Potassium tert-butanolate

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

The predicted log Kow for Potassium tertiary butoxide (KTB), from a valid EPI suit assessment is Log Kow -1.82.  This very low Log Kow (<4.5) is an indication that the substance is likely to remain in water and not transfer into fats or lipids and is unlikely to be bioaccumulative (not B or vB). In addition Potassium tertiary butoxide is not stable and decomposes rapidly in water to Potassium hydroxide and tertiary butanol.  The predicted bio concentration factor (BCF predicted from valid EPI suit) is extremely low at 3.162  L/kg.  This is well below the > 2000 L/kg threshold which again indicates not B or vB.  Potassium tertiary butoxide is therefore not B or vB. 

 

With respect to the persistency the predicted Biowin 3 (ultimate survey model) degradation rate is 2.82 (weeks) and an indication that the substance will biodegrade readily.  The Biowin 5 (MITI Linear model) probability is greater 0.5 (estimated probability 0.56) giving an indication that the substance will biodegrade fast.  The screening results indicate that the substance is readily biodegradable and so the overall assessment of the EPI suit predictions is that the substance is not P or Pv.

 

With respect to toxicity the substance is not classified as carcinogenic (cat 1A or 1B), cell mutagenic (category 1A or 1B) or toxic for reproduction (category 1A, 1B or 2) in accordance with EC No. 1272/2008.    For a substance to be classified as PTB (Persistent, Toxic and Bioaccumulative) or vPTB (vey Persistent, very Toxic and very Bioaccumulative) the substance must meet all three criteria.  The environmental screening assessment of shows that the substance KTB does not meet the criteria for classification as PTB or vPTB

Likely routes of exposure:

Because the substance does not fulfill the PBT and vPvB criteria, no emission characterisation is performed.