2-ethylhexanoic acid, manganese salt

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

Species:

rat

Additional information

Read-across approach

Selected endpoints for the human health hazard assessment are addressed by read-across, using a combination of data on the metal cation and the organic acid anion. This way forward is acceptable, since metal carboxylates are shown to dissociate to the organic anion and the metal cation upon dissolution in aqueous media. No indications of complexation or masking of the metal ion through the organic acid were apparent during the water solubility and dissociation tests (please refer to the water solubility and dissociation in sections 4.8 and 4.21 of IUCLID). Once the individual transformation products of the metal carboxylate become bioavailable (i.e. in the acidic environment in the gastric passage or after phagocytosis by pulmonary macrophages), the “overall” toxicity of the dissociated metal carboxylate can be described by a combination of the toxicity of these transformation products, i.e. the metal cation and carboxylate anion according to an additivity approach.

 

2-ethylhexanoic, manganese salt is the manganese metal salt of 2-ethylhexanoic acid, which readily dissociates to the corresponding divalent manganese cation and 2-ethylhexanoic acid anions. The manganese cation and the 2-ethylhexanoic acid anion are considered to represent the overall toxicity of 2-ethylhexanoic, manganese salt in a manner proportionate to the free acid and the metal (represented by one of its readily soluble salts). 

 

A detailed justification for the read-across approach is added as a separate document in section 13 of IUCLID.

 

Toxicity for reproduction– effects on fertility

No toxicity data on adverse effects on sexual function and fertility with 2-ethylhexanoic acid, manganese salt is available, thus the reproductive toxicity will be addressed with existing data on the dissociation products as detailed in the table below. Further details on the reproductive toxicity of the individual constituents are given below.

 

Table: Summary of toxicity data on adverse effects on sexual function and fertility of 2-ethylhexanoic acid, manganese salt and the individual constituents.

	Manganese sulfate (CAS# 7785-87-7)	2-ethylhexanoic acid (CAS# 149-57-5)	2-ethylhexanoic, manganese salt (CAS#15956-58-8)
Repeated dose toxicity data	Not adverse effects on reproductive organs observed (chronic study, rat)   NOAEL(rat, male)= 615 mg MnSO4/kg bw/day   NOAEL(rat, male)= 715 mg MnSO4/kg bw/day   NOAEL(rat, male)= 224 mg Mn/kg bw/day   NOAEL(rat, male)= 260 mg Mn/kg bw/day	See section on repeated dose toxicity	See section on repeated dose toxicity
Two-generation reproductive toxicity study	Not reprotoxic (weight of evidence, animal data) Not classified	NOAEL(rat; F1) = 100 mg/kg bw/day* NOAEL(rat; P) = 300 mg/kg bw/day   Not classified	No data   Not classified

* Identified as most sensitive endpoint in the registration dossier for 2-ethylhexanoic acid, i.e. has been used for the DNEL derivation of this substance.

 

Manganese (information taken from SCOEL, 2011)

Although evidence is limited, the carcinogenicity, mutagenicity, genotoxicity, and reproductive toxicity profiles for manganese and its compounds do not suggest that these aspects are key to an evaluation of occupational exposure standards.

 

Manganese (information taken from IEH, 2004)

In an NTP 2-year feeding study on Fischer 344 rats and B6C3F1 mice, there were no changes in testes weight noted and no effects on the seminiferous vesicles with manganese sulphate fed in the diet at concentrations of up to 15 000 ppm (NTP, 1993).

In a study only briefly described, Kar et al. (1972) treated rats with 8 mg manganese chloride (8 mg/kg bw) intraperitoneally, daily. Testicular manganese content was determined together with levels of amino acids after 30 and 60 days. Manganese content of the testes showed a 4- and 9-fold increase respectively and after 60 days there were increases in alanine, cysteine, leucine, proline, phenylalanine and glutamine, as compared to controls. The authors concluded that manganese showed evidence of an effect on metabolism in the testes much earlier than changes in histology.

Laskey et al. (1982) chronically treated Long-Evans rats with manganese (II,III) oxide Mn3O4 beginning on day 1 of gestation up to 224 days of age. The manganese was administered in low or high iron diets at concentrations of 350, 1050 and 3050 ppm. The highest manganese level with low iron was stopped after 40 days as there were 50% fatalities. The highest concentration with sufficient iron in the diet, showed some reduction in fertility and the higher doses showed some minimal effects on male reproductive development as measured by testes weight, sperm count and serum follicle stimulating hormone and testosterone. None of these effects was severe enough to alter functional reproduction.

Laskey et al. (1985) described a study in which Long-Evans rats were dosed orally from birth to 21 days with particulate manganese (II,III) oxide (Mn3O4) at doses of 0, 71 or 214 μg/kg bw/day. Assessments were made of hypothalamic, pituitary and testicular function by the measurement of endogenous and stimulated serum concentrations of the pituitary hormones, luteinising hormone and follicle stimulating hormone, and testosterone after 21 and 28 days. There were no significant dose or time-dependent changes in body or testes weight or in follicle stimulating hormone or luteinising hormone levels. There was a significant reduction in serum testosterone after 7 days of stimulation with human chorionic gonadotropin and the authors suggested that any effect is at the level of the testicular Leydig cell and there are no effects on the hypothalamus or pituitary. The hypothalamic manganese concentration seen in these animals is three times that seen in other studies where alterations in the dopaminergic systems have been reported.

In a further study, male Sprague-Dawley rats were fed manganese sulphate (1000 ppm) in drinking water for 12 weeks and territorial aggression, sexual behaviour and fertility were then investigated. There was a decrease in territorial aggression in the treated rats and some slight effects on sexual behaviour, elongation in the time to ejaculation and post-ejaculation. There were no changes in fertility but an increase was seen in the number of resorptions (Bataineh et al., 1998).

New-born CD-1 mice were chronically exposed to manganese oxide for 58, 73 or 90 days. The control diet contained 50 ppm manganese sulphate while the treated mice were exposed to a further 1050 ppm manganese as manganese (IV) oxide. The mice were tested for reactive locomotor activity and sexual development. While body, liver and kidney weights remained unchanged, the growth of the testes, seminal vesicles and preputial glands were retarded. The activity of the rats in a maze over a 2-hour period was significantly reduced at 73 days (Gray & Laskey, 1980).

Joardar and Sharma (1990) compared the cytogenetic and clastogenetic effects of cationic (manganese sulphate) and anionic (potassium permanganate) salts of manganese in male Swiss mice. The manganese sulphate concentrations used were 610, 205 and 102.5 mg/kg bw and potassium permanganate, 380, 130 and 65 mg/kg bw. These concentrations constituted 1/5, 1/15 and 1/30 of a previously experimentally derived LD50 although no details are given. Among the endpoints measured was sperm-head abnormality in five animals for each treatment, administered orally for 5 days then killed after 35 days; 500 sperm were assessed for each animal. There was a significant trend for increased sperm head abnormalities for both manganese sulphate and potassium permanganate.

Fertility was estimated in male Swiss mice exposed for 12 weeks to 1000, 2000, 4000 or 8000 mg/ℓ manganese chloride in drinking water (Elbetieha et al., 2001). Mice were then mated for 10 days with unexposed females, which were then killed after a further 10 days and the number of pregnant females, implantation sites, viable fetuses and resorptions recorded. Fertility was significantly reduced in males exposed to 8000 mg/ℓ although there were no changes in the other parameters. In a further experiment, female mice were exposed to the same concentrations of manganese chloride for 12 weeks and then mated with unexposed males for 10 days and killed after a further 10 days as before. Fertility was not reduced in any treatment group but the numbers of implantation sites and viable fetuses were significantly reduced in the highest dose group (8000 mg/ℓ).

Rabbits were treated with single intratracheal injection of manganese dioxide (250 mg/kg bw) and killed at 4 and 8 months for histological and biochemical analysis. After 8 months, groups of treated and untreated rabbits were also tested for fertility. After 4 months, there were signs of degeneration in about 30% of seminiferous tubules, while at 8 months there was extensive disruption of the tubules with marked degeneration of spermatocytes and spermatids. This was accompanied by infertility. There were decreased levels of enzymes found in the testes of the treated rabbits — acid phosphatase (27%), adenosine triphosphatase (38%), succinic dehydrogenase (78%). The authors suggested that manganese affected the energy metabolism in the testes leading to the destruction of sperm producing structures (Chandra et al., 1973b). In a further study by the same group (Imam & Chandra, 1975), male rabbits received daily intravenous injections of 3.5 mg manganese chloride /kg bw for 5, 10, 15 and 30 days before killing. The testes then underwent histological and histochemical analysis. Again there was a decrease in succinic dehydrogenase and a decrease in glucose-6-phosphate dehydrogenase in the seminiferous tubules with increasing degeneration from day 5 onward.

Huang et al. (2001) showed that manganese nitrate inhibited sperm motility in vitro at a concentration of 500 ppm. However, there was no evidence of accompanying lipid peroxidation, measured by the production of malondialdehyde and indicative of free radical damage. The authors concluded that this effect on sperm motility at high concentration was not biologically or environmentally relevant.

 

2-Ethylhexanoic acid

2-Ethylhexanoic acid was administered via drinking water to an unspecified number of male and female rats at 0, 100, 300, or 600 mg/kg bw/day. There were no deaths. The relative epididymal weights in high-dose males were significantly increased, but no histological changes were noted. A slight, but not statistically significant increase in the number of abnormal sperm was noted in the highest two dose groups; however, the incidence per animal was not provided. Treated groups required more time to successfully complete mating, and the mean litter size in high-dose pregnant females was significantly reduced. The mean pup weights in the high-dose group were significantly lower on postnatal day 7 and 14. Mean fetal weight per litter and mean placental weights were significantly reduced in the mid- and high-dose groups. Clubfoot was the only skeletal malformation; changes in skeletal variations were also noted (wavy ribs, reduced cranial ossification, and twisted hind legs). Corrected maternal body weights at termination and weight gains of high-dose females were significantly reduced. Physical development of the eyes, teeth and hair appeared to be slightly later in the pups from the high-dose groups; the significance of this finding is unclear since no data were presented on the length of gestation in treated and control dams. The high-dose of 600 mg/kg bw/day significantly reduced overall water consumption and body weights in female animals. The NOAEL for reproductive effects in parental animals was 300 mg/kg bw/day; this effect occurred in the presence of maternal toxicity. The NOAEL for F1 offspring was 100 mg/kg bw/day. Based on these results, 2-ethylhexanoic acid is not likely to cause effects on fertility but is likely to be a developmental toxicant. The developmental toxicity of 2-ethylhexanoic acid is at least partially related to disruption of Zn metabolism and distribution in the mother, and that higher zinc levels in the mothers leads to lower developmental toxicity in offspring.

 

2-ethylhexanoic acid, manganese salt

Since no toxicity data on adverse effects on sexual function and fertility is available for 2-ethylhexanoic acid, manganese salt, information on the individual constituents manganese and 2-ethylhexanoic acid will be used for the hazard assessment and, when applicable, for the risk characterisation of 2-ethylhexanoic acid, manganese salt. For the purpose of hazard assessment of 2-ethylhexanoic acid, manganese salt, the point of departure for the most sensitive endpoint of each constituent will be used for the DNEL derivation.

 

2-ethylhexanoic acid, manganese salt is not expected to show adverse effects on sexual function and fertility, since the two constituents manganese and 2-ethylhexanoic acid have not shown adverse effects on sexual function and fertility in relevant bioassays. Thus, 2-ethylhexanoic acid, manganese salt is not to be classified according to regulation (EC) 1272/2008 as reproductive toxicant: fertility impairment. Further testing is not required. For further information on the toxicity of the individual constituents, please refer to the relevant sections in the IUCLID and CSR.

Short description of key information:
2-ethylhexanoic acid, manganese salt is not expected to show adverse effects on sexual function and fertility.

Justification for selection of Effect on fertility via oral route:
Information from read-across substances:
animal data for manganese: not reprotoxic (weight of evidence)
animal data for 2-ethylhexanoic acid: NOAEL(rat, F1)=100mg/kg bw/day

Effects on developmental toxicity

Description of key information

2-ethylhexanoic acid, manganese salt is expected to be a developmental toxicant.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

Species:

rat

Additional information

Read-across approach

 

Selected endpoints for the human health hazard assessment are addressed by read-across, using a combination of data on the metal cation and the organic acid anion. This way forward is acceptable, since metal carboxylates are shown to dissociate to the organic anion and the metal cation upon dissolution in aqueous media. No indications of complexation or masking of the metal ion through the organic acid were apparent during the water solubility and dissociation tests (please refer to the water solubility and dissociation in sections 4.8 and 4.21 of IUCLID). Once the individual transformation products of the metal carboxylate become bioavailable (i.e. in the acidic environment in the gastric passage or after phagocytosis by pulmonary macrophages), the “overall” toxicity of the dissociated metal carboxylate can be described by a combination of the toxicity of these transformation products, i.e. the metal cation and carboxylate anion according to an additivity approach.

  

2-ethylhexanoic, manganese salt is the manganese metal salt of 2-ethylhexanoic acid, which readily dissociates to the corresponding divalent manganese cation and 2-ethylhexanoic acid anions. The manganese cation and the 2-ethylhexanoic acid anion are considered to represent the overall toxicity of 2-ethylhexanoic, manganese salt in a manner proportionate to the free acid and the metal (represented by one of its readily soluble salts). 

 

 A detailed justification for the read-across approach is added as a separate document in section 13 of IUCLID.

 

 

Toxicity for reproduction – developmental toxicity

No toxicity data on adverse effects on development of the offspring with 2-ethylhexanoic acid, manganese salt are available, thus the reproductive toxicity will be addressed with existing data on the dissociation products as detailed in the table below. Further details on the genetic toxicity of the individual constituents are given below.

 

Table: Summary of toxicity data on adverse effects on development of the offspring of 2-ethylhexanoic acid, manganese salt and the individual constituents.

	Manganese sulfate (CAS# 7785-87-7)	2-ethylhexanoic acid (CAS# 149-57-5)	2-ethylhexanoic, manganese salt (CAS#15956-58-8)
Pre-natal developmental toxicity study	NOAEL(rat; mat.)> 1004 mg MnSO4/kg bw/day   NOAEL(rat; dev)> 1004 mg MnSO4/kg bw/day	NOAEL(rat; mat.)= 250 mg/kg   NOAEL(rat; dev)= 100 mg/kg*   Category 2, H361d (CLP)	No data   Self-classified Category 2, H361d (CLP)
Two-generation reproductive toxicity study	No data	NOAEL(rat; F1) = 100 mg/kg bw/day* NOAEL(rat; P) = 300mg/kg bw/day   not classified	No data

* Identified as most sensitive endpoint in the registration dossier for 2-ethylhexanoic acid, i.e. has been used for the DNEL derivation of this substance.

 

Manganese (information taken from SCOEL, 2011)

Although evidence is limited, the carcinogenicity, mutagenicity, genotoxicity, and reproductive toxicity profiles for manganese and its compounds do not suggest that these aspects are key to an evaluation of occupational exposure standards.

 

Manganese (information taken from IEH, 2004)

Female weanling Sprague-Dawley rats were fed manganese sulphate in the diet at 4, 24, 54, 154, 504 and 1004 mg/kg dry diet (Järvinen & Ahlström, 1975). After 8 weeks they were mated with males of the same strain and after 21 days the animals and fetuses were killed and examined. No gross malformation, bone structure abnormality or altered fetal weight was observed. A clear increase in fetal manganese concentration could only be seen in the highest dose (1004 mg/kg). There was no maternal toxicity.

 

In a study by Webster and Valois (1987) pregnant female mice were treated with a single intraperitoneal injection of 12.5, 25 or 50 mg manganese sulphate on day 8, 9 or 10 of pregnancy. On day 8, the highest dose was embryolethal and the other doses induced a low incidence of neural tube defects in the surviving fetuses. The 25 mg dose caused maternal toxicity, coinciding with peak blood concentrations of 1000 ng/mℓ for 30 minutes. Blood levels exceeded 100 ng/mℓ for 24 hours. When manganese was incubated with rat embryos for 48 hours, 25 and 50 ng/mℓ had no effect while there was no survival at 100 ng/mℓ. They also looked at postnatal brain manganese after a single dose of 54Mn and found that manganese entered the fetal and neonatal brain more easily than the adult brain.

 

2-Ethylhexanoic acid

2-Ethylhexanoic acid was administered via drinking water to an unspecified number of male and female rats at 0, 100, 300, or 600 mg/kg bw/day. There were no deaths. The relative epididymal weights in high-dose males were significantly increased, but no histological changes were noted. A slight, but not statistically significant increase in the number of abnormal sperm was noted in the highest two dose groups; however, the incidence per animal was not provided. Treated groups required more time to successfully complete mating, and the mean litter size in high-dose pregnant females was significantly reduced. The mean pup weights in the high-dose group were significantly lower on postnatal day 7 and 14. Mean fetal weight per litter and mean placental weights were significantly reduced in the mid- and high-dose groups. Clubfoot was the only skeletal malformation; changes in skeletal variations were also noted (wavy ribs, reduced cranial ossification, and twisted hind legs). Corrected maternal body weights at termination and weight gains of high-dose females were significantly reduced. Physical development of the eyes, teeth and hair appeared to be slightly later in the pups from the high-dose groups; the significance of this finding is unclear since no data were presented on the length of gestation in treated and control dams. The high-dose of 600 mg/kg bw/day significantly reduced overall water consumption and body weights in female animals. The NOAEL for reproductive effects in parental animals was 300 mg/kg bw/day; this effect occurred in the presence of maternal toxicity. The NOAEL for F1 offspring was 100 mg/kg bw/day. Based on these results, 2-ethylhexanoic acid is not likely to cause effects on fertility but is likely to be a developmental toxicant. The developmental toxicity of 2-ethylhexanoic acid is at least partially related to disruption of Zn metabolism and distribution in the mother, and that higher calcium levels in the mothers leads to lower developmental toxicity in offspring. Based on the above given information, 2-ethylhexanoic acid was classified as toxic for reproduction, developmental toxicity category 2 (H361d/R62).

 

2-ethylhexanoic acid, manganese salt

Since no reproductive toxicity study is available for 2-ethylhexanoic acid, manganese salt, information on the individual constituents manganese and 2-ethylhexanoic acid will be used for the hazard assessment and, when applicable, for the risk characterisation of2-ethylhexanoic acid, manganese salt. For the purpose of hazard assessment of 2-ethylhexanoic acid, manganese salt, the point of departure for the most sensitive endpoint of each constituent will be used for the DNEL derivation. In case of 2-ethylhexanoic acid in2-ethylhexanoic acid, manganese salt, the NOAEL of 100 mg/kg bw/day for the reproductive toxicity in the F1 offspring will be used.

 

Considering the read-across principles as detailed above for2-ethylhexanoic acid, manganese salt based on the toxicological assessment of the individual constituents, it is therefore proposed to also read-across the classification of toxic for reproduction, developmental toxicity category 2 (H361d/R63) of 2-ethylhexanoic acid to2-ethylhexanoic acid, manganese salt.

Justification for selection of Effect on developmental toxicity: via oral route:
Information from read-across substances:
Animal data for manganese: NOAEL(rat)>1004 mg MnSO4/kg bw/day
animal data for 2-ethylhexanoic acid: NOAEL(rat, F1)=100mg/kg bw/day

Justification for classification or non-classification

2-ethylhexanoic acid, manganese salt is not expected to show adverse effects on sexual function and fertility, since the two constituents manganese and 2-ethylhexanoic acid have not shown adverse effects on sexual function and fertility in relevant bioassays. Thus, 2-ethylhexanoic acid, manganese salt is not to be classified according to regulation (EC) 1272/2008 as reproductive toxicant: fertility impairment.

Considering the read-across principles as detailed above for 2-ethylhexanoic acid, manganese salt based on the toxicological assessment of the individual constituents, it is therefore proposed to also read-across the classification of toxic for reproduction, developmental toxicity category 2 (H361d) of 2-ethylhexanoic acid to 2-ethylhexanoic acid, manganese salt.