For many air pollution epidemiological studies in Europe, ‘black smoke’ (BS) was the only measurement available to quantify ambient particulate matter (PM), particularly for exposures prior to the mid-1990s when quantification via the PM10 and/or PM2.5 metrics was introduced. The aim of this work was to review historic BS and PM measurements to allow comparison of health concentration-response functions (CRF) derived using BS as the measure of exposure with CRFs derived using PM10 or PM2.5.The literature was searched for quantitative information on measured ratios of BS:PM10, BS:PM2.5, and chemical composition of PM; with specific focus on the United Kingdom (UK) between 1970 and the early 2000s when BS measurements were discontinued.The average BS:PM10 ratio in urban background air was just below unity at the start of the 1970s, decreased rapidly to ≈ 0.7 in the mid-1970s and to ≈ 0.5 at the end of the 1970s, with continued smaller declines in the 1980s, and was within the range 0.2–0.4 by the end of the 1990s. The limited data for the BS:PM2.5 ratio suggest it equalled or exceeded unity at the start of the 1970s, declined to ≈ 0.7 by the end of the 1970s, with slower decline thereafter to a range 0.4–0.65 by the end of the 1990s. For an epidemiological study that presents a CRFBS value, the corresponding CRFPM10 value can be estimated as RBS:PM10 × CRFBS where RBS:PM10 is the BS:PM10 concentration ratio, if the toxicity of PM10 is assumed due only to the component quantified by a BS measurement. In the general case of some (but unknown) contribution of toxicity from non-BS components of PM10 then CRFPM10 > RBS:PM10 × CRFBS, with CRFPM10 exceeding CRFBS if the toxicity of the other components in PM10 is greater than the toxicity of the component to which the BS metric is sensitive. Similar analyses were applied to relationships between CRFPM2.5 and CRFBS.Application of this analysis to example published CRFBS values for short and long-term health effects of PM suggest health effects from other components in the PM mixture in addition to the fine black particles characterised by BS.

•Land-use regression (LUR) models for NO2 were evaluated using a dispersion model.•The number of monitoring sites improved LUR model performance, but not > ∼30 sites.•Networks including sites in populated areas better estimated across residential NO2.•Roadside sites needed to better characterise the high end of residential NO2.•No specific monitoring site design estimated both overall and high NO2 levels well.Land-use regression (LUR) models are increasingly used to estimate exposure to air pollution in urban areas. An appropriate monitoring network is an important component in the development of a robust LUR model. In this study concentrations of NO2 were simulated by a dispersion model at ‘virtual’ monitoring sites in 54 network designs of varying numbers and types of site, using a 25 km2 area in Edinburgh, UK, as an example location. Separate LUR models were developed for each network. The LUR models were then used to estimate NO2 concentration at all residential addresses, which were evaluated against the dispersion-modelled concentration at these addresses. The improvement in predictive capability of the LUR models was insignificant above ∼30 monitoring sites, although more sites tended to yield more precise LUR models. Monitoring networks containing sites located within highly populated areas better estimated NO2 concentrations across all residential locations. LUR models constructed from networks containing more roadside sites better characterised the high end of residential NO2 concentrations but had increased errors when considering the whole range of concentrations. No particular composition of monitoring network resulted in good estimation simultaneously across all residential NO2 concentration and of the highest NO2 levels. This evaluation with dispersion modelling has shown that previous LUR model validation methods may have been optimistic in their assessment of the model's predictive performance at residential locations.

Nitrogen dioxide (NO2) is a ubiquitous air pollutant with high concentrations particularly close to main roads. The focus of this study was on possible differences in NO2 concentrations between adult and child heights as a function of different distances from heavily trafficked roads in urban areas. Passive diffusion tubes were used to measure NO2 concentrations at heights of 0.8 m (approximate inhalation height of children and closer to vehicle exhaust height) and 2.0 m (approximate inhalation height of adults) above the ground at a number of locations and over several weeks in the city of Edinburgh, UK. Evidence for significant differences in NO2 between heights was observed up to at least 1.2 m from kerbside of busy roads, with tubes at 0.8 m measuring concentrations 5–15 % (a few μg m−3) greater than at 2.0 m. The vertical NO2 concentration difference was not observable at distances 2.5 m or greater from the kerbside. Fitting of horizontal transects of NO2 concentrations away from main roads demonstrated the strong influence of wind speed in yielding faster fall-off in NO2 concentration from the roadside, and in near-ground vertical gradient in NO2, and lower background NO2 concentrations. These observations have potential public health implications for differential NO2 exposures between children walking, or in buggies, close to heavily trafficked urban roads compared with adults.

Insights into the nature and sources of the urban and roadside increments in carbonaceous PM10 are gained from bulk chemical analyses on daily filter samples collected at a roadside, urban background and rural site in Edinburgh, UK (not all sampling contemporaneous). The concentrations of PM10 water-soluble organic matter (WSOM) at the three sites were similar, and (where measured concurrently) strongly correlated, indicating a uniform background source, in contrast to the black carbon component (quantified by filter optical reflectance) whose average concentrations at urban background and roadside were, respectively, about 3 and 7 times greater than at the rural site, indicating local urban sources. BC was not a major component of PM10 but was a major component of the urban and roadside PM10 increments (∼50% and ∼60% respectively). The roadside WSOM had greater hydrophobicity than the urban background WSOM. UV–vis spectra indicated increased prevalence of unsaturated bonds and conjugation in urban background WSOM in winter compared with summer. This is consistent with both summertime photochemical production of particle OM and maritime primary aliphatic WSOM. Raman microscopy of a small subset of samples indicated carbon functionality ranged between diesel-like material and more complex humic-like material. Results overall indicate the presence of a background functionalized carbonaceous material, with local BC sources superimposed.

The diversity of ambient particle size and chemical composition considerably complicates pinpointing the specific causal associations between exposure to particles and adverse human health effects, the contribution of different sources to ambient particles at different locations, and the consequent formulation of policy action to most cost-effectively reduce harm caused by airborne particles. Nevertheless, the coupling of increasingly sophisticated measurements and models of particle composition and epidemiology continue to demonstrate associations between particle components and sources (and at lower concentrations) and a wide range of adverse health outcomes. This article reviews the current approaches to source apportionment of ambient particles and the latest evidence for their health effects, and describes the current metrics, policies and legislation for the protection of public health from ambient particles. A particular focus is placed on particles in the ultrafine fraction. The review concludes with an extended evaluation of emerging challenges and future requirements in methods, metrics and policy for understanding and abating adverse health outcomes from ambient particles.

A few studies have suggested that the precision and accuracy of measurement of NO2 by Palmes-type passive diffusion tube (PDT) are affected by the method of preparation of the triethanolamine (TEA) absorbent coating on the grids. Theses studies have been quite limited in extent and have tended to evaluate PDT accuracy as zero bias between PDT NO2 value and the exposure-averaged NO2 determined by co-located chemiluminescence analyser. This ignores the well-documented intrinsic systematic biases on PDT-derived NO2, such as within-tube chemistry and exposure-duration nitrite loss, which may lead to non-zero bias values irrespective of effects of TEA absorbent preparation method on PDT accuracy. This paper reports on a statistical analysis of a large dataset comprising 680 duplicated PDT exposures spanning 146 separate exposure periods, spread over five urban exposure locations and a number of years. In each exposure period, PDTs prepared by between four and six different grid preparation methods were simultaneously compared. The preparation methods used combinations of the following: acetone or water as the TEA solvent; 20% or 50% as %TEA in the solution; and application of TEA solution by dipping grids for several minutes in the solution before drying and tube assembly, or by pipetting 50 µL of solution directly onto grids already placed in the PDT cap. These represent the range of preparation procedures typically used. Accuracy was evaluated as maximised nitrite capture within an exposure. Data were analysed by general linear modelling including examination of interaction between different aspects of grid preparation method. PDT precision and accuracy were both significantly better, on average, when the PDT grids were prepared by dipping in TEA solution, and neither solvent or %TEA used for the dipping solution were important. Where PDT preparation by pipetting TEA solution onto grids is to be used, better performance was obtained using 20% TEA in water. A systematic positive bias in PDT measure of NO2, consistent with within-tube oxidation of NO to NO2 and independent of preparation method, was again evident in this work.

Soil is an important compartment in the environmental cycling of trichloroacetic acid (TCA), but soil TCA concentration is a methodologically defined quantity; analytical methods either quantify TCA in an aqueous extract of the soil, or thermally decarboxylate TCA to chloroform in the whole soil sample. The former may underestimate the total soil TCA, whereas the latter may overestimate TCA if other soil components (e.g. humic material) liberate chloroform under the decarboxylation conditions. The aim of this work was to show that extraction and decarboxylation methods yield different TCA concentrations because the decarboxylation method can also determine “bound” TCA. Experiments with commercial humic acid solutions showed there was no additional chloroform formation under decarboxylation conditions, and that all TCA in a TCA–humic acid mixture could be quantitatively determined (108 ± 13%). Anion exchange resin was used as a provider of solid-phase TCA binding; only 5 ± 1% of a TCA solution mixed with the resin was present in the aqueous extract subsequently separated from the resin, yet the decarboxylation method yielded mass balance (123 ± 22%) with TCA remaining in the resin. In aqueous extraction of a range of soil samples (with or without added TCA spike), the decarboxylation method was able to satisfactorily account for TCA in the extractant + residue post-extraction, compared with whole-soil TCA (+ spike) pre-extraction: e.g. mass balances for unspiked soil from Sikta spruce and larch forest were 99 ± 8% and 93 ± 6%, respectively, and for TCA-spiked forest and agricultural soils were 114 ± 13% and 102 ± 2%. In each case recovery of TCA in the extractant was substantially less than 100% (<20% for unspiked soils, <55% for spiked soils). Extraction efficiencies were generally lower in more organic soils. The results suggest that analytical methods which utilise aqueous extraction may underestimate whole-soil TCA concentrations. Application of both methodologies together may enhance insight into TCA behaviour in soil.

This study was carried out in response to suggestions that the measurement of NO2 by Palmes-type passive diffusion tubes (PDT) is affected by the method of preparation of the triethanolamine (TEA) absorbent coating on the grids. The following combinations of factors were investigated: TEA solvent (acetone or water), volume composition of TEA in solvent (50% or 20%), and grid coating method (dipping in solution prior to assembly or pipetting solution on after assembly). Duplicate PDTs prepared by each of the 8 methods were exposed in parallel, in urban air, for a total of 80 separate 1 week exposures. NO2 concentrations derived from PDTs prepared by pipetting methods were significantly less precise than concentrations from dipping methods, with mean RSDs for duplicate measurements of 13.8% and 8.5%, respectively (n = 316 each category). Pipetting methods using solutions of 50% TEA composition were particularly imprecise (mean RSD 17.2%). Data from PDTs prepared by pipetting methods were systematically more poorly correlated with each other and with data from co-located chemiluminescence analysers, than corresponding data from PDTs prepared by dipping methods, indicating that more consistent accuracy was also obtained by the latter PDTs. The statistical evidence suggested that PDTs prepared by pipetting 50% TEA in water generally gave lower NO2 concentrations. Although this is in agreement with a previous study, it is also possible that such an observation here may be a statistical artefact given the demonstrably poorer precision of this method. The general tendency of PDTs to show positive bias in NO2 measurement in urban air in 1 week exposures was again evident in this study (mean biases at roadside and urban centre locations of +35% (n = 475) and +18% (n = 112), respectively) consistent with augmentation of within-tube NO2 flux by chemical reaction between co-diffusing NO and O3. Overall, it is recommended that the pipetting method of PDT grid preparation is avoided, or at least investigated further, because of the apparent degradation in precision and accuracy of NO2 measurement. Potential reasons for the effect are discussed.

A wetted-wall cylindrical flow reactor was used to measure uptake coefficients, γ, of O3 on aqueous surfaces at 293 K. The loss of O3 from the gas-phase following contact with varying areas of aqueous surface was determined by UV absorption. The use of Na2S2O3 as an aqueous-phase scavenger for O3 ensured that uptake coefficients were in a reaction-controlled rather than mass accommodation-controlled regime. Observed uptake coefficients were corrected for radial gas-diffusion to yield values of γcorr. From extrapolation of a plot of 1/γcorr against the inverse square-root of the Na2S2O3 activity, a value of α=4×10−2 was derived for the true mass accommodation coefficient of O3. Evaluation of uncertainties indicate a conservative lower limit of 10−2 for α. The data do not rule out that the upper limit approaches unity. However, it is shown that the measured value of α is sufficiently high that mass accommodation does not limit heterogeneous processing of O3 in the atmosphere for droplets of diameter >10 μm. A value of 3.7+0.7−0.6×108 L mol−1 s−1 is derived for the aqueous-phase reaction rate coefficient between O3 and Na2S2O3 at 293 K.

Five different instruments for the determination of the mass concentration of PM10 in air were compared side-by-side for up to 33 days in an undisturbed indoor environment: a tripod mounted BGI Inc. PQ100 gravimetric sampler with a US EPA certified Graseby Andersen PM10 inlet; an Airmetrics Minivol static gravimetric sampler; a Casella cyclone gravimetric personal sampler; an Institute of Occupational Medicine gravimetric PM10 personal sampler; and two TSI Inc. Dustrak real-time optical scattering personal samplers. For 24 h sampling of ambient PM10 concentrations around 10 µg m−3, the estimated measurement uncertainty for the two gravimetric personal samplers was larger (∼±20%) compared with estimated measurement uncertainty for the PQ100/Graseby Andersen sampler (<±5%). Measurement uncertainty for the Dustraks was lower (∼±15% on average) but calibration of the optical response against a reference PM10 method is essential since the Dustraks systematically over-read PM10 determined gravimetrically by a factor ∼2.2. However, once calibrated, the Dustrak devices demonstrated excellent functionality in terms of ease of portability and real-time data acquisition. Estimated measurement uncertainty for PM10 concentrations determined with the Minivol were ±5%. The Minivol data correlated well with PQ100/Graseby Andersen data (r = 0.97, n = 18) but were, on average, 23% greater. The reason for the systematic discrepancy could not be traced. Intercomparison experiments such as these are essential for assessing measurement error and revealing systematic bias. Application of two Dustraks demonstrated the spatial and temporal variability of exposure to PM10 in different walking and transport microenvironments in the city of Edinburgh, UK. For example, very large exposures to PM10 were identified for the lower deck of a double-decker tour bus compared with the open upper deck of the same vehicle. The variability observed emphasises the need to determine truly personal exposure profiles of PM10 for quantifying exposure–response relationships for epidemiological studies.

•Hourly surface O3 simulated at high resolution over the UK for different scenarios•Burdens of O3-attributable mortality and respiratory hospitalizations quantified•Largest increases under a ‘current legislation’ emissions scenario (for 2030)•For 35 ppbv O3 threshold assumption, health burdens approx order of magnitude smaller•Spatial variation reflects interplay between background O3 and local NOx emissionsExposure to surface ozone (O3), which is influenced by emissions of precursor chemical species, meteorology and population distribution, is associated with excess mortality and respiratory morbidity. In this study, the EMEP-WRF atmospheric chemistry transport model was used to simulate surface O3 concentrations at 5 km horizontal resolution over the British Isles for a baseline year of 2003, for three anthropogenic emissions scenarios for 2030, and for a + 5 °C increase in air temperature on the 2003 baseline. Deaths brought forward and hospitalisation burdens for 12 UK regions were calculated from population-weighted daily maximum 8-hour O3. The magnitude of changes in annual mean surface O3 over the UK for + 5 °C temperature (+ 1.0 to + 1.5 ppbv, depending on region) was comparable to those due to inter-annual meteorological variability (− 1.5 to + 1.5 ppbv) but considerably less than changes due to precursor emissions changes by 2030 (− 3.0 to + 3.5 ppbv, depending on scenario and region). Including population changes in 2030, both the ‘current legislation’ and ‘maximum feasible reduction’ scenarios yield greater O3-attributable health burdens than the ‘high’ emission scenario: + 28%, + 22%, and + 16%, respectively, above 2003 baseline deaths brought forward (11,500) and respiratory hospital admissions (30,700), using O3 exposure over the full year and no threshold for health effects. The health burdens are greatest under the ‘current legislation’ scenario because O3 concentrations increase as a result of both increases in background O3 concentration and decreases in UK NOx emissions. For the + 5 °C scenario, and no threshold (and not including population increases), total UK health burden increases by 500 premature deaths (4%) relative to the 2003 baseline. If a 35 ppbv threshold for O3 effects is assumed, health burdens are more sensitive to the current legislation and + 5 °C scenarios, although total health burdens are roughly an order of magnitude lower. In all scenarios, the assumption of a threshold increases the proportion of health burden in the south and east of the UK compared with the no threshold assumption. The study highlights that the total, and geographically-apportioned, O3-attributable health burdens in the UK are highly sensitive to the future trends of hemispheric, regional and local emissions of O3 precursors, and to the assumption of a threshold for O3 effect.

Previous work has indicated that the soil is important to understanding biogeochemical fluxes of trichloroacetic acid (TCA) in the rural environment, in forests in particular. Here, the hydrological and TCA fluxes through 22 in situ soil columns in a forest and moorland-covered catchment and an agricultural grassland field in Scotland were monitored every 2 weeks for several months either as controls or in TCA manipulation (artificial dosing) experiments. This was supplemented by laboratory experiments with radioactively-labelled TCA and with irradiated (sterilised) soil columns. Control in situ forest soil columns showed evidence of net export (i.e. in situ production) of TCA, consistent with a net soil TCA production inferred from forest-scale mass balance estimations. At the same time, there was also clear evidence of substantial in situ degradation within the soil (∼70% on average) of applied TCA. The laboratory experiments showed that both the formation and degradation processes operate on time scales of up to a few days and appeared related more with biological rather than abiotic processes. Soil TCA activity was greater in more organic-rich soils, particularly within forests, and there was strong correlation between TCA and soil biomass carbon content. Overall it appears that TCA soil processes exemplify the substantial natural biogeochemical cycling of chlorine within soils, independent of any anthropogenic chlorine flux.

The diversity of ambient particle size and chemical composition considerably complicates pinpointing the specific causal associations between exposure to particles and adverse human health effects, the contribution of different sources to ambient particles at different locations, and the consequent formulation of policy action to most cost-effectively reduce harm caused by airborne particles. Nevertheless, the coupling of increasingly sophisticated measurements and models of particle composition and epidemiology continue to demonstrate associations between particle components and sources (and at lower concentrations) and a wide range of adverse health outcomes. This article reviews the current approaches to source apportionment of ambient particles and the latest evidence for their health effects, and describes the current metrics, policies and legislation for the protection of public health from ambient particles. A particular focus is placed on particles in the ultrafine fraction. The review concludes with an extended evaluation of emerging challenges and future requirements in methods, metrics and policy for understanding and abating adverse health outcomes from ambient particles.

A few studies have suggested that the precision and accuracy of measurement of NO2 by Palmes-type passive diffusion tube (PDT) are affected by the method of preparation of the triethanolamine (TEA) absorbent coating on the grids. Theses studies have been quite limited in extent and have tended to evaluate PDT accuracy as zero bias between PDT NO2 value and the exposure-averaged NO2 determined by co-located chemiluminescence analyser. This ignores the well-documented intrinsic systematic biases on PDT-derived NO2, such as within-tube chemistry and exposure-duration nitrite loss, which may lead to non-zero bias values irrespective of effects of TEA absorbent preparation method on PDT accuracy. This paper reports on a statistical analysis of a large dataset comprising 680 duplicated PDT exposures spanning 146 separate exposure periods, spread over five urban exposure locations and a number of years. In each exposure period, PDTs prepared by between four and six different grid preparation methods were simultaneously compared. The preparation methods used combinations of the following: acetone or water as the TEA solvent; 20% or 50% as %TEA in the solution; and application of TEA solution by dipping grids for several minutes in the solution before drying and tube assembly, or by pipetting 50 µL of solution directly onto grids already placed in the PDT cap. These represent the range of preparation procedures typically used. Accuracy was evaluated as maximised nitrite capture within an exposure. Data were analysed by general linear modelling including examination of interaction between different aspects of grid preparation method. PDT precision and accuracy were both significantly better, on average, when the PDT grids were prepared by dipping in TEA solution, and neither solvent or %TEA used for the dipping solution were important. Where PDT preparation by pipetting TEA solution onto grids is to be used, better performance was obtained using 20% TEA in water. A systematic positive bias in PDT measure of NO2, consistent with within-tube oxidation of NO to NO2 and independent of preparation method, was again evident in this work.