Characterization and Failure Analysis of Plastics

Volume 11B serves as a reference and guide to help engineers determine the causes of failure in plastic components and make corrective adjustments through design and manufacturing modifications. It contains seven major divisions, covering polymer science and processing, material selection and design, chemical, thermal, and physical analysis, mechanical behavior and testing, degradation mechanisms, systematic failure analysis, and life assessment and optimization. It examines a wide range of factors that contribute to the properties and behaviors of engineering plastics and the effect of thermal and mechanical stresses, impact loading, fatigue, wear, weathering, moisture and chemical exposure, photochemical aging, microbial degradation, and elevated temperatures. It addresses issues such as flammability, environmental stress cracking, crazing, and stress whitening and describes the unique characteristics of polymer fracture and how to assess and predict service life using fracture mechanics. It also presents and analyzes numerous examples of failure, including design and manufacturing related failures, wear failures of reinforced plastics, and failures due to creep and yielding.

MiXie, an Online Tool for Better Health Assessment of Workers Exposed to Multiple Chemicals

There is increasing concern for workers facing multiple chemical exposure. The accumulation of information on occupational conditions indicates the need to incorporate the concept of multiple exposures in the risk assessment process and to develop tools for assessing the potential impacts of multiple exposures on workers’ health. Our objective is to describe the MiXie online decision-making tool that can be used to assess the risk of exposure to multiple chemicals. The description includes the development of MiXie, the structure of its toxicological database according to the target organ or the mode of action, and the algorithm for quantitative analysis of a mixture. Two case studies of its use in evaluating the risks of multiple exposures in real workplace situations are presented. The case study in the printing industry showed increased risk for four toxicological classes (central nervous system damage, ocular damage, skin damage, and ototoxicity) associated with co-exposure to four chemicals during maintenance operations. The MiXie analysis also showed the presence of carcinogenic substances in the mixture and a risk to the development of the foetus. The case study in nail salons showed the presence of carcinogenic and sensitizing chemicals and an increased risk to upper airways. MiXie helps preventers evaluate the possible additive effects of mixtures, providing an easy-to-read diagnosis to identify risks incurred by co-exposed employees. In addition, MiXie identifies risky occupational situations that would go unnoticed without a multiple substance approach.

Development and Evaluation of an In Silico Dermal Absorption Model Relevant for Children

The higher skin surface area to body weight ratio in children and the prematurity of skin in neonates may lead to higher chemical exposure as compared to adults. The objectives of this study were: (i) to provide a comprehensive review of the age-dependent anatomical and physiological changes in pediatric skin, and (ii) to construct and evaluate an age-dependent pediatric dermal absorption model. A comprehensive review was conducted to gather data quantifying the differences in the anatomy and physiology of child and adult skin. Maturation functions were developed for model parameters that were found to be age-dependent. A pediatric dermal absorption model was constructed by updating a MoBi implementation of the Dancik et al. 2013 skin permeation model with these maturation functions. Using a workflow for adult-to-child model extrapolation, the predictive performance of the model was evaluated by comparing its predicted rates of flux of diamorphine, phenobarbital and buprenorphine against experimental observations using neonatal skin. For diamorphine and phenobarbital, the model provided reasonable predictions. The ratios of predicted:observed flux in neonates for diamorphine ranged from 0.55 to 1.40. For phenobarbital, the ratios ranged from 0.93 to 1.26. For buprenorphine, the model showed acceptable predictive performance. Overall, the physiologically based pediatric dermal absorption model demonstrated satisfactory prediction accuracy. The prediction of dermal absorption in neonates using a model-based approach will be useful for both drug development and human health risk assessment.

Next-generation biomonitoring of the early-life chemical exposome in neonatal and infant development

Exposure to man-made and natural chemicals is a major, yet not sufficiently considered, environmental risk factor in the etiology of chronic diseases. Current human biomonitoring approaches typically measure a limited number of exposures rather than investigating complex mixtures. The latter would be fundamental and necessary for a holistic assessment of chemical exposure in exposome-wide association studies. In this work, an highly-sensitive liquid chromatography-tandem mass spectrometry approach was developed and thoroughly-validated. The assay enables the simultaneous and targeted assessment of more than 80 highly-diverse xenobiotics in the investigated body fluids of urine, serum/plasma, and breast milk; the detection limit for most toxicants are in the pg-ng/mL range. In the plasma of extremely-premature infants (gestational age <28 weeks, birth weight <1 kg) a total of 27 different xenobiotics are identified; including severe contamination with synthetic plasticizers, perfluorinated alkylated substances and parabens. In an independent sample set of breast milk that was longitudinally collected over the first 211 days post-partum, a total of 29 analytes is detected, including the first-ever identification of pyrrolizidine- and tropane alkaloids in this matrix. Based on the generated data, a preliminary estimation of daily toxicant intake via breast milk is conducted. In conclusion, our proof-of-principle experiments show significant early-life co-exposure to multiple toxicants, and demonstrate the method’s applicability in future large-scale exposomics-type cohort studies in vulnerable populations.

Profile of Environmental Chemicals in the Korean Population—Results of the Korean National Environmental Health Survey (KoNEHS) Cycle 3, 2015–2017

The Korean National Environmental Health Survey (KoNEHS) program provides useful information on chemical exposure, serves as the basis for environmental health policies, and suggests appropriate measures to protect public health. Initiated on a three-year cycle in 2009, it reports the concentrations of major environmental chemicals among the representative Korean population. KoNEHS Cycle 3 introduced children and adolescents into the analysis, where the blood and urine samples of 6167 participants were measured for major metals, phthalates, phenolics, and other organic compounds. Lead, mercury, cadmium, metabolites of DEHP and DnBP, and 3-phenoxybenzoic acid levels of the Korean adult population tended to decrease compared to previous survey cycles but remained higher than those observed in the US or Canada. Both bisphenol A (BPA) and trans,trans-muconic acid concentrations have increased over time. Heavy metal concentrations (blood lead, and cadmium) in children and adolescents were approximately half that of adults, while some organic substances (e.g., phthalates and BPA) were high. BPA showed higher levels than in the US or Canada, whereas BPF and BPS showed lower detection rates in this cycle; however, as these are increasingly used as a substitute for BPA, further research is necessary. As environmental chemicals may affect childhood health and development, additional analyses should assess exposure sources and routes through continuous observations.

RISK FACTORS IN THE PROCESS OF EMPLOYMENT OF MEDICAL WORKERS OF THE DENTAL PROFILE

One of the most socially important types of work is the work of medical workers. Due to the presence of a significant number of harmful and dangerous factors, the medical profession is divided into a separate group, which in turn is characterized by unique aspects of work. The work of doctors and nurses of different specialties of the dental profile differs significantly in the density of the working day, the volume and nature of professional activities; responsibility for the life of the patient, which affects many physiological processes. The purpose. Assessment and comparative characterization of the presence of occupational risks in the dental field, which are daily exposed to factors of aggressive and dangerous nature, as well as the development of a set of preventive measures aimed at reducing occupational morbidity. Materials and methods. Hygienic research of working conditions of medical staff of the University Dental Clinic in the form of a questionnaire. Statistical analysis of data of special assessment of working conditions; sanitary and hygienic characteristics, acts, maps of cases of nosocomial diseases; laboratory and instrumental research conducted as part of production control; dosimetric control, air sampling with subsequent sowing on the nutrient medium of IPA. Results. It was found that in the studied premises, the total microbial count varied from 756 ± 0.8 CFU / 1m3 to 6497 ± 3.4 CFU / 1m3. In most medical institutions, the level of artificial lighting in the workplaces of medical workers was insufficient. The largest negative contribution was provided by such production factors as: labor intensity and intensity - 26.41%; physical: noise, vibration, non-ionizing and ionizing radiation - 25.32%; chemical - 12.77%. The total contribution of the main factors was 91.78%. Assessment of working conditions is based on hygienic criteria to assess the degree of deviations of the parameters of the production environment and labor process from the current hygienic standards, as well as after analysis and processing of data submitted by employees in the format of their questionnaires. In this regard, the distribution of harmful production factors and their degree of impact on the health of medical personnel was established with the help of multifactor analysis. Conclusions. Thus, the research interprets the results, which clearly in the format of a specific percentage, identify those factors that have a strong driving impact on the health of dental professionals. The most substantiated are such production factors as: chemical (exposure to drugs and chemicals), physical (noise and vibration, non-ionizing and ionizing radiation), the severity and intensity of the labor process, lighting (non-compliance with regulations for artificial lighting in the workplace) and microclimate and biological (work with biological, potentially contaminated material, samples, patients), non-ionizing and ionizing radiation, labor intensity (tension of the visual organs).

Ultrasensitive analysis of genetic instability related to chemical exposure

Our concerns have been raised about whether prolonged exposure to ammunition-related chemicals could correlate with genomic instability predisposing to lung carcinogenesis. The group of professional soldiers engaged in routine ammunition analysis and its explosive properties testing. To assess the presence of an innate genetic profile, DNA isolated from swabs was analyzed with LungCarta and HS Lung Panels and MassARRAY Analyzer 4 mass spectrometry. The presence of new somatic single nucleotide polymorphisms (SNPs) was detected with liquid biopsy technique and circulating cell-free DNA (ccfDNA) isolation, which was further analyzed with UltraSeek Lung Panel. Both genetic profiles obtained for each individual were compared. Genetic analysis revealed that in professional soldiers with long-term exposure to ammunition-related toxic chemicals, new SNPs in genes related to lung carcinogenesis are present. The preliminary data indicate that using modern molecular techniques could be a valuable tool for monitoring the genome instability in context of occupational risk of harmful volatile toxic compounds and improving personnel safety. The analyzed group will be further enlarged, and follow-up studies will be continued.

From Extrapolation to Precision Chemical Hazard Assessment: The Ecdysone Receptor Case Study

Hazard assessment strategies are often supported by extrapolation of damage probabilities, regarding chemical action and species susceptibilities. Yet, growing evidence suggests that an adequate sampling of physiological responses across a representative taxonomic scope is of paramount importance. This is particularly relevant for Nuclear Receptors (NR), a family of transcription factors, often triggered by ligands and thus, commonly exploited by environmental chemicals. Within NRs, the ligand-induced Ecdysone Receptor (EcR) provides a remarkable example. Long regarded as arthropod specific, this receptor has been extensively targeted by pesticides, seemingly innocuous to non-target organisms. Yet, current evidence clearly suggests a wider presence of EcR orthologues across metazoan lineages, with unknown physiological consequences. Here, we address the state-of-the-art regarding the phylogenetic distribution and functional characterization of metazoan EcRs and provide a critical analysis of the potential disruption of such EcRs by environmental chemical exposure. Using EcR as a case study, hazard assessment strategies are also discussed in view of the development of a novel “precision hazard assessment paradigm.

Differences in personal care product use by race/ethnicity among women in California: implications for chemical exposures

Background Personal care products may contain many chemicals, some of which are suspected endocrine disrupters. This is an important source of chemical exposure for women, but little is known about how chemical exposure differs among different races/ethnicities. Objective This study examines differences in personal care product use among Black, Latina, Vietnamese, Mixed Race, and White women in California. Methods We used a community-based participatory process to create and administer a personal care product usage survey to 321 Black, Latina, Vietnamese, Mixed Race, and White women. We used multivariate regression models with pairwise comparisons to examine the frequency of product use by race/ethnicity. Results We found distinct trends of personal care product use by race/ethnicity: Latina women typically used makeup most frequently; Black women used certain hair products or styles most frequently; and Vietnamese women were most likely to use facial cleansing products compared to other races/ethnicities. Latina and Vietnamese women were less likely to try to avoid certain ingredients in their products. Significance These findings can help estimate disparities in chemical exposure from personal care product use and complement future research on health inequities due to chemical exposures in the larger environmental and social context.