Registration Dossier

Environmental fate & pathways

Phototransformation in water

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

TBBPA’s rate of decomposition in water under UV irradiation (k x 10³ (s^-1)) ranged from 0.7 (at pH = 10) to 0.033 (at pH = 5.5). Its half-life ranged from 16 (at pH = 10) to 350 (at pH = 5.5) minutes; TBBPA’s half-life at pH 7.4 = 24 minutes. The disappearance quantum yield ranged from 0.045 (pH = 10) to 0.018 (pH = 5.5). 

Key value for chemical safety assessment

Half-life in water:
24 min

Additional information

A method was developed for studying the phototransformation following UV irradiation of aqueous solutions of tetrabromobisphenol A (TBBPA) and related compounds at various pHs. The absorbance spectra of the compound and the emission spectra of the light-source were determined and used to calculate disappearance quantum yields of the photochemical reactions that were taking place.

The rates of decomposition were determined at a concentration of 77 µM in water with an illumination time of 50 minutes. Fluorescent tubes provided the irradiation, and were intended to represent the range of solar UV wavelengths that penetrate the atmosphere. 

TBBPA’s rate of decomposition in water under UV irradiation (k x 10³ (s^-1)) ranged from 0.7 (at pH = 10) to 0.033 (at pH = 5.5). Its half-life ranged from 16 (at pH = 10) to 350 (at pH = 5.5) minutes; TBBPA’s half-life at pH 7.4 = 24 minutes.  The disappearance quantum yield ranged from 0.045 (pH = 10) to 0.018 (pH = 5.5). 

The data indicated that TBBPA was readily photodegraded in aqueous solution. Degradation rates were sensitive to pH; the rate of decomposition of TBBPA was six times higher at pH 8 than at pH 6.

TBBPA decomposed via cleavage between the isopropyl group and one of the benzene rings. Identification of the degradation products of TBBPA by GC–MS analysis and by comparison to synthesised reference compounds indicated that three isopropylphenol derivatives (4-isopropyl-2,6-dibromophenol, 4-isopropylene-2,6-dibromophenol and 4-(2-hydroxyisopropyl)-2,6-dibromophenol) were major degradation products of TBBPA.