surface groups of RCS particles , affecting how the body responds to the inhaled RCS ( Hall , et al . 2022 ) ( Ramkissoon , et al . 2023 ).
The presence of other , potentially reactive elements in engineered stone dust emissions as well as lung biopsies of silicotic patients , suggests the potential contribution of metal ions in engineered stone to disease risk ( León-Jiménez , et al . 2021 ).
Lower crystalline engineered stone products are being manufactured with products such as amorphous silica ( including glass and recycled glass ) and feldspar . While little is known about the risk profile of emissions ( including dust ) produced when these products are processed , there is some evidence of increased toxicity of freshly ground amorphous silica from these materials ( Ghiazza , et al . 2010 ) ( Porter , et al . 2002 ) ( Pavan , 2020 ) ( Marques Da Silva , et al . 2022 ), as well as differing toxicity profiles of dust from different varieties of feldspar ( Grytting , et al . 2022 ). Further work is required to ensure the materials that may be used in place of crystalline silica in next generation engineered stone products do not pose risks to workers .
2.2.2 Risk profile of engineered stone based on crystalline silica content
There is insufficient evidence to establish a threshold crystalline silica content of engineered stone , beyond which the risk of adverse health effects is unacceptably increased ( for example the 40 % threshold proposed in Options 2 and 3 of this Decision RIS ).
Adverse health effects are associated with airborne silica dust exposure , not the silica content of the bulk material . The limited empirical evidence available supports that a lower silica stone produces less RCS when processed ( Qi and Echt 2016 ) ( Ramkissoon , C , et al . 2022 ), and this in turn supports the logical presumption that reducing the crystalline silica content in the engineered stone slab results in reduced exposure to RCS . However , there is no epidemiological or laboratory toxicological evidence describing how the risk of disease would differ for workers exposed to RCS generated from engineered stone over a range of crystalline silica concentrations , or how it compares to that generated from natural stone . This is particularly important as the processing method is a known determinant of RCS production ( Healy 2014 ) ( van Deurssen , et al . 2014 ), and it can also impact the size of the particles emitted ( Hall , et al . 2022 ).
2.2.3 Impact of manufacturing methods on risk profile
Different manufacturing methods may affect the risk profile arising from processing engineered stone . Resin-based engineered stones have been the most utilised product to date . Moderate heat cures the organic resin binder that holds the stone particles together . Processing resin-based engineered stone can generate high heat which leads to emission of hazardous airborne substances , such as volatile organic compounds ( VOCs ) ( Hall , et al . 2022 ) ( Ramkissoon , et al . 2023 ).
Sintering is a different manufacturing technique that involves subjecting the stone particles to high temperatures and pressure , causing them to compact together , simulating the formation of natural granite , and eliminating the need for resin as a binding agent . Unlike resin-based engineered stone ( comprised of organic and inorganic constituents ) sintered stone has only inorganic ingredients . There is however still uncertainty as to whether the additional mechanical energy and different abrasive action required to process sintered engineered stone results in a different toxicity profile for the dust .
The health risks of emissions produced when processing porcelain-based benchtops ( which may contain crystalline silica and feldspar ) or benchtop materials free from crystalline silica will require further consideration .
DECISION REGULATION IMPACT STATEMENT Prohibition on the use of engineered stone Page 16 of 107