4,4'-cyclohexylidenedi-o-cresol

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

528 ng/L

Assessment factor:

1 000

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

5.28 µg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

52.8 ng/L

Assessment factor:

10 000

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

10 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

0.022 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

2.23 µg/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:

4.15 µg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

0.033 g/kg food

Assessment factor:

300

Additional information

The available aquatic toxicity dataset for dimethyl cyclohexyl bisphenol (DMBPC) consists of short-term toxicity assays for fish, daphnia and algae. No long-term data are available. For fish, an assay performed according to U.S. EPA OPPTS 850.1075 (Freshwater and Saltwater Fish Acute Toxicity Test) found a 96-hour LC50 of 528 µg/L (95% CI: 410 – 681 µg/L) for Oncorhynchus mykiss (rainbow trout) (Ward et al., 2001a). For the aquatic invertebrate Daphnia magna (water flea), a 48-hour EC50 of > 1084 µg/L was reported in an assay performed according to U.S. EPA OPPTS 850.1010 (Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids) (Boeri et al., 2000). For algae, Ward et al. (2001b) conducted an assay according to U.S. EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) with the green algae (Selenastrum capricornutum) and reported a 96-hour EC50 > 1165 µg/L (based on biomass or growth rate) and 96-hour No-Effect Concentrations (NOECs) of 595 and 161 µg/L based on biomass and growth rate, respectively.

The most sensitive species is O. mykiss, with a short-term reference value of 528 µg/L (Ward et al., 2001a). With results from three short-term tests from three trophic levels (fish, aquatic invertebrates and algae), the assessment factor is 1000.

Therefore, the PNECwater is equal to 528 µg/L / 1000 = 0.528 µg/L = 528 ng/L.

For calculation of the PNECmarine, according to Chapter R.10 of ECHA (2008), an assessment factor of 10,000 should be applied when short-term data for three trophic levels of freshwater organisms are used to derive the marine PNEC. As short-term freshwater data are available for fish, aquatic invertebrates and algae, an assessment factor of 10,000 was used in the derivation of the PNECmarine.

Therefore, the PNECmarine is equal to 528 µg/L / 10,000 = 0.0528 µg/L = 52.8 ng/L.

The PNEC for water in the case of intermittent releases (PNECwater,intermittent) is derived based upon short-term L(E)C50 values (Chapter R.10 of ECHA, 2008). The PNECwater,intermittent is normally derived by application of an assessment factor of 100 to the lowest L(E)C50 of at least three short-term tests from three trophic levels. Short-term tests were conducted with fish, aquatic invertebrates and algae with L(E)C50 values of 528, >1084 and >1165 µg/L, respectively. The lowest short-term value is the result of the test with O. mykiss (528 µg/L) and this is conservatively used to derive PNECwater,intermittent.

The PNECwater,intermittent is equal to 528 µg/L / 100 = 5.28 µg/L.

The PNECwater,intermittent is only applicable if the endpoint is based on emissions from batch productions when environmental exposure is limited in time (ECHA Guidance R.10.3.3). If processes are continuous processes, the PNEC intermittent releases endpoint is not relevant and the PNECwater,intermittent can be waived.

The available toxicity to microorganisms dataset consists of a single study in which activated sludge of a predominantly industrial sewage was treated with DMBPC for 20-30 hours at mean nominal concentrations of 50 and 200 mg/L in a study conducted according to OECD Test Guideline 209. Oxygen uptake of the biomass was measured over time in 16 replicate testing vessels. A 30-d EC50 of >100 and >200 mg/L was reported for typical municipal sludge and industrial sludge, respectively (Lockwood, 2001). As a conservative measure, the EC50 for municipal activated sludge, the lower of the two values, >100 mg/L, is taken as the reference concentration. Further, the reference concentration is taken to be 100 mg/L as a conservative measure. Per Chapter R.10 of ECHA (2008), an AF of 10 is applicable based on a long-term NOEC.

PNECmicroorganisms = 100 mg/L / 10 = 10 mg/L

References:

Boeri, R. L., Wyskiel, D. C. and Ward, T. J. 2000. Static, Acute Toxicity of DMBPC to the Daphnid, Daphnia magna. Wilbury Laboratories, Inc., Marblehead, MA, USA. Repot no.: 1997. 2000-06-07.

European Chemicals Agency (ECHA). 2008. Guidance on information requirements and chemical safety assessment. Chapter R.10: Characterisation of dose [concentration]-response for environment. May 2008.

Ward, T. J., Wsykiel, D. C. and Boeri, R. L. 2001a. Flow-Through, Acute Toxicity of DMBPC to the Rainbow Trout, Oncorhynchus mykiss. T.R. Wilbury Laboratories, Inc., Marblehead, MA, USA. Report No.: 2150. 2001-10-14.

Ward, T. J., Wyskiel, D. C. and Boeri, R. L. 2001b. Toxicity of DMBPC to Freshwater Alga, Selenastrum capricornutum. T.R. Wilbury Laboratories, Inc., Marblehead, MA, USA. Report no.: 2149. 2001-10-14.

Conclusion on classification

The available aquatic toxicity dataset for DMBPC consists of short-term toxicity assays for fish, aquatic invertebrates and algae. The most sensitive species is the rainbow trout (O. mykiss), with a 96-hour LC50 of 528 µg/L or 0.528 mg/L (T.R. Wilbury Laboratories, Inc., 2001a). This toxicity value is used for classification by comparing to the aquatic toxicity cut-off values for classification. Since the acute value (0.528 mg/L) is < 1 mg/L, DMBPC is classified as Acute Category 1 for aquatic toxicity according to the GHS/CLP and assigned the hazard statement H400: Very toxic to aquatic life.

No long-term data are available for DMBPC; however, according to the GHS/CLP guidelines, in the absence of long-term data, substances classified as Category 1 acute aquatic toxicants are also classified as chronic aquatic toxicants when at least one of the following criteria are met:

• the substance is not rapidly degradable;

• the experimentally determined BCF ≥ 500 L/kg; or

• the log Kow ≥ 4.

The experimentally-determined log Kow for DMBPC is 3.1 at 25 °C (RCC Ltd., 2001g) and experimentally determined BCF values for C. carpio are 76 and 83 L/kg (Institute of Ecotoxicology, Ltd., 2003); therefore, these criteria are not met. However, the results from three biodegradabiltiy studies (Lockwood SH, 2001b; Institute of Ecotoxicology, Ltd., 2002; Kurume Laboratory, 2001) clearly indicate that DMBPC is not readily biodegradable and, therefore, DMBPC is classified as a Category 1 chronic aquatic toxicant and assigned the hazard statement H410: Very toxic to aquatic life with long lasting effects.