Use of Markov Chain Monte Carlo Analysis with a Physiologically-Based Pharmacokinetic Model of Methylmercury to Estimate Exposures in U.S. Women of Childbearing Age

A Bayesian approach, implemented using Markov Chain Monte Carlo (MCMC) analysis, was applied with a physiologically‐based pharmacokinetic (PBPK) model of methylmercury (MeHg) to evaluate the variability of MeHg exposure in women of childbearing age in the U.S. population. The analysis made use of the newly available National Health and Nutrition Survey (NHANES) blood and hair mercury concentration data for women of age 16–49 years (sample size, 1,582). Bayesian analysis was performed to estimate the population variability in MeHg exposure (daily ingestion rate) implied by the variation in blood and hair concentrations of mercury in the NHANES database. The measured variability in the NHANES blood and hair data represents the result of a process that includes interindividual variation in exposure to MeHg and interindividual variation in the pharmacokinetics (distribution, clearance) of MeHg. The PBPK model includes a number of pharmacokinetic parameters (e.g., tissue volumes, partition coefficients, rate constants for metabolism and elimination) that can vary from individual to individual within the subpopulation of interest. Using MCMC analysis, it was possible to combine prior distributions of the PBPK model parameters with the NHANES blood and hair data, as well as with kinetic data from controlled human exposures to MeHg, to derive posterior distributions that refine the estimates of both the population exposure distribution and the pharmacokinetic parameters. In general, based on the populations surveyed by NHANES, the results of the MCMC analysis indicate that a small fraction, less than 1%, of the U.S. population of women of childbearing age may have mercury exposures greater than the EPA RfD for MeHg of 0.1 μg/kgg/day, and that there are few, if any, exposures greater than the ATSDR MRL of 0.3 μgg/kgg/day. The analysis also indicates that typical exposures may be greater than previously estimated from food consumption surveys, but that the variability in exposure within the population of U.S. women of childbearing age may be less than previously assumed.     

Social responsibility goal perception

The intent of this study is to distinguish areas of difference in the perception of organizational goals among managers, hourly workers, and graduate business students. The managers were chosen to represent the present point of view of management, while the hourly workers were selected to be indicative of labor's viewpoint toward the goal selection of organizations. Students were chosen because they represent the potential transfusion into management. The tool used to solicit these responses was a questionnaire composed of twenty questions, with each question divided into two parts. The first part examined the way the individual perceived the achievement level of the organization (‘is’), and the other half represented the level that the individual aspired for the organization to achieve in the future (‘should be’). These two parts were quantified using a Likert scale ranging from 1 (of no importance) to 5 (of extremely high importance). The results indicate the similarities and differences between each of these three groups in terms of present perceptions and future expectations of these goals.     

An evaluation of physical fitness parameters for graduate students

Although graduate physical therapy students are taught the principles of fitness for incorporation into their professional lives, they have difficulty finding the time to implement these principles during graduate school. The authors studied 3 successive classes of graduate physical therapy students at the beginning and ending of their respective programs. They found that the women's percentages of body fat were significantly greater over the period of the study. The men's lower extremity strength decreased at the slower speeds (60 degrees/second), and the women showed increased strength at the higher speeds (180 and 240 degrees/second, respectively). Male grip strength significantly increased over the period of the study. To decrease students' percentages of body fat and increase their strength, the authors asserted that physical therapy students should be allowed more time to participate in fitness activities during their graduate school years.     

Planning for research and development— the impact on society

This work upon which this article is based has been designed to identify only the most significant facets of future research and development (R & D) and planning in terms of their potential impact on the economic aspect of society. In order to see the impact in the United States, some contrasts have been drawn against the current and future R & D activities of other countries.

In looking for overt directions in environmental developments, it is impossible to escape the realization that no other activity has the potential to affect the lives of all men to the extent of science and technology. Hopefully, by dealing briefly with many facets of R & D, the great scope of this activity may become more evident.

The first part of this article provides the background against which future trends in R & D are examined. Next, separate considerations of the impact that R & D has on the economic elements of the environment are examined. These discussions form the basis for the hypothesis that R & D planning and decision making must not only consider the organizational viewpoint, but also must consider the environment. In this light, a hypothetical R & D planning model is presented in the last section which attempts to direct the selection of the ends in R & D planning toward some socially responsible goal.     

Toward an index of gender equality

This paper develops a Gender Equality Index (GEI) that is modelled in its thinking and implementation on the Consumer Price Index (CPI). The GEI was computed using annual Ontario data on seven socioeconomic indicators for the years 1975 to 1984. The analysis supports the following conclusions: (1) that it is possible to indentify a subset of indicators that have face validity as measures of relative gender equality; (2) that factor analysis is a useful means for evaluating the construct validity of gender equality; (3) that the resulting GEI reveals a strong upward trend toward gender equality in the latter half of the 1970's and the early 1980's and (4) that this trend has flattened in 1984.     

Decision-making in the public sector- a logical model

The decision making process consists of three basic elements. These factors are goals and standards, personality, and environment. Given these three concepts, the decision maker in the public sector follows identifiable processes. Some of these processes are more valuable and yield better results than others. This work is an attempt to discuss this process after an overview of the subject and to identify a model which will facilitate the decision making procedure.