Screening-Level Hazard Characterization Cobalt Naphthenate (CASRN 61789-51-3)

U.S. Environmental Protection Agency June, 2015

Hazard Characterization

SCREENING-LEVEL HAZARD CHARACTERIZATION

Cobalt Naphthenate
(CASRN 61789-51-3)

The High Production Volume (HPV) Challenge Program1 was conceived as a voluntary initiative aimed
at developing and making publicly available screening-level health and environmental effects
information on chemicals manufactured in or imported into the United States in quantities greater than
one million pounds per year. In the Challenge Program, producers and importers of HPV chemicals
voluntarily sponsored chemicals; sponsorship entailed the identification and initial assessment of the
adequacy of existing toxicity data/information, conducting new testing if adequate data did not exist, and
making both new and existing data and information available to the public. Each complete data
submission contains data on 18 internationally agreed to "SIDS" (Screening Information Data Set1'2)
endpoints that are screening-level indicators of potential hazards (toxicity) for humans or the
environment.

The Environmental Protection Agency's Office of Pollution Prevention and Toxics (OPPT) is evaluating
the data submitted in the HPV Challenge Program on approximately 1400 sponsored chemicals by
developing hazard characterizations (HCs). These HCs consist of an evaluation of the quality and
completeness of the data set provided in the Challenge Program submissions. They are not intended to
be definitive statements regarding the possibility of unreasonable risk of injury to health or the
environment.

The evaluation is performed according to established EPA guidance2'3 and is based primarily on hazard
data provided by sponsors; however, in preparing the hazard characterization, EPA considered its own
comments and public comments on the original submission as well as the sponsor's responses to
comments and revisions made to the submission. In order to determine whether any new hazard
information was developed since the time of the HPV submission, a search of the following databases
was made from one year prior to the date of the HPV Challenge submission to the present: (ChemID to
locate available data sources including Medline/PubMed, Toxline, HSDB, IRIS, NTP, ATSDR, IARC,
EXTOXNET, EPA SRS, etc.), STN/CAS online databases (Registry file for locators, ChemAbs for
toxicology data, RTECS, Merck, etc.), Science Direct and ECHA.4 OPPT's focus on these specific
sources is based on their being of high quality, highly relevant to hazard characterization, and publicly
available.

OPPT does not develop HCs for those HPV chemicals which have already been assessed internationally
through the HPV program of the Organization for Economic Cooperation and Development (OECD)
and for which Screening Initial Data Set (SIDS) Initial Assessment Reports (SIAR) and SIDS Initial
Assessment Profiles (SIAP) are available. These documents are presented in an international forum that
involves review and endorsement by governmental authorities around the world. OPPT is an active
participant in these meetings and accepts these documents as reliable screening-level hazard
assessments.

1 U.S. EPA. . High Production Volume (HPV) Challenge Program; http://www.epa.gov/chemrtk/index.htm.

2 U.S. EPA. . HPV Challenge Program - Information Sources; http://www.epa.gov/chemrtk/pubs/general/guidocs.htm.

3 U.S. EPA. . Risk Assessment Guidelines; http://cfpub.epa.gov/ncea/raf/rafguid.cfm.

4 European Chemicals Agency, http: //echa. europa.eu.

-------
U.S. Environmental Protection Agency
Hazard Characterization

June, 2015

These hazard characterizations are technical documents intended to inform subsequent decisions and
actions by OPPT. Accordingly, the documents are not written with the goal of informing the general
public. However, they do provide a vehicle for public access to a concise assessment of the raw
technical data on HPV chemicals and provide information previously not readily available to the public.

2

-------
U.S. Environmental Protection Agency
Hazard Characterization

June, 2015

Chemical Abstract
Service Registry
Number

61789-51-3

(CASRN)

Chemical Abstract
Index Name

Naphthenic acids, cobalt salts

Structural Formula

O Co'

Representative5 SMILES:

0=C(0[Co]OC(CCCCCC4CCC3CCCC34)=0)CCCCCC2CCClCCCC12

Summary

Cobalt naphthenate is a complex mixture that is available commercially as a petroleum-based solvent
or a mineral spirit solution. It possesses moderate water solubility and negligible vapor pressure and is
expected to have low mobility in soil. Volatilization of cobalt naphthenate is considered negligible
since it's a salt. Cobalt naphthenate is expected to dissociate in water to the cobalt cation and
naphthenic acid or its conjugate base, both of which are stable in water. The rate of atmospheric
photooxidation is considered moderate; however, this is not a relevant environmental degradation
pathway since salts are not expected to exist in the vapor phase in the atmosphere. Cobalt naphthenate
is expected to have low persistence (PI) and low bioaccumulation potential (Bl).

The acute oral toxicity of cobalt naphthenate in rats is low. Cobalt naphthenate induced gene
mutations in bacteria but did not induce gene mutations in mammalian cells in vitro. Cobalt
naphthenate is irritating to rabbit skin and eyes. Adequate data were not available for the repeated-
dose, reproductive, developmental and genetic toxicity (chromosomal aberrations) endpoints.

The evaluation of the potential hazard of cobalt naphthenate to fish, aquatic invertebrates and aquatic
plants cannot be completed because no adequate data were available for these endpoints.

Data gaps for the repeated-dose, reproductive, developmental and genetic (chromosomal aberrations)
toxicity, and the acute toxicity to fish and aquatic invertebrates, and toxicity to aquatic plants
endpoints were identified under the HPV Challenge Program.

5 The ring type and carbon number distributions of naphthenic acids from an acidic Californian crude oil was approximately
6% 0-ring naphthenic acids; 32% 1-ringed naphthenic acids; 38% 2-ringed naphthenic acids; 15% 3-ringed napthenic acids;
5% 4-ringed napthenic acids; 3% 5-ringed napthenic acids; 1% 6-ringed napthenic acids. See: Hsu CS; Dechert GJ; Robbins
WK et al. 2000. Napthenic Acids in Crude Oil Characterized by Mass Spectroscopy. Energy & Fuels 14:217-223.

-------
U.S. Environmental Protection Agency
Hazard Characterization

June, 2015

The sponsor, Metal Carboxylates Coalition (OM Group, Inc., The Shepherd Chemical Company and
Troy Corporation), submitted a Test Plan and Robust Summaries to EPA for cobalt naphthenate
(CASRN 61789-51-3; CA Index name: naphthenic acids, cobalt salts) on December 28, 2005. EPA
posted the submission on the ChemRTK HPV Challenge website on March 15, 2006
(http://www.epa.gov/oppt/chemrtk/pubs/summaries/metalcarb/cl4172tc.htm). Cobalt naphthenate was
originally submitted as a subcategory in the metal carboxylates category for which an original test plan
and robust summaries were submitted to EPA on December 27, 2002. EPA posted comments on the
original category submission to the ChemRTK website on May 22, 2003. Public comments were also
received and posted to the website. No EPA comments specific to the single chemical submission for
cobalt naphthenate have been posted to the website to date.

Justification for Supporting Chemical

The sponsor submitted data for two supporting chemicals: naphthenic acids (CASRN 1338-24-5) and
cobalt (II) chloride (CASRN 7646-79-9).

The submitter expects complete dissociation of the sponsored chemical to these supporting chemicals at
environmentally and physiologically relevant pH values. However, EPA considers that the submitter did
not adequately address the issue of stability of the metal-ligand complex and instead submitted an acid
(pKa) dissociation constant study. Therefore, the stability of the metal-ligand complex still needs to be
addressed. It is very possible that this compound is stable and does not readily dissociate at neutral pH.

The sponsor also justifies the use of the supporting chemicals based on assumed bioequivalency of the
cobalt ion in the sponsored chemical to the cobalt ion in soluble cobalt salts, such as cobalt chloride.
However, the data submitted to support bioequivalency rely heavily on theory and several in vitro
studies that cannot be interpreted because the sponsors presented insufficient detail about the
experimental method in either the test plan or the robust summaries.

Furthermore, EPA considers that separate evaluation of the dissociation products did not address
potential interactions (e.g., additivity, synergism or antagonism) among the various associated and
dissociated species that may be present in different biological environments.

Therefore, the proposed use of supporting chemicals is not supported for either human health or aquatic
toxicity assessment and the submitted data for these chemicals are not used in this hazard
characterization.

1. Chemical Identity

1.1 Identification and Purity

Cobalt naphthenate is a complex mixture that is available commercially as a petroleum-based solvent or
a mineral spirit solution.

1.2 Physical-Chemical Properties

The available physical-chemical properties of cobalt naphthenate are summarized in Table 1.

-------
U.S. Environmental Protection Agency
Hazard Characterization

June, 2015

Table 1. Physical-Chemical Properties of Cobalt naphthenate1

Property

Value

CASRN

61789-51-3

Molecular Weight

5062

Physical State

Solid3

Melting Point

77 °C (measured for a product containing 10.5% cobalt)

Boiling Point

315 - 380 °C (measured for a product containing 6% cobalt)

Vapor Pressure

<1.0><10"10 mm Hg at 25°C (estimated)4'5

Dissociation Constant

(pKa)

6.74 and 8.9 (measured)

Henry's Law Constant

<1.0x10"10 atm-m3/mole (estimated)4'5

Water Solubility

34.28 mg/L at 20°C (measured)

Log Kow

1.1 at 20°C (measured)6'7
8.95 (estimated)4'5

2 The value represents the molecular weight of the representative structure used in the estimations.

3 Cobalt naphthenate does not exist commercially as a pure chemical substance, but instead is available only in a
petroleum-based solvent or a mineral spirit solution. A typical commercial product may consist of 55% cobalt
naphthenate, 43% mineral spirit and a small amount of other substances.

4 U.S. EPA. 2011. Estimation Programs Interface Suite™ for Microsoft® Windows, v4.10. U.S. Environmental
Protection Agency, Washington, DC, USA. Available online from:
http://www.epa.gov/opptintr/exposure/pubs/episuitedl.htm as of October 28, 2011.

5 EPIWIN has not been validated for chemicals that contain metals, such as cobalt, in their molecular structure;
therefore, there is uncertainty associated with the calculated values and they should be used with caution whenever
they are reported.

6 The Metal Carboxylates Coalition. 2006. Test Plan and Robust Summary for Naphthenic acids, zinc salts.
Available online at http://www.epa. gov/chemrtk/pubs/summaries/metalcarb/c 14172tc.htm as of October 28, 2011.

7 Data for naphthenic acids, zinc salts (CASRN 12001-85-3).

2. General Information on Exposure

2.1 Production Volume and Use Pattern

CASRN 61789-32-0 had an aggregated production and/or import volume in the United States less than
500,000 pounds during calendar year 2005.

No industrial processing and uses, and commercial and consumer uses were reported for the chemical.

2.2 Environmental Exposure and Fate

Cobalt naphthenate is expected to have low mobility in soil. No biodegradation data exists for this
substance; however biodegradation data for commercial naphthenic acids suggest that naphthenic acids,
cobalt salts will not be highly persistent in the environment. Commercial mixtures of the sodium salts of
naphthenic acids were shown to degrade and mineralize to CO2 when inoculated with microbial
populations indigenous to oil sands tailings. Approximately 50% of the organic carbon was converted to

-------
U.S. Environmental Protection Agency
Hazard Characterization

June, 2015

CO2 over a 24-day period. Three of four model naphthenic acid compounds were also degraded by the
enrichment cultures, with approximately 40-50% of the organic carbon converted to CO2 over a 24-day
period. Additional studies examined the concentration and composition of naphthenic acids in aerobic
biodegradation studies using sodium salts of naphthenic acids. Within 10 days of incubation with
enrichment cultures on naphthenic acid-degraders, naphthenic acids concentration dropped from about
100 to <10 mg/L, accompanied by release of about 60% of the carbon as CO2. The rate of volatilization
is negligible since the substance is a salt. Cobalt naphthenate dissociates in water to the cobalt cation and
naphthenic acid or its conjugate base, both of which are stable in water. The rate of atmospheric
photooxidation is considered moderate; however, this is not a relevant environmental degradation
pathway since salts are not expected to exist in the vapor phase in the atmosphere. Cobalt naphthenate is
expected to have low persistence (PI) and low bioaccumulation potential (Bl).

The environmental fate of cobalt naphthenate is summarized in Table 2.

Table 2. Environmental Fate Characteristics of Cobalt Naphthenate1

Property

Value

Photodegradation Half-
life

4.1 hours (estimated)2'3

Hydrolysis Half-life

Stable

Biodegradation

Half-life approximately 1 day

Bi oconcentrati on

BAF = 2.2 (estimated)2'3

Log Koc

5.8 (estimated)2'3

Fugacity

(Level III Model)2'3

Air (%)

<0.1

Water (%)

1.9

Soil (%)

46.9

Sediment (%)

51.2

Persistence4

PI (low)

Bi oaccumul ati on4

Bl (low)

1 The Metal Carboxylates Coalition. Test Plan and Robust Summary for Naphthenic acids, cobalt salts. January 3,
2006. Available at: http://www.epa.gov/chemrtk/pubs/summaries/metalcarb/cl4172tc.htm as of October 28, 2011.
2U.S. EPA. 2011. Estimation Programs Interface Suite™ for Microsoft® Windows, v4.10. U.S. Environmental
Protection Agency, Washington, DC, USA. Available online at
http://www.epa.gov/opptintr/exposure/pubs/episuitedl.htm as of October 4, 2011.

3 EPIWIN has not been validated for chemicals that contain metals, such as cobalt, in their molecular structure;
therefore, there is uncertainty associated with the calculated values and they should be used with caution whenever
they are reported.

4Federal Register. 1999. Category for Persistent, Bioaccumulative, and Toxic New Chemical Substances. Federal
Register 64, Number 213 (November 4, 1999) pp. 60194-60204.

Conclusion: Cobalt naphthenate is a complex mixture that is available commercially as a petroleum-
based solvent or a mineral spirit solution. It possesses moderate water solubility and negligible vapor
pressure and is expected to have low mobility in soil. Volatilization of cobalt naphthenate is considered
negligible since it's a salt. Cobalt naphthenate is expected to dissociate in water to the cobalt cation and

-------
U.S. Environmental Protection Agency
Hazard Characterization

June, 2015

naphthenic acid or its conjugate base, both of which are stable in water. The rate of atmospheric
photooxidation is considered moderate; however, this is not a relevant environmental degradation
pathway since salts are not expected to exist in the vapor phase in the atmosphere. Cobalt naphthenate is
expected to have low persistence (PI) and low bioaccumulation potential (Bl).

3. Human Health Hazard

A summary of the available health effects data submitted for SIDS endpoints is provided in Table 3.

Acute Oral Toxicity

(1) Albino Sprague-Dawley rats (2 or 3/sex/dose) were administered cobalt naphthenate (percentage of
cobalt not completely legible in source document6) via gavage as a 50% solution in corn oil at 2000,

2510, 3160 or 3980 mg/kg and observed for up to 7 days following dosing. Mortality occurred at > 2510
mg/kg. Additional details are from TSCATS (OTS0512205).

LDso = 2800 mg/kg

(2) Young adult male ChR-CD rats (5/dose) were administered cobalt naphthenate (purity not specified)
via gavage as a 25% solution in peanut oil at 1000, 2000 or 4000 mg/kg and observed for 14 days
following dosing. Mortality occurred at > 2000 mg/kg. Additional details are from TSCATS
(OTS0215503).

LD50 = 2828 mg/kg

Acute Dermal Toxicity

No adequate data.

Repeated-Dose, Reproductive and Developmental Toxicity
No adequate data.

Genetic Toxicity — Gene Mutation
In vitro

(1) Cobalt naphthenate was tested in several Salmonella typhimurium strains (TA98, TA100, TA1537
and TA1538) at concentrations of ranging from 100 to 10,000 |ig/plate, with and without metabolic
activation. . No information was provided on negative or positive controls or cytotoxicity. Negative
results were obtained for all strains except TA98 with metabolic activation.

Cobalt naphthenate was mutagenic in this assay.

6 The sponsor noted that they believed that the illegible percentage of cobalt for the acute oral and dermal studies and
irritation studies provided in TSCATS (OTS0512205) was 11%. Although the value in the report is difficult to read, it
appears to be 17% cobalt.

-------
U.S. Environmental Protection Agency
Hazard Characterization

June, 2015

(2) Cobalt naphthenate was tested in L5178Y mouse lymphoma cells at concentrations ranging from
0.01 to 0.049 [xL/mL without metabolic activation and from 0.03 to 0.17 [xL/mL with metabolic
activation. No information was provided on negative or positive controls or cytotoxicity. Negative
results were obtained both in the presence and absence of metabolic activation.

Cobalt naphthenate was not mutagenic in this assay.

Genetic Toxicity — Chromosomal Aberrations
In vitro

No adequate data.

Additional Information
Skin Irritation

Undiluted cobalt naphthenate (percentage of cobalt not completely legible in source document) was
applied to the clipped intact skin of three Albino New Zealand White rabbits under occluded conditions
for 24 hours. Rabbits were observed for a period of 7 days for irritation, which was scored following the
Draize method. Slight edema was observed at 24 hours and the average irritation score was 2 out of 8.
All signs of irritation cleared within 72 hours. Additional details are from TSCATS (OTS0512205).
Cobalt naphthenate was slightly irritating to rabbit skin in this study.

Eye Irritation

(1) Undiluted cobalt naphthenate (percentage of cobalt not completely legible in source document) was
administered in the conjunctival sac of the right eye of each of three albino rabbits (two males and one
female) for 24 hours, at which time eyes were rinsed. The left eye of each rabbit served as an untreated
control. Rabbits were observed for a period of 7 days for irritation, which was scored following the
Draize method. Observations at 24 hours included moderate erythema, very slight to slight edema and
copious discharge containing whitish exudates. All signs of irritation cleared within 120 hours.
Additional details are from TSCATS (OTS0512205).

Cobalt naphthenate was slightly irritating to rabbit eyes in this study.

(2) Cobalt naphthenate (percent of cobalt not specified) was instilled into one conjunctival sac of each of
two albino rabbits (sex not specified) as either an undiluted powder, a 10% suspension in propylene
glycol, a 6% suspension in mineral spirits or 0.15% in cyclohexane. The other eye of each rabbit served
as an untreated control. Test eyes of one rabbit in each treatment group were rinsed after 20 seconds of
contact. Rabbits were observed for a period of up to 4 days for irritation. The scoring method was not
provided. Mild transient conjunctival irritation was observed in all treatment groups. Washing the eyes
with water did not appreciably lessen the irritation. Irritation cleared within 4 days after treatment.
Cobalt naphthenate was slightly irritating to rabbit eyes in this study.

Conclusion: The acute oral toxicity of cobalt naphthenate in rats is low. Cobalt naphthenate induced
gene mutations in bacteria but did not induce gene mutations in mammalian cells in vitro. Cobalt
naphthenate is irritating to rabbit skin and eyes. Adequate data were not available for the repeated-dose,
reproductive, developmental and genetic toxicity (chromosomal aberrations) endpoints.

-------
U.S. Environmental Protection Agency
Hazard Characterization

June, 2015

Table 3. Summary Table of the Screening Information Data Set
under the U.S. HPV Challenge Program -Human Health Data

Endpoints

Cobalt naphthenate
(689-11-2)

Acute Oral Toxicity
LDso (mg/kg)

2800

Repeated-Dose Toxicity
NOAEL/LOAEL

No Data

Reproductive Toxicity
NOAEL/LOAEL

No Data

Developmental Toxicity
NOAEL/LOAEL

No Data

Genetic Toxicity - Gene Mutation
In vitro

Positive (bacteria)
Negative (mammalian cells)

Genetic Toxicity - Chromosomal Aberrations
In vitro

No Data

Additional Information
Skin Irritation
Eye Irritation

Slightly irritating
Slightly irritating

Measured data in BOLD

4. Hazard to the Environment

Acute Toxicity to Fish and Aquatic Invertebrates and Toxicity to Aquatic Plants

There were no adequate data available to address aquatic toxicity endpoints for cobalt naphthenate.

Conclusion: There were no adequate data available to address aquatic toxicity endpoints for cobalt
naphthenate.

9

-------