Causality Assessment of the Acute Health Complaints Reported in Association with Oxygenated Fuels

In some areas where oxygenated fuel programs have been implemented, there have been widespread complaints of non-specific health effects attributed to the gasoline. There are a number of hypotheses that can account for this apparent association. This paper examines the hypothesis that the use of oxy-fuel (either oxygenated gasoline or reformulated gasoline) results in exposure of the general population to one or more chemicals at concentrations that cause toxicologic injury. Although several oxygenates can be used in oxy-fuels, this analysis focuses on MTBE because it is the most widely used oxygenate and because the database of relevant toxicologic data is greatest for this oxygenate. The causal assessment is based on an evaluation of the qualitative and quantitative plausibility that oxygenated fuel-related exposures have toxicological effects, and the epidemiologic studies that directly test the hypothesis that the use of oxygenated fuels causes adverse health effects. The plausibility that chemical exposures related to oxy-fuel use cause toxicological effects is very low. This determination is based on consideration of the exposure-response and time-action profiles for relevant toxicological effects of MTBE in animals, experimental MTBE exposure studies in humans, and the possibility that the addition of MTBE to gasoline results in toxicologically significant qualitative and/or quantitative changes in gasoline-related exposures. Similarly, the epidemiologic studies of oxy-fuel exposed cohorts do not support a causal relationship between oxy-fuel use and adverse health effects. Although the data are insufficient to rule the possibility of unique sensitivity in a small segment of the population, the strength of the evidence and the availability of other more plausible explanations for the health complaints reported in association with oxy-fuels support a high degree of confidence in the conclusion that MTBE-containing oxygenated fuels are not the cause of acute toxicity in the general population.     

Statistical Properties of Microstructure Noise

We study the estimation of (joint) moments of microstructure noise based on high frequency data. The estimation is conducted under a nonparametric setting, which allows the underlying price process to have jumps, the observation times to be irregularly spaced, and the noise to be dependent on the price process and to have diurnal features. Estimators of arbitrary orders of (joint) moments are provided, for which we establish consistency as well as central limit theorems. In particular, we provide estimators of autocovariances and autocorrelations of the noise. Simulation studies demonstrate excellent performance of our estimators in the presence of jumps, irregular observation times, and even rounding. Empirical studies reveal (moderate) positive autocorrelations of microstructure noise for the stocks tested.     

Improving Causal Inferences in Risk Analysis

Recent headlines and scientific articles projecting significant human health benefits from changes in exposures too often depend on unvalidated subjective expert judgments and modeling assumptions, especially about the causal interpretation of statistical associations. Some of these assessments are demonstrably biased toward false positives and inflated effects estimates. More objective, data‐driven methods of causal analysis are available to risk analysts. These can help to reduce bias and increase the credibility and realism of health effects risk assessments and causal claims. For example, quasi‐experimental designs and analysis allow alternative (noncausal) explanations for associations to be tested, and refuted if appropriate. Panel data studies examine empirical relations between changes in hypothesized causes and effects. Intervention and change‐point analyses identify effects (e.g., significant changes in health effects time series) and estimate their sizes. Granger causality tests, conditional independence tests, and counterfactual causality models test whether a hypothesized cause helps to predict its presumed effects, and quantify exposure‐specific contributions to response rates in differently exposed groups, even in the presence of confounders. Causal graph models let causal mechanistic hypotheses be tested and refined using biomarker data. These methods can potentially revolutionize the study of exposure‐induced health effects, helping to overcome pervasive false‐positive biases and move the health risk assessment scientific community toward more accurate assessments of the impacts of exposures and interventions on public health.     

Climate Change and Human Health: Estimating Avoidable Deaths and Disease

Human population health has always been central in the justification for sustainable development but nearly invisible in the United Nations Framework Convention on Climate Change negotiations. Current scientific evidence indicates that climate change will contribute to the global burden of disease through increases in diarrhoeal disease, vector-borne disease, and malnutrition, and the health impacts of extreme weather and climate events. A few studies have estimated future potential health impacts of climate change but often generate little policy-relevant information. Robust estimates of future health impacts rely on robust projections of future disease patterns. The application of a standardized and established methodology has been developed to quantify the impact of climate change in relation to different greenhouse gas emission scenarios. All health risk assessments are necessarily biased toward conservative best-estimates of health effects that are easily measured. Global, regional, and national risk assessments can take no account of irreversibility, or plausible low-probability events with potentially very high burdens on human health. There is no "safe limit" of climate change with respect to health impacts as health systems in some regions do not adequately cope with the current climate variability. Current scientific methods cannot identify global threshold health effects in order for policymakers to regulate a "tolerable" amount of climate change. We argue for the need for more research to reduce the potential impacts of climate change on human health, including the development of improved methods for quantitative risk assessment. The large uncertainty about the future effects of climate change on human population health should be a reason to reduce greenhouse gas emissions, and not a reason for inaction.     

Noise effects on two industrial tasks

Very little is known about the effects of noise on the quality and quantity of motor task performance particularly in natural work settings. The present paper describes a study of the effects of noise on the performance of two tasks: the assembly of car carburettors and car air conditioners. The tasks were carried out either under quiet conditions (65 dBA) or noisy conditions (75 or 90 dBA): four broadly comparable groups of workers were studied. The data suggested, among other things, that all faulty behaviours involving a mental load were affected by noise although manual dexterity was not. It also appeared that noise impaired activities involving visuo-motor coordination. These findings, and others, are discussed in terms of information processing.     

Quantifying Cancer Risk from Radiation

Complex statistical models fitted to data from studies of atomic bomb survivors are used to estimate the human health effects of ionizing radiation exposures. We describe and illustrate an approach to estimate population risks from ionizing radiation exposure that relaxes many assumptions about radiation‐related mortality. The approach draws on developments in methods for causal inference. The results offer a different way to quantify radiation's effects and show that conventional estimates of the population burden of excess cancer at high radiation doses are driven strongly by projecting outside the range of current data. Summary results obtained using the proposed approach are similar in magnitude to those obtained using conventional methods, although estimates of radiation‐related excess cancers differ for many age, sex, and dose groups. At low doses relevant to typical exposures, the strength of evidence in data is surprisingly weak. Statements regarding human health effects at low doses rely strongly on the use of modeling assumptions.     

Effects of vacation from work on health and well-being: Lots of fun,quickly gone

Abstract

Although vacation from work provides a valuable opportunity for recovery, few studies have met the requirements for assessing its effects. These include taking measurements well ahead of the vacation, during the vacation and at several points in time afterwards. Our study on vacation (after-) effects focused on two related questions: (1) Do health and well-being of working individuals improve during a vacation? and (2) How long does a vacation effect last after resumption of work? In a longitudinal study covering seven weeks, 96 Dutch workers reported their health and well-being levels two weeks before a winter sports vacation, during vacation and one week, two weeks and four weeks after vacation on seven indicators. Participants' health and well-being improved during vacation on five indicators: health status, mood, tension, energy level and satisfaction. However, during the first week of work resumption, health and well-being had generally returned to pre-vacation levels. In conclusion, a winter sports vacation is associated with improvements in self-reported health and well-being among working individuals. However, these effects fade out rapidly after work resumption. We propose a framework for future vacation research and suggest investigating the role of vacation type, duration and means to prolong vacation relief.     

Perception of Risks From Electromagnetic Fields: A Psychometric Evaluation of a Risk-Communication Approach

Potential health risks from exposure to power-frequency electromagnetic fields (EMF) have become an issue of significant public concern. This study evaluates a brochure designed to communicate EMF health risks from a scientific perspective. The study utilized a pretest-posttest design in which respondents judged various sources of EMF (and other) health and safety risks, both before reading the brochure and after. Respondents assessed risks on dimensions similar to those utilized in previous studies of risk perception. In addition, detailed ratings were made that probed respondents' beliefs about the possible causal effects of EMF exposure. The findings suggest that naive beliefs about the potential of EMF exposure to cause harm were highly influenced by specific content elements of the brochure. The implications for using risk-communication approaches based on communicating scientific uncertainty are discussed.     

Assessment of Inhalation Exposures and Potential Health Risks to the General Population that Resulted from the Collapse of the World Trade Center Towers

In the days following the collapse of the World Trade Center (WTC) towers on September 11, 2001 (9/11), the U.S. Environmental Protection Agency (EPA) initiated numerous air monitoring activities to better understand the ongoing impact of emissions from that disaster. Using these data, EPA conducted an inhalation exposure and human health risk assessment to the general population. This assessment does not address exposures and potential impacts that could have occurred to rescue workers, firefighters, and other site workers, nor does it address exposures that could have occurred in the indoor environment. Contaminants evaluated include particulate matter (PM), metals, polychlorinated biphenyls, dioxins, asbestos, volatile organic compounds, particle-bound polycyclic aromatic hydrocarbons, silica, and synthetic vitreous fibers (SVFs). This evaluation yielded three principal findings. (1) Persons exposed to extremely high levels of ambient PM and its components, SVFs, and other contaminants during the collapse of the WTC towers, and for several hours afterward, were likely to be at risk for acute and potentially chronic respiratory effects. (2) Available data suggest that contaminant concentrations within and near ground zero (GZ) remained significantly elevated above background levels for a few days after 9/11. Because only limited data on these critical few days were available, exposures and potential health impacts could not be evaluated with certainty for this time period. (3) Except for inhalation exposures that may have occurred on 9/11 and a few days afterward, the ambient air concentration data suggest that persons in the general population were unlikely to suffer short-term or long-term adverse health effects caused by inhalation exposures. While this analysis by EPA evaluated the potential for health impacts based on measured air concentrations, epidemiological studies conducted by organizations other than EPA have attempted to identify actual impacts. Such studies have identified respiratory effects in worker and general populations, and developmental effects in newborns whose mothers were near GZ on 9/11 or shortly thereafter. While researchers are not able to identify specific times and even exactly which contaminants are the cause of these effects, they have nonetheless concluded that exposure to WTC contaminants (and/or maternal stress, in the case of developmental effects) resulted in these effects, and have identified the time period including 9/11 itself and the days and few weeks afterward as a period of most concern based on high concentrations of key pollutants in the air and dust.     

Exposure-Response Functions for Health Effects of Air Pollutants Based on Epidemiological Findings

Quantitative knowledge about health damage due to air pollution is an important element in analyses of cost-effective abatement strategies, and is also essential for setting Air Quality Standards. Epidemiological studies, in spite of the numerous problems connected to them, provide a reasonable basis for exposure-response functions in this context. On the basis of a literature review, exposure-response functions that relate ambient air pollutant concentrations to the frequency of various health effects are recommended in this paper. The following end-points were examined: Acute and chronic respiratory symptoms in children and adults, crude mortality, and lung cancer incidence. The effects are attributed to one indicator component, which in most cases is particles. A calculation procedure is suggested which makes it possible to estimate excess annual symptom-days for short-term effects using the annual average concentration.     

How the psychosocial work environment of motor vehicle mechanics may influence coping with musculoskeletal symptoms

A number of studies have shown that musculoskeletal symptoms are related to the physical and psychosocial work environments. Workers with musculoskeletal symptoms are often advised to cope by such measures as changing working technique, using lifting equipment and discussing health and environmental problems with supervisors and colleagues. Intervention studies at the individual level, however, have shown that such advice has limited effects in reducing the prevalence of musculoskeletal symptoms. The hypothesis for this study was that negative social and organizational factors may prevent workers from implementing such coping strategies. All 103 motor vehicle mechanics surveyed in 12 different garages responded to a questionnaire on coping with musculoskeletal symptoms and the psychosocial work environment. Positive and significant relationships were shown between how mechanics coped with their musculoskeletal symptoms and such psychosocial factors as work demands, social support, control, manager's involvement in health and safety work, and whether the garages had regular meetings between management and workers. Achieving positive results from preventive work through back schools and other ergonomic interventions seems to require that an organization with positive attitudes towards health and safety work be created before such interventions are implemented.     

Voting Technology,Political Responsiveness,and Infant Health: Evidence From Brazil

This paper studies the introduction of electronic voting technology in Brazilian elections. Estimates exploiting a regression discontinuity design indicate that electronic voting reduced residual (error‐ridden and uncounted) votes and promoted a large de facto enfranchisement of mainly less educated citizens. Estimates exploiting the unique pattern of the technology's phase‐in across states over time suggest that, as predicted by political economy models, it shifted government spending toward health care, which is particularly beneficial to the poor. Positive effects on both the utilization of health services (prenatal visits) and newborn health (low‐weight births) are also found for less educated mothers, but not for the more educated.     

Air Pollution and Human Health: Perspectives for the '90s and Beyond

This paper considers the health effects of air pollution from three perspectives: historical, statistical, and public policy, and also as depicted by the recent epidemiology, primarily mortality studies. The historical perspectives establish the reality of population-based health effects, and they provide data with which to evaluate more recent evidence. Statistical perspectives imply that, while there is strong evidence that associations between air quality and health persist, many details of these relationships remain obscure, especially as to the existence of concentration thresholds that might define safe exposure levels. Additional major questions include the effects of uncertainties in actual pollution exposures, the degree of prematurity of "excess" deaths, and whether the development of new cases of chronic disease is associated with air pollution. Public policy issues center around interpreting the new epidemiological studies in the light of these uncertainties and the analysis and management of the concomitant health risks.     

Technical Uncertainty in Quantitative Policy Analysis — A Sulfur Air Pollution Example

Expert judgments expressed as subjective probability distributions provide an appropriate means of incorporating technical uncertainty in some quantitative policy studies. Judgments and distributions obtained from several experts allow one to explore the extent to which the conclusions reached in such a study depend on which expert one talks to. For the case of sulfur air pollution from coal-fired power plants, estimates of sulfur mass balance as a function of plume flight time are shown to vary little across the range of opinions of leading atmospheric scientists while estimates of possible health impacts are shown to vary widely across the range of opinions of leading scientists in air pollution health effects.     

Development of a Preliminary Framework for Informing the Risk Analysis and Risk Management of Nanoparticles

Decisions are often made even when there is uncertainty about the possible outcomes. However, methods for making decisions with uncertainty in the problem framework are scarce. Presently, safety assessment for a product containing engineered nano-scale particles is a very poorly structured problem. Many fields of study may inform the safety assessment of such particles (e.g., ultrafines, aerosols, debris from medical devices), but engineered nano-scale particles may present such unique properties that extrapolating from other types of studies may introduce, and not resolve, uncertainty. Some screening-level health effects studies conducted specifically on engineered nano-scale materials have been published and many more are underway. However, it is clear that the extent of research needed to fully and confidently understand the potential for health or environmental risk from engineered nano-scale particles may take years or even decades to complete. In spite of the great uncertainty, there is existing research and experience among researchers that can help to provide a taxonomy of particle properties, perhaps indicating a relative likelihood of risk, in order to prioritize nanoparticle risk research. To help structure this problem, a framework was developed from expert interviews of nanotechnology researchers. The analysis organizes the information as a system based on the risk assessment framework, in order to support the decision about safety. In the long term, this framework is designed to incorporate research results as they are generated, and therefore serve as a tool for estimating the potential for human health and environmental risk.     

相对业绩与投资组合思想在期权激励契约设计中的应用

传统股票期权激励契约以股票价格来度量经理人的业绩,但股票价格实际上受到经理人不可控因素(系统风险)的影响,从而导致用股票价格来衡量经理人业绩时会出现反向激励现象,错误惩罚有能力的经理人或慷慨奖励无能的经理人。针对传统股票期权激励契约的缺陷,一些学者把期权激励契约的执行价格和一些指数相联系起来,消除了部分市场水平噪音对期权激励契约的影响。但这种绝对指数股票期权也没有改变指数期权激励契约的结构性缺陷,即不能完全消除市场和行业噪音对期权激励契约的影响。因此,本文借鉴相对业绩和投资组合思想,重新对股票期权的执行价格进行设计,即改变期权到期时权益结构或把执行价格设计成基准绩效投资组合形式,从而达到完全消除市场和行业噪音对期权激励契约的影响,提高期权报酬契约的绩效。     

The effects of fitness training on the physiological stress response

The favourable psychological and physiological profile found in fit sportsmen does not necessarily follow from their exercise behaviour. Alternatively it may depend on endowment and/or self-selection. In that case, participation in regular exercise may not always result in a reduction of susceptibility to stress. The present article reviews several well-controlled laboratory studies that have directly examined the effect of fitness training programmes on the physiological responses to a set of standardized stressors. It was generally expected that fitness training would enhance psychological stress resistance and thus mitigate the physiological response to stress. The results of most studies belie these expectations. Intensive training programmes of up to 8 months do not change stress reactivity, even if initially low fit and high stress-reactive subjects are used. The failure to find a training effect on the intensity of the stress reactions in laboratory studies does not rule out possible psychosocial effects of regular exercise on the frequency and duration of the stress reactions in real-life situations. Furthermore, although the dynamics of the physiological response to stress are not changed, there is a clear downward shift in the overall level of heart rate and blood pressure in stressful situations. Several possible mechanisms are suggested by which these training effects may help us to deal with work stress without suffering health problems.     

A Review of Organizational Stress Management Research:

Evaluation studies of worksite stress management training (SMT) are reviewed and methodological considerations are offered regarding (1) program orientation, (2) experimental design, (3) worker participants, (4) outcome measures, and (5) duration of training effects and worker compliance. Suggestions for additional research include the need to (1) employ additional comparison groups in order to detect training-specific effects, (2) evaluate SMT in blue-collar settings, (3) expand the scope of outcome measures to include employee behaviors, and (4) assess long term effects of SMT and factors associated with worker maintenance of learned skills. It is concluded that SMT has value as a prevention activity in work settings but its use as a treatment strategy for troubled workers is not supported conceptually or empirically. Companies and practitioners are encouraged to view SMT not as an isolated activity but as one component of occupational health and safety activities. A holistic approach which incorporates stress management into company health and safety philosophies is viewed as the optimal strategy.     

Projection of Health Benefits from Ambient Ozone Reduction Related to the Use of Methyl tertiary Butyl Ether (MTBE) in the Reformulated Gasoline Program

To estimate potential public health benefits from ozone (O₃) pollution reduction attributable to the use of methyl tertiary-butyl ether (MTBE) in gasoline, O₃ dose-response estimates from the biomedical literature were combined with model estimates of O₃ reduction. Modeling employed EPA MOBILE5a and Complex models to predict emission changes, industry AQIRP techniques to predict ambient O₃ changes, and the National Exposure Model to predict human exposures. Human health effects considered were lung function decrements and respiratory irritant symptoms (using dose-response functions measured in laboratory and field studies), and increased death rates (using concentration-response functions inferred statistically from public-health data). Other reported health effects, such as lung inflammation, increases in asthma attacks, and hospitalizations, were not addressed because of inadequate dose-response information. Even for the health responses considered, quantitation of improvements due to MTBE use is problematical, because MTBE affects only a small percentage of existing O₃ pollution, and because exposure-response relationships are not well understood for population subgroups most likely to be affected. Nevertheless, it is reasonable to conclude that even small MTBE-associated reductions in peak ambient O₃ levels (1–5 ppb, according to model estimates) should yield considerable public health benefits. Tens of millions of Americans are potentially exposed to O₃ in the concentration range associated with health effects. Even if only a small percentage of them are susceptible, any incremental reduction in O₃ (as with MTBE use) must mitigate or prevent effects for a meaningful number of people. Better quantitative estimates of benefit must await a more detailed understanding of each link in the chain of causation.     

Editorial: Cognitive science,occupational stress and organizational health

A number of studies have shown that musculoskeletal symptoms are related to the physical and psychosocial work environments. Workers with musculoskeletal symptoms are often advised to cope by such measures as changing working technique, using lifting equipment and discussing health and environmental problems with supervisors and colleagues. Intervention studies at the individual level, however, have shown that such advice has limited effects in reducing the prevalence of musculoskeletal symptoms. The hypothesis for this study was that negative social and organizational factors may prevent workers from implementing such coping strategies. All 103 motor vehicle mechanics surveyed in 12 different garages responded to a questionnaire on coping with musculoskeletal symptoms and the psychosocial work environment. Positive and significant relationships were shown between how mechanics coped with their musculoskeletal symptoms and such psychosocial factors as work demands, social support, control, manager's involvement in health and safety work, and whether the garages had regular meetings between management and workers. Achieving positive results from preventive work through back schools and other ergonomic interventions seems to require that an organization with positive attitudes towards health and safety work be created before such interventions are implemented.