Levonorgestrel is a synthetic progestogen used as an active ingredient in some hormonal contraceptives, and in even higher concentrations in some so-called “morning-after pills”. A recent German study found that even less than a billionth of that substance per litre of water seriously affects fish’s egg production, and such levels were found in the sewage water in the Swedish study.
A spokesperson for the main sewage treatment plant in Stockholm admitted that medical residues could be removed to a much higher extent, but to much higher costs.