For instance , fish exposed to treated sewage effluents were found to have concentrations of the synthetic hormone levonorgestrel in blood plasma higher than those found in humans taking hormonal contraceptives .
This can lead to unintended ecological consequences .
Fish exposed to treated sewage effluents were found to have concentrations of the synthetic hormone levonorgestrel in blood plasma higher than those found in humans taking hormonal contraceptives .
This can lead to unintended ecological consequences .