4-(1,1,3,3-tetramethylbutyl)phenol

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.001 mg/L

Assessment factor:

5

Extrapolation method:

sensitivity distribution

PNEC freshwater (intermittent releases):

0 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.001 mg/L

Assessment factor:

5

Extrapolation method:

sensitivity distribution

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

0.1 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

4.62 mg/kg sediment dw

Assessment factor:

50

Extrapolation method:

assessment factor

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

1.23 mg/kg sediment dw

Assessment factor:

50

Extrapolation method:

assessment factor

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

2.3 mg/kg soil dw

Assessment factor:

10

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

2.36 mg/kg food

Assessment factor:

30

Additional information

Oestrogenic Effects Summary

It has been shown that octylphenol can exhibit oestrogenic effects on aquatic organisms. The Environment Agency Environmental Risk Evaluation Report: 4-tert-Octylphenol (EA 2005) found that reliable (fully valid, according to EA, 2005) data indicate the lowest NOEC for oestrogenic effects of octylphenol in aquatic organisms was 12 ug/L but effects such as vitellogenin (VTG) induction can occur at concentrations above 1.6 ug/L. The following discussion is a summary of the studies reviewed and noted as “valid” in the EA 2005 Report. While a draft risk assessment report for nonylphenol and octylphenol prepared by the Environment Agency for England and Wales was made available, the results presented below were obtained from the peer-reviewed EA 2005 Report.  The draft Environment Agency report, mentioned above, presented the EA 2005 Report results only and did not present any additional results. In addition, a literature search was performed to obtain any reliable relevant data for endocrine disrupting effects of octylphenol published after September 2008. A summary of those studies are also included.  In vitro studies and studies involving injection-type exposures were not considered environmentally relevant (based on exposure route) and not discussed here.

Zebrafish (Danio rerio):

Wenzel et al. (2001) exposed fertilized eggs, in a life-cycle test, to measured concentrations of OP in a flow through system. Significant effects, time to fist spawn, total number of eggs/female/day, and fertilization, were found at exposure concentration of 35 ug/L OP. Therefore, the NOEC was determined to be 12 ug/L for all effect parameters. Other studies with the same species agree with these results. Segner et al. (2003) determined an EC50 of 28 ug/L when exposing zebrafish to OP in a flow through system during a lifecycle test. Van den Belt et al. (2001) exposed adult zebrafish for three weeks and determined a NOEC of 100 ug/L. EA (2005) Report notes that the difference in results may be due to life stages tested.

Rainbow Trout (Oncorhynchus mykiss):

After adult males were exposed for 21 days in a flow through system, Jobling et al. (1996) found the NOEC for VTG induction was 1.6 ug/L OP. However, there were no significant gonadal size differences in any of the test concentrations. Routledge et al. (1998) exposed the adult males for 21 days and reported a NOEC of 10 ug/L when for the same effect.

Other fish species:

Adult male and female Roach (Rutilus rutilus) were exposed separately in a flow through system (Routledge et al., 1998).  The NOEC, based on VTG levels, for the female test was reported as >100 ug/L, but for the male test, the NOEC based on VTG levels, was reported as 10 ug/L. Toft and Baetrup (2001) exposed adult male Guppies (Poecilia reticulate) in a flow through system for 30 and 60 days. Results indicated a significant increase in sperm count at 100 and 300 ug/L OP. Toft and Baetrup (2003) also exposed up to 6 day old Guppies for 90 days and found significant mortality, gonadopodium length, and GSI in females at the measured concentration of 149 ug/L, but not at 11.7 ug/L. Kinnberg and Toft (2003) exposed adult male Guppies for 30 to 60 days in a flow through system. The NOEC, based on mortality, was reported as 300 ug/L. Gronen et al. (1999) found significant effects (NOEC <20ug/L) in eggs produced per day when male Japanese medaka (O. latipes) were exposed for 120 days and then transferred to clean water for 9 days and mated with unexposed females. Seki et al. (2003) exposed fertilized eggs of Japanese medaka for 60 days post hatch. The NOEC was reported to be 6.94 ug/L after assessment of testis-ova and VTG levels.  Knorr and Braunbeck (2002) found increased mortality, compared to controls, for offspring of exposed Japanese medaka mated with control fish exposed at 20 ug/L OP. For marine fish, Robinson et al. (2004) exposed the Sand Goby (Pomatoschistus minutus) for 28 days and determined the NOEC, based on VTG levels, to be 20ug/L. Karels et al. (2003) exposed 8-9 month old Sheepshead Minnow (Cyprinodon variegates) for 24 days. Significant increase in VTG levels was found at the lowest test concentration of 11.5 ug/L.

Other aquatic organisms:

The EA (2005) Report summarizes studies performed using African clawed frog (Xenopus laevis), Bullfrog (rana catesbeiana), Leopard frog (rana pipiens), and Snapping turtle (Chelydra serpentine). However, these studies were all noted as “use with care”. Only one study, performed using the Streamside salamander (Ambystoma barbouri), was noted as “valid”. Rohr et al. (2003) exposed salamander eggs for 35 days in a static renewal system. Results indicated significant effects on time to hatch, larval survival and snout-vent length at 500 ug/L (NOEC 50 ug/L).    There were no valid studies on aquatic macroinvertebrates presented in the EA (2005) Report.

Post-September 2008 Literature Review:

Croteau et al. (2009) exposed newly hatched tadpoles (Rana pipiens) to two concentrations of OP (0.01nM and 10 nM) for eight months to assess effects on potential thyroid-based function. It was reported that the percent of tadpoles developing past the median stage (Gosner stage 29) was significantly lower than the controls when exposed to 0.01 nM (0.0021 ug/L) OP. Results from this study should be used with care as concentrations were not analytically verified and purity and source of test chemical is unknown.  Vazquez et al. (2009) exposed adult male and female South American Cichlid (Cichlasoma dimerus) to OP for 60 days under semi-static conditions. Levels of VTG levels in surface mucus and plasma and histological alternation in the liver and gonads were the measured endpoints. VTG was detected in all exposed male fish at the lowest measured concentration of 30 ug/L OP. Testicular structure impairment was seen only in males exposed to 300 ug/L OP. Bjerregaard et al. (2008) exposed juvenile Brown Trout (Salmo trutta) to measured concentrations of OP in a flow through system for seven days. It was report that the EC50, based on VTG induction in plasma was 7 ug/L OP. The NOEC based on VTG levels in the liver was reported as 7.8 ug/L. Results of these studies are in agreement with studies reported and summarized in the EA (2005) Report. Reliable studies investigating oestrogenic effects of PTOP to terrestrial organisms were not found.

Conclusion:

The EA( 2005) Report found that reliable (fully valid, according to EA 2005) data indicate the lowest NOEC for oestrogenic effects of octylphenol in aquatic organisms was 12 ug/L but effects such as vitellogenin (VTG) induction can occur at concentrations above 1.6 ug/L. The calculated PNEC_aquatic, as presented in this CSR Report, is 0.632 ug/L OP and therefore, likely protective of oestrogenic effects exerted by octylphenol.

Conclusion on classification

Following the PBT assessment, octylphenol (PTOP) does not fulfil the screening criteria for bioaccumulation (B-criterion). Screening data show that PTOP can be regarded as inherently biodegradable, although a conservative approach suggests that octylphenol may be considered potentially persistent as the half-life for octylphenol for biodegradation in seawater is equivalent to the persistence screening criteria (P-criterion) of 60 d. PTOP is considered to be toxic to aquatic organisms but the T-criterion was not met for avian toxicity. The overall conclusion is that octylphenol does not meet the PBT or vPvB criteria. No further testing or an emission characterization and risk characterization according to REACH Article 14 (4) is required.