Mean Particle Mass Concentration Research Articles

Monitoring Particulate Matter Air Pollution in Urban Centers: New Insights from Douala, Cameroon

Air quality progressively deteriorates as urbanization, motorization and economic activities increase. Aerosol particles smaller than 2.5µm (PM2.5), a widespread form of pollution is an emergent threat to human health, the environment, quality of life, and the world’s climate. The composition of these particles is an important aspect of interest not only related to possible health and environmental effects of the elemental content but the elemental determination which also adds valuable information for source apportionment. This study investigates and evaluates the level of PM2.5 in Douala, Cameroon. Particles were collected using a cyclone that separates the PM2.5 from the air stream and impacts them on polycarbonate filters which were changed every 24-hour sampling period. Samples were analyzed for particulate mass concentration, black carbon (BC) and trace elements. Trace element analysis was done by EDXRF (energy dispersive x-ray fluorescence spectroscopy). Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Br, Sr, and Pb were identified and quantified for samples. Local meteorology was used to study variations in PM2.5 mass concentrations. Possible sources for the pollutants were also investigated. The mean particle mass concentration was 252 ± 130μg/m3 while BC attained a maximum of 6.993μg/m3. The influence of leaded gasoline was inferred while combustion and road traffic were identified as the major anthropogenic sources. Trends in meteorological parameters were influenced by thunderstorms. Sea spray was identified as another major contributor to aerosol PM. This study highlights high pollution levels in Douala. Keywords: PM2.5, air quality, aerosol, mass concentration, source identification

Occupational Exposure to Particulate Matter and Volatile Organic Compounds in Two Indoor Cannabis Production Facilities.

Legal commercial cultivation and processing of cannabis is a rapidly growing industry in multiple countries. However, to date little effort has been made to characterize and identify the various occupational hazards that workers may be facing in the cannabis production industry, including airborne contaminants that may affect the human respiratory system. In the current study, we quantified occupational exposures to particulate matter (PM) and volatile organic compounds (VOCs) in various task zones of two indoor cannabis facilities in Washington State. Full-shift (8-h) area measurements of PM and VOCs were collected in each task zone. Measurement devices were placed near the employee's work area in order to attempt to estimate the personal exposure to the contaminants. In each task zone we measured particle number concentration, particle mass concentration (PMC), cumulative size distribution of the particles, and total terpene mass concentrations. The mean PMCs were greater in task zones that required the employees to manipulate the cannabis plants and materials. The arithmetic mean PMC for the trim task was 60 µg m-3, preroll task was 45 µg m-3, grow task was 42 µg m-3, and the referent office area was 27 µg m-3. When comparing each task zone PMC to the office referent PMC, the trim task, and the preroll task were significantly higher than the referent group (P-values both <0.05). The arithmetic mean terpene mass concentration for the trim task was 36 mg m-3, preroll task was 9.9 mg m-3, grow task was 15 mg m-3, and for the office referent space was 4.9 mg m-3. Compared with the office space, only the trim task area had significantly elevated terpene mass concentrations (P-value <0.01). We observed a weak but statistically significant correlation between PMC and total terpene mass concentrations (rho = 0.42, P < 0.02). Overall, we observed that exposures to respiratory hazards were highest in task zones where cannabis plants and material were manipulated by workers, including the trim, preroll, and the grow task areas. These observations can help inform the employer of the task zones where exposure to respiratory hazards are the highest, and where it may be beneficial to deploy control measures to reduce worker exposures.

The unprecedented 2017–2018 stratospheric smoke event: decay phase and aerosol properties observed with the EARLINET

Abstract. Six months of stratospheric aerosol observations with the European Aerosol Research Lidar Network (EARLINET) from August 2017 to January 2018 are presented. The decay phase of an unprecedented, record-breaking stratospheric perturbation caused by wildfire smoke is reported and discussed in terms of geometrical, optical, and microphysical aerosol properties. Enormous amounts of smoke were injected into the upper troposphere and lower stratosphere over fire areas in western Canada on 12 August 2017 during strong thunderstorm–pyrocumulonimbus activity. The stratospheric fire plumes spread over the entire Northern Hemisphere in the following weeks and months. Twenty-eight European lidar stations from northern Norway to southern Portugal and the eastern Mediterranean monitored the strong stratospheric perturbation on a continental scale. The main smoke layer (over central, western, southern, and eastern Europe) was found at heights between 15 and 20 km since September 2017 (about 2 weeks after entering the stratosphere). Thin layers of smoke were detected at heights of up to 22–23 km. The stratospheric aerosol optical thickness at 532 nm decreased from values &gt; 0.25 on 21–23 August 2017 to 0.005–0.03 until 5–10 September and was mainly 0.003–0.004 from October to December 2017 and thus was still significantly above the stratospheric background (0.001–0.002). Stratospheric particle extinction coefficients (532 nm) were as high as 50–200 Mm−1 until the beginning of September and on the order of 1 Mm−1 (0.5–5 Mm−1) from October 2017 until the end of January 2018. The corresponding layer mean particle mass concentration was on the order of 0.05–0.5 µg m−3 over these months. Soot particles (light-absorbing carbonaceous particles) are efficient ice-nucleating particles (INPs) at upper tropospheric (cirrus) temperatures and available to influence cirrus formation when entering the tropopause from above. We estimated INP concentrations of 50–500 L−1 until the first days in September and afterwards 5–50 L−1 until the end of the year 2017 in the lower stratosphere for typical cirrus formation temperatures of −55 ∘C and an ice supersaturation level of 1.15. The measured profiles of the particle linear depolarization ratio indicated a predominance of nonspherical smoke particles. The 532 nm depolarization ratio decreased slowly with time in the main smoke layer from values of 0.15–0.25 (August–September) to values of 0.05–0.10 (October–November) and &lt; 0.05 (December–January). The decrease of the depolarization ratio is consistent with aging of the smoke particles, growing of a coating around the solid black carbon core (aggregates), and thus change of the shape towards a spherical form. We found ascending aerosol layer features over the most southern European stations, especially over the eastern Mediterranean at 32–35∘ N, that ascended from heights of about 18–19 to 22–23 km from the beginning of October to the beginning of December 2017 (about 2 km per month). We discuss several transport and lifting mechanisms that may have had an impact on the found aerosol layering structures.

Effects of short-term exposure to fine and ultrafine particles from indoor sources on arterial stiffness - A randomized sham-controlled exposure study.

Particulate air pollution is linked to adverse cardiovascular effects, including arterial stiffness. The aim of the study was to investigate the effect of short-term exposure to indoor fine and ultrafine particles on augmentation index (AIx), augmentation pressure (AP), and pulse wave velocity (PWV), early signs of vascular damage. We analyzed the association of particle emissions from typical indoor sources (candle burning - CB, toasting bread - TB, and frying sausages - FS) with changes in pulse wave analysis indices in 55 healthy adults in a randomized cross-over controlled exposure study. Particle mass concentration (PMC), size-specific particle number concentration (PNC) and lung-deposited particle surface area concentration (PSC) were measured during the 2 h exposure. AIx and AP were measured before, directly, 2, 4 and 24 h after exposure. PWV was measured directly and 24 h after exposure. We performed multiple mixed linear regression analyses of different particle metrics and AIx, AP and PWV. The highest mean PMC was observed during FS reaching a maximum of 210 μg/m3 PM10. The maximal PNC for UFP <100 nm was reached during CB with 2.3 million particles/cm3. PSC was similar across all three exposures (about 3000 μm2/cm³). Strongest associations between different particles metrics and arterial stiffness indices could be observed for UFP from CB and FS and for PMC from TB. The highest mean increase could be observed for the UFP fraction <10 nm, measured during CB, and AIx with an increase of 9.5%-points (95%-CI: 3.1; 15.9). PSC seemed to follow the pattern of PNC. PM10 and PM2.5 from TB led to clear changes in AIx with biggest increases for PM10 of 5.8%-points (95%-CI: 3.2; 8.4) 2 h after exposure and for PM2.5 of 8.1%-points (95%-CI: 2.5; 13.7) directly after exposure. Our study indicates effects of indoor exposure to fine and ultrafine particles on systemic arterial stiffness indices that depend on the indoor source as well as on particle metric. Differences in size-specific physical characteristics of source-specific particles might account for these differential effects. We did not observe clear and stable associations of indoor particle exposure and PWV.

Real-Time Monitoring of Spray Drift from Three Different Orchard Sprayers

In Washington State, half of all pesticide-related illnesses in agriculture result from drift, the off-target movement of pesticides. Of these, a significant proportion involve workers on another farm and orchard airblast applications. We compared the spray drift exposure reduction potential of two modern tower sprayers – directed air tower (DAT) and multi-headed fan tower (MFT), in relation to a traditional axial fan airblast (AFA) sprayer. We employed real-time particle monitors (Dylos DC1100) during a randomized control trial of orchard spray applications. Sections of a field were randomly sprayed by three alternating spray technologies – AFA, DAT and MFT – while monitors sampled particulate matter above and below the canopy at various downwind locations in a neighboring field. Geometric mean particle mass concentrations (PMC) outside the intended spray area were elevated during all applications at all of our sampling distances (16–74 m, 51–244 ft). After adjusting for wind speed and sampling height, the 75th percentile (95% confidence interval) PMC level was significantly greater during spray events than background levels by 105 (93, 120) μg/m3, 49 (45, 54) μg/m3 and 26 (22, 31) μg/m3 during AFA, DAT and MFT applications, respectively. Adjusted PMC levels were significantly different between all three sprayers. In this study, tower sprayers significantly reduced spray drift exposures in a neighboring orchard field when compared to the AFA sprayer, with the MFT sprayer producing the least drift; however these tower sprayers did do not fully eliminate drift.

Ambient exposure to coarse and fine particle emissions from building demolition

Demolition of buildings produce large quantities of particulate matter (PM) that could be inhaled by on-site workers and people living in the neighbourhood, but studies assessing ambient exposure at the real-world demolition sites are limited. We measured concentrations of PM10 (≤10 μm), PM2.5 (≤2.5 μm) and PM1 (≤1 μm) along with local meteorology for 54 working hours over the demolition period. The measurements were carried out at (i) a fixed-site in the downwind of demolished building, (ii) around the site during demolition operation through mobile monitoring, (iii) different distances away from the demolition site through sequential monitoring, and (iv) inside an excavator vehicle cabin and on-site temporary office for engineers. Position of the PM instrument was continuously recorded using a Global Positioning System on a second basis during mobile measurements. Fraction of coarse particles (PM2.5–10) contributed 89 (with mean particle mass concentration, PMC ≈ 133 ± 17 μg m−3), 83 (100 ± 29 μg m−3), and 70% (59 ± 12 μg m−3) of total PMC during the fixed-site, mobile monitoring and sequential measurements, respectively, compared with only 50% (mean 12 ± 6 μg m−3) during the background measurements. The corresponding values for fine particles (PM2.5) were 11, 17 and 30% compared with 50% during background, showing a much greater release of coarse particles during demolition. The openair package in R and map source software (ArcGIS) were used to assess spatial variation of PMCs in downwind and upwind of the demolition site. A modified box model was developed to determine the emission factors, which were 210, 73 and 24 μg m−2 s−1 for PM10, PM2.5 and PM1, respectively. The average respiratory deposited doses to coarse (and fine) particles inside the excavator cabin and on-site temporary office increased by 57- (and 5-) and 13- (and 2-) times compared with the local background level, respectively. The monitoring stations in downwind direction illustrated a logarithmic decrease of PM with distance. Energy-dispersive X-ray spectroscopy and scanning electron microscopy were used to assess physicochemical features of particles. The minerals such as silica were found as a marker of demolition dust and elements such as sulphur coming from construction machinery emissions. Findings of this study highlight a need to limit occupational exposure of individuals to coarse and fine particles by enforcing effective engineering controls.

Short-term chamber exposure to low doses of two kinds of wood smoke does not induce systemic inflammation, coagulation or oxidative stress in healthy humans

Introduction: Air pollution increases the risk of cardiovascular diseases. A proposed mechanism is that local airway inflammation leads to systemic inflammation, affecting coagulation and the long-term risk of atherosclerosis. One major source of air pollution is wood burning. Here we investigate whether exposure to two kinds of wood smoke, previously shown to cause airway effects, affects biomarkers of systemic inflammation, coagulation and lipid peroxidation.Methods: Thirteen healthy adults were exposed to filtered air followed by two sessions of wood smoke for three hours, one week apart. One session used smoke from the start-up phase of the wood-burning cycle, and the other smoke from the burn-out phase. Mean particle mass concentrations were 295 µg/m3 and 146 µg/m3, and number concentrations were 140 000/cm3 and 100 000/cm3, respectively. Biomarkers were analyzed in samples of blood and urine taken before and several times after exposure. Results after wood smoke exposure were adjusted for exposure to filtered air.Results: Markers of systemic inflammation and soluble adhesion molecules did not increase after wood smoke exposure. Effects on markers of coagulation were ambiguous, with minor decreases in fibrinogen and platelet counts and mixed results concerning the coagulation factors VII and VIII. Urinary F2-isoprostane, a consistent marker of in vivo lipid peroxidation, unexpectedly decreased after wood smoke exposure.Conclusions: The effects on biomarkers of inflammation, coagulation and lipid peroxidation do not indicate an increased risk of cardiovascular diseases in healthy adults by short-term exposure to wood smoke at these moderate doses, previously shown to cause airway effects.

Size-segregated characterization of PM10 at the EMEP site Melpitz (Germany) using a five-stage impactor: a six year study

Size-segregated particle samples were collected using a Berner 5-stage impactor (stages 1–5: 0.05–0.14–0.42–1.2–3.5–10 μm aerodynamic diameter). The means for all 169 days and for different categories of days were used for a characterization. The sorting criteria were (a) the distinction between winter (Wi, November to April) and summer (Su, May to October), (b) the distinction between air mass inflow from a sector West (W, 210 °–320 °) and from a sector East (E, 35 °–140 °). For the assignment of the air mass origin 96-h backward trajectories were used and four categories (WiW, WiE, SuW and SuE) with 48, 18, 42 and 29 days were established. The lowest mean particle mass concentrations were found for SuW and the highest for WiE with relative mass concentration distributions of 5.9, 28.2, 36.5, 18.0, and 11.4 % and 3.5, 22.7, 52.6, 16.7, and 4.5 % for stages 1–5, respectively. The mass closure for water soluble ions, water, organic material (OM) and elemental carbon (EC) accounts for 81–99 % of the gravimetric mass in Wi and for 60–81 % for Su, depending on the stage. The fractions of nitrate were relatively high for WiW while sulphate fractions are high for WiE. The estimated concentrations of secondary organic carbon (SOA) on stage 3 for WiW, WiE, SuW and SuE were 0.32, 1.25, 0.27 and 0.58 μgm−³, respectively. The highest amount of SOA is found for WiE, representing 59 % of organic carbon (OC). The highest difference in the percentages of SOA in OC was found between winter (WiW 55 %, WiE 59 %) and summer (SuW and SuE 74 %) indicating photochemical processes during long-range transport. The mean Carbon Preference Indices (CPI) are highest for SuE (stage 4: 7.57 and stage 5: 9.82) resulting mainly from plant wax abrasion in the surrounding forests. For WiE the mean PAH concentration on stage 3 (9.7 ngm−3) is about five times higher than for WiW, indicating long range transport following domestic heating and other combustion processes.

Traffic-generated airborne particles in naturally ventilated multi-storey residential buildings of Singapore: Vertical distribution and potential health risks

The main objective of the study is to quantify the mass concentration exposure levels of fine traffic-generated particles (PM 2.5) at various heights of typical multi-storey public housing buildings located in close proximity, i.e. within 30 m and along a busy major expressway in Singapore. The secondary objective is to compare the potential health risks of occupants in the buildings, associated with inhalation exposure of fine traffic-generated particulate matter, based on estimated dose rates and the lowest observed adverse effect levels (loael) at the various floors of these buildings. Two typical public housing buildings, both naturally ventilated residential apartment blocks, of point block configuration (22-storey) and slab block configuration (16-storey) were selected for the study. Particulate samples were collected for both mass and chemical analysis (OC/EC ratio) at three representative floors: the lower, the mid, and upper floors of the buildings. Key meteorological parameters such as wind speed, wind direction, ambient temperature, and relative humidity were also concurrently measured at the sampling locations. For the potential health risk analysis, the occupants have been divided into four age categories namely, infants, children (1 year), children (8–10 years) and adults. The analysis takes into account age-specific breathing rates, body weights for different age categories. Experimental results explicitly showed that PM 2.5 mean particle mass concentration was highest at the midfloors of both buildings when compared to those measured at upper and lower floors during a typical day. Although the lower floors were closest to traffic emissions, the mean particle mass concentration was lower there than that at the midfloors, which could presumably be due to the interception of PM 2.5 particles by tree leaves or the inflow of clean and drier air from higher altitude with lower aerosol burden mixing with the traffic-polluted air at the lower levels thus lowering the concentration at the lower floors similar to induced chimney effect or both. The upper floors had the least fine particulate matter mass concentration due to dilution following pronounced mixing of traffic-polluted air with ambient air. The only difference between both blocks is that at corresponding floors, the mass concentration levels for slab block is much higher than that of point block. This could be attributed to the configuration of the blocks. Observational data show the slab block tends to slow down the approaching wind thus allowing the accumulation of the fine traffic-generated particulate matter in front of the building. For point block, the HR values at the mid and lower floors suggest that occupants living in these floors experience 1.81 and 1.34 times more health risk, respectively, in contracting respiratory diseases when compared to those living at the upper floors for all age categories. Similarly, for the slab block, occupants living in the mid and lower floors had 1.62 and 1.28 times more risk, respectively, in contracting respiratory diseases when compared to those living at the upper floors for all age categories.

Adequacy of a single monitoring site for defining mean outdoor concentrations of fine particles in a demarcated residential community.

Fine and coarse inhalable particle data for 60 days from five demarcated communities in U.S. cities, each with three monitoring sites, were examined to test whether the mean particle mass concentrations measured at the three sites are equivalent within each community. The result of this kind of analysis should be useful in determining how many sites in a community are adequate to provide a reliable measure of the outdoor component of an exposure estimate in that community. Only fine particles (D < 2.5 μm, aerodynamic diameter) were found to have equivalent mean concentrations, suggesting that only one monitoring site in each community is required to provide an adequate exposure estimate of the outdoor component. However, variable concentrations of total inhalable and/or coarse (2.5 μm< D < 15 μm) particles were found, which Implies a requirement for multiple monitoring sites.

Characterization of Diesel Exhaust in a Chronic Inhalation Study

We describe characterization of the exposure atmosphere in a life-span study of rats and mice exposed to chronic inhalation of diluted diesel exhaust. Diesel exhaust was generated by one of two General Motors 1980 Model, 5.7-liter V8 diesel engines connected to an eddy current dynamometer/flywheel system and operated on the Federal Test Procedure urban driving cycle. Animals were exposed 7 hours/day, 5 days/week to exhaust at particle concentrations of approximately 7000, 3500, and 350 µg/m3 or to clean air. Throughout the 24-month study, the mean particle mass concentration remained within 5% of the target values. Measured gas concentrations of CO, CO2, NO, NO2, and hydrocarbons were roughly proportional to the dilution ratio. A combination of a Lovelace Multijet cascade impactor followed by a parallel flow diffusion battery gave mass median diameters of 0.23 to 0.26 µm averaged over complete cycles and geometric standard deviations larger than 4. The aerosol concentration profile was associated with the operating cycle. The measured diesel particle size was similar to previously reported values of particles released to the atmosphere from the same model engine.

Characterization of diesel exhaust in a chronic inhalation study.

We describe characterization of the exposure atmosphere in a life-span study of rats and mice exposed to chronic inhalation of diluted diesel exhaust. Diesel exhaust was generated by one of two General Motors 1980 Model, 5.7-liter V8 diesel engines connected to an eddy current dynamometer/flywheel system and operated on the Federal Test Procedure urban driving cycle. Animals were exposed 7 hours/day, 5 days/week to exhaust at particle concentrations of approximately 7000, 3500, and 350 micrograms/m3 or to clean air. Throughout the 24-month study, the mean particle mass concentration remained within 5% of the target values. Measured gas concentrations of CO, CO2, NO, NO2, and hydrocarbons were roughly proportional to the dilution ratio. A combination of a Lovelace Multijet cascade impactor followed by a parallel flow diffusion battery gave mass median diameters of 0.23 to 0.26 microns averaged over complete cycles and geometric standard deviations larger than 4. The aerosol concentration profile was associated with the operating cycle. The measured diesel particle size was similar to previously reported values of particles released to the atmosphere from the same model engine.