Methylamine

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

Key: Oral: Munley S.M., 2007: Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test in Rats, gavage (0, 250, 500, 1000 mg methylamine hydrochloride/kg bw/day).

Supporting: Oral: Sarkar, S., and Sastry, M. Chronic toxicity of methylamine on oral administration and feed contamination in rats, 1988; rats, up to 90 days, route of exposure is unspecified 5 mg/kg bw/day (oral)

Link to relevant study records

Reference

Reference 1

Endpoint:

screening for reproductive / developmental toxicity

Remarks:

based on test type

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
In this justification, the read-across (bridging) concept is applied, based on the chemical structure of the potential analogues, their toxicokinetic behaviour and other available (eco-)toxicological data. Please refer also to the detailed read-across justification attached in section 13.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The underlying hypothesis for the read-across is that the target and the source substance have similar toxicological properties due to their structural similarity, resemblance to their chemical reactivity, and biotransformation products in toxicological compartments. In other words, there is a clear chemical analogy (“biotransformation to common compound", scenario 1 of the Read Across Assessment Framework (ECHA 2017)).
The solvation of both methylamine and methylammonium chloride in water results in solutions of the methylammonium cation (“common breakdown product", scenario 1 of the Read Across Assessment Framework (ECHA 2017)). The toxicity of the respective counterion (“non-common compound” – Cl-) is in this case negligible; as Cl does not drive toxicity effects in mammalian species because it is one of the main electrolytes and is required in large amounts in living organisms. So any toxicity of the amounts originated from the methylammonium chloride at maximum dose levels that would be used in toxicity studies is not expected.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

source substance:
methylamine hydrochloride (methylammonium chloride)
structural formula: CH5N.ClH
SMILES: [Cl-].C[NH3+]
CAS 593-51-1
purity: not specified

target substance:
methylamine
structural formula: CH5N
SMILES: CN
CAS 74-89-5
purity: ≥ 80 – 100 %

No additional information is available on purity of the source and the target substances. Both substances are normally of high purity, containing only minor amounts of impurities that do not influence the read-across validity.

3. ANALOGUE APPROACH JUSTIFICATION
Read across from the structural analogue to the target substance is based on the high structural similarity of the analogue with the substance of interest and the similarity of their toxicological characteristics.
The target substance MMA (CAS 74-59-5), as well as the source substance MMA-HCl (CAS 593-51-1) belong to the category of the “Aliphatic amines” according to the profiler “US EPA New Chemical Categories” in the OECD QSAR Toolbox v4.1.
The basicity of amines increases with the length of the aliphatic rest due to electron releasing properties of alkyl groups: the higher the pKa value, the weaker the acid, so the stronger the base. Monomethylamine (the primary amine with a central nitrogen atom and 1 methyl group and 2 hydrogen-atoms) is the least basic of the aliphatic (primary) amines. Monomethylammonium chloride (composed also of one methyl group attached to the nitrogen atom, which is regarded as the common structure / functional group) is no longer basic, but neutralised (please also refer to the following paragraphs). Therefore, it has to be kept in mind that MMA-HCL is an example of a worst case read-across according to RAAF, as MMA tested as salt may achieve very high doses because it is not corrosive.
Furthermore, the chemicals are characterized by a common Mode Of Action (MOA) in detail as “narcotic amines” according to Acute aquatic toxicity MOA by OASIS in the OECD QSAR Toolbox v4.1.
Methylamine and methylammonium chloride - as primary aliphatic amines - undergo similar reactions and resemble each other in their physico-chemical properties. The fundamental properties of different amine classes (primary, secondary and tertiary) – basicity and nucleophilicity – are very much the same (Morrison and Boyd, 1987).
Typical reactions of amines are salt formation, alkylation, and conversion into amides and Hofmann elimination from quaternary ammonium salts (Morrison and Boyd, 1987).
As already mentioned above, they are linked by the common functionality of one central nitrogen atom which bears an unshared pair of electrons and tends to share these electrons determining a similar chemical behaviour. This unshared electron pair can accept a proton - forming a substituted ammonium ion. The tendency to share this electron pair underlies the entire chemical behaviour of amines as a group and this was considered as main / basic parameter, which is suitable for read-across in an analogue approach within an/a analogue/category approach.
The dissociation constant of MMA allows the conclusion that virtually all molecules of methylamine - when dissolved in an excess of water - are present as the methylammonium cation. Moreover, the available data of MMA with hydrochloric acid shows clearly that there will be no relevant amounts of the amine available once in contact with the bodies’ fluids. Only the ionic form is the relevant species present. This applies to all relevant exposure routes, i.e. inhalation, dermal, and as in this case oral. So, in consequence, the solvation of both methylamine and methylammonium chloride in water would result in solutions of the methylammonium cation (“common breakdown product"). Therefore, one must only regard the physico-chemical properties of the respective counterion. Methylamine solutions are accompanied by the hydroxyl anion OH-, resulting in alkaline solutions, whereas the chloride anion of the methylammonium chloride solutions is not expected to trigger significant changes in the pH and exhibit any significant toxicological effects. Both anions are naturally and ubiquitous occurring ions and are also to a certain extent required for the maintenance of various body functions.
The corrosive effects of MMA can certainly be explained by the high concentration of hydroxyl anions in MMA solution, which are likely to occur even when the gas gets in contact with skin moisture or other body fluids. MMA (gas) is legally classified as Skin Irrit. 2 and Eye Dam. 1, MMA (aqueous solution) is legally classified as Skin Corr. 1B; MMA-HCl has no legal classification for Skin or Eye irritation/corrosion. There is no data available on skin irritation of MMA. Experimental data showed MMA-HCl to be only transiently mildly irritating to the eyes of rabbits (no C & L is triggered). MMA-HCl is expected to be minor irritating when compared to MMA, because of the pH neutralisation caused by HCl. Consequently, the enhanced absorption of MMA compared to MMA-HCl due to damage of the skin barrier should be regarded when the substances are applied in corrosive concentrations or without pH neutralization.
Besides the influence of HCl on the pH value of an aqueous solution, it does not bear a relevant intrinsic property, allowing one in general to focus on the methylammonium cation. Generally, it should be denoted that very commonly in literature there is no differentiation made between MMA and MMA-HCl.
Primary amines are considered to be hydrolytically stable and both substances have been shown to be readily biodegradable. The log Koc values are both negative and relatively close and support the read-across approach. Furthermore, the results show that the substances do not have a significant potential for persistence (not P not vP) or bioaccumulation in organisms (not B not vB). Moreover, they are similar in their toxicity endpoints (despite the above mentioned missing corrosivity in the case of MMA-HCl).
The similar findings (refer also to the data matrix outlined below) for both substances support the conclusion that the identical molecule will be formed from both substances when applied systemically, and this molecule, i.e. the methylammonium cation, is responsible for their behaviour and the observed effects. In consequence, the methylammonium cation is indeed what is left to be considered in both cases and similar effects can reasonably be expected when using data from MMA-HCl for the lacking endpoints, compared to the data obtained with MMA.
Hence, MMA-HCl may perfectly serve as a worst case read-across substance for MMA. So, the available data on MMA-HCl can be used to cover all systemic endpoints currently lacking from MMA, making further testing obsolete.

4. DATA MATRIX
There is data available on the environmental fate and behaviour, ecotoxicological and toxicological properties of MMA. Data on MMA-HCl covers data on Biodegradation, Toxicokinetics, oral Repeated dose toxicity, Genetic toxicity in vivo and Toxicity to reproduction/Developmental toxicity. Hence, the identification and discussion of common properties of MMA and MMA-HCl will be mainly based on this and physicochemical data.
The different physical state of the two substances (MMA is - as a pure substance - gaseous at room temperature, MMA-HCl is a solid primary ammonium salt) triggers some differences in the physico-chemical properties like Melting point, Boiling point, Decomposition temperature and Vapour pressure. Nevertheless, regarding the application of both substances, i.e. their distributed form, the gaseous character of MMA becomes less relevant as the substances are usually not applied in their pure forms but rather as aqueous solutions.
The available data for the following physico-chemical properties, which are among others relevant for absorption, are very similar. Both substances are small molecules with a low molecular weight of 31.042 (MMA) resp. 67.52 (MMA-HCl), they are both very soluble in water (completely miscible in water (MMA) and at least 1080 mg/L at 20 °C (MMA-HCl)), have a negative logPow (-0.713 (aqueous solution, 25 °C, pH 11.1 - 11.4; MMA) and -3.82 (MMA-HCl)), and both are readily biodegradable. Although being expected to be hydrolytically stable in the natural environment, they both have a very low potential for bioaccumulation in aquatic and terrestrial organisms. Most importantly, MMA has a pKa of 10.79 at 20 °C (≙ pKb = 3.21), which indicates that methylamine exists almost entirely in the cationic form as methylammonium cation at pH values of 5 to 9.
MMA (not neutralised) has a toxicity potential towards fish and aquatic invertebrates, but does not have to be classified as hazardous. MMA (neutralised) and MMA-HCl have a lower toxicity potential to aquatic organisms and do not have to be considered to be acutely harmful to fish or aquatic invertebrates, nor to microorganisms (no C & L).MMA and MMA-HCL have been shown to be toxic to some extent to aquatic algae and cyanobacteria (shown in Desmodesmus subspicatus, Pseudokirchnerella subcapitata, Scenedesmus obliquus and Microcystis aeruginosa). Their aquatic toxicity potential under real environmental conditions has to be judged carefully, since, methylamine and methylamine hydrochloride are readily biodegradable in nature. As such, both can be considered as non-toxic to aquatic organisms and thus do not have to be classified as hazardous as per the CLP classification criteria.
Regarding their toxicity towards mammals, both substances exert their acute toxicity oral toxicity in the same range (Acute tox 4 - H302 for MMA aqueous solution and for MMA HCl) and are also classified as Acute tox 3 - H331 (MMA - gaseous form, MMA - aqueous solution) and Acute tox 4 - H332 (MMA HCl) via the inhalation route of exposure: MMA (gaseous form and aqueous solution) are also classified as STOT SE 3 (C ≥ 5 %). Moreover, MMA is corrosive / irritative to the skin and the eyes (MMA (gas) = Skin Irrit. 2 and Eye Dam 1; MMA (aqueous solution) = Skin Irrit 1B); in the case of MMA –HCl no classification is warranted.
Regarding their repeated dose toxicity, the No-observed-adverse-effect-levels of both substances to differ to a certain extent (NOAEL ≥ 10 versus NOAEL = 500 mg/kg bw/day). Concerning genetic toxicity in vitro, both substances have been shown to be not mutagenic in Gene mutation in bacteria (Ames) tests. Furthermore, MMA and MMA HCl have been tested for their potential to cause gene mutation in mammalian cells. For MMA an older result gives a positive result when tested only without metabolic activation. However, the very recent new investigation conducted with MMA-HCl showed it not to be mutagenic Chinese hamster ovary cells. For MMA HCL there is also data for toxicity to reproduction and developmental toxicity available (NOEL (reproduction/systemic tox) = 500 mg/kg bw/day and NOAEL (maternal/developmental tox.) = 155 mg/kg bw/day).
No data on long-term toxicity to fish; on long-term toxicity to aquatic invertebrates or carcinogenicity were available.

Reason / purpose for cross-reference:

read-across source

Clinical signs:

no effects observed

Description (incidence and severity):

No specific test substance-related deaths in males or females at any level tested. No test substance-related clinical observations at any level tested

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Test substance-related, adverse effects at 1000 mg/kg/day: significant reductions in body weight in P1 animals. No test substance-related effects on body weight parameters at 500 mg/kg/day or lower.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Test substance-related, adverse effects at 1000 mg/kg/day: significant reductions in body weight in P1 animals. No test substance-related effects on body weight parameters at 500 mg/kg/day or lower.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Test substance-related microscopic findings were observed in the trachea (squamous metaplasia) and stomach (mucoid metaplasia) of males and females given 1000 mg/kg/day of the test substance Methylammonium chloride.

Other effects:

effects observed, treatment-related

Description (incidence and severity):

Test substance intake: Methylammonium chloride was administered by gavage in water

Reproductive function: oestrous cycle:

effects observed, treatment-related

Description (incidence and severity):

Test substance-related & statistically significant reduction in mean corpora lutea count at 1000 mg/kg/day, results in a reduction in the mean number of implantation sites per litter and a significant reduction in the mean litter size at this dose level

Reproductive performance:

no effects observed

Key result

Dose descriptor:

NOEL

Effect level:

500 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

reproductive performance

Clinical signs:

no effects observed

Mortality / viability:

no mortality observed

Body weight and weight changes:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings:

not examined

There was a test substance-related and statistically significant reduction in mean corpora lutea count at 1000 mg/kg/day that resulted in a reduction in the mean number of implantation sites per litter and a subsequent significant reduction in the mean litter size at this dose level. There were no other test substance-related effects on reproductive outcome at this level nor were there any effects on reproductive outcome at 500 mg/kg/day or lower.
There was a significant reduction in mean litter size at 1000 mg/kg/day that was associated with a test substance-related reduction in the mean numbers of corpora lutea observed at this level. Otherwise, there were no additional test substance-related effects in offspring at 1000 mg/kg/day and no evidence of any test substance-related effects on offspring at 500 mg/kg/day or lower.

There were no test substance-related clinical observations in the pups at any dose level tested.

There were no test substance-related effects on mean pup weight either at birth or on day 4 of lactation at any dose level tested.

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

500 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: test substance-related reduction in litter size observed at 1000 mg/kg bw/day.

Key result

Reproductive effects observed:

yes

Lowest effective dose / conc.:

1 000 mg/kg bw/day (nominal)

Treatment related:

yes

Relation to other toxic effects:

reproductive effects as a secondary non-specific consequence of other toxic effects

Dose response relationship:

yes

Relevant for humans:

not specified

Conclusions:

Test substance-related effects were observed at 1000 mg/kg/day and were limited to reductions in parental body weights and food consumption parameters and a significant reduction in the mean corpora lutea and associated reduction in mean implantation sites and mean litter size. There was no evidence of systemic or reproductive toxicity at 500 mg/kg/day or lower.

Executive summary:

Test substance-related effects were observed at 1000 mg/kg/day and were limited to reductions in parental body weights and food consumption parameters and a significant reduction in the mean corpora lutea and associated reduction in mean implantation sites and mean litter size. There was no evidence of systemic or reproductive toxicity at 500 mg/kg/day or lower. Under the conditions of the study, there were no test substance-related effects on any neurobehavioral parameter evaluated in either males or females at any dose level tested. Daily gavage administration of up to 1000 mg/kg/day of the test substance Methylammonium chloride to male and female rats resulted in no adverse changes in clinical pathology parameters.

Liver: Since there was no gross or microscopic finding that correlated with the increased liver weights, and there was no increase in serum liver enzymes (see Clinical Chemistry), the weight effect was considered pharmacological and not adverse. Exposure to xenobiotics commonly induces hepatic metabolic enzymes in laboratory animals. While microscopic hypertrophy of hepatocytes may occur in hepatic enzyme induction, small increases in liver weight parameters are often not associated with a morphological change.

The increased kidney weight parameters in both sexes at 1000 mg/kg/day did not correlate with any gross or microscopic renal pathology. As in liver hepatocytes, xenobiotics may induce P450 microsomal enzymes in the renal proximal tubular epithelium. Increased kidney weights often precede morphological changes (i.e., hypertrophy) in non-adverse enzyme induction.

The metaplasia consisted of the partial replacement of the normal ciliated pseudostratified columnar epithelium on the ventral aspect of the tracheal mucosa with round and slightly flattened epithelial cells resembling mucous membrane. The change was not associated with inflammation of either the trachea or the lung. The minimal to mild squamous metaplasia was probably the result of transient topical exposure of the tracheal mucosa to the test substance Methylammonium chloride following gavage administration. It was interpreted to be a non-adverse adaptive response, most likely reversible, that was due to imperfect dosing or transient esophageal reflux.

The metaplasia consisted of a partial replacement of the normal parietal cells in the gastric glands with mucous epithelial cells. The change was evident in the fundic region of the glandular mucosa adjacent to the esophageal inlet. The change was not associated with any inflammation and was considered to be non-adverse. The minimal mucoid metaplasia was probably the result of the daily gavage administration of a slightly irritating solution to the glandular mucosa adjacent to the esophageal inlet. The degree of focal metaplasia appeared to be biologically insignificant. As with the focal tracheal metaplasia, the focal gastric metaplasia was interpreted to be a non-adverse, most likely reversible, adaptive response.

---

Daily gavage administration of 0, 250, 500, and 1000 mg/kg/day of the test substance Methylammonium chloride, to male and female rats for 98 to 119 consecutive days, resulted in increased liver and kidney weights, squamous metaplasia of the tracheal mucosa, and mucoid metaplasia of the glandular gastric mucosa. The increased liver weights in males (≥ 250 mg/kg/day) and females (≥ 500 mg/kg/day) and kidney weights in both sexes (1000 mg/kg/day) were consistent with pharmacological enzyme induction and were considered to be non-adverse. Minimal to mild squamous metaplasia of the tracheal mucosa and minimal focal mucoid metaplasia of the gastric glandular mucosa of several high-dose rats of both sexes were interpreted to be the result of topical exposure of the test substance Methylammonium chloride. The metaplastic changes in both tissues were interpreted to be adaptive and probably reversible. Therefore, both the tracheal and gastric metaplasia were considered to be non-adverse. There were no test substance-related effects on cause of death, gross pathology, or reproductive failure in adult rats. Gross examination of nursing pups that died before day 4 of lactation did not reveal any test substance-related findings. Under the conditions of this study, the no-observed-effect level (NOEL) for pathology for male and female rats was the highest dose tested, 1000 mg/kg/day Methylammonium chloride.

Under the conditions of this study, the no-observed-effect level (NOEL) for systemic and reproductive toxicity was 500 mg/kg/day methylammonium chloride based on reductions in parental body weights and food consumption and effects on reproductive outcome (reduced corpora lutea and subsequent reductions in implantations and litter size).

The target substance methylamine and the source substance methylammonium chloride used in this study belong to the group of primary aliphatic amines. The solvation of both, methylamine and methylammonium chloride in water results in solutions of the methylammonium cation (common "breakdown product"). Both respective counterions are naturally and ubiquitous occurring ions and are also to a certain extent required for the maintenance of various body functions. Besides the influence on the pH value of an aqueous solution (OH-), they do not bear a relevant intrinsic property, allowing one in general to focus on the methylammonium cation. The methylammonium cation is believed to act and to be metabolised by the same mechanisms by microorganisms and by other classes of living organisms.

Therefore both substances are expected to follow the same toxicokinetic pattern.

Reference 2

Endpoint:

one-generation reproductive toxicity

Remarks:

based on test type

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

not reported, published 1990

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well documented publication which meets basic scientific principles. Only brief description of methods.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline required

Principles of method if other than guideline:

no data available because of publication

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

6 female rats of 12-13 weeks age with regular oestrous cycle

Route of administration:

oral: unspecified

Details on mating procedure:

mated with nontreated male rats of proven fertility

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

not reported

Frequency of treatment:

daily

Details on study schedule:

no data

Dose / conc.:

5 mg/kg bw/day

No. of animals per sex per dose:

6

Control animals:

yes, concurrent no treatment

Details on study design:

- Six females of 12-13 weeks with a regular oestrus cycle were administered at 5 mg/kg methylamine for an unknown period of time
- Females were mated with untreated, proven fertile males
- Observations on the oestrous cycle and reproductive performance were made and the indices of fertility, gestation, live birth, and lactation were calculated

Oestrous cyclicity (parental animals):

no effect on oestrous cycle, redroductive indices and the average weight of pubs at birth and weaning.

Litter observations:

no effect on average weight of pubs at birth and weaning.
significantly decreased average litter size of the treated group

Statistics:

- Dunnett's test and Student's t-test were used for statistical evaluation

Clinical signs:

not specified

Body weight and weight changes:

no effects observed

Description (incidence and severity):

see 7.5.1. key study

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

see 7.5.1. key study

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

not examined

Other effects:

not specified

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

- Methylamine did not affect oestrous cycle, reproductive indices of fertility, gestation, live birth, lactation, and average weight of pups at birth and weaning
- Litter size was significantly (p<0.05 t-test) decreased compared to controls (8.83 (controls) and 6.33 (TS treated)).

Key result

Dose descriptor:

LOAEL

Effect level:

5 mg/kg bw/day

Based on:

test mat.

Sex:

female

Basis for effect level:

reproductive performance

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality / viability:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Histopathological findings:

not examined

Other effects:

not specified

Live birth, lactation, weaning and the average weight of pups were not affected, i.e. were similar to those of control animals. Significantly decreased litter size was noted in the treatment group.

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

5 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Live birth, lactation, weaning and the average weight of pups were not affected, i.e. were similar to those of control animals. Significantly decreased litter size was noted in the treatment group.

Key result

Reproductive effects observed:

yes

Lowest effective dose / conc.:

5 mg/kg bw/day

Treatment related:

not specified

Relation to other toxic effects:

not specified

Conclusions:

No treatment related effects. Litter size is decreased in the treated group.

Executive summary:

Sarkar and Sastry exposed 6 female pregnant rats of 12 -13 weeks age with regular oestrous cycle to 5 mg/kg bw/day of methylamine orally during pregnancy. No treatment related effects in the reproductive parameters tested were found in dams. The estrous cycle, reproductive indices of fertility, gestation, live birth, lactation, weaning and the average weight of pups were not affected, i.e. were similar to those of control animals. Significantly decreased litter size was noted in the treatment group.

Effect on fertility: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

500 mg/kg bw/day

Study duration:

subacute

Species:

rat

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

Sarkar and Sastry exposed 6 female rats of 12 -13 weeks age with regular oestrous cycle pregnant rats to 5 mg/kg bw/day of methylamine orally during pregnancy. No treatment related effects in the reproductive parameters tested were found in dams. The estrous cycle, reproductive indices of fertility, gestation, live birth, lactation, weaning and the average weight of pups were not affected, i.e. were similar to those of control animals. Significantly decreased litter size was noted in the treatment group.

In the OECD 422 study performed in 2005 till 2007 in rats, the influence of Methylammonium chloride after oral repeated dosage was examined, also including the reproductive and developmental effects. A daily gavage administration of 0, 250, 500, and 1000 mg/kg/day of the test substance Methylammonium chloride, to male and female rats for 98 to 119 consecutive days, resulted in increased liver and kidney weights, squamous metaplasia of the tracheal mucosa, and mucoid metaplasia of the glandular gastric mucosa. The increased liver weights in males (≥ 250 mg/kg/day) and females (≥ 500 mg/kg/day) and kidney weights in both sexes (1000 mg/kg/day) were consistent with pharmacological enzyme induction and were considered to be non-adverse. Minimal to mild squamous metaplasia of the tracheal mucosa and minimal focal mucoid metaplasia of the gastric glandular mucosa of several high-dose rats of both sexes were interpreted to be the result of topical exposure of the test substance. The metaplastic changes in both tissues were interpreted to be adaptive and probably reversible. Therefore, both the tracheal and gastric metaplasia were considered to be non-adverse. There were no test substance-related effects on cause of death, gross pathology, or reproductive failure in adult rats. Gross examination of nursing pups that died before day 4 of lactation did not reveal any test substance-related findings. Under the conditions of this study, the no-observed-effect level (NOEL) for pathology for male and female rats was the highest dose tested, 1000 mg/kg/day for Methylammonium chloride.

Under the conditions of this study, the no-observed-effect level (NOEL) for systemic and reproductive toxicity was 500 mg/kg/day Methylammonium chloride based on reductions in parental body weights and food consumption and effects on reproductive outcome (reduced corpora lutea and subsequent reductions in implantations and litter size).

Effects on developmental toxicity

Description of key information

Guest, I. and Varma, D. Developmental toxicity of methylamines in mice. 1991; mouse, 0.25, 1.0, 2.5 and 5.0 mmol/kg/bw Methylammonium chloride, during gestation, intraperitoneal; similar to the OECD guideline 414.

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The route of exposure (i.p.) is not standard. Beside that an acceptable, well-documented publication which meets basic scientific principles, test substance used is methylamine hydrochloride

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Principles of method if other than guideline:

Exploration if chronic administration of methylamines can cause reproductive toxicity using pregnant CD-1mice and mouse embryos in culture as experimental models.

GLP compliance:

not specified

Limit test:

yes

Species:

mouse

Strain:

CD-1

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, St. Constant, Quebec
- Weight at study initiation: 20-25 g
- Housing: Plexiglas cages with heat-treated wood chip bedding
- Diet (e.g. ad libitum): laboratory mouse chow pellets ad libitum
-Water (e.g. ad libitum): ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22-25°C
- Humidity (%):50-70%
- Photoperiod (hrs dark / hrs light): 12 / 12

Route of administration:

intraperitoneal

Vehicle:

other: 0.9% saline

Details on exposure:

intraperitoneal injections, once daily between 08:00 and 09:00 a.m.

Details on analytical verification of doses or concentrations:

no data

Details on mating procedure:

mice bought already mated

Duration of treatment / exposure:

day 1-17 of gestation

Frequency of treatment:

daily

Duration of test:

until day 18 of gestation

Dose / conc.:

8 mg/kg bw/day (nominal)

Remarks:

= 0.25 mmol/kg bw

Dose / conc.:

31 mg/kg bw/day (nominal)

Remarks:

= 1 mmol/kg bw

Dose / conc.:

78 mg/kg bw/day (nominal)

Remarks:

= 2.5 mmol/kg bw

Dose / conc.:

155 mg/kg bw/day (nominal)

Remarks:

= 5.0 mmol/kg bw

No. of animals per sex per dose:

5 - 11

Control animals:

yes, concurrent vehicle

Details on study design:

- Six to eight pregnant mice were admininstered 0, 8, 31, 78, and 155 mg/kg bw methylamine by ip injection from day 1 to 17 after mating
- Results of untreated controls of three parallel experiments (n=29) were pooled

Maternal examinations:

- Maternal and fetal body weight, mortality, resorptions, litter size, and placental weight were recorded in the in-vivo part of the study

Ovaries and uterine content:

- Examination of uterine content: placental weight, resorptions, litter size
- Examination for obvious sign of implantations (uteri were stained in 10 % ammonium sulfide solution to identify implantation sites)

Fetal examinations:

- Examination of fetuses: viability, body weight, visceral and skeletal examination
pubs weight for each female were calculated by dividing the sum of body weights of all live pups in a litter by the number of live pubs in the litter
mean pub weight for each treatment group was based on sum of mean pup weight for each female divided by the number of females in the group
fetuses were randomly placed either in Bouin solution for visceral examination by the freehand razor sectioning technique or in 95 % ethanol for the skeletal examination by an alizarin red S staining technique.

Statistics:

- Statistical evaluation employed Student's t-test and Bonferroni test (multiple means)

Indices:

no data

Historical control data:

no data

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
- Methylamine hydrochloride did not produce maternal toxicity at concentrations up to 2.5 mmol/kg
- For evaluation the results of untreated controls of three parallel experiments (n=29) were pooled
- No dam died from methylamine hydrochloride treatment and maternal body weight development was within the range if the untreated control group
- No significant differences between control and treated animals were observed concerning fetal body weight, mortality, resorptions , litter size, or placental weight

Dose descriptor:

NOAEL

Effect level:

155 mg/kg bw/day

Basis for effect level:

other: no effects observed

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
- Methylamine hydrochloride did not have any significant effect on pregnancy outcome.
- Number of resorbed and dead fetuses were equally distributed across all doses of MMA hydrochloride.
- none of the amines (MMA, DMA, TMA) caused a significant increase in external, internal organ, or skeletal abnormalities.
- all three methylamines possess teratogenic potential in varying degrees.
- decrease of DNA, RNA, and protein after treatment of embryos with methylamines.

Dose descriptor:

NOAEL

Effect level:

155 mg/kg bw/day

Basis for effect level:

other: no effects observed

Abnormalities:

not specified

Developmental effects observed:

not specified

In vitro studies: all three methylamines produced concentration-dependent decreases in yolk-sac diameter, crown-rump length, head length, and fetal survival; developmental score and somite number also exhibited a similar concentration-dependent decrease.

The effect of all the three methylamines was more marked on the head length than on crown-rump length and yolk-sac diameter.

the external appearance of embryos was not affected by low concentrations of methylamines. At higher concentrations (> 0.5 mM), there appeared to be a dispropotionate retardation in forelimb and branchial bar development relative to the development of other organs. All embryos were dorsally convex at 1 mM MMA HCl or DMA HCl.

The development of hearts was unaffected at concentrations up to 1 mM of all 3 methylamines and neuropores closed well up to concentrations of 0.75 mM.

All three methylamines produced concentration-dependent decreases in embryo RNA, DNA and proteins; the realtive order of toxicity was the same as in vivo, namely TMA> DMA > MMA.

Conclusions:

The NOAEL for maternal and developmental toxicity, including teratogenicity, was 155 mg/kg bw Methylammonium chloride based on the absence of any adverse findings at this dose.

Executive summary:

Reproductive toxicity

In a toxicity study in mice no effect of intraperitoneal monomethylamine hydrochloride administration (from day 1 to 17 of gestation) on body weights and food consumption of the females and on organ weights were observed up to 155 mg/kg bw. From the above, it was considered that reproductive/developmental toxicity NOEL is 155 mg/kg bw/day for Methylammonium chloride for female mice. 

Developmental toxicity

A study performed by Guest et al. in 1991, dealt with the investigation of maternal or fetal effects after administration of Methylammonium chloride via intraperitoneal injection. The numbers of resorbed and dead fetuses were equally distributed across all doses of Methylammonium chloride, and, therefore, are considered not to be treatment related. None of the amines (MMA, DMA, TMA) caused a significant increase in external, internal organ, or skeletal abnormalities, but all three possess a teratogenic potential in varying degrees in in vitro experiments on mouse embryos. Monomethylamine hydrochloride did not exert any fetal effects at the highest dose level tested. In vitro, all three methylamines produced concentration-dependent decreases in yolk-sac diameter, crown-rump length, head length, and fetal survival; developmental score and somite number also exhibited a similar concentration-dependent decrease. The external appearance of the embryos was not affected by low concentrations of methylamines, but at higher concentrations (> 0,5 mM), there appeared a disproportionate retardation in the forelimb and branchial bar development relative to the development of other organs. So, Methylammonium chloride inhibits the development of mouse embryos in culture.

Effect on developmental toxicity: via oral route

Dose descriptor:

NOAEL

155 mg/kg bw/day

Species:

mouse

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

Developmental toxicity

A study performed by Guest et al. in 1991, dealt with the investigation of maternal or fetal effects after administration of Methylammonium chloride via intraperitoneal injection. The numbers of resorbed and dead fetuses were equally distributed across all doses of Methylammonium chloride, and, therefore, are considered to not be treatment related. None of the amines (MMA, DMA, TMA) caused a significant increase in external, internal organ, or skeletal abnormalities, but all three possess a teratogenic potential in varying degrees in in vitro experiments in mouse embryos. Monomethylamine hydrochloride did not exert any fetal effects at the highest dose level tested. In vitro, all three methylamines produced concentration-dependent decreases in yolk-sac diameter, crown-rump length, head length, and fetal survival; developmental score and somite number also exhibited a similar concentration-dependent decrease. The external appearance of the embryos was not affected by low concentrations of methylamines, but at higher concentrations (> 0,5 mM), there appeared a disproportionate retardation in the forelimb and branchial bar development relative to the development of other organs. So, Methylammonium chloride inhibits development of mouse embryos in culture.

Justification for classification or non-classification

MMA and MMA HCl induced maternal toxicity at dose levels at which common systemic toxicity was observed. Developmental toxicity findings are considered to be a secondary consequence of maternal toxicity. Embryotoxicity occurred at dose level associated with maternal toxicity. MMA / MMA HCl do not possess teratogenicity potential in rats and mice studies.

The classification is not warranted according to the criteria of EU Classification, Labeling and Packaging of Substances and Mixtures (CLP) Regulation No 1272/2008.