As Australia is set to impose a ban on engineered stone linked to a deadly lung disease in tradespeople, scientists are trying to work out just what makes the material so dangerous.
The disease is a form of silicosis, an incurable condition caused by breathing in toxic silica dust after cutting and grinding engineered – or artificial – stone. It can lead to the scarring and inflammation of the lungs.
Silicosis has been known about for decades as an occupational hazard for those in the building industry as well as for miners and stonemasons. But the current outbreak seems to be more aggressive, striking younger workers and progressing faster, often destroying people’s lungs within a decade.
It seems to be linked to the recent fashion of installing kitchen and bathroom worktops made of engineered stone, a relatively new material that releases a toxic dust when sawn or polished.
About 10 silicosis cases linked to engineered stone have recently emerged in the UK. In Australia, where the ban is due to come into force on 1 July, over 500 cases were identified by a screening programme. It is unclear why the country has such a high rate.
In the UK, though, safety bodies say it is safe to work with the material under stricter new rules, such as only cutting the material with special machines that contain the dust with water.
What causes silicosis?
Silicosis was usually caused by decades of workplace exposure to fine silica dust, present in various kinds of stone, such as sandstone, or construction materials like bricks, rooftiles and concrete.
Silica dust particles are so fine they go deep into the lungs and cannot be cleared, said Professor Mordechai Kramer, a respiratory doctor at Rabin Medical Center in Petah Tikva, Israel. “If you try to cough, you’re not getting the dust out.”
Over time, the particles cause inflammation and this gradually leads to lung tissue becoming stiff and scarred. Initial symptoms include a cough and shortness of breath, eventually progressing until people cannot walk far without breathing difficulties and needing a supply of oxygen. It can also lead to deaths: 13 artificial countertop cutters in California, who are overwhelmingly Latino migrants, have died from silicosis.
Silica exposure can also trigger lung cancer and autoimmune conditions, where the immune system starts attacking the body’s own tissues.
Silicosis today
While this kind of long-term workplace exposure to silica continues, alarm bells have begun ringing over a more aggressive and rapidly progressing form of the condition.
It first became prominent when Professor Kramer noticed that 25 silicosis patients had been evaluated for a lung transplant in Israel since 1997, while in the previous four decades no silicosis patients had required a lung transplant.
All of the 25 cases had been exposed by working with engineered stone, an increasingly popular choice for kitchen and bathroom counters in many countries.
It is made by crushing stone into dust, then mixing it with resins to create a solid slab that is stronger and more heat resistant than natural stones like granite. It can also be made in a range of colours and patterns.
Professor Kramer was also alarmed to see that the new silicosis patients were deteriorating more rapidly. Those affected had typically been working with the material for less than 10 years. With the old form of silicosis, people usually took more than two decades to get symptoms. In a medical journal called Chest, Professor Kramer christened the new form artificial stone silicosis.
Deadly dust
The chief suspect for why engineered stone is so deadly – causing silicosis in one in four of those who work with it, according to an Australian study – is its high content of silica. The slabs can contain over 90 per cent of this compound. Granite, for instance, contains about 40 per cent silica.
Another concern is the other compounds mixed in with the crushed stone, including resin to bind the particles together, as well as pigments containing metals, such as titanium, iron and copper.
Recent research on lung cells grown in a dish suggests that these metals contribute to the toxicity of the dust, according to Dr Jane Bourke at Monash University in Melbourne.
“They are part of the dust that’s inhaled. We are not sure of the impact of those chemicals. The different brands of stone potentially have different toxicity.”
Open questions
A further question is whether engineered stone creates more of the most dangerous kinds of dust when it is cut, said Professor Malcolm Sim, also at Monash University, who helped document the rise in artificial stone silicosis in Australia over the past decade.
Tests of the air from workshops suggest engineered stone releases higher levels of extremely small particles of silica, he said. “The dust seems to break down more easily than natural stone.”
A different theory comes from Kevin Bampton, of the British Occupational Hygiene Society, which has just issued new safety rules for working with engineered stone, after noting a small cluster of about 10 cases of artificial stone silicosis in the UK.
Mr Bampton said the cases may not be caused by the stone’s inherent properties, but may reflect the recent rise in worktop production by small kitchen-fitting firms that are less likely to use safety precautions.
“Previously, we would import products finished in factories. Some manufacturers relatively recently have started providing products which a kitchen fitter can buy and cut a sink hole in,” he said.
Such small businesses are more likely to be unregistered for tax and to employ undocumented migrants, who may be unaware of safety rules, said Mr Bampton. “Super-exposure to massive amounts of dust – that’s what these poor young chaps are facing. It’s not the substance, it’s the exposure.”
But Professor Sim disagreed, saying the rise in aggressive silicosis in Australia had happened so fast, it pointed to engineered stone being uniquely toxic, rather than a change in working practices.
“It’s a brand new substance that has only come into use in recent years,” he said. “There’s something completely different going on here.”