A study of respirator fit and face sizes of National Health Laboratory Service (NHLS) respirator users during 2013-2014
Manganyi, Mafanato Jeanneth
In the hierarchy of controls, the use of respirators is listed as the least preferable means of exposure or infection control; however it is often the primary means of protection in many industries including the health care industry. The National Health Laboratory Service (NHLS) provides diagnostic pathology laboratory services to the national and provincial health departments in nine South African Provinces. NHLS staff includes N95 respirator users working with infectious diseases such as tuberculosis (TB). It has been shown that an individual‟s facial structure influences their chances of achieving respirator fit. Study aim This study aims to describe the proportion of NHLS respirator users with adequate quantitative respirator fit while wearing their currently supplied respirators. Study objectives 1. To determine the proportion of NHLS respirator users achieving an adequate fit 2. To describe facial characteristics of NHLS respirator users and to group these faces into three face sizes (small, medium and large) based on the NIOSH fit test panel and two facial dimensions (face width and face length) 3. To explore the relationship between face size and demographic variables (sex, age, and race) of tested NHLS respirator users 4. To explore the influence of face size on respirator fit obtained by NHLS respirator users wearing their current respirator Materials and methods This was a cross sectional study with descriptive and analytical components. NHLS employees from selected laboratories in Gauteng, Cape Town and Durban were invited to participate. Study participants were respirator users and the majority were exposed to hazardous biological agents (HBA) including tuberculosis (TB). The NHLS employees included the four common South African race groups (as per Statistics South Africa) namely African, White, Coloured and Asian. A minimum sample size of 240 study participants was calculated for the study based on 30 participants per race group and sex. At the close of data collection 610 employees participated in this study. Quantitative respirator fit testing was conducted using a Portacount fit testing machine. Four facial dimensions were taken using callipers and a tape measure. STATA 12 was used to perform descriptive and interferential statistics. The associations between pass and fail and key predictors were investigated by chi-square tests. Student‟s t-tests and Kruskal-Wallis one way analysis of variance were used to investigate the overall fit factor in groups by face size, sex, race, age group and nose bridge width. The effect of the independent variables was explored using multiple linear regressions stratified by sex. Results and discussion Of the 610 employees who participated, a large percentage (78%) of NHLS respirator users failed fit testing and was not protected by their currently supplied medium size respirator. Ninety one percent of the respirators supplied were medium. The race group which achieved a highest proportion of fit factor passes was White (27%) followed by Africans (26%), a drop of pass rate was seen in Coloureds (21%) while the Asians achieved the lowest proportion at 7%. These poor pass rates indicate that a respiratory protection programme is needed in the NHLS, with focus on supplying the correct size and style of respirators. When the measured face length and face width of participants were plotted against the new bivariate NIOSH fit test panel, it was found that 35%, 58% and 7% of the participants had small, medium and large faces respectively. Our study population did fall within the panel but the distributions were different between cells compared to the American population. In the South African population Asians were more likely to be associated with a small face than Africans (p=0.00), Whites (p=0.00) and Coloureds (p= 0.00). While the Coloureds were not significantly different from the Whites or Africans (p= 0.397 p=0.713). The study showed that in addition to face length and face width, nose bridge width play a role in respirator fit. Multiple linear regression analysis showed that face size and nose bridge width were both significant predictors of overall fit. Although both sex and race predicted respirator fit in unadjusted analysis, these fell away when facial characteristic measurements were placed in the model. This suggests that sex and race maybe proxies for facial characteristics in predicting respirator fit. Conclusion and recommendation The high percentage of employees in this study sample achieving poor fit with their current respirator indicates a need for immediate testing of all NHLS respirator users and for a range of sizes and styles of respirators to be provided to all staff requiring respirators. The use of poorly fitting respirators could create a false impression of protection in the laboratories where employees are possibly exposed to HBA‟s including all types of TB. This also leads to in a large amount of funds being spent on purchasing ineffective respirators at the NHLS. A respiratory protection programme including respirator fit testing needs to be compiled, implemented and reviewed regularly to ensure sustainability. Future studies may include the investigation of the relevance of panels used in designing respirators to be worn by South Africans.
A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Public Health (Occupational Hygiene). Johannesburg, May 2015