how city light pollution is affecting us. E.g. turtle hatchlings are disoriented by city lights and head for the light rather than the ocean. Some birds migrate at night, and use star maps in their heads to navigate; city lights disorient them. And birds attracted to lights fly into buildings. As for humans, breast cancer is 1.5X to 2X higher among shift workers. In rat studies, have found that tumors grow less or shrink more with high melatonin blood than low melatonin blood. Darkness increases the melatonin levels in the blood substantially (sigh).