Briefing Note on Persistent Organic Pollutants

INTERNATIONAL

COUNCIL OF

CHEMICAL

ASSOCIATIONS

6 February 1998

INTERNATIONAL COUNCIL OF CHEMICAL ASSOCIATIONS (ICCA)

BRIEFING NOTE ON PERSISTENT ORGANIC POLLUTANTS (POPs)

Background

Persistent organic pollutants (POPs) persist in the environment for a long time, and are toxic to humans and/or wildlife, have a strong tendency to bioaccumulate in the food chain, and are prone to long-range transport. POPs represent a very small percentage of chemicals in commerce, and many are already strictly regulated or not currently in production. However, because of their physical and chemical properties, the regulation of

POPs has become an international policy issue based upon their possible effects on human health and potential environmental risks.

Negotiations concluded in March, 1998 on an U.N. Economic Commission for Europe

(UNECE) agreement to address POPs. POPs generally consist of three different groups: industrial chemical products such as PCBs, byproducts such as dioxins and furans, and pesticides such as DDT. The UNECE Protocol is generally supported by the chemical industries in North America and Europe. In addition, the North American Commission on

Environmental Cooperation (NACEC) has adopted a program on the sound management of persistent toxic substances. The UNECE Protocol and the NACEC program provide important precedent and guidance in the negotiation of a global agreement.

The United Nations Environment Program (UNEP) will begin negotiations on a legallybinding global agreement to address POPs in June, 1998. These negotiations are expected to take two to three years to complete.

ICCA Position

ICCA member associations have demonstrated their commitment to sound chemicals management, and to the goal of reducing the potential human health and environmental risks that may be associated with POPs. Many POPs are already subject to considerable voluntary risk management by chemical companies, and the uses of most substances identified as POPs has been discontinued or extremely limited by chemical companies within the countries represented by ICCA member associations.

The chemical industry supports a legally binding international agreement to establish a process to identify and characterize potential risks of POPs, and to apply appropriate risk management to POPs, provided that the following issues are addressed in the agreement:

 Scope of the Convention : The scope of the Convention should not expand initially beyond the 12 chemicals identified as Persistent Organic Pollutants (POPs) under the UNEP Governing Council’s mandate for the global agreement. Science based criteria and a procedure for identifying additional POPs as candidates for future international action must be agreed.

 Criteria for inclusion of additional POPs in the instrument : The criteria for including chemicals in the instrument should be risk-based and scientifically justified. Numerical screening levels should be established to be used in conjunction with professional judgment. See Annex B of the attached ICCA

Position Paper, which outlines ICCA’s recommendations for a process to identify

POPs for action at the global level.

 Process : The chemicals proposed to be included should be evaluated within a transparent, science-based, risk assessment process. This process should use numerical screening criteria to identify possible POPs to determine the need for further risk assessment or a reevaluation of current risk management. In evaluating risks, separate consideration should be given to human and environmental effects. Emphasis should be given to any likelihood of exposure, its possible magnitude and the characteristics and size of the exposed population.

 Risk Management : Industry supports risk management approaches that follow the results of risk assessments, and which reduce risks to acceptable levels. Possible alternatives to POPs must also be subject to socio-economic and risk assessments.

Risk management decisions must take into account all available management options, including production information, control techniques, and best practices, among others. The process and methods for assessments should recognize the participation of stakeholders, including industry experts, as well as the unique needs of developing countries.

 Nomination of substances : Only the parties to a global agreement should have the right to nominate substances as candidate POPs. Parties proposing substances for possible control under a global POPs agreement should be required to prepare and submit technical data sufficient to allow a determination of whether global action is warranted. In the event that a party does not have the technical resources to conduct such a review, the global agreement should provide a mechanism to coordinate international assessment efforts.

Additional Information

Additional information on ICCA’s position on the negotiation of a global POPs agreement can be obtained from:

Gordon Lloyd

Vice-President, Technical Affairs

Canadian Chemical Producers Association

805 - 350 Sparks Street

Ottawa, ON K1R 7S8 Canada

Tel: 613 237-6215

Anita Ringstrom

Deputy Director General

KEMIKONTORET

P.O. Box 5501

Storgatan, 19

S-11485 Stockholm, Sweden

Tel: ++ 46 87 83 81 47

Ian Swann

Plastics and Chemicals Industries Association

Royal Domain Centre

380 St. Kilda Road

Melbourne, Victoria 3001 Australia

Tel: ++ 61 39 699 6299

Michael P. Walls

Senior Counsel

Chemical Manufacturers Association

1300 Wilson Blvd.

Arlington, VA 22042 USA

Tel: ++ 703 741-5167

INTERNATIONAL COUNCIL OF CHEMICAL ASSOCIATIONS

Position on Persistent Organic Pollutants (POPs)

ABSTRACT

The Chemical Industry acknowledges that hazardous chemicals are one item of the international discussion on health, safety and the environment (see UNCED

Agenda 21, Chapter 19).

The international chemical industry’s position on Persistent Organic Pollutants

(POPs) is based on the following principles:

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POPs must be identified only by using well-defined scientific criteria and not on the basis of unfounded suspicions. Criteria for identification of POPs are proposed in this paper.

Any classification of a chemical substance as warranting management action must be based on a full risk assessment taking into account exposure levels, regional specificity’s and risk-benefit analysis.

Various risk management options to reduce the risk to an acceptable level are available but the type of actions must be adapted to the results of the risk assessment and to the type of products (industrial chemicals, pesticides and contaminants). These options could be based on voluntary agreements and/or regulatory measures.

On such a basis the chemical industry is willing to cooperate in a constructive way with the concerned international organizations on both a regional basis and on a global basis for POPs.

INTRODUCTION

As its representatives agreed with ministers at the Round Table Meeting of

Ministers and chemical industry CEOs in Stockholm, Sweden, January 15-16,

1996:

We support the UNEP Governing Council Decision of May 1995 on

Persistent Organic Pollutants as well as the recommendation of the

Washington Conference on Marine Pollution from Land-Based

Activities to develop a global legally binding instrument for those chemicals having been identified as POPs through a scientifically based assessment of hazards and risks. A global effort to reduce the risk of these chemicals should be based on an international process that includes the fundamental elements of risk

management as outlined in the preamble. IFCS should support the coordination of the various activities of UN organizations in order to avoid duplication of work and to harmonize the risk assessment of

POPs.

We recognize that risk management includes a range of risk reduction measures from product information to legally binding use restrictions including economic instruments when appropriate, as reflected in regional and international agreements.

In carrying out the science-based risk management process a situation may arise where scientific questions remain and where the weight of plausible scientific evidence establishes that damage to health or the environment is likely to be caused by the activity or product in question. In such cases the Precautionary Approach as referred to in Principle 15 of the Rio Declaration should be applied.

Consistent with these commitments the chemical industry has the skills and willingness to participate in discussions and to contribute scientific and technical information at all stages in the process to identify and evaluate chemicals which are introduced into the environment and undergo long-range transport via air

(including deposition) and/or water.

As explained further below, only those chemicals which have been subject to a full internationally accepted risk assessment and characterization, and for which the need for international risk management based on cost-benefit analysis has been demonstrated, should be called POPs.

DEFINITIONS, CRITERIA AND ASSESSMENT OF POPs

The following definitions and criteria are proposed for a scientific assessment process intended to select priority chemicals for risk assessment and management as POPs.

1. Definitions

POPs are substances which are persistent, toxic, liable to bioaccumulate, and which undergo long-range air transport into remote regions.

2. Criteria

The following criteria should guide expert scientific judgment in determining whether a substance is candidate for evaluation as a POP:

2.1 Long Range Transport

Consideration of a substance’s half-life in air and vapor pressure will aid in determining the potential to reach areas remote from production and use. If the potential for long range transport exists, an effort should be undertaken to demonstrate the relationship between release patterns and distribution in the environment. The presence of a substance in remote areas needs to be observed directly.

2.2 Persistence

Potential POPs must be assessed according to agreed upon screening levels for persistence in the environment, taking into account half-life under certain conditions.

2.3 Bioaccumulation/Bioconcentration

The substance must be assessed for its potential to accumulate in the tissue of organisms through intake from water, air, soil or food, normally based on lipophilicity and biological stability.

2.4 Toxicity

Candidate substances must be carefully characterized for their potential hazard to human health and the environment, taking into account a broad range of agreed-upon chronic endpoints, in relationship to exposure.

3. Assessment Process

Verification of all four criteria listed above, in a stepwise process, nominates a substance as a POP candidate. Only after positive results based on an application of an internationally agreed risk assessment methodology, can a candidate POP be considered definitely as a POP.

The above stepwise process, supported by industry, is consistent with proposals under consideration in UN Economic Commission and discussions under the auspices of the Intergovernmental

Forum on Chemical Safety (IFCS), and the mandate of the POPs

INC as established by the UNEP Governing Council.

RISK MANAGEMENT OF POPs

Industry supports the following approach to risk management:

1. Definition: Risk management follows the results of the risk assessment process and is designed to reduce risk to an acceptable level. It could be based on voluntary actions or regulatory measures.

2. Risk management decisions need to take into account:

- analysis of advantages and drawbacks;

- analysis of cost-effectiveness and the relation between costs and benefits;

- proportionality of risks and measures to address them;

- differences between industrial chemicals, pesticides and contaminants (by-products, impurities);

- avoiding distortion of competition;

- considerations of process, emissions, consumption and disposal.

3. Risk management of POPs must consider all available management options, such as:

- product information (classification, labeling, MSDS);

- application of best available techniques (BAT), e.g. for reduction or prevention of emissions;

- application of best environmental practice (BEP), including safe handling, minimization of exposure, promotion and use of cleaner products;

- use limitations.

Substitution requirements as well as bans or phase-outs should be considered as last resort options and only be applied if the evaluation process demonstrates "unreasonable and otherwise unmanageable risk" (see Agenda 21, Chapter 19, paragraph 44).

Finally, the chemical industry urges close cooperation between interested stakeholders, governments and international organizations so that risk assessment and cost-benefit analysis can be conducted in the most effective way.

TRADE IMPACTS

ICCA believes that Multilateral Environmental Agreements (MEAs), such as the proposed global agreement on POPs, are an appropriate way of addressing major transborder or global problems. ICCA, however, opposes the unqualified use of trade measures to compel compliance with MEAs.

Solutions to environmental problems should be appropriate and proportionate to the desired objective. Trade provisions should be included only if they are necessary to achieve an agreed environmental objective and if the objective is scientifically justified. ICCA stresses that any trade measure used pursuant to the

POPs instrument must be transparent and least trade distorting.

Also, MEAs must be negotiated in an open, transparent manner and should include fair and effective dispute settlement mechanisms. WTO members, however, should retain their rights and disciplines under the WTO, including the

right to invoke the WTO dispute settlement procedures in appropriate circumstances

April 21, 1998

ANNEX A

DEFINITIONS

The following definitions and criteria should guide expert scientific judgment in identifying, assessing and managing POPs.

A. Persistent Organic Pollutants (POPs): Substances that meet the criteria for persistence, toxicity, and bioaccumulation, and which are prone to long-range transport and deposition.

B. Half-life: The length of time required to reduce the concentration of a substance by 50% in a particular medium.

C. Long-Range Transport: Some substances have been detected in areas remote from their original source. Atmospheric transport is believed to be the primary mode of transport, even if marine transport cannot be excluded.

Deposition can occur on land or water, possibly affecting water, soil or sediment compartments. Factors influencing atmospheric transport are volatility and halflife in air. Substances have a potential for long-range transport and deposition if they meet the agreed upon criteria and if monitoring evidence demonstrates a link to distant and anthropogenic sources.

D. Persistence: A substance is considered to be persistent in a given medium if it resists physical, biological and chemical degradation. The persistence of a substance in a given medium is defined by its overall half-life in the medium. The half-life cannot be measured independently of the medium or without considering degradation/removal processes, such as hydrolysis, oxidation, photolysis, biodegradation, and evaporation. If a substance is persistent in a given medium, it has the potential for being persistent in the global environment. Its presence in the remote environment must be confirmed by direct observation or analysis.

E. Bioaccumulation: Bioaccumulation of a substance is its capacity to accumulate in the tissues of organisms, either through direct exposure to water, air or soil, or through consumption of food. It is calculated as the ratio, in a steady-state situation, or its concentration in the organism to the concentration in the medium to which this organism is exposed (termed the Bioaccumulation Factor, BAF).

When the intake in the organism is only due to the substance dissolved in the medium (generally water) the ratio is called the bioconcentration factor (BCF).

For some chemicals (e.g., non-polar hydrophobic organic substances) the tendency of the substance to bioconcentrate in tissue has been related to the substance’s hydrophobicity or lipophilicity. Therefore, the logarithm of the substance’s octanol-water partition coefficient (log Kow) has been used to estimate these substance’s bioaccumulation potential. For these substances and all other substances where there is no descriptor that can be used to estimate bioaccumulation potential, a directly measured BCF or BAF using a standard protocol or appropriate laboratory or field data should be used to estimate the bioaccumulation potential.

F. Toxicity: Substances are considered toxic if scientific assessments indicate concerns about their potential human health or environmental effects. Expert judgment should evaluate all available data relevant to various toxic endpoints.

Among the endpoints that should be considered are acute aquatic lethality, subchronic and chronic aquatic toxicity, acute wildlife toxicity, oral/dermal/inhalation toxicity in mammals and birds, carcinogenicity, mutagenicity, teratogenicity, reproductive toxicity, neurological toxicity, and immune system effects. Toxic effects must be demonstrated or expected to occur at the concentrations observed in the environment.

Annex B

Procedure for Identifying Further POPs Candidate Substances for International

Action

Recommendations

Recommendations which are scientifically defensible and supported by the following discussions are

 Substances that are proposed for evaluation as candidate POPs must be identified by using well-established scientifically based criteria. These criteria are to be used as guidelines by the proposing parties which will be required to present weight-ofevidence that the substance meets these criteria.

 Based on the goal of the POPs protocol, criteria are needed to identify substances that are a) persistent in the environment, b) able to bioaccumulate in food chains, and c) undergo long-range transport to remote regions.

 The substance must meet all three areas of the criteria simultaneously to become a

 candidate POP.

Determination that a substance results in toxic or adverse effects in remote regions and thus meets the definition of a POP requiring international action must be based on a full risk assessment taking into account predicted and measured exposure levels to humans and the environment in these remote regions and adverse effects that can occur at these exposure levels.

Rationale

The goal of the proposed procedure is to identify further candidate POPs substances that meet the definition of a POP namely that they a) are persistent in the environment to which they are introduced and transported, b) are able to bioaccumulate in food chains to cause unanticipated effects on higher trophic level organisms, and c) which after being introduced to the environment undergo long-range transport into remote regions d) where they can result in adverse or toxic effects on organisms directly exposed to the substance at environmentally relevant concentrations.

Based on this goal, well-established scientifically based criteria need to be established for determining if the substance meets the first 3 characteristics of a

POP. Once it is determined that the substance meets these criteria, then the probability that the substance is or can result in adverse effects on humans and the environment in these remote regions will be determined based on a full risk assessment. Only when the substance is determined to meet all components of

the definition of a POP will it go to the next stage - international action. This procedure is illustrated in Figure 1.

Specific recommended criteria values for the first three characteristics and guidelines for the risk assessment process are discussed in subsequent sections. However, there are some general principles that should be considered in developing the identification procedure. These are

 · In addition, to being based on scientific reasoning and evidence pertinent to that characteristic, any recommended criteria values needs to be shown to be relevant for distinguishing between already identified POPs and substances that are not

POPs.

 · Criteria should not be used as absolute bright lines but rather as guidelines

 recognizing that there is variability in experimental data.

· When a range of possible values is presented for the criteria, the final criteria value should be chosen to be as high as possible to ensure that the list of POPs for

 international action is limited to those which definitely have the same characteristics as currently recognized POPs and to ensure that the number of substances identified can be feasibly and practically managed internationally.

· Determination that the substance meets the proposed criteria and should proceed to full risk assessment should be based on best available data and weight of evidence.

 · In light of the precautionary principle, if there is potential based on toxicity data



 or field data for "serious or irreversible damage", and the evidence that the substance meets the criteria is not conclusive then the substance should be proposed for full risk assessment and becoming a candidate POP for international management.

· It must be recognized that although separate criteria are presented for determining persistence in each of the environmental media and for determining bioaccumulation potential, these criteria do not act independently in determining the potential for a substance to transport to, persist in and bioaccumulate in organisms in remote regions. Thus, even though a substance meets these criteria does not ensure that on detailed evaluation the substance will be identified as a

POP.

· The first part of the full risk assessment should focus on an evaluation of the fate processes for the substance using a full suite of physical, chemical, and degradation data and the use/release patterns of the substance among countries.

Only when this fate evaluation concludes that the substance undergoes long-range transport will it be considered to have meet the first three characteristics of a POP.

Although the first part of the evaluation process to identify candidate POPs can be conducted using bench scale laboratory test results, surrogate data, and in limited cases QSARs, the full risk assessment and the final determination of a substance as a POP for international action will require that data be presented on

actual environmental concentrations in these remote regions and exposure concentrations in wildlife and humans. In fact, evidence obtained via air and environmental sampling that a substance is undergoing long-range transport to these remote regions should be used to prioritize the evaluation of these substances as candidate POPs.

In addition, it is important that the identification procedure be conducted in an open and transparent manner. The document entitled "Process for Identifying

Candidate Substances for Regional Action under the Sound Chemical

Management of Chemicals Initiative" developed by the North American Working

Group on Sound Management of Chemicals (Commission for Environmental

Cooperation, 1997) contains many guidelines for how to maintain such an open and transparent process. These guidelines include 1) a method for the public to track progress on the evaluation of a substance, 2) list of questions that must be addressed by the Substance Selection Task Force (this task force technically reviews the dossier of information collated by the proposing party), and 3) method for publicly documenting decisions and supporting reasoning. In addition, these reports support the same criteria and criteria values recommended in this document.

In the proposal dossier it is critical to have a complete list of all physical, chemical, degradation and toxicological properties for the substance to be evaluated. This list will include not just those required to ensure that the substance meets proposed criteria. This information will be used in the detailed fate evaluation and subsequent full risk assessment.

Given emerging information on the effect of different use/release pattern on the potential for long-range transport (Webster et al. 1997, F. Wania, 1996), it is also critical to have detailed information on the use/release patterns by country and latitude and by the media into which the substance is released.

References

Commission for Environmental Cooperation. 1997. Process for Identifying

Candidate Substances for Regional Action under the Sound Management of

Chemicals Initiative. Draft Report to the North American Working Group on the

Sound Management of Chemicals by the Task Force on Criteria. Montreal,

Quebec.

Wania, F. 1996. Presentation at SETAC 1996 Annual meeting in Washington,

D.C. in Session on Persistent, Bioaccumulative, Toxic Substances.

Webster, E., D. Mackay, F. Wania. 1997. Environmental Persistence. Draft in

Technical review.

Figure 1: Flow Chart of POPs Identification Procedure

Persistence Criteria for Water, Soil and Sediment

Recommendations

Recommendations, which are scientifically defensible and supported by the following discussions, are

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· Criteria for each of the environmental compartments (i.e., water, soil and sediment) should take into account the different release and introduction patterns to these media as well as the different potentials for these compartments to act as sources for long-range transport or as transport media.

· Criteria values based on half-life of the substance should be a) 180 days for water, b) 360 days for sediment and c) 360 days for soil.

· The half-life of the substance in the environment should include consideration of the medium and all degradation and removal processes (e.g., hydrolysis, oxidation/reduction, photolysis, biodegradation and volatilization).

· If all data are not available for determining the half-life of the substance, then expert judgment should be used to determine if the substance is likely to meet or not meet the criteria. If the weight-of-evidence is not conclusive then the substance should be initially assumed to meet the criteria based on the precautionary principle and proceed to further evaluation, including measurement of all degradation and removal processes.

· Recommended criteria values must be demonstrated to differentiate between already identified POPs and substances that are not POPs.

· The final criteria value should be chosen as high as possible to 1) ensure that the candidate POPs have the same characteristics as currently recognized POPs and

2) ensure that all the candidate POPs can be managed internationally.

It should be noted that the Canadian Toxic Substance's Management Policy

(Env. Canada, 1995a), CMA's PTB Policy Implementation Guidance (CMA,

1996) and the CEC criteria document (Commission for Environmental

Cooperation, 1997) recommend similar criteria. Canada's TSMP and the CEC criteria document recommend a half-life criteria of 180 days for soil. International work to develop criteria for Persistent Organic Pollutants (POPs) being conducted under the auspices of UNECE (AEA/CS/RCEC 1995) has proposed lower half-life criteria for all three environmental compartments. These are a) 60 days for water, b) 180 days for soil and c) 180 days for sediment.

Rationale

The goal of the persistence evaluation is to determine if the substance under evaluation resides in the environment long enough to be a long-term source of the substance to the atmosphere for long-range transport. If the substance degrades rapidly after release to the environment then it would not be available

as a source to the atmosphere for long-range transport from the site of use/release to the Arctic regions. Because different media have different potentials for being sources to the atmosphere and have different potentials for being direct transport media, the half-life criteria in the different source media

(i.e., soil, water and sediment) will potentially be different. Note that these half-life criteria will focus on the persistence in the source environment. It is recognized that half-lives and thus persistence in the Arctic will be much longer because of the cold temperatures.

For example, soil and water are direct sources of the substance to the atmosphere. From water, volatilization is the primary loss mechanism to air and is influenced by both the concentrations of the substance in water and air as well as the substance's Henry's Law constant. In addition, the flow of water from one location to another can contribute to the long-range transport of the substance.

Soil can also be a source of the substance to the air but there is less loss by volatilization because of the high sorption of the substance to the soil particles because log Kow values are greater than 5 for these substances (See

Bioaccumulation discussion in subsequent section). This sorption onto the soil particles also increases the time that the substance remains in a specific soil and would be subject to biodegradation by microbes. Sediment is a source of the substance to water and thus is not a direct source to the atmosphere.

Furthermore, substances that are strongly sorbed to sediment particles, just as they are to soil particles, will not rapidly desorb into the water. Finally, sediment containing the substance will be buried over time, removing this as a source to the water column. For these reasons the half-life criteria for water must be shorter than or equal to that for soil the other source of the substance to the atmosphere. The half-life for sediment in turn should be longer than or the same as that for soil because it is not a primary source to the atmosphere. A further discussion of the relative importance of half-life and environmental residence time is given in Larson and Cowan (1996) and Shimp et al. (1990).

The actual recommended criteria values are based on a consideration of these arguments and a comparison to data on degradation rates for a substance. A compilation of Half-life values for Internationally recognized POPs is given in

Table 1. Based on the data in Table 1, the half-lives in water are greater than 180 days for all these substances except Endrin, the half-lives in Soil are also greater than 360 days for all substances except Aldrin and Dieldrin, and the half-life in sediment is greater than 1 year where there are data available. Because the use of the criteria values within the proposed procedure will be dependent on the substance half-life meeting only one of these three criteria, it can be concluded that these recommended criteria will be sufficient to meet the goals of the persistence evaluation. This conclusion is supported by the fact that 1) all the substances in Table 1 have at least one half-life that meets at least one of these criteria, 2) in most cases the half-lives greatly exceed the criteria indicating that they are conservative.

Table 1: Half-life values in Water, Soil and Sediment for Internationally

Recognized POPs (units of days unless otherwise specified)

Substance Water Soil Sediment Reference

Aldrin 760 > 20 Env. Canada 1995

Dieldrin

Chlordane

DDT

> 1460

7.6 yrs

> 4380

> 175

> 20 yrs

> 15 yrs > 1100

Env. Canada 1995

Env. Canada 1995

Env. Canada 1995

Mirex

Toxaphene

Hexachlorobenzene

Endrin

20 yrs

< 1

> 112

> 600 yrs

20 yrs

> 986

> 1460

> 600 yrs Env. Canada 1995

Env. Canada 1995

Env. Canada 1995

Env. Canada 1995

2,3,7,8 TCDD > 380 10 yrs > 365 Env. Canada 1995

PCBs Env. Canada 1995

Although some groups, notably the UNECE, have proposed much lower criteria values to ensure that any substances that could possibly exhibit any properties of a POP undergo evaluation, it is important in choosing the final criteria values to

consider the benefit versus cost of a long, inclusive list of candidate POPs and a short, exclusive list of candidate POPs.

Determining half-life values for substances that can be compared to these criteria will be very difficult since experimental measurement of half-lives longer that a few weeks is very difficult especially in water and sediment. Thus, it will be very important to use all evidence available and the weight-of-evidence to determine whether the substance's half-life in any of the media is likely to exceed the proposed criteria value. It is important to consider the characteristics of the medium and how this might affect the half-life, environmental conditions such as temperature and rainfall, and the full suite of degradation mechanisms such as hydrolysis, oxidation, photolysis and biodegradation. For this reason, half-life measurements may not be readily available, therefore expert judgment will be necessary to evaluate the accuracy and reliability of available data, determine which processes may contribute to degradation and their relative importance, and the contribution of environmental and media conditions and characteristics to degradation. Based on the expert evaluation and comparison of these data, a weight-of-evidence evaluation can be made of the likelihood that the substance's half-life in one of more of the media meets the criteria values. Types of data to be included in the evaluation would be results from QSAR model, data for analog substances, information on structural elements in substances that enhance or impede degradation, and results of field and laboratory tests.

When only screening biodegradation test data are available for a substance or this is considered to be the best data, there are proposed methods for extrapolating rates from these test to environmental rates (Federle et al., 1997;

Struijs and Berg, 1995; Boethling et al., 1995). However, these extrapolations are very inaccurate and therefore should only be used to identify possible substances for further evaluation. Before the full risk assessment and final judgment of whether a substance is a candidate POP for international action, high quality field and laboratory data will need to be verified or refute these estimates.

Reference

AEA/CS/RCE. 1995. Selection Criteria for Prioritizing Persistent Organic

Pollutants. Prepared for UNECE LRTAP Working Group on Persistent Organic

Pollutants.

Boethling, R.S., P.H. Howard, J.A. Beauman and M.E. Larosche. 1995. Factors for intermedia extrapolation in biodegradability assessment, Chemosphere

30:741-752.





Quebec.

CMA (Chemical Manufacturers Association). 1996. PTB Policy Implementation

Guidance: Product Risk Management Guidance for PTBs. Arlington, Virginia.

Environment Canada. 1995a. Toxic Substances Management Policy. ISBM 0-

662-61860-2.

Federle, T.W., S.D. Gasior, and B.A. Nuck. 1997. Extrapolating mineralization rates from the ready CO2 screening test to activated sludge, river water and soil.

Environ. Toxicol. Chem. 16: 127-134.

Larson, R.J. and C.E. Cowan. 1996. Quantitative Application of

Biotransformation Data to Environmental Risk and Exposure Assessments. Env.

Tox. and Chem. 14(8): 1433-1442.

Shimp, R.J., R.J. Larson and R.S. Boethling. 1990. Use of biodegradation data in substance assessment. Environ. Toxicol. Chem. 9:1369-1377.

Struijs, J. and R. van den Berg. 1995. Standardized biodegradability tests:

Extrapolation of to aerobic environments. Water Res. 29:255-262.

Bioaccumulation

Recommendations


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· Primary criteria for bioaccumulation for all chemicals is fish BCF > 5000

· Secondary criteria for non-polar, hydrophobic organic chemicals only is log

Kow >5 and <7.5, MW < 700 and substance is not metabolized.


(Env. Canada, 1995), CEC's criteria for identifying POPs (CEC, 1997), CMA's

PTB Policy Implementation guidance (CMA, 1996) and international work to develop criteria for Persistent Organic Pollutants (POPs) being conduced under the auspices of UNECE (AEA/CS/RCEC, 1995) have all proposed the BCF criteria of 5000 to identify these type of substances.

Rationale

The primary reason for including evaluation of bioaccumulation potential in the

POPs addition procedure is to identify substances which have the potential for higher exposure to higher trophic level organisms. The primary focus of the subsequent risk assessment will be on effects, if any, that would occur in higher trophic levels of the food chain as a result of this accumulation and transfer of substances via the food web. It must be recognized that bioconcentration is not an adverse effect or hazard in itself but rather an indicator that increased exposure may occur in higher trophic levels. The recommendation of BCF criteria greater than 5000 is based on several lines of evidence as outlined below.

First, a review of the reported and high quality measured BCF values for substances that have been internationally recognized as bioaccumulative and of concern and for which data support their potential for accumulation in higher trophic organisms (e.g., Suedel et al. 1994) was conducted (Table 1). This review indicated that all these substances have BCF values for the most part greater than 5,000 and these chemicals (e.g., PCBs, DDT, etc.) have log Kow values significantly greater than 5.0 and less than 7.5. Furthermore, these substances are primarily highly halogenated (i.e., chlorinated) organic compounds, for example, DDT/DDE, and PCBs. It should be noted that even for these

substances with the greatest evidence for bioacumulation and effect on top predators, there is substantial variability and uncertainty regarding the magnitude and existence of any effects.

Table 1. Log Kow and BCF values for Recognized Persistent and

Bioaccumulative Substances

Substance Log Kow BCF (wet)1

DDT and metabolites

Dieldrin

Chlordane

Mirex

Toxaphene

Hexachlorobenzene

Endrin

2,3,7,8 TCDD

6.5

5.4

6.0

7.1

5.9

5.2

7.0

>5.0

3,9000 to 91,000

2,100 to 34,700

7,100 to 37,800

18,100 to 20,400

19,500 to 70,800

7,800 to 22,000

4,200 to 49,800

7,900 to 344,000

PCBs 6.9

57,000 to 800,000

Aldrin 5.1 to 7.4

10,710

1. Source is Stephan 1993

Second, USEPA field studies on the Great Lakes (U.S. EPA 1993, Stephan

1993) indicate that the concentration of the substance in salmonid fish (i.e., top predator fish) through a four tier food chain is not significantly different from that of algae (>20%) until the BCF is greater than approximately 3,500 (i.e., log Kow

> 4.5). The factor increases to approximately 2.0 when the BCF is approximately

5,000 (i.e., log Kow is approximately 5.0). This means that at a BCF of 5,000 or log Kow of approximately 5.0, the top predator in a 4 tier food chain will have an internal concentration of the substance that is twice that of algae in the same system. For this reason a BCF of 5,000 indicates the level at which food chain transfer becomes a significant part of exposure in these high predators. Finally,

these conclusions are in agreement with other literature (e.g., Thomann et al.

1992, Owens et al. 1994, Porte and Albaiges, 1993) describing food chain accumulation in the field.

Third, food web models that have been developed and validated (e.g., Thomann,

1989; Barber et al., 1991; Gobas and Mackay, 1987) can be used to evaluate the contribution food makes to exposure in various predatory organisms. The results of one such model (Barber et al. 1991) which is used by the USEPA is shown graphically in Fig. 1.

Finally, Gobas et al. (1993) have shown that the contribution from uptake via the gut as compared to uptake from surfaces like the gills is not significant until log

Kow is greater than 5.0.

Fig. 1. Percent of Exposure from Food for Plankton Feeder and Salmonid Fish, which feeds on Plankton Feeder. Based on Barber et al. (1991) model.

Therefore, based on these lines of evidence, the recommended criteria value is that the BCF in fish be greater than 5000.

Secondary BCF Criteria for Non-Polar, Hydrophobic Organic Chemicals of log

Kow > 5 and < 7.5 and Molecular Weight < 700

Testing to measure BCF can result in unnecessary animal testing and high costs

($30,000 to $40,000 (US) for a typical chemical), so there is the impetus to use surrogates for BCF for substances for which they exist. For non-polar, hydrophobic organic chemicals, log Kow is often used as a surrogate measure of

BCF. However, for many chemicals (e.g., esters, aldehydes, anilines, amines and phenols), log Kow is not a surrogate measure for BCF. This is due to the fact that for many classes of substances 1) there are recognized experimental difficulties in measuring Kow, and 2) there are inaccuracies in the computation methods for estimating Kow. For example, the shake flask method for measuring log Kow (OECD 1981) is not applicable to surface active or ionizable substances and is restricted to single pure substances.

There are several accepted relationships for calculating BCF from log Kow values for non-polar, hydrophobic organic chemicals that have been and continue to be used in regulatory applications and which are based on good databases (Table 2). Furthermore, as shown in Fig. 2, they would yield similar

BCF values for each log Kow value up to a log Kow of 6. For substances with log

Kow values greater than 6, the BCF values appear to decrease with increasing log Kow. Curvilinear relationships (e.g., Bintein et al., 1993) have been proposed to predict BCF for log Kow values greater than 6. However, because of experimental difficulties in measuring BCF values for substances in this log Kow range, these QSARs and the predicted BCF values should be used with caution.

Because of the decrease in BCF with increasing log Kow, an upper cut-off criteria for log Kow is proposed. Based on experience with bioaccumulative substances

(e.g., Table B.1) and the curvilinear QSARs (e.g., Bintein et al., 1993), the upper bound appears to be approximately a log Kow of 8.

Table 2. Commonly Used QSARs for Estimating BCF.

Relationship R2 Reference log BCF = 0.85log Kow - 0.7

0.95

BCF = 0.048 Kow 0.97

Veith et al. 1979 and EC

1996

Mackay (1982)

log BCF = 0.79 log Kow - 0.4

log BCF = 0.910 log Kow - 1.975 log

(6.8E-7 Kow +1) -0.786

0.93

0.95

Veith and Kosian (1983)

Bintein et al. 1993

Fig. 2. Comparison of QSARs

Because BCF is the primary criteria, the choice of what log Kow criteria to use for non-polar, hydrophobic chemicals is most appropriately discussed by considering what log Kow values, based on the QSARs which are used in the US, EU, and

Canada, would be equivalent to the proposed BCF criteria of 5,000 (Table 3).

Table 3. Log Kow values Equivalent to BCF of 5000 for Commonly Used QSARs for Estimating BCF.

Relationship log Kow for

BCF = 5000

Reference log BCF = 0.85log Kow - 0.7

5.2

Veith et al. 1979 and EC

1996

BCF = 0.048 Kow log BCF = 0.79 log Kow - 0.4

5.0

5.2

Mackay (1982)

Veith and Kosian (1983) log BCF = 0.910 log Kow - 1.975 log

(6.8E-7 Kow +1) -0.786

5.0 and 7.5

Bintein et al. 1993

It has also been determined that substances with MW > 700 are too large to cross membranes into the organism (EEC 1993). Thus, the full recommendation for the secondary criteria would be that the substance in addition to having log

Kow values between 5 and 7.5 would also have a MW < 700.

Limitations of Log Kow as Secondary Criteria

Although it is possible to use these QSARs to estimate BCF for non-polar organic substances, it is important to recognize that none of these QSAR relationships account for metabolism. Many substances are metabolized. Metabolism can result in measured BCF values for these chemicals that are significantly less than those that would be determined from the log Kow. For example, the BCF for pentachlorophenol is calculated to be 5,500 but the measured value is 195

(Kukkonen and Oikari 1988) and for dodecylbenzene is calculated to be

10,232,930 versus a measured value of 25 (Werner and Kimerle 1982). Other examples are given in Table 1 of ECETOC (1996) and the dissertations of Sijm

(1992) and De Wolf (1992). Thus, log Kow should not be used as the sole secondary criteria. Instead information on pharmacokinetics and metabolism should be considered to determine if the log Kow criteria are likely to lead to an over estimation of bioaccumulation potential. If this evidence exists and the log

Kow is in the range of 5 to 7.5 then a bioaccumulation measurement should be made and the primary criteria of BCF > 5000 used to determine if the substance in a candidate POP.

Although the log Kow is a scientifically supportable surrogate for BCF for nonpolar, hydrophobic chemicals, for other types of organic chemicals, the only scientifically defensible option is to measure the BCF value. However, it is important to recognize that research is ongoing to develop surrogates and methods for estimating the BCF for other classes of chemicals. Some of the other surrogate measures, which are described in ECETOC (1996), include

water solubility, and molecular connectivity indices. In addition, in vitro methods for measuring BCF, such as semi-permeable membrane devices (SPMDs), are being evaluated. These methods potentially could be used to rapidly and inexpensively measure surrogate BCF values for a wide range of chemicals.

Finally, there are promising new short-term bioconcentration test methods being developed (e.g., Gobas and Zhang 1992, de Magaad et al. 1995) that could make bioaccumulation testing of substances easier, faster and less costly.

High-Quality BCF Values

When evaluating whether a substance meets the criteria for bioaccumulation and for choosing data for the evaluation of the proposed criteria values, it is important to use the highest quality and most appropriate data available not necessarily the highest reported value. The hierarchy of data quality in descending order would be 1) data collected recently under GLP using well recognized protocols (e.g.,

OECD 1992, ASTM 1993), 2) data collected recently using well recognized protocols but not necessarily GLP, 3) data judged by experts to be of acceptable quality, 4) information on bioaccumulation potential for analog chemicals, and 5) log Kow, QSAR, or other estimated values. Data quality assurance requirements include but are not limited to consideration of whether the 1) BCF was determined for steady-state conditions, 2) substance could have had an adverse effect (i.e., toxic effect) on the organism, and 3) concentration of the substance in the water was measured and remained relatively constant during exposure.

Weight-of-Evidence

It is suggested that rather than a single measured BCF value that weight-ofevidence be used to support the conclusion that BCF for a substance is likely to be greater than or less than 5,000. Testing of BCF if not already conducted should only be done after it is determined that evidence is insufficient to make this determination. This weight-of-evidence could include measured BCF values from all sources with quality judged as indicated in the previous paragraph, BCF values for analog chemicals, evidence of metabolism, whether the substance is halogenated and to what degree, and other physical/chemical descriptors such as molecular weight that influence the potential for bioconcentration. It should also be recognized that the presence of halogenation in the substance does not

automatically imply that the substance will be persistent or bioaccumulative. As shown in Fig. 3, the bioaccumulation potential of halogenated substances is dependent on the organic molecule to which the chlorine molecules are attached as well as the number of chlorine molecules.

Fig. 3. Plot of log Kow as a function of the number of chlorine atoms per molecule. The shaded area represents hydrophobic, bioaccumulative chemicals.

From Mackay and DiGuardo 1995

REFERENCES

AEA/CS/RCEC. 1995. Selection Criteria for Prioritizing Persistent Organic

Pollutants. Prepared for UNECE LRTAP Working Group on Persistent Organic

Pollutants.

ASTM. 1993. Standard Practice for Conducting Bioconcentration Tests with

Fishes and Saltwater Bivalve Molluscs. ASTM E 1022-84 (reapproved 1988). In:

ASTM Standards on Aquatic Toxicology and Hazard Evaluation, American

Society of Testing and Materials, Philadelphia, PA, pp. 356-372.

Barber, M.C., L.A. Suarez and R.R. Lassiter. 1991. Modeling bioaccumulation of organic pollutants in fish with an application to PCBs in Lake Ontario salmonids.

Can. J. Fish. Aquat. Sci. 48:318-337.

Bintein, S., J. Devillers and W. Karcher. 1993. Nonlinear dependence of fish bioconcentration on n-Octanol/water partition coefficients. SAR and QSAR in

Env. Res. 1:29-39.





Quebec.


Guidance: Product Risk Management Guidance for PTBs. Arlington, Virginia. de Magaad, G.J., M. Overdijk, D.T.H. M. Sijm, A. Opperhuizen. 1995.

Determining bioavailable PAH fraction during static fish exposure using a florescent quenching method. Abstract from the Society of Environmental

Toxicology. 16th Annual Meeting. Vancouver, Canada. pp. 64 de Wolf, W. 1992. Influence of biotransformation on the bioconcentration of chemicals in fish. Ph.D. Dissertation. University of Utrecht, The Netherlands.

EC. 1996. Technical Guidance Manual

ECETOC 1996. The role of bioaccumulation in environmental risk assessment:

The aquatic environment and related food webs. Brussels, Belgium.

EEC. 1993. Technical guidance documents in support of the risk assessment directive (93/67/EEC) for substances notified in accordance with the requirements of Council Directive 67/548/EEC. Brussels, Belgium.

Environment Canada. 1995. Toxic Substances Management Policy. Ottawa,

Ontario, Canada.

Gobas, F.A.P.C. and X. Zhang. 1992. Measuring bioconcentration factors and rate constants of chemicals in aquatic organisms under conditions of variable water concentrations and short exposure time. Chemosphere 25:1961-1971.

Gobas, F.A.P.C., X. Zhang, and R. Wells. 1993. Gastrointestinal Magnification:

The mechanism of biomagnification and food chain accumulation of organic chemicals. Environ. Sci. Technol. 27: 2855-2863.

Gobas, F.A.P.C., and D. Mackay. 1987. Dynamics of hydrophobic organic chemicals in fish. Environ. Toxicol. Chem. 6:495-504.

Kukkonen, J. and A. Oikari. 1988. Sulphate conjugation is the main route of pentachlorophenol metabolism in Daphnia magna. Comp. Biochem. Physiol.

91C:465-468.

Mackay, D. 1982. Correlation of bioconcentration factors. Env. Sci. Technol. 16:

274-278

Mackay, D. and A. DiGuardo. 1995. Organochlorine chemicals in Great Lakes

Ecosytems. Ecological Applications 5(2) 301-304.

Nendza, M. (1991) "QSARs of bioconcentration: Validity Assessment of log

Pow/log BCF correlations" In; Nagel, R. and R. Loskill (ed). Bioaccumulation in

Aquatic systems - Contributions to the assessment. pp. 43-66. VCH -

Verlagsgesellschaft, Weinheim, Germany 239 pp.

OECD 1981. Guidelines for the testing of chemicals, 107, Partition coefficient (noctanol-water). OECD. Paris, France.

OECD. 1992. Bioconcentration: Flow-through fish test. OECD Guidelines for

Testing of Substances. Draft Guideline 305. 23 pp. December 1992.

Owens, J.W., Swanson, S.M., and D.A. Birkholz. 1994. Bioaccumulation of

2,3,7,8-tetrachlorodibenzo-p-dioxin, 2,3,7,8-tetrachlorobenzofuran, and extractable organic chlorine in a Northern Canadian river system. Environ.

Toxicol. Chem. 13:343-354.

Porte, C. and J. Albaiges. 1993. Bioaccumulation patterns of hydrocarbons and polychlorinated biphenyls, in bivalves, crustaceans, and fishes. Arch. Environ.

Contam. Toxicol. 26:273-281.

Suedel, B.C., J.A. Boraczek, R.K. Peddicord, P.A. Clifford and T.M. Dillon. 1994.

Trophic transfer and biomagnification potential of contaminants in aquatic ecosystems. Rev. Environ. Cont. Toxicol 136: 21-89.

Thomann, R.V. 1989. Bioaccumulation model of organic chemical distribution in aquatic food chains. Environ. Sci. Technol. 23:699-707.

Thomann, R.V., J.P. Connolly, and T.F. Parkerton. 1992. Environ. Toxicol.

Chem. 11:615-629.

U.S. EPA. 1993. Great Lakes Water Quality Initiative Criteria Documents for the

Protection of Wildlife. EPA-822-R-93-007.

Veith, G.D., D.L. Defoe and B.V. Bergstedt. 1979. Measuring and estimating the bioconcentration factor of chemicals on fish. J. Fish. Res. Board Can. 36:1040-

1048.

Veith, G.D. and P. Kosian. 1983. Estimating bioconcentration potential from octanol/water partition coefficients. In: Mackay, D., Paterson, S., Eisenreich, S.J.,

Simons, M.S. (eds). Physical behavior of PCBs in the Great Lakes, Ann Arbor

Sciences Publishers, Ann Arbor, P. 269-282.

Werner, A.F. and R.A. Kimmerle. 1982. Uptake and distribution of C12 alkylbenzene in bluegill (lepomis macrochirus). Environ. Toxicol. Chem. 1:143-

146.

Long-range Transport Criteria

Recommendations






· Half-life in air is > 2 days

· VP < 13 Pa

 · documented evidence that the substance is found in remote Arctic regions due to long-range transport.


(Env. Canada, 1995a), CEC's criteria for identifying POPs (CEC, 1997) and international work to develop criteria for Persistent Organic Pollutants (POPs) being conduced under the auspices of UNECE (AEA/CS/RCEC 1995) have all proposed the air half-life criteria of 2 days to identify these type of substances.

CMA's PTB Policy Implementation Guidance (CMA, 1996) recommends an air half-life value of 5 days.

In several of the documents discussing the criteria for identifying potential POPs

(e.g., UNECE report, July 1995 and Ad Hoc Preparatory Work Group on POPs,

Dec. 1995) a Vapour Pressure (VP) cut-off value is also included in the list of criteria; however, a vapour pressure criteria was not part of the Canadian Toxic

Substances Management Policy (Env. Canada, 1995) nor of the CMA's PTB

Policy Implementation Guidance (CMA, 1996).

Rationale

The focus of determining transport criteria values is to identify substances "may have the potential for long-range transport and contribute to atmospheric deposition". The main focus for these criteria are on ensuring that the substance does travel in the atmosphere for long distances and does deposit back to the earth at these distant locations.

Air Half-life Criteria

The primary purpose of the air half-life criteria is used to identify substances that do not degrade rapidly in the atmosphere and thus could be transported long distances and then redeposited to the earth. The recommended air half-life is based on several lines of evidence as outlined below.

First, a review of reported and high quality measured air half-life values for substances that have been internationally recognized as POPs compared to those of other representative substances that are not POPs. Table 1 contains this summary. Based on these data and others presented in Env. Canada

(1995b), there appears to be no single air half-life value that can be used to distinguish between the POPs and other substances. However, when data is available the POPs generally have half-lives of a few days or less with the notable exceptions of Dieldrin and Hexachlorobenzene. This is further supported by the fact that many characteristics of the POPs substance contribute to longrange transport besides air half-life. These include log Kow or sorption constants to particulates and the media into which the substance is released.

Table 1: High Quality Air Half-life values for Internationally Recognized POPs and Other Representative Substances that are not POPs.

Substance Measured Half-life Predicted Half-life Reference

Dieldrin 1 day Env. Canada (1995b)

Chlordane

DDT

Endrin

PCDDs and PCDFs

PCBs 3-21 days

8 days

2-4 days

7

1-15

Env. Canada (1995b)

Env. Canada (1995b)

Env. Canada (1995b)

Env. Canada (1995b)

Anderson and Hites,

(1996)

1,2,3,4 TCDD 9.7 days Brubaker and Hites,

(1997)

Propanol 1.6 days 0.728

Atkinson (1989) and

SRC (1995)

Formaldehyde 0.9

0.089

Atkinson (1989) and

SRC (1995)

CFC's 11,800 >13,000 Howard (1976) and

WMO (1991)

Second, comparison of travel times in air to proposed air half-life criteria.

According to Bidleman, T. (1996) the travel time of a parcel of air during episodic events in which air masses can be tracked from the Japan, China, Middle of

Russia and other parts of Asia to the sub Arctic region of Canada has been measured to be approximately 5 days. Thus, to allow for degradation of the substance in the air during transport, an air half-life value of approximately 2 days or less would result in the substance concentration being reduced by at least half during this average transportation time.

Thus, based on the data compilation and the travel time in air data, an air half-life of a few days or less (less than or equal to 5 days) is reasonable as a criteria value. However, the ability of the substance to undergo long-range transport will depend on the entire suite of characteristics of the substance not just the air halflife value. Thus, the final determination of whether the substance meets the definition of undergoing long-range transport can not be based solely on whether the substance meets these guideline criteria which will indicate that the substance is similar to other substances that have been shown by monitoring data to have undergone long-range transport. Instead the final determination should be based on an evaluation of potential for long-range transport that includes all properties of the substance considered together and monitoring data documenting the presence of the substance in remote Arctic regions.

The choice of which data to use to compare to the criteria values is also critically important. As a compilation of all available air half-life values will illustrate, there is considerable variability in the measured and estimated values. Variability in air half-life determinations is due to both variability that results from experimental methods as well as the variability in environmental parameters that affect the measured half-lives. The precision and accuracy of most physical property determinations and estimates has improved significantly in the past 25 years due in part to advent of GLP operating procedures, automated steps in experimental determinations, and increasing knowledge about environmental processes. With

regard to air half-life it is important to recognize that it is very difficult to experimentally determine the air half-life for substances that sorb to the experimental chamber. The POPs of interest all have large sorption constants as indicated by the fact that they have log Kow values greater than 5. Furthermore, the rate can be catalyzed by material in the environment or in aerosol particulates. Thus, review of any data used for comparison to the air criteria should first include an expert evaluation of the quality of the data and the likelihood that experimental artifacts such as sorption to the experimental apparatus could have influenced the measurements. According to Atkinson

(REF), the accuracy of measurements of reactivity with hydroxyl radicals can vary by 20% to 30%.

Thus, in determining whether the substance under evaluation is likely to meet the air half-life criteria, it is important to conduct an expert review of any measurement and to compare any reported measurements to those determined using QSARs and those for analog substances. Among the high quality QSARs that can be used in this evaluation are those of Atkinson (1987, 1988) which are programmed into the Meylan and Howard AOP program (Meylan and Howard,

1993; SRC, 1995).

Vapour Pressure Criteria value

A criteria value based on vapour pressure is used to eliminate from the selection process any substances that are clearly volatile but would not be deposition problems nor would they meet the subsequent criteria for a potential POP. For example, CFCs and similar substances would be captured in this initial criteria screen if only the half-life criteria screen was used. It is recognized that substances like CFCs with vapour pressure > 1000 Pa are considered so volatile that they will remain predominantly in the atmosphere and not transfer to the condensed phase and deposit on the earth. As illustrated in Table 1, the vapour pressure values for those substances which are proposed as POPs are significantly less than those of CFCs. For example, the vapour pressures for the proposed POPs are all less than 0.2 Pa. Thus, the criteria value should be placed within this range of 1,000 to 0.2 Pa. Because POPs are semi-volatile substances, the proposal is to use the range of based on the work of Wania and

Mackay (1996). In this paper these authors show that substances that are have high preferential transport to and deposition and accumulation in the polar latitudes have log Kow values greater than 5 and have subcooled vapour pressures in the range of 1 to 10-2 Pa.

Table 1. Vapor Pressure (VP) values for proposed POPs and for CFCs.

Substance VP (Pa) Source

PCBs (2 to 8 chlorine) dioxins (1 to 8 chlorine)

0.2 to 0.00003

Wania and Mackay, 1993

Mackay et al. 1992 0.12 to 1.1E-10 (decreases with increasing chlorination

Furans (2 to 8 chlorine)

Aldrin

Dieldrin

DDT

Endrin

Chlordane

Hexachlorobenzene

Mirex

0.00039 to 5.0E-10 (decreases with increasing chlorination)

0.01

0.005

0.00002

0.003

0.0011

0.0015

0.0001

Mackay et al. 1992

Hinckley et al., 1990




Toxaphene

Heptachlor

0.002

0.01



CFC ~ 340000 Mackay et al., 1993

References

Anderson, P.N. and R.A. Hites. 1996. Environ. Sci. Technol. 30:1756-1763.




Atkinson, R. 1987. A structure-activity relationship for the estimation of rate constants for the gas-phase reactions of OH radicals with organic compounds.

Int. J. Chem. Kinetics 19:700-828.

Atkinson. R. 1988. Estimation of gas-phase hydroxyl radical rate constants for organic chemicals. Env. Chem Toxicol. 7: 435-442.

Atkinson, R. 1989. J. Phys. Chem. Ref. Data. Supp. 3, 18-881.

Bidleman, T. 1996. Presentation at SETAC 1996 Annual meeting in Washington,

D.C. in Session on Persistent, Bioaccumulative, Toxic Substances.

Brubaker, W.W. and R.A. Hites. 1997. Environ. Sci. Technol. 32:1805-1810.





Quebec.


Guidance: Product Risk Management Guidance for PTBs. Arlington, Virginia.

Environment Canada. 1995a. Toxic Substances Management Policy. Ottawa,

Ontario, Canada.

Environment Canada. 1995b. Toxic Substances Management Policy:

Persistence and Bioaccumulation Criteria. Ottawa, Ontario, Canada.

Hinckley, D.A., T. F. Bidleman, and W.T. Foreman. 1990. Determination of vapour pressures for nonpolar and semipolar organic compounds from gas chromatographic retention data. J. Chem. Eng. Data. 35: 232-237.

Mackay, D., W-Y Shiu, and K-C Ma. 1992. Illustrated handbook of physicalchemical properties and environmental fate for organic chemicals: Vol. II

Polynuclear Aromatic hydrocarbons, polychlorinated dioxins and dibenzofurans.

Lewis Publishers. Ann Arbor, Michigan.

Mackay, D., W-Y Shiu, and K-C Ma. 1993. Illustrated handbook of physicalchemical properties and environmental fate for organic chemicals: Vol. III Volatile organic chemicals. Lewis Publishers. Ann Arbor, Michigan.

Meylan, W.M. and P.H. Howard. 1993. Computer estimation of the atmospheric gas-phase reaction rate of organic compounds with hydroxyl radicals and ozone.

Chemosphere 26:2293-99.

SRC (Syracuse Research Corporation) 1995. User's Guide for AOPWIN.

Syracuse Research Corporation, Environmental Science Center, Merrill Lane,

Syracuse, NY 13210

Wania, F. and D. Mackay. 1993. Global fractionation and cold condensation of low volatility organochlorine compounds in polar regions. Ambio 22:10-18.

WMO. 1991. Scientific Assessment of Ozone Depletion.

Risk and Hazard Evaluation

Recommendation

Recommendations which are scientifically defensible and supported by the following discussions, are











· Because the meeting of the criteria does not guarantee that a substance will be a

POP, first part of evaluation should be to look at fate and ensure that substance once all characteristics are considered simultaneously that the substance does undergo long-range transport and thus meets definition of POP.

· Focus of risk assessments is on determining potential for adverse effects in remote, Arctic regions. Thus, assessment process and endpoints should reflect the particular characteristics and considerations of these environments.

· In addition to determining if there is a potential for adverse effects from current exposures in these remote regions, the assessment should attempt to evaluate long-term exposures if current release patterns are maintained, if anticipated increases in releases occur and if all releases are terminated as ways of bounding the potential for adverse effects in the future based on current practices or potential management.

· Risk assessment procedure should be transparent and based as much as possible on harmonized risk assessment procedures under development or in use in international arenas (i.e., IPCS, and OECD).

· Standard set of assessment endpoints, questions and scenarios should be developed to guide the risk assessment process and thereby focus it on the areas and effects of greatest concern.


(Env. Canada, 1995), CMA's PTB Policy Implementation Guidance (CMA, 1996),

CEC's criteria for identifying POPs (CEC, 1997), and international work to develop an identification for Persistent Organic Pollutants (POPs) being conduced under the auspices of UNECE (AEA/CS/RCEC 1995) have all proposed that a full risk assessment be included in the final part of the identification procedure.

Rationale

The last part of the evaluation process for a substance to determine if it is a candidate POP for international action is a full risk assessment. In conducting this evaluation, there are several principles and points that need to be addressed to ensure that the risk assessment is properly focused on the main issues of concern and to ensure that the final results of the risk assessment will provide the necessary information to guide risk management of the substance if this is

found to be appropriate. We offer the following points for inclusion in this discussion.

The first part of the risk assessment process needs to focus on determining, based on consideration of all the physical, chemical, and degradation properties and the release/use patterns, whether the substance does indeed meet the full definition of a POP. This is a critical part of the assessment and the first question that needs to be addressed. This assessment will use the concurrence between monitoring data in the remote Arctic regions and modeling results which provide insights into the most important processes contributing to the long-range transport to support this conclusion.

The second part of the assessment will focus on determining if the substance is currently causing or could in the future cause impacts on animals and/or humans that live in these remote Arctic regions. Thus, an important part of the guidance for those people preparing this risk assessment is a specific set of questions that should be addressed in the assessment. These questions would, for example, focus the risk assessor on which environmental organisms and effects should be assessed. These questions and the answers are also a good method to use as part of an open and transparent risk assessment and decision making process.

Although other risk assessments that have been conducted for these substances should be taken into consideration and some of the data used in this assessment, it is important to recognize that only assessment(s) that focus on the Arctic regions and a global assessment of the consequences of releases/uses should be used in making the final decision.

Environmental fate models used in the assessment once verified using available monitoring data should also be used to project what could happen in the future under various potential release/use scenarios. The specification of these release/use scenarios could be part of the guidance given to the risk assessors.

For example, future scenarios might focus on what would happen to exposure concentrations in the remote Arctic regions if all releases/uses were to discontinue, continue at current levels, increase by some specified fraction, etc.

These future exposure scenarios could then be used to determine if or when in the future if ever, exposure concentrations would reach critical levels. This

information could also be used to dimension the urgency of control measures.

These same fate models can also be used to determine which releases/uses and in which locations (e.g., latitudes and/or countries) contribute the most to the existing and future exposure levels in these remote Arctic regions. This information will be particularly useful in assisting risk managers in developing management plans, if required.

Within this risk assessment process, there is clearly a need to address issues around transparency and consistency and the need for peer review of any assessments that are used in the decision making. Although there are differences in the approaches advocated among the European Union (EC 1996,

EEC 1993), U.S. EPA (EPA documents, Maurice etc.?), Environment and Health

Canada (Env. Canada, 1997; Health Canada???) and OECD's SIDs program

(OECD 1996), the effect of these differences on the assessments is not likely to be large in most cases because 1) the focus will be on the Arctic region and environmental conditions used will reflect those conditions and not that of these particular regions, 2) the differences between the assessment approaches are not as important at the higher tiers where measured environmental concentrations and higher level toxicity test data are available, and 3) expert judgment is always factored into these higher level assessments. Most likely the major differences between parties involved in the assessments or the decision making process will be on 1) what to protect and 2) the level of protection to ensure. These issues will need to be addressed in dialog and guidance between the assessors and stakeholders. It is also recognized that part of the goals of

Chapter 19 of Agenda 21 is to strengthen technical capability in risk assessment methodology and to promote harmonization and transparency in risk assessment methods. This harmonization process and the experts involved in it could be used to address technical issues that arise in the assessment process and provide peer review. Among the issues that will need to be addressed are 1) data extrapolation, 2) appropriate models and use of models, 3) validity of data used in the assessment, and 4) the appropriateness and methods for addressing uncertainty.

Industries have a large amount of experience in conducting risk assessments of new and existing ingredients and products often on a global scale or in several geographies. This expertise is offered to assist in working through both technical and transparency issues in the risk assessment process. Industry is also recognized as a leader in developing and promoting improvements in risk assessment methods and data interpretation (e.g., Cowan et al., 1995).

References

Cowan, C.E., D.J. Versteeg, R.J. Larson and P.J. Kloepper-Sams. 1995.

Integrated Approach for Environmental Assessment of New and Existing

Substances. Reg. Toxicol. Pharm. 21:3-31.

EC. 1996. Technical Guidance Manual

EEC. 1993. Technical guidance documents in support of the risk assessment directive (93/67/EEC) for substances notified in accordance with the requirements of Council Directive 67/548/EEC. Brussels, Belgium.

Environment Canada 1997. Environmental Asessments of Priority Substances

Under the Canadian Environmental Protection Act. Guidance Manual Version 1.

Ottawa, Ontario. EPS/2/CC/3E

OECD. 1996. SIDS Manual. Paris, France EXCH\MANUAL\96COVER.DOC/May

1996

Risk Management of POPs

Recommendations

Recommendations which are supported by the following discussions are

 · The type of risk management actions that are taken to reduce the risk of POPs identified for international action must consider the results of the risk assessment, the type of products that contain the POP (e.g., industrial chemicals, pesticides, and contaminants in industrial products), and other information (e.g., feasibility of

 pollution prevention technology, availability of alternatives, and economics).

· These management actions should be based on voluntary agreements whenever possible with supporting regulatory measures, as appropriate.

Rationale

Industry supports the following approach to risk management of POPs that have been identified for international action.

First, risk management decisions regarding specific POPs need to take into account the following principles and information

 · the level of risk that is present, i.e., the risk management action should be

 commensurate with the level of risk indicated by the risk assessment

 · the uses or contexts of uses that result in the greatest contribution to the risk

· feasibility and practicality of engineering options





· social acceptance of various management options

· analysis of advantages and limitations of each potential management option

 · analysis of cost-effectiveness and the relationship between costs and benefits of

 each potential management option

· proportionality of risks from each source and the cost and effectiveness of each

 management option

· risks associated with substitution by alternative chemicals





· the full life-cycle of the substance including production, use and disposal

· methods for avoiding distortion in trade and competition

 · legal constraints and enforcement mechanisms

 Second, risk management of POPs must consider all available management options, such as

 · Presenting information to workers and users of presence of POP and safe





 handling via classification, labeling, and/or MSDSs.

· application/installation of best available techniques for reducing or preventing emissions

· application of best environmental practice (BEP), including safe handling, minimization of exposure, and/or promotion and use of alternative products or substances

· use limitations

Risk management option of substitution as well as bans or phase-outs should be considered as the last resort options and only be applied if the evaluation process demonstrates that these chemicals pose "unreasonable and otherwise unmanageable risks to human health and the environment ... and whose use can not be adequately controlled" (see Agenda 21, Chapter 19, paragraph 44).

The chemical industry also urges close cooperation between interested stakeholders, governments and international organizations so that the choice of management options will have wide support and can be conducted in the most effective way. For this same reason, industry urges the use of mutually agreed to voluntary measures to accomplish the risk management goals. Only when the voluntary measures are not feasible or when regulatory actions need to be taken to ensure that voluntary actions can happen in the most effective manner is regulatory action recommended.

In addition, it is important that the risk management process and the rationale for the chosen risk management options be presented in an open and transparent manner that is readily understandable to all stakeholders. Part of this open and transparent process should include peer review following accepted conventions and guidelines.

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