On the Effect of Probability Distributions of Input Variables in Public Health Risk Assessment

A central part of probabilistic public health risk assessment is the selection of probability distributions for the uncertain input variables. In this paper, we apply the first-order reliability method (FORM)^(1–3) as a probabilistic tool to assess the effect of probability distributions of the input random variables on the probability that risk exceeds a threshold level (termed the probability of failure) and on the relevant probabilistic sensitivities. The analysis was applied to a case study given by Thompson et al. ⁽⁴⁾ on cancer risk caused by the ingestion of benzene contaminated soil. Normal, lognormal, and uniform distributions were used in the analysis. The results show that the selection of a probability distribution function for the uncertain variables in this case study had a moderate impact on the probability that values would fall above a given threshold risk when the threshold risk is at the 50th percentile of the original distribution given by Thompson et al. ⁽⁴⁾ The impact was much greater when the threshold risk level was at the 95th percentile. The impact on uncertainty sensitivity, however, showed a reversed trend, where the impact was more appreciable for the 50th percentile of the original distribution of risk given by Thompson et al. ⁴ than for the 95th percentile. Nevertheless, the choice of distribution shape did not alter the order of probabilistic sensitivity of the basic uncertain variables.     

Perception of Ecological Risk to Water Environments

This paper examines lay and expert perceptions of the ecological risks associated with a range of human activities that could adversely affect water resource environments. It employs the psychometric paradigm pioneered in characterizing perceptions of human health risks, which involves surveys to obtain judgments from subjects about risk items in terms of several important characteristics of the risks. The paper builds on a previous study that introduced ecological risk perception. This second study employs a larger, more diverse sample, a more focused topic area, and comparisons between lay and expert judgments. The results confirm that a small set of underlying factors explain a great deal of variability in lay judgments about ecological risks. These have been termed Ecological Impact, Human Benefits, Controllability , and Knowledge. The results are useful in explaining subjects' judgments of the general riskiness of, and need for regulation of, various risk items. The results also indicate several differences and areas of agreement among the lay and expert samples that point to potential key issues in future ecological risk management efforts for water resources.     

ATSDR Science Panel on the Bioavailability of Mercury in Soils: Lessons Learned

On the basis of discussion and analysis during and following an ATSDR science panel on the bioavailability of mercury in soils, it is apparent that the default assumption of 100% relative bioavailability for mercury-contaminated soils is excessively conservative. However, current knowledge does not allow the development of default assumptions or guidelines for determining relative bioavailability of mercury in soils. Until such default assumptions or guidelines can be developed, site-specific assays of bioavailability, preferably using either animal bioassays or validated in vitro techniques, may provide the best approach for estimating soil-mercury bioavailability.     

不同规模农地抵押贷款可得性研究

以南阳市427户农户调查数据为样本,运用二元Logit回归模型对三类不同土地规模农户的农地抵押贷款可得性及其影响因素进行分析。结果发现,户主年龄、文化程度、家庭收入、房屋价值、社会资本、对贷款政策了解度及土地规模差异均对农户农地抵押贷款可得性具有显著影响。其中,家庭收入与房屋价值是影响不同土地规模农户农地抵押贷款可得性的共同因素,土地规模是影响农地抵押贷款可得性最为直接的关键性因素,随着土地规模增加,金融机构贷款审批更注重农户个人信用程度、社会资本和风险保障措施。     

西部山区农民易地扶贫搬迁意愿的影响因素

从现在到2020年是打赢脱贫攻坚战的关键时期,从农民自身角度研究搬迁意愿,对加快实施易地扶贫移民搬迁具有重要意义。研究依据西方微观人口迁移理论：地方效用理论、计划行为理论和效价[CD*2]期望理论,整合构建了中国国情下由政府引导的易地扶贫搬迁意愿的理论分析框架。以陕南移民搬迁为例,在验证性因子分析的基础上,运用有序Logit模型和最优尺度模型对理论假设进行检验。结果显示：①心理因素、政策和预期因素、环境因素对搬迁意愿具有显著影响 ②控制变量中家庭人口数、非农劳动力比例、家庭成员求学婚姻等控制变量与搬迁意愿显著相关;③没有搬迁的主要的顾虑是搬迁后找不到工作、城镇生活成本高、搬迁成本高、搬迁后的适应等问题。研究建议政府部门在搬迁补助、就业安置、搬迁后适应等方面加大支持力度,增强搬迁的信心。     

农地流转与农户金融需求

以四川省为例,基于647份农户调查数据,从农地流转、农户基本情况、农户经营特征、农村金融市场特征4个方面运用Logit模型实证分析其对农户金融需求的影响方向及强度,分析农地流转背景下农户金融需求的影响因素。研究结果表明,农地流转行为带来农户金融需求分化趋势,农地流转价格过快上涨对农户金融需求有明显抑制作用,加快创新农村金融产品已经十分紧迫,农户普遍面临缺乏抵押融资能力的困境。农地流转对农户金融需求的分化性发展产生重要影响,进而对我国农业的转型升级具有极为积极的促进作用。在进一步深化农村土地产权制度改革基础之上,重点针对扩大土地经营规模的农户进行农村金融产品创新,有效满足其不断增长的金融需求,则是当前我国推进现代农业发展必须破解的主要难题。     

东道国外债规模与中国OFDI——基于发展中国家面板数据的研究

本文利用2003—2013年间中国对外直接投资跨国面板数据,采用系统GMM方法,实证研究发展中国家外债规模与中国OFDI的关系.研究发现,在发展中国家或地区,外债规模与中国对外直接投资存在正向关系.此外,我们还得到东道国外债规模均会弱化市场规模、自然资源、技术水平对中国OFDI的正向作用.     

论概率安全评价中的组织风险因素

核电站组织风险已经成为核电站安全运行重要的影响因素,在概率安全评价中考虑组织风险因素是核电安全研究的重要课题。文章在建立组织风险因素与PSA之间转换的概念框架的基础上,对组织风险因素进行分类。分类后的组织风险因素受人员行为形成因子的影响,其影响在人因可靠性分析中进行分析。计算和评估这些人员行为形成因子对于事故后操纵员的影响可以计算组织因素对核电站安全的影响。     

城市规模、创业边界与企业家创业

大城市更有活力且更年轻化的人口结构,导致大城市的消费者异质性偏好更强,进而可能推动企业家创业边界的降低与城市创业活动的发展。为了识别这一理论机制,本文在Zhelobodko et al.（2012）的分析框架上,通过引入城市规模和消费者异质性偏好假设,构建了一个异质性企业家区位选择与创业的空间经济学模型,考察城市规模通过企业家创业边界对城市创业活动的影响,并基于2000-2016年204个城市的面板数据以及2008年中国经济普查数据进行了实证检验。研究发现：（1）企业家才能越高的企业,相应的产品定价会越低,产品需求量越大,而利润越高;（2）企业家创业边界除了受到城市规模的影响以外,还会受到消费者多样性偏好的影响;（3）消费者多样化偏好更强的城市,城市的创业门槛更低,城市的创业活跃度更高。     

Assessing Risk‐Based Upper Limits of Melamine Migration from Food Containers

Melamine contamination of food has become a major food safety issue because of incidents of infant disease caused by exposure to this chemical. This study was aimed at establishing a safety limit in Taiwan for the degree of melamine migration from food containers. Health risk assessment was performed for three exposure groups (preschool children, individuals who dine out, and elderly residents of nursing homes). Selected values of tolerable daily intake (TDI) for melamine were used to calculate the reference migration concentration limit (RMCL) or reference specific migration limit (RSML) for melamine food containers. The only existing values of these limits for international standards today are 1.2 mg/L (0.2 mg/dm²) in China and 30 mg/L (5 mg/dm²) in the European Union. The factors used in the calculations included the specific surface area of food containers, daily food consumption rate, body weight, TDI, and the percentile of the population protected at a given migration concentration limit (MCL). The results indicate that children are indeed at higher risk of melamine exposure at toxic levels than are other groups and that the 95th percentile of MCL (specific surface area = 5) for children aged 1–6 years should be the RMCL (0.07 mg/dm²) for protecting the sensitive and general population.