environment protection environmental pollution 62 environment 60 permanently sustainable development 51 ecology 49 air pollution 42 waste disposal services 37 more ... wastes 36 recycling of wastes 30 water courses 23 environmental management 22 unconventional energy sources 22 ecosystems 17 atmosphere (biology) 15 environmental law 15 power engineering 14 water pollution 14 water management 13 health harmful substances 13 contaminants 13 coolants 12 issues 12 environmental policy 12 biofuels 11 sewerage 11 air cleanness monitoring 11 Earth warming 11 landscape recultivation 11 construction materials 11 cooling mechanisms 10 less ...