Registration Dossier

Administrative data

Description of key information

No valid repeated dose toxicity studies on acetylsalicylic acid are available. A read-across approach is therefore proposed from studies on Methyl salicylate (MeS) which is readily metabolised to salicylic acid (See section.7.1.1), the main metabolite of ASA. On the other hand there is a long history of human use of ASA.
A set of studies was conducted on MeS by Webb & Hansen (1963), consisting of oral feeding studies of duration 17 weeks and 2 years in rats, studies in dogs by capsule administration of duration 59 days and 2 years, and a dermal study in rabbits. These studies did not examine all the parameters recommended in the current OECD guidelines 409 and 452, however they were conducted according to good scientific principles by US FDA. The chronic studies in rat and dog are therefore proposed as key studies for this endpoint, with the subchronic studies in rats and dogs as supporting study. A second set of subacute oral studies was conducted on MeS by Abbott & Harrisson (1978) to further investigate the effects on bone in rats and liver in dogs, identified in the studies by Webb & Hansen. These are considered to be acceptable as supporting studies.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
chronic toxicity: oral
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
no data are available
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This is an old study predating GLP however the protocol and results were reported in adequate detail and included hematological studies, gross pathology, and limited histopathological examinations of key organs and tissues.
Reason / purpose:
reference to same study
Qualifier:
no guideline available
Principles of method if other than guideline:
MeS was blended with diet and administered daily for a period of 2 years.
GLP compliance:
no
Limit test:
no
Species:
rat
Strain:
Osborne-Mendel
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: no data
- Age at study initiation: weanling
- Weight at study initiation: ~ 50 g
- Fasting period before study: no data
- Housing: no data
- Diet: ad libitum
- Water: no data
- Acclimation period: no data


ENVIRONMENTAL CONDITIONS
- Temperature (°C): no data
- Humidity (%): no data
- Air changes (per hr): no data
- Photoperiod: no data


IN-LIFE DATES: no data
Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS:


DIET PREPARATION
- Rate of preparation of diet (frequency): every other week
- Mixing appropriate amounts with (Type of food): no data
- Storage temperature of food: all diets were stored in sealed cans under refrigeration
- Other: 10% additional methyl salicylate was added at time of mixing to compensate for evaporation

VEHICLE: none
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
none
Duration of treatment / exposure:
2 years
Frequency of treatment:
daily
Remarks:
Doses / Concentrations:
0, 0.1, 0.5, 1 and 2% (0, 50, 250, 500, and 1000 mg/kg bw/day)
Basis:
nominal in diet
No. of animals per sex per dose:
25/sex/dose (except for 24 males, 26 females in 2% group)
Control animals:
yes
Details on study design:
- Dose selection rationale: the data reported in the subchronic study in rats by the same authors (methyl salicylate/ dietary administration for 17 weeks in rats).

Positive control:
no data are available
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: No


DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: The rats were weighed weekly.


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): No


FOOD EFFICIENCY: No



OPHTHALMOSCOPIC EXAMINATION: No


HAEMATOLOGY: Yes
- Time schedule for collection of blood: 3, 11, 17 and 22 months.
- Anaesthetic used for blood collection: No data
- Animals fasted: Yes
- How many animals: 10 rats/dose



CLINICAL CHEMISTRY: No


URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Other examinations:
none
Statistics:
not reported
Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
CLINICAL SIGNS AND MORTALITY
Animals of the 1.0% and 2.0% groups developed rough hair coats. In the high-dose group, half of the animals died by week 8 and all of the animals
died by week 49 of the study.
BODY WEIGHT AND WEIGHT GAIN:
Animals of the 1.0% and 2.0% groups had statistically significant growth inhibition.
HAEMATOLOGY
no hematological effects were observed.ORGAN WEIGHTSAverage organ weights were similar for all animals. however, relative organ to body weight
ratios for the testes of male animals and for the heart and kidneys of the female animals of the 1.0% groups were significantly increased.
GROSS PATHOLOGY
gross lesions of the pituitary gland were observed in 10 animals of the 0.5% group as compared to four animals in the control
group.In the 2% group, 29 of the 50 animals had pneumonia, which appeared to be more acute than regularly observed.
HISTOPATHOLOGY: NON-NEOPLASTIC
Microscopically, the only induced lesion was a pronounced change in the bones of the rats on the 2.0% diet.
Cancellous bone in the metaphysis was increased as compared to same-age controls; this was observed to a moderate degree in five and a marked
degree in four of the nine bones examined from animals of the 2.0% group. Bone lesions were slight in 2 of 11 and 1 of 11 bones examined from
animals of the 1.0% and 0.5% groups, respectively. The affected bones had fewer osteoclasts, and the number was inversely proportional to the
degree of change.
HISTOPATHOLOGY: NEOPLASTIC
The data are limited:Malignant pituitary tumors occurred in 1 male and 2 female rats on the 0.5% diet. Mammary tumors occurred in females rats on
all diets.
Dose descriptor:
NOAEL
Effect level:
50 mg/kg diet
Sex:
male/female
Basis for effect level:
other: Increased amount of cancellous bone from 250 mg/kg
Critical effects observed:
not specified

The results for a supplemental study:

One male test animal died on day 11, the two others died on day 19. The females died on days 31, 40 and 71. Rough hair coat and growth inhibition was observed for all test animals, with some animals having labored respiration.

Grossly, four of the six treated rats had slight to moderate lung damage. Focal gastric hemorrhages were present in the glandular portion of three of the test animals. Bone growth was affected.

Long bones of the limbs showed reduced length and diameter compared to controls. Density of the hypophysis of long bones was increased.

Conclusions:
Under the test conditions, growth retardation and bone lesions were reported in rats at levels of 1.0 and 2.0% MeS in the diet, with minimal effects at 0.5%. Based on this study and the subchronic oral study, the NOAEL /oral/rat is 0.1% (50 mg/kg body weight/day, equivalent to 59.2 mg/kg ASA ).
Executive summary:

Webb and Hansen (1963) administered methyl salicylate in the diet to groups of 24 -25 male and 25 -26 female Osborne-Mendel rats at dietary concentrations of 0, 0.1%, 0.5%, 1.0% or 2.0% in the diet providing doses of approximately 0, 50, 250, 500, and 1000 mg/kg body weight/day for two years. All rats in the 1000 mg/kg group died by the 49th week. Body weight of both sexes were significantly decreased in both the 500 and 1000 mg/kg group body weight/day groups.

An increased amount of cancellous bone was present in the metaphyses in rats treated at either 500 or 1000 mg/kg body weight/day, with a more marked effect at the highest dose level. A slight increase was reported in one rat at 250 mg/kg. The relative testes weights of males were significantly increased as were the relative weights of the heart and kidneys of females in the 500 mg/kg body weight/day group. Gross pituitary gland lesions were found in 10 rats at 250mg/kg bw/day compared to four animals in the control groups. while based on chronic and subchronic oral studies in rat by Webb and Hansen (1963), the NOAEL value is 50 mg/kg body weight/day (equivalent to 45.4 mg/kg bw/day as SA or 59.2 mg/kg ASA).

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
59 mg/kg bw/day
Study duration:
chronic
Species:
rat
Quality of whole database:
In this studies based on MeS it seems that in the rat the NOAEL from 1 month to 24 months is the same, while this is not the case in the
dog or the rabbit, with higher NOAEL at shorter times.

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available
Study duration:
subacute
Species:
rat
Quality of whole database:
No effect at vapour saturation 700 mg/m3 MeSal.

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Repeated dose toxicity: dermal - systemic effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: dermal
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: This study is limited in design and in reporting detail. Few animals were used, at very high dose levels.
Reason / purpose:
reference to same study
Qualifier:
no guideline available
Principles of method if other than guideline:
Rabbits were treated on their backs with four dose levels of methyl salicylate for approximately 6.5 hours daily for up to 96 days. Since the compound was absorbed, the backs of the rabbits were not wiped before they were replaced in their individual cages. Microscopic examinations were made of the major organs
GLP compliance:
no
Limit test:
no
Species:
rabbit
Strain:
not specified
Sex:
male/female
Type of coverage:
open
Vehicle:
unchanged (no vehicle)
Duration of treatment / exposure:
up to 96 days
Frequency of treatment:
daily on five days/week
Remarks:
Doses / Concentrations:
0.5, 1.0, 2.0 and 4.0 ml/kg/day (590, 1180, 2360, and 4720 mg/kg body weight/day)
Basis:
nominal per unit body weight
No. of animals per sex per dose:
3 per dose level (mixed sexes)
Control animals:
no
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Other examinations:
Local dermal effects
Dermal irritation:
effects observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Details on results:
CLINICAL SIGNS AND MORTALITY
The three rabbits on 4.0 ml/kg died after 6, 8, and 28 days and exhibited anorexia, weight loss, and depression.

BODY WEIGHT AND WEIGHT GAIN
Several of the survivors had subnormal weight gains

HISTOPATHOLOGY:
Microscopically: one high-dose animal had "several distinct lesions" including dilatation, desquamation, and formation of new atypical epithelium of the renal tubules; a moderate number of small foci of superficial necrosis and sloughing of the skin; foci of moderate necrosis and slight calcification of voluntary muscles; marked vacuolation of pancreatic acinar cells, slight myeloid hyperplasia and shift to the left of bone marrow, and slight hepatitis. These effects were not seen in the other examined high-dose animals, but an effect on the distal portion of the nephrons was indicated.The incidence of spontaneous nephritis and mild hepatitis in the nine surviving rabbits was increased over that in rabbits in other experiments.
OTHER FINDINGS: A slight sloughing of epidermal scales occurred in two of the three rabbits on 2.0 ml/kg/day. The remaining animals showed no skin abnormalities.
Dose descriptor:
NOAEL
Remarks:
Local effects
Effect level:
1 other: ml/kg bw/day
Sex:
male/female
Basis for effect level:
other: slight to very slight dermatitis (sloughing of epidermal scales) at 2.0 ml/kg bw/day
Dose descriptor:
LOAEL
Remarks:
Systemic effects
Effect level:
0.5 other: ml/kg bw/day
Sex:
male/female
Basis for effect level:
other: Increased spontaneous nephritis and mild hepatitis.
Critical effects observed:
not specified

One high dose decedent was not necropsied due to extreme autolysis. Of the two high dose animals examined, one showed local dermal effects (small foci of superficial necrosis and sloughing of the skin) as well as lesions in several organs (kidney, voluntary muscle, pancreas, bone marrow, liver). The only effect reported in the other high dose animal examined was a suggestion of an effect on the distal portion of nephrons. At 2.0 ml/kg (2360 mg/kg), slight sloughing of epidermal scales was observed in 2/3 rabbits. No dermal effects were noted in rabbits exposed to 0.5 or 1.0 ml/kg (590 and 1180 mg/kg body weight/day).The NOAEL for local effects was 1.0 ml/kg/day (1180 mg/kg bw/day).

No clear NOAEL was determined for systemic effects due to the reported increased incidence in spontaneous nephritis and mild hepatitis over that in rabbits in other experiments.

Conclusions:
Under the test conditions, no systemic or local NOAELs could be established.
Executive summary:

In a study by Webb and Hansen (1963), groups of three rabbits of both sexes were administered methyl salicylate of 99% purity to sites on the back clipped free of hair. Dermal exposures of 0.5, 1.0, 2.0 and 4.0 ml/kg/day (590, 1180, 2360, and 4720 mg/kg body weight/day) were administered 5 days/week for up to 96 days. The animals were restrained in holders for 6.5 h, but due to absorption the test substance was not wiped from the test sites after the exposure period. Following termination, the major organs from all rabbits except one severely autolysed animal were subjected to histological examination.

All the 3 high-dose animals had died by day 28 of exposure, following weight loss and depressed activity. In one of these animals, local effects on the skin (small foci of superficial necrosis and sloughing of the skin) and lesions in a number of organs (skin, kidney, voluntary muscle, pancreas, bone marrow, liver) were reported. The only effect reported in the other high dose animal examined was a suggestion of an effect on the distal portion of nephrons. At 2.0 ml/kg (2360 mg/kg), slight sloughing of epidermal scales was observed in 2/3 rabbits. No dermal effects were noted in rabbits exposed to 0.5 or 1.0 ml/kg (590 and 1180 mg/kg body weight/day). The NOAEL for local effects was 1.0 ml/kg/day (1180 mg/kg bw/day), however the lower pH of SA predicts a higher potential for irritation for the acid than for the ester. No clear NOAEL for local effects for SA could therefore be determined.

No clear NOAEL was determined for systemic effects due to the reported increased incidence in spontaneous nephritis and mild hepatitis over that in rabbits in other experiments.

This dermal study at very high doses was limited in design and in reporting detail and is not useful for the purposes of risk assessment for systemic toxicity.. It is not possible to determine whether the effects reported on kidney and other organs in one high dose animal represent systemic toxicity or a secondary effect due to skin and muscle damage.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LOAEL
590 mg/kg bw/day
Study duration:
subchronic
Species:
rabbit
Quality of whole database:
Sufficient for non classification

Repeated dose toxicity: dermal - local effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: dermal
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: This study is limited in design and in reporting detail. Few animals were used, at very high dose levels.
Reason / purpose:
reference to same study
Qualifier:
no guideline available
Principles of method if other than guideline:
Rabbits were treated on their backs with four dose levels of methyl salicylate for approximately 6.5 hours daily for up to 96 days. Since the compound was absorbed, the backs of the rabbits were not wiped before they were replaced in their individual cages. Microscopic examinations were made of the major organs
GLP compliance:
no
Limit test:
no
Species:
rabbit
Strain:
not specified
Sex:
male/female
Type of coverage:
open
Vehicle:
unchanged (no vehicle)
Duration of treatment / exposure:
up to 96 days
Frequency of treatment:
daily on five days/week
Remarks:
Doses / Concentrations:
0.5, 1.0, 2.0 and 4.0 ml/kg/day (590, 1180, 2360, and 4720 mg/kg body weight/day)
Basis:
nominal per unit body weight
No. of animals per sex per dose:
3 per dose level (mixed sexes)
Control animals:
no
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Other examinations:
Local dermal effects
Dermal irritation:
effects observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Details on results:
CLINICAL SIGNS AND MORTALITY
The three rabbits on 4.0 ml/kg died after 6, 8, and 28 days and exhibited anorexia, weight loss, and depression.

BODY WEIGHT AND WEIGHT GAIN
Several of the survivors had subnormal weight gains

HISTOPATHOLOGY:
Microscopically: one high-dose animal had "several distinct lesions" including dilatation, desquamation, and formation of new atypical epithelium of the renal tubules; a moderate number of small foci of superficial necrosis and sloughing of the skin; foci of moderate necrosis and slight calcification of voluntary muscles; marked vacuolation of pancreatic acinar cells, slight myeloid hyperplasia and shift to the left of bone marrow, and slight hepatitis. These effects were not seen in the other examined high-dose animals, but an effect on the distal portion of the nephrons was indicated.The incidence of spontaneous nephritis and mild hepatitis in the nine surviving rabbits was increased over that in rabbits in other experiments.
OTHER FINDINGS: A slight sloughing of epidermal scales occurred in two of the three rabbits on 2.0 ml/kg/day. The remaining animals showed no skin abnormalities.
Dose descriptor:
NOAEL
Remarks:
Local effects
Effect level:
1 other: ml/kg bw/day
Sex:
male/female
Basis for effect level:
other: slight to very slight dermatitis (sloughing of epidermal scales) at 2.0 ml/kg bw/day
Dose descriptor:
LOAEL
Remarks:
Systemic effects
Effect level:
0.5 other: ml/kg bw/day
Sex:
male/female
Basis for effect level:
other: Increased spontaneous nephritis and mild hepatitis.
Critical effects observed:
not specified

One high dose decedent was not necropsied due to extreme autolysis. Of the two high dose animals examined, one showed local dermal effects (small foci of superficial necrosis and sloughing of the skin) as well as lesions in several organs (kidney, voluntary muscle, pancreas, bone marrow, liver). The only effect reported in the other high dose animal examined was a suggestion of an effect on the distal portion of nephrons. At 2.0 ml/kg (2360 mg/kg), slight sloughing of epidermal scales was observed in 2/3 rabbits. No dermal effects were noted in rabbits exposed to 0.5 or 1.0 ml/kg (590 and 1180 mg/kg body weight/day).The NOAEL for local effects was 1.0 ml/kg/day (1180 mg/kg bw/day).

No clear NOAEL was determined for systemic effects due to the reported increased incidence in spontaneous nephritis and mild hepatitis over that in rabbits in other experiments.

Conclusions:
Under the test conditions, no systemic or local NOAELs could be established.
Executive summary:

In a study by Webb and Hansen (1963), groups of three rabbits of both sexes were administered methyl salicylate of 99% purity to sites on the back clipped free of hair. Dermal exposures of 0.5, 1.0, 2.0 and 4.0 ml/kg/day (590, 1180, 2360, and 4720 mg/kg body weight/day) were administered 5 days/week for up to 96 days. The animals were restrained in holders for 6.5 h, but due to absorption the test substance was not wiped from the test sites after the exposure period. Following termination, the major organs from all rabbits except one severely autolysed animal were subjected to histological examination.

All the 3 high-dose animals had died by day 28 of exposure, following weight loss and depressed activity. In one of these animals, local effects on the skin (small foci of superficial necrosis and sloughing of the skin) and lesions in a number of organs (skin, kidney, voluntary muscle, pancreas, bone marrow, liver) were reported. The only effect reported in the other high dose animal examined was a suggestion of an effect on the distal portion of nephrons. At 2.0 ml/kg (2360 mg/kg), slight sloughing of epidermal scales was observed in 2/3 rabbits. No dermal effects were noted in rabbits exposed to 0.5 or 1.0 ml/kg (590 and 1180 mg/kg body weight/day). The NOAEL for local effects was 1.0 ml/kg/day (1180 mg/kg bw/day), however the lower pH of SA predicts a higher potential for irritation for the acid than for the ester. No clear NOAEL for local effects for SA could therefore be determined.

No clear NOAEL was determined for systemic effects due to the reported increased incidence in spontaneous nephritis and mild hepatitis over that in rabbits in other experiments.

This dermal study at very high doses was limited in design and in reporting detail and is not useful for the purposes of risk assessment for systemic toxicity.. It is not possible to determine whether the effects reported on kidney and other organs in one high dose animal represent systemic toxicity or a secondary effect due to skin and muscle damage.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
1 180
Study duration:
subchronic
Species:
rabbit

Additional information

No repeated dose toxicity studies have been carried out on ASA itself. DNELs for systemic effects have been derived based on read-across from other salicylates (see Introduction). They are also to compare with ASA use as drug.

Cutaneous route

Since ASA is poorly absorbed by the skin (<2%), it is not really relevant to derive a DNEL for ASA for long term exposure by cutaneous route even though it is not classified as hazardous by cutaneous exposure.

A route to route extrapolation has been carried out (oral-to-dermal) based on an oral long term study performed on MeS (Webb, 1965).

Inhalation

No repeated dose inhalation toxicity data are available for SA. . One subacute inhalation toxicity study on MeS at a single limit dose level (saturated vapour) and chronic oral studies in rats and dogs are available for risk assessment. Nevertheless due to high granulometry ( 96% > 11 microns) and density, inhalation exposure is not relevant and the main part could be swallowed.

Assessment based on chronic dietary rat study

Based on an oral long term study performed on MeS (Webb, 1965). MeS was administered to rats at dietary concentrations of 0, 0.1%, 0.5%, 1.0% or 2.0% (equivalent to 0, 50, 250, 500, and 1000 mg/kg bw/day) for two years. Body weight of both sexes were significantly decreased in both the 1.0% and 2.0% groups and an increased amount of cancellous bone was present in the metaphyses in rats treated at 1.0% or 2.0%, with minimal increase for one rat at 0.5%.

The NOAEL was 0.1% (50 mg/kg bw/day, equivalent to 59,2 mg/kg bw/day as SA). The LOAEL was 0.5% (250 mg/kg bw/day) for body weight gain reduction and bone lesions in rats.

 


Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Rat isthe usual species and it is a 2 years study and same MeS NOAEL at 28 days. MeS 50 mg/kg equivalent to 59.2 mg/kg ASA

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
Study not possible with ASA crystalline powde of high MMAD (>150um), rat need MMAD of 2 um forinhalative fraction. Supporting study with MeS saturating vapour was negative.

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
Not an irritant and not a sensitiser

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:
No adverse effetc in acute test and not an irritant. Me Sal is a related substance

Justification for selection of repeated dose toxicity dermal - local effects endpoint:
not an irritant. Read across with Me Sal which have imortant dermal penetration

Repeated dose toxicity: via oral route - systemic effects (target organ) other: bone

Justification for classification or non-classification

No repeated dose toxicity studies have been carried out on ASA itself. DNELs for systemic effects have been derived based on read-across from other salicylates (see Introduction). They are also to compare with ASA use as drug.

Assessment based on chronic dietary rat study

A route to route extrapolation has been carried out (oral-to-inhalation) based on an oral long term study performed on MeS (Webb, 1965). MeS was administered to rats at dietary concentrations of 0, 0.1%, 0.5%, 1.0% or 2.0% (equivalent to 0, 50, 250, 500, and 1000 mg/kg bw/day) for two years. Body weight of both sexes were significantly decreased in both the 1.0% and 2.0% groups and an increased amount of cancellous bone was present in the metaphyses in rats treated at 1.0% or 2.0%, with minimal increase for one rat at 0.5%.

The NOAEL was 0.1% (50 mg/kg bw/day, equivalent to 59,2 mg/kg bw/day as SA). The LOAEL was 0.5% (250 mg/kg bw/day) for body weight gain reduction and bone lesions in rats.

This is also used to derive Dermal NOAEL by route to route, an alternative would have been the rabbit subchronic NOAEL of 590 mg/kg (Webb, 1963).

The inhalation route is not relevant, due to the MMAD of ASA crystalline power (>100 microns) and the low % (<4%) of particles <10 microns.

With the above mentionned data ASA is not classified for repeat toxicity.