Registration Dossier

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
basic toxicokinetics
Type of information:
other: expert statement
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Theoretical assessment taking all currrently available relevant information into account, based on the REACH Guidance: Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7c Endpoint specific guidance. Since this is a theoretical assessment, the Klimisch value cannot be 1.
GLP compliance:
no
Type:
absorption
Results:
For risk assessment purposes, % is used for oral, dermal and inhalation absorption

Description of key information

A toxicokinetic assessment was performed based on the available data of the substance. Based on the physical/chemical properties of the substance, absorption factors for this substance are derived to be 50% (oral), 100% (inhalation) and 50% (dermal) for risk assessment purposes. The bioaccumulation potential is expected to be low.

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential
Absorption rate - oral (%):
50
Absorption rate - dermal (%):
50
Absorption rate - inhalation (%):
100

Additional information

A toxicant can enter the body via the gastrointestinal tract, the lungs and the skin. In general, a compound needs to be dissolved before it can be taken up from the gastrointestinal tract after oral administration (Martinez et al., 2002). DBI is moderately water soluble (0.0748 g/l) and, in combination with the partition coefficient (3.8) and molecular weight (242.31), the absorption of DBI is likely limited by a low ability to dissolve in the gastrointestinal fluids and hence make contact with the mucosal surface.

Based on the water solubility, molecular weight, and the log P, for risk assessment purposes oral absorption of DBI is set at 50% (ECHA REACH guidance Chapter R.7c, 2014). The oral toxicity data do not provide reason to deviate from the proposed oral absorption factor.

For inhaled substances the processes of deposition of the substance on the surface of the respiratory tract and the actual absorption have to be differentiated. A vapor pressure of less than 0.5 KPa (0.19 Pa) and a boiling point above 150°C (222°C) indicate a low volatility. If DBI reaches the tracheobronchial region, it is likely to diffuse/dissolve into the mucus lining of the respiratory tract due to its water solubility and subsequently will be absorbed due to its low molecular weight (242.31) and partition coefficient (3.8). Based on the above data, for risk assessment purposes the inhalation absorption of DBI is set at 100% (ECHA REACH guidance Chapter R.7c, 2014). The oral toxicity data do not provide reason to deviate from the proposed inhaled absorption factor.

DBI is a liquid which is taken up when it comes in contact with the skin. According to the criteria given in the REACH Guidance (ECHA REACH guidance Chapter R.7c, 2014), a default value of 100% dermal absorption should be used unless MW >500 and log Pow <-1 or >4, in which case a value of 10% skin absorption should be chosen. The MW (242.31) and log Pow (3.8) of DBI indicate that absorption is to be expected. It is generally accepted that dermal absorption is not higher that oral absorption, which for DBI is set at 50%. Based on these considerations, for risk assessment purposes the dermal absorption of DBI is set at 50%.

Once absorbed, distribution of the test substance throughout the body is expected based on its water solubility (0.0748 g/L), molecular weight (242.31) and partition coefficient (3.8). Absorbed DBI is most likely excreted via urine (Parkinson, 2001). Based on its partition coefficient (3.8) and water solubility (0.0748 g/L), DBI is not expected to accumulate significantly in adipose tissue.