Effect of mask fit testing aimed at reducing the number of neutrophil in nasal swabs in stainless steel welders

Introduction
We evaluated the effect of mask fit testing aimed at reducing the number of neutrophil in nasal swab. Neutrophils are a marker of rhinitis in stainless steel welders. We also assessed the convenience of mask used. Mask fit testing is recommended as a part of a procedure to find an effective and suitable mask for every employee. 

Methods
Research was started by measuring chromium in the working environment and then conducting mask fit testing so that all respondents had their own well fitting mask. The effect was measured by cross over design in 38 stainless steel welders. The incidence of rhinitis was measured by comparing the number of neutrophil from nasal swabs across the shift between respondents wearing well fitting masks and regular masks. We categorized the change in the number of neutrophil using the Weber score. The convenience to the users of the mask was assessed by questionnaire.

Results
The level of chromium in the working environment was 0.003452 mg/m3. When respondents wore a regular mask, the Weber score dropped in 23% respondents, remained the same in 58% respondents and rose in 19% respondents. When respondents wore well fitting masks, the Weber score dropped in 42% respondents, was fixed in 8% respondents and rose in 8% respondents. The proportion of  respondents who experienced a decline in the Weber score was much greater with well fitting masks than with regular masks (p=0.047). The well fitting mask was also thought to be more comfortable than the regular mask according to users personal opinion (p=0.022). 

Discussion
The fitting mask proved to be effective in reducing the marker of rhinitis among stainless steel welders. Workers also appreciated its greater comfort and convenience, thereby increasing the compliance of workers in using mask in industrial environment.