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.     

Sharing genetic origins information in third party assisted conception: a case for Victorian family values?

In the United Kingdom (UK) approximately 2500 children are born each year as a result of third party assisted conception. Since formal record keeping by the statutory regulatory body, the Human Fertilisation and Embryology Authority, began in 1991, the total number of children known to have been born from all forms of third party assisted conception exceeds 13 500. Although the records contain information about these children's genetic origins, including the identity of the donor, current legislation severely circumscribes their ability to access this information and, save in very exceptional circumstances, they are not permitted to learn the identity of the donor. Consequently, they are the only individuals in the UK whose inability to learn the identity of both their genetic parents is formally endorsed by statute. This paper identifies different approaches to exchanging genetic origins information in third party assisted conception. It provides a critique of the model currently in force in the UK and advocates its replacement by a system that more closely resembles that introduced in Victoria (Australia) in 1998. Copyright © 2000 John Wiley & Sons, Ltd.     

'You've gotta learn how to play the game': homeless women's use of gender performance as a tool for preventing victimization

As a masculinist space, ‘the streets’ present a variety of dangers to homeless women, a fact that has received too little attention within the social science literature. This study utilizes data drawn from interviews with homeless women and service providers in Edinburgh, San Francisco, Vancouver, Montreal and Ottawa, to explore the complex survival strategies that homeless women develop to prevent criminal victimization. Through women's words, we see that gender is understood strategically as performance. Four gender performances are identified and discussed: the ‘femininity simulacrum’, the ‘masculinity simulacrum’, ‘genderlessness’ and ‘passing’. We discussed how each of these performances is employed in the pursuit of safety and security in frequently violent and chaotic social spaces.     

Normalité asymptotique d'estimateurs convergents du mode conditionnel

We state sufficient conditions for asymptotic normality of convergent estimates of the conditional mode, irrespective of data dependence, and give an application to α-mixing stationary processes.     

Contrôle des normes internationales du travail et complémentarité des systèmes nationaux et internationaux: récentes évolutions

Les systèmes nationaux et internationaux de régulation du travail, loin de s'opposer, sont largement imbriqués. De hautes juridictions nationales ont utilisé les normes de l'OIT dans de récentes décisions. Les auteurs décryptent les conditions et les conséquences de cet usage en examinant deux décisions de la Cour suprême du Canada (liberté syndicale) et une de la Cour d'appel de Paris (contrat de travail). Outre que ces affaires ont fait l'objet de procédures tant nationales qu'internationales, le choix de pays aux cultures juridiques différentes permet de discuter l'appropriation du droit international du travail par les juridictions nationales.