---

Recommendations for further research

130. In making recommendations for further research, the Panel has included only that research which may have a bearing on future setting of standards for particulate air pollution. Thus, our principal objective is to advise the Government on directions that might be taken to assist in setting a Standard more directly relevant to adverse health effects than is the present PM₁₀ Standard. We note that substantial progress in understanding the effects of air pollution in the UK has been made with relatively modest funding and recognise that pollution still has effects, both short- and long-term, on the health of the population that should not be ignored. We believe that continuation of a specifically targeted research programme is an important condition for solution of those outstanding problems that prevent definition of a better metric for control of particulate pollution in the UK. Three areas in particular have been considered:

• better toxicological characterisation of the different components of the particulate aerosol;
• better methods for measurement of the various components of the aerosol; and
• further epidemiological studies investigating relations between different components and health effects.

131. The toxic component may be defined in any of three ways; by in vitro studies, by animal experiments, and by human studies, either epidemiological or toxicological. Epidemiological studies have suggested that this component may lie more in the fine fraction of PM₁₀ than in the coarse fraction, although some effect of the coarse fraction cannot be ruled out. Experimental studies give further support to the concept that it is likely to be related mainly to the fine fraction. Further studies of the interactions of particle surfaces and surface chemicals with relevant lung cells and fluids are desirable, since in the future a chemical method of particle monitoring may prove a realistic option.

132. Studies intended to improve measurement of the toxic component must necessarily wait until that component is better defined. At present the experimental clues do, however, give an indication of the directions research might take. There is scope for development of improved methods for measurement of particle number, surface area and adsorbed transition metals, which could be applied in epidemiological studies and would allow their comparison with the traditional gravimetric measures as predictors of health effects.

133. The potential of epidemiological studies to distinguish the effects of different exposure metrics will depend importantly on the extent to which the metrics are intercorrelated in the populations investigated. Further epidemiological studies would be helpful where such intercorrelation was sufficiently low that differences between the metrics could be discriminated. These studies might take the form of time-series analyses of mortality or hospital admissions in large populations; panel studies of individuals suspected to be more vulnerable to the effects of particulate pollutants; and cross-sectional and longitudinal comparisons of morbidity and mortality in geographical locations with different patterns of pollution.

134. The most important contribution of epidemiology towards defining a suitable metric for particulate pollution control will be to distinguish the effects of different measurement metrics. We welcome the institution by the Government and Devolved Administrations of a number of sites at which multiple measurements are to be made simultaneously, and point out the need to couple these measurements with carefully designed epidemiological and toxicological studies. Such sites, which are predominantly situated in large cities, will afford the opportunity of carrying out panel studies of suspected vulnerable individuals, using intermediate markers of health effects (such as changes in cardiac function or blood variables). In order to increase the power of such studies to detect associations between the measurements of particles and health, further studies aimed at modelling the exposures of individuals within populations are also desirable. Investigation of the possible longer-term consequences of exposure to particulate air pollution is likely to be difficult in the UK context, but is nevertheless of great importance. Consideration should be given to setting up longitudinal studies, but efforts should be made to exploit any current population databases used, for example, in the study of risk factors for cardiovascular or neoplastic disease, linking them to accumulated data on Black Smoke and sulphur dioxide.

[ Previous ] [ Contents ] [ Next ]

---

Published 17 May 2001

---

Expert Panel on Air Quality Standards

---

Air and Envirnonmental Quality

---

Environmental Protection Index

---

Defra Home Page