Demand for environmental policies to improve health: Evaluating community-level policy scenarios

Using a national survey and a discrete choice experiment format, we estimate demand for environmental polices to improve health. We use a richly detailed community-level approach that describes illnesses avoided, premature deaths avoided, policy duration, and the affected population size. We allow preferences for policy attributes to vary systematically with the scenario design, with the source of risk and type of health threat, and with respondent characteristics. Using a willingness to pay (WTP) framework similar to that used for studies of individual risk, we find that omission of illness information leads to an upward bias in estimates of the value of avoided premature deaths and that individuals view avoided deaths and avoided illnesses as substitutes. We also find evidence of strongly diminishing marginal utility in policy scope. Differences in marginal WTP from different sources of risk or types of illness appear very small relative to differences associated with respondent characteristics and/or perceptions. Self-interest strongly dominates altruistic considerations.     

Influence of Environmental Contamination with PCBs on Human Health

Statistical data on different sicknesses have been processed to evaluate the dynamics of human health in Serpukhov City (an administrative centre in the Moscow region of Russia) and to estimate the contribution of ecological factors to the total level of morbidity. Chlorinated biphenyls (PCBs) appear to be among the most dangerous contaminants of the ecosystem that includes the urban areas and those lands, which are actively used for vegetable production. A preliminary health risk calculation for PCBs has been done using soil contamination data. We estimated the share of cancer attributable to soil contamination with PCBs to be approximately 6% of the value of total cancer morbidity in Serpukhov. The highest level of soil pollution by PCBs occurred in the district of the city where the highest values of some other sicknesses also were located. The results of this study could be useful for decision-making and planning of environmental policy in the city.     

Assessment of age-dependent radiation dose and toxicity risk due to intake of uranium through the ingestion of groundwater from Northern Rajasthan,India

Uranium traces were measured by laser fluorimeter in groundwater samples collected from four districts of Rajasthan state in India. The average values of uranium concentration in groundwater in Sri Ganganagar, Hanumangarh, Churu, and Sikar districts were determined to be: 57, 50, 40, and 21 µg L^?1, respectively. These recorded values were compared with the maximum contamination levels recommended for drinking water by various health and environmental protection agencies. The associated age-dependent radiation dose is estimated by taking the prescribed water intake values of different age groups. The average cancer mortality and morbidity risks are calculated to be 5.6 × 10^?5 and 8.8 × 10^?5 respectively, indicate that the probability of carcinogenic risks is negligible. About half (49%) of the analyzed samples showed hazard quotient > 1.0, indicating significant risk due to chemical toxicity of uranium.     

Valuation of human health: An integrated model of willingness to pay for mortality and morbidity risk reductions

This paper develops and applies an integrated model of mortality and morbidity valuation that is consistent with the principles of welfare economics. To obtain the integrated model, the standard one-period expected utility model of one person facing the prospect of either being alive or dead is extended to incorporate (1) a third health state (sick) with a utility level that is intermediate to utility if healthy and utility if dead, (2) a family perspective in which a parent makes choices about risk exposure both for herself and for a child, and (3) a multi-period framework that allows for possible parent/child differences in illness latency. Monetary benefits of health risk reduction obtained from the integrated model are compared with those that would be computed using the standard model. The integrated model then is applied using data obtained from two field studies of skin cancer and leukemia to demonstrate how it can be used to estimate health benefits of reduced illness and death risks.     

Uncertainty and measurement error in welfare models for risk changes

Most welfare models of environmental or mortality risk reductions assume that risks are exogenously determined and known with certainty. However, a growing body of research suggests that uncertainty about risks can affect choices over risky prospects. I present a decision-weighted random-utility model that decomposes welfare losses into those attributable to an increase in the deterministic component of risk and those attributable to uncertainty about risk. I apply the model to an illustrative dataset of subjects' perceived mortality risk and willingness to accept the risk of nuclear-waste transport. I estimate the model using Lewbel's (2000) strictly exogenous regressor approach to account for endogeneity bias and measurement error. Subjects display aversion to both risk and uncertainty about the risk of a transport accident, so that increases in either leads to social-welfare losses. Roughly 12% of the external cost of nuclear-waste transport is attributable to the public's uncertainty about transport risk.     

Evidence of variable discount rates and non-standard discounting in mortality risk valuation

Time discounting is central to the valuation of future health and mortality risks in public sector allocative decision-making, particularly for environmental policies with delayed health impacts. Using a Risk-Risk trade-off survey, we elicit discount rates for fatality risks and establish discounting functional forms on both a sample and an individual level. We find wide variation in implicit discount rates for fatality risk between individuals, as well as between-individual heterogeneity in discounting functional forms. In aggregate, the sample is best characterised by subadditive discounting. Our work has implications for the academic investigation of intertemporal choice involving mortality risks, and potentially for the evaluation of policy options with delayed mortality risk outcomes. A thought experiment cautions against the standard practice of assuming that exponential discounting characterises society's time preferences.     

Spatial elements of mortality risk in old-growth forests

For many species of long-lived organisms, such as trees, survival appears to be the most critical vital rate affecting population persistence. However, methods commonly used to quantify tree death, such as relating tree mortality risk solely to diameter growth, almost certainly do not account for important spatial processes. Our goal in this study was to detect and, if present, to quantify the relevance of such processes. For this purpose, we examined purely spatial aspects of mortality for four species, Abies concolor, Abies magnifica, Calocedrus decurrens, and Pinus lambertiana, in an old-growth conifer forest in the Sierra Nevada of California, USA. The analysis was performed using data from nine fully mapped long-term monitoring plots. In three cases, the results unequivocally supported the inclusion of spatial information in models used to predict mortality. For Abies concolor, our results suggested that growth rate may not always adequately capture increased mortality risk due to competition. We also found evidence of a facilitative effect for this species, with mortality risk decreasing with proximity to conspecific neighbors. For Pinus lambertiana, mortality risk increased with density of conspecific neighbors, in keeping with a mechanism of increased pathogen or insect pressure (i.e., a Janzen-Connell type effect). Finally, we found that models estimating risk of being crushed were strongly improved by the inclusion of a simple index of spatial proximity. Not only did spatial indices improve models, those improvements were relevant for mortality prediction. For P. lambertiana, spatial factors were important for estimation of mortality risk regardless of growth rate. For A. concolor, although most of the population fell within spatial conditions in which mortality risk was well described by growth, trees that died occurred outside those conditions in a disproportionate fashion. Furthermore, as stands of A. concolor become increasingly dense, such spatial factors are likely to become increasingly important. In general, models that fail to account for spatial pattern are at risk of failure as conditions change.     

基于自然灾害的北京幅综合生态风险评价

经过20多年的发展,风险源评价从单一风险源扩展到多风险源,风险受体从单一受体发展到多受体,评价尺度也从种群、生态系统扩展到区域和景观水平。但总体说来,对多风险源、多过程的多个生态系统层次的风险评价尚不成熟。运用数字高程模型、干燥度分布图、植被指数、人口密度以及8种自然灾害风险源频率分布图、土地利用图、植被类型图、陆地生态系统生态资产分布图等数据,基于ArcGIS 9.2平台,综合考虑生态的脆弱性,风险源的发生频率,受体的暴露水平、危害程度等,对多风险源、多个生态系统综合的北京幅生态风险进行评价。旨在对区域综合生态风险评价方法进行探讨。评价结果显示：（1）高风险区主要为本区环渤海湾沿岸,包括天津市,河北唐山、沧州,山东滨州、东营、潍坊等沿海地带;以及本图幅西部、北部的太行山地,包括河北省、北京市及图幅西部的山西、河南部分地区;（2）较低生态风险区所占比例较高,达42.55%,可见降低生态风险有很大的潜力;（3）高强度的人类开发,尤其是在滨海地区围海造陆,将会导致沿海地区生态风险更高。     

Ideal free distributions under predation risk

 We examine the trade-off between gathering food and avoiding predation in the context of patch use by a group of animals. Often a forager will have to choose between feeding sites that differ in both energetic gain rate and predation risk. The ideal site will have a high gain rate and low risk of predation. However, intake rate will often decrease when the patch is shared with other foragers and it may be optimal for some individuals to feed elsewhere. Within the framework of ideal free theory, we investigate the distribution of foragers that will equalise individual fitness gains. We focus on a two-patch environment with continuous inputs of food. With reference to existing experimental studies, we examine the effects of risk dilution, food input rates and an animal’s expectations of the future. We identify the effect of total animal numbers when one patch is subject to predation risk and the other is safe. Conditions under which the difference in intake rate in the two patches is constant are identified, as are conditions in which the ratio of animals in the two patches is constant. If current conditions do not alter future expectations an increase in input rates to the patches promotes increased use of the risky patch. Yet, if conditions are assumed to persist indefinitely the opposite effect is seen. When both patches are subject to predation risk, dilution of risk favours more extreme distributions, and may lead to more than one stable distribution. The results of these models are used to critically analyse previous work on the energetic equivalence of risk. This paper is intended to help guide the development of new experimental studies into the energy-risk trade-off. Received: 10 February 1995/Accepted after revision: 1 October 1995     

兰州地区人群对多环芳烃的暴露及健康风险评价

采用多介质-多途径暴露模型,评价兰州地区居民暴露于多环芳烃的健康风险,分析风险来源、暴露介质及暴露途径,并结合蒙特卡罗方法分析研究过程中的不确定性。结果表明,兰州地区居民中男性和女性对环境中多环芳烃的终身日平均暴露量分别为4.55×10-4和5.07×10-4mg.kg-1.d-1。暴露途径中食物摄取是最主要途径,食物中贡献较大的为谷物。相应的男性和女性的健康风险度分别为4.12×10-5.a-1和4.80×10-5.a-1,兰州地区多环芳烃类污染物居民人体健康风险度远远高于可接受健康风险度的标准。兰州地区女性对多环芳烃的暴露量高于男性,女性健康风险平均值亦远远高于EPA标准值,兰州地区女性乳腺癌发病率较高可能与长时间低剂量多环芳烃暴露有一定的关系。兰州地区多环芳烃人群暴露与天津和北京相比存在一定的差异。