Screening Assessment for the Challenge 2-Naphthalenecarboxamide,N-(5-chloro-2,4-dimethoxyphenyl)-4-[[5-[(diethylamino)sulfonyl]-2-methoxyphenyl]azo]-3-hydroxy- (Pigment Red 5)

Chemical Abstracts Service Registry Number 6410-41-9

Environment Canada
Health Canada

February 2009

Table of Contents

1. Synopsis
2. Introduction
3. Substance Identity
4. Physical and Chemical Properties
5. Sources
6. Uses
7. Releases to the Environment
8. Environmental Fate
9. Persistence and Bioaccumulation Potential
10. Potential to Cause Ecological Harm
11. Conclusion
12. References
13. Appendix I. Robust study summaries

Synopsis

Pursuant to section 74 of the Canadian Environmental Protection Act, 1999 (CEPA 1999), the Ministers of the Environment and of Health have conducted a screening assessment on 2-Naphthalenecarboxamide,N-(5-chloro-2,4-dimethoxyphenyl)-4-[[5-[(diethylamino)sulfonyl]-2-methoxyphenyl]azo]-3-hydroxy- (Pigment Red 5), Chemical Abstracts Service Registry Number 6410-41-9. This substance was identified as a high priority for screening assessment and included in the Challenge because it was originally found to meet the ecological categorization criteria for persistence, bioaccumulation potential and inherent toxicity to non-human organisms and is believed to be in commerce in Canada.

The substance Pigment Red 5 was not considered to be a high priority for assessment of potential risks to human health, based upon application of the simple exposure and hazard tools developed by Health Canada for categorization of substances on the Domestic Substances List. Therefore, this assessment focuses on information relevant to the evaluation of ecological risks.

Pigment Red 5 is an organic substance that is used in Canada and elsewhere primarily as a colour pigment in plastics, inks, paints and textiles, and is also used in cosmetics, soaps and detergents, and in the rubber, fabricated metal products and electronic equipment sectors. The substance is not naturally produced in the environment. It is not reported to be manufactured in Canada; however, 100 kg of the pigment were imported into the country in 2006.

Based on reported use patterns and certain assumptions, most of the substance ends up in waste disposal sites. Estimates predict that 1.8% of Pigment Red 5 may be released to soil. No releases are predicted to air, surface water and groundwater. Pigment Red 5 is characterized by low to very low experimental solubility in water and octanol (less than 150 µg/L). It is present in the environment primarily as micro-particulate matter that is not volatile and rather chemically stable, and it has a tendency to partition by gravity to sediments if released to surface waters, and to soils if released to air over terrestrial environments.

Based on its physical and chemical properties, Pigment Red 5 is determined to be persistent in all environmental media. However, new experimental data relating to its solubility in octanol and water suggest that this pigment has a low potential to accumulate in the lipid tissues of organisms. The substance therefore meets persistence criteria but does not meet bioaccumulation criteria as set out in the Persistence and Bioaccumulation Regulations. In addition, new experimental toxicity data for a chemical analogue, as well as new toxicity predictions that take into account revised estimates of bioaccumulation potential, suggest that saturated solutions of the substance do not cause acute harm to aquatic organisms.

A quantitative evaluation of exposure and of ecological effects was conducted as part of the weight-of-evidence evaluation of this pigment's potential to cause harm. Based upon a conservative, generic scenario, the risk posed by exposure to Pigment Red 5 was estimated to be low. Considering these findings, it is concluded that Pigment Red 5 is unlikely to be causing ecological harm in Canada.

This substance will be included in the upcoming Domestic Substances List inventory update initiative. In addition and where relevant, research and monitoring will support verification of assumptions used during the screening assessment.

Based on the information available, it is concluded that Pigment Red 5 does not meet any of the criteria set out in section 64 of CEPA 1999.

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Introduction

The Canadian Environmental Protection Act, 1999 (CEPA 1999) (Canada 1999) requires the Minister of the Environment and the Minister of Health to conduct screening assessments of substances that have met the categorization criteria set out in the Act to determine whether these substances present or may present a risk to the environment or human health. Based on the results of a screening assessment, the Ministers can propose to take no further action with respect to the substance, to add the substance to the Priority Substances List (PSL) for further assessment, or to recommend that the substance be added to the List of Toxic Substances in Schedule 1 of the Act and, where applicable, the implementation of virtual elimination.

Based on the information obtained through the categorization process, the Ministers identified a number of substances as high priorities for action. These include substances that

• met all of the ecological categorization criteria, including persistence (P), bioaccumulation potential (B) and inherent toxicity to aquatic organisms (iT), and were believed to be in commerce; and/or
• met the categorization criteria for greatest potential for exposure (GPE) or presented an intermediate potential for exposure (IPE), and had been identified as posing a high hazard to human health based on classifications by other national or international agencies for carcinogenicity, genotoxicity, developmental toxicity or reproductive toxicity.

The Ministers therefore published a notice of intent in the Canada Gazette, Part I, on December 9, 2006 (Canada 2006), that challenged industry and other interested stakeholders to submit, within specified timelines, specific information that may be used to inform risk assessment, and to develop and benchmark best practices for the risk management and product stewardship of those substances identified as high priorities.

The substance 2-Naphthalenecarboxamide,N-(5-chloro-2,4-dimethoxyphenyl)-4-[[5-[(diethylamino)sulfonyl]-2-methoxyphenyl]azo]-3-hydroxy- was identified as a high priority for assessment of ecological risk as it was found to be persistent, bioaccumulative and inherently toxic to aquatic organisms and is believed to be in commerce in Canada. The Challenge for Pigment Red 5 was published in the Canada Gazette on August 18, 2007 (Canada 2007). A substance profile was released at the same time. The substance profile presented the technical information available prior to December 2005 that formed the basis for categorization of this substance. As a result of the Challenge, submissions of information were received.

Although Pigment Red 5 was determined to be a high priority for assessment with respect to the environment, it did not meet the criteria for GPE or IPE and high hazard to human health based on classifications by other national or international agencies for carcinogenicity, genotoxicity, developmental toxicity or reproductive toxicity. Therefore, this assessment focuses principally on information relevant to the evaluation of ecological risks.

Under CEPA 1999, screening assessments focus on information critical to determining whether a substance meets the criteria for defining a chemical as toxic as set out in section 64 of the Act, where

Screening assessments examine scientific information and develop conclusions by incorporating a weight-of-evidence approach and precaution. 

This draft screening assessment includes consideration of information on chemical properties, hazards, uses and exposure, including the additional information submitted under the Challenge. Data relevant to the screening assessment of this substance were identified in original literature, review and assessment documents, stakeholder research reports and from recent literature searches, up to February 2008. Key studies were critically evaluated; modelling results may have been used to reach conclusions. When available and relevant, information presented in hazard assessments from other jurisdictions was considered. The draft screening assessment does not represent an exhaustive or critical review of all available data. Rather, it presents the most critical studies and lines of evidence pertinent to the conclusion.

This screening assessment was prepared by staff in the Existing Substances Programs at Health Canada and Environment Canada and incorporates input from other programs within these departments. The draft of this screening assessment was subject to a 60-day public comment period. While external comments were taken into consideration, the final content and outcome of the screening assessment remain the responsibility of Health Canada and Environment Canada. Additionally, the draft of this screening assessment was subject to a 60-day public comment period. The critical information and considerations upon which the assessment is based are summarized below.

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Substance Identity

For the purpose of this document, this substance will be referred to as Pigment Red 5. This pigment belongs to the group of Naphthol AS III organic pigments, for which the basic entity is the anilide of 2-hydroxy-3-naphthoic acid (Table 1; Herbst and Hunger 2004).

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Physical and Chemical Properties

The pigment industry synthesizes organic pigments that have low to very low solubilities in nearly all solvents (i.e., less than 1 mg/L to less than 0.01 mg/L). This arises from the desire of the industry to produce chemicals that will retain their colour for a long time and in any type of material. Low solubility is enhanced by designing chemicals that have strong interactive forces between molecules. For Naphthol AS compounds, this is achieved by the introduction of substituents like -CONH₂, -SO₂NH-, or -Cl in the molecule (Herbst and Hunger 2004; Lincke 2003). The resulting intermolecular bonds, in turn, generate a crystal structure that is at the origin of the stability of organic pigments (Lincke 2003).

As is the case with the majority of organic pigments, Naphthol AS III pigments generally do not exist as individual molecules but are principally particles in the submicron range. The pigment powder is typically composed of primary particles (i.e., the crystal lattice of a pigment), aggregates and agglomerates. Manufacturers usually provide the physical specifications of their pigments, which include the average particle size of the pigment powder. In doing so, users can determine which pigment is the most appropriate to colour their product(s), since performance is chiefly controlled by the particle size distribution (Herbst and Hunger 2004).

Table 2 contains modelled and experimental physical and chemical properties of Pigment Red 5 that are relevant to its environmental fate. Modelled estimates for these properties, as well as for rate constants and environmental partitioning, are typically generated using quantitative structure-activity relationship (QSAR) models. These models, in turn, base their predictions on the individual characteristics of the molecules. The modelled log K_owof 7.65 (KOWWIN 2000) implies that the solubility of Pigment Red 5 is much higher in octanol than in water. Experimental solubility data, however, reveals that the substance has roughly similar solubilities in both solvents, indicating that the modelled partition coefficient is likely overestimated. The modelled estimate of log K_ow has therefore been disregarded for this assessment.

The experimental solubilities in Table 2 have been determined using an aggressive approach with long contact times between pigment particles and the solvent, and a filtration step removing as much of the particulate matter in the suspension as possible. These studies have been critically reviewed, and although none reported using reference chemicals of known solubilities, they were determined to have a satisfactory degree of reliability for the present assessment.

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Sources

Pigment Red 5 is not known to be formed in nature. In Canada, no manufacture of this substance was reported in response to a CEPA 1999 section 71 survey notice for the 2006 calendar year in a quantity meeting the 100-kg reporting threshold. One company reported importing 100 kg of this pigment for use in the manufacturing of various coloured products. No companies reported using a total quantity greater than 1000 kg of the substance, whether alone, in a mixture, in a product or in a manufactured item, at any concentration. Ten organizations have identified a stakeholder interest in this substance (Environment Canada 2008a). One of these stakeholders is an American company that reported exporting Pigment Red 5 to Canada.

No companies reported manufacturing or importing Pigment Red 5 in response to a CEPA 1999 section 71 survey notice for the 2005 calendar year in a quantity meeting the 100-kg reporting threshold. However, three Canadian companies and one American Industrial Association identified themselves as having a stakeholder interest in this substance. 

Products containing Pigment Red 5 may enter the country even if they are not identified as such in the section 71 survey because they may be imported unknowingly in manufactured items, or in quantities below the 100-kg reporting threshold for the survey.

In the United States, between 4500 and 226 800 kg of Pigment Red 5 were manufactured and/or imported in each of the following years: 1994, 1998 and 2002 (US EPA 2007). Pigment Red 5 was in use in Denmark, Sweden and the Netherlands during 1999 to 2005 (SPIN 2007).

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Uses

According to responses to a CEPA 1999 section 71 survey notice for 2006, the only current use pattern for Pigment Red 5 in Canada is as a colorant/pigment/stain/dye/ink (Environment Canada 2008a). The importing company appears to be a wholesaler and distributor of chemicals, and it indicated that the main applications for this substance included plastic coloration and the manufacturing of printing inks and paints (Environment Canada 2008a). Voluntary information submitted as part of the Challenge also indicated that one United States company exported slightly more than 100 kg of Pigment Red 5 to Canada in 2006 for use in paints and coatings for cars and other purposes.

The following use codes were specified for the substance during the DSL nomination: colorant - pigment/stain/dye/ink, organic chemicals, industrial, photographic/photocopier, pigment, dye and printing ink, and textile, primary manufacture. Data collected during DSL nomination in the 1980s suggest that this substance could also be used in the manufacture of textiles.

Internationally, Pigment Red 5 has been used as a colorant

• in plastic compounding (Environment Canada 2008a);
• in printing inks for wood and paper (Environment Canada 2008a; Herbst and Hunger 2004);
• in paints, surface coatings, and water-based pigment dispersions (Environment Canada 2008a; Herbst and Hunger 2004; SPIN 2007);
• for textiles, spin coloration of viscose rayon (CII 2002; Herbst and Hunger 2004);
• in cosmetics such as lipstick, eye shadow, powder and nail polish (CII 2002; Herbst and Hunger 2004); and
• in soaps, detergents, shower gel, and hand-cleansing cream (CII 2002; SPIN 2007).

Uses in Canada as a colorant/pigment/stain/dye/ink are considered to be similar to those identified above.

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Releases to the Environment

The company that reported importing this substance in 2006 did not indicate any releases of this chemical to the environment.

Mass Flow Tool

To estimate potential release of the substance to the environment at different stages of its life cycle, a Mass Flow Tool was used. Empirical data concerning releases of specific substances to the environment are seldom available. Therefore, for each identified type of use of the substance, the proportion and quantity of release to the different environmental media are estimated, as is the proportion of the substance chemically transformed or sent for waste disposal. Assumptions and input parameters used in making these estimates are based on information obtained from a variety of sources including responses to regulatory surveys, Statistics Canada, manufacturers' websites and technical databases. Of particular relevance are emission factors, which are generally expressed as the fraction of a substance released to the environment, particularly during its manufacture, processing, and use associated with industrial processes. Sources of such information include emission scenario documents, often developed under the auspices of the Organisation for Economic Co-operation and Development (OECD), and default assumptions used by different international chemical regulatory agencies. It is noted that the level of uncertainty in the mass of substance and quantity released to the environment generally increase further down the life cycle. 

Results (Table 3) indicate that Pigment Red 5 can be expected to be found largely in waste management sites (88.3%), due to the eventual disposal of manufactured items containing it. Unless specific information is available on the rate or potential for releases to occur from landfills and incinerators, the Mass Flow Tool does not quantify releases from these sources. A small fraction of solid waste is incinerated, which is expected to result in transformation of the substance. Based largely on information contained in OECD emission scenario documents for processing and uses associated with this substance, it is estimated that 1.8%, 0% and 9.9% of the pigment may be released to soil, air, and sewer respectively. Releases of Pigment Red 5 to wastewater are predicted to be mostly due to recycled printing ink. Releases to soil are expected to occur from equipment residues and from flaking and chipping of paints during automotive refinishing and household decorative painting.

Although no information is available on the total quantity of importation of consumer products containing Pigment Red 5, it is anticipated that the quantities of releases to the various environmental media would not be significantly different from those estimated here. However, the quantities sent for waste management would be higher if importation of these products were taken into consideration.

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Environmental Fate

The very low modelled vapour pressure and a negligible Henry's Law constant of ~ 10^-16 Pa·m³/mol for Pigment Red 5 are consistent with the fact that it is a large and complex molecule (Baughman and Perenich 1988; Danish EPA 1998). This pigment is not expected to volatilize at environmentally realistic temperatures.

Because of its very low solubility in water, this pigment may be considered not available for aerobic biodegradation. In addition, when incorporated in the materials it is destined to colour, this pigment is probably no longer in a form easily available for biota.

The particulate character of Pigment Red 5 should have a key influence on its fate in the environment. Its particle size and density, which is 40 to 44% greater than that of water (Wetzel 2001; Reynolds et al. 1987), together with its chemical stability and low aqueous solubility, indicates that it will partition by gravity to sediments if released to surface waters and will tend to remain in soils if released to terrestrial environments.

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Persistence and Bioaccumulation Potential

Environmental Persistence

Jaffe (1996) has stated that once a pigment is incorporated into a matrix (e.g., plastic), it is expected to be durable and withstand the combined chemical and physical stresses of weather, solar radiation, heat, water and industrial pollutants.

Industries that manufacture pigments recognize that their substances are persistent. For example, the Color Pigments Manufacturers Association, Inc. (CPMA 2003) has indicated that pigments are designed to be durable or persistent in the environment in order to provide colour to finished coatings, inks and paints.

The environmental persistence of Naphthol AS III pigments such as Pigment Red 5 in anoxic environments is an important area of uncertainty. Azo dyes are reported to be degraded in anoxic waters via anaerobic reduction of the azo bond (-N=N-: Van der Zee 2002). Naphthol AS III pigments have azo chromophores in their structure as well. However, no documentation has been found regarding a possible degradation potential of these pigments in aqueous media in the absence of oxygen. In principle, the crystal would have to dissolve first, releasing its constituent molecules. Then, the azo bonds in these molecules would be available for biotic reduction. However given its limited solubility, it is expected that only a very small proportion of the pigment would be reduced in this manner.

Based on the weight of evidence provided by the above-described literature, Pigment Red 5 is considered to meet the persistence criteria defined in the Persistence and Bioaccumulation Regulations (Canada 2000).

Potential for Bioaccumulation

For most organic compounds there is a predictable relationship between K_ow and the bioconcentration factor in lipids (Mackay 1982). However the model-derived K_ow value is not considered to be a good indicator of the bioaccumulation potential of Pigment Red 5.

The ratio log (C_o/C_w) has been estimated from the experimental solubilities of Pigment Red 5 in octanol (C_o) and water (C_w) (Table 2), and this experimentally derived ratio has been preferred over the model-derived log K_ow for this pigment. This approach is supported by the observation that partitioning into octanol is a good indicator of a substance's potential to partition into the lipid phase of aquatic biota (Bertelsen et al. 1998) and, for pigments, the observation that a reduced solubility in octanol translates into a similarly reduced bioconcentation factor (BCF) and bioaccumulation factor (BAF) in an aquatic organism (Banerjee and Baughman 1991).

A revised set of BCF and BAF estimates for Pigment Red 5 has been obtained from quantitative structure-activity relationship (QSAR)-based bioaccumulation models, using the experimentally based value log (C_o/C_w) in place of the overestimated log K_ow by KOWWIN (2000). Table 4 shows that the revised modelled BCF and BAF estimates are well below 1000 (log BCF/BAF of 3) for this pigment.

Thus, Pigment Red 5 is expected to present a low bioaccumulation potential because of its very limited affinity for the lipid phase of living organisms. Further support is provided by experimental determinations for six representative organic pigments, all with BCF values less than 100 wet wt (MITI 1992).

The above weight of evidence indicates that Pigment Red 5 does not meet the bioaccumulation criterion (BCF, BAF greater than or equal to 5000) as set out in the Persistence and Bioaccumulation Regulations (Canada 2000).

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Potential to Cause Ecological Harm

A quantitative evaluation based on exposure and ecological effects was conducted for this pigment as part of the weight-of-evidence evaluation of its potential to cause harm.

First, a predicted environmental concentration (PEC) was determined based on an analysis of exposure pathways. Then, pertinent endpoint organisms were selected. For each endpoint organism, a conservative (reasonable worst-case) predicted no-effect concentration (PNEC) was derived. The PNEC is obtained by selecting the lowest critical toxicity value (CTV) for the organism of interest and dividing it by an application factor appropriate for the endpoint.

Ecological Effects Assessment

A - In the Aquatic Compartment

Although no experimental toxicity data were found for Pigment Red 5, there are experimental toxicity data available for Pigment Red 146, which is a close analogue of Pigment Red 5 (Table 4, CAS RN 5280-68-2). Furthermore, a predicted ecotoxicity value was obtained using the experimental log (C_o/C_w) of Pigment Red 5 (1.22) instead of the modelled log K_ow. These experimental and predicted toxicity data (Tables 5a and 5b) are considered reliable and have been used in the weight-of-evidence approach to determine the aquatic toxicity potential of this pigment.

Juveniles of Daphnia magna were exposed to a saturated solution of Pigment Red 146 for 48 hours under static conditions (Study Submission 2007c; Table 5a). The pH was maintained between 7.6 and 7.7, the temperature oscillated between 18 and 22°C and dissolved oxygen ranged between 8.0 and 8.5 mg/L. The test water had a hardness of 249 mg CaCO₃/L. An experimental treatment consisted of 5 specimens placed in a 50-mL glass beaker. One test concentration of 100 mg/L was established, using 4 replicates per test. In order to make a saturated solution, a stock solution of 100 mg Pigment Red 146 in 1 Lof test water was made. The stock solution was shaken at room temperature at 20 rpm for 24 hours (rotating shaker). Undissolved particles were removed by filtration on 0.45-µm membrane. This approach followed the guidance provided by the OECD for sparingly soluble substances (OECD 2000). The chemical was not measured during the test. No biologically significant effects (immobilization) were observed at saturation.

The degree of reliability of this study was deemed satisfactory for the present assessment. Notably, a reference toxicant was used and good laboratory practices were followed.

Aquatic toxicity predictions for this pigment were recalculated using log (C_o/C_w) in place of the modelled log K_ow. The ASTER (1999) model predicted the mode of action (MOA) uncoupling of oxidative phosphorylation for fathead minnows based on substructural fragments associated with this mode of action. A QSAR was developed for estimating acute LC₅₀s associated with this MOA in fathead minnows (Russom et al. 1997). Table 5b presents the modelled ecotoxicity result. It should be noted that the MOA prediction is for the solubilized molecule.

The modelled toxicity value is well above the estimated water solubility of the substance. This result is thus consistent with that of the experimental acute toxicity test, which indicates no effects at saturation.

B - In Other Environmental Compartments

No empirical or predicted effects data for non-aquatic organisms were identified for this compound. However, given the current release scenarios and quantities used in Canada, exposures through soils, suspended solids and sediment are not likely to be significant at this time.

Pigment Red 5 is considered to be a structural analogue to Pigment Red 146; however, it differs from Pigment Red 146 in two chemical features. On the upper terminal benzene ring there is a permutation of the position of the chloro- and methoxy- substituents. This difference of position could not strongly impact the ecotoxicity of Pigment Red 5 and Pigment Red 146. The lower benzene ring shows the replacement of the sulfonamide substituent of Pigment Red 5 by an aromatic amide for Pigment Red 146. Sulfonamide and aromatic amide substituents are both moieties for which there is no known environmental ecotoxicity concern. Moreover, both structures are deactivating substituents with similar molecular weight and structural hindrance potential. Overall, these structural differences will not strongly impact the ecotoxicity of Pigment Red 5 and Pigment Red 146. Consequently, Pigment Red 5 and Pigment Red 146 can be considered as analogues for ecotoxicity.

Ecological Exposure Assessment

No data have been found regarding concentrations of Pigment Red 5 in the Canadian environment. The Mass Flow Tool estimated that ~ 88% of the mass of this pigment ends up in waste disposal facilities. Off-site chemical migration from these facilities is unlikely, or can be predicted to be minor because of the negligible geochemical mobility of the pigment indicated by its very low solubility in water and in organic solvents. Consequently, it is anticipated that there are negligible releases associated with the waste management stage of this substance.

The Mass Flow Tool estimated that 9.9% (or ~ 20 kg), and 1.8% (or ~ 4 kg) of the total mass of Pigment Red 5 in use in 2006 could be released to wastewater and soil, respectively associated with use of this substance in the manufacturing of coloured products. The Industrial Generic Exposure Tool - Aquatic (IGETA) was selected to conservatively model the discharge of an industrial operation (user of the pigment) to the aquatic environment. IGETA is a modelling tool developed by Environment Canada to estimate surface water concentrations. The tool models an industrial release scenario based on loading data from sources such as industrial surveys and knowledge of the distribution of industrial discharges in the country, and calculates a predicted environmental concentration (PEC). The equation and default inputs used to calculate the PEC in the receiving watercourse (a generic small river) are described in Environment Canada (2008b). The maximum mass, per year, used by an industrial facility (1000 kg: Environment Canada 2008a) was taken to calculate the loading rate for the PEC estimation. The percentage loss from manufacturing or handling was estimated at 5%, the number of processing days per year was estimated at 150 while the estimated removal from sewage treatment was estimated to be 0 percent. Based on IGETA results, the annual average PEC (assuming instantaneous dilution) is 0.0056 mg/L in the receiving watercourse (Environment Canada 2008b).

Characterization of Ecological Risk

The approach taken in this ecological screening assessment was to examine various supporting information and develop conclusions based on a weight-of-evidence approach and using precaution as required under CEPA 1999. Particular consideration was given to risk quotient analysis, persistence, bioaccumulation, toxicity, sources and fate in the environment.

Pigment Red 5 is determined to be persistent based on published experimental evidence. However, it has been determined not to be bioaccumulative in accordance with the Persistence and Bioaccumulation Regulations of CEPA 1999 (Canada 2000), based on observations of its very low solubility in octanol, low modelled BCFs and low experimental BCFs determined for a number of analogous organic pigments (MITI 1992).

Newly acquired empirical data for a chemical analogue suggest that this pigment is not very harmful, showing a negligible acute toxicity for aquatic organisms. The experimental finding of no effect at saturation (i.e., 7.8 µg/L), indicates that acute toxicity is unlikely to result from exposure to the solubilized fraction at saturation, as well as to any very fine particulate matter that passed through the filter. Indeed, the mean particle size of the analogue Pigment Red 146 is 110 nm (NPIRI 2000) whereas the pore size of the filter used for the test solution is 450 nm. This empirical result is consistent with the modelled LC₅₀ for acute toxicity, that is much greater than the solubility of the compound.

A quantitative evaluation of exposure and of ecological effects was conducted as part of the weight-of-evidence evaluation of this pigment's potential to cause harm. First, a predicted environmental concentration (PEC) was determined based on an analysis of exposure pathways. Then, pertinent endpoint organisms were selected. For each endpoint organism, a conservative predicted no-effect concentration (PNEC) was derived. The PNEC is obtained by selecting the lowest critical toxicity value (CTV) for the organism of interest and dividing it by an application factor appropriate for the endpoint.

In view of the limited amount of empirical Canadian exposure data, the IGETA model was used, along with industrial information, to estimate worst-case PECs. Two categories of organisms were considered for derivation of PNECs: fish and daphnids. An application factor of 100 was used to extrapolate from acute to chronic effects, and from laboratory species to different species in the field. CTVs and PNECs are based on the most conservative effect values and are presented in Table 6. The fact that the PNEC is more than 100 times larger than the measured water solubility of the substance is a further indication that Pigment Red 5 poses little risk to aquatic organisms."

Considering these findings and given that this chemical is imported in relatively low quantities, it is concluded that Pigment Red 5 is unlikely to be causing ecological harm in Canada.

Uncertainties in Evaluation of Ecological Risk

This section summarizes the key uncertainties associated with the risk assessment of Pigment Red 5.

There is uncertainty in the current assessment resulting from the use of analogue data to evaluate the bioaccumulation potential and aquatic toxicity of Pigment Red5. As data were not available for Pigment Red 5, the modelled predictions for bioaccumulation and aquatic toxicity are based on experimental physical and chemical properties of analogues and the empirical toxicity data presented are based on studies of analogue substances.

Pigment Red 5 is expected to partition primarily to sediment; however experimental data on its fate and toxicity in sediments are lacking. Specifically, the long-term stability of Pigment Red 5 in anoxic sediments as well as in anoxic layers in the soil column of waste disposal sites has not been studied. It is however considered likely that the crystalline structure of Pigment Red 5 would be maintained in these compartments, and that the substance would remain unavailable to sediment and soil-dwelling organisms and unavailable for reduction of the azo bond, which could release bioavailable aromatic amines. Although acute and chronic toxicity data are not available for sediment or soil-dwelling organisms, toxicity is expected to be low based on information for aquatic organisms.

Nanoscale materials are informally defined as substances having at least one dimension less than 100 nm. There is increasing evidence to the effect that nanoparticles can be absorbed by non-specific biouptake pathways such as pinocytosis (Leroueil et al. 2007). Organic pigments such as Pigment Red 5 typically have a certain proportion of their particle size spectra in the nanoparticle range (e.g., Table 2). Presently, the bioaccumulation mechanisms and potential of these particles is poorly understood, as is the nature of the relationship between their bioaccumulation and their toxicity. Furthermore, certain less commonly considered environmental fate processes may have an important influence on the propensity of the pigment nanoparticles to be taken up by biota (e.g., importance of aggregation in nature: Wiesner et al. (2006)).

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Conclusion

Based on the information presented in this draft screening assessment, it is proposed that Pigment Red 5 is not entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity or that constitute or may constitute a danger to the environment on which life depends. 

It is therefore proposed that Pigment Red 5 does not meet the definition of "toxic" as set out in section 64 of CEPA 1999. Additionally, it is proposed that Pigment Red 5 is persistent but does not meet the criterion for bioaccumulation as set out in the Persistence and Bioaccumulation Regulations (Canada 2000).

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Appendix I. Robust study summaries

Evaluation of experimental data using Kollig's approach

Kollig, H.P. 1988. Criteria for evaluating the reliability of literature data on environmental process constants. Toxicol. Environ. Chem. 17: 287-311.

Table A-1. Evaluation of experimental data using Kollig's approach for 13365Challenge018

Table A-2. Evaluation of experimental data using Kollig's approach for 13365Challenge019

Table A-3. Robust Study Summaries Form and Instructions: Aquatic iT

13365Challenge007. Acute Immobilization Test (Static, 48 hr) to Daphnia magna STRAUS, Limit-Test, 2006