ReviewQuantifying human exposure to air pollution—Moving from static monitoring to spatio-temporally resolved personal exposure assessment
Highlights
► We review and discuss recent developments and advances of research into personal exposure to air pollution. ► We emphasise the importance of personal exposure studies to accurately assess human health risks. ► We discuss potential and shortcomings of methods and tools with a focus on how their development influences study design. ► We propose a novel conceptual model for integrated health impact assessment of human exposure to air pollutants. ► We present a conceptual model taking into account latest technological capabilities and socio-economic context.
Introduction
Human exposure to environmental pathogens and specifically air pollutants is a highly topical issue. Clean air to breathe is a basic requirement of life and the quality of air both outdoors and indoors is a crucial determinant of health (WHO, 2010). Air quality is affected by pollutants such as nitrogen oxides (NOx), particulate matter (PM), carbon monoxide (CO) and ground level ozone (O3).
Substantial growth in individual transport activities and energy consumption reflect growing affluence and contribute considerably to high and, in some cases, increasing ambient levels of air pollutant concentrations. Urban areas with high population densities are especially affected.
Air pollutants are ubiquitous and a certain level of exposure is inevitable, whether a person is indoors or outdoors. For risk and impact assessments of air pollution effects and the design of control policies, such as the UK National Air Quality Strategy (NAQS) or national Air Quality Standard regulations (Scottish Statutory Instrument, 2010) as well as indoor air quality information (Parliamentary Office of Science and Technology, 2010), it is necessary to accurately quantify everyday human exposure to air pollution. Traditionally, personal, environmental exposure has not been directly assessed for individuals, but rather by estimating population-wide exposure via networks of fixed monitoring sites deriving annual ambient average concentrations and spatial interpolation of the results. However technological advances have produced sophisticated monitoring devices carried or worn by a person during their regular daily routine allowing for personal exposure to be monitored explicitly. Time-geography accounting for the movement of people and their individual activity-space is a crucial determinant of personal exposure in this context. The following quote from the founding father of time-geography, Torsten Hägerstrand, reflects this well:
“Existence in society implies people are constantly in motion. Virtually every individual possesses his own unique field of movement, with his residence in the centre and with places of work, shops, places of recreation, residences of intimate friends, and other similar locales serving as nodal points.” (Hägerstrand, 1967, p. 8)
In this paper the focus is on methods and concepts for monitoring the movement of individuals and their everyday exposure to environmental air pollution in space and time. Following the introduction of methods and concepts for exposure assessment in general, recent papers investigating personal exposure are assessed. Methods, concepts and technologies as well as study design described in these papers are discussed in the subsequent sections. We identify shortcomings and development potentials in this research area. Finally, we derive recommendations for future research needs and introduce a novel conceptual model for the assessment of human exposure to air pollution.
Section snippets
Background and scope of the review
Human exposure to a pollutant has been defined as occurring when “a person comes into contact with the pollutant” (Ott, 1982, p. 186). Exposure assessment is “… the process of estimating or measuring magnitude, frequency and duration of exposure to an agent…” (Zartarian et al., 2007, p. 58). Ideally, it is a complementary concept describing sources, pathways, routes as well as the uncertainties in the assessment. Personal exposure assessment is evolving quickly and latest advances in technology
Methods and concepts for personal exposure assessment
Personal exposure assessment requires the recording of a person's time-activity patterns, as well as the pollutant concentrations in the environment through which the person is exposed (Sabel et al., 2009).
A person's movement, having a spatial and temporal component, can be described as a path (Thrift, 1977). Traditionally, the tool to record such a path as well as additional information, for instance on the transport mode used, is a so-called time-activity diary (TAD). Study participants would
Personal monitoring—Pieces of the puzzle?
Personal monitors measure pollutant concentrations as close as possible to a person's breathing zone and provide the most accurate data about actual personal exposure. Regularly conducted comparisons of concentrations measured by personal monitors, fixed-site monitors, stationary ME monitors or even in the direct vicinity of the subject indicate substantial differences in concentration and thus establish a preference for the use of personal monitoring techniques to collect reliable individual
Conclusions
The literature discussed indicates a trend towards real-time tracking of individual time-activity patterns for personal exposure assessment. GPS receivers are becoming widely used to analyse how people move through different MEs and hence experience varying exposure to air pollutants in the respective MEs. In combination with GPS receivers, portable active pollutant monitors can directly relate pollutant concentrations to time and location.
At the same time, small electronic devices such as
Acknowledgements
This work is supported by the Environmental Determinants of Public Health in Scotland (EDPHiS) project, funded by the Scottish Government's Rural and Environment Science and Analytical Services Division (RESAS), and the LIAISE Network of Excellence, funded under the 7th Framework Programme of the European Commission.
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