هزینه های اقتصادی ذرات معلق آلودگی هوا بر سلامت در سنگاپور

The rapid process of urbanization and industrialization in developing countries and newly industrialized countries (NIC) over the past few decades has resulted in degradation in air quality in these countries. However, accompanying this phenomenon has been the growing realization that economic development and environmental management are mutually supporting goals. The paper attempts to address this concern by estimating the economic cost of particulate air pollution on health in Singapore. Using the damage function/dose response approach, the mortality and morbidity effects of particulate air pollution on the population of Singapore are estimated. In addition, the economic values of these health impacts are also calculated in terms of the statistical lives which could be saved and the cost of illness incurred. The results show that the cost of particulate air pollution (PM10) in Singapore is substantial both in absolute and relative terms. It is estimated that the total economic cost US $3662 million is about 4.31% of Singapore’s GDP in 1999. The findings thus strengthen the assertion that policy-makers should not ignore the environment in their pursuit for economic progress.

Developing countries and newly industrialized countries (NIC) face the twin challenges of protecting the environment while also strengthening their economies. Over the past few decades, the intensified process of urbanization and industrialization undertaken by these countries, coupled with rapid population growth, has resulted in the degradation of the environmental quality. Particularly, the emission of harmful pollutants such as sulfur dioxide (SO2), nitrogen oxide (NO2), lead, ozone and particulate matter has contributed considerably to a rapid drop in the air quality in the cities. Among the air pollutants, particulate matter was found to be the most damaging. Particulate includes dust, dirt, soot, smoke, and liquid droplets directly emitted into the atmosphere by sources such as factories, power plants, transportation sources, construction activity, fires, and windblown dust. They are also formed in the atmosphere by condensation of emitted gases such as sulfur dioxide, nitrogen oxides, and volatile organic compounds into tiny droplets. The concentration of particles in the air can be measured either as an average over a defined time period, usually 20 h, or continuously using newer types of particle monitors called continuous samplers. Concentration is expressed in micrograms of particles per cubic meter of air sampled (μg/m3). Particles get into the body through our lungs whereas larger particles settle in our mouth and nose. The particulate size measurement used, known as PM10, includes particles with an aerodynamic diameter of 10 μm or less. These particles are of health concern as they are able to penetrate deep into the sensitive regions (thoracic or lower regions) of the respiratory tract. Thus, PM10 are also known as inhalable particles. Recent studies on the effects of chronic exposure to air pollution have identified PM10 as the pollutant most responsible for the life-shortening effect of dirty air. The major concerns for human health include effects on breathing and respiratory symptoms, aggravation of existing respiratory and cardiovascular disease, alterations in the body’s defense systems against foreign materials, damage to lung tissue, carcinogenesis and premature death. Particulate exposure might increase susceptibility to bacterial or viral respiratory infections, leading to an increased incidence of pneumonia in vulnerable members of the population. It might also aggravate the severity of underlying chronic lung disease, causing more frequent or severe exacerbation of airway disease or more rapid loss of lung function. Besides its adverse impact on human health, particulate matter can also result in visibility degradation. This can affect the residents and tourists’ aesthetic visions of nature. Moreover, visibility degradation can take on a much more serious nature when it interferes with the navigation of vehicular traffic on highways and around airports. These environmental impacts are undoubtedly serious from a road and air safety perspective. The soiling effect of particulate matter is another environmental impact. When particulate fall out of the atmosphere, they can accumulate on people’s cars, laundry drying outside, and in their homes. Thus, elevated levels of atmospheric particulate can have a “nuisance impact” on the environment. In view of the various negative impacts particulate air pollution has on the environment, the issue of the improvement of this aspect of air quality (e.g., reduction in the concentration level of particles in the air) is becoming a major concern for both the general public and the governments of the developing countries and NICs. Nearly every Asian capital is now choking on its own economic success. For example, air pollution is expected to more than triple in Seoul and Bangkok between 1991 and 2000, and more than double in Taipei, Jakarta and Kuala Lumpur (Berfield, 1996). Even though Singapore is often cited as an exception, there are little by way of any study in Singapore which can reaffirm this belief. Thus, this paper attempts to provide more insights into the epidemiological and valuation relationships of particulate air pollution which is apparently lacking in Singapore. If cost of particulate air pollution were substantial, it would highlight the importance of not ignoring the environment in pursuing economic progresses. Given the available epidemiological data, PM10 may be regarded as an important and useful indicator for the health risk of air pollution. We use PM10 as the main indicator for air pollution and its impact on health as the proxy for the estimation of the economic cost of particulate air pollution. 1.1. Effects of particulate air pollution on health The most troubling finding from many recent scientific health studies in the air pollution epidemiological literature is that increase in ambient concentrations of particulate matter under 10 μg (PM10) is associated with increase in the risk of premature mortality. Dockery et al. (1993) found that the risk of early death in areas with high levels of particulate air pollution was 26% higher than in low-level areas. Pope et al. (1995) also found an association between exposure to particulate air pollution and premature mortality due to cardiopulmonary causes. Using the data obtained from 15 European cities, the investigators of Air Pollution on Health: European Approach (APHEA) project found that a 50 μg/m3 increase in PM10 results in a 2.1% increase in total mortality in the Western European cities (Katsouyanni et al., 1996). For the association between increased PM10 concentrations and mortality to be plausible, it would be expected that increases in PM10 would also be associated with less severe effects on health than death. There is strong evidence suggesting that short-term increase in ambient concentrations of PM10 is associated with increase in PM10-related morbidity. Pope (1996) found that in addition to increased mortality the health effects of elevated PM10 pollution observed in Utah Valley include decreased lung function, increased incidence of respiratory symptoms, increased school absenteeism, increased respiratory hospital admissions, and possibly increased lung cancer. Forsberg, Stjernberg, Falk, Lundback, and Wall (1993) found a positive association between daily variation in particulate pollution levels—even at levels below the U.S. air quality standards—and severe shortness of breath in people with asthma. Several other studies done in the United States also provide empirical support for the relationship between PM10 and morbidity (see Ransom & Pope, 1992, Schwartz, 1994a, Schwartz, 1994b and Schwartz & Morris, 1995). 1.2. Assigning economic values to health risks Once the links between emissions to human health effect have been established, the next stage requires the assignment of economic (monetary) value to the predicted health effects. In the case of health effects, the monetarization approach should determine values according to individual stated preferences (willingness to pay). It has been argued that if people’s preferences are a valid basis upon which to make judgments concerning changes in human well being, then it follows that changes in human mortality and morbidity should also be valued according to what individuals are willing to pay or willing to accept as compensation to forgo the change in health status (Maddison et al., 1996). However, when it comes to the valuation of human life, the moral and ethical considerations involved greatly transcend the economic analysis undertaken. Conflicts between the ethical arguments against the placing of a monetary value on human life and the economic analysis involved arise because of the misunderstanding of the concept of the valuation of “human life.” The value of a statistical life should not be confused with the value of a human life. The value of a statistical life (VOSL) is the value of a small change in the risks associated with an unnamed member of a large group dying ( Dixon, Scura, Carpenter & Sherman, 1994). In another word, it represents an individual’s willingness to pay (WTP) for a marginal reduction in the risk of being dead. There are several approaches to measure the VOSL i.e., Hedonic Value Methods—Property-value Approach and Compensating Wage Differential Approach, Preventive Expenditures Approach and Contingent Valuation Method (CVM). As a result of the differences in the approaches used, it is not surprising to see widely varying empirical estimates of the VOSL in the literature (see Fisher, Chestnut & Violette, 1989; Miller, 1990 and da Motta & Mendes, 1994). As for the valuation of reduced morbidity, it can be done by using approaches that measure individual’s WTP or by using the cost of illness (COI) approach. COI measures the total cost of illness that is imposed on the society. These costs include value of the lost productivity (loss in earnings) due to illness, medical costs such as hospital care, home health care, medicine, services of the doctors and nurses; and other related out-of-pocket expenditures. Table 1 summarizes the results from several studies that were done to estimate the economic costs of air pollution damage to human health from particulate matter (PM10). The economic costs of health damage per capita in developing countries appear fairly consistent in the range of US $15 to US $247. One key point to note about these studies is the tendency to use consensus dose-response functions (DRFs) in their estimation of the economic cost of air pollution. Hence the cost of particulate air pollution in terms of its impacts on human health will be largely determined by the size of the population at risk and the unit economic values used to value the increase in mortality and morbidity.

By making use of Singapore data on levels of ambient concentration of PM10, and the population at risk of particulate air pollution, combined with the “transferred” dose-response coefficients and unit economic values of the effects of mortality and morbidity, this paper provides, the first study albeit, some rough estimates of the economic impact of particulate air pollution on health in Singapore. Based on our estimation, it is obvious that the cost imposed on society is substantial both in absolute and relative terms. Table 9 shows that the total estimated mortality and morbidity cost related to PM10 pollution are US $1773 million and US $1889 million, respectively. Adding up the total mortality and morbidity costs, the total estimated economic cost of health damage attributable to particulate air pollution in Singapore is US $3662 million. This is about 4.31% of total GDP of the country in 1999. Total mortality cost accounts for about 2.09% of total GDP while total morbidity costs accounts for some 2.22% while the health damage costs per capita in Singapore is estimated to be around US $941. The estimated values are much smaller when change in PM10 is assumed to be 9.7 μg/m3.The study is limited in two aspects. Firstly, as mentioned earlier the paper uses DRFs and unit economic values for mortality and morbidity effects estimated in the developed countries for the estimation of the cost of particulate air pollution since no study has been conducted in Singapore before. In a strict sense, these adapted values may not apply in the Singapore context. As such, the estimates presented in the exercise should only be regarded as rough, “back-of-the-envelope” estimates of the economic costs of the environmental issue considered. Secondly, as Pearce (1996) noted, a major weakness of the air pollution damage literature has been the focus on outdoor pollution. In terms of human person hours, 68% of all developed country person hours are spent indoors in urban environments and 21% are spent indoors in rural environments, leaving only 11% of time in the outdoors. In the developing countries, the proportions are 70% and 30%. In other words, the major part of an individual’s time is spent indoors, not outdoors (Smith, 1988). However, it is not possible to estimate environmental costs without information on the level of environmental quality. Thus, given the paucity of data on indoor air quality in Singapore, only outdoor air quality has been considered in our estimation of the economic costs of PM10 pollution in Singapore. In view of the limitations discussed above, the findings of this paper have to be treated as indicative rather as conclusive. Nevertheless, some important insights emerge from the analysis of the results obtained from the exercise. The substantial cost of particulate air pollution that is estimated seems to provide strong support for the assertion that economic development and environmental management are mutually supporting goals. Furthermore, it appears that the reductions in the level of ambient concentrations of PM10 do have the potential to yield substantial health benefits in Singapore—benefits that are equal to a very significant percentage of the GDP. The findings of the study thus bear on policy-makers in Singapore in a very important way. The results obtained underscore the importance of controlling particulate beyond that would be required by international standards, given the significant contribution of this air pollutant to health damage and the high values the population placed on these damages in Singapore. The possible policy initiatives include energy conservation and vehicle traffic control measures. In fact, air pollution studies have suggested a focus on the transport sector rather than the traditional power station sector because of the relatively stronger association of particulate matter with vehicle emissions. In addition, the occurrence of recent haze episodes has also reiterated the fact that air pollution ignores borders. As such, policy made on environmental management should no longer be restricted within the country in question only, but rather such decisions should represent a concerted effort involving countries within the same region. The paper also highlights the large uncertainties involved in the economic valuations of environmental amenities like clean air. Uncertainties “range from questions about the existence of a health effect, to statistical uncertainties about the value of coefficients, to issues about what dollar values should be assigned to various benefit categories” (NERA, 1990). To reduce these uncertainties, the best approach is to establish dose–response relationship of local (Singapore) PM10 and conduct studies investigating the values that residents in Singapore actually place on clean air. Although data collection to establish DRFs and values will be neither easy nor cheap, such efforts could provide the impetus for more in-depth analysis of the environmental impacts of air pollution in Singapore. By estimating the economic impact of particulate air pollution on health in Singapore, this paper has shed some light on the epidemiological and valuation relationships of PM10 pollution in Singapore. Even though the findings are only rough estimates of the likely environmental costs of the situation analyzed, it is hoped that the findings could contribute, in some way or another, to Singapore’s goal of becoming a “Tropical City of Excellence.”