Systematic review of epidemiological studies evaluating the association between exposure to man-made vitreous fibers and non-malignant respiratory diseases.

This study aimed to systematically review and synthesize epidemiological evidence evaluating the association between occupational man-made vitreous fiber (MMVF) exposure and non-malignant respiratory disease (NMRD). We searched PubMed and Scopus databases to identify epidemiological studies evaluating the association between occupational MMVF exposure (limited to insulation wools) and at least 1 NMRD outcome published prior to January 2023. A total of 23 studies met our inclusion criteria. Studies of NMRD mortality among workers with MMVF exposure (n = 9) predominately reported null findings. Qualitative and quantitative synthesis of evidence from these studies suggests that MMVF exposure is not associated with elevated risk of NMRD mortality. The remaining 14 studies evaluated NMRD morbidity, specifically self-reported respiratory symptoms and/or subclinical measures of respiratory disease. Our review did not identify any consistent or compelling evidence of an association between MMVF exposure and any NMRD morbidity outcome; however, this body of evidence was largely limited by cross-sectional design, self-reported exposure and/or outcome ascertainment, incomplete statistical analysis and reporting, and questionable generalizability given that 13/14 studies were published over 20 years ago. We recommend that future studies aim to overcome the limitations of this literature to more accurately characterize the association between occupational MMVF exposure and NMRD morbidity.

Emissions associated with operations of four different additive manufacturing or 3D printing technologies.

In this pilot-scale study, a wide range of potential emissions were evaluated for four types of additive manufacturing (AM) machines. These included material extrusion (using acrylonitrile-butadiene-styrene [ABS]); material jetting (using liquid photopolymer); powder bed fusion (using nylon); and vat photopolymerization (using liquid photopolymer) in an industrial laboratory setting. During isolated operation of AM machines, adjacent area samples were collected for compounds of potential concern (COPCs), including total and individual volatile organic compounds (VOCs), nano- and micron-sized particulate matter, and inorganic gases. A total of 61 compounds were also sampled using a canister followed by gas chromatography and mass spectrometry analysis. Most COPCs were not detected or were measured at concentrations far below relevant occupational exposure limits (OELs) during AM machine operations. Submicron particles, predominantly nanoparticles, were produced during material extrusion printing using ABS at approximately 12,000 particles per cubic centimeter (p cm-3) above background. After subtracting the mean background concentration, the mean concentration for material extrusion printing operations correlated with a calculated emission rate of 2.8 × 1010 p min-1 under the conditions tested. During processing of parts produced using material jetting or powder bed fusion, emissions were generally negligible, although concentrations above background of respirable and total dust were measured during processing of powder bed fusion parts. Results of this pilot-scale study indicate that airborne emissions associated with AM operations are variable, depending on printing and parts handling processes, raw materials, and ventilation characteristics. Although personal samples were not collected in this pilot-scale study, the results can be used to inform future exposure assessments. Based on the results of this evaluation, measurement of submicron particles emitted during material extrusion printing operations and dust associated with handling parts manufactured using powder bed fusion processes should be included in exposure assessments.

Systematic review and meta-analysis of epidemiological literature evaluating the association between exposure to man-made vitreous fibers and respiratory tract cancers.

We conducted a systematic review and meta-analysis of epidemiological studies that evaluated occupational exposure to man-made vitreous fibers (MMVF) including glass, rock, and slag wools, and respiratory tract cancers (RTC) including cancers of the larynx, trachea, bronchus, and lung. The MEDLINE/PubMed and Web of Science databases were searched in order to identify epidemiological studies that evaluated the association between occupational MMVF exposure and RTCs. We performed random-effects meta-analyses of relevant studies identified by our literature search, and evaluated sources of between-study heterogeneity. The pooled relative risk (RR) of RTC among workers exposed to MMVFs was 1.09 (95% CI = 0.97, 1.22). The RR was closer to 1.0 when limiting the analysis to effect estimates from studies that accounted for the main a priori risk factors for RTC, asbestos exposure and smoking (RR = 1.03, 95% CI = 0.90, 1.18). Overall, our synthesis of the epidemiological literature suggests that occupational MMVF exposure is not associated with risk of RTC.