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Criteria used by the PBT Profiler

Introduction

The PBT Profiler is a screening-level tool that provides estimates of the persistence, bioaccumulation, and chronic fish toxicity potential of chemical compounds. It is designed to be used when no data are available. In order to help interested parties make informed decision on a chemical’s PBT characteristics, the PBT profiler automatically identifies chemicals that may persist in the environment and bioaccumulate in the food chain.   These chemicals are identified using thresholds published by the EPA. By comparing the estimated persistence and bioaccumulation provided by the PBT Profiler, interested parties can rapidly obtain information to make informed judgments on the PBT characteristics of the chemicals under consideration. This screening assessment can be used early in the decision making process to help users better focus resources and identify pollution prevention opportunities.

The thresholds the PBT profiler uses to highlight chemicals that may persist and/or bioaccumulate in the environment are based on information published by the EPA in the Federal Register.   The first is a policy statement on a new category for PBT substances for the review of Premanufacture Notices (PMNs) submitted under section 5 of the Toxic Substances Control Act (TSCA).   The second is a final rule that added several chemicals with PBT characteristics and lowered reporting thresholds for certain PBT chemicals that were already listed on the Toxics Release Inventory (TRI), under section 313 of the Emergency Planning and Community Right-to-Know Act (EPCRA). The criteria published in these two Federal Register notices are comparable.

The PBT profiler uses a different set of criteria to highlight chemicals that may be toxic.   These criteria are based on the scientific principles and quantitative structure activity relationships that have been used to screen for toxicity in EPA’s New Chemical Program for over 20 years.

The following sections provide an overview of the persistence, bioaccumulation, and toxicity criteria the PBT Profiler uses to highlight chemicals. Extensive discussions of the scientific basis for the persistence and bioaccumulation criteria are provided in the EPA notices discussed herein.   Interested parties are invited to read the full text of these notices, which are available on-line using the links provided. A discussion of how the PBT Profiler estimates persistence, bioaccumulation, and toxicity is provided in the PBT Methodology section.

Persistence Criteria To Top
 

To highlight a chemical that may persist in the environment, the PBT profiler uses criteria set forth by the EPA in the Federal Register. An overview of these criteria as presented in a final rule and a policy statement on a new PBT category for new chemicals is provided below. The user is encouraged to follow the links to the Federal Register documents to gain insight on the scientific rationale for the persistence criteria, details on the actions they describe, and other persistence criteria that have been brought forward by other domestic and international organizations

The persistence criteria for EPA’s policy statement on a new PBT category for Premanufacture Notices are: [Category for Persistent, Bioaccumulative, and Toxic New Chemical Substances, Federal Register: November 4, 1999 (Volume 64, Number 213), pages 60194-60204.]

TSCA Section 5 Action
5 (e) Order/Significant New Use Rule (SNUR) Ban Pending Testing
Half-life in water, soil, and sediment Half-life > 2 months
(> 60 days)
Half-life > 6 months
(> 180 days)

The persistence criteria for EPA’s final rule for TRI reporting are: [ Persistent Bioaccumulative Toxic (PBT) Chemicals; Lowering of Reporting Thresholds for Certain PBT Chemicals; Addition of Certain PBT Chemicals; Community Right-to-Know Toxic Chemical Reporting: Final rule, Federal Register: October 29, 1999 (Volume 64, Number 209), pages 58666-58753.]

Considered Persistent Considered Very Persistent
Half-life in water, soil, and sediment Half-life >= 2 months
(>= 60 days)
Half-life > 6 months
(> 180 days)
Half-life in Air Half-life > 2 days

The PBT Profiler combines the persistence criteria for water, soil, and sediment provided above and highlights chemicals with an estimated half-life >= 2 months and < 6 months in orange text and those with an estimated half-life > = 6 months in red. The half-life in air is not used in the PBT Profiler's Persistence summary. The PBT Profiler uses 30 days in a month for its comparisons. 

Bioaccumulation Criteria To Top
 

To highlight a chemical that may bioaccumulate in the food chain, the PBT profiler uses criteria set forth by the EPA in the Federal Register. These criteria use a bioconcentration factor (BCF) as the indicator of a chemical’s potential to bioaccumulate. An overview of these criteria as presented in a final rule and a policy statement is provided below. The user is encouraged to follow the links to the Federal Register documents to gain insight on the scientific rationale for the bioaccumulation criteria, details on the actions they describe, and other bioaccumulation criteria that have been brought forward by other domestic and international organizations.

The bioaccumulation criteria for EPA’s policy statement on Premanufacture Notices are: [Category for Persistent, Bioaccumulative, and Toxic New Chemical Substances, Federal Register: November 4, 1999 (Volume 64, Number 213), pages 60194-60204.]

TSCA Section 5 Action
5 (e) Order/Significant New Use Rule (SNUR) Ban Pending Testing
Bioconcentration factor (BCF) > = 1,000 > = 5,000

The bioaccumulation criteria for EPA’s rule for TRI reporting are: [ Persistent Bioaccumulative Toxic (PBT) Chemicals; Lowering of Reporting Thresholds for Certain PBT Chemicals; Community Right-to-Know Toxic Chemical Reporting: Final rule Federal Register: October 29, 1999 (Volume 64, Number 209), pages 58666-58753.]

Considered Bioaccumulative Considered Very Bioaccumulative
Bioconcentration factor (BCF) > = 1,000

> 5,000

The PBT Profiler combines the bioaccumulation criteria provided above and highlights chemicals with a BCF >= 1,000 and < 5,000 in orange text and those with a BCF > = 5,000 in red. 

Toxicity To Top
 

To highlight a chemical that may be chronically toxic to fish, the PBT profiler uses criteria developed in EPA’s New Chemical Program [Clements, R. G.; Nabholz, J. V.; Johnson, D. E.; and Zeeman, M. G. The Use of Quantitative Structure-Activity Relationships (QSARs) as Screening Tools in Environmental Assessment. Environmental Toxicology and Risk Assessment, 2nd Vol., edited by J.W. Gorsuch, F. J. Dwyer, C. G. Ingersoll, and T. W. LaPoint, pp 555-570. ASTM STP 1216. Philadelphia: American Society for Testing and Materials, 1993]. The criteria used in the New Chemicals Program are:

Low Concern Moderate Concern High Concern
Fish ChV (mg/l) > 10 mg/l 0.1 - 10 mg/l < 0.1 mg/l

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