Trimanganese bis(orthophosphate)

Endpoint summary

Description of key information

Trimanganese bis(orthophosphate) does not show adverse effects in chronic oral repeated dose toxicity studies in animals. Solely reversible adverse relative liver weight changes were reported.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Introduction to read-across approach

During the literature search and data gap analysis it became obvious that the overall database on substance-specific human health hazard data for trimanganese bis(orthophosphate) is too scant to cover all REACH endpoints. Therefore, the remaining data gaps had to be covered by either experimental testing or read-across from similar substances.

Selected endpoints for the human health hazard assessment are addressed by read-across, using a combination of data on the phosphate moiety and the manganese moiety (or one of its readily soluble salts). This way forward is acceptable, since trimanganese bis(orthophosphate) dissociates to the phosphate anion and the manganese cation upon dissolution in aqueous media.

Manganese exists in various oxidation states (i.e. -3 to +7), from which Mn²⁺and Mn³⁺were relevant in biological systems.As to the speciation of manganese under physiological conditions, Mn²⁺must be assumed to be the prevailing species under mildly acidic conditions according to the Pourbaix diagram for manganese.

In accordance with ATSDR, 2012:

Manganese is capable of existing in a number of oxidation states, and limited data suggest that inorganic manganese may undergo changes in oxidation state within the body. Circumstantial support for this hypothesis comes from the observation that the oxidation state of the manganese ion in several enzymes appears to be Mn(III) (Leach and Lilburn 1978; Utter 1976), while most manganese intake from the environment is either as Mn(II) or Mn(IV). Another line of evidence is based on measurements of manganese in tissues and fluids using electron spin resonance (ESR), which detects the unpaired electrons in Mn(II), Mn(III), and Mn(IV). When animals were injected with manganese chloride, levels of manganese increased in bile and tissues, but only a small portion of this was in a form that gave an ESR signal (Sakurai et al. 1985; Tichy and Cikrt 1972). This suggests that Mn(II) is converted to another oxidation state (probably Mn(III)), but it is also possible that formation of complexes between Mn(II) and biological molecules (bile salts, proteins, nucleotides, etc.) results in loss of the ESR signal without oxidation of the manganese ion. Evidence by Gibbons et al. (1976) suggests that oxidation of manganese occurs in the body. It was observed that human ceruloplasmin led to the oxidation of Mn(II) to Mn(III) in vitro, and although the process was not studied in vivo, it is a likely mechanism for manganese oxidation in the blood. These authors also noted that manganese oxidation led to a shift in manganese binding in vitro from α2-macroglobulin to transferrin and that in vivo clearance of Mn(II)-α2-macroglobulin from cows was much more rapid than the clearance of Mn(III)-transferrin (Gibbons et al. 1976). This suggests that the rate and extent of manganese reduction/oxidation reactions may be important determinants of manganese retention and toxicity in the body. Reaney et al. (2006) compared brain concentrations of manganese, dopamine, and gamma amino butyric acid in female retired breeder Long Evans rats exposed to cumulative intraperitoneal doses of 0, 30, or 90 mg manganese/kg of Mn(II) chloride or Mn(III) pyrophosphate. Rats were given intraperitoneal doses of 0, 2, or 6 mg manganese/kg, 3 times/week for 5 weeks. In Mn(III)-treated rats, brain manganese concentrations (analyzed in the striatum, globus pallidus, thalamus, and cerebrum regions) and blood concentrations were higher than brain concentrations in Mn(II)-treated rats. The only other marked changes in end points between the two treatment groups was that the highest Mn(III) exposure group showed a 60% increased dopamine level in the globus pallidus (compared with controls), whereas the comparably treated Mn(II) rats showed a 40% decrease in globus pallidus dopamine level. These results suggest that manganese valence state can influence tissue toxicokinetic behavior, and possibly toxicity.

 

 

Once the individual constituents of trimanganese bis(orthophosphate) become bioavailable (i.e. in the acidic environment in the gastric passage or after phagocytosis by pulmonary macrophages), the “overall” toxicity of the dissociated substance can be described by the toxicity of the “individual” constituents. Since synergistic effects are not expected, the human health hazard assessment consists of an individual assessment of the manganese cation and the phosphate anion.

The hazard information of the individual constituents was obtained from publicly available literature (i.e. EFSA documents, ATSDR toxicological profile and WHO recommendations for human nutrition).

Trimanganese bis(orthophosphate) readily dissociates to the corresponding manganese cations and phosphate anions. The manganese cation and the phosphate anion are considered to represent the overall toxicity of trimanganese bis(orthophosphate) in a manner proportionate to the phosphate and the metal (represented by one of its readily soluble salts). Based on the above information, unrestricted read-across is considered feasible and justified.

Manganese

In a chronic feeding study, male and female F344/N rats were given doses of 1500, 5000, and 15000 ppm of manganese (II) sulfate monohydrate (actual dose received: 60, 200, and 615 mg/kg/day for males and 70, 230, and 715 mg/kg/day for females, respectively). Ten animals per sex and group were sacrificed after 9 months and 15 months of test item exposure, the remaining animals were sacrificed at the end of the study. The mean body weights of 15,000 ppm male rats were within 5% of that of controls until week 89. From week 89, the mean body weights ranged from 8% to 13% lower than that of controls; at the end of the 2-year study, the final mean body weight of 15,000 ppm males was 10% lower than that of controls. Mean body weights of exposed females were similar to that of controls throughout the study. Chronic nephropathy occurred in all male rats examined at both interim evaluations and most of the control and exposed males at the end of the study. The average severity of nephropathy was slightly greater in the high-dose group, but the difference was not statistically significant. No test item-related effects were found for clinical signs, body weight, food consumption, haematology (interim sacrifices), clinical chemistry (interim sacrifices), organ weights (interim sacrifices), and histopathology. At both the 9- and 15-month interim evaluations, significantly increased manganese concentrations were observed in livers of the 5000 and 15000 ppm dose groups (males and females), accompanied with depression of hepatic manganese. Based on the absence of any adverse effects related to the test substance, a No Observed Adverse Effect Level (NOAEL) for test item of 15000 ppm (actual dose received: 615 mg/kg/day for males and 715 mg/kg/day for females (200 and 233 mg Mn/kg/day, respectively) was concluded for male and female rats.

In a chronic feeding study, male and female B6C3F1 mice were given doses of 1500, 5000, and 15000 ppm of manganese (II) sulfate monohydrate (actual dose received: 160, 540, and 1800 mg/kg/day for males and 200, 700, and 2250 mg/kg/day for females, respectively). Ten animals per sex and group were sacrificed after 9 months and 15 months of test item exposure, the remaining animals were sacrificed at the end of the study. The mean body weights of exposed males were similar to those of the control group. After week 37, mean body weights of all exposed groups of females were lower than that of the controls; the final mean body weights for the 1,500, 5,000, and 15,000 ppm groups were 6%, 9%, and 13% lower than that of the control group. No treatment-related effects were observed for clinical chemistry and organ weights. The haematological evaluation revealed that the percent hematocrit, hemoglobin concentrations, and erythrocyte counts in 15000 ppm male mice at the 15-month interim evaluation were greater than those of the controls. The significance of this finding is uncertain. Thyroid follicular dilatation and focal hyperplasia as well as focal squamous hyperplasia in the forestomach accompanied by ulceration/erosion and inflammation were statistically increased in the high-dose animals and considered to be treatment-related findings. No significant increase in the incidence of neoplasia in mice could be found. Based on the histopathological findings in the thyroid (follicular dilatation and focal hyperplasia), decreased final body weight in females, and haematological findings in the male mice at the 15000 ppm dose level, a No Observed Adverse Effect Level (NOAEL) for test item of 5000 ppm (actual dose received: 540 mg/kg/day for males and 700 mg/kg/day for females (172.8 and 224 mg Mn/kg/day, respectively)) was concluded for male and female mice.

 

Phosphate

A registration dossier shall contain information on the human health hazard assessment (regulation 1907/2006, Art.10). However, it is considered that the information requirements for orthophosphate as laid down in annex VII to IX can be fulfilled by adaptation of the standard testing regime according to Annex XI, points 1.1.3, 1.2, as presented in the following:

Phosphorus is most commonly found as the phosphate ion, with phosphorus in its pentavalent form. Thus, in the following the term phosphorus refers to phosphate, including its major form orthophosphate.

(1) A large part of human nutrition consists of phosphorus as cited by EFSA, 2015:

The major dietary contributors to phosphorus intake are foods high in protein content, i.e. milk and milk products followed by meat, poultry and fish, grain products and legumes. Based on data from 13 dietary surveys in nine European Union countries, mean phosphorus intakes range from 265 to 531 mg/day in infants, from 641 to 973 mg/day in children aged 1 to < 3 years, from 750 to 1202 mg/day in children aged 3 to < 10 years, from 990 to 1601 mg/day in children aged 10 to < 18 years and from 1000 to 1767 mg/day in adults (≥18 years).(EFSA, 2015)

(2)The EFSA concluded on phosphorus:

The available data [derived from short and long term studies in rodents and humans, and summarised by EFSA, 2005] indicate that normal healthy individuals can tolerate phosphorus intakes up to at least 3000 mg phosphorus per day without adverse systemic effects. In some individuals, however, mild gastrointestinal symptoms, such as osmotic diarrhoea, nausea and vomiting, have been reported if exposed to supplemental intakes >750 mg phosphorus per day. Estimates of current intakes of phosphorus in European countries indicate total mean dietary and supplemental intakes around 1000-1500 mg phosphorus per day, with high (97.5 percentile) intakes up to around 2600 mg phosphorus per day. There is no evidence of adverse effects associated with the current intakes of phosphorus.(EFSA, 2005)

A detailed evaluation of the underlying single studies is not provided here, in order to avoid unnecessary duplication of the work already performed by an EU-nominated expert body. Based on the findings evaluated in the EFSA document, an upper intake level (UL) cannot be established based on the effect of a high phosphorus intake on the activity of calcium regulating hormones, which the expert body considers not to be adverse in themselves, and which have no demonstrable effects on bone mineral density and skeletal mass. (EFSA, 2005)

Based on the above given arguments, one may safely assume that human exposure towards phosphorus substances exerts any adverse effects of toxicological relevance after chronic exposure.

In conclusion, the conduct of any further toxicity studies with chronic exposure in animals would not contribute any new information and is therefore not considered to be required.

A registration dossier shall contain information on the human health hazard assessment (regulation 1907/2006, Art.10). However, it is considered that the information requirements for orthophosphate as laid down in annex VII to IX can be fulfilled by adaptation of the standard testing regime according to Annex XI, points 1.1.3, 1.2, as presented in the following:

Phosphorus is most commonly found as the phosphate ion, with phosphorus in its pentavalent form. Thus, in the following the term phosphorus refers to phosphate, including its major form orthophosphate.

(1) A large part of human nutrition consists of phosphorus as cited by EFSA, 2015:

The major dietary contributors to phosphorus intake are foods high in protein content, i.e. milk and milk products followed by meat, poultry and fish, grain products and legumes. Based on data from 13 dietary surveys in nine European Union countries, mean phosphorus intakes range from 265 to 531 mg/day in infants, from 641 to 973 mg/day in children aged 1 to < 3 years, from 750 to 1202 mg/day in children aged 3 to < 10 years, from 990 to 1601 mg/day in children aged 10 to < 18 years and from 1000 to 1767 mg/day in adults (≥18 years).(EFSA, 2015)

(2)The EFSA concluded on phosphorus:

The available data[derived from short and long term studies in rodents and humans, and summarised by EFSA, 2005]indicate that normal healthy individuals can tolerate phosphorus intakes up to at least 3000 mg phosphorus per day without adverse systemic effects. In some individuals, however, mild gastrointestinal symptoms, such as osmotic diarrhoea, nausea and vomiting, have been reported if exposed to supplemental intakes >750 mg phosphorus per day. Estimates of current intakes of phosphorus in European countries indicate total mean dietary and supplemental intakes around 1000-1500 mg phosphorus per day, with high (97.5 percentile) intakes up to around 2600 mg phosphorus per day. There is no evidence of adverse effects associated with the current intakes of phosphorus.(EFSA, 2005)

A detailed evaluation of the underlying single studies is not provided here, in order to avoid unnecessary duplication of the work already performed by an EU-nominated expert body. Based on the findings evaluated in the EFSA document, an upper intake level (UL) cannot be established based on the effect of a high phosphorus intake on the activity of calcium regulating hormones, which the expert body considers not to be adverse in themselves, and which have no demonstrable effects on bone mineral density and skeletal mass. (EFSA, 2005)

Based on the above given arguments, one may safely assume that human exposure towards phosphorus substances exerts any adverse effects of toxicological relevance after chronic exposure.

In conclusion, the conduct of any further toxicity studies with chronic exposure in animals would not contribute any new information and is therefore not considered to be required.

Trimanganese bis(orthophosphate)

Since no repeated dose toxicity study is available specifically for manganese phosphate, information on the individual constituents manganese and phosphate will be used for the hazard assessment and when applicable for the risk characterisation of manganese phosphate. For the purpose of hazard assessment of manganese phosphate, no hazard was identified for the individual assessment entities manganese and phosphate. Consequently, no hazard is identified for the assessment entity manganese phosphate.

References

 

Agency for Toxic Substances and Disease Registry (ATSDR): Toxicological profile for manganese. U.S: Departement of Health and Human Services, Public Health Service, ATSDR, 2012.

EFSA (2005): Opinion of the Scientific Panel on Dietetic Products, Nutrition and Allergies on a request from the Commission related to the Tolerable Upper Intake Level of Phosphorus, The EFSA Journal, 233, 1-19.

EFSA (2015): Scientific Opinion on Dietary Reference Values for phosphorus, EFSA Panel on Dietetic Products, Nutrition and Allergies. The EFSA Journal, 13(7): 4185.

Gibbons RA, Dixon SN, Hallis K, et al. 1976. Manganese metabolism in cows and goats. Biochim Biophys Acta 444:1-10.

 

Leach RM, Lilburn MS. 1978. Manganese metabolism and its function. World Rev Nutr Diet 32:123134.

Reaney SH, Bench G, Smith DR. 2006. Brain accumulation and toxicity of Mn(II) and Mn(III) exposures. Toxicol Sci 93(1):114-124.

 

Sakurai H, Nishida M, Yoshimura T, et al. 1985. Partition of divalent and total manganese in organs and subcellular organelles of MnCl2-treated rats studied by ESR and neutron activation analysis. Biochim Biophys Acta 841:208-214.

Tichy M, Cikrt M. 1972. Manganese transfer into the bile in rats. Arch Toxikol 29:51-58.

Utter MF. 1976. The biochemistry of manganese. Med Clin North Am 60:713-727.

Justification for classification or non-classification

STOT-RE, oral

Two chronic repeated dose toxicity studies in rats and mice are considered as the key study for repeated dose toxicity and will be used for classification.

Based on the histopathological findings in the thyroid (follicular dilatation and focal hyperplasia), decreased final body weight in females, and haematological findings in the male mice at the 15000 ppm dose level, a No Observed Adverse Effect Level (NOAEL) for test item of 5000 ppm (actual dose received: 540 mg/kg/day for males and 700 mg/kg/day for females (172.8 and 224 mg Mn/kg/day, respectively)) was concluded for male and female mice.

The classification criteria according to regulation (EC) 1272/2008 as specific target organ toxicant (STOT) – repeated exposure, oral are not met since the no observed adverse effect level (NOAEL) via oral application is above the guidance value for a Category 1 classification of 10 mg/kg bw/day and above the guidance value for a Category 2 classification of 100 mg/kg bw/day. For the reasons presented above, no classification for specific target organ toxicant (STOT) – repeated exposure, oral is required.

STOT-RE, inhalation

The classification criteria according to regulation (EC) 1272/2008 as specific target organ toxicant (STOT) – repeated exposure, inhalation are met. The assessment entity manganese used in the present hazard assessment is legally classified as STOT-RE Category 2 based on human evidence for neurological effects following life-time inhalation exposure towards various manganese substances. Consequently, the assessment entity trimanganese bis(orthophosphate) will also be classified as STOT-RE Category 2 via inhalation.