Answer:
There is a chance that the person receiving that insulin will get a bad immune response, and there is a possibility that the animal might have a disease or infectious organisms, that their insulin might contain, and putting it inside a human might transmit that disease.
Explanation:
First of all, it makes algae grow, because pesticides and stuff provide too many nutrients. Algae needs a lot of oxygen and so the fish begin to die off because the algae is taking all the oxygen out of the lake. Next, it causes biodiversity to drop, meaning that species are beginning to get less varied. Water pollution harms the lakes and is a concern because the effects of it on species and the water will stay.