How are organic phosphates formed? How do they get into the environment?

Organophosphates are man-made chemicals, which are widely used as insecticides in agricultural applications. They get into the environment because we put them there. Fortunately, they degrade quite rapidly in the environment, but nonetheless find their way into drinking water supplies in small quantities. They're very potent neurotoxins (some are used as chemical weapons - nerve gases), so their presence in the environment is a concern... but they're good insecticides for crops.