Triphenyl phosphate

Endpoint summary

Description of key information

Stability

As the half-life of TPP in air was calculated to be 35.5 h it is not expected to have a potential for long range atmospheric transport.

Regarding hydrolysis the key study gave half lives of 3 days at pH 9, 19 days at pH 7 and >28 days at pH 5 at 25 °C.

A direct photolysis study was conducted for TPP in which TPP was rapidly degradated by irradiation with a half life of 1.04 minutes at both pH 3 and 10.

Biodegradation

In a test on ready biodegradability 83 -94% of the applied TPP was degraded after 28 days of incubation. Thus TPP can be classified as readily biodegradable. Similarly, in a test simulating of an aerobic sewage treatment plant a mean elimination rate of 93.8% was determined after 20 days.

Other studies have given similar results showing that TPP is readily degraded in water/sediment systems. TPP can also be degraded under anaerobic aquatic conditions in the presence of river sediment.

In soil under aerobic conditions, the amount of TPP decreased steadily with time and accounted for 46.6% of that applied after 32 days. However, degradation slowed and 20.2% of the applied test substance was recovered after 101 days. In heat sterilized soil under the same conditions mainly unchanged TPP was recovered after 101 days incubation. This indicates that the degradation in soil is mostly microbial. Under anaerobic conditions in soil degradation was equally rapid and extensive as under aerobic conditions as the amount of extractable radioactivity represented 35.8% of the applied dose after 102 days. Under aerobic conditions a DT50 of 37 days can be calculated and under anaerobic conditions 21 days.

The results obtained show that TPP is unlikely to be persistent in the environment.

Bioaccumulation

Uptake of TPP in Oryzias latipes, Killifish, was rapid and increased gradually over time giving a BCF of about 60 after 2 days and 144 after 18 days. After transferring the fish to clean water fast elimination occured and concentration of TPP is below the detection limit within 24 hours. The biological half-life is 1.2 h.

On the basis of the results of this and other studies, a moderate potential for the biaccumulation of TPP can be assumed.

Transport and Distribution

The adsorption/desorption coefficients for TPP indicate that it is strongly bound to soil and is unlikely to leach to any great extent (log Koc 3.5). Studies with sediment water systems also show that TPP has a greater affinity for the sediment compared to the water phase. These experimental results are confirmed by calculations based on the Mackay fugacity model which gives a global distribution of TPP with 43.9% in soil, 41% in sediment and 14.3% in water.

Monitoring data

Monitoring studies have been carried out on rivers and on the air quality of houses, public buildings and outside

The level of TPP in the river Ruhr increased from values below the limit of detection at its source to values of 200 ng/L in the Dortmund region. In two tributaries values of 400 ng/L were found. Even higher values were found in a creek dominated by asewage works (2000 ng/L) and in the river Emscher (3400 ng/L). However, bankfiltered ground water contained <1ng/L - the detection limit.

Indoor and outdoor triphenyl phosphate concentrations were below 0.01 µg/m3. Even in the air of several buildings which were thought to contain  triphenyl phosphate containing materials, no triphenyl phosphate was found. In particulate matter from public buildings, a maximum of 220 mg triphenyl phosphate/kg was measured, but all other results were <= 3 mg/kg.