Registration Dossier

Administrative data

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
Study duration:
subchronic
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

Introductory remark – read-across

 

Read-across entails the use of relevant information from analogous substances (the ‘source’ information) to predict properties for the ‘target’ substance(s) under consideration. Substances whose physicochemical or toxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be considered as a category of substances. Structural similarity is a pre-requisite for any read-across approach under REACH (ECHA Read-Across Assessment Framework, 2015).

 

In accordance with Annex XI, 1.5 of the REACH regulation and the ECHA Guidance Read-Across Assessment Framework (ECHA, 2017), the similarities may be based on:

 

1) A common functional group (i.e. chemical similarity within the group);

2) Common precursors and/or likelihood of same breakdown products through physical and/or biological processes which result in structurally-similar degradation products (i.e. similarity through (bio) transformation); or

3) A constant pattern in the changing of the potency of the properties across the group (i.e. of physical-chemical and/or biological properties).

 

Due to the absence of substance specific information for the majority of substances within the cobalt category, the approach will read-across data from representative source substances to all other members of the read-across group.

 

Due to the route-specific toxicological properties of the cobalt category substances, several read-across groups are formed as shown in the table below:

 

 

Route

Read-across group

Cobalt category

oral-systemic

bioavailable cobalt substances group

inorganic poorly soluble

poorly soluble in aqueous solutions with organic ligand

inhalation-local

reactive

non-reactive

 

 

Further details on the read-across approach are given in Appendix 1.1 of the CSR for the oral systemic effects and Appendix 1.2 of the CSR for the inhalation local effects.

 

Cobalt metal is assigned to the read-across group for oral-systemic: bioavailable cobalt substances group.

 

 

 

Effects on fertility

 

Cobalt dichloride is the source substance for the soluble inorganic cobalt substances group based on the read-across approach as outlined in Appendix 1.1 in the CSR. Two soluble inorganic cobalt substances, cobalt dichloride and cobalt powder, have been tested for effects on fertility, resulting in an absence of effects on the reproductive organs of male and female animals up to the maximum tolerated dose. In all studies, the effect levels were based on similar findings, predominantly body weight effects and haematological findings.

 

In the sub-chronic repeated dose toxicity study, cobalt dichloride was given male and female rats at doses of 0, 3, 10, 30 mg/kg bw/day. A total of 10 males and 10 females per group were given the test items suspended in 0.5% hydroxypropyl methylcellulose gel orally via gavage once daily for 90 days. Additional 2 groups of 5 male and 5 female animals, dosed with 0, 30 mg/kg bw/day were assigned as recovery animals, kept for 28 days after the treatment period without receiving the test item. Additional examinations were added to the study design:

 

(i) monitoring of the oestrus cycle pre-dose, during study conduct, at the end of test week 13 and at the end of the recovery period in all female animals

(ii) hormone level status (testosterone, progesterone, 17beta-estradiol) pre-dose, during study conduct, at the end of test week 13 and at the end of the recovery period in all animals

(iii) Detailed histopathologic examination on one testicle and one epididymis (with special emphasis on the qualitative stages of spermatogenesis and histopathology of interstitial testicular structure)

 

During the conduct of the study no deaths occurred and no test item-related changes in behaviour or external appearance were observed. The body weight of the male animals treated with 10 mg Cobalt dichloride hexahydrate/kg b.w./day and the body weight of the male and female animals treated with 30 mg Cobalt dichloride hexahydrate/kg b.w./day were slightly reduced. Body weight gain and body weight at autopsy changed accordingly.

 

No test-item related changes were observed during histopathological examination of the male and female reproductive organs. Histopathological examination performed on one testicle and one epididymis with special emphasis on the qualitative stages of spermatogenesis (proliferative, meiotic and spermiogenic phases) and histopathology of the interstitial testicular structure, did not reveal any test item-related effects. No test-item related influence on the ovaries, oviducts, uterus (incl. cervix) and vagina were noted. No test item-related difference was noted in the mean number of oestrous cycles for the female animals. No test item-related influence was noted on the serum levels of the hormones testosterone, progesterone, and 17 beta-estradiol in the male and female animals treated with 30 mg Cobalt dichloride/kg bw/day compared to the control group during study conduct, at the end of the treatment period, and at the end of the recovery period.

 

The No-Observed-Effect-level (NOEL) for fertility/reproductive effects was above 30 mg cobalt dichloride/kg bw/day by oral administration based on a complete absence of effects on reproductive organs, oestrus cycle, qualitative sperm staging and hormone levels.

 

 

In a combined repeated dose toxicity studies with the reproduction/developmental toxicity screening test (according to OECD 422 and under GLP) cobalt was administered orally to rats at dose levels of 30, 100, 300 and 1000 mg/kg bw/day during the pre-mating, mating and post-mating periods to parental males as well as during the pre-mating, mating, gestation and lactation periods until day 3 post-partum (or shortly thereafter) to parental female animals.

Piloerection, reduced motility, soft faeces/diarrhoea and reduced food consumption were noted - in relation to the dose - from a dose level of 100 mg cobalt /kg bw/day onwards. In addition, reductions of body weight were noted from 300 mg cobalt /kg bw/day onwards. Premature deaths occurred in five female rats at 100 mg cobalt /kg bw/day and eight female rats at 300 mg cobalt /kg bw/day. Treatment with 1000 mg cobalt /kg bw/day caused the premature death of nine of ten males and all ten females. Macroscopic inspection revealed changes of the gastro-intestinal tract - mainly in the prematurely deceased animals - from a dose level of 100 mg cobalt/kg bw/day onwards and adrenal changes and pulmonal lesions at 1000 mg cobalt/kg bw/day.

 

Histopathological inspection did not reveal any pathological changes. No histopathological correlate could be found for the macroscopical lesions noted at necropsy. No test item-related influence was noted on the sperm staging or interstitial cell structure (qualitative examination). Treatment with 300 mg cobalt/kg bw/day resulted in an increase of the post-implantation loss and a decrease in the live birth index. No test item-related influence was noted on mating behaviour, fertility and the gestation length. From 30 mg cobalt/kg bw/day onwards, the mean litter weight of pups was slightly reduced in a dose-related way (not significant at p ≤ 0.01), significant only at 300 mg cobalt/kg bw/day. In order to estimate a possible correlation between maternal toxicity and F1-Generation (pups) findings, the litter weight of pups was compared in dams with clinical signs within each group. Dams were classified based on the severity and occurrence of clinical signs. As a result it appeared that the earlier the clinical signs occurred in the dams a more pronounced weight reduction was noted for the pups of the respective dams. An increased F1-Generation (pups) mortality rate and a slightly decreased viability index were noted from 100 mg cobalt/kg bw/day onwards.

 

The NO(A)EL for effects on the F0-generation was 30 mg cobalt/kg bw/day, based on mortality, clinical signs of toxicity, effects on food consumption and macroscopic pathological changes observed at and above 100 mg cobalt/kg bw/day and reduced body weight at and above 300 mg cobalt/kg bw/day.

 

The NO(A)EL for effects on the reproductive toxicity was 30 mg cobalt/kg bw/day, based on an increased F1-Generation (pups) mortality rate and a slightly decreased viability index at 100 mg cobalt/kg bw/day and on post-implantation losses, decreases in the live birth index and significantly reduced litter weights of pups observed at 300 mg cobalt/kg bw/day.

 

In addition to the above studies there is a substantial number of information on the toxicity of soluble cobalt compounds to organs of male reproduction. These effects on male reproduction have been the reason to classify several cobalt substances for impairment of fertility in the EU. However, the available studies on fertility, summarized in IUCLID section 7.8.1, are all rated 3 (not reliable) or 4 (not assigned); the studies themselves do not show a clear dose-response relationship and beyond that suffer from either one or several of the following shortcomings:

 

                   Studies were not conducted according to guideline

                   The size of animal groups used in the published studies is smaller than stipulated within the guidelines and therefore, the statistical sensitivity of these studies is compromised.

                   only one dose level was given to animals instead of three dose levels as foreseen in the guideline

                   crucial parameter not reported, such as body weight, food/water consumption, clinical observations, full necropsy/histopathology

                   due to missing food/water consumption data, the actual ingested dose in drinking water/feeding studies could not be determined

 

Furthermore, none of the available studies represent state-of-the-art, guideline-compliant, extended one-generation reproduction toxicity studies or other relevant study designs, from which robust no-effect levels for human risk assessment could be derived. Moreover, the above-mentioned studies have a primary focus on effects in males, whereas there are no adequate data whatsoever to assess the effects on female reproduction.

 

Conclusion

 

The current test results (sub-acute and sub-chronic repeated dose toxicity study with cobalt and cobalt dichloride in male and female rats with additional examinations on fertility impairment) does not support the identification of any adverse effects towards male reproductive organs for the bioavailable cobalt substances group. However, these is still existing information in the public domain which identified a hazard with regard to male reproduction. Consequently all members of the bioavailable cobalt substances group will be self-classified as toxic for reproduction category 1B (H360F). The available data on the repeated dose toxicity of the bioavailable cobalt substances group is adequate to support a robust risk assessment, by using the point of departure for the most sensitive systemic effect on the haematopoietic system.

 

Effects on developmental toxicity

Effect on developmental toxicity: via oral route
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
Study duration:
subacute
Species:
rat
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

 

Cobalt dichloride is the source substance for the bioavailable cobalt substances group based on the read-across approach as outlined in Appendix 1.1 in the CSR. Two soluble inorganic cobalt substances, cobalt dichloride and cobalt powder, have been tested for developmental toxicity, resulting in an absence of effects on the developing organism up to the maximum tolerated dose.

 

In a pre-natal developmental toxicity study (according to OECD 414 and under GLP), cobalt dichloride was given to pregnant rats at doses of 0, 25, 50, 100 mg/kg bw/day. A total of 25 females per group were given the test items suspended in 0.5% hydroxypropyl methylcellulose gel orally via gavage once daily from gestation day 6 until gestation day 19.

 

No test item-related premature death was noted in the control or in any of the test item treated groups.

At 50 or 100 mg/kg bw/day piloerection, a slight to moderate reduced motility and slight to moderate salivation were noted for several dams on one or up to 6 test days.

At 100 mg/kg bw/day a haemorrhagic nose/snout was noted for 3 of 20 dams on gestation days 19 or 20. At 50 or 100 mg/kg bw/day statistically significantly reduced body weights in comparison to the control group were noted after the start of treatment (about 5 to 6% below the control group on gestation day 8 or 9). The reductions in body weight for both dose groups compared to the control group slightly increased during the further course of the study, leading to body weights on gestation day 20, that were 14.2% (intermediate dose group) or 15.1% (high dose group) below the value of the control group. The net weight change (body weight without gravid uterus) after the start of treatment until laparotomy (gestation day 6 to gestation day 20) was statistically significantly reduced for the dams treated with 50 or 100 mg/kg bw/day: control: + 38. 4 g, intermediate dose: -10.6 g, high dose: - 14.1g. Gastro-intestinal lesions in form of haemorrhagic foci in the stomach and intestines with a dark(-brown) content were noted in a dose related way for the dams dosed with 25, 50 or 100 mg/kg bw/day (low dose: 1 of 20 dams, intermediate dose: 3 of 20 dams, high dose: 9 of 20 dams). No test item related influence was noted on the gravid uterus weight. The carcass weights were statistically significantly reduced in comparison to the control group by 8.7, 18.2 and 18.1% for the dams treated with 25, 50 or 100 mg/kg bw/day.

 

The reproduction data of the dams revealed no test item-related differences for pre-implantation loss, post-implantation loss and resorptions/implantation site ratios between the dams of the control group and the dams treated with 25, 50 or 100 mg/kg bw/day.

 

No dead foetuses were noted in the litters of the dams of the control group and in the litters of the dams treated with 25, 50 or 100 mg/kg bw/day. No test item-related influence on the ratio of live male foetuses to live female foetuses were noted for all treatment groups. All values of the treatment groups were within the range of laboratory background data.

No test item-related differences of the placental or foetal weights were noted between the control group and the treatment groups.

 

No test item-related macroscopically visible malformations or variations were noted for the foetuses of the treatment groups during the external examination of the foetuses at laparotomy. The internal examination revealed no malformation or variations in the control or any of the treatment groups. Skeletal examination showed no test-item related malformations, variations or retardations in the control or any of the treatment groups. No test item-related malformations were noted during soft tissue examinations of the foetuses according to WILSON in any of the treatment groups. No test item-related differences for the incidences of the observed soft tissue variations were noted between the control group and the test item treated groups.

 

Under the test conditions of the pre-natal developmental toxicity study with cobalt dichloride, the no-observed-adverse-effect level (NOAEL) was 25 mg cobalt dichloride/kg bw/day for the dams, based on reduction of body weight and body weight gain, food consumption, changes of haematological parameters as well as gastro-intestinal lesions

 

The no-observed-adverse effect level (NOAEL) for the foetal organism was above 100 mg cobalt dichloride/kg bw/day. No test item-related changes were noted for the number of resorptions and the foetal body weight. No dead foetuses, no test item-related malformations, variations or retardations were noted at any of the tested dose levels.

 

In a prenatal developmental toxicity study, cobalt dichloride was administered orally to female rabbits at dose levels of 5, 13, 32 or 80 mg cobalt dichloride hexahydrate /kg bw/day from the 6th to 28th day of pregnancy. The 80mg/kg bw/daygroup was terminated prematurely due to the poor general condition of the animals, abortions and mortality.

Under the present test conditions, the no-observed-adverse-effect level (NOAEL) for systemic effects was 13 mg/kg bw/day for the dams based on significant decreases in body weight gain and food consumption at 32 mg/kg bw/day. There was increased mortality (19% loss of test animals) at this dose level. Low amounts of excreted faeces and/or diarrhoea were noted for the dams treated with 32 mg/kg bw/day. Histopathological changes were noted for the lungs and the liver at 32 mg/kg bw/day (necrosis and vacuolisation of hepatocytes). Furthermore, histopathological examination revealed test item-related local changes for the stomach mucosa (bleeding/congestions of gastric mucosa, isolated ulcerations and vacuolization of epithelial cells) and the large intestine mucosa (subepithelial lympho-histiocytic infiltration and vacuolization of epithelial cells) in all treatment groups (5, 13, 32 or 80 mg/kg bw/day) in a dose-related way. Based on the histopathological findings in the GI tract, the NOAEL for local effects in maternal animals is at 5 mg/kg bw/day, based on the onset of effects on the stomach mucosa (discoloration, red, white deposits, filled with liquid) at 13 mg/kg bw/day. No test item-related changes were noted during microscopic inspection of the sternal bone marrow of the control group and the low intermediate and high intermediate dose group (13 or 32 mg/kg bw/day).

The no-observed-adverse effect level (NOAEL) for the foetal organism was 5 mg/kg bw/day:

An increased number of resorptions was noted at 13 mg/kg bw/day, which was materno-toxic (local effects). At the materno-toxic (systemic effects) dose levels of 32 or 80 mg/kg bw/day an increased number of resorptions and/or abortions were noted. At 80 mg/kg bw/day, a decreased body weight was noted for the 5 available foetuses. No test item-related prematurely deceased foetuses, no malformations and no test item-related variations were noted. For the high intermediate dose group (32 mg/kg bw/day), an increase was noted for the incidence of unossified sternebrae (skeletal retardation) and the total number of skeletal retardations. However, as a reduced food consumption of the dams leads to a retarded ossification in the foetuses (Cappon et al., 2005), the increased incidences for unossified sternebrae and for the total number of skeletal retardations in the high intermediate dose group were considered to be secondary effects caused by the pronounced maternotoxicity. Under the conditions of the study, cobalt dichloride hexahydrate had no teratogenic potential.

In summary, the NOAELs determined in this study are as follows:

·        Maternal NOAEL (systemic) = 13 mg/kg bw/day, based on significant effects on body weight gain and food con-sumption and increased mortality at 32 mg/kg bw/day

·        Maternal NOAEL (local) = mg/kg bw/day, based on onset of GI irritation 13 mg/kg bw/day

·        Foetal NOAEL = 5 mg/kg bw/day, based on an increase in resorptions 13 mg/kg bw/day

 

 

In a combined repeated dose toxicity studies with the reproduction/developmental toxicity screening test (according to OECD 422 and under GLP) cobalt was administered orally to rats at dose levels of 30, 100, 300 and 1000 mg/kg bw/day during the pre-mating, mating and post-mating periods to parental males as well as during the pre-mating, mating, gestation and lactation periods until day 3 post-partum (or shortly thereafter) to parental female animals.

Piloerection, reduced motility, soft faeces/diarrhoea and reduced food consumption were noted - in relation to the dose - from a dose level of 100 mg cobalt /kg bw/day onwards. In addition, reductions of body weight were noted from 300 mg cobalt /kg bw/day onwards. Premature deaths occurred in five female rats at 100 mg cobalt /kg bw/day and eight female rats at 300 mg cobalt /kg bw/day. Treatment with 1000 mg cobalt /kg bw/day caused the premature death of nine of ten males and all ten females. Macroscopic inspection revealed changes of the gastro-intestinal tract - mainly in the prematurely deceased animals - from a dose level of 100 mg cobalt/kg bw/day onwards and adrenal changes and pulmonal lesions at 1000 mg cobalt/kg bw/day.

Histopathological inspection did not reveal any pathological changes. No histopathological correlate could be found for the macroscopical lesions noted at necropsy. No test item-related influence was noted on the sperm staging or interstitial cell structure (qualitative examination). Treatment with 300 mg cobalt/kg bw/day resulted in an increase of the post-implantation loss and a decrease in the live birth index. No test item-related influence was noted on mating behaviour, fertility and the gestation length. From 30 mg cobalt/kg bw/day onwards, the mean litter weight of pups was slightly reduced in a dose-related way (not significant at p ≤ 0.01), significant only at 300 mg cobalt/kg bw/day. In order to estimate a possible correlation between maternal toxicity and F1-Generation (pups) findings, the litter weight of pups was compared in dams with clinical signs within each group. Dams were classified based on the severity and occurrence of clinical signs. As a result it appeared that the earlier the clinical signs occurred in the dams a more pronounced weight reduction was noted for the pups of the respective dams. An increased F1-Generation (pups) mortality rate and a slightly decreased viability index were noted from 100 mg cobalt/kg bw/day onwards.

 

The NO(A)EL for effects on the F0-generation was 30 mg cobalt/kg bw/day, based on mortality, clinical signs of toxicity, effects on food consumption and macroscopic pathological changes observed at and above 100 mg cobalt/kg bw/day and reduced body weight at and above 300 mg cobalt/kg bw/day.

 

The NO(A)EL for effects on the reproductive toxicity was 30 mg cobalt/kg bw/day, based on an increased F1-Generation (pups) mortality rate and a slightly decreased viability index at 100 mg cobalt/kg bw/day and on post-implantation losses, decreases in the live birth index and significantly reduced litter weights of pups observed at 300 mg cobalt/kg bw/day.

 

 

In addition to the above studies there is a limited number of information on developmental toxicity of soluble cobalt compounds in several species, which suffers from several defects:

 

                   several studies (in particular those of Wide, 1984; Domingo et al., 1985) report effects on foetuses and neonates, but all studies suffer from several methodical and reporting deficiencies, thus rendering them of very limited use in a regulatory context. In addition, the reference by Gluhcheva et al. (2014) suffers from several methodological and reporting deficiencies, therefore was not relevant for human health risk assessment.

                   one study is apparently void of effects (Paternain et al., 1988) with regard to foetal effects, but maternal toxicity was observed at all dose levels, so that this study does not allow the derivation of a maternal no-effect level.

                   another study (Szakmary et al., 2001) provides a multitude of information, but which is partly contradictory in nature and also has reporting and methodological shortcomings.

 

In conclusion, these and other available studies show several deficiencies, thus rendering them of limited use in a regulatory context. Since the results are somewhat contradictory, they are considered unsuitable for a human health risk assessment and DNEL-setting under REACH.

Furthermore, none of the available studies represent state-of-the-art, guideline-compliant, extended one-generation reproduction toxicity studies or other relevant study designs, from which robust no-effect levels for human risk assessment could be derived.

 

 

Conclusion

 

Due to an absence of adverse effects for the soluble inorganic cobalt substances group in pre-natal developmental toxicity, no DNEL for reproductive toxicity will be derived.

 

The current test results (screening test with cobalt and pre-natal developmental toxicity study with cobalt dichloride in rats does not support the identification of any adverse effects towards developmental toxicity for the bioavailable cobalt substances group.

 

Justification for classification or non-classification

Based on the existing published data on fertility impairment of some members of the bioavailable cobalt substances group all members of the bioavailable cobalt substances group (with the exception of cobalt metal) will be self-classified as toxic for reproduction category 1B (H360F). This is supported by the findings in the pre-natal developmental toxicity study showing a decreased ability of the dams to maintain pregnancy.

Due to an ongoing legal process of a harmonised classification for cobalt metal, the self-classification as toxic to reproduction category 2 (H361f) will remain unaltered until the legal classification will become binding.