Opinions from the non-food Scientific Committees of the European Commission … 

The opinion of SCCS, SCHER and SCENIHR on the Threshold of Toxicological Concern (TTC) approach – which centres upon the idea that, even for chemicals with incomplete toxicity profiles, a level of exposure can be predicted below which there is no appreciable risk to human health – supported the single threshold value of 1.5 μg/kg bw/day for Cramer Class II and III compounds. For substances with structural genotoxicity alerts (possible DNA reactive carcinogens), the default value of 0.0025 μg/kg bw/day was considered acceptable, although the committees stated that its scientific basis should be strengthened. Also discussed was the use of the TTC approach for endocrine disrupting substances, recommended on a case-by-case basis. In general, this approach was considered to be “scientifically acceptable for human health risk assessment of systemic toxic effects caused by chemicals present at very low levels”, but was only applicable to cosmetics belonging to a sufficiently well represented class in the TTC databases (from which the TTC threshold values were derived), and with adequate exposure data available.

European Commission. Scientific Committee on Consumer Safety (SCCS). Scientific Committee on Health and Environmental Risks (SCHER). Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR). Opinion on: Use of the Threshold of Toxicological Concern (TTC) approach for human safety assessment of chemical substances with focus on cosmetics and consumer products. SCCP/1171/08.



…and EFSA

EFSA’s finalised opinion makes several recommendations on its use in assessing possible human health risks from low level exposures. Having reviewed the literature and carried out its own independent analyses, EFSA judged the following oral TTC threshold values to be sufficiently conservative:

  • 0.0025 μg/kg bw/day for substances with structural alerts for genotoxicity
  • 0.3 μg/kg bw/day for organophosphates and carbamates with anti-cholinesterase activity
  • 1.5 μg/kg bw/day for substances belonging to Cramer Classes II and III (abolishing the previous value of 9 μg/kg bw/day for Cramer Class II substances)
  • 30 μg/kg bw/day for substances belonging to Cramer Class I

EFSA concluded that more work needs to be done to establish separate TTC values for exposure via the dermal and inhalation routes. Also discussed was the use of the TTC approach for infants below six months of age (with immature metabolic and excretory systems), for which EFSA recommended consideration on a case-by-case basis. In addition, a number of chemical categories (including metals, proteins and highly potent carcinogens) were defined for which the TTC approach was judged inappropriate.

European Food Safety Authority. Scientific Committee. Scientific opinion on exploring options for providing advice about human health risks based on the concept of Threshold of Toxicological Concern (TTC). EFSA Journal 2012, 10(7): 2750.



The above item was taken from the August 2012 issue of Toxicology and Regulatory News which is sent automatically to members of bibra (click here for more details).