Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Stability

In the atmosphere a half-life of 21.3 h for TDCP is estimated due to indirect photolysis with hydroxyl radical.

A study revealed that reaction with oxidative species such as ozone or hydroxyl radicals can proceed rapidly, but the paper did not relate the data to typical environmental conditions.

A hydrolysis study revealed that the rate of hydrolysis at environmentally-relevant pH values is fast enough to have any influence on predicted environmental concentrations. The most rapid t1/2 at pH 9 : > 120d at 20 °C.

Biodegradation

TDCP has been shown to be not readily biodegradable in water. No definitive conclusion can be reached regarding inherently biodegradability or biodegradation under anaerobic conditions.

In soil very little degradation (< 6%) occured in a 17 -week study.

Bioaccumulation

The measured BCF of 45 l/kg is used in the risk assessment; this is the arithmetic mean of the range 31 to 59 l/kg. Since the values are in a narrow range, a mean is considered acceptable and representative.

The measured BCF for TDCP is relatively low in comparison with the predictions and with other substances of similar log Kow values. There could be various causes for such a result, including the observed rapid metabolism in the organism.

Adsorption/desorption

For TDCP, good agreement is found between the QSAR predictions of Kocfrom Kow(Koc= 950.8 (range 633.4 – 1427.2) and the value measured in the OECD 106 study (Koc= 1780 (range 1540 – 2010). The HPLC screening estimates of Kocappear to consistently over-estimate this value for the chloroalkylphosphates. For TDCP, the Kocmeasured in the OECD 106 study will be used for the risk assessment, Koc= 1780 log Koc= 3.25.

Henry's law constant

A Henry’s Law constant of 1.24 x 10-4 Pa.m3/mol can be calculated from the vapour pressure and water solubility. This indicates a preference for water compared to air, and hence a low rate of volatilisation from surface water to air.

Additional information

PBT assessment

Persistence

The persistence criteria currently laid down in the TGD require a half-life >60 days in marine water (or >40 days in fresh water) or >180 days in marine sediment (or >120 days in freshwater sediment). The available screening studies show that TDCP is not readily biodegradable so the screening criterion for persistence is met.

Bioaccumulation

The criterion used in the TGD for bioaccumulation is a bioconcentration factor (BCF) >2,000 l/kg. TDCP has a measured fish BCF of 31-59 in the only acceptable result of three studies and hence does not meet the B criterion.

Toxicity

The toxicity criterion used in the TGD is a chronic NOEC <0.01 mg/l or substances classified as Carcinogenic (category 1 & 2), Mutagenic (category 1 & 2), or Toxic to Reproduction (category 1,2, & 3) or with other evidence of chronic toxicity. The lowest aquatic NOEC for TDCP is 2 µg/L from a 6 month development and growth study with the fish Danio rerio. Regarding human health effects, TDCP is classified as Carcinogenic (re-evaluation of existing data as reported in Faust and Meehan, 2011). Based on the current evidence, combined with the aquatic toxicity results, there is clear evidence of chronic toxicity and hence the T criterion has been met.