Registration Dossier

Administrative data

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:
PNEC aqua (freshwater)
PNEC value:
0.004 mg/L
Assessment factor:
10
Extrapolation method:
assessment factor
PNEC freshwater (intermittent releases):
0.005 mg/L

Marine water

Hazard assessment conclusion:
PNEC aqua (marine water)
PNEC value:
0 mg/L
Assessment factor:
100
Extrapolation method:
assessment factor

STP

Hazard assessment conclusion:
PNEC STP
PNEC value:
0.3 mg/L
Assessment factor:
10
Extrapolation method:
assessment factor

Sediment (freshwater)

Hazard assessment conclusion:
PNEC sediment (freshwater)
PNEC value:
0.147 mg/kg sediment dw
Extrapolation method:
equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:
PNEC sediment (marine water)
PNEC value:
0.015 mg/kg sediment dw
Extrapolation method:
equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:
no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:
PNEC soil
PNEC value:
0.027 mg/kg soil dw
Extrapolation method:
equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
no potential for bioaccumulation

Additional information

Conclusion on classification

ZMBT is an organic complex, in which MBT structure is present. Meanwhile MBT is often found as impurity in ZMBT with variable percentage. The dissolution of MBT determines the hazard profile of ZMBT aqueous solution; and hence a read-across approach from MBT is used to support the risk assessment of ZMBT as a worst-case. No valid data with ZMBT as test substance are available for the aquatic ecotoxicity. The same environmental classification as MBT is therefore recommended to ZMBT as a worst case.

According to Directive 67/548/EEC and the regulation (EC) No 1272/2008, MBT is legally classified as "Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment" with the phrase of R 50/53 in Annex I and aquatic acute 1 (H400) and aquatic chronic 1 (H410), respectively. The up-to-date information summarised above confirmed this classification and is listed below:

- The most sensitive acute toxicity of MBT is to aquatic algae (Selenastrum capricornutum): 72h-ECr50 of 0.5mg/L (MITI, 1999), which is lower than 1 mg/l.

- The most sensitive chronic toxicity of MBT was determined in a long-term study with fish (rainbow trout): NOEC (89d) of 0.041 mg/L (CMA, 1989), which is lower than 0.1 mg/L.

- MBT is not readily biodegradable (MITI, 1992).

With the data listed above, MBT should be classified as aquatic acute 1 (H400) and aquatic chronic 1 (410) according to GHS (Regulation EC 1272/2008) and as R50/53 according the Directive 67/548/EEC. The appropriate multiplying factors for acute and chronic toxicity are both 1.