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Background. To investigate the dermal uptake of 4,4′-diphenylmethane diisocyanate (4,4′-MDI), a study was performed in which 2 female volunteers were exposed to 10 and 25 mg, respectively, of 4,4′-MDI by applying 2.0% 4,4′-MDI in petrolatum over areas where the surface concentration corresponded to 800 µg/cm2. Ten days later, they developed eczematous dermatitis at the area of application. Objectives. To investigate whether the dermal application caused active sensitization to 4,4′-MDI. Methods. Chemical analysis of the 4,4′-MDI preparation used in the application and the amount of 4,4′-MDI not absorbed by the skin was performed with liquid chromatography-mass spectrometry. The volunteers were tested with serial dilutions of 4,4′-MDI and the potentially cross-reacting substances 4,4′-diaminodiphenylmethane (4,4′-MDA), p-phenylenediamine (PPD), and dicyclohexylmethane-4,4′-diisocyanate (DMDI). Results. Patch test results suggested that the volunteers were actively sensitized to 4,4′-MDI following the dermal uptake study, as they reacted positively to 4,4′-MDA, a marker for 4,4′-MDI allergy. No positive reactions were seen to PPD or DMDI. Chemical investigation confirmed that the correct concentration had been used for the dermal uptake study, and showed that about 70% of the applied 4,4′-MDI was not absorbed. Conclusions. A dermal uptake study with 4,4′-MDI in 2.0% pet. with an occlusion time of 8 hr induced active sensitization to 4,4′-MDI and subsequently to 4,4′-MDA. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine workers' mental interpretation models developed in response to occupational chemical exposure. The study was performed in six companies within the reinforced plastics industry in northern Sweden, in which styrene was used; 32 workers participated in the study. Each worker performed between four and seven exposure measurements. Before receiving each result of the second to seventh measurements, the workers were asked to predict the level of their next exposure measurement. Their predictions were evaluated with respect to two judgmental principles: coherence (that the predictions are based on logical decision rules, that is, the mean value of the prior exposure levels); and correspondence (the predictions have high empirical accuracy) by calculating the mean absolute percent forcast error (MAPE). The coherence principle was tested by comparing each of the workers' predictions with the mean, median, and last exposure level (last value) of the prior measurements. The correspondence principle was tested by comparing the worker's prediction with the outcome of the measurement. The coherence principle was found to be the best descriptor of the workers' predictions and the median model had the best fit. The mean model had a similar but significantly poorer fit (MAPE values of 29 and 31, respectively). The correspondence model had a poor fit with a MAPE of 54. The workers' predictions were generally lower than their average exposures. We conclude that the workers' interpretation model can be best described by a coherence model rather than by a correspondence model. [ABSTRACT FROM AUTHOR]

Background: The lead concentration in plasma is correlated to that in whole blood with a two to fourfold variation. It has never been investigated if this variation is inter-individual., Methods: Lead and hemoglobin were determined in blood and plasma from 13 lead workers with a history of relatively high blood-lead concentrations, sampled three times during 1 day. The variation in the distribution of lead between cells and plasma was studied, but not the variation in the lead concentrations as such., Results: Blood hemoglobin decreased with rising plasma lead (0.9-3.0 microg/L). Regarding the distribution of lead, no effect of current exposure during the day or of recent meals appeared. As much as 84% of the overall variance of the distribution of lead between cells and plasma could be attributed to individual factors. After adjustment for erythrocyte volume fraction this decreased to 67%. Plasma samples with elevated hemoglobin concentrations (due to in vitro hemolysis) had somewhat elevated lead concentrations., Conclusions: Plasma lead is not significantly altered by variation in a single day's exposure and, therefore, the choice of time of the day is not critical for sampling. However, plasma lead is negatively correlated to blood hemoglobin and mild hemolysis (not visible by the eye) in a sample may increase plasma lead with up to 30%. Finally, plasma provides lead exposure information that differs from whole blood, but it is not clear which one of these is the biomarker with the closest relation to exposure and/or effects., (Copyright (c) 2006 Wiley-Liss, Inc.)