N-butyl phenyl ether

Endpoint summary

Description of key information

In vitro Skin and Eye irritation assays (Epiderm and EpiOccular) on Butyl Phenyl Ether

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: OECD Guideline study performed in accordance with GLP requirements (but not a GLP study).

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Version / remarks:

This is a screening non-GLP study. The current protocol is a streamlined version of OECD TG 439 test guideline.

Deviations:

no

GLP compliance:

no

Remarks:

THe study was conducted in accordance with the principles of GLP (reporting, data auditing, data retention, GLP qualification fo all equipment and study personel) but was not officially conducted as a GLP study.

Specific details on test material used for the study:

Test Material Name: Butyl phenyl ether
Chemical Name: Butoxybenzene
Lot/Reference/Batch Number: 22466
Purity/Characterization (Method of Analysis and Reference): The purity of the test material was determined to be 99.41% ± 0.01% by gas chromatography after correction for water content. Identification was by gas chromatography mass spectrometry and Fourier transform infrared spectroscopy (Ferruzzi, 2016a).
Test Material Stability Under Storage Conditions: Butyl phenyl ether, lot 22466, was determined to be stable for 2 weeks at 54°C which is equivalent to 24 months under ambient storage conditions as tested under U.S. EPA OPPTS Guideline 830.6317. (Ferruzzi, 2016b).

Test system:

human skin model

Source species:

human

Cell source:

other: human-derived epidermal keratinocytes (NHEK)

Justification for test system used:

The EpiDerm three-dimensional human skin model has been extensively characterized (EC-ECVAM, 2009) and is approved (OECD TG 439, 2013) for identification and classification of skin irritation hazard according to the UN GHS and EU classification system (Category 2/R38 or No label).

Vehicle:

unchanged (no vehicle)

Details on test system:

TEST SYSTEM:
The potential for chemically induced skin irritation and corrosion are important considerations in establishing procedures for the safe handling, packing, and transport of chemicals (UN, 2007). The EpiDerm three-dimensional human skin model has been extensively characterized (EC-ECVAM, 2009) and is approved (OECD TG 439, 2013) for identification and classification of skin irritation hazard according to the UN GHS and EU classification system (Category 2/R38 or No label). The EpiDerm model uses human-derived epidermal keratinocytes (NHEK) as the cell source, which are cultured to form a multi-layered, highly differentiated model that closely mimics human epidermis at biochemical and physiological levels.
The test is based on the principle that chemicals with irritant potential can cause a cytotoxic response to the stratum cornea and the rate of cytotoxicity is proportional to irritation potency. In the assay, the EpiDerm tissue model was incubated with the test chemical for 60 minutes, followed by 42-hour incubation (recovery) under standard cell culture conditions. Following the post-treatment incubation period, cell viability was assessed using the MTT (3-[4,5- dimethylthiazol-2-yl] -2,5 – diphenyltetrazolium bromide) assay (Mosmann, 1983). Relative cell viability was calculated for each tissue as % of the mean of the negative control-treated tissues. A test chemical was interpreted as a potential skin irritant (UN GHS Cat 1/2) or non-irritant (UN GHS Cat NC), when the cell viability was ≤ or > 50%, respectively (OECD TG 439, 2013).

STUDY DESIGN:
The EpiDerm System (EPI-200) consists of normal, human-derived epidermal kerotinocytes which have been cultured to form a multi-layered, highly differentiated model of the human epidermis. It consists of organized basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo. The EpiDerm tissues are cultured on polycarbonate membranes of cell culture inserts (MILLICELLs, 10 mm diameter, 0.6 cm² surface) and shipped as kit, containing 24 tissues mounted on agarose.

Supplier and Location:
MatTek Corporation; Ashland, MA.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

Preparation of the Treatment Solution:
The chemical was tested at a concentration of 100% (neat/as provided), following supplier’s protocol (EpiDerm SOP) and OECD 439 test guideline. Thirty microliter of undiluted Butyl phenyl ether was directly dispensed atop the tissue.

Route of Administration:
The test chemical was administered by topical application to the surface of the EpiDerm tissues.

Experimental Procedure:
EpiDerm tissue cultures were used within 24 to 48 hours of receipt from the supplier. Upon receipt, the EpiDerm tissues were stored at 2-8ºC until used. On the day prior to testing, EpiDerm assay medium was warmed to room temperature and an aliquot of 0.9 mL was dispensed into each well of a 6-well plate. The EpiDerm tissues were transferred from a 24-well shipping plate to a 6-well plate containing the fresh, pre-warmed assay medium. Prior to transferring, each EpiDerm tissue was inspected for air bubbles between the agarose gel and MILLICELL insert. Tissues with air bubbles greater than 50% of the MILLICELL area were discarded. Any unused tissues were stored in an air tight bag (filled with 5% CO2/95% air) and stored at 2-8ºC for subsequent use. The EpiDerm tissues were incubated at approximately 37ºC in a humidified atmosphere of approximately 5% CO2 for 60 ± 5 min. At the end of the first pre-incubation period, the inserts were transferred into wells containing fresh warm assay medium and were incubated overnight (18 ± 3 hrs) to acclimate the tissue.
On the day of treatment, the EpiDerm tissues were exposed to the test chemical as described above (30 μL of test material or controls). After dosing, the tissue plates were transferred to a cell culture incubator and were incubated for 35 ± 1 minutes at standard culture conditions. Following incubation, the plates were transferred to the laminar flow hood and incubated at room temperature for 25 minutes. Following the total of 60 ± 1 minutes treatment period, the tissues were rinsed with sterile DPBS to remove test substance. The tissues were then transferred to new 6-well plates containing 0.9 mL/well fresh pre-warmed assay medium and incubated at standard culture conditions for an initial post-treatment incubation of 24 ± 2 hours. After the initial post-treatment incubation, the inserts were transferred into new 6-well plates pre-filled with 0.9 mL fresh pre-warmed assay medium and incubated for additional 18±2 hours (total post-treatment incubation period of 42 ± 2 hours).
Following post-treatment incubation, tissue inserts were evaluated for cell viability using the MTT assay. Each tissue insert was transferred to a well containing 300 μL MTT solution in a 24-well plate and tissues were incubated for 3 ± 0.1 hr at standard cell culture conditions. After incubation the tissues were washed with DPBS and formazan was extracted in 2 mL extractant solution with 2 hours shaking at room temperature. The amounts of extracted formazan from each tissue was measured spectrophotometrically at 570 nm (OD570) using a Microplate Reader (Molecular Devices).

Duration of treatment / exposure:

60 ± 1 minutes treatment period

Duration of post-treatment incubation (if applicable):

Following the total of 60 ± 1 minutes treatment period, the tissues were rinsed with sterile DPBS to remove test substance. The tissues were then transferred to new 6-well plates containing 0.9 mL/well fresh pre-warmed assay medium and incubated at standard culture conditions for an initial post-treatment incubation of 24 ± 2 hours. After the initial post-treatment incubation, the inserts were transferred into new 6-well plates pre-filled with 0.9 mL fresh pre-warmed assay medium and incubated for additional 18±2 hours (total post-treatment incubation period of 42 ± 2 hours).

Number of replicates:

Three

Irritation / corrosion parameter:

other: Mean Viability %

Run / experiment:

Mean Viability % for 3 replicates

Value:

88.6

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

Assessment of Direct Test Material Reduction of MTT:
As some test chemicals may interfere with MTT assay readout by directly reducing MTT dye (turn MTT solution to blue/purple formazan in the absence of viable cells), Butyl phenyl ether was evaluated for this property. In this experiment, Butyl phenyl ether (30 μL) was incubated with 1 mL of the MTT reagent in the dark at standard cell culture conditions (37°C) for 60 min. Untreated (no test material) MTT medium was used as the negative control. Results from this experiment suggested no direct reduction of MTT dye by Butyl Phenyl Ether, as the test material did not turn MTT solution to blue/purple colour.

ACCEPTANCE CRITERIA:
The results for negative and positive controls met assay acceptance criteria, suggesting appropriate conduct of the study.
1) The corrected mean OD570 value of the negative control tissues (exposed for 60 minutes) was 2.37 (i.e. ≥ 1.00; criteria set by the tissue manufacturer).
2) The relative mean viability of positive control (5% SDS) was 36.0% (i.e. <50% compared to negative control).

Interpretation of results:

GHS criteria not met

Conclusions:

The mean relative tissue viability for EpiDerm tissues treated with Butyl phenyl ether and positive control (5% SDS) were 88.6% and 36.0%, respectively. According to the EpiDerm skin irritancy prediction model, a test substance is considered irritant to skin if the mean tissue viability is ≤ 50%. Therefore, based on the present EpiDerm study results, Butyl phenyl ether was interpreted to be a non-irritant (UN GHS Cat NC) to skin.

Executive summary:

Butyl phenyl ether was evaluated for skin irritation potential in an in vitro EpiDerm skin irritation assay (MatTek Corporation; Ashland, MA). The EpiDerm tissue consists of normal, human-derived epidermal keratinocytes (NHEK) that are cultured to form a multilayered, differentiated model of human epidermis. In this assay, Butyl phenyl ether was topically applied to the EpiDerm tissue for 60-minutes, followed by a 42-hour postexposure recovery. Following recovery, the cell viability was measured in treated and control tissues using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay and the data reported as a percentage of the mean of negative control. A test chemical was considered to possess skin irritation potential (UN GHS Cat 1/2) if the relative cell viability was less than or equal to 50%. In this study, Dulbecco Phosphate Buffered Saline (DPBS) and 5% SDS served as the negative and positive controls, respectively.

The mean relative cell viability of Butyl phenyl ether and positive control-treated tissues were 88.6% and 36.0% (i.e. ≤ 50%), respectively. Therefore, Butyl phenyl ether was interpreted as a potential non-irritant (UN GHS Cat NC) to skin in the EpiDerm irritation assay.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: OECD Guideline study performed in accordance with GLP requirements (but not a GLP study).

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 492 (Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage)

Version / remarks:

This study is not designed to fulfill any testing guidelines. The current protocol is a
streamlined version of OECD TG 492 test guideline.

Deviations:

no

GLP compliance:

no

Remarks:

THe study was conducted in accordance with the principles of GLP (reporting, data auditing, data retention, GLP qualification fo all equipment and study personel) but was not officially conducted as a GLP study.

Specific details on test material used for the study:

Test Material Name: Butyl phenyl ether
Chemical Name: Butoxybenzene
Lot/Reference/Batch Number: 06027KH
Purity/Characterization (Method of Analysis and Reference): The non-GLP certificate of analysis lists the purity as 99.5% by gas liquid chromatography with structure confirmation by infrared spectroscopy (Rajzer, 2007).
Stability: Butyl phenyl ether, lot 22466, was determined to be stable for 2 weeks at 54°C which is equivalent to 24 months under ambient storage conditions as tested under USEPA OPPTS Guideline 830.6317. (Ferruzzi, 2016).
The test material butyl phenyl ether, lot 06027KH was not tested for neat test material stability. However, neat test material stability was conducted for butyl phenyl ether, Lot 22466, under GLP conditions determining the neat test material to be stable for 24 months under ambient storage conditions.

Species:

human

Details on test animals or tissues and environmental conditions:

The EpiOcular three-dimensional model has been extensively characterized and currently has an OECD test guideline (OECD TG 492) for identifying chemicals not requiring classification and labeling for eye irritation or serious eye damage.

The EpiOcular model estimates the potential ocular irritation of a test substance by measuring cytotoxicity following topical exposure (Freeman et al., 2010) (MatTek Corporation, Ashland, MA). This assay assumes that in vitro cytotoxicity is directly proportional to in vivo damage that a test substance would inflict upon exposure to the eye (cornea) (Jackson et al., 2006). This assumption is based in part on the Maurer et al. (2002) proposed hypothesis, which suggests that the level of ocular irritation is related to the extent of initial injury, regardless of the processes leading to tissue damage.

Principle of the Test System:
The EpiOcular model (OCL-200) uses Normal Human Epidermal Keratinocytes (NHEK) from a single donor as the cell source. The cells are cultured on polycarbonate membranes of cell culture inserts (MILLICELLs, 10 mm diameter, 0.6 cm² surface), in serum-free medium to form a multi-layered (5-8 cell layers), highly differentiated, stratified, squamous epithelia that closely mimics human eye (corneal) epithelium at biochemical and physiological levels. The EpiOcular tissue is mitotically and metabolically active and releases many of the pro-inflammatory agents (cytokines) that are important in ocular irritation and inflammation.

Supplier and Location:
MatTek Corporation; Ashland Massachusetts

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

Preparation of the Test Material:
Test material was tested at a concentration of 100% (neat/as provided), following MatTek Corporation’s recommended procedure (Ocular Irritation Protocol: Neat Method-MTT).

Route of Administration:
The test material was administered by topical application to the ocular tissue.

Experiment Procedure:
Upon receipt, the EpiOcular tissue kits were stored at 2-8ºC and used within 24 to 48 hours of receipt from the supplier. On the day of testing, an aliquot of 0.9 mL of Dulbecco’s Modified Eagle’s medium (MatTek Corporation) was dispensed into the wells of 6-well plates. Each EpiOcular tissue was inspected for air bubbles between the agarose gel and Millicell insert prior to opening the sealed package. Tissue samples with air bubbles greater than 50% of the Millicell area were not used for testing.
The EpiOcular tissues were incubated at approximately 37ºC in a humidified atmosphere of approximately 5% CO2 for 60 ± 5 min. At the end of the first pre-incubation period, the inserts were transferred into wells containing fresh warm assay medium. The testing included treating the inserts with 50 μL (liquids) or 50 mg (solids) DPBS (negative control; 30±2 exposure time), 0.3% Triton X-100 (positive control; 30±2 exposure time) and the test material (three exposure times; 2, 15, or 30 min). Following the exposure periods, the EpiOcular tissues were carefully washed with Dulbecco phosphate buffered saline (DPBS; GIBCO, Grand Island, NY) (at least 5 times) to remove residual test substance. Following washes, the Millicell inserts were submerged in fresh assay media and incubated at 37ºC and 5% CO2 for approximately 12±2 minutes (to remove any test chemical absorbed into the tissue) at room temperature. Subsequently, the Millicell inserts were further incubated in fresh medium for 120±15 minutes at standard culture conditions (post-exposure incubation). After incubation, the tissue inserts were transferred to a well containing 300 μL MTT solution in a 24-well plate and tissues were incubated for 3 ± 0.1 hr at standard cell culture conditions. After incubation the tissues were washed with DPBS and the MTT dye (formazan crystals) is solubilized and extracted from the inserts by incubating each insert in 2 mL of extract reagent (MatTek Corporation) for at least 2 hours with gentle shaking or overnight at room temperature. The extract solution was mixed and two x 200 μL aliquots of the extract solution was transferred to a 96-well plate and the optical density of the extracted formazan was quantified at 570 nm (OD570) using a Microplate Reader.

Duration of treatment / exposure:

The testing included treating the inserts with 50 μL (liquids) or 50 mg (solids) DPBS (negative control; 30±2 exposure time), 0.3% Triton X-100 (positive control; 30±2 exposure time) and the test material (three exposure times; 2, 15, or 30 min).

Duration of post- treatment incubation (in vitro):

Following washes, the Millicell inserts were submerged in fresh assay media and incubated at 37ºC and 5% CO2 for approximately 12±2 minutes (to remove any test chemical absorbed into the tissue) at room temperature. Subsequently, the Millicell inserts were further incubated in fresh medium for 120±15 minutes at standard culture conditions (post-exposure incubation).

Irritation parameter:

other: ET-40

Remarks:

Value is in minutes

Value:

30

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

Criteria for Determination of a Valid Test:
The results for negative and positive controls met the assay acceptance criteria, suggesting appropriate conduct of the study.
1) The corrected mean OD570 value of the negative control tissues (exposed for 30 minutes) was 2.454 (i.e., ≥ 1.00; criteria set by the tissue manufacturer).
2) The ET40 value of the positive control (26.9 minutes) was within two standard deviations of the historical mean of manufacture data (12.2 – 37.5 minutes; Kubilus et al., 2005)

Calculation of ET-40 value:
The ET-40 value represents the test material exposure time that results in reduction in cell viability to 40% of negative control level. The ET-40 is determined by linear interpolation between time-points above and below 40% cytotoxicity. To determine ET-40, the dosing time is represented in log scale and % viability in linear scale and a supplier provided Microsoft Excel 5.0 macro is used. The test substance was considered a severe irritant (UN GHS Cat 1) or an irritant (UN GHS Cat 2) in the EpiOcular assay if the ET-40 was less than 3 or 30 minutes, respectively. The test substance was considered a non-irritant (UN GHS Cat NC) if the ET-40 was >30minutes.

Assessment of Direct Test Chemical Reduction of MTT:
One limitation of this assay method is a possible interference of the test material with the MTT assay. A colored test substance or one that directly reduces MTT (and thereby mimics dehydrogenase activity of the cellular mitochondria) may interfere with the MTT end-point. This issue arises for test materials that remain on the tissue after several postexposure washes. In the present study, Butyl phenyl ether was evaluated for potential interaction with the MTT dye.
Approximately 100 mg of Butyl phenyl ether was added to 1 mL of MTT solution in a tube and the mixture was incubated in the dark in an incubator with shaking at approximately 37°C for one hour. A negative control (100 μL of DPBS) was tested concurrently. Results from this experiment suggested that Butyl phenyl ether not interfere with the MTT dye, as the test material did not turn MTT solution to blue/purple crystals.

Interpretation of results:

Category 2 (irritating to eyes) based on GHS criteria

Conclusions:

The ET-40 values of Butyl phenyl ether and positive control were 30.0 minutes and 26.9 minutes respectively. As the ET-40 of Butyl phenyl ether was 30 minutes, Butyl phenyl ether was classified as a potential mild (UN GHS Cat 2) irritant to eyes.

Executive summary:

Butyl phenyl ether was evaluated for eye irritation potential in the in vitro EpiOcular eye irritation screening assay (MatTek Corporation; Ashland, MA). The EpiOcular tissue consists of normal, human-derived epidermal keratinocytes that are cultured to form a stratified, squamous epithelium similar to that found in the cornea. The test consisted of topical application of the test material to the EpiOcular tissue for 30 minutes followed by thorough washing with DPBS and incubating with cell culture medium for approximately 120 ± 5 minutes (post-exposure recovery). In this study, Butyl phenyl ether was tested at two additional exposure times (2 and 15 minutes) to better characterize its irritation potential. Following recovery, the cell viability in the EpiOcular tissue was measured in the treated and control tissues using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay and the data was reported as a percentage of the mean of negative control. An ET-40 value was calculated for Butyl phenyl ether, which is the time of exposure that resulted in reduction in cell viability to 40% of negative control level. The test substance was considered a severe irritant (UN GHS Cat 1) or an irritant (UN GHS Cat 2) in the EpiOcular assay if the ET-40 was less than 3 or 30 minutes, respectively. The test substance was considered a non-irritant (UN GHS Cat NC) if the ET-40 was >30minutes. In this study, Dulbecco Phosphate Buffered Saline (DPBS) and 0.3% Triton X-100 served as the negative and positive controls, respectively.

The percent viability for Butyl phenyl ether-treated EpiOcular tissue was < 50% at 30 minutes, therefore, interpreted as a potential mild irritant (UN GHS Category 2) in the EpiOcular assay.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Eye Irritation:

Butyl phenyl ether was evaluated for eye irritation potential in the in vitro EpiOcular eye irritation screening assay (MatTek Corporation; Ashland, MA). The EpiOcular tissue consists of normal, human-derived epidermal keratinocytes that are cultured to form a stratified, squamous epithelium similar to that found in the cornea. The test consisted of topical application of the test material to the EpiOcular tissue for 30 minutes followed by thorough washing with DPBS and incubating with cell culture medium for approximately 120 ± 5 minutes (post-exposure recovery). In this study, Butyl phenyl ether was tested at two additional exposure times (2 and 15 minutes) to better characterize its irritation potential. An ET-40 value was calculated for Butyl phenyl ether, which is the time of exposure that resulted in reduction in cell viability to 40% of negative control level. The test substance was considered a severe irritant (UN GHS Cat 1) or an irritant (UN GHS Cat 2) in the EpiOcular assay if the ET-40 was less than 3 or 30 minutes, respectively. The test substance was considered a non-irritant (UN GHS Cat NC) if the ET-40 was >30minutes. In this study, Dulbecco Phosphate Buffered Saline (DPBS) and 0.3% Triton X-100 served as the negative and positive controls, respectively. The percent viability for Butyl phenyl ether-treated EpiOcular tissue was < 50% at 30 minutes, therefore, interpreted as a mild irritant (UN GHS Category 2) in the EpiOcular assay.

Skin Irritation:

Butyl phenyl ether was evaluated for skin irritation potential in an in vitro EpiDerm skin irritation assay (MatTek Corporation; Ashland, MA). A test chemical was considered to possess skin irritation potential (UN GHS Cat 1/2) if the relative cell viability was less than or equal to 50%. In this study, Dulbecco Phosphate Buffered Saline (DPBS) and 5% SDS served as the negative and positive controls, respectively. The mean relative cell viability of Butyl phenyl ether and positive control-treated tissues were 88.6% and 36.0% (i.e. ≤ 50%), respectively. Therefore, Butyl phenyl ether was interpreted as a non-irritant (UN GHS Cat NC) to skin in the EpiDerm irritation assay.

Justification for classification or non-classification

Eye irritation: Category 2 (irritating to the Eye)

Skin: not classified.

The substance does not meet the classification criteria as described in regulation EC 1272/2008 or its accompanying guidance