Development of a personal heat strain risk assessment (PHSRA) index in workplaces and its validation

Validity of ten analytical heat stress indices in predicting the physiological parameters of people under various occupational and meteorological conditions

Until now, only a few comprehensive studies have validated analytical heat stress indices in different conditions. The present study aims to investigate the validity of these indicators in predicting the physiological parameters of workers. This cross-sectional study was conducted with 194 male employees working in warm environments. First, demographic information was collected. After participants rested for 30 min, their heart rate and tympanic temperature were measured. The subjects then performed their routine tasks. At the end of 90 min, their heart rate and tympanic temperature were again measured. Additionally, their metabolism rate and clothing thermal insulation were estimated. Environmental parameters were also measured at 30-, 60-, and 90-min time points. Additional information required to compute the indices was recorded. Then, the values of each of the indices were computed. Finally, the validity of the indices was assessed under different conditions. The results indicated that the highest regression coefficients with tympanic temperature were assigned to modified physiologically equivalent temperature (mPET) (0.7515), predicted heat strain (PHS) (0.7201), and predicted mean vote (PMV) (0.7082), index, respectively. Also, the greatest regression coefficients with heart rate belonged to mPET (0.7773), PMV (0.7624), and PHS (0.6479) index, respectively. Based on the results, the highest diagnostic accuracies of receiver operating characteristic (ROC) curves for tympanic temperature were related to indices of mPET, PHS, and PMV with the area under the ROC curve (AUC) of 0.945, 0.931, and 0.930, respectively. Of the studied indices, it was observed that mPET, PHS, PMV, and PPD showed more validity compared to others.

Providing an approach to analyze the risk of central oxygen tanks in hospitals during the COVID-19 pandemic

The central oxygen unit of hospitals is considered a high-risk unit, requiring high safety standards to maintain the integrity of the system during the COVID-19 pandemic. The linear reasoning assumption of conventional risk analysis methods cannot adequately describe these modern systems, which are characterized by tight connections and complex interactions between technical, human, and organizational aspects. Therefore, this study presents a new and comprehensive approach to oxygen tanks in hospitals during the COVID-19 pandemic. In this study, trapezoidal fuzzy numbers were used to calculate failure rates. After determining the probability of basic events (BEs), intermediate events (IE), and top event (TE) with fuzzy logic and transferring it into Bayesian Network (BN), deductive and inductive reasoning, and sensitivity analysis were performed using RoV in GeNIe software. The results of the case study showed that the IE of "Human Error" had the highest probability of fuzzy fault tree (FFT) and the probability of oxygen leakage was lower using FBN than FFT. According to the results, BE16 (failure to use standard and updated instructions) and BE12 (defects in the inspection and testing program of tank devices) had the highest posterior probability, while based on the FFT results, BE4 (defects in the external coating system of the tank) and, BE3 (Corrosive environment (acidity state)) had the least probability. According to the sensitivity analysis, basic events 10, 11, and 16 were the most important in the oxygen leakage event with a very small difference, which was almost in line with the results of posterior FBN (FBNPO). Updating the existing guidelines, fixing defects in the inspection of all types of tank gauges, and testing related equipment can greatly help the reliability of these tanks. Root cause analysis of these events provides opportunities for prevention and emergency response in critical situations, such as the COVID-19 pandemic.

Health risk assessment of exposure to ambient formaldehyde in carpet manufacturing industries

Formaldehyde is categorized as a definitive carcinogen by the International Agency for Research on Cancer. To the best of our knowledge, no study has assessed the health risks of occupational exposure of workers in carpet manufacturing plants to formaldehyde. Therefore, this study assesses the health risks of the occupational exposure to formaldehyde of 67 male workers in carpet manufacturing plants in Iran in 2022. Exposure to formaldehyde was quantitatively determined after collecting personal exposure samples from the workers' respiratory zone and spectrophotometric analysis based on method number 3500 of the National Institute of Occupational Safety and Health. In the next step, the carcinogenic and noncarcinogenic risks based on personal exposure to formaldehyde were evaluated. Sensitivity analyses were employed using the Monte Carlo simulation method. The mean inhalation exposure of workers to formaldehyde was 0.636 mg m^-3. The inhalation cancer risk value based on the integrated risk information system for formaldehyde was 4.06×10^-4 ± 3.17×10^-5 (mean ± standard deviation), which exceeded the value reported by the US Environmental Protection Agency. An unacceptable carcinogenic risk level was found in 75.6% of workers. The highest mean inhalation cancer risk was 6.74×10^-4 (i.e., 6.74 additional cases per 10,000 employees exposed) was found in sizing post employees. The hazard quotient of formaldehyde was 0.311±0.024. The formaldehyde concentration had a considerable effect on the health risk. The findings of this study provide valuable scientific information that supports the development of future policies to enhance the health status of employees in carpet manufacturing plants.

Development of an observational - perceptual heat strain risk assessment (OPHSRA) index and its validation

BACKGROUND

The thermal strain can be measured using subjective methods without the use of sensitive equipment. The purpose of the present study was the development and validation of an observational - perceptual heat strain risk assessment (OPHSRA) method.

METHODS

This cross-sectional study, in 2019, was performed. At first, an observational-perceptual questionnaire was designed using effective items in producing heat strain. Then, the reliability and validity of the questionnaire were examined. Later, 201 male workers were asked to perform the routine tasks for 90 min under various climatic conditions after resting in a cool room. At the end of the activity, the tympanic temperature of the subjects was accurately measured. Also, the designed questionnaire was completed by researchers and participants. Then, the effect coefficients of the items were calculated and used for developing the novel index. At final, the index validity was investigated.

RESULTS

The values of the content validity ratio (CVR), content validity index (CVI), and Cronbach's coefficient alpha (α) of the designed questionnaire with 16 questions were equal to 0.793, 0.913, and 0.910, respectively. The results indicated that environmental, job, administrative, and clothing items assessed by the questionnaire with the coefficients of 0.860, 0.658, 0.783, and 0.566 had significant effects on the thermal strain, respectively. These coefficients were exploited to develop the index. The result revealed that the OPHSRA index justified 69% of the variations of the tympanic temperature (R² = 0.69).

CONCLUSION

The novel index developed by the questionnaire had an acceptable validity. Therefore, this index can be used for estimating the risk of thermal strain in a variety of thermal conditions.