The environmental movement (sometimes referred to as the ecology movement), is a social movement that aims to protect the natural world from harmful environmental practices in order to create sustainable living. Environmentalists advocate the just and sustainable management of resources and stewardship of the environment through changes in public policy and individual behavior. In its recognition of humanity as a participant in (not an enemy of) ecosystems, the movement is centered on ecology, health, and human rights. The environmental movement is an international movement, represented by a range of environmental organizations, from enterprises to grassroots and varies from country to country. Due to its large membership, varying and strong beliefs, and occasionally speculative nature, the environmental movement is not always united in its goals. At its broadest, the movement includes private citizens, professionals, religious devotees, politicians, scientists, nonprofit organizations, and individual advocates like former Wisconsin Senator Gaylord Nelson and Rachel Carson in the 20th century. The origins of the environmental movement lay in response to increasing levels of smoke pollution in the atmosphere during the Industrial Revolution. The emergence of great factories and the concomitant immense growth in coal consumption gave rise to an unprecedented level of air pollution in industrial centers; after 1900 the large volume of industrial chemical discharges added to the growing load of untreated human waste. Under increasing political pressure from the urban middle-class, the first large-scale, modern environmental laws came in the form of Britain's Alkali Acts, passed in 1863, to regulate the deleterious air pollution (gaseous hydrochloric acid) given off by the Leblanc process, used to produce soda ash. Early interest in the environment was a feature of the Romantic movement in the early 19th century.