initially slated for completion in July 2011. Air pollution Since 2006, significant air pollution, largely attributed to external sources in India, has manifested in a brown haze in the atmosphere above Bhutan. This air pollution resulted in decreased crop output and increased concerns about public health. Bhutan's four cement plants have been cited as some of the most prevalent causes of domestic air pollution, with three out of four running without modern emission controls. Semiannual NEC site visits check for compliance with existing regulation and may impose relatively trivial fines, however living conditions remained poor due to dust. Enforcement has been portrayed as lax in Bhutanese media, and complaints by some residents around the Pasakha industrial center went unaddressed. Through 2011, many thromdes and smaller villages in Bhutan had pits or areas for burning refuse due to a lack of designated landfills or disposal sites. The practice increases ambient air pollution as well as air and ground toxicity. In 2011, the NEC began setting up stations to monitor air quality in Thimphu, Kanglung, Pasakha and Rinchending. Biodiversity Biodiversity, a hallmark of Bhutan, is threatened by human activity and climate change. To address these problems, the Royal Government began setting aside protected areas in the 1960s. Since 1992, protected areas of Bhutan have been managed by the Bhutan Trust Fund for Environmental Conservation under the Ministry of Agriculture, Forestry Services Division. In 1993, the Fund revised and reduced its extensive parks system for better ecological representation and management. Through 2008, however, protected areas expanded significantly with the establishment of Wangchuck Centennial Park, spanning a swath in northern Bhutan. The parks and sanctuaries are all connected either directly or by "biological corridors." Bhutan is regarded by some as the best example in the world of setting aside a high proportion of a country's area to maintain the ecologies of protected areas by constructing corridors without financial consequences, as reviewed by Wangchuk 2007 and reflected in the study of Lham et al 2019. As of 2011, the Fund had recruited 189 field staff, had trained 24 post-graduate specialists, and had provided over 300 short scientific courses. The Fund alone manages a total protected area of – nearly the size of Eswatini and more than 42 percent of Bhutan's total . With the exception of Phibsoo Wildlife Sanctuary and Torsa Strict Nature Reserve, these protected areas are inhabited or are located within populated areas.