Objective
To assess environmental stability of 10-(2, 5-dihydroxyl phenyl)-10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-HQ) as a potential alternative to polybrominated diphenyl ethers (PBDEs).
Methods
According the requirement of Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) by the European Union, the hydrolysis and biodegradation of DOPO-HQ were evaluated by Organization for Economic Cooperation and Development (OECD) guidelines such as Hydrolysis as a Function of pH (OECD111), Manometric Respirometry Test (OECD301F), and Inherent Biodegradability:Modifed MITI Test (OECD302C); and the results were compared with those of PBDEs.
Results
In pH7.0 and pH9.0 buffers, DOPO-HQ was rapidly hydrolyzed with a halftime of hydrolysis less than 2 h. In pH4.0 buffer, the hydrolysis was a first-order reaction, and the hydrolysis rate increased with higher temperature. The halftime of hydrolysis were 866, 201, and 47 h at 20℃, 35℃, and 50℃, respectively. The results of ready biodegradability test evaluated by biochemical oxygen demand (BOD) showed that DOPO-HQ had no ready biodegradability after 28 d with a biodegradability rate of 6.13%. However, according to the inherent biodegradability test results with mixture inoculums from many sites, DOPO-HQ showed primary degradability with a chemical residue rate of 8.8% after 28d. The BOD results showed no biodegradability of DOPO-HQ for the first 20d, and the biodegradability rate obviously increased after 20d and reached 12.7% after 28d, implying slow inherent biodegradability.
Conclusion
DOPO-HQ shows varied hydrolysis properties under different pH conditions and rapid hydrolysis under neutral and basic conditions. At the same time, it shows inherent biodegradability. Compared with PBDEs, the weaker persistence of DOPOHQ is identified, thus it could be a potential alternative to PBDEs.
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