Health risk assessment of construction workers from trace metals in PM2.5 from Kolkata, India.

Construction activities have long been recognized as a pertinent source of PM2.5 though limited information exists regarding chemical characteristics of aerosols generated during building demolition/construction. A comprehensive investigation was carried out to assess the physical (SEM analysis) and chemical (ICP MS analysis) properties of PM2.5 in a building demolition and construction site and compared with background. Average concentrations of PM2.5 at both the sites exceeded the National Ambient Air Quality Standards (NAAQS). Overall trend of the total metal concentrations of PM2.5 followed the order of (Na, Ca, Al, Mg, Fe, Zn) > (Ti, Sr, Cd, Ba, Pb, V, Cr, Mn, Co, Ni, Cu) in both the sites. Sr, Ba, Mg, Zn, Ti, Cd, Al, Cr, Fe, Co, Mn, V, Ni, Ca, and Zn showed a ∼1.3-3.0 fold increase, and Pb showed the highest increase of almost >3.5 times when compared to the background concentrations. Health risk estimates based on the bio-available concentration of metals indicated that hazard quotient (HQ) values for non-carcinogenic metals were within the prescribed limit (HQ ≤ 1). However, the excess lifetime cancer risk (ELCR) for the carcinogenic metals Pb, Ni, Cd, and Cr(VI) were higher than the guideline limits of USEPA.

Viability of cultured human skin cells treated with 1,6-hexamethylene diisocyanate monomer and its oligomer isocyanurate in different culture media.

The isocyanate monomer 1,6-hexamethylene diisocyanate (HDI) and one of its trimers, HDI isocyanurate, are airway and skin sensitizers contained in polyurethane paint. The toxic response of cultured skin cells to these compounds was measured by evaluating the isocyanate concentrations at which 50% of the cells die (i.e., lethal concentration 50%, LC50) because the relative toxicity of each form of HDI should be considered when exposure limits of HDI-based paints are set. By using a luminescent ATP-viability assay, we compared the cytotoxic effects of HDI monomer and HDI isocyanurate on cultured human skin cells (keratinocytes, fibroblasts, and melanocytes) after 4-h isocyanate exposures using culture media with varying levels of nutrients in order to also determine the effects of media composition on isocyanate toxicity. Before analysis, experimental wells were normalized to controls containing cells that were cultured with the same vehicle and media. The measured mean LC50 values ranged from 5 to 200 µM across the experimental conditions, in which HDI isocyanurate in protein-devoid media was the most toxic to cells, producing the lowest LC50 values. For HDI monomer, keratinocytes were the most resistant to its toxicity and melanocytes were the most susceptible. However, when exposed to HDI isocyanurate, the opposite was observed, with melanocytes being the most resilient and the keratinocytes and fibroblasts were more susceptible. Depending on the type of skin cells, dose-response data indicated that HDI isocyanurate was 2-6 times more toxic than HDI monomer when using protein-devoid media whereas HDI isocyanurate was 4-13 times more toxic than HDI monomer when protein-rich media was used. Therefore, if the protein-devoid saline medium alone were used for these experiments, then a significant under-estimation of their relative toxicities in protein-rich environments would have resulted. This difference is because HDI monomer toxicity was more attenuated by the presence of protein in the culture media than HDI isocyanurate toxicity. Thus, conclusions based on comparative toxicity studies and consequent inference applied to potential human toxicity can be affected by in vitro culture media conditions. The physiochemical difference in reactivity of the two forms of HDI to biological molecules most likely explains the observed toxicity differences and may have implications for skin penetration, adverse effects like skin sensitization, and systemic responses like asthma. Future studies are warranted to investigate differences in the biological availability, cellular toxicity, and immunologic sensitization mechanisms for HDI monomer and HDI isocyanurate.

Toxicity of stainless and mild steel particles generated from gas-metal arc welding in primary human small airway epithelial cells.

Welding fumes induce lung toxicity and are carcinogenic to humans but the molecular mechanisms have yet to be clarified. The aim of this study was to evaluate the toxicity of stainless and mild steel particles generated via gas-metal arc welding using primary human small airway epithelial cells (hSAEC) and ToxTracker reporter murine stem cells, which track activation of six cancer-related pathways. Metal content (Fe, Mn, Ni, Cr) of the particles was relatively homogenous across particle size. The particles were not cytotoxic in reporter stem cells but stainless steel particles activated the Nrf2-dependent oxidative stress pathway. In hSAEC, both particle types induced time- and dose-dependent cytotoxicity, and stainless steel particles also increased generation of reactive oxygen species. The cellular metal content was higher for hSAEC compared to the reporter stem cells exposed to the same nominal dose. This was, in part, related to differences in particle agglomeration/sedimentation in the different cell media. Overall, our study showed differences in cytotoxicity and activation of cancer-related pathways between stainless and mild steel welding particles. Moreover, our data emphasizes the need for careful assessment of the cellular dose when comparing studies using different in vitro models.

Exposure to respirable dust among workers fabricating aluminium trihydroxide-containing synthetic countertops.

The aim of this study is to characterize personal exposure of workers to respirable particulate matter (PM) generated in cutting and other fabrication activities when fabricating acryl polymer/aluminium trihydroxide synthetic countertops. We collected 29 personal full-day samples of respirable PM from three workers in a small private workshop. We tested differences between- and within-worker variances of mass concentrations using the Kruskall-Wallis test. We used segmented regression to test the means and medians 15-min interval concentrations changes over time and to identify a breakpoint. Respirable PM concentrations ranged nearly 100-fold, from 0.280 to 25.4 mg/m3 with a median of 2.0 mg/m3 (1-min concentrations from 13,920 data points). There were no statistical difference in daily median or geometric mean concentrations among workers, whereas the concentrations were significantly higher on days with three versus two workers present. The 15-min median concentrations (n = 974 measures) increased until 2.35 h (beta 0.177; p < 0.05), representing a 0.70 mg increase in exposure per hour. This was followed by a plateau in concentrations. The high levels of respirable PM we observed among workers fabricating aluminium trihydroxide-containing synthetic countertops highlight an unmet early prevention need.

Dietary quality and bisphenols: trends in bisphenol A, F, and S exposure in relation to the Healthy Eating Index using representative data from the NHANES 2007-2016.

BACKGROUND: Given policy regulations restricting bisphenol A (BPA) in food-related products, and consumer concerns about adverse health effects, newer bisphenols such as bisphenol F (BPF) and bisphenol S (BPS) have been developed. Exposure to BPA has been linked to dietary behaviors and poor health outcomes. OBJECTIVES: We sought to examine how the Healthy Eating Index (HEI) and its 13 subgroups, the healthy American diet, the Mediterranean diet, the vegetarian diet, and other dietary quality behaviors are related to BPA and the newer substitutes in a representative sample of US adults. METHODS: Dietary intakes from the NHANES were used to determine dietary scores. Osmolality-adjusted urinary BPA (n = 6418) and BPF and BPS (n = 2520) concentrations were tested for their association with dietary intake in models that adjusted for sociodemographics. RESULTS: Compared with low scores, high scores for total HEI and the American, Mediterranean, and vegetarian diets were associated with lower odds of high BPA concentration (OR: 0.65, 0.60, 0.59, and 0.60, respectively). Of the HEI subgroups, lower BPA concentration was associated with high total fruit (OR: 0.61; 99.95% CI: 0.42, 0.89), whole fruit (OR: 0.59; 99.95% CI: 0.41, 0.86), and whole grain (OR: 0.68; 99.95% CI: 0.40, 0.94) intake, when compared with low intakes. Compared with low intakes, high intakes of plain and tap water were associated with lower odds of high BPA concentration (OR: 0.65; 99.95% CI: 0.47, 0.91 and OR: 0.70; 99.95% CI: 0.50, 0.99, respectively). A perception of high, compared with low, dietary quality was also associated with lower odds of high BPA concentration (OR: 0.72; 99.95% CI: 0.53, 0.98). CONCLUSIONS: Healthier dietary quality and several HEI subgroups were related to lower urinary BPA concentrations; no significant (P ≤ 0.0005) findings were observed for BPF and BPS. The association between bisphenol substitutes and dietary quality should continue to be monitored as bisphenol substitutes continue to increase in the food system.

Bisphenol-A inhibits mitochondrial biogenesis via impairment of GFER mediated mitochondrial protein import in the rat brain hippocampus.

Mitochondrial biogenesis relies on different protein import machinery, as mitochondrial proteins are imported from the cytosol. The mitochondrial intermembrane space assembly (MIA) pathway consists of GFER/ALR and CHCHD4/Mia40, responsible for importing proteins and their oxidative folding inside the mitochondria. The MIA pathway plays an essential role in complex IV (COX IV) biogenesis via importing copper chaperone COX17, associated with the respiratory chain. BPA, an environmental toxicant, found in consumable plastics, causes neurotoxicity via impairment in mitochondrial dynamics, neurogenesis, and cognitive functions. We studied the levels of key regulatory proteins of mitochondrial import pathways and mitochondrial biogenesis after BPA exposure in the rat hippocampus. BPA caused a significant reduction in the levels of mitochondrial biogenesis proteins (PGC1α, and TFAM) and mitochondrial import protein (GFER). Immunohistochemical analysis showed reduced co-localization of NeuN with GFER, PGC-1α, and TFAM suggesting impaired mitochondrial biogenesis and protein import. BPA exposure resulted in damaged mitochondria with distorted cristae in neurons and caused a significant reduction in GFER localization inside IMS as depicted by immunogold electron microscopy. The reduced levels of GFER resulted in defective COX17 import. The translocation of cytochrome c into the cytosol and increased cleaved caspase-3 levels triggered apoptosis due to BPA toxicity. Overall, our study implicates GFER as a potential target for impaired mitochondrial protein machinery, biogenesis, and apoptosis against BPA neurotoxicity in the rat hippocampus.

Review of the physicochemical properties and associated health effects of aerosols generated during thermal spray coating processes.

Thermal spray coating is a process that applies a molten metal product under pressure onto a surface. Although thermal spray processes have been used for decades, exposure to aerosols formed during thermal spray coating is an emerging risk. Reports indicate that high concentrations of aerosols composed of toxic metals (e.g. chromium) are generated in the workplace. A knowledge gap exists related to the physicochemical properties of thermal spray coating aerosols as well as any potential associated health effects. The objective of this manuscript was to review thermal spray coating and previous studies that have examined the aerosols produced from this process. A thermal spray coating generator and exposure system is also described that has recently been developed to further evaluate the physical and chemical properties of aerosols formed during thermal spray coating as well as to assess the possible health effects of this process in an effort to mitigate potential occupational health hazards related to the industry.

Probabilistic model for assessing occupational risk during the handling of nanomaterials.

Exposure to nanomaterials (NMs) can be considered as human, occupational or environmental. Occupational exposure may be experienced by the workers and/or researchers who develop and produce these products and the hazards inherent to exposure are not yet fully known. Quantitative and qualitative methods are available to estimate the occupational risks associated with the handling of NMs, however, both have limitations. In this context, the objective of this study was to create a Bayesian network (BN) that will allow an assessment of the occupational risk associated with the handling of NMs in research laboratories. The BN was developed considered variables related to exposure, the hazards associated with NMs and also the existing control measures in the work environment, such as collective protection equipment (CPE), administrative measures and personal protection equipment (PPE). In addition to assessing the occupational risk, simulations were carried out by the laboratory manager to obtain information on which actions should be taken to reduce the risk. The development of a BN to assess the occupational risk associated with the handling of NMs is a novel aspect of this study. As a distinctive feature, the BN has measurement control variables in addition to considering CPE, administrative measures and PPE. An advantage of this network in relation to other risk assessment models is that it allows the easy execution of simulations and provides a guide for a decision making by identifying which actions should be taken to minimize the risk.

Development of a method for quantification of toluene diisocyanate and methylenediphenyl diisocyanate migration from polyurethane foam sample surface to artificial sweat by HPLC-UV-MS.

The US Environmental protection agency (EPA) has published guidance that includes test procedures for evaluating indoor exposure to chemicals from products. One of the test procedures represents the migration test for evaluating potential dermal exposure from home furniture. Such an evaluation involves the chemical measurement of the sweat which is currently unavailable in the literature. The objective of this project was to develop and validate an analytical method for quantification of migration of 4,4'-methylenediphenyl diisocyanate (MDI), 2,6-toluene diisocyanate (2,6-TDI) and 2,4-toluene diisocyanate (2,4-TDI) from a polyurethane (PU) flexible foam to artificial sweat that meets the recommendations of the EPA test protocol. Following the EPA protocol, six synthetic sweat solutions were prepared and used in evaluation of isocyanate recovery performance. The migration tests were conducted using five foam types that were chosen and supplied by PU foam manufacturers to represent the types most commonly found in commercial products, and with formulations anticipated to have the highest potential residual TDI or MDI. Migration tests were conducted using glass fiber filters (GFF) coated with 1-(2-methoxyphenyl)piperazine (1,2-MP) and analyzed using HPLC equipped with a UV detector for quantification and a MS detector to qualify peaks. The detection limits of the method were 0.002 µg/mL for 2,6-TDI, 0.011 µg/mL for 2,4-TDI, and 0.003 µg/mL for MDI. Quantification limits were 0.006 µg/mL, 0.037 µg/mL, and 0.010 µg/mL, respectively. The recovery tests on a Teflon surface for 5 of the 6 EPA-recommended synthetic sweat solutions indicate the recovery percentage was approximately 80% for diisocyanates. Recovery for the sixth sweat solution was low, approximately 30%. TDI and MDI migration was not observed when testing was conducted on foam samples.

Advances in BPA-induced Oxidative Stress and Related Effects and Mechanisms in Liver, 1991-2017.

Bisphenol A (BPA) is a widely spreading environmental endocrine disruptor . Its characteristics, including small doses and frequent contact, make it easy to enter human body through drinking water, food, air and other pathways, leading to tumors, infertility, and liver damage. The present review summarizes the underlying mechanism of oxidative stress and its related effects induced by BPA in the liver. The progress of the mechanism for oxidative stress induced by BPA is summarized, including mitochondrial dysfunction, lipid peroxidation and inflammation reaction, liver dyslipidemia, apoptosis, and cell death mechanism. In the future, it is necessary to elucidate the molecular mechanisms and timing of oxidative stress to clarify the effects on different exposures to different genders and growth stages. Besides, studying the toxic effects on BPA surrogates, BPA metabolites and BPA combined with other pollutants in the environment is beneficial to clarify the environmental and human health effects of BPA and provide technical reference for the development of practical control measures.

Assessment of the physicochemical properties of chrysotile-containing brake debris pertaining to toxicity.

Grinding and drilling of chrysotile asbestos-containing brake pads during the 20th century led to release of chrysotile, resulting in varying levels of workplace exposures of mechanics. Despite exposures, excess risk of mesothelioma remains in doubt. Objectives: The toxicity of particulates is primarily derived through a combination of physicochemical properties and dose and as such this study aimed to determine properties of asbestos-containing brake debris (BD) which may influence pathogenicity and potential of mesothelioma. Materials and Methods: Chrysotile-containing brake pads were ground - to reflect occupational activities, aerosolized, and size-fractionated to isolate respirable fractions. Analysis of morphology, biodurability, surface charge, and interactions with macrophages were undertaken. Results: The respirable fraction of BD contained ∼15-17% free chrysotile fibers thereby constituting a small but relevant potential long fiber dose. Acellular biodurability studies showed rapid dissolution and fragmentation of chrysotile fibers that was consistent for pure chrysotile control and BD samples. Conclusions: The long, free, respirable chrysotile fibers were present in BD, yet were of low bio-durability; incubation in artificial lysosomal fluid led to destruction of free fibers.

Flavorings-Related Lung Disease: A Brief Review and New Mechanistic Data.

Flavorings-related lung disease is a potentially disabling and sometimes fatal lung disease of workers making or using flavorings. First identified almost 20 years ago in microwave popcorn workers exposed to butter-flavoring vapors, flavorings-related lung disease remains a concern today. In some cases, workers develop bronchiolitis obliterans, a severe form of fixed airways disease. Affected workers have been reported in microwave popcorn, flavorings, and coffee production workplaces. Volatile α-dicarbonyl compounds, particularly diacetyl (2,3-butanedione) and 2,3-pentanedione, are implicated in the etiology. Published studies on diacetyl and 2,3-pentanedione document their ability to cause airway epithelial necrosis, damage biological molecules, and perturb protein homeostasis. With chronic exposure in rats, they produce airway fibrosis resembling bronchiolitis obliterans. To add to this knowledge, we recently evaluated airway toxicity of the 3-carbon α-dicarbonyl compound, methylglyoxal. Methylglyoxal inhalation causes epithelial necrosis at even lower concentrations than diacetyl. In addition, we investigated airway toxicity of mixtures of diacetyl, acetoin, and acetic acid, common volatiles in butter flavoring. At ratios comparable to workplace scenarios, the mixtures or diacetyl alone, but not acetic acid or acetoin, cause airway epithelial necrosis. These new findings add to existing data to implicate α-dicarbonyl compounds in airway injury and flavorings-related lung disease.

Does exposure to bentonite dust during tunnel hyperbaric interventions increase health risks for compressed air workers? A prospective qualitative and quantitative safety assessment.

INTRODUCTION: The mining and tunneling industries are historically associated with hazardous exposures that result in significant occupational health concerns. Occupational respiratory exposures causing pneumoconiosis and silicosis are of great concern, silicosis being non-curable. This work demonstrates that compressed-air workers (CAWs) performing tunnel hyperbaric interventions (HIs) may be at risk for hazards related to bentonite exposure, increasing the likelihood of developing harmful illnesses including cancer. Bentonite dust inhalation may result in respiratory levels of silica exceeding acceptable industrial hygiene standards. METHODS: A qualitative observational exposure assessment was conducted on CAWs while they were performing their HI duties. This was followed by quantitative data collection using personal and area air sample techniques. The results were analyzed and interpreted using standard industrial hygiene principles and guidelines from NIOSH and OSHA. RESULTS: Our work suggests bentonite dust exposure may be an emerging particulate matter concern among CAWs in the tunneling industry. Aerosolized bentonite particles may have potential deleterious effects that include pneumoconiosis and silicosis. Silicosis can result in the development of pulmonary carcinoma. CONCLUSIONS: The modern tunneling industry and required hyperbaric interventional tasks represent a potential public health and occupational concern for CAWs. This paper introduces the modern tunneling industry and the duties of CAWs, the hazardous environment in which they perform their duties, and describes the risks and potential harmful health effects associated with these hazardous exposures.

High variability in toxicity of welding fume nanoparticles from stainless steel in lung cells and reporter cell lines: the role of particle reactivity and solubility.

Millions of people in the world perform welding as their primary occupation resulting in exposure to metal-containing nanoparticles in the fumes generated. Even though health effects including airway diseases are well-known, there is currently a lack of studies investigating how different welding set-ups and conditions affect the toxicity of generated nanoparticles of the welding fume. The aim of this study was to investigate the toxicity of nine types of welding fume particles generated via active gas shielded metal arc welding (GMAW) of chromium-containing stainless steel under different conditions and, furthermore, to correlate the toxicity to the particle characteristics. Toxicological endpoints investigated were generation of reactive oxygen species (ROS), cytotoxicity, genotoxicity and activation of ToxTracker reporter cell lines. The results clearly underline that the choice of filler material has a large influence on the toxic potential. Fume particles generated by welding with the tested flux-cored wire (FCW) were found to be more cytotoxic compared to particles generated by welding with solid wire or metal-cored wire (MCW). FCW fume particles were also the most potent in causing ROS and DNA damage and they furthermore activated reporters related to DNA double- strand breaks and p53 signaling. Interestingly, the FCW fume particles were the most soluble in PBS, releasing more chromium in the hexavalent form and manganese compared to the other fumes. These results emphasize the importance of solubility of different metal constituents of the fume particles, rather than the total metal content, for their acute toxic potential.

Simultaneous analysis of bisphenol A fractions in maternal and fetal compartments in early second trimester of pregnancy.

Background Bisphenol A (BPA) is an estrogenic, endocrine-disrupting compound widely used in the industry. It is also a ubiquitous environmental pollutant. Its presence was confirmed in human fetuses, which results from maternal exposure during pregnancy. The mechanisms behind maternal-fetal transfer, and relationships between pregnant women and fetal exposures remain unclear. The aim of this study was to assess the impact of maternal exposure to BPA on the exposure of the fetus. Methods Maternal plasma and amniotic fluid samples were collected from 52 pregnant women undergoing amniocentesis for prenatal diagnosis of chromosomal abnormalities. BPA was measured by gas chromatography-mass spectrometry (GC-MS). The permeability factor - a ratio of fetal-to-maternal BPA concentration - was used as a measure delineating the transplacental transfer of BPA. Results The median concentration of maternal plasma BPA was 8 times higher than the total BPA concentration in the amniotic fluid (8.69 ng/mL, range: 4.3 ng/mL-55.3 ng/mL vs. median 1.03 ng/mL, range: 0.3 ng/mL-10.1 ng/mL). There was no direct relationship between the levels of BPA in maternal plasma and amniotic fluid levels. The permeability factor, in turn, negatively correlated with fetal development (birth weight) (R = -0.54, P < 0.001). Conclusion Our results suggest that the risk of fetal BPA exposure depends on placental BPA permeability rather than the levels of maternal BPA plasma concentration and support general recommendations to become aware and avoid BPA-containing products.

Emission profiles, ozone formation potential and health-risk assessment of volatile organic compounds in rubber footwear industries in China.

The emission characteristics of VOCs in the rubber footwear industry (RFI) and its effect on human health are poorly understood to date. Herein, up to 68 VOCs, sorted into seven classes including alkanes, alkenes, acetylene, aromatics, halocarbons, carbon disulfide, and oxygenated VOCs, were monitored. VOCs emitted from three main processing stages of RFI, including shaping, painting and vulcanizing, were 383, 1507 and 1026 mg/m3, respectively. The top 10 VOCs contributing to the concentration and ozone formation potential were identified. Generally, alkanes were the major component emitted from three stages, contributing 48.58%-63.07% of the total VOCs. Alkenes contributed most to the OFP, accounting for 37.2%-69.1%. Based on the risk assessment, a definite cancer risk for workers in shaping workshop should be noticed. Several VOCs with a life carcinogenic risk higher than 10-4, especially benzene, bromodichloromethane, ethylbenzene and 1,1,2-trichloroethane, should be focused on. Therefore, more attention should be taken for the extended-ranges of VOCs in subordinate RFI, except for the publicly concerned aromatics in rubber industry. A VOCs emission inventory from the production process of Chinese RFI in 2000-2016 was compiled. It is estimated that Chinese RFIs have emitted a total of 319 × 104 t VOCs in those past 17 years.

Kinetics of isoflurane and sevoflurane in a unidirectional displacement flow and the relevance to anesthetic gas exposure by operating room personnel.

International guidelines recommend the use of ventilation systems in operating rooms to reduce the concentration of potentially hazardous substances such as anesthetic gases. The exhaust air grilles of these systems are typically located in the lower corners of the operating room and pick up two-thirds of the air volume, whereas the final third is taken from near the ceiling, which guarantees an optimal perfusion of the operating room with a sterile filtered air supply. However, this setup is also employed because anesthetic gases have a higher molecular weight than the components of air and should pool on the floor if movement is kept to a minimum and if a ventilation system with a unidirectional displacement flow is employed. However, this anticipated pooling of volatile anesthetics at the floor level has never been proven. Thus, we herein investigated the flow behaviors of isoflurane, sevoflurane, and carbon dioxide (for comparison) in a measuring chamber sized 2.46 × 1.85 × 5.40 m with a velocity of 0.3 m/sec and a degree of turbulence <20%. Gas concentrations were measured at 1,728 measuring positions throughout the measuring chamber, and the flow behaviors of isoflurane and sevoflurane were found to be similar, with an overlap of 90%. The largest spread of both gases was 55 cm at 5.4 m from the emission source. Interestingly, neither isoflurane nor sevoflurane was detected at floor level, but a continuous cone-like spreading was observed due to gravity. In contrast, carbon dioxide accumulated at floor level in the form of a gas cloud. Thus, floor level exhaust ventilation systems are likely unsuitable for the collection and removal of anesthetic gases from operating rooms.

On the bio-accessibility of 14 elements in welding fumes.

The bio-accessibility of 14 elements in welding fume particulate matter was investigated in 325 personal air samples collected during welding in two shipyards and one factory producing heavy machinery. The apparent solubility in a synthetic lung lining fluid (Hatch's solution) was used as proxy for the bio-accessibility. The Hatch solubility of the different elements was highly variable with a median < 1% for Al, Fe, Pb, Ti, between 4 and 6% for Co, Cr, Ni, V, W, between 13 and 27% for Cd, Cu, Mn, Zn, and 41% for Mo. For many elements, the solubility varied over a wide range of several tens of percent. The welding techniques used influenced the solubility of Co, Cr, Cu, Mn and V significantly. The plants investigated (i.e., the welded materials and used electrodes) had a significant influence on the solubility of Co, Cr, Cu, Mn, Mo, V and W. According to principal component analysis (PCA), the variation in solubility can be described by four components, which explain 69% of the variance. The first principal component mostly comprises elements that can predominantly occur as divalent cations, the second principal component elements often forming oxyanions. The principal components are independent of the absolute value of the Hatch solubility. The results of PCA indicate that the co-variation of Hatch solubility is mainly controlled by the most soluble compounds in contrast to the absolute value of apparent solubility, which is strongly influenced by the distribution of the elements between compounds with different equilibrium solubilities. The observed large variability and the significant differences between welding techniques and plants clearly show that the bio-accessibility cannot be obtained from the literature but has to be studied experimentally at each location of interest.

Bacterial peroxidase-mediated enhanced biodegradation and mineralization of bisphenol A in a batch bioreactor.

The present study focused on the enhanced biodegradation and mineralization of bisphenol A (BPA) as a toxic endocrine disrupting compound using peroxidase-mediated bioprocess under H2O2-infusion. The complete biodegradation of 100 mg/L BPA was achieved within 54 h reaction time at the optimum H2O2:BPA molar ratio of 10. BPA concentrations up to 100 mg/L had no inhibitory effect on the bacterial biomass at which a dehydrogenase activity of 9.1 µg TF/gbiomass and a peroxidase activity of 1.4 U/mL was obtained. The increase in biomass concentration from 90 to 450 mg/L improved the BPA biodegradation from 70.3% to 97.8% and its mineralization from 11.5% to 71.2% at the reaction time of 36 h. The highest BPA biodegradation rate was found to be 10.8 mg BPA/gbiomass. h. Accordingly, infusing H2O2 into the bioreactor stimulated the bacteria to produce peroxidase and allowed peroxidase-mediated enhanced biodegradation of BPA.

Respiratory effects of occupational exposure to low concentration of hydrochloric acid among exposed workers: a case study in steel industry.

Occupational exposure to hydrochloric acid in pickling of steel for remove rust or iron oxide scale from iron processing occurs at low concentration. This study aimed to investigate the respiratory symptoms and pulmonary dysfunction caused by exposure to low concentration of hydrochloric acid in acid washing unit in one of the steel industries. A case control study was carried out in the acid washing unit of the cold rolling of the steel industry in 2017. The exposed group included 45 male workers, and another 41 unexposed employees from official employees were enrolled as control group. A questionnaire was used to collect personal and occupational data and pulmonary function tests, including forced vital capacity (FVC), forced expiratory volume in the first second and peak expiratory flow rate followed guidelines given by the American Thoracic Society and measured with a portable calibrated vitalograph spirometer. For determination of acid concentration, 21 breathing zone air samples were collected in accordance with Method 7903 NIOSH. The findings showed that nose sensitivity, throat irritation and shortness of breath were the highest prevalence symptoms among exposed persons (30.4% to 32.6%). Also, the results showed that FVC and forced expiratory volume in the first second had highest and direct or positive correlation with height (0.965 and 0.927, respectively). Age and weight put in the next priorities (P < 0.01). On the other hand, based on the results of multivariate linear regression, exposing to the acid and job history are two main predictor factors for FVC. So that, the exposing to acid, by itself can reduce FVC as 4.386 units. This value is equal to 1.117 for the job history. Exposure to low concentrations of hydrochloric acid alone could increase the risk of respiratory tract damage and pulmonary function disorders. But the extent to which it can cause respiratory complications for occupational exposure is still unknown and requires further study. This study was approved by Ethical Committee of Qom University of Medical Sciences (approval No. IR.MUQ.REC.1397.118) on November 6, 2018.