Naphthenic acids, nickel salts

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

No genetic toxicity study with naphthenic acids, nickel salts is available, thus the genetic toxicity will be addressed with existing data on the assessment entities nickel and naphthenate.

Naphthenic acids, nickel salts is expected to be genotoxic, since the moiety nickel has shown positive results in in vitro and in vivo studies:

For water soluble nickel compounds like nickel sulphate, there is evidence indicating that they are weak genotoxicants in vitro and may exhibit clastogenic activity. Some in vivo studies with nickel sulphate have been positive while two recent micronucleus studies via oral and intraperitoneal injection were negative. Evidence from human studies is limited. There are no definitive studies on germ cells, and little evidence concerning hereditable effects. Nickel sulphate and other water-soluble nickel compounds carry a harmonized Muta. 2: H341 CLP classification.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (positive)

Genetic toxicity in vivo

Description of key information

No genetic toxicity study with naphthenic acids, nickel salts is available, thus the genetic toxicity will be addressed with existing data on the individual moieties nickel and naphthenate.

Naphthenic acids, nickel salts is expected to be genotoxic, since the moiety nickel has shown positive results in in vitro and in vivo studies:

For water soluble nickel compounds like nickel sulphate, there is evidence indicating that they are weak genotoxicants in vitro and may exhibit clastogenic activity. Some in vivo studies with nickel sulphate have been positive while two recent micronucleus studies via oral and intraperitoneal injection were negative. Evidence from human studies is limited. There are no definitive studies on germ cells, and little evidence concerning hereditable effects. Nickel sulphate and other water-soluble nickel compounds carry a harmonized Muta. 2: H341 CLP classification.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (positive)

Additional information

Nickel

The in vivo studies with nickel sulphate have produced mixed results. Two studies (a K1 and a K2) looking at micronucleus in bone marrow of rats (oral) and mice (intraperitoneal) exposed repeatedly to nickel sulphate were negative (Oller and Erexson, 2007; Morita et al., 1997); two K3 studies looking at the oral induction of micronucleus in mice indicated positive results (Sharma et al., 1987; Sobti and Gill, 1989). A study by Benson et al. (2002) showed that nickel sulphate given by inhalation seemed to induce genotoxicity (DNA damage) in lung cells at the same or higher concentrations at which it induces inflammation after repeated exposures. Evidence from human studies is limited. There are no definitive tests of nickel compounds on the germ cells but evidence for a possible effect is limited. Whilst there is evidence that the nickel ion reaches the testes, no effect on spermatogonial cells was seen in the Mathur et al. (1978) study with nickel sulphate. The effects seen in spermatozoa in the Sobti & Gill (1989) study with several water soluble Ni compounds may reflect toxic effects on germ cells rather than chromosomal damage. In addition, a dominant lethal test (Deknudt & Léonard, 1982) with water soluble Ni compounds, was negative and these results are relevant for nickel sulphate. Whilst some effects are seen in males (e.g. sperm abnormalities) there is little evidence for inheritable effects on the germ cells.

In April 2004, the Specialised Experts concluded that nickel sulphate, nickel chloride and nickel nitrate should be classified as Muta. Cat. 3; R68 (now Muta. 2: H341 under CLP classification). This conclusion was based on evidence of in vivo genotoxicity in somatic cells, after systemic exposure (the 2007 negative oral MN study was not available at that time). Hence the possibility that the germ cells are affected could not be excluded (European Commission, 2004). The mutagenicity of nickel acetate was not evaluated by the Specialised Experts, but nickel acetate was later classified as Muta. 2: H341 by reading across from Ni sulphate.

The following information is taken into account for any hazard / risk assessment:

For water soluble nickel compounds like nickel sulphate, there is evidence indicating that they are weak genotoxicants in vitro, and may exhibit clastogenic activity. Some in vivo studies with nickel sulphate have been positive while two recent micronucleus studies via oral and intraperitoneal injection were negative. Evidence from human studies is limited. There are no definitive studies on germ cells, and little evidence concerning hereditable effects. Nickel sulphate and other water soluble nickel compounds carry a harmonized Muta. 2: H341 CLP classification. Recently, there has been some recognition that nickel compounds may be indirect genotoxic carcinogens with a practical threshold (see discussion of SCOEL 2011 report in Appendix C2).

 

Naphthenate

No experimental in vitro genetic toxicity studies were available for Naphthenic acids, however Weight of Evidence was available from ‘Sodium naphthenates’:

- Salmonella bacterial mutagenicity: negative up to >333 μg/L with and without metabolic activation (NTP, 1993; HPVIS, 2012).

- Chromosomal aberration: negative in CHO cells at 54, 116 & 250 μg/mL without metabolic activation and 25, 54, 116 & 250 μg/mL with metabolic activation (NTP, 1993; HPVIS, 2012).

- Sister Chromatid Exchange: weakly positive to positive when tested at concentrations of 17, 59, 167, 500 ug/mL (Trial 1; without metabolic activation) and 100, 150, 200, 250 µg/mL (Trial 2; without metabolic activation) and negative at 17, 59, 167, 500 µg/mL with metabolic activation (NTP, 1993; HPVIS, 2012). Although a positive result is obtained in 2 separate runs without metabolic activation, the validity of these results is questionable since the occurrence of cytotoxicity is not well documented.

 

Further Weight of Evidence is available from ‘Calcium naphthenates’:

- E-coli and Salmonella bacterial reverse mutagenicity: negative in WP2 uvr A and Salmonella TA 1535, TA 1537, TA 98 and TA 100 strains when tested at 31.25 - 4000 μg/plate with and without metabolic activation (Shell Research Ltd, 1983).

- Saccharomyces cerevisiae: non-mutagenic when tested at 10 -5000 μg/plate with and without metabolic activation (Shell Research Ltd, 1983).

- Rat Liver chromosomal damage: non-mutagenic at 62.5-250 μg/mL without metabolic activation (Shell Research Ltd, 1983).

- In vitro testing in L5178Y T K +/-mouse lymphoma cells both with and without metabolic activation at 0.0005 to 10000 µg/mL showed a positive effect in the absence of metabolic activation (Seifried et al, 2006), however when studying the raw data and the evaluation criteria the applicant can not support this conclusion.

 

Additional Weight of Evidence is available from QSAR prediction on the various molecules (C6 -C30 chain lengths):

- VEGA QSAR model which is an extension of the original CAESAR model (Ferrari & Gini, 2010; Benigni et al;, 2008): consistently non-mutagenic.

- Toxtree: Benigni-Bossa rulebase for mutagenicity (Benigni et al., 2008; Benigni et al., 2007): consistently non-mutagenic.

 

Finally, an in vivo Micronucleus test was conducted in male and female Wistar rats with refined Naphthenic acids dosed at 100, 300 and 900 mg/kg bw by oral gavage (HPVIS, 2010). A total of 1000 erythrocytes/slide were evaluated (both polychromatic PCE and normochromatic erythrocytes NCE), and the PCE/NCE ratio was calculated. The number of micronucleated PCEs from a total of 2000 PCEs was then determined for each animal. The frequencies of micronuclei in in bone marrow did not differ statistically from those in the sham and vehicle control groups. A significant increase in micronucleus frequency was found in material harvested from rats treated with the positive control, cyclophosphamide providing evidence that the test had worked as expected.

Naphthenic acids, nickel salts

Naphthenic acids, nickel salts is expected to be genotoxic, since the moiety nickel has shown positive results in in vitro and in vivo studies:

For water soluble nickel compounds like nickel sulphate, there is evidence indicating that they are weak genotoxicants in vitro and may exhibit clastogenic activity. Some in vivo studies with nickel sulphate have been positive while two recent micronucleus studies via oral and intraperitoneal injection were negative. Evidence from human studies is limited. There are no definitive studies on germ cells, and little evidence concerning hereditable effects. Nickel sulphate and other water-soluble nickel compounds carry a harmonized Muta. 2: H341 CLP classification. Thus, naphthenic acids, copper salts is classified according to regulation (EC) 1272/2008 as genetic toxicant Muta. Cat. 2 (H341).

For further information on the toxicity of the individual moieties, please refer to the relevant sections in the IUCLID and CSR.

Justification for classification or non-classification

Naphthenic acids, nickel salts is expected to be genotoxic, since the moiety nickel has shown positive results in in vitro and in vivo studies. Thus, naphthenic acids, copper salts is classified according to regulation (EC) 1272/2008 as germ cell mutagen cat. 2 (H341).