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Current air quality standards for particulate matter (PM) use the PM mass concentration [PM with aerodynamic diameters ≤ 10 μm (PM(10)) or ≤ 2.5 μm (PM(2.5))] as a metric. It has been suggested that particles from combustion sources are more relevant to human health than are particles from other sources, but the impact of policies directed at reducing PM from combustion processes is usually relatively small when effects are estimated for a reduction in the total mass concentration. We evaluated the value of black carbon particles (BCP) as an additional indicator in air quality management. We performed a systematic review and meta-analysis of health effects of BCP compared with PM mass based on data from time-series studies and cohort studies that measured both exposures. We compared the potential health benefits of a hypothetical traffic abatement measure, using near-roadway concentration increments of BCP and PM(2.5) based on data from prior studies. Estimated health effects of a 1-μg/m3 increase in exposure were greater for BCP than for PM(10) or PM(2.5), but estimated effects of an interquartile range increase were similar. Two-pollutant models in time-series studies suggested that the effect of BCP was more robust than the effect of PM mass. The estimated increase in life expectancy associated with a hypothetical traffic abatement measure was four to nine times higher when expressed in BCP compared with an equivalent change in PM(2.5) mass. BCP is a valuable additional air quality indicator to evaluate the health risks of air quality dominated by primary combustion particles.

Given the hypothesis that air pollution is associated with elevated blood pressure and heart rate, the effect of daily concentrations of air pollution on blood pressure and heart rate was assessed in 131 adults with coronary heart disease in Helsinki, Finland; Erfurt, Germany; and Amsterdam, the Netherlands. Blood pressure was measured by a digital monitor, and heart rate was calculated as beats per minute from an electrocardiogram recording with the patient in supine position. Particle concentrations were measured at central measuring sites. Linear regression was used to model the association between 24-hr mean concentrations of particles and blood pressure and heart rate. Estimates were adjusted for trend, day of week, temperature, barometric pressure, relative humidity, and medication use. Pooled effect estimates showed a small significant decrease in diastolic and systolic blood pressure in association with particulate air pollution; a slight decrease in heart rate was found. Of the three centers, Erfurt revealed the most consistent particle effects. The results do not support findings from previous studies that had shown an increase in blood pressure and heart rate in healthy individuals in association with particles. However, particle effects might differ in cardiac patients because of medication intake and disease status, both affecting the autonomic control of the heart.

The blackness of aerosol filter samples, meant as a proxy for particulate mass concentration, is the earliest parameter for which monitoring data exist. The smoke shade method (developed in the late 1910s) was the standardised approach to collect samples. The blackness was visually appraised by a comparison with a set of reference sheets covered with an increasing number of layers (shades) of a suspension of carbon black (ink). Samples were assigned a shade number (SN) according to the number of shades of ink on the reference sheet with a corresponding blackness. Automated hourly sampling started in 1921. After World War II, the blackness was measured with a reflectometer and light absorption was translated to the parameter British Smoke (BrS). One unit of SN was equivalent to a specific loading of BrS of 8 μg cm−2. BrS in turn is a proxy for elemental carbon (EC) as we showed in an earlier publication, where we found that a value of BrS of 8 μg cm−2 corresponded to an EC load of 1.4 μg cm−2. SNs can thereby be translated to historic EC loadings/concentrations. In an evaluation of SN-data, we noticed that average pre-war values were mostly at the lower detection limit (one SN) and overestimated because reference sheets faded over time. Data for smog periods with their elevated SNs, however, are quite reliable and can be used for exposure estimates. After World War II, daily sampling resulted in higher filter loadings and reliable average values. Wintertime concentrations corresponding to up to 100 μg m−3 EC were reached. On the other hand, the increased loadings due to the long sampling times resulted in a decrease of the upper limit of detection to an extent that it was exceeded at most of the measuring stations during the “Great Smog” of London in 1952. In this study, we analysed SN data from this episode in depth. At one measuring site, precautions were taken to minimise the loading by using a large filter, but even then the maximum SN was at the upper limit of detection. From a one-to-one relation of BrS and gravimetric mass, established during later smog periods, we deduced that the maximum 2-day mass concentration of EC must have been around 1000 μg m−3. This value is twenty times the new EU-limit for workplace EC exposure (EU 2019) and the 24-h ambient PM10 mass concentration.

The below-cloud irradiance in The Netherlands increased by over 10 Wm−2 in the past half century. It was hypothesized that this could be due to a decrease in the aerosol serving as cloud condensation nuclei, on which the cloud droplets form, in the following way. With unchanged macrophysics, clouds with a lower number of droplets are less reflective, in other words, they transmit more solar radiation. This hypothesis cannot be substantiated with data because of a generic absence of long-term information on cloud droplet number concentrations (CDNCs) worldwide. To assess the historic trend in CDNC, we used the Boucher and Lohmann (B&L) empirical relationship between CDNC and the mass concentration of the water-attracting hygroscopic aerosol components. The B&L parameterization was tested and validated with observations from the CHIEF cloud chamber, in which the formation of marine stratocumulus, the most frequent cloud type in The Netherlands, is simulated. This study will focus on summer periods because the irradiance governs the yearly average at this latitude. The summer trend of sulfate, the most dominant hygroscopic component of observed aerosol mass concentration, was analyzed with EBAS data from 1972 onwards. The average summer CDNCs were then calculated via the B&L parameterization, showing an upper limit of 380 cm−3 in the 1970s and decreasing to around 200 cm−3 in the 2010s. The associated increase in transmission for thin marine stratocumulus without overlying clouds would be, at most, 3.5 W m−2. Unobstructed stratocumuli occur only part of the time, and the change in irradiance based on the reduction in cloud droplet number is certainly small in comparison to the empirically derived trend of 10 W m−2.

ObjectivesStudies of individual inflammatory responses to exposure to air pollution are few but are important in defining the most sensitive markers in better understanding pathophysiological pathways in the lung. The goal of this study was to assess whether exposure to airborne particles is associated with oxidative stress in an epidemiological setting.MethodsThe authors assessed exposure to particulate matter air pollution in four European cities in relation to levels of nitrite plus nitrate (NOx) in exhaled breath condensate (EBC) measurements in 133 subjects with asthma or chronic obstructive pulmonary disease using an EBC capture method developed for field use. In each subject, three measurements were collected. Exposure measurements included particles smaller than 10 μm (PM10), smaller than 2.5 μm (PM2.5) and particle number counts at a central site, outdoors near the subject's home and indoors.ResultsThere were positive and significant relationships between EBC NOx and coarse particles at the central sampling sites (increase of 20.4% (95% CI 6.1% to 36.6%) per 10 μg/m3 increase of coarse particles of the previous day) but not between EBC NOx and other particle measures. Associations tended to be stronger in subjects not taking steroid medication.ConclusionsAn association was found between exposure to ambient coarse particles at central sites and EBC NOx, a marker of oxidative stress. The lack of association between PM measures more indicative of personal exposures (particularly indoor exposure) means interpretation should be cautious. However, EBC NOx may prove to be a marker of PM-induced oxidative stress in epidemiological studies.

The light absorbance of PM-samples on PTFE filters is often used as a measure for exposure to diesel soot in large-scale health studies. Absorbance is a synonym for the optical parameter “absorption coefficient” (AbsC). The formal exposure measure for diesel soot is the mass concentration of the light absorbing species of PM, viz. elemental carbon (EC). In the central health effects study by Janssen et al. [2011] a relation between AbsC and EC is presented, however with an overall uncertainty of 2.5. In the present study, we started with an analysis of the measuring approach of light absorption according to ISO-9835 [ISO, 1993]. Following this procedure, absorption is probed in reflection and expressed in the ratio of the intensity of light reflected from/by a clean and a loaded filter. The AbsC is the logarithm of this ratio (which is known as optical depth) scaled to the volume of air sampled and loaded filter area. We first critically reanalysed the studies used by Janssen et al. [2011] in which the equivalency factor between absorbance and EC concentration was given. We found a good linear relationship when we selected only those data points for which the optical density (OD) was within the proper limits of 0.05 and 2.0. We then analysed which methods had been used to obtain EC data in those studies (and also more recent ones) and selected only those studies where EC had been determined with an official reference approach, i.e. the USreference method NIOSH-5400. The overall relation of EC mass concentration in µg m −3 and AbsC in units of 10 –5  m −1 was 0.8 (R 2  = 0.92), or 1.0 according to the EU-reference method EUSAAR2-TOT with a factor of 1.25 between US and EU reference EC values. This highly improved estimate of equivalence factors between AbsC and EC might be used to translate the results of existing health effects studies (based on AbsC) to studies using current EC monitoring data (as prescribed in EU-guidelines for air quality) to investigate the possible health effects at a given EC level.

The associations between residential outdoor and ambient particle mass, fine particle absorbance, particle number (PN) concentrations, and residential and traffic determinants were investigated in four European urban areas (Helsinki, Athens, Amsterdam, and Birmingham). A total of 152 nonsmoking participants with respiratory diseases, not exposed to occupational pollution, were included in the study, which comprised a 7-day intensive exposure monitoring period of both indoor and home outdoor particle mass and number concentrations. The same pollutants were also continuously measured at ambient fixed sites centrally located to the studied areas (fixed ambient sites). Relationships between concentrations measured directly outside the homes (residential outdoor) and at the fixed ambient sites were pollutant-specific, with substantial variations among the urban areas. Differences were more pronounced for coarse particles due to resuspension of road dust and PN, which is strongly related to traffic emissions. Less significant outdoor-to-fixed variation for particle mass was observed for Amsterdam and Birmingham, predominantly due to regional secondary aerosol. On the contrary, a strong spatial variation was observed for Athens and to a lesser extent for Helsinki. This was attributed to the overwhelming and time-varied inputs from traffic and other local sources. The location of the residence and traffic volume and distance to street and traffic light were important determinants of residential outdoor particle concentrations. On average, particle mass levels in suburban areas were less than 30% of those measured for residences located in the city center. Residences located less than 10 m from a street experienced 133% higher PN concentrations than residences located further away. Overall, the findings of this multi-city study, indicated that (1) spatial variation was larger for PN than for fine particulate matter (PM) mass and varied between the cities, (2) vehicular emissions in the residential street and location in the center of the city were significant predictors of spatial variation, and (3) the impact of traffic and location in the city was much larger for PN than for fine particle mass.

The interaction of layers with differing static stability, such as those encountered in natural plant or urban canopies, made Falcona stress the importance of mixing near the emission and deposition sources and sinks, and in particular the dire inadequacy of eddy diffusivity models in situations where the turbulent mixing elements were of the same size or larger than the principal features of the concentration gradients. A debate to explore future lines of research and collaboration closed the Research School. The increase of the urban region dimensions of the cities planned for the twenty-first century represents a challenge for the atmospheric physics/chemistry community because it requires maintaining air quality standards in relation to both human health and the potential impact on climate change.

BACKGROUND: Current air quality standards for paniculate matter (PM) use the PM mass concentration [PM with aerodynamic diameters ≤ 10 μm (PM₁₀) or < 2.5 μm (PM₂.₅)] as a metric. It has been suggested that particles from combustion sources are more relevant to human health thanare particles from other sources, but the impact of policies directed at reducing PM from combustion processes is usually relatively small when effects are estimated for a reduction in the total mass concentration. OBJECTIVES: We evaluated the value of black carbon particles (BCP) as an additional indicator in air quality management. METHODS: We performed a systematic review and meta-analysis of health effects of BCP compared with PM mass based on data from time-series studies and cohort studies that measured both exposures.We compared the potential health benefits of a hypothetical traific abatement measure, using near-roadway concentration increments of BCP and PM₂.₅ based on data from prior studies. RESULTS: Estimated health effects of a 1-μg/m³ increase in exposure were greater for BCP than for PM₁₀ or PM₂.₅, but estimated effects of an interquartile range increase were similar. Two-pollutant models in time-series studies suggested that the effect of BCP was more robust than the effect of PM mass. The estimated increase in life expectancy associated with a hypothetical traffic abatement measure was four to nine times higher when expressed in BCP compared with an equivalent changein PM₂.₅ mass. CONCLUSION: BCP is a valuable additional air quality indicator to evaluate the health risks of air quality dominated by primary combustion particles.