Environmental factors can affect human health in important ways, both positive and negative. Positive environmental factors sustain health, and promoting them is preventive medicine.
Environmental health comprises those aspects of human health, including quality of life, that are determined by the following types of factors: physical, chemical, biological as well as social and psychosocial (Credit: World Health Organization, Public health and environment).
The quality of our planet's air affects not only our health as we breath it, but has wide impacts on vegetation and, very critically, climate change.
Water, the mainstay of life on Earth affects humanity in many ways, from providing drinking water and water for our vegetation and food, to the oceans, and their temperature and currents, and their levels, which, if they change, could flood many densely inhabited regions.
Sunlight, so necessary for humans, our food, and the planet we live on, can also sometimes be harmful - e.g. UV radiation - unless we understand why and when and are adequately warned.