The draft report, published in November, comes just days before a 30 December deadline to pre-register substances for safety screening and registration under the EU's chemical regulation REACH.
The report assess the applicability of the so-called Threshold of Toxicological Concern (TTC) approach to the human health-related risk assessment of chemical substances.
The TTC concept is based on 'safe levels of of exposure' and evaluates toxicity based on substances' known toxicity or chemicals that share similar characteristics. According to the EU scientific committees, it is used in situations where there is limited or no information on the toxicity of a compound, and where human exposure is so low that adverse effects are not expected.
The concept is currently used for materials which come into contact with food, but its application in a number of other areas is under discussion, notes the report, listing consumer products, food additives, pesticides and cosmetics as examples.
A critical review of the available scientific literature on the use of the TCC approach was requested by the European Commission in view of generalising its use. It also follows recent research by the European cosmetics industry association, which found that despite being a useful extra tool in the absence of chemical-specific toxicology data, the TTC concept did not provide a full safety evaluation of cosmetic ingredients, in particular regarding local effects at the site of application.
The draft opinion underlines that appropriate exposure assessment is essential for TTC, adding that only limited knowledge exists regarding a wide variety of consumer products with "complex exposure scenarios" and "multiple exposure routes".
The scientific committees note that "uncertainties are higher and methodology is less developed" for consumer products such as cleaning products, cosmetics and toys, which involve oral exposure, skin contact and exposure via inhalation. Meanwhile, "significant" exposure is likely for products that are frequently used, they add.
Regarding cosmetic ingredients, the committees conclude that the use of the TTC approach is "at present in general not applicable" for some substances, as the current exposure database is "inadequate" for that purpose.
In conclusion, the committees call for further research to be carried out into the development and validation of toxicity databases, particularly in areas where insufficient numbers of representative chemicals are included. They also think that the methodology for assessing systemic exposure needs to be improved and appropriate exposure data generated for the various exposure scenarios.
It is not yet clear how the use of TTC in relation to REACH will take place, but a guidance document on its use in EU chemicals regulation points to various limitations of the approach with respect to the "applicability of [the] database, excluded classes of chemicals and extrapolation to other exposure routes than oral exposure".
With regard to exposure, the document states that, for human health aspects, the TTC approach is only applicable in cases where detailed information is available on all anticipated use scenarios for which the risk assessment is provided. Therefore, the scientific committees note that in situations where there are a multitude of uses and applications, it may not be possible to rely on TTC thresholds to conduct risk assessment within REACH.
