Tar acids, 3,5-xylenol fraction

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Persistence (P):

According to the criteria stated in Regulation (EC) 1907/2006, Annex XIII, persistence can be determined through the evaluation of the dissipation half-lives of a substance in different environmental compartments. The persistence of tar acids, 3,5 -xylenol fraction in water, sediment and soil can be estimated using data from single isomers. With regard to its chemical structure cresols and xylenols are not expected to hydrolyse, but they will be photolytically degraded in water (half-lives 11-21 days) and in the atmosphere (half-lives about 3.8-9 hours). Cresols are also readily biodegradable in water/sediment and soil systems (BOD of 80-95% within 40 days; Desai, 1990). Xylenols are inherently biodegradable. Thus, cresols are not expected to persist in the environment and the P criterion is not met.

Bioaccumulation (B):

Xylenols, m-Cresol and o-cresol are not expected to bioaccumulate, as the experimental BCF values are 20 and 10.7 (Freitag et al. 1985; Butte et al., 1987). Since p-cresol has a log Kow of 1.94 it is also judged to have a low bioaccumulation potential. Based on this information the substance does not meet the B criterion.

Toxicity (T):

According to the criteria stated in Regulation (EC) 1907/2006, Annex XIII, the toxicity of a certain substance can be assessed based on the available toxicity data on aquatic organisms and mammals. The xylenols and cresols are not toxic due to due to NOECs ranging between 3 and 0.3 mg/L (Falk-Petersen et al. 1985). Furthermore, cresols are not classified as carcinogenic, mutagenic or toxic for reproduction or R48. For these reasons, the cresols do not meet the T-criterion.