ABSTRACT
A simple mathematical equation based on a diffusion model has been utilized recently to estimate migration of both acrylonitrile and styrene from polymers produced from these monomers which are used under a wide variety of food-contact applications. These calculated migration values have subsequently been used to estimate the US consumer's exposure to acrylonitrile and styrene from food stored in these materials. The basic assumptions integral to the model are discussed in relation to potential errors in migration estimates that could be experienced if the assumptions are not true. In addition to the discussion of the basic assumptions, factors affecting the migration predictions such as polymer 'ageing', temperature changes during the lifetime of the polymeric article, the effects of polymer-modifying materials (plasticizers, impact modifiers), and the physical form of the article or test sample are discussed.
Subject(s)
Acrylonitrile , Food Contamination , Food Packaging , Models, Theoretical , Styrenes , Diffusion , Humans , TemperatureABSTRACT
An approach has been developed to estimate the exposure of consumers to styrene from polystyrene food-contact articles which incorporates published literature on the diffusion of styrene through polymeric materials and industry survey data on uses of polystyrene in food-contact applications. The approach has been shown to be quite practical and has yielded an exposure estimate of 3 ppb (9 micrograms/day) styrene, on average, in the daily diet of people in the United States. This value compares reasonably well with the value of 1-4 micrograms/day for residents of the United Kingdom in 1983. The value is also four orders of magnitude less than the acceptable daily intake calculated by the Styrene Information and Research Center.
Subject(s)
Diet/adverse effects , Food Packaging , Polymers/analysis , Polystyrenes/analysis , Styrenes/analysis , Animals , Humans , Models, Biological , Styrene , Styrenes/adverse effectsABSTRACT
The correlation of residual acrylonitrile (AN) monomer concentration in AN-containing polymers with AN migration into food simulants is of interest because the US FDA regulates the use of these polymers on the basis of the amount of AN that may migrate into food simulants. Studies of the migration of AN into water from seven acrylonitrile/butadiene/styrene polymers with varying composition and residual AN levels showed that a linear relationship exists between the concentration of AN in the polymer and the amount of AN migrating, for a given set of exposure conditions. A linear relationship was also observed between the diffusion coefficients generated from the experimental data using a simple Fickian diffusion model and the inverse of the absolute temperature of exposure.
Subject(s)
Acrylonitrile/chemistry , Beverages , Butadienes , Styrenes , Diffusion , Ethanol/chemistry , Polymers , Temperature , Water/chemistryABSTRACT
In the study reported here the authors examined the relationships among 40 measures of undergraduate college and medical school performance and competence in 18 medical care tasks during the first year of residency. A rating form was developed for the study to assess residents' competency in the medical care tasks and was sent to the directors of the residency programs entered by the graduates of a medical school. Stepwise multiple regression procedures were used to analyze the relationship between these ratings of residency performance and the residents' premedical and medical school performance and to identify the best predictors of residency performance for the 1982 and 1984 classes. A Rasch model analysis of the residency performance ratings indicated the ease or difficulty of each of the 18 tasks. The results provide information that would allow medical educators to use premedical and medical school performance to predict residents' competencies. The task of "clinically evaluates research and clinical data" was the most difficult for the graduates; that is, they were rated lower on it than on any other task. Two groups of measures of undergraduate and medical school performance were significantly related to performance in the residency: the Part II examination of the National Board of Medical Examiners (particularly the scores on the obstetrics-gynecology, medicine, surgery, and pediatrics subtests and the overall score) and the clerkships (particularly the third-year medicine clerkship, the fourth-year medicine clerkship, and the surgery clerkship).
