tert-butyl methacrylate

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference

Reference Type:

other: Thesis

Title:

Unnamed

Year:

2002

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Butyl methacrylate

EC Number:

202-615-1

EC Name:

Butyl methacrylate

Cas Number:

97-88-1

Molecular formula:

C8H14O2

IUPAC Name:

butyl methacrylate

Test material form:

other: liquid

Specific details on test material used for the study:

- Supplier: Ineos Acrylics
- Name of test material (as cited in study report): n-butyl methacrylate
- Physical state: liquid
- Analytical purity: 99%
- Purity test date: no data
- Lot/batch No.: Acrylics 98/15

Radiolabelling:

no

Test animals

Species:

rat

Strain:

Wistar

Sex:

male

Administration / exposure

Type of coverage:

open

Vehicle:

unchanged (no vehicle)

Duration of exposure:

48 hours

Doses:

100 µL/cm²

Details on in vitro test system (if applicable):

The absorption of nBMA was evaluated through rat and human epidermis and through rat whole skinin an in vitro system.

SKIN PREPARATION
- Source of skin: epidermal membrane absorption studies: male rats of the Wistar-derived strain (supplied by Charles River UK Ltd, Margate, Kent, UK.); whole skin absorption studies: male Fisher F344 rats (supplied by Harlan Olac); human skin for epidermal membrane absorption studies: extraneous tissue was removed from human abdominal whole skin samples
- Ethical approval if human skin: obtained post mortem in accordance with local ethical guidelines
- Type of skin: human and rat skin
- Preparative technique:
Wistar rat skin: Fur from the dorsal and flank region was carefully shaved using animal clippers, ensuring that the skin was not damaged. The clipped area was excised and any subcutaneous fat removed. The skins were soaked for approximately 20 hours in 1.5M sodium bromide then rinsed in distilled water. The epidermis was carefully peeled from the dermis. Each epidermal membrane was given an identification number and stored frozen on aluminium foil until required for use.
Fisher rat skin: Fur from the dorsal and flank region was carefully shaved using animal clippers, ensuring that the skin was not damaged. The clipped area was excised and any subcutaneous fat removed. Each skin membrane was given an identification number and immediately assembled into diffusion cells and their integrity checked.
Human skin: The skin samples were immersed in water at 60°C for 40-45 seconds and the epidermis was carefully peeled away from the dermis. Each epidermal membrane was given an identifying number and stored frozen on aluminium foil until required for use.
- Thickness of skin (in mm): Discs of approximately 3.3 cm in diameter; thickness not specified
- Membrane integrity check: yes; The donor and receptor chambers of the cells were filled with physiological saline (approx 0.9% w/v sodium chloride in water) and placed in a water bath maintained at 32ºC ± 1ºC. Membrane integrity was determined by measuring their electrical resistance. Membranes that were found to have a measured resistance that was below 2.5 kΩ (rat) or 10 kΩ (human) were regarded as having a lower integrity than normal and were not used. Following the completion of the integrity assessment, the contents of the donor and receptor chambers were discarded
- Storage conditions: frozen

PRINCIPLES OF ASSAY
- Diffusion cell: glass diffusion cell
- Receptor fluid: 50% ethanol in water (rat and human epidermis experiments) or physiological saline (0.9% w/v sodium chloride in water) (whole rat skin experiment)
- solubility in receptor fluid: Those esters that were tested are sufficiently
soluble in the ethanol/water receptor fluid, however, only the smaller esters – MMA & nBMA – are anything more than slightly soluble in saline
- Static system: yes; dose rate 100 μl cm-2; occluded for the duration of the exposure period (up to 48 h)
- Flow-through system: no
- Occlusion: yes

Results and discussion

Signs and symptoms of toxicity:

not examined

Dermal irritation:

not examined

Absorption in different matrices:

Absorption of nBMA through rat epidermis:
The fastest rate of absorption (mean) of nBMA through rat epidermis was measured to be 1543 µg cm-2 hr-1, which occurred between 0 and 6 hrs following the application of the chemical. The rate of absorption diminished from this time onwards, as indicated by a flattening of the curve. The total amount absorbed was calculated as 11% by 6 hours and 18.3% after 24 hours, at which point no more samples were taken.

Absorption of nBMA through human epidermis:
The rate of absorption of n-butyl methacrylate was linear over the duration of the experiment and was calculated to be 76.7 µg cm-2 hr-1. Just over 2% of the applied dose was absorbed over the exposure period.

Absorption of nBMA through whole (viable) rat skin
Only methacrylic acid (MAA) appeared in the receptor chambers of skin that had had n-butyl methacrylate applied to the surface. This would imply that all of the nBMA that is absorbed through the skin is hydrolysed by carboxylesterases that are present in this tissue. The peak rate of appearance of MAA, which occurred between 2 and 10 hrs, was calculated to be 40.9 µg cm-2 hr-1. There is a lag-time present between 0 and 2 hrs. This experiment did not extend beyond ten hours, and the percentage dose removed from the donor reservoir was 0.4%.

Percutaneous absorption

Percutaneous absorption 1

Dose:

100 µL/cm²

Parameter:

percentage

Absorption:

18 %

Remarks on result:

other: 24 hours

Remarks:

Rat epidermis

Percutaneous absorption 2

Dose:

100 µL/cm²

Parameter:

percentage

Absorption:

2 %

Remarks on result:

other: 24 hours

Remarks:

Human epidermis

Percutaneous absorption 3

Dose:

100 µL/cm²

Parameter:

percentage

Absorption:

0.4 %

Remarks on result:

other: 10 hours

Remarks:

Whole (viable) rat skin

Conversion factor human vs. animal skin:

Human epidermis appears to be 20 times less permeable to nBMA than rat epidermis.

Any other information on results incl. tables

The results of the whole-skin penetration studies and the model predictions for 

other methacrylate esters are presented in the table.

Table: Summary of peak rates of absorption of MAA and alkyl-methacrylate esters through whole rat skin.

 Ester     Ester      MAA     Period    %               Peak       Peak       Peak    Applied
                                         Absorp. Dose/
                                 (hours) length of exposure
-----------------------------------------------------------
MAA                    4584    5 - 8       70%/24 h 
MMA        360         108     2.5 - 24    11.3%/24 h
EMA                    190**                              
i-BMA                   56**                              
n-BMA                   41     2 - 10      0.4%/10 h
HMA                     20**                              
2EHMA                    9**                              
OMA                     10     8 - 24      0.24%/24 h
LMA                     12     8 - 24      0.26%/24 h
-----------------------------------------------------------

Ester Peak = rate of appearance of the parent ester (µg/cm2/hr) 
MAA Peak = rate of appearance of the hydrolysis product, MAA (µg/cm2/hr)
Period Peak Absorp. = Time (hours) after application for peak absorption
% Applied Dose = total % absorbed
** Predicted rates of MAA from model estimates.

Applicant's summary and conclusion

Conclusions:

nBMA readily absorbs through rat and human epidermis and through whole rat skin. Human epidermis appears to be 20 times less permeable to 2-EHMA than rat epidermis.

Executive summary:

The absorption of nBMA was evaluated through rat and human epidermis and through whole (viable) rat skin in an in vitro system. Glass diffusion cells are employed to measure the amount of n-BMA that is received into a receptor chamber with respect to time, following the application of 100 µl/cm² of nBMA to the epidermal surface. The mean rate of absorption was 1540, 76.7 and 40.9 (appearance of MAA) µg cm-2 hr-1 and the total amount of chemical that was absorbed during the time of exposure was 18 (over 24 hours), 2 (over 24 hours) and 0.4% (over 10 hours), respectively. nBMA appears readily absorbed through rat and human epidermis, but human epideremis is 20 times less permeable to nBMA than rat epidermis.