Registration Dossier

Administrative data

Description of key information

Oral
90d rat: NOAEL >= 450 mg/kg bw/day; no bioavailability (OECD 408, Bomhard et al. 1982)
46d (males)/ 41-45d (females) rat: NOAEL >= 1000 mg/kg bw/day (OECD 422, MHLW 2002)
Inhalation
5 d rat: NOAEL >= 0.06 mg/L; clearance in the lung, no bioavailability (BASF 1994)
Because of the nickel titanate impurity in C.I. Pigment Green 50, surrogate data from other nickel species for the inhalation route are used to fully assess the endpoint. Inhalation exposure related toxicities were noted following 13 weeks or two years of exposure to NiO (Dunnick et al. 1989, NTP, 1996) in both rats and mice. Adverse effects in rodents were primarily limited to the lung (e. g., increased tissue weight, inflammation, macrophage hyperplasia) The LOAEC from the corresponding chronic study was 0.6 mg NiO/m3 or 0.5 mg Ni/m3.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
1 000 mg/kg bw/day
Study duration:
subacute
Species:
rat
Quality of whole database:
Peer reviewed data base (peer review was conducted by a Japanese toxicological expert group at March 5, 2001)

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Study duration:
subacute
Species:
rat
Quality of whole database:
Well documented study report.

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

Additional information

Data for C.I. Pigment Green 50 (spinel pigment based on cobalt (II)/nickel (III)/zinc titanate) are not available. Thus read across was performed with C.I. Pigment Yellow 53 (nickel antimony titanium yellow). The two Nickel-containing pigments belong to a family of spinel and rutile pigments that have been tested for ion leaching (please refer to IUCLID section 7.9.3) and have been exempted from classification based on non-availability of ion toxicophores. The heavy metal oxides (used for Pigment manufacturing) are absorbed by the spinel resp. rutile lattice and thus lose their chemical, physical, and physiological properties. Both pigments show a very low water solubility (< 0.05 mg/L) being practically physiologically inert. Thus, it can be concluded, that the chemical behaviour towards the different toxicological endpoints is similar for both pigments. Therefore all toxicological endpoints were addressed with C.I. Pigment Yellow 53. No data was available for repeated dose inhalation. Because both pigments contain nickel titanate as impurity, surrogate data from other nickel species were used to cover this endpoint. Bridging to nickel oxide was performed to cover the worst case for repeated dose inhalation. Due to the inert character the exposure towards fine dust is the most relevant health concern for pigments.

Oral repeated exposure

Key studies

In a GLP compliant study performed according to OECD guideline 422, groups of male and female CD rats (12/sex) were administered orally with C.I. Pigment Yellow 53 at concentrations of 250, 500 or 1000 mg/kg bw/day for 46 d (males) or 41-45 d (females) (MHLW 2002). No abnormal findings were observed at a dose of 250 mg/kg bw/d. In the 500 and 1000 mg/kg bw/d groups, all of the males and females showed yellow or yellowish brown feces throughout the administration period. Gross pathological examination of these groups revealed yellowish green discoloring of the contents in the cecum in some of the animals. However, it was considered that the contents in the digestive organs were colored yellow with oral administration of a large amount of C.I. Pigment Yellow 53, and that these changes did not indicate biological adversity. There were no treatment related adverse effects on body or organ weights, food consumption, findings of urinalysis, hematological and blood chemical examinations, and histopathological examination in any animal in these groups. The NOAEL is considered to be 1000 mg/kg bw/day or more for males and females.

In a subchronic study performed similar to OECD guideline 408, groups of male and female Wistar rats (15/sex) were treated with C.I. Pigment Yellow 53 at concentrations of 0.5, 5, 50 and 500 mg/kg bw/day for 90 d (Bomhard et al. 1982). No substance related effects on mortality, clinical signs, body weight, haematology, clinical chemistry, organ weights, gross pathology and histopathology were observed. There were no indications for bioavailability.

Inhalation repeated exposure

Key study

In a GLP compliant bioavailability study, male Wistar rats were exposed for 5 d to 60 mg/m3 of C.I. Pigment Yellow 53; the observation period was 0, 3, 10, 31 and 60 d (BASF, 1994). No effects on mortality, clinical signs, body weights and body weight gains were found. Clearance half time was ca. 50 d in the lung; no systemic bioavailability was found in other organs. However, because C.I. Pigment Green 50 contains nickel titanate as an impurity, for which no inhalation data were available, surrogate data from other nickel species were used to fully assess this endpoint.

Supporting publications

Data for repeated-dose toxicity via inhalation exposure to nickel oxide described below. The inhalation studies ranged in exposure duration from 12 days to lifetime exposures, including 1, 3, 4, 6, 12, 13 and 24 and more month durations of nickel oxide inhalation. Several studies evaluated toxicity at the end of exposure, and some also included evaluation of toxicity one to three months following the cessation of exposure. Both green and black nickel oxides were evaluated, though most studies focused on a single dose of green nickel oxide. Toxicity was evaluated in rats, mice and hamsters. Endpoints generally included evaluation of body and organ weight changes, assessment of tissue damage (primarily in lung), mortality and gross toxicity, and alterations in serum or broncho-alveolar lavage fluid (BALF) chemistry.

The most robust data characterizing toxicity following repeated doses of nickel oxide was reported in a series of publications by Dunnick and colleagues (1988, 1989, 1995; Benson et al. 1989). These studies were associated with a comprehensive bioassay conducted by the National Toxicology Program (NTP) that compared the toxicity of nickel sulfate, Ni3S2 and NiO (NTP, 1996). Toxicity evaluations were conducted following 16 days, 3 months, and two years (exposure on weekdays only) of exposure to green NiO (0, 1.2, 2.5, 5.0, 10, or 30 mg NiO/m3) in F344/N rats and B6C3F1 mice. Endpoints examined included clinical signs of toxicity, body and organ weights, histopathology, and measurement of the concentration of nickel in lung tissue. Following 12-day and 3-month exposures, adverse effects in rodents were primarily limited to the lung (e. g. increased tissue weight, inflammation, macrophage hyperplasia); effects were noted to occur in a dose dependent fashion, and were generally more severe in rats than mice. Following two years of exposure, effects included dose-dependent occurrence of alveolar and bronchiolar hyperplasia, inflammation, fibrosis, lymphoid hyperplasia of the lung-associated lymph nodes, and increases in lung weight. No increased mortality was observed due to NiO exposure of any duration. Relative to the other nickel compounds evaluated, NiO was the least toxic, though it resulted in the highest lung burden of nickel. As such, the authors generally concluded that toxicity to the lung correlated with solubility of the nickel compound rather than the amount of nickel in the lung. The LOAEC for respiratory effects in the chronic study was 0.6 mg/m3.

In a series of studies associated with, but not specifically included in the comprehensive NTP bioassay, Benson et al (1989) evaluated biochemical and cytological changes in BALF in rats and mice following 13 weeks or 6 months of exposure to green NiO (0, 0.6, 2.5 or 10 mg/m3). Generally, dose-dependent changes were observed for the majority of endpoints evaluated, including changes in total protein, lactate dehydrogenase, total nucleated cells, the percent of neutrophils and macrophages, macrophage proliferation, interstitial pneumonia and chronic inflammation. The severity and incidence of histopathological findings were evaluated over time in the 6-month exposure study (Benson et al., 1995); effects were generally most severe two months following the initiation of exposure, remained steady until the cessation of exposure. However, the incidence of lesions continued to increase in mice for two months after the termination of exposure, whereas the incidence (but not severity) decreased during the 4-month recovery phase. Based on the findings that changes in biochemical indicators of lung lesions measured in BALF paralleled the nature and incidence of morphological changes (as reported by Dunnick and colleagues), the authors concluded that inhalation of occupationally relevant aerosol concentrations of green NiO can produce toxic effects in the lungs of rodents.

Chronic exposure to multiple doses of nickel oxide was also investigated by a number of other groups. Weischer and colleagues (1980a, 1980b) evaluated clinical and clinico-chemical parameters in blood, serum and urine, along with body and organ weight changes and tissue damage associated with exposure to NiO aerosols (three doses) for 21-, 28-, or 120-days in female and male rats. Gender differences were observed in the severity of changes for a number of clinical chemistry endpoints, though data generally suggested that toxicities occurred in a dose-dependent fashion with some exceptions (e. g., organ weight changes). The authors concluded that subchronic NiO inhalation induced lesions in lungs, liver and kidneys in rats.

Though most studies characterizing repeated inhalation toxicity associated with nickel oxide did not report increased mortality, Takenaka et al. (1985) observed dose-dependent, significant decreases in mean survival times following exposure to 60 μg/m3 or 200 μg/m3 in rats. Exposure-dependent decreases in body weight, increased lung weight, and histopathological signs of toxicity were also reported. Following a similar duration of exposure, Tanaka et al. (1988) did not see an exposure related effect on body weight gain or mortality following inhalation of NiO (200 μg/m3 or 1200 μg/m3) in rats, though significant increases in lung weight and pulmonary lesions were clearly associated with exposure. These authors also evaluated animals 8 months following the cessation of a 12-month exposure and did not note any significant toxicities following long-term exposure. Cho et al. (1992) also evaluated toxicity in rats immediately following a 12-month inhalation exposure, and 8 months following cessation of the exposure. Similarly, the authors reported increased lung tissue weight; these authors also reported that NiO exposure resulted in a significant increase in lung lipid concentration following chronic exposure.

Several studies also evaluated the toxicity of repeated inhalation exposure to a single concentration of nickel oxide. Murthy et al. (1983) exposed rats to NiO (120 μg/m3) for 12 days, collected BALF, and documented a number of cellular toxicities in macrophages using transmission electron microscopy. Fujita et al. (2009) also evaluated toxicity, as well and changes in gene expression, following repeated exposure to a single dose of ultrafine NiO (200 μg/m3) for one month in rats. The authors did not report a significant change in lung weight; however, changes in gene expression in lung tissue were evaluated 3 and 33 days post exposure that were collectively suggestive of acute inflammation and also suggested that damaged tissues undergo repair in the post-exposure period. In a study evaluating the potential co-carcinogenicity of inhaled NiO and cigarette smoke, Wehner et al (1975) exposed hamsters over a lifetime (53.2 μg NiO/L) and reported that NiO exposure did not appear to effect survival. The authors concluded that while the hamsters eventually developed increasingly severe pneumoconiosis in response to the chronic NiO exposures (53.2 μg/L), they did not find a significant carcinogenic effect of the inhaled NiO or a co-carcinogenic effect of cigarette smoke.

Collectively, the available studies demonstrate that repeated inhalation of nickel oxide in laboratory species results in dose-dependent, adverse toxicological responses, primarily in the lung. These responses include, but are not limited to, increased tissue weight and a variety of cellular lesions associated with inflammation and hyperplasia (typically observed in macrophages). Repeated inhalation exposure to nickel oxide typically did not significantly influence mortality rates, body weight changes, nor was it associated with significant adverse effects in tissues other than the lung. Given the robust nature of the available studies, the data were sufficient to characterize toxicity following repeated inhalation exposure; however, data were insufficient to characterize repeated dose toxicity from all other routes.

Conclusions

The study data on oral exposure with the read across substance Pigment Yellow 53 proves the inert character of pigments as no treatment related effects were observed in both the subacute and subchronic study. When inhaled the read across pigment did not show any treatment related effects regarding overall clinical signs and mortality as well. The studies on oral and inhalation exposure confirmed the results from the in vitro leaching studies that organ translocation of ions from the crystal lattice could not be demonstrated. But as Pigment Green 50 contains nickel titanate as impurity, the above findings with the read across substance NiO cannot be disregarded with regard to inhalation findings.


Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Peer reviewed data base (peer review was conducted by a Japanese toxicological expert group at March 5, 2001)

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
Well documented study report.

Justification for classification or non-classification

Dangerous Substance Directive (67/548/EEC)

The available studies are considered reliable and suitable for classification purposes under 67/548/EEC. As a result the substance is notconsidered to be classified for repeated dose toxicity under Directive 67/548/EEC.

Classification, Labeling, and Packaging Regulation (EC) No. 1272/2008

The available experimental test data are reliable and suitable for classification purposes under Regulation 1272/2008. As a result the substance is not considered to be classified for repeated dose toxicity under Regulation (EC) No. 1272/2008.