Global Health Impacts and Costs Due to Mercury Emissions

Since much of the emission is in the form of metallic Hg whose atmospheric residence time is long enough to cause nearly uniform mixing in the hemisphere, much of the impact is global. This article presents a first estimate of global average neurotoxic impacts and costs by defining a comprehensive transfer factor for ingestion of methyl-Hg as ratio of global average dose rate and global emission rate. For the dose-response function (DRF) we use recent estimates of IQ decrement as function of Hg concentration in blood, as well as correlations between blood concentration and Hg ingestion. The cost of an IQ point is taken as $18,000 in the United States and applied in other countries in proportion to per capita GDP, adjusted for purchase power parity. The mean estimate of the global average of the marginal damage cost per emitted kg of Hg is about $1,500/kg, if one assumes a dose threshold of 6.7 μg/day of methyl-Hg per person, and $3,400/kg without threshold. The average global lifetime impact and cost per person at current emission levels are 0.02 IQ points lost and $78 with and 0.087 IQ points and $344 without threshold. These results are global averages; for any particular source and emission site the impacts can be quite different. An assessment of the overall uncertainties indicates that the damage cost could be a factor 4 smaller or larger than the median estimate (the uncertainty distribution is approximately log normal and the ratio median/mean is approximately 0.4).     

Costs of Health Damage from Atmospheric Emissions of Toxic Metals: Part 1—Methods and Results

Significant quantities of toxic metals are emitted to the air by the incineration of waste, as well as by the combustion of coal and oil. To optimize the regulations for their emissions one needs to know the cost of their damage. That requires an impact pathway analysis, with realistic dispersion models, exposure‐response functions, and monetary values. In this article we explain the method and assumptions and present results for arsenic, cadmium, mercury, and lead, the most important toxic metals in terms of damage cost. We also estimate their contribution to the damage cost of waste incineration and electric power from coal for typical situations in Europe. The damage costs of As, Cd, and Pb are much higher than previous estimates because of a large number of new epidemiological studies, implying more and more serious health effects than what had been known before. New cost‐benefit studies for the abatement of toxic metal emissions are advisable. The discussion of the epidemiological studies and the derivation of exposure‐response functions are presented in two companion articles, one for As and Cd, the other for Hg and Pb.     

An International Pooled Analysis for Obtaining a Benchmark Dose for Environmental Lead Exposure in Children

Lead is a recognized neurotoxicant, but estimating effects at the lowest measurable levels is difficult. An international pooled analysis of data from seven cohort studies reported an inverse and supra‐linear relationship between blood lead concentrations and IQ scores in children. The lack of a clear threshold presents a challenge to the identification of an acceptable level of exposure. The benchmark dose (BMD) is defined as the dose that leads to a specific known loss. As an alternative to elusive thresholds, the BMD is being used increasingly by regulatory authorities. Using the pooled data, this article presents BMD results and applies different statistical techniques in the analysis of multistudy data. The calculations showed only a limited variation between studies in the steepness of the dose‐response functions. BMD results were quite robust to modeling assumptions with the best fitting models yielding lower confidence limits (BMDLs) of about 0.1–1.0 μ g/dL for the dose leading to a loss of one IQ point. We conclude that current allowable blood lead concentrations need to be lowered and further prevention efforts are needed to protect children from lead toxicity.     

Benefactors and Beneficiaries: The Effects of Giving and Receiving on Cost‐Coalitional Problems

Motivated by supply chain collaborations in practice, we introduce a class of cost‐coalitional problems, which are based on a priori information about the cost faced by each agent in each set that it could belong to. Our focus is on problems with decreasingly monotonic coalitional costs. In this class of problems, we study the effects of giving and receiving when there exist players whose participation in an alliance always contributes to the savings of all alliance members (we refer to these players as benefactors), and there also exist players whose cost decreases in such an alliance (we call them beneficiaries). We use linear and quadratic norm cost games to analyze the role played by benefactors and beneficiaries in achieving stability of different cooperating alliances. We consider different notions of stability (the core and the bargaining set) and provide conditions for stability of an all‐inclusive alliance of agents which leads to minimum value of total cost incurred by all agents.     

碳排放交易对实现我国“十二五”减排目标的成本节约效应研究

本文针对实现我国"十二五"期间减排目标的现实背景,构建了一个省际排放权交易模型,重点探讨了在实现各省减排目标的过程中,碳排放权交易机制发挥的成本节约效应。研究设置了无碳交易市场(NETS)、仅包含北京等六个碳交易试点省市的碳交易市场(PETS)和全国范围内实施碳排放权交易(CETS)三种政策情景。通过模型分析得到以下结论:(1)为实现"十二五"碳强度减排目标,扣除自然下降率,全国二氧化碳排放需要减少约6.39亿吨,占当年总碳排放的6.65%;无碳排放交易时全国需要付出约157.62亿元的减排成本,占当年GDP的0.04%;六省市参与碳交易情景下,全国总的减排成本约为150.66亿元,节约减排成本4.42%,碳交易量为0.22亿吨CO₂,占总减排量的3.39%,均衡碳价约为70.55元/吨CO₂;全国碳市场情景下,全国总的减排成本约为120.68亿元,相比于无碳排放交易情景节约减排成本23.44%,碳交易量为1.21亿吨CO₂,占总减排量的18.98%,均衡碳价约为38.17元/吨CO₂;(2)碳交易市场对参与交易的省份的成本节约效应各不相同,总的来看,东、西部地区成本节约较为明显,部分西部地区能够在完成自身减排目标前提下,通过加入碳交易市场而获取正的收益。     

Evaluation of Methods for Assessing the Oral Bioavailability of Inorganic Mercury in Soil

The risks associated with environmental exposures to inorganic mercury are typically assessed based on toxicity studies conducted with the soluble salt, mercuric chloride (HgCl₂). Evidence indicates, however, that inorganic mercury is present in soil as a variety of compounds and that oral absorption of inorganic mercury decreases with a decrease in the solubility of the mercury compound being studied. Thus, while HgCl₂ is approximately 15–20% bioavailable, the bioavailability of cinnabar (HgS) may be 30- to 60-fold less. The solubility and, hence, bioavailability of inorganic mercury in soil is expected to be substantially less than that of HgCl₂ due to the presence of less soluble compounds and their interactions with soil constituents. Quantification of this difference in bioavailability is important in assessing potential risks associated with exposure to mercury-containing soil. A review of available studies supports the expectation that mercury bioavailability in soils will be reduced. This paper reviews methods for assessing soil metal absorption with consideration of the characteristics of the oral absorption of elemental and inorganic mercury that should be evaluated in designing additional studies. Because of the very slow elimination of mercury in some species, it is recommended that a repeated-dose study be conducted. Such a study would yield an estimate of relative bioavailability based on a comparison of tissue mercury concentrations in animals ingesting soil with those of animals receiving HgCl₂. The dose, age, gender, and species of animal selected are not expected to affect relative bioavailability estimates; however, it is recommended that studies be conducted in two animal species. Rats should be used because they have been used in many studies of mercury absorption and toxicity. A species of large animals such as monkeys, swine, or dogs should also be used to provide confirmation in a species with greater similarities to humans in gastrointestinal physiology and anatomy. Other critical factors in designing these studies, such as selection and characterization of soil samples, are also addressed.     

Policy Incentives for Dangerous (But Necessary) Operations

In industries where firms perform dangerous (but necessary) operations, liability costs—due to potential harm to third parties—can be significant. Firms may therefore find it optimal to exit the market, and this may lead to an inefficiently low number of incumbents. A social planner can discourage exit by offering appropriately designed subsidies. Ex ante subsidies defray the costs associated with making operations safer (e.g., funds to subsidize the purchase of safety equipment). Ex post subsidies mitigate the financial damages caused by an accident (e.g., funds to defray the cost of cleaning up a toxic spill). We consider a model where (i) firms have private information about their ability to improve reliability and (ii) reliability investments are unobservable. We demonstrate that when the social value of reliability outweighs the benefit of increased competition, it is optimal to offer ex ante subsidies alone (i.e., to subsidize the cost of making operations safer). Conversely, when the benefits of competition outweigh the benefits of reliability, a combination of ex ante and ex post subsidies is optimal (i.e., not only to subsidize safer operations, but also to share the costs of a potential accident).     

Cost‐Effective Sampling and Analysis for Mycotoxins in a Cereal Batch

The presence of hazards (e.g., contaminants, pathogens) in food/feed, water, plants, or animals can lead to major economic losses related to human and animal health or the rejection of batches of food or feed. Monitoring these hazards is important but can lead to high costs. This study aimed to find the most cost‐effective sampling and analysis (S&A) plan in the cases of the mycotoxins deoxynivalenol (DON) in a wheat batch and aflatoxins (AFB₁) in a maize batch. An optimization model was constructed, maximizing the number of correct decisions for accepting/rejecting a batch of cereals, with a budget as major constraint. The decision variables were the choice of the analytical method: instrumental method (e.g., liquid chromatography combined with mass‐spectrometry (LC‐MS/MS)), enzyme‐linked‐immuno‐assay (ELISA), or lateral flow devices (LFD), the number of incremental samples collected from the batch, and the number of aliquots analyzed. S&A plans using ELISA showed to be slightly more cost effective than S&A plans using the other two analytical methods. However, for DON in wheat, the difference between the optimal S&A plans using the three different analytical methods was minimal. For AFB₁ in maize, the cost effectiveness of the S&A plan using instrumental methods or ELISA were comparable whereas the S&A plan considering onsite detection with LFDs was least cost effective. In case of nonofficial controls, which do not have to follow official regulations for sampling and analysis, onsite detection with ELISA for both AFB₁ in maize and DON in wheat, or with LFDs for DON in wheat, could provide cost‐effective alternatives.     

An effective algorithm for obtaining the whole set of minimal cost pairs of disjoint paths with dual arc costs

In telecommunication networks design the problem of obtaining optimal (arc or node) disjoint paths, for increasing network reliability, is extremely important. The problem of calculating k _c disjoint paths from s to t (two distinct nodes), in a network with k _c different (arbitrary) costs on every arc such that the total cost of the paths is minimised, is NP-complete even for k _c =2. When k _c =2 these networks are usually designated as dual arc cost networks.     

Methods for Detecting and Estimating Population Threshold Concentrations for Air Pollution–Related Mortality with Exposure Measurement Error

The association between daily fluctuations in ambient particulate matter and daily variations in nonaccidental mortality have been extensively investigated. Although it is now widely recognized that such an association exists, the form of the concentration–response model is still in question. Linear, no threshold and linear threshold models have been most commonly examined. In this paper we considered methods to detect and estimate threshold concentrations using time series data of daily mortality rates and air pollution concentrations. Because exposure is measured with error, we also considered the influence of measurement error in distinguishing between these two completing model specifications. The methods were illustrated on a 15-year daily time series of nonaccidental mortality and particulate air pollution data in Toronto, Canada. Nonparametric smoothed representations of the association between mortality and air pollution were adequate to graphically distinguish between these two forms. Weighted nonlinear regression methods for relative risk models were adequate to give nearly unbiased estimates of threshold concentrations even under conditions of extreme exposure measurement error. The uncertainty in the threshold estimates increased with the degree of exposure error. Regression models incorporating threshold concentrations could be clearly distinguished from linear relative risk models in the presence of exposure measurement error. The assumption of a linear model given that a threshold model was the correct form usually resulted in overestimates in the number of averted premature deaths, except for low threshold concentrations and large measurement error.     

THE COST OF IGNORING LEAD TIME UNRELIABILITY IN INVENTORY THEORY*

A computerized cost-minimization model was used to study the importance of lead time unreliability (variability of lead time from mean lead time) in inventory management. Using different combinations of stockout cost, demand variability, mean lead time, and variability of lead time around the means, changes in optimum safety stock and in inventory costs were observed. Lead time unreliability was found to be of greater importance than either the mean lead time or the variability of demand in explaining inventory cost behavior. Managers and researchers involved in the development of inventory theory are urged to note the great financial damage that may result from ignoring lead time unreliability; a dollar measure of this penalty is included in the presentation.     

Optimal Procurement Design of an Assembly Supply Chain with Information Asymmetry

We study a decentralized assembly supply chain in which an assembler (she) assembles a set of n components, each produced by a different supplier (he), into a final product to satisfy an uncertain market demand. Each supplier holds private cost information to himself, for which the assembler only has a subjective estimate. Furthermore, the assembler believes that the suppliers' costs follow a joint discrete probability distribution. The assembler aims to design an optimal menu of contracts to maximize her own expected profit. The assembler's problem is a complex multi‐dimensional constrained optimization problem. We prove that there exists a unique optimal menu of contracts for the assembler, and we further develop an efficient algorithm with a complexity of O(n) to compute the optimal contract. In addition, we conduct a comprehensive sensitivity analysis to analyze how environmental parameters affect individual firm's performance and the value of information to the assembler, to each supplier, and to the supply chain. Our results suggest that each supplier's private cost information becomes more valuable to the assembler and each supplier when the average market demand increases or when the final product unit revenue increases. Surprisingly, when a supplier's cost volatility increases and its mean remains the same, the value of information to the assembler or to each supplier does not necessarily increase. Furthermore, we show that when the suppliers' cost distributions become more positively correlated, the suppliers are always worse off, but the assembler is better off. However, the value of information for the assembler might increase or decrease.     

The influence of aircraft size on airline operating costs

Many previous studies have shown that there are probably no economies of scale in the airline industry directly attributable to firm size. Scale effects within the firm, however, have often been suggested, particularly for example with regard to such firm-size independent factors as market density, route length, or aircraft size. The focus of this paper is the effect of aircraft size on an airline's unit cost. Though much of the previous evidence appears to be at variance with a priori expectations, the empirical results presented here suggest that most of the divergence is probably due to a conceptually inadequate basis of comparison. Appropriately compared, actual unit costs were generally found to decrease at a decreasing rate with aircraft size, though as the route length parameter is reduced some mild diseconomies appeared. Of further interest, the behavior with size of the underlying cost components was found to be quite diverse, the (far from uniform) decreases with size in unit crew, fuel, and maintenance costs being offset somewhat by increases in unit capital costs, insurance plus other costs, and landing fees.     

Reassessing the human health benefits from cleaner air

Recent proposals to further reduce permitted levels of air pollution emissions are supported by high projected values of resulting public health benefits. For example, the Environmental Protection Agency recently estimated that the 1990 Clean Air Act Amendment (CAAA) will produce human health benefits in 2020, from reduced mortality rates, valued at nearly $2 trillion per year, compared to compliance costs of $65 billion ($0.065 trillion). However, while compliance costs can be measured, health benefits are unproved: they depend on a series of uncertain assumptions. Among these are that additional life expectancy gained by a beneficiary (with median age of about 80 years) should be valued at about $80,000 per month; that there is a 100% probability that a positive, linear, no-threshold, causal relation exists between PM(2.5) concentration and mortality risk; and that progress in medicine and disease prevention will not greatly diminish this relationship. We present an alternative uncertainty analysis that assigns a positive probability of error to each assumption. This discrete uncertainty analysis suggests (with probability >90% under plausible alternative assumptions) that the costs of CAAA exceed its benefits. Thus, instead of suggesting to policymakers that CAAA benefits are almost certainly far larger than its costs, we believe that accuracy requires acknowledging that the costs purchase a relatively uncertain, possibly much smaller, benefit. The difference between these contrasting conclusions is driven by different approaches to uncertainty analysis, that is, excluding or including discrete uncertainties about the main assumptions required for nonzero health benefits to exist at all.     

Cost accounting in manufacturing: dawn of a new era

Abstract

Advances in the technology of manufacturing planning, control and operation have made conventional cost accounting practices not only obsolete but dangerous. As a portion of total factory cost, direct labour costs have declined dramatically due to improved quality materials, fewer interruptions, automation and robotics. Overhead costs, conversely, have increased greatly and the fixed components now predominate. Charts of accounts contain many trivial items and lack those now considered very important. This article presents the needed revisions.     

电子商务环境下合作采购效益分析

合作采购是一种重要的企业间电子商务应用模式,成功实施合作采购需要供应链成员的积极参与。本文针对供应商采取的两种批发价定价策略,比较分析了协调成本对买主间合作采购动力及其总体采购成本的影响。其结果表明,只要协调成本较小,买主便具有合作采购动力,且无论供应商采取固定价格策略还是采取数量折扣策略,都存在一个协调成本临界值,当协调成本小于该临界值时,合作采购将同时减少买主与供应商的总体成本;当协调成本大于该临界值时,则总有一方的总体成本在合作采购中增加。     

Analysis and Management of Periodic Review,Order‐Up‐To Level Inventory Systems with Order Crossover

In this article, we investigate the (R, S) periodic review, order‐up‐to level inventory control system with stochastic demand and variable leadtimes. Variable leadtimes can lead to order crossover, in which some orders arrive out of sequence. Most theoretical studies of order‐up‐to inventory systems under variable leadtimes assume that crossovers do not occur and, in so doing, overestimate the standard deviation of the realized leadtime distribution and prescribe policies that can inflate inventory costs. We develop a new analytic model of the expected costs associated with this system, making use of a novel approximation of the realized (reduced) leadtime standard deviation resulting from order crossovers. Extensive experimentation through simulation shows that our model closely approximates the true expected cost and can be used to find values of R and S that provide an expected cost close to the minimum cost. Taking account of, as opposed to ignoring, crossovers leads, on average, to substantial improvements in accuracy and significant cost reductions. Our results are particularly useful for managers seeking to reduce inventory costs in supply chains with variable leadtimes.     

作业成本动因选择、合并与评价的系统方法构建

目前学术界关于作业成本动因选择与合并的研究,缺乏对动因留选与留选个数的探讨,而关于对成本动因选择合并的评价的研究未见。可以通过聚类分析建立模型,得到成本动因的相关类,再结合主成分分析指导留选动因的个数,最终确定留选动因,并首次建立评价动因选择与合并优劣性的主成分分析模型。实证分析表明,此系统方法更好地解决了成本动因选择与合并的问题,相同数据下该方法比矩阵理论与距离聚类分析结果更优,作业成本管理系统的复杂性与信息成本显著降低。本文为作业成本动因的选择与合并以及评价提供了一套系统方法。     

Cost sharing and strategyproof mechanisms for set cover games

We develop for set cover games several general cost-sharing methods that are approximately budget-balanced, in the core, and/or group-strategyproof. We first study the cost sharing for a single set cover game, which does not have a budget-balanced mechanism in the core. We show that there is no cost allocation method that can always recover more than $\frac{1}{\ln n}$ of the total cost and in the core. Here n is the number of all players to be served. We give a cost allocation method that always recovers $\frac{1}{\ln d_{\mathit{max}}}$ of the total cost, where d _max is the maximum size of all sets. We then study the cost allocation scheme for all induced subgames. It is known that no cost sharing scheme can always recover more than $\frac{1}{n}$ of the total cost for every subset of players. We give an efficient cost sharing scheme that always recovers at least $\frac{1}{2n}$ of the total cost for every subset of players and furthermore, our scheme is cross-monotone. When the elements to be covered are selfish agents with privately known valuations, we present a strategyproof charging mechanism, under the assumption that all sets are simple sets; further, the total cost of the set cover is no more than ln?d _max times that of an optimal solution. When the sets are selfish agents with privately known costs, we present a strategyproof payment mechanism to them. We also show how to fairly share the payments to all sets among the elements.     

Order Progress Information: Improved Dynamic Emergency Ordering Policies

Technologies such as radio‐frequency identification and global positioning systems can provide improved real‐time tracking information for products and replenishment orders along the supply chain. We call this type of visibility order progress information. In this paper, we investigate how order progress information can be used to improve inventory replenishment decisions. To this end, we examine a retailer facing a stochastic lead time for order fulfillment. We characterize a replenishment policy that is based on the classical (Q, R) policy and that allows for releasing emergency orders in response to the order progress information. We show that the optimal structure of this policy is given by a sequence of threshold values dependent on order progress information. In a numerical study we evaluate the cost savings due to this improved replenishment policy.