S59 Silicosis, tuberculosis and silica exposure among artisanal and small-scale miners: a systematic review and modelling paper

<h3>Background</h3> An estimated 44 million artisanal and small-scale miners (ASM), largely based in developing economies, face significant occupational respiratory diseases risks. We aimed to review studies describing silicosis and tuberculosis (TB) prevalence and respirable crystalline silica (RCS) exposures among ASM and use previous evidence to model the relationship between silica exposure and silicosis and TB outcomes. <h3>Methods</h3> We searched PubMed, Web of Science, Scopus and Embase for studies published before the 24th March 2023. Our primary outcomes were silicosis or TB among ASM. Secondary outcomes were respirable dust or silica measurements, spirometry values and respiratory symptom prevalence. A systematic review and meta-analysis were performed and risk of bias assessed using the Joanna Briggs Prevalence Critical Appraisal Tool. Logistic and Poisson regression models with predefined parameters were used to estimate silicosis prevalence and TB incidence at increasing distributions of cumulative silica exposure. <h3>Results</h3> We identified 18 eligible studies that included 29,562 miners from 13 distinct populations in 10 countries. Silicosis prevalence ranged from 11 to 37%, despite four of five studies reporting an average median duration of mining of &lt;6 years. Tuberculosis prevalence was high; microbiologically confirmed disease ranged from 1.8 to 12% in six studies and clinical disease 3.0 to 17% in four studies. Meta-analysis results demonstrated very high heterogeneity (<i>I</i>² Silicosis 97% and microbiological TB 98%). Average RCS intensity was very high (range 0.19–89.5 mg/m³) in five studies. Respiratory symptoms across three studies were common while spirometry findings in three studies were mixed. Our modelling demonstrated greater reductions in silicosis prevalence and TB incidence at high RCS exposure distributions, which were robust across multiple scenarios (figure 1). These models may be viewed interactively at: https://phowlett.shinyapps.io/sil_tb_app/. Study quality was mixed; recurrent issues included selection and measurement bias. <h3>Discussion</h3> Despite limitations of included studies, the prevalence of silicosis and TB appears high which is likely due to RCS exposures between 4–1790 times above the US permissible exposure limit. Our modelling demonstrated the greatest respiratory health benefits of reducing RCS are in those with the highest exposures. Effective low-cost interventions are available and should be studied and implemented.