4-tert-butylphenol

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Persistence Assessment

The substance has shown to be readily biodegradable in one test (OECD 301 A) and in two other tests failed to pass the 10 day window criterion, although showing a significant aerobic biodegradation of 60% within 28 days (OECD 301B-test, OECD 301F-test). However, clearly the substance is biodegradable and therefore does not fulfill the criteria for persistence in the environment. A modified MITI-test suggested that ptBP could not be considered as inherently biodegradable but this result may be attributable to the inhibitory concentration of ptBP used resulting in a long lag phase under the test conditions. Hydrolysis is not expected under relevant environmental conditions (no experimental data) and from the structure of the substance it can be deduced that it does not undergo abiotic degradation through hydrolysis. According to Regulation (EC) No 1907/2006 (REACH) ANNEX XIII and the Guidance on information requirements and chemical safety assessment, Chapter R.11 (PBT Assessment, May 2008), the substance does not fulfill the screening criterion “persistent (P)” and “very persistent (vP)” as within an OECD 301A study the substance showed to be degradable at a rate of 98% determined by DOC-removal within 28 days. The substance can be considered as readily biodegradable but failing the 10-day window.

Bioaccumulation Assessment

According to Annex XIII of Regulation (EC) No 1907/2006 and to the Guidance on information requirements and chemical safety assessment Chapter R.11 (PBT Assessment, May 2008), a substance does not fulfill the criterion “bioaccumulative (B)” or “very bioaccumulative (vB)” if the BCF is below 2000 or 5000 respectively or the log Kow is below 4.5. The bio concentration factor of p-tert. butyl phenol was determined to be 20-43 upon exposure of 40 mg/l and 38-88 upon exposure to 4 µg/l as determined by the Ministry of Trade and Industry (MITI) in Japan according to an OECD 305C guideline test. The log POW value determined by HPLC method (OECD 117) was found to be 3 (at 23 °C and pH of 5.7). Consequently, both the logPOW as well as the BCF values determined for para tert.butyl phenol were found to be well below the screening criteria as defined in Annex XIII of the REACH regulation and a potential for bioaccumulation is not expected. According to Guidance on information requirements and chemical safety assessment (May 2008), Chapter R.11, Figure 11-2: Integrated testing strategy for B-assessment, no further testing is required to conclude on the bioaccumulation criterion.

Toxicity Assessment

The substance is classified as toxic for reproduction (category 2) according to Regulation (EC) NO. 1272/2008 and classified as Cat. 3

(developmental effects) as set out in Directive 67/548/EEC.