Risk Characterization for Silica-related Silicosis and Lung Cancer in Communities Adjacent to Sand and Gravel Extraction Facilities: Examining Limitations in our Current Risk Methods

Anthony Russell¹Kenneth A. Mundt²Andrew Maier^1*

• ¹Integral Consulting (United States), Seattle, United States
• ²University of Massachusetts Amherst, Amherst, Massachusetts, United States

Effectively managing and reducing occupational exposure to crystalline silica continues to be a critical priority for public health agencies. The relationship between workplace inhalation exposure to respirable crystalline silica (RCS) and the onset of silicosis is well known. However, ongoing health effects research continues to explore the impacts of the physical and chemical forms of crystalline silica and the potential of RCS to cause lung-disease. Further, the levels at which occupational RCS exposure potentially increases the risk of lung cancer in occupational settings remains uncertain. This investigation examines the implications for assessing community exposure and cancer risk from: 1) direct quantitative application of occupational epidemiology data using non-threshold assumptions, and 2) application of threshold-like risk assessment approaches informed by mode of action hypotheses. Community RCS exposures adjacent to National Sand, Stone, and Gravel Association (NSSGA) member facilities were estimated from exposure levels reported in a forthcoming publication (Richards and Brozell 2025). The exposure levels were supplemented by publicly available data from state and federal governing bodies. Three modifying factors were hypothesized as key in determining the disease-causing potential of RCS from community exposures when extrapolating from occupational epidemiology findings. The regression analysis resulted in a lung cancer risk = 0.069(mg/m3) X + 1.17 (p = 0.017) and a silicosis risk = 1.75 (mg/m3) X + 1.67 (p < 0.001). At the community background exposure equivalent of 4 µg/m3, these regression analyses resulted in a RR for lung cancer of 1.17 (95% CI: 1.169 – 1.171) and a RR for silicosis of 1.68 (95% CI: 1.66 – 1.69). Mode of action analyses supported a threshold-like response for lung cancer with inflammatory markers being key drivers.: Risk of silicosis and lung cancer due to community exposures to RCS needs to be addressed in the context of observable increases of disease in populations exposed to low to moderate levels of RCS. Direct epidemiology studies of community exposures are lacking, but no clear indication of concern based on lung effect prevalence has been reported.