ADB_book_18 April.qxp - Himalayan Document Centre - icimod

World Bank in 1990 estimated impacts on mortalityand morbidity due to PM10 levels. The study estimatedthat Kathmandu’s PM10 levels resulted in 84 casesof excess mortality, 506 cases of chronic bronchitis,4,847 cases of bronchitis in children, and 18,863asthma attacks per year. Overall, Kathmandu’sresidents experienced over 1.5 million respiratorysymptom days per year (Shah and Nagpal 1997).An analysis of the records of 369 COPD patientsand 315 control patients admitted to Patan Hospitalfrom April 1992 to April 1994 showed that the odds ofhaving COPD are 1.96 times higher for KathmanduValley residents compared with outside residents.The study also stated that over the past decade theproportion of COPD patients had increased morethan fourfold and that COPD was the number onekiller of adult patients in the hospital (CEN andENPHO 2003).The records from three major hospitals inKathmandu indicate that the number of COPDpatients admitted to hospitals, as well as the numberof COPD patients as a percentage of all patients, hasincreased significantly in the last ten years. Hospitalrecords also indicate that the number of COPDpatients is highest in the dry winter months, when airpollution in Kathmandu is at its peak (Figure 7.12).Vehicular pollution and suspended dust from poorlymaintained roads are the major causes for the poorair quality in urban centers.Another observable impact is on visibility.Atmospheric data obtained from Kathmandu airportfrom 1970 onwards shows a substantial decrease invisibility in the Valley since 1980. The trend towardsreduced visibility in the Valley has been quitedramatic for the months November–March, andparticularly for December–February. The number ofdays with good visibility (>8,000 m) at 11:45 amdecreased in the winter months from more than 25Figure 7.12: Air Pollution Level in Kathmandu andIncidence of Chronic Destructive Pulmonary Disease(COPD) Patients as a Percentage of All Patientsdays/month in 1970 to 5 days/month in 1992. By 1997,the number of days per month in December–February with good visibility at noon approachedzero (Sapkota et al. 1997).The impacts of air pollution are felt not only onhealth but also on vegetation and in corrosiondamage to buildings and monuments. Air pollutioncan inflict significant damage on local vegetation.The information collated by Regional Air Pollution inDeveloping Countries during the initial phase of theCrops and Forests Project has clearly shown that inmany developing countries, and particularly in partsof Asia, crop yields and forest productivity are beingseverely affected by local ambient air pollutantconcentrations. In the context of South Asia, there isa strong linkage between monsoon activity andagricultural productivity. In the last decade, Nepaland the Indo-Gangetic plains of India experiencedsevere sky overcast during winter, affecting majorwinter crops like potato, oilseeds, pulses, and onion.Yield reduction in 1997/98 ranged from 11% to 38%compared with the average of the preceeding 10years. The precise reasons for this, however, are notyet clear. Frequent occurrence of cold waves and fogmixed with dust particles in the atmosphere could bethe cause. Likewise, reduction of solar radiationcould be the explanation. Aerosols can directly alterthe hydrological cycle by suppressing evaporationand rainfall. With respect to agricultural changes, itcan directly impact productivity by shadingvegetation from solar radiation; and indirectlythrough induced changes in temperatures and thehydrological cycle (UNEP and C4 2002).Climate and Climate ChangeNepal’s ClimateThe climate in Nepal varies from tropical to arcticwithin the 200 km span from south to north. Much ofNepal falls within the monsoon region, with regionalclimate variations largely being a function ofelevation. National mean temperatures hover around15°C, and increase from north to south with theexception of the mountain valleys. Average rainfall is1,500 mm, with rainfall increasing from west to east.The northwest corner has the least rainfall, situatedas it is in the rain shadow of the Himalayas. Rainfallalso varies by altitude—areas over 3,000 mexperience a lot of drizzle, while heavy downpoursare common below 2,000 m. Although annual rainfallis abundant, its distribution is of great concern.Flooding is frequent in the monsoon season duringsummer, while droughts are not uncommon incertain regions in other parts of the year.Data Source: Limbu (2005)Chapter 7: Air Pollution and Climate Change91