Earlier this month we discussed the shifting occupational exposure standards set to take effect in Queensland over the coming week. A recent international study into silicosis progression was recently published in the CHEST Journal. The findings of this study evidence that the lasting effects of the silicosis epidemic that have arisen in recent years will continue to cause ripples for years to come.
Of the 106 Spanish participants in the study, at diagnosis ninety-nine (99) had simple silicosis and seven (7) had progressive massive fibrosis (PMF). At the time of publishing 56% of these patients had progressed two (2) or more ILO categories (significant radiological progression) and the number diagnosed with PMF had increased to 40 (37.7%). All of these results occurred following complete cessation of occupational exposure following diagnosis.
An important discovery from the study is the suggestion that silicosis resulting from exposure to engineered or manufactured stone products is more aggressive than traditional silicosis. The data reflects rapid progression to PMF in a number of cases and although the higher silica content (approximately 90%) has been predominately to blame, studies also suggest that the high content of transition metal ions and/or the coating of silica particles with resins causes the respirable crystalline silica to possess greater toxicity than that of natural stone products such as granite, limestone and marble.
The study also draws attention to the fact that despite the introduction of new training, increased inspections and controlled usage of protective measures by the regional health authority in Spain, silicosis cases continue to arise, a clear indication that the silicosis epidemic has yet to be contained.
The most alarming conclusion of this study is that silicosis as a result of exposure during the fabrication of engineered stone products progresses rapidly, despite removal from exposure. An average follow-up of 4 years in the Spanish study sample evidenced a 37.7% progression to PMF and 25% experienced significant decline in lung function values annually. At the rate of progression evidenced, many of these individuals may develop respiratory failure in the next few years and will require lung transplantation, which remains the only effective treatment available for those suffering from silicosis.
A follow up Editorial also published within the CHEST Journal highlights the stark contrast of these results to traditional silicosis patients, one study evidencing that disease progression in coal miners and granite workers evidenced a 10% progression to PMF in silicosis patients over an average of twenty-two (22) years.
The Editorial also notes the apparent increased toxicological nature of respirable crystalline silica dust compared to its natural counterparts. Stating that this increased toxicity may be a result of components of the pigments including Potassium, Sodium, Calcium, Magnesium, Iron, Copper, Zinc and Titanium, also pointing out that recent work has evidenced a significantly higher percentage of ultra-fine particles (<0.1 µm in diameter) during the fabrication process, which exhibit larger reactive surface areas compared to natural stone silica dust.
The biggest takeaway from both the study and the follow-up editorial is that primary prevention is critical, the evidence now shows that removal from exposure is insufficient to halt progression of the condition and although the development and evolution of future treatments, interventions, surveillance and research are vital to this field, the catch-up approach currently implemented is clearly not working.
The study has also evidenced that improved occupational exposure controls and awareness did not prevent further diagnoses in Spain.
The question therefore remains, will the stricter occupational exposure standards be sufficient to protect workers within the stonemasonry industry or is it the case that engineered stone can never be worked with safely.
