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Environmental fate & pathways

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The environmental fate properties of the diphenyl isodecyl phosphite (DPDP) and related phenyl/alkyl phosphites generally include: low water solubility, low vapor pressure, and rapid hydrolysis to phosphorous acid and corresponding alcohols (in the case of DPDP it is phenol and isodecanol).

These phosphite substances have demonstrated a high capacity to biodegrade in recent OECD 301D studies. In a recent study by van Ginkel (2015) on Triphenyl Phosphite (TPP), a significant constituent of DPDP, the 28 -day degradation results were 84%. This study also met the 60% criterion for ready biodegradable. The mode of action is thought to be rapid hydrolysis of the phosphite (abiotic degradation) to the alcohol components and biodegradation of the alcohols. Prior studies that showed poor biodegradation are no longer considered to be valid as it appears that the test system did not properly address the poor water solubility of the phosphites.

Reliable bioaccumulation concentration factor (BCF) estimates for DPDP are difficult to obtain due to the rapidly hydrolysis. However, it is because of this rapid hydrolysis that the potential for bioaccumulation is expected to be very low. BCF values from the BCFBAF v3.00 model for DPDP are not considered reliable because they do not consider hydrolysis or biotranformation of the substance. The BCF of phenol (the primary hydrolysis product) is 17.5 L/Kg (EU Phenol RAR 2006) and the BCF of isodecanol is 131 L/kg (EPISuite 4), indicating that neither DPDP nor its hydrolysis products are expected to bioaccumulate and do not meet the criterion of B or vB.

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