SUMMARY OF PEER TECHNICAL REVIEW COMMENTS ON
PENTABROMODIPHENYL ETHER AND PERFLUOROOCTANE
SULFONATE DOSSIERS SUBMITTED UNDER THE UNECELRTAP POPS
PROTOCOL PENTACHLOROBENZENE
Introduction: In 2002, The Netherlands proposed commercial Pentachlorobenzene
for listing as persistent organic pollutant (POP) under the UNECE-LRTAP POPs
Protocol. Subsequently updates were issued in December 2005 and January 2006.
The LRTAP nomination process includes the submission of a risk profile by the
proponent Party, which, if considered acceptable by the LRTAP Executive Body, then
undergoes one or more technical reviews. The technical review process has been
separated into Track A (POPs characteristics) and Track B (management options).
This report is an abbreviated summary of four independent technical reviewers of the
risk profile undertaken under Track A of this process. The original technical reviews
are appended and should be referred to should clarification be needed.
Methods: The technical reviews were conducted in a similar manner to those
routinely undertaken for peer reviewed journal articles or government document
preparation. Reviewers were instructed to be transparent, and to include critical
evaluation of such aspects as, inter alia, availability, reliability, completeness and
relevance of the information and references. Only information contained in the
dossiers was to be addressed, and reviewers were to refrain from any elaboration of
their content or comments that could be considered to reflect policy. Thus, the
statements and conclusions made in the technical reviews address the sufficiency and
veracity of the risk profile in making the case that a substance is a POP under the
LRTAP POPs Protocol. Reviewers were at liberty to suggest additional citations and
information, as routinely performed in peer reviews, based on the reviewer’s
knowledge of the subject and contemporary literature, but where asked to base their
conclusions on the information provided in the dossier. Following an introductory
teleconference to discuss the peer review charge, the reviewers acted independently
and were instructed not to seek to obtain consensus on issues, although conversations
between reviewers were permitted. Individual, independent, peer review reports were
submitted by each reviewer. These reports are summarized here with the
understanding that the purpose of this summary is to compile the independent
findings, not to seek consensus on decisions or to provide any further interpretation.
For brevity, the terms “concluded” or “agreed” are used in this following summary to
refer to independent evaluations of whether the risk profile provides sufficient
information to draw its stated conclusions, rather than a concurrence among reviewers
or a de novo assessment of POPs characteristics.
POP characteristics in terms of the guidance and indicative numerical values
provided in the Executive Body Decision 98/2 for:
Persistence: All four technical reviewers concluded that the risk profile presented in
the dossier provides sufficient information to show that pentachlorobenzene is
persistent in the environment with half-lives exceeding the LRTAP indicative
guidance values.
Reviewers generally accepted the estimated values for persistence in water
although one reviewer felt they could have been supported more thoroughly.
One reviewer noted the aquatic photolysis data but agreed that this was
unlikely to be rapid under environmental conditions given the likely
adsorption to suspended matter and sediment. All reviewers noted the data
provided on persistence in soil and sediment agreed that these data supported a
half-life estimate >6 months. One reviewer noted that soil half-lives may be
<6 months in certain soils. One reviewer noted that the data provided was
quite limited and another that it could have been presented more clearly,
possibly in the form of a table.
Bioaccumulation: All four technical reviewers concluded that the risk profile
presented in the dossier provides sufficient information to show that
pentachlorobenzene is bioaccumulative with Bioconcentration Factors (BCFs)
exceeding the LRTAP indicative guidance values of 5000.
Reviewers all felt that the available steady state BCF data on fish clearly
indicated high level of bioconcentration. One reviewer felt that this conclusion
was also supported by the available field study. Two reviewers noted that at
least some of the lower BCFs could be due to shorter non-steady-state testing.
Two reviewers felt that more details regarding the testing, such as lipid
content of the test species, would have enable a better comparison of data. One
reviewer felt that the data could have been presented with greater clarity by
brigading the BCFs together under taxa and including references. Two
reviewers also noted that the log Kow is >5. One reviewer provided additional
referenced data supporting the above general conclusion.
Toxicity: All four technical reviewers concluded that the risk profile presented in the
dossier provides sufficient information to show that pentachlorobenzene is highly
(eco)toxic sufficient to meet the LRTAP indicative guidance criteria.
All reviewers noted the NOEC value of 0.01 mg/l for crustaceans as indicative
of moderate or high toxicity to aquatic organisms. One reviewer felt, however,
that the endpoints in the aquatic toxicity studies were not well described and
more detail should have been included. Two reviewers noted the NOEC value
of 12.5 mg/kg bw from a subchronic study also indicated moderate
mammalian toxicity. One of these reviewers, however, had concerns regarding
the manner of recording of the data and provided some clarifications, but did
not feel these changed the conclusions. The same reviewer had concerns about
of documentation regarding the source of the data presented. This reviewer
also felt that the statement ‘Insufficient evidence was available to conclude
that the substance was teratogenic’ could be misleading and quoted evidence
of possible developmental toxicity from two rat studies presented in the
dossier. One reviewer quoted evidence of the formation of pentachlorophenol
as a metabolite of pentachlorobenzene, and suggested that this might be noted
when considering the potential for carcinogenicity.
Potential for Long-range Transboundary Atmospheric Transport: All four
technical reviewers concluded that the risk profile presented in the dossier provides
sufficient information to show that pentachlorobenzene has the potential to undergo
long-range atmospheric transport according to the LRTAP indicative guidance
criteria.
All reviewers confirmed that pentachlorobenzene can be considered to have
around 2 Pa at 25oC and therefore below the 1000 Pa of the indicative
guidance. Three reviewers commented that the source of these data where not
presented.. All reviewers agreed that the atmospheric half-life was greatly in
excess of two days, although there was some concern that wide ranges were
quoted, eg 45-467 days, and no explanation was provided. Three reviewers
also pointed out that both the modeling and monitoring data from remote
regions supported the conclusion that long-range atmospheric transport was
occurring.
Monitoring or equivalent scientific information suggesting long-range
transboundary atmospheric transport: All four reviewers concluded that the
monitoring evidence provided in the risk profile was sufficient to conclude that longrange atmospheric transport was occurring.
All reviewers noted the presence of pentachlorobenzene in arctic air,
freshwater and biota suggest that long-range transboundary atmospheric
transport is occurring. Two reviewers stressed the relevance of the detection of
pentachlorobenzene in air samples from all 40 locations sampled in North
America, including 5 arctic stations. Two reviewers also noted the additional
data provided by industry showing a declining level over time but noted that
pentachlorobenzene was still being detected in remote regions
Sufficiency of the information to suggest that the substance is likely to have
significant adverse human and/or environmental effects resulting from its longrange transboundary atmospheric transport: All four reviewers conclude that the
data provided indicate that the possibility of adverse effects as a result of long-range
transboundary atmospheric transport cannot be excluded. One reviewer felt that,
while such adverse effects could not be excluded, this was insufficient to conclude
that adverse effects were probable.
Three reviewers recognize that, while concentrations of pentachlorobenzene
are low, they represent a significant contribution to the exposure arising from
similar persistent, bioaccumulative and toxic substances in both man and
biota, the consequences of which are unknown, but potentially severe.
Individual reviewers’ specific comments are included below.
Reviewer A: Human and wildlife are exposed to a cocktail of different
contaminants in the environment including remote regions. Therefore it will
be difficult to relate or predict effects to one single compound, especially if
they have high hazard potentials. In this respect the PEC/PNEC approach is
not a suitable tool to protect ecosystems in sensitive areas. PeCB exhibit
persistent, bio -accumulative and toxic properties. Due to the widespread
distribution of PeCB in the environment including remote regions, the
occurrence in arctic top predators and the hazard potential, adverse effects on
human health and the environment cannot be excluded.
Reviewer B: The dossier concludes there is sufficient information that POP
characteristics of pentachlorobenzene meet the UN-ECE criteria.
Pentachlorobenzene has the potential for long-range atmospheric transport,
persistence in water, sediment and soil, bioaccumulation and ecotoxicity. I
agree with the dossier’s conclusions there is sufficient information that POP
characteristics of pentachlorobenzene meet the UN-ECE criteria for the
potential for long-range atmospheric transport, persistence in water, sediment
and soil, bioaccumulation and ecotoxicity. But the dossier does not state
directly, nor does it provide sufficient quantitative data on amounts
transported long range, most sensitive receptors, or the toxic levels in these
sensitive receptors to warrant an extrapolation to the conclusion “likely to
have significant adverse human and/or environmental effects resulting
from its long-range transboundary atmospheric transport.”
Reviewer C: Scarce toxicological data and incomplete toxicological profile,
while contributing to make problematic the characterization of possible
adverse human and/or environmental effects resulting from long-range
transboundary atmospheric transport, on the other hand induce to consider the
eventuality that adverse effects resulting from toxicological properties
different from those which have been explored might occur. On this basis,
and considering that the substance is persistent, bioaccumulative, and has
been found in remote regions (in both environmental matrices and biota), the
possibility of adverse effects on the delicate balance of complex ecosystems is
not to be excluded.
Reviewer D: Detection of pentachlorobenzene in remote regions and biota
does not, of itself, indicate an adverse effect. The levels detected are very low,
well below any known toxic effect level. There is evidence in the additional
submissions of a time trend although more recent monitoring would indicate
that emissions and consequent exposures are continuing. There is no evidence
of non-threshold effects such as might lead to adverse effects even at the very
low concentrations measured.
Nevertheless, pentachlorobenzene is one of a series of chlorinated aromatics
that constitute an significant load to the environment. It is itself likely to be a
degradation product of hexachlorobenzene and lindane. Its own degradation
has been shown to result in lower chlorinated aromatics such as terta and
trichlorobenzenes that are themselves subject to widespread distribution in the
environment. Assuming that the data provided in the dossier reflects the true
properties of PeCB, then it is clearly a POP like substance for which emissions
are continuing. The possibility of significant harm, particularly through a
contribution to an overall load of persistent and bioaccumulative substances,
cannot be excluded
Conclusions on the technical content of the dossier: All reviewers felt that
the dossier, including the updates submitted in December 2005 and January
2006, provided sufficient information to conclude that pentachlorobenzene
meets the indicative criteria of Executive Decision 98/2 for consideration as an
LRTAP POP, although one reviewer felt that this provided insufficient
information to justify the conclusion that it is “likely to have significant
adverse human and/or environmental effects resulting from its long-range
transboundary atmospheric transport.” Two reviewers felt that some of the
data could have been better supported by information on sources and
additional verifiable detail.