Intuitive Toxicology: Expert and Lay Judgments of Chemical Risks

Human beings have always been intuitive toxicologists, relying on their senses of sight, taste, and smell to detect harmful or unsafe food, water, and air. As we have come to recognize that our senses are not adequate to assess the dangers inherent in exposure to a chemical substance, we have created the sciences of toxicology and risk assessment to perform this function. Yet despite this great effort to overcome the limitations of intuitive toxicology, it has become evident that even our best scientific methods still depend heavily on extrapolations and judgments in order to infer human health risks from animal data. Many observers have acknowledged the inherent subjectivity in the assessment of chemical risks and have indicated a need to examine the subjective or intuitive elements of expert and lay risk judgments. We have begun such an examination by surveying members of the Society of Toxicology and the lay public about basic toxicological concepts, assumptions, and interpretations. Our results demonstrate large differences between toxicologists and laypeople, as well as differences between toxicologists working in industry, academia, and government. In addition, we find that toxicologists are sharply divided in their opinions about the ability to predict a chemical's effect on human health on the basis of animal studies. We argue that these results place the problems of risk communication in a new light. Although the survey identifies misconceptions that experts should clarify for the public, it also suggests that controversies over chemical risks may be fueled as much by limitations of the science of risk assessment and disagreements among experts as by public misconceptions.     

Russki adventures

This case study, by Paul Beamish, was a prize-winner in the EFMD 1992 Annual Case Writing Competition, in the section entitled, ‘Entrepreneurship’. It concerns a daring new business venture in the Russian Caucasus Mountains.In mid-1991, Guy Crevasse and Andrei Kakov, the two major partners in Russki Adventures contemplated their next move. They had spent the last year and a half exploring the possibility of starting a helipcopter skiing operation in Russia.Their plan was to bring clients from Europe, North America, and Japan to the Caucasus Mountains to ski the vast areas of secluded mountain terrain made accessible by the use of helicopters and the recent business opportunities offered by ‘glasnost’.Three options for proceeding were being considered. The first was to proceed with the venture on their own, in the Caucasus Mountains area that had been made available to them by a Soviet government agency. The second was to accept the offer of partnership with Extreme Dreams, a French tour operator that had begun operations in the Caucasus region during the 1991 season. The final option was to wait, save their money and not proceed with the venture at this time.The data presented in the case includes information on: the company founders the helicopter skiing industry the Russian environment proposed market positioning of the business the potential alliance partners forecast financial analysis, under several scenarios.     

Exposure Reconstruction for the TCDD-Exposed NIOSH Cohort Using a Concentration- and Age-Dependent Model of Elimination

Recent studies demonstrating a concentration dependence of elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) suggest that previous estimates of exposure for occupationally exposed cohorts may have underestimated actual exposure, resulting in a potential overestimate of the carcinogenic potency of TCDD in humans based on the mortality data for these cohorts. Using a database on U.S. chemical manufacturing workers potentially exposed to TCDD compiled by the National Institute for Occupational Safety and Health (NIOSH), we evaluated the impact of using a concentration- and age-dependent elimination model (CADM) (Aylward et al., 2005) on estimates of serum lipid area under the curve (AUC) for the NIOSH cohort. These data were used previously by Steenland et al. (2001) in combination with a first-order elimination model with an 8.7-year half-life to estimate cumulative serum lipid concentration (equivalent to AUC) for these workers for use in cancer dose-response assessment. Serum lipid TCDD measurements taken in 1988 for a subset of the cohort were combined with the NIOSH job exposure matrix and work histories to estimate dose rates per unit of exposure score. We evaluated the effect of choices in regression model (regression on untransformed vs. ln-transformed data and inclusion of a nonzero regression intercept) as well as the impact of choices of elimination models and parameters on estimated AUCs for the cohort. Central estimates for dose rate parameters derived from the serum-sampled subcohort were applied with the elimination models to time-specific exposure scores for the entire cohort to generate AUC estimates for all cohort members. Use of the CADM resulted in improved model fits to the serum sampling data compared to the first-order models. Dose rates varied by a factor of 50 among different combinations of elimination model, parameter sets, and regression models. Use of a CADM results in increases of up to five-fold in AUC estimates for the more highly exposed members of the cohort compared to estimates obtained using the first-order model with 8.7-year half-life. This degree of variation in the AUC estimates for this cohort would affect substantially the cancer potency estimates derived from the mortality data from this cohort. Such variability and uncertainty in the reconstructed serum lipid AUC estimates for this cohort, depending on elimination model, parameter set, and regression model, have not been described previously and are critical components in evaluating the dose-response data from the occupationally exposed populations.     

Pathways between education and health: a causal modelling approach

Summary.  The association of poor education and poor health has been consistently observed in many studies and in various countries. Thus far, studies examining the mechanisms underlying this association have looked at only a limited set of potential pathways. This study simultaneously examines six distinctive pathways, which have been hypothesized to link education and health and found support from previous studies. A causal analysis of education and health was performed using structural equation models. Data were used from six phases of the National Child Development Study, which is based on following up an initial sample of 17416 children who were born in 1958. The association between education and health appears to be explained by a combination of mechanisms: adolescent health and adult health behaviours for men and women, adult social class among men and parental social class among women. We conclude that improvements in population educational attainment may not automatically lead to improvements in population health, and that health policies for improving health and reducing health inequalities need to target specific causal pathways.     

Evaluation: Stakeholder-focused Criteria

Identifying and selecting suitable criteria is an important consideration in evaluating the performance of public sector organizations. Which criteria are chosen, and how they are weighted, will depend largely on the perspective being taken; different stakeholders (for example, clients, providers or commissioners) are likely to emphasize different criteria. In this paper a number of criteria are identified and an argument is developed to indicate which criteria are likely to be valued by various stakeholders. Furthermore, a number of approaches and mechanisms for evaluation are identified and the links between these, the criteria appropriate to them and the various stakeholders are made explicit. Finally, the issue of politics and the distribution of power between the stakeholders is addressed with a call for greater explicitness in using and balancing criteria (for example, as between professionals and the intended beneficiaries of services). In this way, while recognizing the inherent political nature of performance evaluation, the planning and implementation of services may be improved by a more mutually informed approach to evaluation.     

The prevalence rates of pathological gambling: A look at methods

Planning the gambling environment requires protection of the public's health, safety and welfare. Whereas most public gaming provisions and statutes address the public's fears of organized crime as well as some welfare needs, rarely do they safeguard the public's health regarding the spread of the mental disease known as pathological gambling. Measurement of the prevalence and incidence of this disease would enable policy planners to evaluate both the state's responsibility for an epidemic and the adequacy of publicly funded treatment programs. The purpose of this paper is to examine the methods which underlie three different estimates of the prevalence rate of pathological gambling and to critique them in the light of sound epidemiological procedure. In 1975, the Institute for Social Research (ISR) of the University of Michigan conducted a national survey and a survey of the state of Nevada on behalf of the U.S. Commission on a National Policy Toward Gambling. Using discriminant function analysis coupled with subjective inspection of cases in the at-risk pool, the researchers estimated rates of probable and potential pathological gamblers. In 1984 and 1985, this author surveyed residents in the Delaware Valley and the state of Ohio using the cumulative clinical signs method which also posited rates of probable and potential pathological gamblers. In 1986, researchers at the Office of Mental Health for the State of New York employed a formal screening device to survey residents and proposed a rate of probable pathological gamblers and a rate of problem — although not pathological — gamblers. All three approaches produced different estimates. The utility of prevalence and incidence rate research in this field is threatened by a lack of consensus about the proper epidemiological procedure to be employed in arriving at these estimates. There is also confusion about the distinction between a probable and a potential pathological gambler. The planning purpose, method, validity and reliability of prevalence rate research about pathological gambling are addressed in this paper.     

Principal curves revisited

A principal curve (Hastie and Stuetzle, 1989) is a smooth curve passing through the middle of a distribution or data cloud, and is a generalization of linear principal components. We give an alternative definition of a principal curve, based on a mixture model. Estimation is carried out through an EM algorithm. Some comparisons are made to the Hastie-Stuetzle definition.     

Book reviews

Nathan Glazer Ethnic Dilemmas Harvard, Harvard University Press. 1985

Giddens, Anthony The Constitution of Society, Berkeley, University of California, 1985, pp.XXXVII, 402. Notes, glossary, diagrams, bibliographic notes and index.

Jeremy Rifkin Declaration of a Heretic. Boston. London, Melbourne and Henley, Routledge and Kegan Paul, 1985, pp.X,140.

Ted Benton The Rise and Fall of Structural Marxism: Althusser and his Influence, New York, St.Martin's Press, 1984, pp. VII,259.

Raymond L. Garthoff Détente and Confrontation Washington, The Brookings Institution, 1985, pp.XVI,1126.

Joseph J. Collins The Soviet Invasion of Afghanistan. A Study in the Use of Force in Soviet Foreign Policy, Massachusetts/Toronto, D.C. Heath and Company/Lexington, 1986, pp. XV, 195.

Jan Shipps Mormonism: The Story of a New Religious Tradition, Chicago, University of Illinois Press, 1985, pp.211.

Robert Jay Lifton Home from the War: Vietnam Veterans: Neither Victims nor Executioners, New York, Basic Books, 1985, pp.478     

Estimating the National High School Dropout Rate

Recent interest has focused on the high school dropout rate as one indicator of the national education picture. Empirical estimates of this "rate" vary considerably, because these estimates are poorly defined. This article reviews some of the current measures and presents a new measure of the high school dropout rate--the proportion of high school students who drop out in a defined period of time (1 year). The estimates show that the national yearly high school dropout rate was about the same in 1985 as it was in 1968. Improvement has occurred, however, since 1968 for specific racial groups as well as for some grade levels.