Personal protective equipment for preventing asbestos exposure in workers.

BACKGROUND: Asbestos exposure can lead to asbestos-related diseases. The European Union (EU) has adopted regulations for workplaces where asbestos is present. The EU occupational exposure limit (OEL) for asbestos is 0.1 fibres per cubic centimetre of air (f/cm3 ) as an eight-hour average. Different types of personal protective equipment (PPE) are available to provide protection and minimise exposure; however, their effectiveness is unclear.

OBJECTIVES: To assess the effects of personal protective equipment (PPE), including donning and doffing procedures and individual hygienic behaviour, compared to no availability and use of such equipment or alternative equipment, on asbestos exposure in workers in asbestos demolition and repair work.

SEARCH METHODS: We searched MEDLINE, Embase, CENTRAL, and Scopus (September 2022), and we checked the reference lists of included studies.

SELECTION CRITERIA: We included studies that measured asbestos concentration outside and inside PPE (considering outside concentration a surrogate for no PPE), exposure to asbestos after doffing PPE, donning and doffing errors, nonadherence to regulations, and adverse effects of PPE.

DATA COLLECTION AND ANALYSIS: Two review authors selected studies, extracted data, and assessed risk of bias using ROBINS-I. We categorised PPE as full-face filtering masks, supplied air respirators (SARs), and powered air-purifying respirators (PAPRs). Values for asbestos outside and inside PPE were transformed to logarithmic values for random-effects meta-analysis. Pooled logarithmic mean differences (MDs) were exponentiated to obtain the ratio of means (RoM) and 95% confidence interval (95% CI). The RoM shows the degree of protection provided by the respirators (workplace protection factor). Since the RoM is likely to be much higher at higher outside concentrations, we presented separate results according to the outside asbestos concentration, as follows. • Below 0.01 f/cm3 (band 1) • 0.01 f/cm3 to below 0.1 f/cm3 (band 2) • 0.1 f/cm3 to below 1 f/cm3 (band 3) • 1 f/cm3 to below 10 f/cm3 (band 4) • 10 f/cm3 to below 100 f/cm3 (band 5) • 100 f/cm3 to below 1000 f/cm3 (band 6) Additionally, we determined whether the inside concentrations per respirator and concentration band complied with the current EU OEL (0.1 f/cm3 ) and proposed EU OEL (0.01 f/cm3 ).

MAIN RESULTS: We identified six studies that measured asbestos concentrations outside and inside respiratory protective equipment (RPE) and one cross-over study that compared the effect of two different coveralls on body temperature. No studies evaluated the remaining predefined outcomes. Most studies were at overall moderate risk of bias due to insufficient reporting. The cross-over study was at high risk of bias. Full-face filtering masks Two studies evaluated full-face filtering masks. They provided insufficient data for band 1 and band 6. The results for the remaining bands were as follows. • Band 2: RoM 19 (95% CI 17.6 to 20.1; 1 study, 3 measurements; moderate certainty) • Band 3: RoM 69 (95% CI 26.6 to 175.9; 2 studies, 17 measurements; very low certainty) • Band 4: RoM 455 (95% CI 270.4 to 765.1; 1 study, 16 measurements; low certainty) • Band 5: RoM 2752 (95% CI 1236.5 to 6063.2;1 study, 3 measurements; low certainty) The inside measurements in band 5 did not comply with the EU OEL of 0.1 f/cm3 , and no inside measurements complied with the proposed EU OEL of 0.01 f/cm3 . Supplied air respirators Two studies evaluated supplied air respirators. They provided no data for band 6. The results for the remaining bands were as follows. • Band 1: RoM 11 (95% CI 7.6 to 14.9; 1 study, 134 measurements; moderate certainty) • Band 2: RoM 63 (95% CI 43.8 to 90.9; 1 study, 17 measurements; moderate certainty) • Band 3: RoM 528 (95% CI 368.7 to 757.5; 1 study, 38 measurements; moderate certainty) • Band 4: RoM 4638 (95% CI 3071.7 to 7044.5; 1 study, 49 measurements; moderate certainty) • Band 5: RoM 26,134 (16,647.2 to 41,357.1; 1 study, 22 measurements; moderate certainty) All inside measurements complied with the current OEL of 0.1 f/cm3 and the proposed OEL of 0.01 f/cm3 . Powered air-purifying respirators Three studies evaluated PAPRs. The results per band were as follows. • Band 1: RoM 8 (95% CI 3.7 to 19.1; 1 study, 23 measurements; moderate certainty) • Band 2: RoM 90 (95% CI 64.7 to 126.5; 1 study, 17 measurements; moderate certainty) • Band 3: RoM 104 (95% CI 23.1 to 464.1; 3 studies, 14 measurements; very low certainty) • Band 4: RoM 706 (95% CI 219.2 to 2253.0; 2 studies, 43 measurements; very low certainty) • Band 5: RoM 1366 (544.6 to 3428.9; 2 studies, 8 measurements; low certainty) • Band 6: RoM 18,958 (95% CI 4023.9 to 90,219.4; 2 studies, 13 measurements; very low certainty) All inside measurements complied with the 0.1 f/cm3 OEL when the outside concentration was below 10 f/cm3 (band 1 to band 4). From band 3, no measurements complied with the proposed OEL of 0.01 f/cm3 . Different types of coveralls One study reported the adverse effects of coveralls. A polyethylene suit may increase the body temperature more than a ventilated impermeable polyvinyl (PVC) coverall, but the evidence is very uncertain (MD 0.17 °C, 95% CI -0.08 to 0.42; 1 study, 11 participants; very low certainty).

AUTHORS' CONCLUSIONS: Where the outside asbestos concentration is below 0.1 f/cm3 , SARS and PAPRs likely reduce exposure to below the proposed OEL of 0.01 f/cm3 . For outside concentrations up to 10 f/cm3 , all respirators may reduce exposure below the current OEL, but only SAR also below the proposed OEL. In band 5 (10 to < 100 f/cm3 ), full-face filtering masks may not reduce asbestos exposure below either OEL, SARs likely reduce exposure below both OELs, and there were no data for PAPRs. In band 6 (100 f/cm3 to < 1000 f/cm3 ), PAPRs may not reduce exposure below either OEL, and there were no data for full-face filtering masks or SARs. Some coveralls may increase body temperature more than others. Randomised studies are needed to directly compare PAPRs and SARs at higher asbestos concentrations and to assess adverse effects. Future studies should assess the effects of doffing procedures.