Development and Comparison of Complementary Methods to Study Potential Skin and Inhalational Exposure to Pathogens During Personal Protective Equipment Doffing

Abstract

Background: Fluorescent tracers are often used with ultraviolet lights to visibly identify healthcare worker self-contamination after doffing of personal protective equipment (PPE). This method has drawbacks, as it cannot detect pathogen-sized contaminants nor airborne contamination in subjects' breathing zones.

Methods: A contamination detection/quantification method was developed using 2-µm polystyrene latex spheres (PSLs) to investigate skin contamination (via swabbing) and potential inhalational exposure (via breathing zone air sampler). Porcine skin coupons were used to estimate the PSL swabbing recovery efficiency and limit of detection (LOD). A pilot study with 5 participants compared skin contamination levels detected via the PSL vs fluorescent tracer methods, while the air sampler quantified potential inhalational exposure to PSLs during doffing.

Results: Average PSL skin swab recovery efficiency was 40% ± 29% (LOD = 1 PSL/4 cm2 of skin). In the pilot study, all subjects had PSL and fluorescent tracer skin contamination. Two subjects had simultaneously located contamination of both types on a wrist and hand. However, for all other subjects, the PSL method enabled detection of skin contamination that was not detectable by the fluorescent tracer method. Hands/wrists were more commonly contaminated than areas of the head/face (57% vs 23% of swabs with PSL detection, respectively). One subject had PSLs detected by the breathing zone air sampler.

Conclusions: This study provides a well-characterized method that can be used to quantitate levels of skin and inhalational contact with simulant pathogen particles. The PSL method serves as a complement to the fluorescent tracer method to study PPE doffing self-contamination.

Keywords: doffing self-contamination; exposure assessment; inhalational exposure; methods development; personal protective equipment doffing.

Figure 1.

Map of the study area indicating subject walking path and separate rooms for each activity: (1) personal protective equipment (PPE) donning; (2) contamination; (3) PPE doffing and visible (Glitter Bug) contamination check; and (4) skin swabbing for polystyrene latex spheres. Abbreviations: PPE, personal protective equipment; PSLs, polystyrene latex spheres.

Figure 2.

Linearity of recovery of polystyrene latex spheres (PSLs) after swabbing porcine skin coupons spiked with PSL numbers ranging from 10⁰ to 10⁵ (total of 25 swabbed skin coupons). Data are shown as average ± 1 standard deviation. Across the range of spiked PSL numbers, the average recovery efficiency was about 40% ± 29%. Abbreviation: PSLs, polystyrene latex spheres.

Figure 3.

Qualitative illustrations of relative sizes and numbers of contamination spots for each subject for both types of contamination methods—fluorescent tracer method vs polystyrene latex sphere (PSL) method. The fluorescent tracer contamination was detected by eyesight under ultraviolet light, but the PSLs were swabbed and quantified using microscopy. PSLs were not detectable by eyesight alone. Abbreviation: PSL, polystyrene latex sphere.

Figure 4.

Skin swabbing results for polystyrene latex spheres (PSLs) detected across subjects and swab locations on the head/face vs hands/wrists after doffing of personal protective equipment. Results are presented as number of PSLs per cm² of swabbed skin, as estimated using anthropomorphic data (Supplementary Table 1). Abbreviation: PSLs, polystyrene latex spheres.

Figure 5.

Cumulative number of polystyrene latex spheres (PSLs) across each subject’s skin swabs vs the concentration of PSLs measured in the breathing zone of study subjects via Button Sampler during personal protective equipment doffing. Only subject 4 had any PSLs detected in the breathing zone. Abbreviation: PSLs, polystyrene latex spheres.