[Study of development of public health safety literacy scale in China]

Objective: To develop a suitable scale for assessing the public health safety literacy in residents in China. Methods: The initial scale of Chinese public health safety literacy was developed through theoretical conceptualization, item pooling, field verifying and item inclusion and exclusion. Then the initial scale was converted into an electronic questionnaire. A total of 2 809 residents from 4 provinces were randomly selected for field testing. Classical test theory (CTT) and item response theory (IRT) were used for item reduction. SPSS 23.0 was used for exploratory factor analysis (EFA) and unidimensional testing. Package R 4.1.1 ltm and mirt were used for the analysis of the psychometric properties of items and generate the ICC, IIC and TIF. Results: The initial scale had 30 items (B1-B30), and the test took 9.8 s to complete one item averagely. According to the CTT, B2 was deleted due to coefficient of total correlation (CITC) <0.3 and the item-dimension correlation coefficient (IDCC) <0.4. B23 was deleted due to CITC<0.3, IDCC<0.4 and difficulty index (W) <0.2. B30 was deleted due to CITC<0.3 and W<0.2. The total Cronbach's α of the scale was 0.923 after deletion. EFA indicated that 14 items should be deleted due to lower factor loadings <0.7. EFA was conducted for remaining 13 items and 2 common factors were extracted, the factor loadings of all items were >0.7, the accumulated variance contribution of the 2 common factors was 63.361%, and the total Cronbach's α was 0.891, showing unidimensionality, IRT was used to test the remaining items. B14 and B20 were deleted due to discrimination coefficient (a) <0.3, difficulty threshold coefficient (b) ∉[-3,3], the small amount of information and the flat, crowded, non-monotonic ICC, and IIC. Finally, the Cronbach's α of the 11-itemed scale was 0.936 with TLI=0.97, CFI=0.99, and RMSEA=0.03. Conclusion: The final scale has good reliability, validity, discrimination, difficulty level and feasibility, and can be applied for the rapid assessment of public health safety literacy in China.

[Preliminary study of a mask filtration test device with respiratory simulation]

Objective: To develop an air particulate protective mask filter test device that can simulate the dynamics process of human breathing. Methods: The new device used two air pumps working alternately to simulate the dynamics process of human breathing. On March 4th to 17th, 2017, the new device and the traditional one-way airflow mask filtration test device were used to measure the internal and external particle levels of 39 masks of 13 models of 6 brands, and then the filtration efficiency of the mask was calculated and the test results were compared. Results: For the mask without breathing valve, there was no statistically significant difference between the filter efficiency test results of the new device and the traditional unidirectional airflow filter performance test device (P>0.05) . For masks with breathing valves, the new device detected that three of them had lower filtration efficiency (99.50% vs 98.63%, P<0.01) . After sealing the mask breathing valve with glue, the filtering efficiency of the mask with a breathing valve detected by the new device significantly improved (98.63% vs 99.50%, P<0.01) . Conclusion: This new device can simulate the dynamic process of human exhalation and inhalation, and measure the filtration efficiency of the mask. For masks with breathing valves, the new device makes it easier to detect the decrease in the filtering efficiency of the mask caused by the breathing valve.

[Performance evaluation of two N95 filtering-facepiece respirators on decomposition products of sulfur hexafluoride]

OBJECTIVE

To assess the filtration efficiency of two N95 filtering-facepiece respirators (FFRs) for the decomposition products of sulfur hexafluoride (SF6).

METHODS

Two types of N95 FFRs (the particulate and the acid-proof respirators) were selected in this study. The decomposition products of SF6, including particles, hydrogen fluoride (HF) and sulfur dioxide (SO2) , were measured under experimental condition by using TSI PortaCount Plus, fluorine ion-selective electrodes and spectrophotometer separately. The filtration efficiency was then calculated and compared.

RESULTS

Both two models of N95 respirators had lowest filtration efficiency larger than 95% for particles under airflow ranged from 10 to 95 L/min. When exposed to different concentrations of HF (low: 0.00~1.99 mg/m(3), middle: 2.00~3.99 mg/m(3), high: >4 mg/m(3)) , the acid-proof N95 respirator was more effective than the particulate respirator (P<0.05) with a filtration efficiency of 98.83%, 99.08%, and 99.03% versus 48.44%, 45.71%, and 47.31%. For four SO2 concentration ranges (0.00~2.49 mg/m(3), 2.50~4.99 mg/m(3), 5.00~9.99 mg/m(3), and >10.00 mg/m(3)) , the acid-proof respirator showed a high filtration efficiency within exposure to 1.5 hours: 95.73%, 98.67%, 98.14%, and 97.78%, respectively, when exposure duration extended to 4 hours, the filtration efficiency of the acid-proof respirator decreased to 91.97%, 82.28%, 70.12%, and 58.56%, respectively.

CONCLUSION

Both the particulate and the acid-proof N95 FFRs met national standards on the particulate filtration efficiency. The acid-proof N95 respirator demonstrates to be more effective in filtering HF and SO2 than the particulate respirator. The filtration efficiency could decrease to an unsafe condition under longer exposure duration, timely replacement of respirator is recommended at the workplace.