The expansion of cities, pollution from mining and tourism are exacerbating challenges for waste management in mountain regions - but a new report led by UN Environment shows how policymakers can prevent it. Mountain cities in developing countries are often expanding into areas vulnerable to natural disasters such as steep hills or riverbanks, finds the study, titled 'Waste Management Outlook for mountain regions - sources and solutions' launched in Vienna on the occasion of the International Mountain Day. The resulting waste generation can be staggering. The 7.8 magnitude earthquake that struck Nepal in April 2015 produced nearly four million tons of debris in the Kathmandu valley. This was equivalent to nearly 11 years of waste being generated in a single day, overwhelming sanitary landfill sites, which were in place in only five out of 191 municipalities. In the specific case of natural disasters, immediate waste management is essential to prevent disease and limit impact on the environment. Disaster waste management plans should also be drawn-up before they are required to make best use of scarce resources.