Background
After IARC classified  respirable crystalline silica (RCS) as a proven occupational carcinogen in 1997 the European Industrial Minerals Association started a prospective dust monitoring programme in 2000. The aim of the dust monitoring programme was to document existing personal exposure concentrations and by introducing risk management measures via best practices guidance lower the personal exposure to RCS and rconsequently educe the risk of lung cancer and silicosis.

Objective
To estimate the number and percentage of lung cancer and silicosis cases prevented due to the lowering of personal exposure to respirable crystalline silica.

Methods
The numbers of prevented lung cancer and silicosis cases in the European industrial minerals sector (IMA-Europe) achieved by their Dust Monitoring Programme (IMA-DMP) were estimated using a quantitative counterfactual model.
Cohort Characteristics
- 42,500 workers, ages 20-65, followed 2000-2040 and turnover rates 2%.
- Exposure Data: Personal full-shift RCS exposure measurements (40,000) from the IMA-DMP started in 2000.
- Median concentration in 2000 was 14 µg/m3 and annual decline was -4.5% (see Figure).
- Baseline disease rate for lung cancer and mortality from Netherlands Cancer Registry (NKR, 1989-2020)
- Baseline disease rate for silicosis from Danish Occupational Cohort (DOC*X, 1976-2015).
- Exposure-response relationship for lung cancer: IRR 1.06 per 1,000 µg/m³-years
- Exposure-response relationship for silicosis: IRR 1.20 per 50 µg/m³-years   
Simulation Model
A Monte Carlo simulation (100 iterations) was used to estimate attributable lung cancer cases and silicosis for two exposure scenarios:
(1)  steady-state exposure at on average 14 µg/m³ (no trend)
(2) declining exposure trend of 4.5% per annum from 2000 till the end of 40-year follow-up; steady state before 2000
Acquired cumulative exposure of the population was simulated as a time series with an autoregressive component by sampling from an annual exposure distribution with a three orders of magnitude range.
Assumptions
-Silica exposure was accumulated over the age of 20–64.
-Only workers aged 20–29 were replaced by new hires with no prior exposure.

Results
We estimated 3.5 times more silicosis cases (n=2,451) than lung cancer cases (n= 702). The decline in exposure prevented 10 times more silicosis cases than lung cancer cases (277 versus 27 cases). The risk management measures taken by the industrial minerals sector prevented 4% of all lung cancer cases (20% of lung cancer cases attributable to RCS) and 12% of silicosis cases.

Conclusions
The industry-wide initiative by IMA-Europe to lower the exposure to respirable crystalline silica and to document it by prospectively collect personal exposure data enabled estimation of prevented cases of lung cancer and silicosis. 
This proactive approach by a sector that cares about its employees resulted in around a 12% reduction in silicosis cases and 20% reduction in lung cancer cases due to RCS within the IMA workforce. So, effective prevention by lowering the exposure to a lung carcinogen is possible, but unfortunately not every industrial sector is taking such a proactive approach. Furthermore, it also requires appropriate occupational exposure limit values set and enforced by government regulatory agencies.

Long term trend in exposure to respirable crystalline silica