Environmental policy is the framework and means by which public decisions take into account the natural, nonhuman environment. The origins of environmental policy in modern cities can be traced to efforts at comprehensive planning. Early examples include John Claudius Loudon's Breathing Places plan for London in 1829, Frederick Law Olmstead's work on Boston's Emerald Necklace beginning in about 1878, and Daniel Burnham's 1909 Plan for Chicago. Such plans incorporated the felt need for green spaces that would improve the physical beauty of cities, living conditions, and public access to nature. In the early stages of industrialization, cities turned to environmental policy to mitigate air and water pollution from industry and inadequate sanitation infrastructure and thus to prevent damage to human health.