Seoul's tap water recently became safe to drink, with city officials branding it "Arisu" in a bid to convince the public. Efforts have also been made with afforestation projects. Another multibillion-dollar project was the restoration of Cheonggyecheon, a stream running through downtown Seoul that had earlier been paved over by a motorway. One major challenge is air quality, with acid rain, sulfur oxides, and annual yellow dust storms being particular problems. It is acknowledged that many of these difficulties are a result of South Korea's proximity to China, which is a major air polluter. South Korea had a 2019 Forest Landscape Integrity Index mean score of 6.02/10, ranking it 87th globally out of 172 countries.