Coarse particles compensate for missing daytime sources of nitrous acid and enhance atmospheric oxidation capacity in a coastal atmosphere

Large missing sources of daytime atmospheric nitrous acid (HONO), a vital source of hydroxyl radicals (OH) through its photolysis, frequently exist in global coastal regions. In this study, ambient HONO and relevant species were measured at a coastal site in the Pearl River Delta (PRD), China, during October 2019. Relatively high concentrations (0.32 ± 0.19 ppbv) and daytime peaks at approximately 13:00 of HONO were observed, and HONO photolysis was found to be the dominant (55.5 %) source of the primary OH production. A budget analysis of HONO based on traditional sources suggested large unknown sources during the daytime (66.4 %), which had a significant correlation with the mass of coarse particles (PM2.5-10) and photolysis frequency (J(NO2)). When incorporating photolysis of the abundant nitrate measured in coarse particles with a reasonable enhancement factor relative to fine particles due to favorable aerosol conditions, the missing daytime sources of HONO could be fully compensated by coarse particles serving as the largest source at this coastal site. Our study revealed great potential of coarse particles as a strong daytime HONO source, which has been ignored before but can efficiently promote NOx recycling and thus significantly enhance atmospheric oxidation capacity.

Distribution and the trend of airborne particles and bio-aerosol concentration in pediatric intensive care units with different ventilation setting at two hospitals in Riyadh, Saudi Arabia

OBJECTIVE

To examine the distribution and the trend of airborne particles and bio-aerosol concentration in pediatric intensive care units (PICUs) in two tertiary care hospitals with different ventilation setting.

METHODS

Hospitals A but not B is provided with a central HEPA filter. PICUs in both hospitals were categorized into protective environment (PE) with room HEPA filter, semi-protective environment (SPE) with portable air-purifier, and non-protective environment (NPE) with neither system. Fine particles (≤ 2.5 µm) and coarse particles (≤ 10.0 µm) were obtained using optical particle counter (Lighthouse Handheld 3016) and total bacterial (TBC) and fungal (TFC) counts were obtained using Andersen air sampler.

RESULTS

Hospital B had significantly higher levels of fine and coarse particles (in all room), TBC (in PE), but not TFC compared with matched rooms in hospital A. In hospital B, the levels of fine particles, coarse particles, and TBC were lowest in SPE (p < 0.001, p = 0.004, and p = 0.006, respectively) while TFC was lowest in NPE (p = 0.014). Airborne particles, TBC, and TFC had variable trends with some of the indoor peaks follow outdoor peaks. Gram-positive bacteria (69 %) were the predominant bacteria in hospital A while bacterial flora (70 %) were the predominant bacteria in hospital B (p < 0.001 for each).

CONCLUSIONS

The levels of airborne contaminants and microbial counts in PICUs are significantly affected by the ventilation system and to less extent by outdoor levels. The results indicated that advanced filtration system and central HEPA filters play a significant role in the reduction of indoor fine particulates and TBC.

Concentration and size distribution of atmospheric particles in southern Italy during COVID-19 lockdown period

Many countries imposed lockdown (LD) to limit the spread of COVID-19, which led to a reduction in the emission of anthropogenic atmospheric pollutants. Several studies have investigated the effects of LD on air quality, mostly in urban settings and criteria pollutants. However, less information is available on background sites, and virtually no information is available on particle number size distribution (PNSD). This study investigated the effect of LD on air quality at an urban background site representing a near coast area in the central Mediterranean. The analysis focused on equivalent black carbon (eBC), particle mass concentrations in different size fractions: PM_2.5 (aerodynamic diameter D_a < 2.5 μm), PM₁₀ (D_a < 10 μm), PM_10-2.5 (2.5 < D_a < 10 μm); and PNSD in a wide range of diameters (0.01-10 μm). Measurements in 2020 during the national LD in Italy and period immediately after LD (POST-LD period) were compared with those in the corresponding periods from 2015 to 2019. The results showed that LD reduced the frequency and intensity of high-pollution events. Reductions were more relevant during POST-LD than during LD period for all variables, except quasi-ultrafine particles and PM_10-2.5. Two events of long-range transport of dust were observed, which need to be identified and removed to determine the effect of LD. The decreases in the quasi-ultrafine particles and eBC concentrations were 20%, and 15-22%, respectively. PM_2.5 concentration was reduced by 13-44% whereas PM_10-2.5 concentration was unaffected. The concentration of accumulation mode particles followed the behaviour of PM_2.5, with reductions of 19-57%. The results obtained could be relevant for future strategies aimed at improving air quality and understanding the processes that influence the number and mass particle size distributions.

Agricultural practices drive biological loads, seasonal patterns and potential pathogens in the aerobiome of a mixed-land-use dryland

Air carries a diverse load of particulate microscopic biological matter in suspension, either aerosolized or aggregated with dust particles, the aerobiome, which is dispersed by winds from sources to sinks. The aerobiome is known to contain microbes, including pathogens, as well as debris or small-sized propagules from plants and animals, but its variability and composition has not been studied comprehensibly. To gain a dynamic insight into the aerobiome existing over a mixed-use dryland setting, we conducted a biologically comprehensive, year-long survey of its composition and dynamics for particles less than 10 μm in diameter based on quantitative analyses of DNA content coupled to genomic sequencing. Airborne biological loads were more dependent on seasonal events than on meteorological conditions and only weakly correlated with dust loads. Core aerobiome species could be understood as a mixture of high elevation (e.g. Microbacteriaceae, Micrococcaceae, Deinococci), and local plant and soil sources (e.g. Sphingomonas, Streptomyces, Acinetobacter). Despite the mixed used of the land surrounding the sampling site, taxa that contributed to high load events were largely traceable to proximal agricultural practices like cotton and livestock farming. This included not only the predominance of specific crop plant signals over those of native vegetation, but also that of their pathogens (bacterial, viral and eukaryotic). Faecal bacterial loads were also seasonally important, possibly sourced in intensive animal husbandry or manure fertilization activity, and this microbial load was enriched in tetracycline resistance genes. The presence of the native opportunistic pathogen, Coccidioides spp., by contrast, was detected only with highly sensitive techniques, and only rarely. We conclude that agricultural activity exerts a much stronger influence that the native vegetation as a mass loss factor to the land system and as an input to dryland aerobiomes, including in the dispersal of plant, animal and human pathogens and their genetic resistance characteristics.

Effects of partially replacing animal fat by ethylcellulose based organogels in ground cooked salami

Partial fat replacement in cooked salamis was formulated using organogels made with canola oil, ethylcellulose (EC; 6, 8, 9, 10, 11, 12 and 14%) and three types of surfactants; i.e., glycerol monostearate (GMS), stearyl alcohol/stearic acid (SOSA) and soybean lecithin (Lec). Texture profile analysis (TPA) and back extrusion tests indicated that increasing EC polymer concentration leads to harder gels regardless of the surfactant used. However, using GMS resulted in the hardest gel, whereas Lec did not strengthen the gel (mechanical stress test), but plasticized it. In general, gel hardness had a distinct effect on the binding of the organogel particle to the meat matrix, with softer gels adhering better under progressive compression. Substituting animal fat with organogel did not affect the main TPA parameters in most salami formulations, and canola oil by itself was also not significantly different from the pork and beef fat control. Using canola oil resulted in very small oil globules compared to the animal fat control, while structuring the oil yielded a microstructure with larger fat particles/globules, similar to the control. Color evaluation revealed a shift to yellow of the treatments with organogels compared to the control, but lightness and redness were not altered. The results demonstrate the potential use of structured vegetable oil to manufacture coarse ground meat products with lower saturated fat and a more favorable nutritional profile while resembling the traditional ground products.

Coarse particles (PM2.5-10) and cause-specific hospitalizations in southwestern China: Association, attributable risk and economic costs

The short-term morbidity effects of the coarse particle (diameter in 2.5-10 μm, PM_2.5-10), as well as the corresponding morbidity burden and economic costs, remain understudied, especially in developing countries. This study aimed to examine the associations of PM_2.5-10 with cause-specific hospitalizations in a multi-city setting in southwestern China and assess the attributable risk and economic costs. City-specific associations were firstly estimated using generalized additive models with quasi-poisson distribution to handle over-dispersion, and then combined to obtain the regional average association. City-specific and pooled concentration-response (C-R) associations of PM_2.5-10 with cause-specific hospitalizations were also modeled. Subgroup analyses were performed by age, sex, season and region. The health and economic burden of hospitalizations for multiple outcomes due to PM_2.5-10 were further evaluated. A total of 4,407,601 non-accidental hospitalizations were collected from 678 hospitals. The estimates of percentage change in hospitalizations per 10 μg/m³ increase in PM_2.5-10 at lag01 was 0.68% (95%CI: 0.33%-1.03%) for non-accidental causes, 0.86% (95% CI: 0.36%-1.37%) for circulatory diseases, 1.52% (95% CI: 1.00%-2.05%) for respiratory diseases, 1.08% (95% CI: 0.47%-1.69%) for endocrine diseases, 0.66% (95% CI: 0.12%-1.21%) for nervous system diseases, and 0.84% (95% CI: 0.42%-1.25%) for genitourinary diseases, respectively. The C-R associations of PM_2.5-10 with cause-specific hospitalizations suggested some evidence of nonlinearity, except for endocrine diseases. Meanwhile, the adverse effects were modified by age and season. Overall, about 0.70% (95% CI: 0.35%-1.06%) of non-accidental hospitalizations and 0.78% (95% CI: 0.38%-1.17%) of total hospitalization expenses could be attributed to PM_2.5-10. The largest morbidity burden and economic costs were observed in respiratory diseases. Our findings indicate that PM_2.5-10 exposure may increase the risk of hospitalizations for multiple outcomes, and account for considerable morbidity and economic burden.

Quantification of soil organic carbon stock in urban soils using visible and near infrared reflectance spectroscopy (VNIRS) in situ or in laboratory conditions

Urban soils, like other soils, can be sink or source for atmospheric carbon dioxide, and due to urban expansion, are receiving increasing attention. Studying their highly variable attributes requires high-density sampling, which can hardly be achieved using conventional approaches. The objective of this work was to determine the ability of visible and near infrared reflectance spectroscopy (VNIRS) to quantify soil organic carbon (SOC) concentration (gC kg^-1) and stock (gC dm^-3, or MgC ha^-1 for a given depth layer) in parks and sealed soils of two French cities, Marseille and Nantes, using spectra collected on pit walls or in laboratory conditions (air dried, 2 mm sieved samples). Better VNIRS predictions were achieved using laboratory than in situ spectra (R² ≈ 0.8-0.9 vs. 0.7-0.8 in validation), and for sample SOC concentration than stock (R²_val up to 0.83 in situ and 0.95 in the laboratory vs. 0.78 and 0.89, respectively). Stock was conventionally calculated according to four methods that variably account for coarse particles (>2 mm); and it was better predicted when coarse particles were not taken into account. This was logical using laboratory spectra, collected on 2 mm sieved samples; but concerning in situ spectra, this suggested the operator tended to put the spectrometer beside the coarsest particles during spectrum acquisition. This point is worth considering for urban soils, often rich in coarse particles. Stocks were then aggregated at the profile level: SOC stock prediction was more accurate at profile than sample level when using laboratory spectra (R²_val = 0.94 vs. 0.89, respectively), probably due to uncertainty compensation; but this was not the case when using in situ spectra, possibly because samples collected for SOC analysis and corresponding VNIRS scans were not at the exact same location. This work demonstrates VNIRS usefulness for quantifying SOC stock time- and cost-effectively, in urban soils especially.

Physicochemical and morphological characterization of atmospheric coarse particles by SEM/EDS in new urban central districts of a megacity

Physicochemical and morphological characteristics of atmospheric particles in new urban centers of fast-developing megacities are not well understood. In this study, atmospheric coarse particles (PM_2.5-10) were simultaneously collected in multiple stations (10) in new urban centers, namely Beylikduzu, Buyukcekmece, and Esenyurt, of Istanbul using a modified passive particulate sampling method. Scanning electron microscope and energy dispersive X-photon spectroscopy (SEM-EDS) was used to investigate the size distribution characteristics, chemical composition and their weight percent abundances, and morphological properties of the collected particles. The particle clusters were mainly dominated by Ca-rich Al silicates, Ca dominant, Ca- and S-rich, and NaCl particles, respectively. Their potential sources were assigned to the natural sources (e.g., wind erosion, soil resuspension, and sea sprays) and anthropogenic activities (construction, transportation, mining and crushing, and cement production). In addition to the major contributions (up to 47% of particle number abundance), the minor contribution clusters (less than 1%) with transitional metals rich particles (Fe, Zn, and Cu rich) mainly from anthropogenic sources (combustion, traffic, and vehicular emissions) were identified. The typical size range (> 0.65 to < 11.00 μm) distribution of the major particle clusters fits a left-skewed modal distribution with a peak at 1.10-2.30-μm size range. However, the number of particles decreases significantly with increasing distance to the source, and this justification is stronger for larger size fractions (> 2.3 μm). Particle numbers and varieties indicated significant spatial variations depending upon the identified sources, meteorological factors, and temporal conditions. In general, the results of this study suggest that the passive sampling of PM_2.5-10 coupled with SEM/EDS based single-particle analysis is an effective tool to understand the physicochemical characterization and spatial and temporal variations of atmospheric particles in urban environments.

Acute effect of fine and coarse particular matter on cardiovascular visits in Ningbo, China

Although a growing number of epidemiological studies have been conducted on size-specific health effects of particulate matter in China, results remain inconsistent. In this study, we investigated acute effect of fine and coarse particular matter on cardiovascular hospital visits in Ningbo, China. We used generalized additive models to examine short-term effects of PM_2.5 and PM_10-2.5 on cardiovascular hospital visits by adjustment for temporal, seasonal, and meteorological effects. Subgroup analyses were conducted by age, sex, and season. We also examined the stability of their effects in multi-pollutant models. We found that PM_2.5 were associated with cardiovascular hospital visits (RR = 1.006; 95% CI 1.000, 1.011) and results remained similar after adjustment for PM_10-2.5 (RR = 1.005; 95% CI 0.998, 1.013). There was a borderline association between PM_10-2.5 and cardiovascular hospital visits (RR = 1.007; 95% CI 0.997, 1.016), which disappeared after controlling for PM_2.5 (RR = 1.000; 95% CI 0.988, 1.013). The associations appeared to be stronger in the cold season and among the elderly (≥ 75 years). The findings of this study suggested significant adverse effects of PM_2.5, but no independent effects of PM_10-2.5 on cardiovascular hospital visits. Additional studies are needed to confirm these findings.

Temporal variation of post-accident atmospheric 137Cs in an evacuated area of Fukushima Prefecture: Size-dependent behaviors of 137Cs-bearing particles

The concentrations of ¹³⁷Cs in the air, which were divided into coarse (>1.1 μm ϕ) and fine (<1.1 μm ϕ) fractions of particulate matter (PM), were measured from October 2012 to December 2014 in an area evacuated after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Total atmospheric ¹³⁷Cs concentrations showed a clear seasonal variation, with high concentrations during summer and autumn related to the dominant easterly wind blowing from the highly radioactivity contaminated area. This seasonal peak was dominated by ¹³⁷Cs in the coarse PM fraction. The ¹³⁷Cs specific activity (massic ¹³⁷Cs concentration) in the coarse PM was also found to increase significantly in summer, whereas that in the fine PM showed no variability during the year. These results show that coarse and fine ¹³⁷Cs-bearing PM have different origins and behaviors in the resuspension process. The seasonal variation in atmospheric ¹³⁷Cs concentration was well correlated with the mean ¹³⁷Cs surface contamination (deposition density) around the observation site weighted by the frequency of wind direction, indicating that the atmospheric ¹³⁷Cs concentration in the observation site was explained by the distribution of the ¹³⁷Cs surface contamination and the frequency of different wind directions. We introduced a resuspension factor corrected for wind direction, consisting of the ratio of the atmospheric ¹³⁷Cs concentration to the weighted mean ¹³⁷Cs surface contamination, which evaluated the intensity of resuspension better than the conventional resuspension factor. This ratio ranged from 5.7 × 10^-11 to 8.6 × 10^-10 m^-1 and gradually decreased during the study period.

Depletion of tropospheric ozone associated with mineral dust outbreaks

From May to September 2012, ozone reductions associated with 15 Saharan dust outbreaks which occurred between May to September 2012 have been evaluated. The campaign was performed at a mountain station located near the eastern coast of the Iberian Peninsula. The study has two main goals: firstly, to analyze the decreasing gradient of ozone concentration during the course of the Saharan episodes. These gradients vary from 0.2 to 0.6 ppb h(-1) with an average value of 0.39 ppb h(-1). The negative correlation between ozone and coarse particles occurs almost simultaneously. Moreover, although the concentration of coarse particles remained high throughout the episode, the time series shows the saturation of the ozone loss. The highest ozone depletion has been obtained during the last hours of the day, from 18:00 to 23:00 UTC. Outbreaks registered during this campaign have been more intense in this time slot. The second objective is to establish from which coarse particle concentration a significant ozone depletion can be observed and to quantify this reduction. In this regard, it has been confirmed that when the hourly particle concentration recorded during the Saharan dust outbreaks is above the hourly particle median values (N > N-median), the ozone concentration reduction obtained is statistically significant. An average ozone reduction of 5.5 % during Saharan events has been recorded. In certain cases, this percentage can reach values of higher than 15 %.

Comparison of physicochemical properties between fine (PM2.5) and coarse airborne particles at cold season in Korea

Although it has been well-known that atmospheric aerosols affect negatively the local air quality, human health, and climate changes, the chemical and physical properties of atmospheric aerosols are not fully understood yet. This study experimentally measured the physiochemical characteristics of fine and coarse aerosol particles at the suburban area to evaluate relative contribution to environmental pollution in consecutive seasons of autumn and winter, 2014-2015, using XRD, SEM-EDX, XNI, ICP-MS, and TOF-SIMS. For these experimental works, the fine and coarse aerosols were collected by the high volume air sampler for 7 days each season. The fine particles contain approximately 10 μg m(-3) of carbonaceous aerosols consisting of 90% organic and 10% elemental carbon. The spherical-shape carbonaceous particles were observed for the coarse samples as well. Interestingly, the coarse particles in winter showed the increased frequency of carbon-rich particles with high contents of heavy metals. These results suggest that, for the cold season, the coarse particles could contribute relatively more to the conveyance of toxic contaminants compared to the fine particles in the study area. However, the fine particles showed acidic properties so that their deposition to surface may cause facilitate the increase of mobility for toxic heavy metals in soil and groundwater environments. The fine and coarse particulate matters, therefore, should be monitored separately with temporal variation to evaluate the impact of atmospheric aerosols to environmental pollution and human health.

Short-term exposure to fine and coarse particles and mortality: A multicity time-series study in East Asia

Few studies on size-specific health effects of particulate matter have been conducted in Asia. We examined the association between both fine and coarse particles (PM2.5 and PM10-2.5) and mortality across 11 East Asian cities from 4 countries (Korea, Japan, Taiwan, and China). We performed a two-stage analysis: we generated city-specific estimates using a time-series analysis with a generalized additive model (Quasi-Poisson distribution), and estimated the overall effects by conducting a meta-analysis. Each 10-μg/m(3) increase in PM2.5 (lag01) was associated with an increase of 0.38% (95% confidence interval = 0.21%-0.55%) in all causes mortality, 0.96% (0.46%-1.46%) in cardiovascular mortality, and 1% (0.23%-1.78%) in respiratory mortality. Each 10-μg/m(3) increase in PM10-2.5 (lag01) was associated with cardiovascular mortality (0.69%, [0.05%-1.33%]), although this association attenuated after controlling for other pollutants, especially PM2.5. Increased mortality was associated with increasing PM2.5 and PM10-2.5 concentrations over 11 East Asian cities.

Size-resolved fluorescent biological aerosol particle concentrations and occupant emissions in a university classroom

This study is among the first to apply laser-induced fluorescence to characterize bioaerosols at high time and size resolution in an occupied, common-use indoor environment. Using an ultraviolet aerodynamic particle sizer, we characterized total and fluorescent biological aerosol particle (FBAP) levels (1-15 μm diameter) in a classroom, sampling with 5-min resolution continuously during eighteen occupied and eight unoccupied days distributed throughout a one-year period. A material-balance model was applied to quantify per-person FBAP emission rates as a function of particle size. Day-to-day and seasonal changes in FBAP number concentration (NF ) values in the classroom were small compared to the variability within a day that was attributable to variable levels of occupancy, occupant activities, and the operational state of the ventilation system. Occupancy conditions characteristic of lecture classes were associated with mean NF source strengths of 2 × 10(6) particles/h/person, and 9 × 10(4) particles per metabolic g CO2 . During transitions between lectures, occupant activity was more vigorous, and estimated mean, per-person NF emissions were 0.8 × 10(6) particles per transition. The observed classroom peak in FBAP size at 3-4 μm is similar to the peak in fluorescent and biological aerosols reported from several studies outdoors.

PRACTICAL IMPLICATIONS

Coarse particles that exhibit fluorescence at characteristic wavelengths are considered to be proxies for biological particles. Recently developed instruments permit their detection and sizing in real time. In a mechanically ventilated classroom, emissions from human occupants were a strong determinant of coarse-mode fluorescent biological aerosol particle (FBAP) levels. Human FBAP emission rates were significant under quiet occupancy conditions and increased with activity level. Fluorescent particle emissions peaked at a diameter of 3–4 μm, which is the expected modal size of airborne particles with associated microbes. Human activity patterns, and associated coarse FBAP and total particle levels varied strongly on short timescales. Thus, the dynamic temporal behavior of aerosol concentrations must be considered when determining collection protocols for samples meant to be representative of average concentrations using time-integrated or ‘snapshot’ bioaerosol measurement techniques.

Which specific causes of death are associated with short term exposure to fine and coarse particles in Southern Europe? Results from the MED-PARTICLES project

We investigated the short-term effects of particles with aerodynamic diameter less than 2.5μm (PM2.5), between 2.5 and 10μm (PM2.5-10) and less than 10μm (PM10) on deaths from diabetes, cardiac and cerebrovascular causes, lower respiratory tract infections (LRTI) and chronic obstructive pulmonary disease (COPD) in 10 European Mediterranean metropolitan areas participating in the MED-PARTICLES project during 2001-2010. In the first stage of the analysis, data from each city were analyzed separately using Poisson regression models, whereas in the second stage, the city-specific air pollution estimates were combined to obtain overall estimates. We investigated the effects following immediate (lags 0-1), delayed (lags 2-5) and prolonged exposure (lags 0-5) and effect modification patterns by season. We evaluated the sensitivity of our results to co-pollutant exposures or city-specific model choice. We applied threshold models to investigate the pattern of selected associations. For a 10μg/m(3) increase in two days' PM2.5 exposure there was a 1.23% (95% confidence interval (95% CI): -1.63%, 4.17%) increase in diabetes deaths, while six days' exposure statistically significantly increased cardiac deaths by 1.33% (95% CI: 0.27, 2.40%), COPD deaths by 2.53% (95% CI: -0.01%, 5.14%) and LRTI deaths by 1.37% (95% CI: -1.94%, 4.78%). PM2.5 results were robust to co-pollutant adjustments and alternative modeling approaches. Stronger effects were observed in the warm season. Coarse particles displayed positive, even if not statistically significant, associations with mortality due to diabetes and cardiac causes that were more variable depending on exposure period, co-pollutant and seasonality adjustment. Our findings provide support for positive associations between PM2.5 and mortality due to diabetes, cardiac causes, COPD, and to a lesser degree to cerebrovascular causes, in the European Mediterranean region, which seem to drive the particles short-term health effects.

Short-term effects of PM2.5, PM10 and PM2.5-10 on daily mortality in The Netherlands

INTRODUCTION

Information on the relationship between levels of particulate matter (PM) smaller than 2.5 μm and mortality rates in Europe is relatively sparse because of limited availability of PM2.5 measurement data. Even less information is available on the health effects attributable to PM2.5-10, especially for North-West Europe.

OBJECTIVES

To investigate the relationship between various PM size fractions and daily mortality rates.

METHODS

Daily concentrations of PM from the Dutch National Ambient Air Quality Monitoring Network as well as all cause and cause-specific mortality rates in The Netherlands were obtained for the period 2008-2009. Poisson regression analysis using generalized additive models was used, with adjustment for potential confounding including long-term and seasonal trends, influenza incidence, meteorological variables, day of the week, and holidays. Different measures of PM (PM2.5, PM10 and PM2.5-10) were analysed.

RESULTS

PM10 and PM2.5 levels were statistically significantly (p<0.05) associated with all cause and cause-specific deaths. For example, a 10 μg/m(3) increase in previous day PM was associated with 0.8% (95% CI 0.3-1.2) excess risk in all cause mortality for PM2.5 and a 0.6% (CI 0.2-1.0) excess risk for PM10. No appreciable associations were observed for PM2.5-10. Effects of PM10, and PM2.5 were insensitive to adjustment for PM2.5-10, and vice-versa. PM10 and PM2.5 were too highly correlated to disentangle their independent effects.

CONCLUSIONS

PM10 and PM2.5 both were significantly associated with all cause and cause-specific mortality. We were unable to demonstrate significant effects for PM2.5-10, possibly due to the lower temporal variability and the higher exposure misclassification in PM2.5-10 compared to PM10 or PM2.5. The lack of effects of PM2.5-10 in our study should therefore not be interpreted as an indication that PM2.5-10 can be considered harmless.