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Toxicological information

Acute Toxicity: inhalation

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Administrative data

Endpoint:
acute toxicity: inhalation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Exposure duration deviating from current standards. 6 female rats were tested instead of 5 males and 5 female rats in OECD403, but this is consistent with current OECD guideline 436. Purity is unspecified for the batch tested, only a general purity is stated for the production at the time. Indirect measurement to assess airborne concentrations (nominal concentrations). The aerosol was generated from an aqueous solution instead of dust particles. However this, and the fact the particle generated were 1 um size is expected to be in favour of potential lung absorption.

Data source

Reference
Reference Type:
publication
Title:
The benzenediols: catechol, resorcinol and hydroquinone: a review of the industrial toxicology and current industrial exposure limits.
Author:
Flickinger C.W.
Year:
1976
Bibliographic source:
American Industrial Hygiene Association Journal, 37(10), 596-606.

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
other: Federal register (see below)
Deviations:
not specified
Principles of method if other than guideline:
Federal Register (1961) pp.7333-7341, Part 191- Hazardous Substances: Definitions and Procedural and Interpretative Regulations, Final Order
GLP compliance:
no
Test type:
other: inhalation study
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
aerosol dispenser: not specified
Remarks:
migrated information: aerosol
Details on test material:
Resorcinol, 1,3-benzenediol.
water-soluble, white crystalline compound. Typical purity of commercial resorcinol is reported to be > 99% based on process performance at the time of test.
Koppers Company Inc., Resorcinol, Flake Grade. Purity not stated.
Resorcinol-water solutions were prepared and atomized at 1µm size.

Test animals

Species:
rat
Strain:
Wistar
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Harlan-Wistar, no more data
- Age at study initiation: no data
- Weight at study initiation: 87 to 126 grams
No more data

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
not specified
Vehicle:
other:
Details on inhalation exposure:
- Aerosol generation system: 
Because resorcinol is hygroscopic, size reduction and dispersion in air of particle size < 10 µm were impractical to obtain concentrations of 2000 mg/m3 and higher. Therefore resorcinol-water solutions were prepared and atomised to particle of 1 µm size.
Samples were dissolved in distilled water and the resulting solutions were aerosolised using a D18 Dautrebande aerosol generator operated at 30 psi. At this operating pressure, the D18 generator delivers droplet diameters of 1 µ size and smaller. Airborne concentrations were determined by measurement of the volume loss of solution following aerosolisation. 
The weight of sample present in that volume was then calculated and related to the total volume of air used in generating the aerosol to obtain chamber concentrations. The nominal airborne concentrations of sample were 1500, 2000 and 2800 mg/m3.
Analytical verification of test atmosphere concentrations:
yes
Remarks:
airborne conc. were determined by measurement of the volume loss following aerosolisation. The weight of sample present in that volume was calculated and related to the total volume of air used in generating the aerosol to obtain chamber concentrations.
Duration of exposure:
1 - 8 h
Remarks on duration:
1 hour or 8 hours inhalation periods were tested.
Concentrations:
1 h: 2130 and 7800 mg/m3 (nominal)
8 hrs: 2000, 2480, and 2800 mg/m3 (nominal)
No. of animals per sex per dose:
6 females per dose
Control animals:
no
Details on study design:
Animals were held for 14 days following exposure and were then weighed and sacrificed for gross necropsy.
Rats were observed during a 14-day post-exposure period.

Results and discussion

Effect levelsopen allclose all
Sex:
female
Dose descriptor:
LC0
Effect level:
>= 2 800 mg/m³ air (nominal)
Based on:
test mat.
Exp. duration:
8 h
Remarks on result:
other: LC50 >= 2.8 mg/L
Sex:
female
Dose descriptor:
LC0
Effect level:
>= 7 800 mg/m³ air (nominal)
Based on:
test mat.
Exp. duration:
1 h
Remarks on result:
other: LC50 >= 7.8 mg/L
Mortality:
No deaths resulted when rats inhaled resorcinol-water aerosols at 2130 and 7800 mg/m3 for 1 hour.
No deaths were observed when rats inhalaed resorcinol-water aerosols at 2000, 2480, and 2800 mg/m3 for 8 hours.
Clinical signs:
other: There no clinical signs observed during the 14-day observation period.
Body weight:
All animals had normal 14-d weight gains
Gross pathology:
No lesion attributable to inhalation of aerosol was seen at gross necropsy. 

Any other information on results incl. tables

The solutions of resorcinol-water at 7800 mg/m3 (1-hr exposure) and 2480 mg/m3 (8 -hr exposure) turned milky and some precipitate was noted. It is likely that flow concentration was less than the concentration calculated for these 2 exposure conditions.

Applicant's summary and conclusion

Interpretation of results:
not classified
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
Resorcinol (1,3-benzenediol, CAS 108-46-3) did not induce mortality or clinical signs at up to 7800 mg/m3 for 1 hour, or up to 2800 mg/m3 for 8 hours.
Executive summary:

In a study (Flickinger, 1976), 6 female Wistar rats were exposed to aerolizated solutions of resorcinol at nominal doses of 2130, and 7800 mg/m3 for 1 hour, or to nominal doses of 2000, 2480, or 2800 mg/m3 for 8 hours.

The LC0 (1 hr) was > 7800 mg/m3 and the LC0 (8hrs) was > 2800 mg/m2 . At this dose, no mortality occured, and no clinical signs were observed.

Based on the experimental LC0, resorcinol, a substance structurally related to hydroquinone is not considered as harmful by the inhalation route.

Based on similarities of structure and metabolisation pathway, and consistent toxicity levels by the oral and dermal route, resorcinol is considered a relevant surrogate to estimate the acute inhalation toxicity potential of HQ.