Phthalates are important industrial chemicals used in the manufacture of a wide range of plastic and nonplastic products and can be divided into two basic groups: those used as plasticizers for synthetic polymers that are incorporated into food wrap, medical tubing, and molded toys, and those used primarily in consumers products such as varnishes, perfumes, nail polishes, and insect repellents. It is conceivable that the route of exposure of an organism to phthalates is an important parameter when considering metabolism of these chemicals in vivo. Phthalates are readily metabolized in the gut, such that oral exposure would not lead to accumulation of high concentrations of these chemicals (1). However, few data are available on the metabolism of this group of chemicals after inhalation or dermal exposure. The primary route of phthalate exposure to the general human population has been presumed to be ingestion. Lower molecular-weight phthalates such as diethyl phthalate (DEP) and di-nbutyl phthalate (DBP) can be absorbed percutaneously, and the more volatile congeners can be inhaled. Dermal absorption is important for products applied to skin. (3) applied a simple pharmacokinetic model to estimate the total daily intake of phthalates that would result in the reported urinary concentrations of monoester metabolites. These intake estimates were used as a measure of total exposure to diethyl phthalate (DEP), di-n-butyl phthalate (DBP), n-butyl benzyl phthalate (BBP), dicyclohexyl phtha-Blount et al. (2) reported a considerable number of observations in which the analyte levels in urine were below the limit of detection (LOD) for the procedure being used. This analysis excluded analytes for which more than 25% of the studied individuals were below the LOD and discarded individuals below the LOD for analytes they did analyze. This represents a substantial loss of information. Maximum likelihood methods for censored observations (4-7) have been used for many years to analyze survival data and data for which some observations cannot be seen, but it is known that the observation is beyond some critical point. For urinary metabolite data, an observation below the LOD can be assumed to have a metabolite concentration less than the LOD. Methods have been developed for analyzing biomarkers of exposure-including observations below the LOD-by using statistical likelihoods and regression methods for censored data (8). Using a likelihood for censored data, these fractional pieces of information contribute to the overall interpretation of the data and can be used in a natural framework to estimate parameters and test for population differences. To account for strata differences of demographic factors, we estimated population-based exposures to phthalates using a weighted analysis in which weights were assigned for each individual group depending on the frequency of their demographic variables in the general U.S. population.The aim of this study was to present methods for the analysis of exposure estimates based on urinary biomar...

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ObjectivesThe present study evaluated the effects of job stress, including organisational system to self-rated depression through a panel study of male municipal firefighters in the Republic of Korea.MethodsA panel of 186 municipal firefighters reported self-rated depressive symptoms according to the Beck Depression Inventory (BDI). The effects of job stress were evaluated using the Korea Occupational Stress Scale, taken one year earlier and classified by the median value. Panel members were classified into Depression or Control groups according to BDI scores, with a cut-off level of ‘over mild depression’ in a follow-up survey.ResultsThe Depression group included 17 (9.1%) workers. Firefighters who scored high on occupational system had an 8.3 times greater risk of being assigned to the Depression group than those who had not (adjusted odds ratio [OR] = 8.03, 95% confidence interval (CI) = [1.73–37.22]). In contrast, job stress from a ‘difficult physical environment’ revealed negative risks related to being classified in the Depression group (AOR = 0.20, 95% CI = [0.04–0.92]).ConclusionsAlthough the healthy worker effect may be involved, job stress based on perceptions of organisational system was a strong risk factor for depression. A comprehensive approach should be considered that encompasses social issues when assessing or mental health in high-risk groups, as well as the practical issue of physiochemical hazards.

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