Fluoride Exposure and Respiratory Symptoms in Welders

Sodium fluoride activates the extrinsic apoptosis via regulating NOX4/ROS-mediated p53/DR5 signaling pathway in lung cells both in vitro and in vivo

An extensive body of research has demonstrated that pulmonary toxicity induced by fluoride is related to cell apoptosis. Although induction of death receptor-initiated extrinsic apoptosis by sodium fluoride (NaF) has been reported, its mechanism of action is still not clearly defined. Herein, we found that NaF treatment induced activation of caspase-8 in BEAS-2B cells, resulting in apoptosis, which was markedly reduced by blocking caspase-8 using small interfering RNA (siRNA). In this study, we report that death receptor 5 (DR5), a major component of the extrinsic apoptotic pathway, is markedly induced upon NaF stimulation. Enhanced DR5 induction was necessary for the apoptotic effects of NaF, inasmuch as transfected BEAS-2B cells with DR5 siRNA attenuated NaF-induced caspase-8 activation in lung cells. Mechanism investigation indicated that the induction of DR5, following NaF exposure, was mediated by tumor protein 53 (p53)-dependent transcriptional activation. Notably, we demonstrated that NaF could induce a significant increase in intracellular reactive oxygen species (ROS) level derived from nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4). Specifically, NOX4 knockdown inhibited NaF-induced the activation of p53/DR5 axis by reducing NOX4-derived ROS production. Further in vivo investigation demonstrated that NOX4 deficiency markedly attenuates NaF-induced lung injury, apoptosis, and ROS levels in the lung. Moreover, the expressions of p53 and DR5 were significantly reduced after NaF treatment in NOX4 knockout mice compared with the wild type mice. Taken together, our findings provide a novel insight into for the pulmonary apoptosis in response to NaF exposure.

Pulmonary fluorosis: a review

The increased industrialization and improvised human lifestyle lead to a surge in environmental pollution nowadays. Even the chemicals which are known as prophylactic agents were currently liable to be toxic. One among them is inorganic fluoride whose wider application in numerous processes makes it as an inevitable environmental contaminant and industrial pollutant. Although the systemic toxicity of fluoride has been extensively studied, still there is lacuna in the field of pulmonary fluoride toxicity. Hence, we have focused on the molecular mechanism of action of fluoride compounds on pulmonary system. A study of literatures that focused on the potential physiological and toxicological consequences of fluoride on pulmonary system was carried out. The goal of this review is to present an overview of the research carried out till date on the molecular aspects of fluoride exposure with emphasis on pulmonary system and their possible mechanisms.

Tamarind seed coat ameliorates fluoride induced cytotoxicity, oxidative stress, mitochondrial dysfunction and apoptosis in A549 cells

Fluoride (F) is an environmental contaminant and industrial pollutant. Molecular mechanisms remain unclear in F induced pulmonary toxicity even after numerous studies. Tamarind fruits act as defluoridating agents, but no study was conducted in in vitro systems. Hence, we aimed to assess the ameliorative impact of the tamarind seed coat extract (TSCE) against F toxicity utilizing lung epithelial cells, A549. Cells were exposed to sodium fluoride (NaF-5 mM) alone and in combination with TSCE (750 ng/ml) or Vitamin C (positive control) for 24 h and analyzed for F content, intracellular calcium ([Ca(2+)]i) level, oxidative stress, mitochondrial integrity and apoptotic markers. TSCE treatment prevented the F induced alterations in [Ca(2+)]i overload, F content, oxidant (reactive oxygen species generation, lipid peroxidation, protein carbonyl content and nitric oxide) and antioxidant (superoxide dismutase, catalase, glutathione peroxidase and glutathione) parameters. Further, TSCE modulates F activated changes in mitochondrial membrane potential, permeability transition pore opening, cytochrome-C release, Bax/Bcl-2 ratio, caspase-3 and PARP-1 expressions. In conclusion, our study demonstrated that TSCE as a potential protective agent against F toxicity, which can be utilized as a neutraceutical.

Assessment of the biological effects of welding fumes emitted from metal inert gas welding processes of aluminium and zinc-plated materials in humans

The aim of this study was to investigate biological effects and potential health risks due to two different metal-inert-gas (MIG) welding fumes (MIG welding of aluminium and MIG soldering of zinc coated steel) in healthy humans. In a threefold cross-over design study 12 male subjects were exposed to three different exposure scenarios. Exposures were performed under controlled conditions in the Aachener Workplace Simulation Laboratory (AWSL). On three different days the subjects were either exposed to filtered ambient air, to welding fumes from MIG welding of aluminium, or to fumes from MIG soldering of zinc coated materials. Exposure was performed for 6 h and the average fume concentration was 2.5 mg m(-3). Before, directly after, 1 day after, and 7 days after exposure spirometric and impulse oscillometric measurements were performed, exhaled breath condensate (EBC) was collected and blood samples were taken and analyzed for inflammatory markers. During MIG welding of aluminium high ozone concentrations (up to 250 μg m(-3)) were observed, whereas ozone was negligible for MIG soldering. For MIG soldering, concentrations of high-sensitivity CRP (hsCRP) and factor VIII were significantly increased but remained mostly within the normal range. The concentration of neutrophils increased in tendency. For MIG welding of aluminium, the lung function showed significant decreases in Peak Expiratory Flow (PEF) and Mean Expiratory Flow at 75% vital capacity (MEF 75) 7 days after exposure. The concentration of ristocetin cofactor was increased. The observed increase of hsCRP during MIG-soldering can be understood as an indicator for asymptomatic systemic inflammation probably due to zinc (zinc concentration 1.5 mg m(-3)). The change in lung function observed after MIG welding of aluminium may be attributed to ozone inhalation, although the late response (7 days after exposure) is surprising.

Personal exposure to metal fume, NO2, and O3 among production welders and non-welders

The objective of this study was to characterize personal exposures to welding-related metals and gases for production welders and non-welders in a large manufacturing facility. Welding fume metals and irritant gases nitrogen dioxide (NO(2)) and ozone (O(3)) were sampled for thirty-eight workers. Personal exposure air samples for welding fume metals were collected on 37 mm open face cassettes and nitrogen dioxide and ozone exposure samples were collected with diffusive passive samplers. Samples were analyzed for metals using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and welding fume metal exposure concentrations were defined as the sum of welding-related metals mass per volume of air sampled. Welding fume metal exposures were highly variable among similar types of welding while NO(2) and O(3) exposure were less variable. Welding fume metal exposures were significantly higher 474 μg/m(3) for welders than non-welders 60 μg/m(3) (p=0.001). Welders were exposed to higher concentrations of NO(2) and O(3) than non-welders but the differences were not statistically significant. Welding fume metal exposure concentrations for welders performing gas metal arc welding (GMAW) and shielded metal arc welding (SMAW) were higher than welders performing gas tungsten arc welding (GTAW). Non-welders experienced exposures similar to GTAW welders despite a curtain wall barrier separating welding and non-welding work areas.

Evaluation of alveolar clearance by Tc-99m DTPA radioaerosol inhalation scintigraphy in welders

OBJECTIVES

The welding process produces metal fumes and gases which may affect respiratory health. Technetium-99m diethylenetriaminepentaacetic acid (Tc-99m DTPA) dynamic lung scanning is an easy, noninvasive method to assess disorders of alveolar-capillary barrier permeability secondary to epithelial damage. We aimed to investigate the alveolar clearance by Tc-99m DTPA radioaerosol inhalation scintigraphy in welders, to assess additive effects of exposure to welding fumes and cigarette smoking on clearance rate of alveolar epithelium and to determine the correlation between Tc-99m DTPA aerosol lung scintigraphy and spirometric measurements.

METHODS

Nine nonsmoking welders, 9 smoking welders, and a control group of 6 nonsmokers and 6 smokers were accepted to the study. Tc-99m DTPA radioaerosol inhalation scintigraphy was performed in all subjects. Clearance half time (Tl/2) was calculated by placing a monoexponential fit on the curves. Penetration index (PI) was also calculated on the first minute image. Pulmonary function tests of welders and control group were compared.

RESULTS

The mean T1/2 values of Tc-99m DTPA of the nonsmoking welders were significantly higher than those of the nonsmoking control group (82.1+/-24.3 min and 48.1+/-9.7 min, respectively; p = 0.003). The mean T1/2 values of Tc-99m DTPA of the smoking welders were higher than those of the smoking control group (53.3+/-24.5 min and 44.5+/-9.7 min, respectively; p = 0.510). PI of the nonsmoking welders was significantly higher than that of the nonsmoking control group (0.46+/-0.38 and 0.39+/-0.46 respectively; p = 0.004). PI of the smoking welders was significantly higher than that of smoking control group (0.43+/-0.38 and 0.37+/-0.45, respectively; p = 0.019). There was a negative correlation between T1/2 value and FEV1% (r = -0.468, p = 0.016), FVC% (r = -0.442, p = 0.024) and FEF25-75% (r = -0.391, p = 0.048) in the welders and control group. No statistically significant differences were found in the values of the standard pulmonary function tests of any of the subjects.

CONCLUSIONS

Welding seems to decrease alveolar clearance which causes an increase in the penetration index. This was considered to be due to fibrotic changes and increased number of alveolar macrophages induced by welding fumes.