Appendix 8: Test Criteria for the Sunrise Approach - from the Public Advocacy Group Representatives Discussion Paper, August 2000
The various tests necessary for adequately measuring the various characteristics of concern are outlined below. Some of these tests are already required on the highest schedules for chemicals and polymers; others have been proposed to a subcommittee to the NSN consultation process.
Acute toxicity: tests for mammalian, fish, daphnia and algal toxicity.
Chronic toxicity: determination of an effective concentration to 50% for growth, total mass or photosynthesis rate inhibition in higher plants, 90-day mammalian, and indicators of chronic toxicity, such as a lowest-observed-adverse-effect level (LOAEL), a no-observed-adverse-effect level (NOAEL) and the maximum allowable toxicant concentration (MATC) in aquatic assays.31
Those tests relating to persistence already required by the highest schedule (such as hydrolysis and ready biodegradability), although the criteria cut-off of substances' half-lives in the media of air, water, sediment and soil may need to be lowered from that provided by the Toxic Substances Management Policy (TSMP).
Those tests relating to bioaccumulation and the octanol/water partition coefficient (Kow) already required by the highest schedule (such as water solubility, fat solubility, dissociation constant), although the criteria cut-off for log Kow may need to be lowered from that provided by the TSMP.
Tests for 20, 100 and 500 ODP, as well as the atmospheric lifetime for those classes of substances to which these measurements apply.
Tests for 20, 100 and 500 GWP, as well as the atmospheric lifetime for those classes of substances to which these measurements apply.
Screening new substances for endocrine disrupting potential is possible and can add value in the NSN assessment. The U.S. Environmental Protection Agency Tier 1 and Tier 2 model is proposed here:
in vitro assays include:
- an estrogen receptor binding or reporter gene assay;
- an androgen receptor binding or reporter gene assay; and
- a steroidogenesis assay with minced testis.
in vivo assays include:
- a rodent 3-day uterotrophic assay;
- a rodent 20-day pubertal female assay with enhanced thyroid endpoints;
- a rodent 5- to 7-day Hershberger assay;
- a frog metamorphosis assay; and
- a fish reproductive screening assay.
The assessment can evaluate the Tier 1 data and other scientifically relevant information (e.g., high through put screenings, quantitative structure-activity relationships, referred to as "QSARs", or literature data) to decide if the chemical can be moved to a "hold category (needs no further analysis at this time)" or needs to undergo Tier 2 Testing. Tier 2 testing will determine whether it may have an effect in humans that is similar to the effect produced by a naturally occurring hormone.
The Tier 1 assays have the necessary breadth and depth to detect all currently known chemicals that may affect the endocrine, androgen and thyroid systems. Therefore, after having gone through the Tier 1 screening battery, a chemical will be designated as having either the potential for estrogen, androgen or thyroid activity, which will require further analysis in Tier 2 tests to verify and evaluate that potential; or low or no potential for estrogen, androgen or thyroid activity, which will allow the chemical to be put on "hold."
The Tier 2 tests are longer-term studies designed to encompass critical life stages and processes, a broad range of doses and administration by a relevant route of exposure. Effects associated with endocrine disruption may be latent and not manifested until later in life or may not appear until the reproductive period is reached. Therefore, Tier 2 tests will usually encompass two generations and will include effects on fertility and mating, embryonic development, sensitive neonatal growth and development, and transformation from the juvenile life stage to sexual maturity.
Tier 2 tests include:
- a two-generation mammalian reproductive toxicity study or a less comprehensive alternative;
- a mammalian reproductive toxicity test;
- an avian reproduction toxicity test;
- a fish life cycle toxicity test;
- an opossum shrimp (Mysidacea) or other invertebrate life cycle toxicity test; and
- an amphibian development and reproduction test.
Environment Canada and Health Canada may decide to require less testing based on scientifically relevant information showing that effects can be adequately characterized in a one-generation assay.
The Sunrise clause could take the form of either an absolute threshold limit for each criterion or a scoring system wherein a substance could not exceed a certain cumulative score for all categories combined. An example of the latter approach, as applied to select indicators, is illustrated below:
Before applying such a system, careful thought would have to be given to what numeric test results would be associated with each score and the relationship that ranks achieved in each category would have to one another. For instance, it could be decided that a substance would be DSL-bound if it did not exceed x number of "poor" scores throughout the entire assessment process. Alternatively, the tests could be divided into smaller subsets according to nature of the effect, location of the effect, etc., and allocated a given number of allowable "poor" scores for each subset.
| Score* | Good | Moderate | Poor |
|---|---|---|---|
| Acute Aquatic Lethality (LC50 or EC50, mg/L)32 | >100 | 100-1 | <1 |
| Chronic Aquatic Toxicity (NOAEC, mg/L)33 | >0.02 | 0.02-0.0002 | <0.0002 |
| Acute Oral Lethality (LD50, mg/kg)34 | >500 | 500-5 | <5 |
| Persistence (half-life in aquatic environment, days)35 | <50 | 50-180 | >180 |
| Bioaccumulation (Bioaccumulation Factor [BAF], where log BAF = 1.07 log Kow - 0.21)36 | <500 | 500-1 000 | >1 000 |
| Ozone Depleting Potential (ODP, relative to CFC-11 and CFC-12)37 | <0.01 | 0.01-0.70 | >0.70 |
| Global Warming Potential (GWP, equal mass relative to CO2 over 100 years)38 | <1 | 1-500 | >500 |
Footnotes
* LC50 = median lethal concentration; ED50 = median effective dose; LD50 = median lethal dose; NOAEC = no-observed-adverse-effect concentration; CFC = chlorofluorocarbon.
31 M. Swanson and A. Socha, Chemical Rankingand Scoring: Guidelines for Relative Assessments of Chemicals (1997), p. 93.
32 Environment Canada, Environmental Leaders 2: Accelerated Reduction/Elimination of Toxics (ARET) (1997), p. 36.
33 Environment Canada, Environmental Leaders 2: Accelerated Reduction/Elimination of Toxics (ARET) (1997), p. 36.
34 Environment Canada, Environmental Leaders 2: Accelerated Reduction/Elimination of Toxics (ARET) (1997), p. 36.
35 For "poor" category, taken from:Environment Canada, Environmental Leaders 2: Accelerated Reduction/Elimination of Toxics (ARET) (1997), p. 34.
36 Based in part on Environment Canada, Environmental Leaders 2: Accelerated Reduction/Elimination of Toxics (ARET) (1997),p. 34; and U.S. Environmental Protection Agency, Proposed Category for Persistent,Bioaccumulative, and Toxic Substances (October 5, 1998); (http://www.epa.gov/oppt/pbt/)
37 M. Swanson and A. Socha, Chemical Rankingand Scoring: Guidelines for Relative Assessmentsof Chemicals (1997), p. 121.
38 M. Swanson and A. Socha, Chemical Rankingand Scoring: Guidelines for Relative Assessmentsof Chemicals (1997), p. 120.
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