Noise and silver nanoparticles induce hepatotoxicity via CYP450/NF-Kappa B 2 and p53 signaling pathways in a rat model.

Co-exposure to noise and nanomaterials, such as silver nanoparticles (Silver-NPs), is a common occurrence in today's industries. This study aimed to investigate the effects of exposure to noise and the administration of silver-NPs on the liver tissue of rats. Thirty-six adult male albino Wistar rats were randomly divided into six groups: a control group (administered saline intraperitoneally), two groups administered different doses of Silver-NPs (50 mg/kg and 100 mg/kg, 5 days a week for 28 days), two groups exposed to noise in addition to Silver-NPs (at the same doses as mentioned before), and a group exposed only to noise (104 dB, 6 hours a day, 5 days a week for 4 weeks). Blood samples were taken to assess hepatic-functional alterations, such as serum ALP, ALT, and AST levels. Additionally, biochemical parameters (MDA, GPX, and CAT) and the silver concentration in the liver were measured. Histopathological analysis, mRNA expression (P53 and NF-κB), protein expression (CYP450), and liver weight changes in rats were also documented. The study found that the administration of Silver-NPs and exposure to noise resulted in elevated levels of ALP, ALT, AST, and MDA (p < .01). Conversely, GPX and CAT levels decreased in all groups compared with the control group (p < .0001). There was a significant increase (p < .05) in liver weight and silver concentration in the liver tissues of groups administered Silver-NPs (50 mg/kg) plus noise exposure, Silver-NPs (100 mg/kg), and Silver-NPs (100 mg/kg) plus noise exposure, respectively. The expression rate of P53, NF-κB, and cytochromes P450 (CYPs-450) was increased in the experimental groups (p < .05). These findings were further confirmed by histopathological changes. In conclusion, this study demonstrated that exposure to noise and the administration of Silver-NPs exacerbated liver damage by increasing protein and gene expression, causing hepatic necrosis, altering biochemical parameters, and affecting liver weight.

Validation of a temperature-humidity index (Humidex) in evaluating heat stress at a tile factory in Iran.

BACKGROUND: Several heat indices have been developed in industrial health, but each has its limitations. OBJECTIVE: The objective of this article is to determine the validity and applicability of a temperature-humidity index, named Humidex compared with the Standard Wet-Bulb Globe Temperature (WBGT) index (ISO 7243). METHOD: This cross-sectional study was conducted in the summer of 2019, in a tile factory in the west of Iran. 59 measurements were performed in 8 different workstations. Environmental parameters including natural wet bulb temperature (Tnw), dry bulb temperature (Ta), globe bulb temperature (Tg), and heat stress (WBGT) were measured. Humidex was calculated according to an equation. SPSS software (version 16) was used for data analysis. RESULTS: There was a high correlation between Humidex and WBGT in the estimation of heat stress (R=0.912, P<0.001). The Kappa Coefficient between Humidex and WBGT was 0.298, P=0.001. CONCLUSION: Humidex is highly correlated with WBGT. Humidex can be used instead of the WBGT index, especially in hot and humid environments.

Association of prolonged occupational co-exposures to electromagnetic fields, noise, and rotating shift work with thyroid hormone levels.

The purpose of this study was to determine the association of prolonged occupational co-exposure to extremely low-frequency electromagnetic fields (ELF-EMFs), noise, and rotating shift work with the levels of thyroid hormones (triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH). From 2016 to 2017, we enrolled all male workers without a history of thyroid disorders and followed them until 2020. To measure ELF-EMFs and noise exposures, we calculated the 8-hour equivalent sound pressure levels (Leq) and the 8-hour average of ELF-EMFs, respectively. Shift work schedules involved 8-hr fixed day and 8-hr clockwise 3-rotating night schedules. The participant's thyroid hormone levels were obtained from blood test results in their medical records. The percentage change in the levels of T3, T4, and TSH was estimated by using different mixed-effects linear regression models. The TSH levels were significantly elevated per a 10-dB increment of noise. The levels of T4 hormone were significantly changed per a unit increase in the levels of ELF-EMFs. Compared to the fixed-day workers, we observed workers exposed to shift work had a significantly lower T4 level. For T4 and TSH hormones, we found significant interactions among noise, ELF-EMFs, and shift work variables. In summary, this study warranted that prolonged exposure to ELF-EMFs, noise, and rotating shift work might be associated with thyroid dysfunction.

Association between Simultaneous Occurrence of Occupational Noise-Induced Hearing Loss and Noise-Induced Vestibular Dysfunction: A Systematic Review.

Background: Background: Because of functional and structural similarities between the cochlea and vestibular sensory receptors, vestibular dysfunction could be accompanied by noise-induced hearing loss (NIHL) due to occupational noise exposure. We aimed to evaluate the occurrence of vestibular dysfunction (VD) in individuals with NIHL and occupational noise exposure. Methods: A systematic literature research was carried out within the databases of PubMed, Scopus, Science Direct, and Web of Science for published articles between 1980 and Jan 5, 2023 using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The methodological quality of the included systematic reviews was assessed with the Joanna Briggs Institute (JBI) checklist. Vestibular system dysfunction parameters were considered as primary outcomes in subjects with NIHL. Results: We reviewed the evidence (from 19 eligible articles) for VD from noise-induced damage to peripheral vestibular structures. VD can occur after occupational noise exposure or concomitantly with NIHL. Furthermore, this study showed that the saccular organ has a higher susceptibility to noise damage than the vestibular organs of the utricle and semicircular canals (SCCs). Conclusion: Our results support the role of occupational noise exposure and NIHL as risk factors for developing VD. Further research is needed to investigate the association between the occurrence of VD due to occupational noise exposure or concomitantly with NIHL.

Independent, modified, and interacting effects of long-term noise, extremely low-frequency electromagnetic fields, and shift work exposures on liver enzymes.

To quantify long-term independent, modified, and interacting effects of noise, extremely low-frequency electromagnetic fields (ELF-EMFs), and shift work exposures on liver enzymes, a four-year repeated measures study was performed among male workers in a thermal power plant industry from 2016 to 2020. The 8-h equivalent sound pressure levels (Leq) were measured at weighting channels of Z, A, and C for octave-band frequencies. The 8-h time-weighted average of ELF-EMFs levels was measured for each participant. Shift work schedule was determined based on job titles, including 3-rotating night shift work and fixed day shift work schedules. The fasting blood samples were taken to determine liver enzymes (AST, Aspartate transaminase; ALT, Alanine transaminase). The percentage change (PC) and 95% confidence interval (CI) of AST and ALT enzymes were estimated by the different bootstrapped-mixed-effects linear regression models. Per 10-dB noise increase, we found a significantly higher PC (95% CI) of AST and ALT (only LAeq) levels in all regression models with the highest changes for LAeq. For the octave-band noise analysis, there was an upward trend from 31.5 Hz to 1 kHz frequencies and a downward trend from 1 to 8 kHz frequencies. Per 1 mG ELF-EMFs increase, we observed a significantly higher PC (95% CI) of AST and ALT enzymes in the main adjusted and the main adjusted + shift work models. The 3-rotating night than fixed day shift workers had a significant PC in the unadjusted model for AST enzyme and the fully adjusted and the main adjusted + ELF-EMFs models for ALT enzyme. Significant negative two-way or/and three-way interaction effects among the noise, ELF-EMFs, and shift work were observed for both AST and ALT enzymes. Our findings indicated long-term noise, ELF-EMFs, and 3-rotating night shift work exposures may be significantly associated with changes in the levels of liver enzymes.

The combined effects of noise and vibration stress on sex hormone levels, fertility capacity, and the protective role of cinnamon extract in rats: an experimental study.

Due to the high prevalence of noise and vibration exposure in most industries, this study aimed to investigate the effects of simultaneous exposure to noise and vibration on sex hormone levels and fertility capacity in rats, as well as the protective effects of the hydroalcoholic extract of cinnamon. In this experimental study, 64 adult male rats were randomly divided into 8 groups, control, noise (N), cinnamon (C), noise + cinnamon (NC), vibration (V), vibration + cinnamon (VC), noise + vibration (NV) and groups Noise + Vibration + Cinnamon (NVC). Groups C, NC, VC and NVC received a 75 mg/kg dose of cinnamon extract by gavage. The rats of groups N and NC, V and VC and NV and NVC were each exposed to noise at 100 dB (700-5700 Hz), vibration acceleration of 1 m/s2 rms (frequency range of 4-8 Hz), and simultaneously exposed to vibration and noise for 8 hours continuously every night (23:00-7:00) for 50 consecutive nights. Next, a blood sample was taken from the lateral tail vein and the levels of LH, FSH and testosterone were measured with ELISA kits. Each male rat was caged with 3 female rats for one week. The pregnant rats were kept until all of the rat pups were born. Then the fertility capacity, the total number of births, the live births and the birth weight of the rat pups were analyzed with the software SPSS. In the N and NV groups, compared to the control group, a significant decrease in LH and testosterone levels, the number of births and the birth weight was observed (p < 0.05). A significant decrease in testosterone levels, number of births and birth weight was observed in Group V compared to the control group (p < 0.05). In addition, significant increases in LH, FSH and testosterone levels and in birth weight were observed in group C compared to the control group (p < 0.05). Significant increases in FSH and testosterone levels, birth weight, and the number of births were noted in the NVC group compared to the NV group (p < 0.05). Based on the results of this study, cinnamon extract could alleviate the destructive effects of noise and vibration (both individually and in combination) on levels of sex hormones (LH, FSH, and testosterone), the number of births, and birth weight.

The long-term effects of exposure to noise on the levels of thyroid hormones: A four-year repeated measures study.

Animal studies have suggested that noise exposure can be associated with changes in the levels of thyroid hormones. However, no evidence is available that quantified this effect on humans. This study aimed to quantify the long-term effects of exposure to noise and its different frequencies on thyroid hormone levels. A four-year repeated measures study was performed among male workers of a thermal power plant industry from 2016 to 2020. Overall, 1032 observations were examined. To determine exposure to noise for each participant, the 8-hour equivalent sound pressure levels (Leq) were measured at weighting channels of Z, A, and C for an octave-band including low (31.5, 63, 125 Hz), middle (250,500, and 1000 Hz), and high (2, 4, 8 kHz) frequency noises. The fasting blood samples were also taken to determine thyroid hormone levels (TSH, Thyroid-stimulating hormone; T4, Thyroxine; T3, Triiodothyronine). The mixed-effects linear regression was applied to specify the percent changes in the levels of thyroid hormones. The prevent changes (95% confidence interval) of T4, T3, and TSH levels per a 10-dB increase in Leq based on the full adjusted model were estimated -0.90 (-1.68, -0.11), -0.70 (-1.44, 0.05), and 3.94 (0.58, 7.40), respectively. The highest percent changes in the T4 and TSH hormones were identified at 500 Hz (percent change = -1.08 and 95% CI = -1.93, -0.23) and with little difference at 1 (percent change = 4.73 and 95% CI = 0.91, 8.70) and 2 kHz (percent change = 4.72 and 95% CI = 1.13, 8.52) frequencies, correspondingly. Our findings indicated that long-term noise exposure may be associated with changes in the levels of thyroid hormones. Although more studies are warranted, noise-induced thyroid dysfunction may play a significant role in the biological pathways of the effects of noise on the human body.

Weighing and modelling factors influencing serum cortisol and melatonin concentration among workers that are exposed to various sound pressure levels using neural network algorithm: An empirical study.

BACKGROUND: Noise is one of the most common harmful agents in the workplace. Exposure to excessive noise can lead to complications such as cardiovascular disorders, disturbance of body hormones' rhythm and hearing loss. This study aimed at weighing and modelling factors influencing serum cortisol and melatonin concentrations of workers that are exposed to various sound pressure levels using neural network algorithm. METHODOLOGY: A case-control design was adopted in the current research. The required data were collected from 75 industrial and mining firm staff members. They were assigned to three groups with equal sample sizes (25 workers). In developing the conceptual model in regard to variables that may affect workers' serum cortisol and melatonin concentration, SPL, age, weight, and height were included. The influence of SPL on serum cortisol concentration as assessed in the three shifts. Moreover, radioimmunoassay (RIA) was utilized to assess serum cortisol and melatonin concentrations. Neural network algorithm was subsequently exploited to weigh and model predictor factors. IBM SPSS Modeler 18.0 was the software program used for data analysis. RESULTS: The average cortisol concentration values for administrative, condensing, and pelletizing units respectively were 10.24 ± 2.35, 12.15 ± 3.46, and 14.91 ± 4.16 µ g d l . On the other hand, the average melatonin concentration values for administrative, condensing, and pelletizing units respectively were 37 ± 12.52, 34 ± 13.15, and 27 ± 9.54 µ g d l . According to the results of the developed model for cortisol, SPL3 (32%) and age (5%) respectively had the highest and lowest impact. On the other hand, considering the model developed for melatonin, height (27%) and SPL1 (10%) were the most and least influential factors in that order. The accuracy rates of the model were also found to be 95% for cortisol and 97% for melatonin. CONCLUSION: Comparing cortisol concentrations during various shifts revealed a significant reduction (from the beginning to the end of the shift) in all the three groups. Further, the rise of SPL would result in higher secretion of cortisol. Moreover, in all the three groups, the average serum melatonin concentration went up from the beginning to the middle of the shift and then declined to the end of the shift. Considering the accuracy rates of the models developed to predict hormones, neural network algorithm is a suitable and powerful tool for weighing and modelling factors influencing serum cortisol and melatonin concentrations.

Neuroanatomical changes of the medial prefrontal cortex of male pups of Wistar rat after prenatal and postnatal noise stress.

Recent evidences showed that, noise stress causes abnormal changes in structure and function of central nervous system (CNS). The Current study was conducted to evaluate some stereological parameters of the medial prefrontal cortex (mPFC) of male pups of Wistar rat after prenatal and early postnatal noise stress. 18 pregnant Wistar rats were randomly divided into prenatal noise-exposed (NE) group, postnatal NE group, and controls. Male pups of NE groups were exposed to noise 100 dB at the frequency ranges of 500-8000 Hz, 4 h per day from gestational day one (GD1) to GD21 for the prenatal NE group, and from postnatal day one (PND1) to PND21 in the postnatal NE group. The Control group animals were maintained under standard condition without noise stimulation. Corticosterone level in plasma was measured using ELISA technique. Changes of the neurons and non-neurons cells number and volume of the mPFC were evaluated by stereological analysis. Tunnel assay was also used for detection of apoptotic cells. Increase in plasma corticosterone level, decrease in the number of neurons, and increase in the apoptotic cells number were observed in both NE groups. Decrease in volume of mPFC and also in non-neurons cells number was observed in the prenatal NE group. An increase in the non-neurons number was seen in the postnatal NE group. Data of the current comparative study showed that, noise stress during prenatal and early postnatal periods can induce the abnormal alteration in some stereological parameters of mPFC in male pups of Wistar rat. These negative alterations were more remarkable after prenatal noise stress.