Registration Dossier

Administrative data

Description of key information

Repeated dose toxicity of HEMA has been investigated in an OECD 422 combined repeated dose and reproductive toxicity study. A chronic study does not have to be performed, because, like MMA, the substances are rapidly metabolised, and by analogy to MMA ultimately metabolised to carbon dioxide and water. Therefore, as demonstrated in the case of MMA in carcinogenicity studies of up to 2 years duration, there is no concern for lesions due to accumulative toxicity. MMA data with different species and different application routes are used by read-across. For EG, the glycolic metabolite of HEMA, subchronic and chronic studies in rodents show toxicity with the kidneys as target organ.

Read across evaluation according to ECHA’s ReadAcrossAssessment Framework (RAAF)

The metabolism from HEMA to its primary metabolites is well understood. The same is true for the further metabolism pathways of MAA and the alcohol metabolite EG, respectively (see chapter 5.2, ATSDR 1997/ 2008/ 2010, NTP 2004a, 2004b). The endpoint specific “scientific assessment” of the read across is thus “acceptable with a high level of confidence”.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well conducted study, carried out by Nippon Bioresearch Inc.Hashima Laboratory (Japan).
Qualifier:
according to
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Deviations:
yes
Remarks:
, An old version of OECD 422 (not containing functional observation battery test) had been  conducted.
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Crj: CD(SD)
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Japan
- Age at study initiation: 10 weeks
- Weight at study initiation: male 341~380 g; the female was 232~256 g.
- Housing: suspended, stainless steel cage; 5/cage until breeding, then divided into separate rearing cages.
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 5 day quarantine; 7 day acclimation

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 ~ 24 ℃
- Humidity (%): 40 to 70%
- Photoperiod (hrs dark / hrs light): 12 hour light / 12 hour dark

Route of administration:
oral: gavage
Vehicle:
water
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS: dissolved in water


VEHICLE
- Justification for use and choice of vehicle (if other than water): water
- Concentration in vehicle: 5 mL/kg
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
Males, 49 days; Females, from 14 days before mating to day 3 of lactation
Frequency of treatment:
Once daily
Remarks:
Doses / Concentrations:
0 (vehicle), 30, 100, 300, 1000 mg/kg/day
Basis:

No. of animals per sex per dose:
12
Control animals:
yes
Details on study design:
Post-exposure period: Male, 50 days; Females, day 4 of lactation
- Dose selection rationale: based on range-finding
- Rationale for animal assignment (if not random): random
Positive control:
not applicable
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily
- Cage side observations checked : general condition and mortality; estrus and abnormal labor conditions in females

BODY WEIGHT: Yes
- Time schedule for examinations: twice per week in males; before mating, twice a week during the mating period, 0, 7 ,14 and 21 days duirng pregnancy, during the feeding period was measured 0 and 4 days in females

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): one week prior to mating, then twice a week; additionally, in females, days 2,9,16 and 21 of pregnancy, four days over the feeding period.
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: day after treatment
- Anaesthetic used for blood collection: Yes; sodium pentobarbital
- Animals fasted: No data
- How many animals: No data
- Parameters checked in table [No.1] were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: day after treatment
- Animals fasted: No data
- How many animals: No data
- Parameters checked in table [No.2] were examined.

URINALYSIS: No


NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
Terminal kill: Males, day 50; Females, day 4 of lactation
GROSS PATHOLOGY: Yes; Thymus, liver, kidney, testis and epididymis weight in males and ovary in females was measured after removal, adrenal gland, brain, heart and spleen and 10% neutral buffered formalin solution (However, testicular and epididymal fluid Buan) was fixed. Post-mortem examination of feamles who did not give birth to Day 25 of pregnancy. Number of corpora lutea and the number of implantation scars in females.

HISTOPATHOLOGY: Yes; Paraffin-embedded specimens were prepared. Control group and 1000 mg / kg group of heart, liver, spleen, thymus, kidney, testis and epididymis in males ovary in females, adrenal and brain for the Preparation HE staining of tissue was examined histologically. In males, 1000 mg / kg in the kidney was considered to indicate a difference in the number of abnormal animals in the test group compared with the control group; 30, 100 and 300 mg / kg group were similarly examined. In females, 1000 mg / kg differences in the brain was considered to indicate an abnormal number of animals in the test group than the control group and changes in adrenal cases and 30, 100, 300 mg / kg group were similarly examined.
Other examinations:
Fetal examinations
(1) number of preterm birth and sex, number of stillborn children, the presence of abnormalities observed and the number of newborn.
(2) general condition and mortality
(3) measurement of body weight
(4) autopsy
Statistics:
Newborn screening as a unit has an average of one litter.
Weight (the parent animals, babies), food consumption, number of estrus, days mating, pregnancy [Day delivery (feeding 0) - date confirmed mating, the number of implantation scars, the number of birth control mobilize (number of babies stillborn baby + ), the number of newborn, number of children born dead, birth rate [(number of birth control mobilize / number of implantation scars) × 100], rate of production of child [(number of infant feeding 0 days / number of implantation scars) × 100], corpus number, implantation rates [(number of implantation scars / number of corpora lutea) × 100], fertility [(number of infant feeding 0 day / mobilize all of birth control) × 100], feeding baby number four day, feeding 4 day survival rate [(number of infant feeding 4 days / 0 Number of infant feeding day) × 100], unusual occurrence rate [(number of children with abnormal/ number of newborns) × 100], sex ratio (male / female), organ weights ( including the relative weight), results of blood tests, blood biochemistry test results for the mean and standard deviation were calculated for each group.
Significant difference test, Bartlett's test and the homoscedasticity of Law, analysis of variance, Dunnett method. Kruskal-Wallis test.
Copulation rate [(number of established animal mating / number of live animals) × 100], fertility [(number of female fertility / Establishment of animal mating) × 100], the birth rate [(number of female newborns / number of female fertility) × 100] is, χ ^ 2 using the test.
Cochran • Armitage was carried out using a test of dose-response trend test.
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):
effects observed, treatment-related
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
effects observed, treatment-related
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:
no effects observed
Details on results:
Detail:[Males]
1) General condition: With the survival animals, no death and no moribund  were found for 30, 100 and 300 mg/kg/day groups. At 1000 mg/kg/day, one  death on day 20 of dosing was seen and abnormality wasn't seen except for  salivation until the previous day.  With the dead animals, no abnormality  was found for 30, 100 and 300 mg/kg/day groups.  At 1000 mg/kg/day,  salivation was seen in about 1 to 30-minutes after dosing from day 3. 2) Body weight: No significant difference from control group was seen in  30, 100, and 300 mg/kg/day groups. At 1000 mg/kg/day, the significant low  value was recorded during day 18 to day 25 of dosing andduring day 32 to  day 50 of dosing.
3) Food consumption: At 30 and 300 mg/kg/day, no significant difference  from control was seen. At 100 mg/kg/day, the significant high values were  seen on day 31. but no dose-related changes were obserbed.At 1000  mg/kg/day, the statistically significant low values were recorded on day  13, 31 and during day 38 to day 45. 
4) Hematological examination: No significant difference from control  group was seen for all groups up to 1000 mg/kg/day dose.
5) Blood chemical examination: At 30 and 300 mg/kg/day,the significant  high value in BUN were seen. As the difference was very small, this was  not considered as the adverse effect of HEMA dosing.  At 100 mg/kg/day, a  higher value of BUN but not statistically signifficant difference from  control was recorded. At 1000 mg/kg/day, the significant high values were  recorded in BUN, K, Cl,I-phosphorous and Triglyceride. 
6) Autopsy: No abnormalitywas found for 30 and 100 mg/kg groups. In the  300 mg/kg group, the albedo spot in the kidney of the unilateral in the 1  animal and, the atrophy of the testiculus of the bilaterality and  softening were observed in the 1 animal. In the 1000 mg/kg group, the  dark-red of the thymus gland in the 1 animal and the hypertrophy of the  kidney of bilaterality in the 1 animal were observed. 
7) Weight oforgans: At 30 mg/kg/day, no significant difference from  control group in absolute and relative weight was seen for all organs. At  100 and 300 mg/kg/day, the significant high value was recorded in the  absolute weight of kidneys. At 1000 mg/kg/day, the statistically  significant high values were recorded in the relative weight of liver and  kidneys.
8) Histopathological examination: At 1000 mg/kg/day in the survival  animals, the dilatation of renal tubule in 3 animals in the kidney and  the dilatation of collecting tubules in 2 animals were obserbed. But, all  these changes were just slight. And the dilatation of renal tubule has a  significant difference but no dose-related changes.  As for the  dilatation of collecting tubules, it has no significant difference but  increase tendency. In the other group, there were hemorrhage of thymus  gland, microgranuloma of the heart, microgranuloma of the liver and  hepatocyte vacuolar degeneration of the centrilobular, renal basophilic  tubules, eosinophilic corpuscle in proximal tubule, cyst, diffusive  mineral deposition and neutrophilic infiltration. But it was judged with  the incidental change, because they were whether it equivalently seems  even in the control group or small number animals. And no abnormality was  observed in spleen, adrenal, testiculus and brain in the control and 1000  mg/kg group. In animal of death of the 1000 mg/kg group, there were  hemorrhage of the thymus gland, edema of the lung, autolysis of adrenal  and lung and thymus gland with the deadanimal of 1000 mg/kg group. As for  those degrees, all were just slight. In the adrenal with the abnormality  in the autopsy, no change which suggested hypertrophy was seen.   
[Females]
1) General condition: With the existence animales, no death and no  moribund were seen for 30, 100 and 300 mg/kg/day groups. At 1000  mg/kg/day, three death on day 6 of dosing, one death on day 12 of dosing  and one death on day 17 of dosing were seen. Salivation, decrease in  locomotor activity, adoption of a prone position, acrimation, soiled fur,  hypothermia, bradypnea were seen at 1000 mg/kg. With the death animals,  no abnormality was found for 30, 100 and300 mg/kg/day groups.  At 1000  mg/kg/day, salivation was seen in about 1 to 30-minutes after dosing from  day 3.
2) Body weight: Before mating period, no significant difference from control  group was seen at 30, 100 and 300 mg/kg/day. At 1000 mg/kg/day, the  significant lower values were recorded on day 4 and 5 of dosing. During  gestation period, no significant difference from control groups was seen  in 30, 300 and 1000 mg/kg/day groups. At 100 mg/kg/day, the significant  high values were recorded on day 21 of gestation,  but no dose-related  changes were observed. During lactation period, no significant difference  from control groups was seen in 300 and 1000 mg/kg/day groups. At 30 and  100 mg/kg/day, the significant high values were recorded on day 4 of  lactation, but no dose-related changes were obserbed.
3) Food consumption:  Before mating period, no significant difference from control group was  seen at 30, 100 and 300 mg/kg/day. At 1000 mg/kg/day, the significant low  value from control group was recorded on day 3, 6 and 13 of dosing. During  gestation period, no significant difference from control groups was seen  in 30 and 300 mg/kg/day groups. At 100 and 1000 mg/kg/day, the  significant high value from control group was recorded on day 16 of  gestation, but no dose-related changes were observed. During lactation  period, no significant difference from control groups was seen.
4) Weight of organs: At 30 mg/kg/day, no significant difference from  control group in absolute and relative weight was seen for all organs. At  100 mg/kg/day,the significant high value was recorded in the absolute  weight of kidneys. At 1000 mg/kg/day, the significant high values were  recorded in the relative and absolute weight of kidneys. 
5) Histopathological examination: Though at 1000 mg/kg/day survival  groups, neutrophilic infiltration (unilateral ) to medulla and papilla  mammae part in the kidney were observed in the 1 animal, the degree was  slight. Though extensive softening of the medulla oblongata in the brain  was observed in the 1 example at 1000 mg/kg group, the degree was slight.   In dead 6 animals of the 1000 mg/kg group, there were the edema in 1  animal in the lung, the atrophy in 1 animal in the thymus gland, the  atrophy in 5 animals and the atrophy of a Malpighian body in 1 animals in  the spleen, the hyperplasia of zona fasciculata in 3 animals and the  autolysis in 1 animal in the the adrenal and the erosion in 1 animal in  the small intestinal mucosa. The degrees of the atrophy in the thymus  gland and the atrophy of a Malpighian body were moderate, but the others  were slight.  All the changes are noted related agonism. No changes which  suggested, though the hypertrophy of the adrenal in 2 animals, dark-red  of the glandular stomach mucosa in 2 animals and dark-red of the  intestinum tenue were observed as abnormal in the autopsy of the 1000  mg/kg group.
Dose descriptor:
NOAEL
Effect level:
100 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male
Basis for effect level:
clinical biochemistry
organ weights and organ / body weight ratios
Dose descriptor:
NOAEL
Effect level:
300 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
female
Basis for effect level:
organ weights and organ / body weight ratios
histopathology: non-neoplastic
Critical effects observed:
not specified
Conclusions:
An OECD 422 study was conducted with rats by gavage at doses of 0, 30, 100, 300 and 1000 mg/kg. The NOELs for repeat dose toxicity are considered to be less than 30 mg/kg for males, and 30 mg/kg for females.
Executive summary:

2-Hydroxyethyl methacrylate was studied for oral toxicity in rats in an OECD combined repeat dose and reproductive/developmental toxicity screening test at doses of 0, 30, 100, 300 and 1000 mg/kg/day. One male and 6 females of the 1000 mg/kg group (12 animals of each sex) died during the treatment period. In the males, BUN was elevated or tended to be high at 30 mg/kg or more, and the relative kidney weights were increased at 100 mg/kg or more. Salivation, suppression of body weight gain, decrease in food consumption, iucreased K, C1 and inorganic phosphorous, decreased triglyceride, increased relative liver weights, dilatation of renal tubules and collection tubules in the kidney were seen at 1000 mg/kg. In the females, the relative kidney weights were elevated or tended to be high at 100 mg/kg or more. Salivation, decrease in locomotor activity, adoption of a prone position, lacrimation, soiled fur, hypothermia, bradypnea, suppression in body weight gain, decrease in food consumption, increases of absolute and relative kidney weights, neutrophil cellular infiltration in the papilla and medulla and massive malacia in the medulla oblongata were seen at 1000 mg/kg. The NOELs for repeat dose toxicity are considered to be less than 30 mg/kg for males, and 30 mg/kg for females.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
100 mg/kg bw/day
Study duration:
subacute
Species:
rat

Additional information

Repeated dose toxicity: oral

There are reliable data available to assess the toxic potential of HEMA after repeated oral exposure. HEMA has been evaluated for repeat-dose toxicity in Sprague-Dawley rats in the OECD 422 combined repeat-dose developmental/reproductive toxicity screening test. This study was conducted by the Japan Ministry of Health and Welfare and assigned a K-2, reliable with restriction reliability rating.

For the primary metabolites data are available for subchronic to chronic exposures. The eight studies used are reliable with or without restrictions (K-1 or K-2; partially presented under the chapter “carcinogenicity”). The metabolism from HEMA to the primary metabolites is well understood and the same is true for the further metabolism pathways of MAA and EG, respectively (see category document, chapters 5.2 and 5.7). The endpoint specific “scientific assessment” of the read across is thus acceptable with at least medium confidence.

HEMA

In the study for HEMA, male rats (12/group) were given daily gavage doses of 0 (vehicle), 30, 100, 300 or 1000 mg/kg for 50 days including pre-mating, mating and post-mating intervals. Females (12/group) were administered the same doses for two weeks prior to mating, during mating and gestation up until day 4 of lactation. (approximately 54 days depending upon time to conception). Animals were observed for clinical symptoms of intoxication daily and food consumption and body weight were monitored throughout the study. Blood samples were taken for hematological and clinical chemistry analysis at study termination. Thymus, liver, kidney, testes, epididymes, and ovaries were weighed. In addition to these tissues, adrenal gland, brain, heart and spleen were fixed in 10% neutral buffered formalin solution for subsequent staining and histopathological evaluation.

Six animals of the 1000 mg/kg dose groups died (one male, five females). Clinical symptoms of intoxication observed at 1000 mg/kg [the highest dose tested] included: salivation, suppression of body weight gain, decrease in food consumption, increased kidney weights and renal histopathological changes as well as decrease in locomotor activity, adoption of a prone position and lacrimation (females only). Liver weight was increased in males only, but there was no histopathological correlate. Further, females exposed to 1000 mg/kg HEMA had an elevated incidence of malacia of the medulla oblongata, but this effect was not observed at lower doses and was not observed in males at any dose level.

Male rats in 300 mg/kg and 1000 mg/kg dose groups had elevated kidney weights and also elevated levels of BUN. Histopathological changes in the kidney of male rats were confined to minimal (+/-) grade severity observations in 1000 mg/kg group animals that included: renal tubule dilatation (3 rats); collecting duct dilatation (2 rats); unilateral cyst (1 rat); diffuse mineralization (1 rat) and neutrophilic cellular infiltration (1 rat). In addition, basophilic tubules and eosinophilic bodies in proximal tubules were described in similar numbers of animals for both control and 1000 mg/kg groups. The single histological observation in 300 mg/kg group males was focal renal tubule degeneration of minimal (+/-) grade in one male rat.

Female rats had elevated kidney weight at 1000 mg/kg and at 100 mg/kg, but not at 300 mg/kg. Histopathological changes in kidney tissue described in one female rat as grade 1 (+) unilateral neutrophilic cellular infiltration into the medulla and papilla were observed in female rats only at the 1000 mg/kg dose level. Clinical chemistry measurements were not reported for female rats.

Overall, these results for repeat-dose toxicity testing of HEMA indicate that the kidney is a target organ for toxicity in both male and female rats. Male rats had elevated kidney weights and BUN levels at 300 and 1000 mg/kg dose levels. However, histopathology was described as minimal and occurred only in a few animals. The 100 mg/kg dose was the No Observed Adverse Effect Level (NOAEL) for these effects on kidney in males. Female animals had elevated kidney weights and histopathological changes in one animal and only at the 1000 mg/kg dose level; 300 mg/kg was the NOAEL for lethality and effects on kidney in females.

The short half-life of HEMA (as desribed in the metabolism chapter) implies that, under normal physiological conditions, the systemic exposure to HEMA as parent ester is irrelevant for the hazard assessment. This is especially true when the low level of electrophilic reactivity as potential mode of action of the parent esters is considered. The combination of the short half-life and the weak electrophilic reactivity of the parent esters means that toxicity profile upon repeated dosing is determined by the profiles of the primary metabolites (EG and MAA).

Primary Metabolites

Primary Metabolite MAA (donor substance MMA)

Due to the corrosivity of MAA, a repeated dose study by the oral route has not been performed. In a guideline inhalation study, ten male and ten female Sprague Dawley rats per test group were whole body exposed to MAA vapour on 6 hours per working day for 90 days (65 exposures). The target concentrations were 20, 40, 100 and 350 ppm (corresponding to 72, 143, 358 and 1252 mg/m³). At the high dose of 350 ppm, equivalent to a body burden of 308 mg/kg/d in males and 377 mg/kg/d in females[1], the 90-day inhalation exposure of rats to MAA induced signs of general toxicity as indicated by decreased body weight, body weight gain, food consumption and transiently food efficiency in the high concentration male animals. At 350 ppm, the local irritating effect was marginal, indicated by the hypertrophy/hyperplasia of the respiratory epithelium in the nasal cavity of two female animals. Under the current test conditions, the no-observed adverse effect level (NOAEL) in this study is 100 ppm (equivalent to a body burden of 88 mg/kg/d in males and 96 mg/kg/d in females) for the male and female rats.

Primary metabolite EG

There are several rodent studies available with orally applied Ethylene glycol (EG). From those, subchronic and chronic feeding studies mainly performed by NTP were selected for the IUCLID dataset of HEMA for the reason of sufficient reliability and high relevance of the continuous uptake mode of a metabolite. In general, “the kidney is clearly identified as the most sensitive target organ in rats and mice after intermediate-duration oral exposure ” of high doses > 1000 mg/kg/d”. Typical renal effects included oxalate crystal deposition and renal tubular dilation, vacuolation, and degeneration. Oxalate, a metabolite of glycolic acid, forms a precipitate in the presence of calcium, and the deposition of these crystals in the renal tubules are hallmarks of ethylene glycol toxicity. Glycolic acid accumulation and metabolic acidosis do not contribute to renal toxicity, which is solely caused by oxalate crystal accumulation. Males were more sensitive than females, and rats were more sensitive than mice” (ATSDR 2010).

After subchronic feeding, the NOAEL in male mice was found to be 3230 mg/kg/d based on liver and kidney effects, while no adverse effects were found in female mice up to 16,000 mg/kg/d (NTP 1993). After subchronic feeding, the NOAEL in male rats was found to be 600-1000 mg/kg/d, while the NOAEL in female rats was found in female rats to be 1000-1500 mg/kg/d; both based on kidney effects (Melnick et al. 1984). After chronic feeding, the NOAEL in male mice was found to be 1500 mg/kg/d based on liver effects, while the NOAEL in female mice was found to be 3,000 mg/kg/d based on blood effects (all NTP 1993).

Repeated dose toxicity: inhalation

There are no relevant inhalation studies available on HEMA. A limited three-week inhalation study in rats at saturated VP (approx. 0.5 mg/L) showed no toxic effects.

See also discussion regarding “Route” below

Repeated dose toxicity: dermal

There are no relevant dermal studies available on HEMA.

Repeated dose toxicity: other routes

No relevant studies available.

Human information

There are no relevant data available

Summary and discussion of repeated dose toxicity

Subacute (~50 d) repeated dose studies are available for both, HEMA and HPMA. For the primary metabolites methacrylic acid/MMA, ethylene glycol and propylene glycol subchronic or chronic repeated dose data are available. For comparison reasons, results from rat studies are shown below.


 

Table11: Repeated dose toxicity - NOAEC/NOAEL summary

Route & effects type

HEMA

MW 130.14

HPMA

MW 144.17

MAA      MW 86.09

MMA

MW 100.12

EG

MW 62.07

PG

MW 76.09

Inhalation

Local effects

---

---

100 ppm

358 mg/m³

25 ppm

208 mg/m³
*
   **

---

---

Inhalation

Systemic effects

---

---

100 ppm

358 mg/m³

500 ppm

1040 mg/m³

---

---

 

 

 

 

 

 

 

Oral

Systemic effects

100 mg/kg/d

(gavage)

300 mg/kg/d

(gavage)

---

164 mg/kg/d

(drinking water)

600 mg/kg/d

(feeding)

≥2500 mg/kg/d

(feeding)

0.77 mmol/ kg/d

2.08 mmol/ kg/d

 

1.64 mmol/ kg/d

9.67 mmol/ kg/d

32.9 mmol/ kg/d

*

The departure point for the risk assessment is the SCOEL IOLV of 50 ppm, taking into account observations in humans

 

**

No time-dependency of the lesion was found in several studies between 6 hours and 2 years

 

 

HEMA and HPMA have been evaluated for repeat-dose toxicity by the oral route in the OECD 422 protocol. In this protocol, both males and females were given daily oral gavage doses of HEMA and HPMA up to the limit dose of 1000 mg/kg/day for approximately 50 consecutive days. Toxicity was achieved in these studies as demonstrated by reduced food consumption and body weight gain at 1000 mg/kg/d. In addition, for HEMA only (not found for HPMA), kidney toxicity particularly in male rats as indicated by elevated BUN levels in serum, elevated kidney weights and minimal histopathological changes were described in 1000 mg/kg group animals. For males dosed with HEMA, the NOAEL was 100 mg/kg/d while the NOAEL for females administered HEMA was 300 mg/kg/d. No target organ was identified for HPMA even at doses which depressed body weight gain and food consumption.

These results indicate a mild effect of HEMA on the kidney which is considered a target organ for HEMA at very high repeat oral doses that depressed body weight gain and food consumption. These mild changes in kidney after approximately 50 days exposure indicate a small likelihood that effects of greater severity at the same effect doses or effects at lower doses would be observed in 90 day studies. The male rat (and Sprague-Dawley rat in particular) is prone to the spontaneous development of kidney toxicity beginning as early as 90 days of age (Goldstein 1988; Masoro, 1989). Thus, the mild effects described upon administration of limit doses of HEMA to male Sprague-Dawley rats may represent the interaction of the material with initial stages of development of spontaneous kidney toxicity in these animals.

 

Route

As outlined earlier, the saturated vapour density is approx. 80 ppm (427 mg/m³) for HEMA equivalent to a maximum body burden of approx. 100 mg/kg/d for a standard inhalation study in rat. In practice, the saturated vapour density is a theoretical value that cannot be achieved in full because under the conditions of an inhalation study the equilibrium is not reached fast enough. In consequence, that means that a study could only be performed below the expected NOAEL. The existing inhalation screening study confirms that.  

 

Discussion

As described in the toxicokinetics chapter, the short half-life of the parent ester combined with their weak electrophilic reactivity mean that toxicity profile upon repeated dosing is determined by the primary metabolites (EG and MAA). In comparison of the two hydroxyalkyl methacrylates HEMA has a lower NOAEL based on repeated dosing as compared to HPMA.

In the case of HEMA and EG after repeated exposure both substances demonstrate general signs of toxicity and body weight loss at high doses with specific target organ toxicity in the kidney (Furuhashi et al. 1997; ATSDR 2010). It is well understood that the kidney effects of EG are related to its metabolites, glycolic and oxalic acids. The relevant NOAEL of HEMA for the derivation of the DNEL is 100 mg/kg bw/d. So, the two predominant modes of action which have to be considered are general toxicity of the methacrylates as expressed by body weight effects and kidney effects as a specific MoA of the glycol metabolite.

Body weight: The common primary metabolite MAA is metabolised via the TCA cycle predominantly being eliminated as CO2 and water. After repeated exposure (350 ppm/-477 mg/kg/d, 90 days) there are no apparent adverse systemic findings other than reduced food consumption and transiently food efficiency in the high concentration male animals resulting in decreased terminal body weight and body weight gain in these animals. The dose range is consistent between the MAA study and HEMA. Bearing in mind that the study duration is different, and consistent findings have been observed e.g. in the 2-year carcinogenicity study with MMA (NTP, 1986) there is apparently not much progression of this lesion with an extended duration of the study,

Kidney effects: As mentioned earlier, the kidney effects of EG are related to its metabolites, glycolic and oxalic acids. Also, the markedly lower NOAELs in studies with bolus dosing (e.g. gavage studies) as compared to continuous dosing (e.g. feed studies) highlight the effect of transiently high serum concentrations. A typical exposure situation at the workplace would be more similar to the continuous dosing scheme so that kidney effects seen in gavage studies are probably less relevant in practice. In addition, the EG studies indicate, that a further progression with extended duration of the study to even lower NOAELs is not expected

As outlined earlier, the inhalation route is not an appropriate route of exposure for the hydroxyalkyl methacrylates HEMA and HPMA, because it is very unlikely that toxicologically relevant concentrations could be reached using the inhalation route.

Taken together, results of repeat-dose studies in HEMA and results from studies on MAA/MMA as representative of the chemical class of short-chain alkyl esters of methacrylic acid and on EG, the alcohol metabolite, indicate that additional studies of longer duration (90 days) are not critical for the assessment of HEMA and may therefore be waived. 

 

[1]Calculated using R8 guidance defaults for respiration / body weight, assuming 100 % absorption

Justification for classification or non-classification

HEMA is not classified for repeated dose toxicity.No severe or irreversible effects were identified. CLP criteria are not met NOAEL >= 100 mg/kg.