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Full text of "Scientific criteria document for the development of a provincial water quality objective for cobalt (stable isotope) : report"

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SCIENTIFIC CRITERIA DOCUMENT 
FOR THE DEVELOPMENT OF 
A PROVINCIAL WATER QUALITY 
OBJECTIVE FOR COBALT 
(STABLE ISOTOPE) 



OCTOBER 1996 




Ministry of 

Ontario '"^'°"'"" 



and Energy 



ISBN 0-7778-4673-X 



SCIENTIFIC ClUTERIA DOCUMENT 

FOR THE DEVELOPMEN I OF 

A PROVINCIAL WATER QUALITY OBJECTIVE 

FOR COBALT 

(STABLE ISOTOPE) 



OCTOBER 1996 



® 



Cade publication tcchniciuc 
n"est disponible qucii anglais. 

Copyriglil; Queen's Printer for Ontario. 1996 

Ttiis publication may be reproduced for non-commercial purpo.ses 

with appropriate attribution. 



PIBS 336 IE 



SCIENTIFIC CRITERIA DOCUMENT 

FOR THE DEVELOPMENT OF 

A PROVINCIAL WATER QL AUTY OBJECITVE 

FOR COBALT 

(STABLE ISOTOPE) 



Report prepared by: 
T. Flelcher'. G.L. Stephenson-, J. Wang- and CD. Wren- 



' Standards Development Branch 
Ontario Ministry of Environment and Energy 

-Ecological Services for Planning Ltd. 

361 Southgate Drive 

Giicipli, Ontario 

K I G 3M5 



PREFACE 

The Ontario Ministry of Environment and Energy develops Provincial Water Quality 
Objectives, or Interim Objectives, for tliose substances deemed to be of greatest 
environmental concern in Ontario. These as determined through a screening process 
which considers persistence, potential to bioaccumulate, acute and chronic toxicity and 
potential presence in the aquatic environment. Alternatively, Ministry staff who have a 
direct responsibility for managing possible effects of these chemicals may request an 
evaluation. 

Provincial Water Quality Objectives and Interim Objectives (PWQO/IOs) are numeric or 
narrative criteria intended to protect all life stages of aquatic organisms for indefinite 
exposures and/or to protect recreational uses of water. PWQO/IOs for recreational uses, 
including swimming, are currently based on microbiological and aesthetic considerations. 
The potential for harmful effects from exposure to chemical substances during recreational 
uses is unknown at present, but will be considered when scientific information becomes 
available. Ontario Drinking Water Objectives and sport fish consumption guidelines are 
also considered in protection of human health. PWQO/IOs represent a desirable water 
quality for the protection of designated uses of surface waters in Ontario. PWQO/IOs do 
not take into account analytical detection or quantification limits, treatability or removal 
potential, socio-economic factors, natural background concentrations, or potential transport 
of contaminants among air, water and soil. These factors are considered in policies and 
procedures which govern the uses of PWQO/IOs, contained in the booklet. Water 
Management: Policies, Guidelines and Provincial Water Quality Objectives of the Ministry 
of Environment and Energy (OMOEE 1994a), which deals with all aspects of Ontario's 
water management policy. 

The process for deriving these criteria is detailed in Ontario's Water Quality Objective 
Development Process (OMOE 1992a). The toxicology literature is reviewed for all of the 
following areas: aquatic toxicity, bioaccumulation, mutagenicity, and aesthetic 
considerations. The final Objective/Interim Objective is based on the lowest effect 



concentration reported for any of tfiese factors on aquatic organisnns as well as taste and 
odour considerations of the water. Where there are reliable and adequate data, an 
Objective is developed using a safety factor. Where there are fewer data, an interim 
Objective is developed using an "uncertainty factor". The size of the uncertainty factor 
reflects the availability of appropriate data and the potential of the material to 
bioaccumulate. Interim Objectives can be promoted to Objectives when sufficient reliable 
data become available. 

PWQO/IOs are used to designate surface waters of the Province which should not be 
further degraded. They are also used in receiving water discharge assessments and may 
be included in Certificates of Approval which are issued to regulate effluent discharges. 
Where better water quality is required to protect other beneficial uses of the environment in 
a given location, appropriate criteria and factors, including public health considerations, are 
taken into account. 



ACKNOWLEDGEMENTS 

The authors would like to thank members of the MOEE Aquatic Criteria Development 
Committee, and specifically Gary Westlake, Dave Rokosh, and Mike Salamone, from 
Standards Development Branch, for the review of the first draft of this document. 

The authors would especially like to thank the peer reviewers from outside of Standards 
Development Branch. Thanks go to W. Frais (Bayer Rubber Inc.), W. Ng (Regional 
Operations Division, MOEE), J. Hawley (MISA - MOEE), D. Skingsley (York University, 
UK). R. Playle (Wilfred Laurier University), N. Nagpal (B.C. Environment), J. Johnston 
(Lakefield Research), K.J. Buhl (U.S. Department of Interior, National Biological Service), 
and from Environment Canada, S. Teed, C. Jefferson, D. Andersen, C. Dumaresq, A. 
Pawlisz and S. Munger, 



IV 



SUMMARY 

A Provincial Water Quality Objective (PWQO) was developed for cobalt for the protection 
of aquatic life. Available information on the physical-chemical properties, aquatic toxicity, 
bioaccumulation potential, taste and odour characteristics and genotoxicity potential of 
cobalt were considered in developing the Objective. 

Cobalt is an element which occurs naturally in the earth's crust. Approximately 10% of the 
world's total production of cobalt comes from Canada. Cobalt is used in various alloys, as 
a catalyzing agent, fertilizer and as a colouring agent in glass and ceramics. It is also 
used in the medical field and as a farm feed additive. 

Cobalt is found in trace amounts in surface waters of Ontario. In the Great Lakes, total 
cobalt concentrations rarely exceed the detection limit of 1 |jg/L, however concentrations 
as high as 80 pg/L have been reported in surface water near mine tailings. 

Cobalt exists in surface waters mainly as the divalent and trivalent forms. Cobalt is 
strongly adsorbed on suspended solids and sediments, Therefore very low concentrations 
are found in the dissolved state. In most ecosystems, the sediment is the primary sink for 
cobalt. 

Compared to other metals, cobalt is slightly to moderately toxic. The literature indicates 
that acute effects for a variety of aquatic lile occur between 1 mg/L and 450 mg/L. 
Chronic effects range from 0.009 mg/L to 2 500 mg/L. Cobalt does not appear to 
bioaccumulate to any significant degree in fish. 

There was sufficient aquatic toxicity data available to derive a Provincial Water Quality 
Objective. The recommended PWQO for cobalt is 0.0009 mg/L (0.9 pg/L) derived by 
dividing the lowest acceptable effect concentration of 0.009 mg/L (28d reproduction 
impairment and reduced survival of Daphnia magna) by an safety factor of 10. 

The PWQO is above the OMOEE laboratory detection limit, however due to difficulties in 
analysis, often the detection limit may be higher than the PWQO. This value should be 
protective of effects due to aquatic toxicity, bioaccumulation, taste and odour effects. 
There are indications that exposure to cobalt may cause mutagenicity. However insufficient 
information was available to assess these effects on aquatic organisms. 

Note: Concentrations in this document are expressed in a number of different units 
commonly used in scientific papers. The conversion factors are: 

1 gram per litre (g/L) = 1000 milligrams per litre (mg/L) 

1 milligram per litre (mg/L) = 1000 micrograms per litre (pg/L) 



TABLE OF CONTENTS 

PREFACE ii 

ACKNOWLEDGEMENTS iv 

SUMMARY V 

TABLE OF CONTENTS vi 

1 INTRODUCTION 1 

1.1 PRODUCTION AND USES 1 

1.2 AQUATIC SOURCES AND FATE 2 

1.3 AMBIENT CONCENTRATIONS IN ONTARIO WATERS 3 

1 .4 AQUATIC CHEMISTRY 6 

2.0 TOXICITY TO AQUATIC ORGANISMS 7 

2.1 ACUTE TOXICITY 8 

2.1 .1 Vertebrates 8 

2.1 .2 Invertebrates 9 

2.2 CHRONIC TOXICITY 11 

2.2.1 Vertebrates 11 

2.2.2 Invertebrates 12 

2.2.3 Ottier Organisms (Algae. Prolists etc.) 14 

2.3 SUMMARY OF TOXICITY DATA 15 

2.4 EFFECTS OF WATER QUALITY PARAMETERS ON TOXICITY 17 

3.0 BIOACCUMULATION 18 

4.0 IMPACT ON TASTE AND ODOUR OF WATER AND FISH TAINTING 19 

5.0 MUTAGENICITY 19 

6.0 DERIVATION OF THE PROVINCIAL WATER QUALITY OBJECTIVE 21 

6.1 Toxicological data 21 

6.2 Bioaccumulation 22 

6.3 Mutagenicity : 22 

6.4 Taste and Odour 22 

6.5 Other Effects 22 

6.6 Dermal Effects 23 

6.7 OMOEE Laboratory Detection Limits 23 

6.8 Conclusion 23 

7.0 RESEARCH NEEDS 24 

8.0 OBJECTIVES OF OTHER AGENCIES 25 



VI 



9.0 REFERENCES '. 26 

List of Tables 

Table 1. Toxicity Ranking of Cobalt Compared to Other Metals 17 

Table 2. Aquatic Toxicity Data Table for Cobalt 35 

Table 3. Data Requirements for Provincial Water Quality Objectives .... 40 



LIST OF FIGURES 

Figure 1a. Objective Derivation Graph - Acute 43 

Figure lb. Objective Derivation Graph - Chronic 44 



VII 



1.0 INTRODUCTION 

Cobalt (Co) is a silver-grey, hard, magnetic, ductile, and somewhat malleable metal similar 
to nickel and iron in appearance (Sax and Lewis 1989; Weast et al. 1987: Windholz et al. 
1983). It is the 30th most abundant element on earth and comprises approximately 
0.0025% of the earth's crust (Kirk et al. 1979). ASTDR (1991) reports that cobalt 
frequently occurs in nature in association with nickel, and often with arsenic. In Cobalt, 
Ontario, deposits of cobalt occur with silver (Hawley, Pers. comm). Cobalt is found in 
various rock types present in Ontario, namely granite, basalt, shale, limestone, and 
sandstone. Common ores may contain the minerals cobaltite (CoS^.CoASj), linnaeite 
(C03SJ, carrollite, safflorite, skutterudite, smaltite (CoASj), and erythrite 
(3CoO.AS2O5.8H2O) (Shamberger 1979; Windholz et al. 1983). The average total cobalt 
concentration in Ontario soils is 4.4 mg/kg (Young 1979), while that in tailings deposits is 
83 mg/kg (Hawley, 1980). 

Cobalt is an essential nutrient required for vitamin B,2 metabolism. In mammals, Co 
deficiency and low levels of vitamin B.j result in pernicious anemia, whereas excess results 
in polycythemia (Martell 1975). 

1.1 PRODUCTION AND USES 

Cobalt was used as a colouring agent as far back as 2000 BC by the Egyptians, and later 
by the Assyrians, Greeks, Romans, and Chinese (Kirk et al. 1979). By the 17th century, 
Europeans had discovered methods of mining cobalt and used it to colour glass and 
pottery. In 1914, the first cobalt produced commercially in the world was manufactured at 
Deloro, Ontario. The plant at Deloro was closed down in 1961 due to the slumping 
demand for cobalt (Azcue and Nriagu 1993). Today there are numerous uses for cobalt, 
including uses in the industrial, agricultural and medical sectors. 

Important cobalt deposits occur in Zaire, Morocco, Australia, and Canada (Weast et al. 
1987). The reserves of Canada and Australia comprise about one quarter of the world 

1 



supply (Kirk et al. 1979). Emsley (1991) reports that 1984 world production of cobalt was 
19 000 tonnes. In Canada, cobalt is produced mainly in Ontario and Manitoba (CCREM 
1987) as a by-product of nickel-copper production. 

Giancola (1994) reports that in 1993 there were nine mines in Ontario which produce 
cobalt. All were in the Sudbury area. Cobalt is only incidently mined from these deposits, 
primary ores are nickel, silver and copper (Hawiey, Pers. comm). In 1993 the cobalt 
content of metal concentrates produced in Canada was 2 370 tonnes, of which 
approximately 2 000 tonnes were produced in Ontario (NRC 1994, OMNDM 1994). 
Ontario ranked fourth in world cobalt production, accounting for 1 1% of the worid total 
(OMNDM 1994). Zambia was the world's largest producer in 1993 accounting for 25% of 
total production. 

Cobalt is used in various alloys including super-alloys, magnetic alloys (for the 
manufacturing of jet and gas turbines, and stainless steels), dental and surgical alloys 
(CCREM 1987; Shamberger 1979). Cobalt and its salts are also used in cemented 
tungsten carbides, glass and ceramic paints, hygrometers, as catalysts tor organic 
reactions, in electroplating, fertilizers, and as a foam stabilizer in beer (Shamberger 1979; 
Sittig 1985: Windholz et al. 1983). Therapeutically, cobalt or cobalamin (vitamin B12) is 
used in the treatment of cyanide poisoning and as a feed additive to correct deficiency 
symptoms such as anaemia and retarded growth (Bellies 1979). 

Radioactive cobalt-60 is used as an anti-neoplastic gamma ray source. However cobalt-59 
has been found to be a possible (experimental) neoplastlgen and tumorlgen (Sax and 
Lewis 1989; Sittig 1985; Windholz et al. 1983). Radioactive properties of cobalt will not be 
further addressed. 

1.2 AQUATIC SOURCES AND FATE 

Cobalt residence time in the atmosphere is quite short. It is more likely to be found in 
sediments, soils and water. It is estimated that weathering of rock and soils contributes 



between 17 and 20% of the natural global emissions for cobalt, whereas biological action 
by plants contributes 60% (Merian 1984). 

Coal contains on average about 1 mg/kg cobalt, but concentrations can range up to 40 
mg/kg. Combustion of coal is a major anthropogenic source of cobalt to the environment 
{Merian 1984). Other anthropogenic sources include acid coal mine drainage, smeiter 
emissions, raw and treated sewage (0.002-0.04 mg/kg and 0.001 and 0.03 mg/kg, 
respectively), and application and losses of cobaltous sulphate-containing fertilizers (Smith 
and Carson 1981). 

Recent effluent discharge data are available from Ontario's Municipal/Industrial Strategy for 
Abatement (f\/llSA) monitoring reports. Ten sectors (iron and steel, organic chemical 
manufacturing, pulp and paper, metal mining, metal casting, industrial minerals, inorganic 
chemicals, petroleum, waste water treatment plants and hydro-electric generation) were 
required to monitor effluent quality for a one year period (OMOE 1988, 1990, 1991a-f, 
1992b, 1993), Quantification of the total mass (effluent flow X effluent concentration) of 
cobalt discharged to Ontario's surface waters could not be determined reliably because 
many of the data were at or below the regulatory method detection limit (20 pg'L). The 
data suggest that these industries contribute approximately 36 kg of cobalt per day to 
Ontario watersheds. However, intake data suggest that 50-90% of cobalt in the discharge 
was merely entrained by the industry. Significant dischargers of cobalt are the Mining 
Sector and the Municipal Sewage Treatment plants, each contributing approximately 1/3 
of the total discharge. However, recent closures of uranium mines in Ontario have 
reduced mining sector discharge of cobalt by about 25% (Hawley, Pers. comm). 

1.3 AMBIENT CONCENTRATIONS IN ONTARIO WATERS 

Boomer (pers. comm.) reports that the routine OMOEE laboratory detection limit for cobalt 
in surface water is currently 0.5 pg/L using pre-concentrated samples and ICP/MS 
technology. However, there are problems when using this technique with samples 
containing high concentrations of iron. Iron emits photons at a wavelength similar to that 



of cobalt, resulting in interference. This may result in a detection limit 2-3 orders of 
magnitude higher for samples containing high concentrations of iron. In general, OMOEE 
data such as the Provincial Water Quality Monitoring Network (PWQMN) data or the Great 
Lakes Surveillance Data report a detection limit of 1 pg/L. The MISA Regulatory Detection 
Limit (RMDL) for cobalt was 20 pg/L. 

Cobalt concentrations in oxygenated surface waters in Canada range from 1 to 47 pg/L 
(NAQUADAT 1985, as cited in CCREM 1987) and are generally below 20 mg/kg in 
freshwater sediments (Smith and Carson 1981). Background concentrations of cobalt 
were higher in Lake Erie water than in Lake Ontario water, and were the lowest in Lake 
Superior waters. Median values of dissolved, particulate, and total cobalt were 0.089, 
0.005, and 0.096 pg/L, respectively, for Lake Erie; and 0.021, 0.0037, and 0.025 pg/L, 
respectively for Lake Ontario (Rossmann and Barres 1988). 

Monitoring data from the Ontario Ministry of Environment and Energy (OMOEE 1994b) 
suggest that cobalt concentrations are generally beiow the detection limit of 1 pg/L in the 
Great Lakes. For some areas, in particular the St. Clair River, concentrations as high as 
10 pg/L have been reported, but it is unknown whether this is due to natural or 
anthropogenic sources. While effluent data collected under the MISA program from 
organic chemical manufacturing industries along the St. Lawrence River suggest that 
cobalt may be being discharged, OMOEE data (OMOEE 1994b) report all values were 
below 1 pg/L at seven ambient stations along the river. 

Data were also available for Ontario inland waters collected under the Provincial Water 
Quality Monitoring Network (OMOEE 1994c). Most areas monitored had cobalt 
concentrations below the detection limit (1 pg/L), however there are areas that are 
significantly contaminated with cobalt. These areas are generally downstream of mining 
sites, particularly abandoned uranium mines. Waterbodies around Bancroft (NE Ontario), 
including Farrell Creek, Paudash Lake, Deer Creek and Centre Lake contain cobalt 
concentrations of 30 to 50 pg/L. Surface water around Cobalt, Ontario contain similar 
concentrations of cobalt. The Trent River, near Peterborough, had concentrations of 30-40 



pg/L cobalt, although there are no mines in the area. Tailings ponds and waterbodies 
downstream of Bicroft Mine (also in the Bancroft area) contained concentrations ranging 
from 25 to 60 |jg/L, while areas around Balmer Creek (NW Ontario near Red Lal<e) had 
concentrations as high as 80 ng/L. 

The Bicroft mine, and many of the others in the Bancroft area have been abandoned for 
more than 20 years (Hawley, pers. comm.). However PWQMN data suggests that 
leaching from the tailings is still of concern. It should be noted that the highest 
concentrations were found directly in tailings ponds, and waterborne concentrations of 
cobalt decreased steadily downstream due to dilution and/or sorption to sediments. 

Ambient cobalt concentrations in the suspended solids of the Niagara River and the 
sediments of Lake Ontario (Niagara Basin) were 0.021 and 0.017 mg/kg. respectively 
(Thomas 1983). 

Deloro, in southwestern Ontario (about 60 km NE of Peterborough) is the site of an 
abandoned gold mining and refining site, which has a long history of metal contamination 
(Azcue and Nriagu 1993). Cobalt, mined in Cobalt. ON or imported from outside the 
province, was brought to the site for refining. Tailings contained high concentrations of 
cobalt which leach into the Moira River. Although the refinery was closed in the 1960's, 
and a tailings treatment plant has been built on-site, elevated concentrations of cobalt are 
still detected in the Moira River. Just downstream of the Deloro site, levels of cobalt 
ranging from 1 to 20 pg/L were detected. Cobalt concentrations in samples collected 
further downstream ranged from 1 to 10 ^ig/L, while at the mouth of the river (near 
Belleville) levels were below the detection limit (OMOEE 1994c). Mudroch and 
Capobianco (1979) correlated cobalt concentrations in surface sediments to those in 
submerged macrophytes of the Moira River drainage basin. For samples collected at the 
same site, cobalt concentrations in surface sediments and in the macrophytes 
Myriophyllum verticillatum and Elodea canadensis were 864, 262.5 and 10 pg/g dry weight, 
respectively (Mudroch and Capobianco 1979). 



1.4 AQUATIC CHEMISTRY 

Cobalt metal (molecular weight 58.9) has a melting point of 1 493 °C and a boiling point of 
3 100 °C, and is stable in air and water at standard temperatures (Sax and Lewis 1989; 
Windholz et al. 1983). There are six oxidation states for cobalt -1, 0, +1, +2, +3, and +4. 
In general the common valence of cobalt is +2 (cobaltous ion), except in coordination 
complexes where the +3 (cobaltic ion) predominates (Shamberger 1979). 

In aqueous solution the cobaltous ion (Co II) is stable but the uncomplexed cobaltic ion 
(Co III) is a strong oxidizing agent (Trisdan et al. 1981). Based on simulations using the 
MINEQL-1 model, cobalt metal should exist mainly as aquo ions (i.e. as an ion containing 
water molecules) over a pH range of 4 to 7 (Campbell et al. 1982; Campbell and Stokes 
1985). 

ASTDR (1991) reports that in most freshwaters, less than 2% of cobalt species are present 
in the dissolved state, most cobalt is precipitated or adsorbed on suspended solids or 
sediments. However, the data from Rossmann and Barres (1988) Lakes Erie and Ontario 
does not indicate the same ratio, with cobalt existing almost entirely in the dissolved state 
in Lake Erie and existing in about equal proportions in Lake Ontario. Nriagu and Coker 
(1980) determined that only 2-5% of cobalt was associated with humic acids in Lake 
Ontario sediments. Illite clay suspensions (1 g/L), adsorbed 95% of cobalt at pH 8 and 
40% at pH 4 at concentrations from 50 to 200 pg/L (O'Connor and Kester 1 975 as cited in 
CCREM 1987). Adsorption of cobalt to clay minerals was found to increase with increasing 
pH (Carson 1981; Murray and Murray 1973). In most waiers, the sediment is the primary 
repository site of cobalt. Some mobilization may occur in acidic waters, in the presence of 
excess chloride ions or chelating agents. Chelation of cobalt with ligands such as EDTA, 
increases its solubility and mobility in the aquatic environment (CCREM 1987). 



2.0 TOXICITY TO AQUATIC ORGANISMS 

All candidate toxicological information is screened for acceptability. All information that 
meets the following requirements is considered primary data: 

• Toxicity tests must employ accepted laboratory practices of exposure and 
environmental controls. While all tests must be evaluated on a case by case basis, 
those tests following published protocols of government agencies or standard 
setting associations are generally acceptable. 

• Any tests may be acceptable, including static tests if it can be shown \ha\ con- 
centrations of the toxicant are not changing (significantly) throughout the test and 
adequate environmental conditions for the test species are maintained with respect 
to such factors as dissolved oxygen and removal of metabolic wastes. Generally, 
continuous flow exposures, and renewal tests (i e. static tests with replacement) are 
acceptable if appropriate rates of renewal of toxicant are maintained. Static tests 
are acceptable if concentrations of the toxicant are measured in the exposure 
vessel at the beginning and end of the test and no more than 10% of the toxicant is 
lost during the test. The use of chemical carriers is acceptable as long as the 
concentration of the toxicant does not exceed water solubility in the absence of the 
carrier. Appropriate chemical carrier controls must also be included. 

• Dissolved concentrations of toxicant in the exposure vessels must be constant and 
verified by measurements rather than calculated or measured only in stock 
solutions. Tests will generally be considered unacceptable if more than 10% of the 
toxicant is lost during the test. 

• Test end points and lengths of exposure must be appropriate to the life stage of the 
species tested and the characteristics of the substance. Although the definitive 
bench mark for chronic toxicity is a whole life cycle test, partial life cycle and short 
term or early life stage tests are acceptable as chronic data. 



• Relevant environmental parameters such as temperature, pH and hardness must 
have been recorded. 

• Responses and survival of controls must be appropriate tor the species and test 
used. 

Data on vertebrates and invertebrates not meeting all of the above are denoted as 
secondary in objective development documents. Secondary data are inadmissible in the 
derivation of an Objective but are admissible in deriving an Interim Objective. Most tests 
using aquatic plants w/ill also be classified as secondary due to the frequent use of artificial 
media or a lacl< of standardized protocols; however, plant data may be used as the critical 
endpoint for Objective development subject to best scientific judgement. 

Toxicity data, current to February 1995, are summarized in Table 2. These data were 
critically reviewed and classified as primary, secondary or ancillary data based on the 
laboratory practices of the researchers. A more detailed explanation of the classification 
procedure is outlined in "Ontario's Objective Development Process" {OMOE 1992a). 

2.1 ACUTE TOXICITY 

2.1.1 Vertebrates 

There were two primary studies with vertebrates, both using fathead minnows {Pimephales 
promelas). Additionally, there were four secondary studies on two fish species and one 
frog species. 

Diamond et al. (1992) reported hardness-dependent 48h-NOECs (No Observable Effect 
Concentrations) for fathead minnows of 1.2, 7.3, 13.7 and 6.2 mg/L for hardnesses of 50, 
200, 400 and 800 mg/l CaCOg, respectively. These tests were done under static 
conditions with daily renewals. The authors reported that LC50 values for fathead minnow 
tests could not be calculated due to the unexpectedly low sensitivity of this species to high 
cobalt concentrations (^ 5 mg/L) over the 48h exposure period. Kimball (undated MS), 

8 



however, reported a 96h-LC50 of 3.61 mg/L, also using fathead minnows These tests 
were done under flow-through conditions with a 5.8h turn-over time. It is unknown why 
Kimball (undated MS) was able to derive a result with concentrations less than 5 mg/L, 
while Diamond et al. (1992) was not. The longer exposure time may be the main reason, 
since Kimball (undated MS) also reported a 192h-LC50 of 2.74 mg/L under the same 
conditions, suggesting exposure periods have a significant effect on toxicity. These data 
were considered primary as they employed good laboratory practices using measured 
toxicant concentrations. 

Secondary acute toxicity data were available for giant gouramis (Colisa fasciatus), fathead 
minnows, and african clawed frogs (Xenopus laevis). 96h-LC50 values ranged from 22 to 
13 500 mg/L (Srivastava and Agrawal 1979; Ewell ef al. 1986; Curtis and Ward 1981; 
Sunderman 1992). Frogs exposed to a cobalt concentration of 5.453 mg/L exhibited 
decreased growth and an exposure to a concentration of 0.325 mg/L resulted in 50% 
embryo abnormalities after 96h, suggesting that sub-lethal effects may result at lower 
concentrations than those needed for lethal effects (Sunderman 1992). The original paper 
for this study could not be obtained, thus it was ranked as secondary. 

Srivastava and Agrawal (1979) reported a 96-h LC50 of 225 mg/L of cobalt chloride for the 
freshwater teleost, Colisa fasciatus. Although the LC50 was based on the salt, they did 
not state whether it was anhydrous or hexahydrate. The conversions of the LC50, 
assuming the salt used to be anhydrous or hexahydrate, results in 96h-LC50 values of 

102.1 mg Co^VL or 55.7 mg Co'VL respectively. In addition to the 96-h LC50, Srivastava 
and Agrawal (1979) reported that a 90-h exposure of the fish to a sublethal concentration 
of 195 mg/L cobalt chloride salt caused a decrease in blood clotting time, an increase in 
circulating thrombocytes, and leucopenia. 

2.1.2 Invertebrates 

There were three primary studies with three species of freshwater invertebrates (two 
crayfish species and one daphnid). Secondary data were available for eleven species. 

9 



Most data were EC50s with exposure times varying from 24 to 96h. Acute toxicity values 
ranged from about 1 mg/L to 500 mg/L. Daphnids appear the most sensitive invertebrate 
to cobalt, while Tubifex appear to be the most tolerant. 

Biesinger and Christensen (1972) reported 48-h EC50 values for Daphnia magna of 1.62 
mg/L and 1.11 mg/L, with and without food, respectively. It appears that either the toxicity 
of cobaitous chloride hexahydrate was reduced in the presence of added food, or toxicity 
was enhanced in unfed organisms due to the stress of starvation. Khangarot et al. (1987) 
reported two 24-h EC50s and two 48-h EC50s by applying different statistical methods to 
the same raw data for Daphnia magna. The 24-h EC50s were 2.11 mg/L and 2.61 mg/L 
with cobaitous chloride hexahydrate as the toxicant. The 48-h EC50s were 1 .52 mg/L and 
1.49 mg/L (Khangarot et al. 1987). Baudouin and Scoppa (1974) reported a 48-h EC50 
value of 1 .32 mg/L for D. hyalina using hexahydrated cobaitous chloride salt as the 
toxicant. 

Kimball (undated MS) conducted replicated acute tests with D. magna. Tests used 
neonates <24-h old and were static, lasting either 48 h with and without feeding, or 96 h 
only if fed This experiment involved measured toxicant conditions and was considered 
primary. Feeding decreased the toxicity of cobalt at 48h. The 48h-EC50s of cobalt were 
7.37 and 5.99 mg/L for daphnids that were fed and not fed, respectively. It is not clear 
however if the effect was due to increased stamina of the Daphnia or interference with the 
toxic action. 

Diamond et al. (1992) reported 48h-EC50s for D. magna at four water hardness levels. 
Reported values were 2.3, 4.6, 4.2 and >5.3 mg/L at hardness values of approximately 55, 
255, 475, and 880 mg/L as CaC03, respectively. This experiment was considered primary. 
The data suggests that toxicity is inversely proportional to water hardness. 

Boutet and Chaisemartin (1973) reported 96h-LC50s of 8.8 mg/L and 10.2 mg/L. for two 
species of crayfish, Austropotamobius pallipes paliipes and Orconectes limosus, 
respectively. Both of these studies used measured toxicant concentrations and were 

10 



considered primary. In most cases, invertebrate studies lasting more than 48h are 
considered chronic. However, crayfish life cycles tend to be longer in duration and a single 
life stage may last for longer than 96h. Thus, these 96h experiments were considered to 
be acute. 

2.2 CHRONIC TOXICITY 

2.2.1 Vertebrates 

Three primary chronic studies using four species of vertebrates were found (Birge 1978, 
Kimball undated f^S, Diamond et al. 1992). In addition, two studies were classified as 
secondary. Toxicity values for cobalt ranged from 0.05 mg/L for a 7d-LC50 for the 
narrowmouth toad (Gastrophryne carolinensis) to 15 mg/L resulting in haematological 
changes in tilapia {Sarotheradon mossambicus). 

BIrge (1978) obtained a 28-d LC50 of 0.47 mg/L for rainbow trout embryos. For goldfish 
{Carassius auratus) and the narrow mouthed toad, the 7-d LC50 values were 0.81 mg/L 
and 0.05 mg/L, respectively (Birge 1978). 

Chronic toxicity of cobalt to fathead minnows was tested by Kimball (undated MS) starting 
with eggs <40-h old and lasting until 28 days post hatch. At 1.61 mg/L there was a small 
decrease in hatch success, however all fry were reported to have developmental 
abnormalities. Only 23% of fathead minnows survived for 28d at 1.61 mg/L. Weight gain 
was a more sensitive endpoint however, and fish exposed to 0.81 mg/L gained significantly 
less weight than controls. Kimball (undated MS) reported that cobalt ranked fourth of 
seven metals tested on fathead minnows for growth inhibition. 

Jones (1939a) reported a 10-d NOEC of 10 mg/L for the stickleback Gasterosteus 
aculeatus with cobaltous nitrate as the toxicant. The author observed that cobaltous 
nitrate and several other salts of metals such as silver, precipitated with the mucus 
secreted by the fish. Noticing an increase in the frequency and amplitude of respiratory 
movements. Jones (1939a) postulated that this compensatory reaction was not adequate 

11 



to overcome impairment ot respiratory function due to the physical clogging of the gill 
filaments by the precipitates, thus resulting in death by asphyxiation. 

Diamond et al. (1992) examined the effects of hardness on survival and growth of fathead 
minnows over seven days. While the data suggest that increasing hardness may decrease 
chronic cobalt toxicity, the authors felt that there were too few chronic data available to 
determine a definite relationship between cobalt toxicity and water hardness. 

2.2.2 Invertebrates 

Four primary chronic studies with three species of invertebrates were found. An additional 
twelve secondary chronic studies were also identified. Toxicity values of cobalt ranged 
from a low of 0.00016 mg/L causing terata in snail embryos to 139,32 mg/L for a 96h-LC50 
for tubificids. Chronic studies investigate many types of toxic effects, both lethal and 
sublethal, over a wide range of exposure times and it is not surprising that there is such a 
large range of toxicity values. 

Diamond et al. (1992) examined the effects of hardness on D. magna using 7-d sun/ival 
and reproduction expehments. The auttiors reported that a number of experimental 
problems caused difficulty in analyzing the results, and they reported that NOECs could 
only be calculated for one hardness level (400 mg/L as CaC03) which was reported as <50 
|jg/L. The authors do report, however, that their experiments suggest a hardness 
dependant relationship for cobalt toxicity. 

Boutet and Chaisemartin (1973) determined the 30-d LC50 for two species of crayfish, with 
and without food. For A. pallipes pallipes the 30-d LC50 was 0.77 mg/L with food, and 
0.79 mg/L without food. Similarly, the 30-d LC50 for O. limosus was 0.79 mg/L with food, 
and 0.88 mg/L without. Thus, the addition of food had little effect on the toxicity of cobalt 
as cobaltous chloride hexahydrate. 



12 



Biesinger and Christensen (1972) exposed D. magna to cobalt chloride hexahydrate for 3 
weeks and reported the LC50 and sublethal effects. The 21 -d LC50 was 0.021 mg/L, 
while a concentration of 0.024 mg/L caused a 15% reduction in weight as well as 12% and 
45% increases in protein and glutannic oxalacetic transanninase (GOT), respectively. 
These physiological responses occurred at Co^' levels greater than the LC50. 
Reproduction was impaired by 16% and 50% at cobalt concentrations of 0.010 mg/L and 
0.012 mg/L, respectively (Biesinger and Christensen 1972). Kaiser (1980) was able to 
accurately predict the 16% reproductive impairment concentration given by Biesinger and 
Christensen (1972), using an equation that incorporated ion-specific physical-chemical 
properties {e.g., ionization potential and oxidation state). 

Chronic toxicity of cobalt to D. magna was tested by Kimball (undated MS). Tests were 
static with replacement and measured survival and several indices of reproductive success. 
The 28-d LC50 was 0.027 mg/L Co, almost identical to that of Biesinger and Christensen 
(1972). Kimball (undated f\/IS) reported that tests using Daphnia reproduction as the 
endpoint were much more sensitive than those using lethality. The lowest concentration of 
cobalt which significantly decreased reproduction (as mean young per female) was 0.009 
mg/L. Kimball (undated MS) also compared the sensitivity of Daphnia and fathead 
minnows to nine metals (V, Be, Tl, Co, Sb, Mn, Al, Mo and Be). For most metals, the 
toxicity was similar for both organisms although the order of sensitivity changed somewhat. 
In the case of cobalt however, Daphnia were nearly 60 times more sensitive than fathead 
minnow. Compared to the toxicity of other metals, cobalt ranked fifth of the nine metals 
tested on daphnids. 

Sodergren (1976) reported a 96-h LC50 of 33 mg/L for the nymph of damselflies 
{Ephemerella mucronata) exposed to cobalt nitrate. Cobalt toxicity was tested on E. ignita 
nymphs in the presence of a food source Fontinalis dalecarlica. A four week exposure to 
0.0326 mg/L of cobalt nitrate resulted in reduced growth (Sodergren 1976). A possible 
explanation for the higher toxicity to E. ignita. presented by Sodergren (1976), is that the 
nymphs received a greater dose of cobalt by consuming F. dalecarlica, which accumulates 



13 



cobalt. However, the observed toxicity may simply be a function of the longer exposure 
period. These data were considered secondary. 

A solution of cobaltous chloride at 10 mg/L of Co^*. was found to completely inhibit nuclear 
expansion in the chloragocytes of Tubifex tubifex under hypoxic conditions (Fischer et al. 
1980). Under aerobic conditions cobalt had neither a stimulatory nor an inhibitory effect on 
nuclear expansion. The authors surmise that since cobalt is an effective inhibitor of haem 
synthesis and possibly an inhibitor of globin synthesis, the depression of nuclear expansion 
may be the result of cobalt's inhibitory effect on haemoprotein synthesis. 

The probit-derived 96-h EC50 estimate for the rotifer, Phllodina acuticornis, exposed to 
cobalt chloride was 27.8 mg/L with an endpoint criterion of no visible internal or external 
motion (Buikema et al. 1974). Hardness of the water had little effect on cobalt toxicity in 
this study. 

Solski and Piontek (1987, in AQUIRE) reports planaria exposed to 0.002 to 0.028 mg/L 
cobalt for 10 days showed a change in the ability to regenerate. This paper could not be 
obtained and critically reviewed, and thus could not be used for criteria development. 

Based on 96h-EC50 studies with T. tubifex, Khangarot (1991) found that cobalt ranked 
24th of 32 elements tested. Cobalt was found to be twice as toxic to Tubifex than 
magnesium, calcium and sodium, but at concentrations significantly less toxic than metals 
such as lead, mercury or cadmium. 

2.2.3 Other Organis ms (Algae. Protists etc. l 

According to the Objective Development Process (Of^OE 1992a), tests employing algae 
are always classified as secondary data due to inherent difficulties in performing algal 
expenments. 



14 



Toxicity studies were available for seven species of algae and two protists. Toxicity values 
ranged from 0.1 mg/L to 50 mg/L for algae, while 3h-HTC (highest concentration where 
protists were still observed alive after three hours) ranged from 1 000 to 2 500 mg/L. 

Cobalt toxicity to algae was in the same order of magnitude as that of copper and nickel 
(den Dooren de Jong 1965). For Chlorella vulgaris, the growth inhibition NOEC and LOEC 
(lowest observed effect concentration) values were 0.226 mg/L and 0.442 mg/L Co'* as 
cobalt chloride hexahydrate, respectively (den Dooren de Jong 1965). Hutchinson (1973) 
reported 99% growth inhibition of this same species at 1.0 mg/L. For the more tolerant 
species Haematococcus capensis, growth was inhibited by 80% at 5.0 mg/L (Hutchinson 
1973). A more sensitive species was Chlamydomonas eugametos. which had 100% 
growth inhibition at 0.5 mg/L (Hutchinson 1973). Other toxicity tests with algae showed 
that concentrations of cobalt chloride between 2 and 9 mg/L Co^' were toxic to Anabaena 
variabilis, whereas, concentrations between 20 and 50 mg/L were toxic to C. vulgaris 
(Ahluwalia and Kaur 1988). Stokes (1981) reported EC50 values of 0.25 mg/L for 
Scenedesmus acutiformis f. alternans and 0.1 mg/L for S. acuminatus. Sharma et al. 
(1987) found Spirulina plater)Sls to be less sensitive to cobalt than other algae, with a 96-h 
EC50 of 23.8 mg/L. The endpoint cnterion in this study was dry weight biomass as a 
function of optical density at 490 nm and sublethal concentrations (0.1 and 0.5 mg/L) 
resulted in an increase in biomass, which was ascribed to a hermetic effect. 

2.3 SUMMARY OF TOXICITY DATA 

Insufficient data prohibits comparison of the relative toxicities of the various forms of cobalt 
to aquatic biota. 

In general, acutely toxic concentrations from primary references indicated effects in the 1 
to 10 mg/L range, except when organisms are exposed in very hard water, while 
secondary values were as high as 450 mg/L. Toxicity values fall within the same range for 
both vertebrates and invertebrates, however there are too few acute vertebrate studies for 
accurate comparison. Chronic toxic concentrations of cobalt from primary references 

15 



suggest that effects are likely to occur in the range of 0.009 to 2 mg/L, while secondary 
studies ranged from 0.0016 to 2 500 mg/L. In general, chronic data tend to vary more 
widely than acute data due to the wide range of exposure times and types of endpoints 
examined. Primary data suggest that invertebrates may be more sensitive to cobalt than 
vertebrates under chronic exposures. Kimball (undated MS) reported that Daphnia are 
more sensitive to cobalt than fathead minnows when exposed for 96h, however the extent 
of the difference is not very large. Data compahng growth of fathead embryos and 
Daphnia survival and reproduction suggested that Daphnia were approximately 60 times 
more sensitive to cobalt than are fathead minnows (Kimball undated MS). 

Khangarot and Ray (1989) summarized how cobalt toxicity compared to the toxicity of 
other metals tested on various aquatic species (Table 1). Cobalt tends to be slightly to 
moderately toxic, however some species appear to be especially sensitive. Kimball 
(undated MS) found that Daphnia magna were more sensitive to cobalt than many other 
minor inorganics {e.g.. beryllium, selenium, thallium etc.). However, this study did not 
expose organisms to metals such as mercury, cadmium or lead, that other experiments 
have shown to be much more toxic. For example, Khangarot and Ray (1989) found that 
cobalt was approximately 1000 times less toxic than mercury. Birge (1978) ranked cobalt 
in an arbitrarily determined, Toxicity Group 1 , based on toxicity studies with toads, goldfish 
and rainbow trout. This category included more toxic metals such as silver, mercury, and 
cadmium. 



16 



Tabic I: Toxicily ranking cil aibalt coinparcd lo oihcr metals (modified from Khangarnt ami Ray 1989) 



.Species Tested 


Eiidpoint 


Cobalt 

Ranking 


# of Metals 
Tested 


Reference 


Clitorclla viili;ans 


l:C50 


8 


y 


Sakaguchi ei at. (1977) 


Paramecium 


I.C50 


7 


9 


Shaw (19.'i4) 


Folyccin nigra 


LC50 


7 


16 


Jones (1939b) 


Daphniu maiina 


48liT,(:S0 


5 


23 


Khangaroi k Ray (1989) 


Dapknia magna 


481vLC50 


5 


9 


Kimball (undated MS) 


Duphiiia magna 


2Sd LC5() 


1 


9 


Kimball (undateii MS) 


Daplmia magna 


28d-repi()diicIi(Tn 


1 


9 


Kimball (undated MS) 


Daphnia magna 


6)liT-C50 


8 


19 


Anderson (1948) 


Daphnia magna 


48h-EC.50 


fi 


15 


Biesinger and Christensen 
(1972) 


Daphnia hyalina 


48hT;C?() 


-J 
/ 


12 


Badouin and Scoppa (1974) 


Cyclops ahyssfriim 
prealpins 


4Sh [■rso 


K 


12 


[ladoijiii and Scop[)a (1974) 


Tiihijex luhiJL'x 


WhT-X'.'SO 


24 


32 


Khangaroi (1991) 


Cypris siibgUihnsa 


48h-IZC5() 


II 


28 


Khangarot and Ray 
(unpublished 1 


Li'hisU's reliciilalti^ 


LDSO 


s 


9 


Shaw and Grushkin (1957) 


Gasierosteiis aculcatu}, 


1 C'SO 


1 1 


18 


Jones (1939a) 


runephak'.i promclas 


i'J2iiTx:'.'s() 


4 


8 


Kimball (undated MS) 


Pimephaies pramelas 


2Kd-survival 


4 


7 


Kimball (undated MS) 


Guitruphrynt' curolinensis 


7d-LC5() 


II 


■)-> 


Birgc (1978) 


Rana hcxaJaccyia 


')()hT_C?() 


7 


9 


Khangaroi et at. ( 1982) 


Bufa vallireps 


LD50 


7 


9 


Shaw and Gnishkin (1957) 



2.4 EFFECTS OF WATER QUAUTY PARAMETERS ON TOXICITY 

Diamond et al. (1992) reported that water hardness had a significant effect on the 
toxicity of cobalt. Their studies showed that in the hardness range of 50 to 200 mg/L 
as CaC03, acute cobalt toxicity to both fish and invertebrates may be inversely 



17 



related to hardness. Toxicity of cobalt to fathead minnows appeared to increase at the 
highest hardness tested, however the authors state that toxicity may have been a 
result of the extreme hardness rather than cobalt toxicity. Diamond et al. (1992) 
suggested that it is possible that Ca^' and Mg^' compete with cobalt for potential target 
sites of toxic actions. Cobalt has a higher density and higher ionization potential than 
these ions and thus cobalt adsorption on cell membranes may not be a stable 
phenomenon given an abundance of more reactive cations available. This paper only 
reported NOECs for fathead minnow, instead of effect concentrations. As such, it is 
difficult to assess the true effects of hardness due to the possibility that toxic effects 
may not occur In proportion to the respective NOECs. Buikema et al. (1984) was the 
only other study that Investigated hardness effects on cobalt toxicity. They reported 
that hardness had little effect on cobalt toxicity to rotifers over 96 hours. 

3.Q BIQACCUMULATION 

Cobalt may bioaccumulate in freshwater plants and invertebrates but does not 
accumulate in fish tissues. Although freshwater algae can have cobalt concentrations 
of 400 to 2x10*^ times the ambient levels, it is uncertain to whether this is due to actual 
biological uptake or to physical adsorption (Cole and Carson 1981). Bioconcentration 
factors range from 100-14 000 for freshwater molluscs; up to 10^ for Insect larvae; and 
from 1-11 000 for other Invertebrates (Cole and Carson 1981). Various species of fish 
sampled had cobalt concentrations ranging from 0.23 pg/g (fresh weight) to 4.7 pg/g In 
Lake Erie; 0.16 pg/g to 1.1 pg/g in Lake Ontario; and 0.04 pg/g to 0.33 pg/g in the St. 
Lawrence (Tong et al. 1972). The cobalt concentrations in lake trout {Salvelinus 
namaycush) which averaged 0.0599 pg/g (fresh weight), were found not to vary 
significantly with fish up to 12 years (Tong et al. 1974), suggesting that it does not 
biomagnify. ASTDR (1991) reports that benthic bottom feeding fish do not appear to 
significantly bioaccumulate cobalt from contaminated sediment. 



Baudin and Fritsch (1989) examined the related contribution of food and water in the 
accumulation of cobalt in fish. Carp fed Co^-contaminated snails were found to 
accumulate Co only slightly. The authors report a trophic transfer rate (transfer of 
contaminant residues from lower to higher trophic levels) of about 10^. Furthermore, 
the fish were found to depurate cobalt, resulting in a retention factor of only 3x10'^ 
after 63 days. Fish exposed to waterborne cobalt had uptakes significantly higher 
than those exposed through food, while fish exposed through both water and food had 
the highest uptake. The authors concluded that water is the primary route of cobalt 
uptake in carp and that accumulation from both food and water was additive. 

4.0 IMPACT ON TASTE AND ODOUR OF WATER AND FISH TAINTING 

in water cobaltous bromide has a slight odour and cobaltous chloride has a slight 
sharp odour: cobaltous nitrate and sulfate are odourless (Weiss 1986). 
Concentrations at which these odours were detectable were not given Organoleptic 
data were not available for tainting of fish flesh. 

5.0 MUTAGENICITY 

A review of summary documents was undertaken to examine the likelihood of cobalt 
causing mutagenic effects (ASTDR 1991, Smith and Carson 1981, IRIS 1994). A 
recent special issue of the journal, "The Science of the Total Environment" (Volume 
150, 1994) contained a number of papers on the toxicity, mutagenicity and 
environmental fate of cobalt. 

ASTDR (1991) reported that no studies were found describing genotoxic effects on 
humans or animals through inhalation, oral or dennal exposure to cobalt. It was 
reported that cobalt (II) was found to be generally non-mutagenic in bacteria and 
yeast, while cobalt (III) garnered positive mutagenic responses in Salmonella 
typhimurium and Escherichia coli. Further information suggested that cobalt was 

19 



genotoxic in in vitro experiments, causing genetic conversions in S. cerevisae. 
clastogenic effects on mammalian cells, transformations in hamster cells and sister 
chromatid exchanges in human lymphocytes. Sharma and Talukder (1987) report that 
cobalt exerts very strong mutagenic effects on plant activity. When compared to other 
inorganics, cobalt was found to be less toxic than arsenic and selenium, yet more 
toxic than lead, zinc or cadmium based on clastogenic tests with onion root tips 
{Allium sp). Effects reported include chromosome breaks, diplochromatids, erosion, 
fragmentation and bridges. Cobalt salts reduced the rate of cell division, inhibited 
passage of interphase into prophase and produced clumping and stickiness of 
chromosomes in Vicia sp. 

Nordberg (1994) reported that there was sufficient evidence of carcinogenicity for 
cobalt (II) oxide, limited evidence of carcinogenicity for cobalt (II) sulphide and cobalt 
(II) chloride, and inadequate evidence of carcinogenicity for cobalt aluminum spinel, 
cobalt (II. Ill) oxide, cobalt naphtenate and cobalt (III) acetate in animals. 

ASTDR (1991) reported that cobalt has not been shown to cause cancer in humans 
by any exposure route. However, lARC (International Agency for Research on 
Cancer) recently classified cobalt and cobalt compounds as possible human 
carcinogens (Group B). This classification was based on limited evidence in humans, 
and data from studies that concluded that soluble cobalt (II) compounds are genotoxic 
to various organisms (Binderup and Wassermann 1994). 

There is evidence that suggests that cobalt is teratogenic in mammalian systems 
(ASTDR 1991). There is some indication that cobalt may cause terata in aquatic 
invertebrates. Jaroensastraraks and McLaughlin (1974 as cited in Herndon et al.) 
reported that eggs of the freshwater snail, Helisoma, treated with 1 mg/L of cobalt had 
deformities of the shell and gut. Another study (Morrill 1963, in Herndon et al. 1981) 
reported that concentrations as low as 0.16 pg/L caused abnormalities in the shell and 
feet of gastropods. This study, could not be critically reviewed for this document, and 

20 



was not used in objective derivation. Data by Sundemnan (1992) suggested that low 
concentrations of cobalt (30 mg/L) may cause abnormalities in Xenopus, however this 
paper could not be obtained. 

In summary, available information suggests that cobalt may exert genotoxic effects, 
with cobalt (111) likely exhibiting the most significant mutagenic effects. Recent 
evidence suggests that cobalt may cause cancer, and may result in terata in some 
organisms, including aquatic invertebrates. 

6.0 DERIVATION OF THE PROVINCIAL WATER QUAUTY OBJECTIVE 

6.1 TOXICOLOGICAL DATA 

For a PWQO to be developed, certain information requirements must be met (OMOE 
1992a). These are summarized in Table 3. All requirements for developing a PWQO 
could be met with the existing data, except for a mutagenicity assessment. While 
cobalt has been shown to be mutagenic in lab animals, no primary data was available 
for aquatic organisms. Until sufficient mutagenicity information becomes available, a 
PWQO based solely on aquatic toxicity will be developed. It should be noted that this 
value may not protect against mutagenic effects. 

While there is evidence suggesting that cobalt toxicity is affected by water hardness, 
there is insufficient toxicity data to allow development of a hardness-based PWQO. 
Thus, the most conservative approach will be taken and the PWQO will be set as a 
single value. 

The lowest effect concentration of cobalt was 0.009 mg/L; based on a 28d LOEC 
(reproduction) for D. magna (Kimball undated MS). The initial safety factor of 10 
(OMOE 1992a) was applied to this value to derive a preliminary PWQO of 0.0009 
mg/L (0.9 pg/L) for the protection of aquatic life. 



21 



6.2 BIOACCUMULATION 

Cobalt does not appear to bioaccumulate in fish. Thus, for the purposes of criterion 
development, bioaccumulation of cobalt was not considered significant. Therefore 
bioaccumulation will not affect the preliminary PWQO calculated from toxicity data. 

6.3 MUTAGENICITY 

There were few studies available which examined mutagenic effects on aquatic 
organisms. However, these data were from secondary literature sources and could 
not be properly reviewed. Data for mammalian systems indicates that cobalt may 
exert genotoxic effects, with cobalt (III) likely exhibiting the most significant mutagenic 
effects. Recent evidence suggests that cobalt may cause cancer, and may result in 
terata in some organisms. Therefore, the PWQO based on aquatic toxicity may not 
protect against these effects. 

6.4 TASTE AND ODOUR 

There was no information in the literature that indicates that cobalt would affect the 
taste and odour of water. In fact there is evidence to the contrary, it is tasteless and 
odourless. 

6.5 OTHER EFFECTS 

There is no evidence to suggest that the PWQO should be lowered to protect 
piscivorous wildlife. 



22 



6.6 DERMAL EFFECTS 

The scant data available regarding dermal absorption of cobalt suggest that there 
should be no detrimental effects on humans exposed to environmental concentrations 
of cobalt while engaging in water based recreational activities (e.g. swimming). 

ASTDR (1991) reported that no studies were found regarding lethal or significant non- 
lethal effects on humans after dermal exposure to cobalt, nor were any studies 
investigating rates of dermal absorption in humans found. Christie et al. (1976 in 
Herndon et al. 1981) found that cobalt poorly penetrated normal skin but may 
penetrate damaged skin more quickly. Herndon et al. (1981) reported that intermittent 
dermal exposure to a 0.5 to 2.5% Co(N03)2 solution over periods ranging from 1 week 
to 35 years resulted in dermatitis and eczema. There have been reports of some 
people with severe dermal hypersensitivity to cobalt. Concentrations as low as 0.27% 
cobalt chloride in distilled water have elicited an effect. 

6.7 OMOEE LABORATORY DETECTION LIMITS 

Boomer (pers. comm.) reported that the routine OMOEE laboratory detection limit for 
cobalt in surface water is currently about 0.5 pg/L using pre-concentrated samples and 
ICP/MS technology. This value is lower than the proposed PWQO of 0.9 pg/L. 
However, there are problems when using this technique with samples containing high 
concentrations of iron, which may result in laboratory detection limits 2 to 3 orders of 
magnitude higher. Hence, in some instances, the PWQO may be below the detection 
limit. 

6.8 CONCLUSION 

In summary, the recommended PWQO for total cobalt is 0.0009 mg/L based on 
aquatic toxicity 

23 



7.0 RESEARCH NEEDS 

Primary chronic and acute toxicity tests with vertebrates, especially coldwater North 
American species are required to provide a more comprehensive data base. Although 
there is fairly good breadth in the variety of species tested, there is very little depth in 
terms of several tests on important species. In general, experimental procedure in the 
future should include: 

1 . reporting the effect concentration in terms of mg metal ion/L instead of 
leaving it ambiguous and incomparable with other data. This is 
especially important for cobalt which has significant differences in 
molecular weight for hydrated and anhydrous salts, making conversions 
from mg/L salt to mg/L metal ion impossible if the specific form of salt 
used is not indicated. 

2. studies on the toxic species and effects of water quality variables such 
as pH and hardness. 

3. since there is evidence suggesting cobalt may have mutagenic 
properties, further investigations of these properties on aquatic organisms 
are needed. 

4. since the data from Kimball (undated) was never published, similar 
experiments should be performed to assess the validity of the data. 

5. The paper by Solski and Piontek (1987) reporting toxicity to Dugesia at 
very low concentrations of cobalt should be obtained and assessed. 

6. The two papers examining the mutagenicity of cobalt (Morrill 1963. 
Sunderman 1992) should be obtained and assessed. 

24 



8.0 OBJECT I VES OF OTH E R AGE N CIES 

There is no national Canadian cobalt guideline for the protection of freshwater aquatic 
life (CCREM 1987). There are however guidelines for livestock watering and irrigation 
water of 1.0 mg/L and 0.05 nng/L, respectively, for total cobalt (CCREf^ 1987). The 
U.S. EPA (1987) has a permissible ambient goal of 0.7 mg/L based on human health 
effects (Sittig 1985). A limit of 1.0 mg/L for cobalt in drinking water has been set in 
the U.S.S.R. (Sittig 1985). The New York State ambient water quality standard for 
cobalt of 5 |jg/L in surface water is based on chronic reproductive toxicity to aquatic 
life (NYSDEC 1986). 



25 



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Table 3 : Data Requirements for 
Provincial Water Quality Objectives 

1. Toxicity 

All data must be primary or chronic: marine or brackish 
species are not permitted. 

FISH 

At Least: 



One coldwater species - Rainbow trout (Birge 1978) 



One warmwater species - Fathead minnow (Diamond et al 
1992) 



One other warmwater or coldwater species - Toad (Birge 
1978) 





With at least : 


X 


One species resident in Ontario (may be one of above) 
Rainbow trout (Birge 19 78) 


X 


One early lifestage endpoint - 9d-ELS for fathead minnows 
(Diamond et al . 1992) 


X 


one other whole oi"ganisms chronic endpoint - 28d-LC50 for 
rainbow trout (Birge 1978) 



INVERTEBRATES 

At Least : 



one crustacean - Daphnia magna (Diamond et al . 1992) 



One other order - Crayfish (Boutet & Chaisemartin 1973) 





With at Least: 


X 


no more than one tropical species 


X 


one early lifestage endpoint - 7d-L0EC (reproduction of 
Daphnia as # of young per female) (Diamond et al . 1992) 


X 


one other chronic endpoint - 30d-LC50 with crayfish 
(Boutet & Chaisemartin 1973) 



40 



ALGAE /AQUATIC PLANT 



one algae or aquatic plant resident in temperate North 
America using scientific procedures and test conditions 
compatible with recognized algal bioassays - Green algae 
{Coleman et aJ . 1971) 



Bioaccumulation 

One of : 





Fish consumption limit {e.g. Health and Welfare Guideline) 




an acceptable daily intake limit 




contaminant residue in aquatic biota value 



md : 



A bioconcentration factor a 1000 (In the absence of 
consumption limits, bioaccumulation may be significant and 
the Guideline setting process should be followed) 



or: 



X 


A bioconcentration factor s 1000 (In the absence of 




consumption information, bioaccumulation is not considered 




to be significant) . 



If BCF data is unavailable: 



Log Kow 2 4.00, then bioaccumulation is assumed to be 
significant and the Guideline setting process should be 
followed . 



or : 



Log Kow s 4.00, then bioaccumulation is assumed not to be 
significant . 



41 



Mutagenicity 

A) For Initial Assessment 





Chemical is considered to be non-mutagenic (i.e. data from 




a minimum of two test systems, including tests for 




mutagenic as well as chromosomal damage endpoints, clearly 




demonstrating . 



or: 



Chemical is considered to be mutagenic in aquatic or 
mammalian systems. - Possibly, data is inconclusive 



B) For Setting PWQOs (A total of three studies are required 
for mutagenicity. 

VERTEBRATES 

(All data must be primary and measured in whole aquatic 
organisms, Marine and brackish tests are not permitted) 





Data 


from at least one of the following three categories: 




fish 


- mutagenicity related diseases 




fish 


- mutagenicity or chromosomal aberrations 




o t he r 


vertebrate mutagenicity of chromosomal aberration 



INVERTEBRATES 

Data from a maximum of two of the following three categories: 





invertebrate - mutagenicity or chromosomal aberration 




aq^jatic plant - mutagenicity or chromosomal aberration 




microbial - mutagenicity 



42 



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