Reaction mass of copper oxide and manganese dioxide

Endpoint summary

Description of key information

No data are available for the registration substance. However adequate and reliable studies performed with each of the two constituents of the registration substance are at hand.

The studies leading to the most robust data are:

a) In a 13-week repeated dose toxicity study male and female Fisher F334/N rats received 0, 500, 1000, 2000, 4000, and 8000 ppm of cupric sulfate pentahydrate (CASRN 7758-99-8) via feed. Based on histopathological changes in forestomach, liver and kidney and changes in clinical chemistry and urine analysis, the NOAEL of this study was determined to be 1000 ppm (mg/kg diet) corresponding to 16.3/17.3 mg copper/kg bw/day in male/female rats and 90.7 mg registration substance/kg bw/day.

b) In a cross sectional study, which investigated an occupational cohort of male workers from a dry alkaline battery exposed to MnO2 dust and their unexposed age-and area-matched controls, statistically significant differences in results of neurobehavioral tests, particularly in simple reaction time, eye-hand coordination, and hand steadiness, were noted. The reference value derived based on the most critical endpoint was the BMCL10 estimate from the logistic model of 142 μg Mn/m3, which corresponds to 320 μg registration substance/m³.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

supporting study

Justification for type of information:

For details on endpoint specific justification please see read-across report in section 13 or find a link in cross-reference “assessment report”.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Dose descriptor:

NOAEL

Effect level:

3.2 mg/kg bw/day (nominal)

Based on:

test mat.

Remarks:

calculated to copper from copper monochloride

Sex:

male

Basis for effect level:

gross pathology

Dose descriptor:

NOAEL

Effect level:

17.8 mg/kg bw/day (nominal)

Based on:

test mat.

Remarks:

calculated to registration substance

Sex:

male

Basis for effect level:

histopathology: non-neoplastic

Remarks on result:

other: value calculated based on ratio of MnO2 and CuO in the reaction mass

Dose descriptor:

NOAEL

Effect level:

1.3 mg/kg bw/day (actual dose received)

Based on:

test mat.

Remarks:

calculated to copper from copper monochloride

Sex:

female

Basis for effect level:

histopathology: non-neoplastic

Dose descriptor:

NOAEL

Effect level:

4.64 mg/kg bw/day (nominal)

Based on:

test mat.

Remarks:

calculated to registration substance

Sex:

female

Basis for effect level:

histopathology: non-neoplastic

Remarks on result:

other: value calculated based on ratio of MnO2 and CuO in the reaction mass

Conclusions:

A combined repeated dose and reproductive/developmental toxicity study (OECD TG 422) with copper monochloride was performed with rats. Sprague-Dawley rats received 0, 1.3, 5, 20 or 80 mg/kg bw/day via oral gavage. The most critical effects in parental animals was the increase in squamous cell hyperplasia of the stomach. Based on these findings, the NOAELs were concluded to be 5 mg/kg bw/day in male rats (corresponding to 3.2 mg copper/kg bw/day and 17.8 mg registration substance/kg bw/day) and 1.3 mg/kg bw/ day (corresponding to 0.83 mg copper/kg bw/day and 4.64 mg registration substance/kg bw/day; low dose group) in female rats.

Executive summary:

The study used as source investigated copper monochloride.

The study results of the source compound were considered applicable to the target compound. Justification and applicability of the read-across approach (structural analogue) is outlined in the read-across report in section 13 or find a link in cross reference “assessment report”.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

90.7 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

quality of the whole database good, study used here for DNEL derivation is used in various assessments of copper compounds as key study

System:

other: Histopathological changes in forestomach, liver and kidney. Changes in clinical chemistry and urine analysis.

Organ:

kidney

liver

stomach

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

BMCL10

320 µg/m³

Study duration:

chronic

Species:

other: humans (epidemiological study results reported in IUCLID section 7.10.2)

Quality of whole database:

quality of the whole database good, study used here for DNEL derivation is used in various assessments of manganese dioxide mediated toxicity as key study (Roels et al., 1992)

System:

other: neurobehavioural effects

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

Mode of Action Analysis / Human Relevance Framework

Summary of manganese induced neurotoxicity (leading to classification) as provided by the German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation; Hartwig, A, 2011, 50. Lfg)

"Damage to dopaminergic neurons in the brain stem and basal ganglia, produced by selective accumulation of manganese in specific regions of the brain stem and the basal ganglia ( striatum , pallidum and substantia nigra), is regarded to be the most important physiological endpoint of manganese toxicity. The mechanisms of the neurotoxicity of manganese are very complex, and different mechanisms of action were found which converge in damaging dopaminergic neurons. In the dopaminergic system, manganese inhibits the reverse transport of dopamine to the cells and synapses as well as dopamine release. At the cellular level, the mitochondria are the most sensitive target. Here, oxidative phosphorylation and ATP synthesis - and thus energy supply to the cells - are inhibited. The induction of reactive oxygen species (ROS) and nitrogen monoxide (NO) is considered to be the molecular mechanism. ROS can be released when electrons are transferred directly to oxygen in the respiratory chain disturbed by manganese or when manganese releases iron ions from protein complexes, which catalyze the formation of ROS. NO is also considered to be a cause of manganese neurotoxicity; this is because manganese induced the inducible NO synthase (iNOS) both in vivo and in vitro. However, a number of data also exist which question oxidative stress as a mediator of manganese toxicity. On the other hand, manganese also interacts with the aggregation and fibrillation properties of alpha-synuclein, the most important protein in the pathogenesis of Parkinson’s disease."

Additional information

Copper:

As key study the subchronic toxicity study with rats by Hébert et al., 1993 was used. Within this toxicity study similar to a guideline study (OECD TG 408) male and female F344/ N rats were dosed with cupric sulfate pentahydrate via feed at concentrations of 0, 500, 1000, 2000, 4000, and 8000 ppm (mg/ kg diet).

This corresponds to 0, 8.1/8.7, 16.3/17.3, 32.8/34.4, 65.9/68.0 and 140.2/134.4 mg copper/kw bw /day in male/female rats (recalcuation was taken from the voluntary risk assessment report).

Animals were evaluated for histopathology, clinical pathology, reproductive toxicity, and tissue metal accumulation, and target organs were examined by a variety of special stains and by electron microscopy to characterize the observed lesions.Cupric sulfate concentrations of 4000 ppm and higher caused significant reductions in body weight gain. Hyperplasia and hyperkeratosis of the limiting ridge of the forestomach were present (starting at concentration of 2000 ppm). A dose-related increase in inflammation in the liver and changes in clinical chemistry parameters which were indicative of hepatocellular damage and cholestasis were seen. Histologic changes in the kidneys of rats consisted of a dose-related increase in the number and size of eosinophilic protein droplets in the epithelial cytoplasm and the lumina of the proximal convoluted tubules. Droplets were larger and more numerous in males than in females. Urinalysis results were suggestive of renal tubular epithelial damage. The present study confirms the liver and kidney toxicity of cupric sulfate in rats and extends these results to describe the occurrence of forestomach lesions in rats. In addition, iron staining of spleens from treated animals indicated a marked depletion of iron stores in both male and female rats, while hematologic and clinical chemistry alterations were indicative of a microcytic anemia. Cupric sulfate produced no adverse effects on any of the reproductive parameters measured in rats of either sex. The NOAEL identified in this study thus is determined to be 1000 ppm (mg cupric sulfate pentahydrate/kg diet), which corresponds to 90.7 mg registration substance/kg bw/day (value calculated based on ratio of MnO2 and CuO in the reaction mass).

The results of a combined repeated dose and reproductive/developmental toxicity study (OECD TG 422) with copper monochloride performed with rats can be used as supporting study. Sprague-Dawley rats received 0, 1.3, 5, 20 or 80 mg/kg bw/day via oral gavage. The most critical effects in parental animals was the increase in squamous cell hyperplasia of the stomach. Based on these findings, the NOAELs were concluded to be 5 mg/kg bw/day in male rats (corresponding to 3.2 mg copper/kg bw/day and 17.8 mg registration substance/kg bw/day) and 1.3 mg/kg bw/ day (corresponding to 0.83 mg copper/kg bw/day and 4.64 mg registration substance/kg bw/day; low dose group) in female rats.

A guideline limit value for the respirable fraction of 10 µg Cu/m³ was identified by different stakeholders (Hartwig, 2014, 57. Lfg.; SCOEL, 2014(SCOEL/SUM/171) and was based on a weight of evidence approach. The respective studies are shortly introduced here, but not reported in full detail in this IUCLID:

- Gleason, 1968: flu-like effect at exposure concentration of 0.12 to 0.36 mg Cu/m³; effects observed in occupationally exposed workers disappeared when the copper exposure was lowered to 0.008 mg Cu/m³

- Drummond, 1986: decreased activity of immune system after 5 or 10 day inhalation exposure (3h/day) to 0.12 or o.13 mg Cu/m³ (applied as CuSO4)

- ICA, 2010: subacute inhalation toxicity study (OECD TG 412) - rats were exposed to copper (I) oxide (Cu2O, concentration of 0, 0.2, 0.4, 0.8 and 2.0 mg/m3, 6h/day, 5 days/week)

--> local effects - inflammation in lower respiratory tract – only exposure to respirable fraction already at lowest test concnetration --> LOAEC = 0.2 mg Cu2O/m³ = 0.17 mg Cu/m³ --> leading to a human equivalent concentration of NAEC = 0.012 mg Cu/m³ (this is a no effect concnetration as basis was only 1/3 of the study LOAEC).

Overall - identification of the same target organ (lung) and obvious effects in the same concentration range (0.12–0.36 mg Cu/m3).

NOTE: While the stakeholders derived limit values for the respirable fraction they concluded that no reliable studies are available allowing for deduction of a limit value for the inhalable fraction.

Manganese:

ORAL:

As supporting evidence a study, in which male and female Wistar rats were treated orally with MnO2 daily for 28 days can be used. No mortality was observed, yet at the highest dose level toxic effects occured

and therefore a NOAEL of 300 mg MnO2 /kg bw/d corresponding to be 429 mg/kg bw/d for Hopcalite, was deteremined.

INHALATION:

The most relevant and reliable study for manganese dioxide was provided as key study (Roels et al., 1992).

In this cross sectional study a occupational cohort involving 92 male workers in a dry alkaline battery plant (exposure to dust containing MnO2) and the 101 age-and area-matched controls (with no industrial

exposure to manganese) were investigated for performance on a battery of neurobehavioral tests as well as for some biological parameters. The selection of study participants as well as the matching of

controls was reasonable and both populations were well matched for age, height, weight, work schedule, coffee and alcohol consumption and smoking.

Exposure assessment was done by personal sampling and the average (geometric mean) exposure duration was 5.3 years (range: 0.2–17.7 years) and the average exposure concentration was 215 μg

manganese/m³ of respirable dust and of 948 μg manganese/m³ for toal dust.

Manganese-exposed workers performed significantly worse than the controls on the neurobehavioral tests, with particular differences in simple reaction time, eye-hand coordination, and hand steadiness.

Additional data not published (individual exposure levels and whether the individual had an abnormal performance in the neurobehavioral tests (scores below the 5th percentile score of the control group)) was provided by the study authors Dr. Harry Roels to a US agency (ATSDR - Agency for Toxic Substances and Disease Registry), which then calculated a benchmark dose based on the most

sensitive endpoint among the end points showing statistically significantly elevated incidences of abnormal scores, i.e. percent precision score in the eye-hand coordination test.

Average exposure concentration for each worker was calculated by dividing the individual lifetime integrated respirable concentration (LIRD; calculated by Dr. Roels from occupational histories and measurements of workplace air manganese concentrations) by the individual’s total number of years working in the factory. Individuals were grouped into six exposed groups and the control group, and the

average of the range in each group was used in benchmark dose (BMD) modeling of the incidence data for number of workers with abnormal percent precision eye-hand coordination scores.

The agency identified the BMCL10estimates from the logistic model as the best fitting model by the AIC measure and the respective BMCL10 is 142 μg Mn/m3, which corresponds to 320 µg registration substance/m³.

There is a variety of studies available investiagting effects in cross sectional studies, follow-up studies or other epidemilogical studies and which are assessed in various risk assessments performed by expert groups and committees like the German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) (MAK) or the European Scientific Committee on Occupational Exposure Limits (SCOEL).

The most sensitive endpoint identified for deriving workplace threshold concentrations for manganese is the occurrence of preclinical neurotoxic effects after inhalation.

In summary, in the majority of the studies relevant for an assessment, the NOAEC is at or above 0.2 mg Mn/m³ (inhalable fraction), which corresponds to 450 µg hopcalite/m³.

Justification for classification or non-classification

Based on the results obtained in epidemiological studies (especially Roels et al., 1992) with exposure to manganese dioxide, one of the main constituents of the registration substance, this constituent is classified with respect to specific target organ toxicity following repeated inhalation exposure (STOT RE 2, hazard phrase H373) accoding to the criterias set in Regulation (EC) No 1272/2008 section 3.9.2.6. In turn the registration substance is classified as specific target organ toxicity following repeated inhalation exposure (STOT RE 2, hazard phrase H373), as well, based on the generic concentration limits which trigger classification of a mixture as provided in table 3.9.4 of the same regulation.