Naphthenic acids, bismuth salts

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

In conclusion, it can be stated that neither bismuth ions nor naphthenic acid ions had negative effects on mating and reproductive organs or sperm parameters/oestrus cyclicity. Thus, naphthenic acids, bismuth salts, the target substance, is not considered to negatively affect fertility.

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The substance naphthenic acids, bismuth salts is manufactured from bismuth oxide/hydroxide and 3 equivalents of naphthenic acids, resulting in the bismuth tri-naphthenate. Thus, to assess reproductive toxicity, results for bismuth 3+ cations were assessed as well as data for naphthenic acids, the two potential hydrolysis products of the substance. The undissociated substance is considered uncritical, as its molecular mass of ~850 Dalton makes it unlikely that such compounds efficiently pass biological membranes. Thus, the reproductive toxicity on naphthenic acids, bismuth salts will be dominated by its ions, derived from hydrolysis.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The source compound naphthenic acids is the starting material for the manufacturing of naphthenic acids, bismuth salts. Naphthenic acids do contain mainly hydrocarbon acids with a carbon range from 10 - 15 (other naphthenic acids may have wider ranges), with a variable number of cyclics contained (n = 0, 1, 2 and rarely 3). To a minor extent also aliphatics may be present as minor "impurities".
The naphthenic acids are reacted in a slight excess of >3 equivalents of naphthenic acids with bismuth oxide to derive naphthenic acids, bismuth salts, the target substance, containing bismuth tri-naphthenate and a slight excess of naphthenic acids. Thus, the starting compound for the synthesis of the target compound is actually the source substance. Whereas the bismuth oxide used has a purity of 99% by weight typically, the naphthenic acids, being a UVCB-type substance, are of 100% purity, by definition.
The second source substance used here is bismuth hydroxide nitrate oxide, a soluble form of bismuth(III) compounds, suitable to achieve high Bi3+ concentrations in aqueous biotic systems; this substance was chosen for assessing reproductive toxicity testing as surrogate for bismuth compounds, as it allowed achieving high Bi3+ concentrations and thus a maximum bioavailability, compared to bismuth oxide, being hardly soluble and hardly absorbed.
Thus, the two source compounds naphthenic acids (as surrogate for naphthenate anions) and bismuth hydroxy nitrate oxide (as surrogate for bismuth cations) are appropriate surrogates for assessing the developmental toxicity of the target substance. Furthermore, one other study was identified, a one generation reproductive toxicity study on calcium naphthenate, but was disregarded due to methodological shortcomings, in particular lack of clarity on test substance.

3. ANALOGUE APPROACH JUSTIFICATION
Although the two source substances, naphthenic acids and bismuth hydroxide nitrate oxide, are different in respect of properties compared to the target substance, the read-across is justified, as the source substance bismuth hydroxy nitrate oxide allows to achieve a higher bismuth concentration in aqueous systems and thus better absorption, compared to the target substance (water solubility of < 0.036 mg/L). In a sub-chronic repeated dose toxicity study (OECD 408) also oestrus cycles of females and sperm / testosterone parameters of males were assessed without any findings, even at the high does group of 1000 mg/kg bw/d (equivalent to ~ 3.4 mmol Bi/kg bw/d (based on Bi5H9N4O22). Thus, in absence of effects on oestrus cyclicity and sperm/testosterone parameters, it is concluded that bismuth cations do not have an effect on fertility of males and females.
The second source substance naphthenic acids has been investigated in a combined 28-day repeated dose oral toxicity study with the reproduction/developmental toxicity screening test with a mammalian erythrocyte micronucleus test in rats, essentially an OECD 422 study, amended by a mutagenicity in vivo module (OPPTS 870.3650) as requested by the US EPA. Doses tested were 0 (control), 100, 300 and 900 mg/kg bw/d. No effects on mating index and reproductive organs were seen up to the highest dose group of 900 mg/kg bw/d in this study. There were no weight differences in any of the other organs nor any pathological changes in the reproductive organs up to the highest dose tested (900 mg/kg bw/day). The NOAEL for mating and reproductive organ effects was 900 mg/kg bw/day.
Thus, it can be concluded, that the bismuth(III) cations are of low reproductive toxicity, but also the naphthenic acid anions and the target substance naphthenic acids, bismuth salts does not have any effects on reproductive performance or organs, especially when considering the very low water solubility of the target substance that was determined being < 0.036 mg/L and the expected low absorption rate of the undissociated target substance.

4. DATA MATRIX
The source substance bismuth hydroxy nitrate oxide was found showing no reproductive toxicity when dosed up to 1000 mg/kg bw/d, equivalent to ~ 3.4 mmol Bi/kg bw/d (based on Bi5H9N4O22), and thus this dose was defined as NOAEL for fertility effects in the OECD 408 study, amended by fertility parameters being observed in this study.
In a combined sub-acute oral toxicity study with reproduction toxicity screen (OECD 422) with naphthenic acids grades, a NOAEL of 900 mg/kg bw/d was determined (equivalent to 3.98 mmol/kg bw/d, calculated based on an average of C14, 1-ring naphthenic acid as average value) for reproductive toxicity. No effects on mating or reproductive performance were observed and reproductive organs were not notably affected.
In conclusion, it can be stated that neither bismuth ions nor naphthenic acid ions had negative effects on mating and reproductive organs or sperm parameters/oestrus cyclicity. Thus, naphthenic acids, bismuth salts, the target substance, is not considered to negatively affect fertility.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Dose descriptor:

NOAEL

Effect level:

> 900 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Remarks on result:

not determinable due to absence of adverse toxic effects

Remarks:

no effects on fertility were seen.

Reproductive effects observed:

no

Conclusions:

The source substance bismuth hydroxy nitrate oxide was found showing no reproductive toxicity when dosed up to 1000 mg/kg bw/d, and thus this dose was defined as NOAEL for fertility effects in the OECD 408 study, amended by fertility parameters observed in this study.
In a combined sub-acute oral toxicity study with reproduction toxicity screen (OECD 422) with naphthenic acids grades, a NOAEL of 900 mg/kg bw/d was determined for reproductive toxicity. No effects on mating or reproductive performance were observed and reproductive organs were not notably affected.
In conclusion, it can be stated that neither bismuth ions nor naphthenic acid ions had negative effects on mating and reproductive organs or sperm parameters/oestrus cyclicity. Thus, naphthenic acids, bismuth salts, the target substance, is not considered to negatively affect fertility.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

900 mg/kg bw/day

Study duration:

subacute

Species:

rat

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Effects on developmental toxicity

Description of key information

In conclusion, it can be stated that neither bismuth ions nor naphthenic acid ions had apparent effects on mating and did not produce malformations, but the naphthenic acids had effects on number of offspring, number live born and offspring body weights in the high dose group at doses above maternal toxicity effects (NOAEL for systemic toxicity was set to 100 mg/kg bw/d – see repeated dose toxicity endpoint) in the OECD 422 study. However, no adverse effects were seen in a teratogenicity study according to OECD 414. Thus, naphthenic acids, bismuth salts, the target substance, is not considered to be teratogenic.

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The substance naphthenic acids, bismuth salts is manufactured from bismuth oxide/hydroxide and 3 equivalents of naphthenic acids, resulting in the bismuth tri-naphthenate. Thus, to assess reproductive toxicity, results for bismuth 3+ cations were assessed as well as data for naphthenic acids, the two potential hydrolysis products of the substance. The undissociated substance is considered uncritical, as its molecular mass of ~850 Dalton makes it unlikely that such compounds efficiently pass biological membranes. Thus, the reproductive toxicity on naphthenic acids, bismuth salts will be dominated by its ions, derived from hydrolysis.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The source compound naphthenic acids is the starting material for the manufacturing of naphthenic acids, bismuth salts. Naphthenic acids do contain mainly hydrocarbon acids with a carbon range from 10 - 15 (other naphthenic acids may have wider ranges), with a variable number of cyclics contained (n = 0, 1, 2 and rarely 3). To a minor extent also aliphatics may be present as minor "impurities".
The naphthenic acids are reacted in a slight excess of >3 equivalents of naphthenic acids with bismuth oxide to derive naphthenic acids, bismuth salts, the target substance, containing bismuth tri-naphthenate and a slight excess of naphthenic acids. Thus, the starting compound for the synthesis of the target compound is actually the source substance. Whereas the bismuth oxide used has a purity of 99% by weight typically, the naphthenic acids, being a UVCB-type substance, are of 100% purity, by definition.
The second source substance used here is bismuth hydroxide nitrate oxide, a soluble form of bismuth(III) compounds, suitable to achieve high Bi3+ concentrations in aqueous biotic systems; this substance was chosen for assessing reproductive toxicity testing as surrogate for bismuth compounds, as it allowed achieving high Bi3+ concentrations and thus a maximum bioavailability, compared to bismuth oxide, being hardly soluble and hardly absorbed.
Thus, the two source compounds naphthenic acids (as surrogate for naphthenate anions) and bismuth hydroxy nitrate oxide (as surrogate for bismuth cations) are appropriate surrogates for assessing the developmental toxicity of the target substance. Furthermore, two other studies were identified (a one generation reproductive toxicity study on calcium naphthenate and a published thesis on developmental toxicity, applying Athabasca oil sands, that do contain naphthenic acids, but both were disregarded due to methodological shortcomings, in particular lack of clarity on test substances.

3. ANALOGUE APPROACH JUSTIFICATION
Although the two source substances, naphthenic acids and bismuth hydroxide nitrate oxide, are different in respect of properties compared to the target substance, the read-across is justified, as the source substance bismuth hydroxy nitrate oxide allows to achieve a higher bismuth concentration in aqueous systems and thus better absorption, compared to the target substance (water solubility of < 0.036 mg/L). In a teratogenicity study according to OECD 414 in rats, this substance was investigated for developmental toxicity and no adverse effects were seen at the highest dose tested, i.e. 1000 mg/kg bw/d (equivalent to ~ 3.4 mmol Bi/kg bw/d (based on Bi5H9N4O22).
The second source substance naphthenic acids has been investigated in a combined 28-day repeated dose oral toxicity study with the reproduction/developmental toxicity screening test with a mammalian erythrocyte micronucleus test in rats, essentially an OECD 422 study, amended by a mutagenicity in vivo module (OPPTS 870.3650) as requested by the US EPA. Doses tested were 0 (control), 100, 300 and 900 mg/kg bw/d. No neurotoxic effects were seen in any dose group. The NOAEL for systemic maternal toxicity was set to 100 mg/kg bw/d, due to 2 mortalities in the high dose group females and statistically significant effects on liver and kidney weight increase in the high dose and to a lesser extent also in the mid dose group. Treatment of Sprague-Dawley rats with refined naphthenic acids had no apparent effects on mating and did not produce malformations at the highest dose tested (900 mg/kg/day). However, there were significant reductions in number of offspring, number live born and offspring body weights. The NOAEL for developmental toxicity was set to 300 mg/kg bw/d in this study.
Additionally, an OECD 414 study with naphthenic acids with dosing by gavage to rats was performed, and in this study the NOAEL maternal toxicity as well as for teratogenicity were both set to 1000 mg/kg bw/d, in lack of signs of developmental toxicity.
Thus, it can be concluded, that the bismuth(III) cations are of low reproductive toxicity, whereas the findings on naphthenic acids are more decisive for the reproductive toxicity of the target substance naphthenic acids, bismuth salts, especially when considering the very low water solubility of the target substance that was determined being < 0.036 mg/L and the expected low absorption rate of the undissociated target substance. However, as the target substance does contain free naphthenic acids (~10%) due to a slight excess used during production, the naphthenic acids findings have to be considered for assessing the systemic toxicity of the target substance.

4. DATA MATRIX
The source substance bismuth hydroxy nitrate oxide was found showing no developmental toxicity when dosed up to 1000 mg/kg bw/d, equivalent to ~ 3.4 mmol Bi/kg bw/d (based on Bi5H9N4O22), and thus this dose was defined as NOAEL in this study.
In a combined sub-acute oral toxicity study with reproduction toxicity screen (OECD 422) with naphthenic acids grades, a NOAEL of 100 mg/kg bw/d was determined (equivalent to 0.44 mmol/kg bw/d, calculated based on an average of C14, 1-ring naphthenic acid as average value) for maternal toxicity and a NOAEL of 300 mg/kg bw for developmental toxicity, due to significant reductions in number of offspring, number live born and offspring body weights in the high dose group. Treatment of Sprague-Dawley rats with refined naphthenic acids had no apparent effects on mating and did not produce malformations at the highest dose tested (900 mg/kg/day) in this study.
In a dedicated teratogenicity study according to OECD 414, no adverse effects were seen when naphthenic acids were dosed by gavage during days 5 – 19 of gestation, and accordingly the NOAEL for maternal and developmental toxicity in this study were both set to 1000 mg/kg bw/d.
In conclusion, it can be stated that neither bismuth ions nor naphthenic acid ions had apparent effects on mating and did not produce malformations, but the naphthenic acids had effects on number of offspring, number live born and offspring body weights in the high dose group at doses above maternal toxicity effects (NOAEL for systemic toxicity was set to 100 mg/kg bw/d – see repeated dose toxicity endpoint) in the OECD 422 study. However, no adverse effects were seen in a teratogenicity study according to OECD 414. Thus, naphthenic acids, bismuth salts, the target substance, is not considered teratogenic.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

other: disregarded study

Remarks:

test substance identity unclear

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Basis for effect level:

organ weights and organ / body weight ratios

Remarks on result:

other: NOAEL adjusted to target substance

Dose descriptor:

NOAEL

Effect level:

ca. 400 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

fetal/pup body weight changes

Remarks on result:

other: NOAEL adjusted to target substance

Developmental effects observed:

yes

Lowest effective dose / conc.:

400 mg/kg bw/day

Treatment related:

yes

Relation to maternal toxicity:

developmental effects as a secondary non-specific consequence of maternal toxicity effects

Dose response relationship:

yes

Relevant for humans:

not specified

Conclusions:

In two OECD 414 studies with bismuth hydroxide nitrate oxide and naphthenic acids, respectively, a NOAEL for teratogenicity of 1000 mg/kg bw/d was found, in absence of teratogenic effects. However, in an OECD 422 study with naphthenic acids effects on number of offspring, number live born and offspring body weights in the high dose group were seen, resulting in a NOAEL of 300 mg naphthenic acids/kg bw/d (adjusted to naphthenic content in naphthenic acids, bismuth salts being ~ 400 mg naphthenic acids, bismuth salts/kg bw/d), but in this study systemic maternal toxicity was seen at 100 mg/kg bw/d (adjsued to target substance being 136 mg naphthenic acids, bismuth salts/kg bw/d. Hence, in conlsuion reproductive effect in absence of maternal toxicity were not seen and the substance is not considered being teratogenic.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

136 mg/kg bw/day

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

Justification for classification or non-classification

In studies investigating effects on fertility of bismuth compounds and naphthenic acids, no negative effects on fertility were seen. In developmental toxicity studies according to OECD 414 also no negative effects on developmental toxicity were noted. Only in the OECD 422 study with naphthenic acids, effects on pups were seen at maternally toxic levels. Thus, the substance is not required to be classified for reprodcutive toxicity according to CLP (Regulation EC No. 1272/2008).