Across East Asia, the blight of air and water pollution is spreading in the wake of economic development, not just within countries but across borders to damage the quality of life in neighbouring nations and regions. The recurrence of choking air pollution in Hong Kong originating from the transport, industry and cities of Guangdong, and the pall of smoke from forest fires in Indonesia drifting over Malaysia and Singapore, are unwelcome reminders of this downside of growth. So, too, are the complaints from states in Southeast Asia about China's new dams on the upper reaches of the Mekong River. The Chinese barrages are blamed, perhaps unfairly, for declining water flow and fish catches in the lower reaches of Southeast Asia's largest river. Some political analysts say that cross-border environmental disputes could worsen as the pressure of population on available natural resources increases and the consequences are exacerbated by global warming. Scientists meeting in Stockholm, Sweden, this week warned that the risk of wars being fought over water is rising because of rapid population growth in some parts of the world and lack of effective action by governments. Conflict over access to dwindling supplies of fresh water appears most likely within and between countries in the Middle East, Africa and South Asia. For example, India wants to divert water from South Asian rivers, prompting claims that it will turn parts of neighbouring Bangladesh into desert and cause unseasonal flooding in Nepal. In East Asia, air pollution is the major cross-border environmental problem. Dust and sand storms affect Northeast Asia nearly five times as frequently as they did 50 years ago, according to a study by the United Nations Environment Programme (UNEP) released this year. The storms come from the dry regions of northern China and Mongolia, where excessive grazing and farming, deforestation and climate change have contributed to the spread of deserts. A single storm can dump more than 8,000 tonnes of sand on South Korea, according to the country's Rural Development Agency. UNEP warned that the phenomenon was a threat to people's health and to economies in the region, with disruptions and losses amounting to US$6.5 billion a year. The 1997-98 fires in Southeast Asia are estimated to have cost regional economies over US$9 billion in damage to health, farming, transport and tourism. The Northeast Asian dust storms blow across the Korean Peninsula and Japan. On the way, they pick up toxic pollutants in the industrial belt along China's east coast. The Korean Peninsula and Japan, as well as China itself, have also been affected by acid rain caused by sulfur dioxide emissions from Chinese coal-burning power plants. A massive tree-planting programme is under way to stem the spread of deserts in China. Tighter controls to reduce acid-rain damage have been imposed by Chinese authorities. But because these environmental problems transcend borders, they complicate the responses. For example, efforts by Hong Kong and Guangdong to tackle the Pearl River Delta's pollution together are being stymied by their differing political and legal systems. Still, South Korea, Japan and China have established a system of monitoring and early warning of dust and sand storms, and such efforts are getting support from UN agencies, the World Bank and the Asian Development Bank. Effective national action and better international co-operation are the best way forward. Michael Richardson, a former Asia editor of the International Herald Tribune, is a visiting senior research fellow at the Institute of Southeast Asian Studies in Singapore. The views expressed in this article are those of the author