| environmental aspect of human settlements Human settlements have an adverse impact on many ecosystems and on themselves by the addition of toxic or harmful substances to the outer lithosphere, hydrosphere, and atmosphere. The major types of environmental pollutants are sewage, trace metals, petroleum hydrocarbons, synthetic organic compounds, and gaseous emissions. Most, if not all, of the additions of potentially harmful substances to the environment are result of the population growth and the technological advances of industrial societies | الجانب البيئي للمستعمرات البشرية |