ASASP Position on Ongoing Harmonised Classification and Labelling procedure (CLH) for Silicon Dioxide
On 9 July, ASASP held an online Forum for Downstream Users of Synthetic Amorphous Silica (SAS). The meeting focused on the CLH classification proposal by the Dutch National Institute for Public Health and the Environment (RIVM) and the public consultation which will run from June 10 until August 9, 2024.
ASASP has now published its position, explaining that with SASforREACH (the EU REACH consortium for Silicon Dioxide / Synthetic Amorphous Silica), we are of the opinion that the proposed classification for Silicon Dioxide as STOT RE 1 is not warranted as it is not based on intrinsic properties of the substance and for the following reasons:
1. SAS is a substance with no intrinsic toxicity
Synthetic Amorphous Silica (SAS) is being proposed for classification based on adaptive, unspecific inflammatory effects in rat repeated dose inhalation toxicity studies, which are generic to all particles regardless of the substance. Classifying a substance based only on its particle effects deviates from the legal scope of the CLP because the hazard identification process can only assess the intrinsic properties of substances to determine their potential to cause harm.
2. SAS is safe as placed on the market
The assumption made by the CLH Report Submitter that all untreated SAS forms are respirable is a fundamental error. More than 90% of SAS forms, as placed on the market (as per Article 8(6) CLP, as supported by recital 30), are not respirable. Any concerns regarding inhalation exposure are thus mitigated, if not eliminated.
3. What’s tested in toxicity tests is different to what’s on the market
Repeated dose inhalation studies according to OECD test guidelines require particles to be intentionally modified to be respirable for the test animals to investigate effects (OECD TG 4132 with MMAD - mass median aerodynamic diameter ≤ 2 µm respectively ≤ 3 µm in the previous test guideline). Inhalation testing for regulatory purposes can therefore not be conducted on SAS forms as placed on the market, as required by Articles 8(6) and 9(5) of the CLP, recital 30.
4. CLP is not fit for purpose to regulate particles
The proposed cut-off limit concentrations for STOT-RE classification by CLP (Annex I 3.9) are unrealistically high. Repeated dose inhalation studies show that inflammation is triggered by respirable particles at concentrations far below these limits. SAS shows reversible inflammation caused by physical conditions, not intrinsic properties of the substance itself.
5. Rats are more sensitive to particles than humans
Rats are more sensitive to particles than humans, as shown by inhalation studies on various materials, not just SAS. This is due to the anatomy of rat lungs, which are predisposed to more severe inflammation. Over 40 years of human health data supports this, showing no respiratory toxicity in humans.
6. The whole respiratory tract is not affected
The proposal by the CLH Report Submitter to classify the whole respiratory tract is made on a wrong interpretation of observations in the nasal cavities. These observations are not relevant for human health hazard assessment. The inflammatory effects observed in the studies are restricted to the lungs and its associated lymph nodes.
Based on the above, ASASP and SASforREACH do not agree with the proposed classification of SAS as STOT RE 1. It contradicts the law as it stands. Should classification continue to be proposed, we acknowledge an alternative approach where - based on the data provided by industry - classification is limited to respirable particles of forms of SAS as placed on the market reaching the alveoli with the target organ being lung and not the respiratory tract.
The Slide Deck shared during the Forum, and our full Position Paper can be consulted here and used for contributions to the Public Consultation.
