Fertilizers, in contrast to pesticides, are not deliberately designed to kill life and are not directly toxic either to wild animals and plants or to ourselves. They are contaminants of the environment, rather than pollutants. Under certain conditions, though, they play an important role in chemical reactions in the environment that do result in significant pollution. Nitrates and phosphates can result in eutrophication ofrivers, lakes and coastal waters; nitrates are converted inside ourselves and other animals to produce nitrites that are toxic; and nitrous oxide, given off to the atmosphere, takes part in both the depletion of the ozone layer and global climatic warming.