Development of Science-based Criteria for Identifying Further POPs, UK, June 1996

Paper for IFCS meeting, Manila, 20-21 June 1996, Agenda Item 5

Discussion Paper on the Development of Science-based Criteria for Identifying Further POPs

Presented by the United Kingdom

Click to download: Development of Science-based Criteria for Identifying Further POPs, United Kingdom, June 1996, 19K/8K, English

Introduction

Decision 18/32 identified twelve substances, or groups of substances, as a list of POPs for which international action is warranted. However, it is highly unlikely that these twelve represent the only organic substances released into the environment that have the potential to cause adverse effects in humans and/or the environment at considerable distances from their point of release. As scientific knowledge increases, so further substances will be identified as potential candidates for inclusion within the process.

There is therefore a need for the development of objective science-based criteria to judge the strength of the case for, or against, the inclusion of any given candidate POP. This discussion paper outlines the approach being discussed in the United Nations Economic Commission for Europe (UNECE) Convention on Long Range Transboundary Air Pollution (LRTAP) as a possible means of achieving this, and compares it with the perceived needs of the UNEP/IFCS process.

First it is important to define what we mean by a selection procedure. There are normally two stages in such a process:

screening potential candidates: a priority setting stage which can be made fairly mechanistic, and therefore relatively simple;
deciding whether or not the candidate is a POP: this involves a detailed expert consideration of all the available data on the candidate, and is therefore difficult to define precisely, although it can be said to involve some form of risk characterisation.

Once a POP has been selected, the next step is to decide on the appropriate measures to control the POP: this involves consideration of the socio-economic factors involved in the various control options, e.g. the availability of affordable alternatives, and is beyond the scope of this paper.

UNECE

Such a stepwise procedure is being developed for the possible POPs Protocol in the UNECE Convention on LRTAP. It is envisaged that countries would propose additions to the Protocol, demonstrating first to the other parties that the substance in question appears to match the characteristics of a POP, i.e. its atmospheric half life and volatility suggest long range atmospheric transport is possible (or monitoring evidence confirms that it does occur), and a cursory examination of the data on bioaccumulation potential and persistence suggests the substance may be of concern. In UNECE, this procedure is thought of as two separate stages, although both are relatively quick and easy, and are therefore considered to be part of the same stage for the purposes of this paper. This first stage serves to focus the later, more resource intensive efforts to those substances most likely to meet the more stringent second stage criteria.

The proposing country would then be responsible for providing all the available information on the substance to a group of experts, who would peer review the evidence and advise the negotiating body of the Protocol as to whether they thought the substance should be defined as a POP.

The second stage differs from the first in that it must contain a detailed, internationally acceptable risk characterisation. There are a number of possible sources for such a risk characterisation, e.g. an up to date IPCS Environmental Health Criteria document, an OECD or EU risk assessment, or a national assessment of similar standard. It is unlikely that these types of study would focus explicitly on the particular risks of interest to UNECE, i.e. risk to man and the environment as a result of long range transboundary air pollution. However, they provide authoritative assessments in a number of vital areas:

the quality of individual studies (there are often contradictory or misleading data in the scientific literature);
the persistence of the substance in air, water, and biological systems;
The potential for bioaccumulation (and, if possible, biomagnification);
the potential for adverse effects to man and the environment, resulting from chronic low level exposure.

Such assessments form the backbone of what would be required for a determination of whether or not a substance is a POP. To them should be added a detailed consideration of the potential for long range transport, for which monitoring data could play an important role. The resulting assessment is not a true risk characterisation in that there is no comparison of exposure and effect levels. Accurately predicting exposure as a result of long range transport is extremely difficult, unless detailed monitoring data in air, water and biota is available. Likewise, predicting dose (or concentration)-response functions is highly problematic for the types of effects associated with POPs, e.g. immune system effects, endocrine disruption, carcinogenicity, reproductive effects. Instead, expert judgement must be used to determine qualitatively the strength of the case for or against the POP classification of the proposed substance.

It has been proposed that UNECE establishes an expert panel, either on an ad-hoc or standing basis, to determine the technical merits of proposals for additional POPs. In either case, the onus would be on the country proposing the addition to provide the detailed assessment, with other countries providing supplementary information. Three outcomes of a proposal would be possible:

the substance is judged to be a POP on current evidence;
the substance is judged not to be a POP on current evidence;
more information is needed to allow a decision to be made.

If the expert panel were to be a standing body, it could devise its own detailed guidelines for assessment, incorporating new assessment techniques as they become available.

If the panel recommends that the substance should be judged to be a POP, the negotiating body, assuming it accepts the recommendation, would then consider the various control options and their socio-economic implications. This final step would hopefully lead to a negotiated amendment to the Protocol.

UNEP/IFCS

The process described above has many parallels with the requirements of the UNEP/IFCS initiative on POPs. Existing UN bodies (possibly IPCS, using its Environmental Health Criteria Document Task Forces as a model) could fulfil the role of the expert panel, and it might be appropriate for the countries most interested in the proposed addition to be responsible for providing all the necessary information for consideration.

Where the UNEP/IFCS process may differ from the UNECE POPs proposal is in the breadth of the risks which the controls are designed to address. UNECE is quite clearly concerned only with long range transboundary air pollution; other risks being considered only when comparing the risk profiles of POPs and their potential alternatives. In UNEP/IFCS other possible target risks have been mentioned, such as other dispersion mechanisms, e.g. the hydrosphere, or problems specific to tropical climates. The relative importance of these risks in relation to those posed by atmospheric transport is beyond the scope of this document, and should be considered by a group of experts as soon as possible in order to focus resources on the most important global environmental issues associated with POPs.