Air quality expert group - Fine particulate matter (PM2.5) in ... - Defra

PM2.5 in the UK
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12. With respect to road traffic emissions, a key future factor is that as reductions in
exhaust emissions of PM occur as a consequence of European vehicle emission
regulation, non-exhaust components of traffic emissions will become much
more important, emphasising the need to introduce measures to control their
sources. Emissions from tyre and brake wear, and road abrasion are not well
understood, yet current inventory projections predict that if they continue to be
uncontrolled they will be responsible for over 70% of total traffic emissions of
PM2.5 by 2020.
13. Emissions from fugitive dust sources, small-scale wood and waste burning,
cooking, agriculture, natural sources and shipping are also poorly understood
and difficult to quantify yet can make a significant contribution to PM2.5
concentrations. This needs to be addressed, especially if the benefits of
mitigation are to be assessed.
14. Models are an important tool for the synthesis of knowledge and prediction
of concentrations. Models fulfil an important role in answering questions such
as how will PM levels change into the future, which are the most important
emission sources to control to reach acceptable air quality and what balance
should be struck between policy actions within the UK and abroad? PM models
are still developing and have a number of inadequacies and uncertainties. It
may be that there are ‘surprises’ before we can be sure that they are completely
reliable policy tools. There is a pressing requirement to develop and evaluate PM
models in the policy context.
15. The science underpinning the knowledge of PM2.5 is rapidly evolving and
remains uncertain in many areas. There is a need for rapid translation into the
policy arena of the newest results and understanding.
6.1 PM2.5 report summary of actions
16. Table 6.2 summarises AQEG’s assessment of the action areas for the current
evidence base, highlighting areas which need most attention to improve
understanding of PM2.5 in the UK.
Table 6.2: Action areas for the science and evidence base on PM2.5.
Evidence area Urgency Impact/
importance
Measurements
Automatic Urban and Rural Network
(AURN) PM2.5 measurements
Chemically-speciated PM2.5
measurements
Concentrations and composition
of PM2.5
Addresses recommendation(s)
or conclusion
1 H See Chapter 2 (§2.6) and
paras 4-5
1 H See Chapter 3 (§3.10.2) and
para 7
Observational analysis 2 M See Chapter 3 (§3.10.2)
Determination of rural background 1 H See Chapter 3 (§3.10.2)
Mitigation analysis 2 M See Chapter 3 (§3.10.2) and para 8