Particulate Matter Number Concentration Research Articles

Characteristics of airborne particles in stone quarrying areas: Human exposure assessment and mitigation

This investigation aims to assess the levels of human exposure to airborne particulate matter (PM) in various locations of a natural stone quarry for the first time based on simultaneous measurements of both PM mass and number concentrations (PMC and PNC). A quarry located in Danang city, Vietnam, considered to be a “hotspot” of air pollution in the city, was selected for detailed investigations. Both PMC and PNC were found to be significantly higher (1.2–6.0 times) within the quarry compared to surrounding areas. Mechanical activities during mining, notably crushing, screening, hauling, and loading stones, contributed to increased emissions of PM in the coarser mode (1–10 μm) compared to the accumulation mode (0.1–1 μm) and thus increased deposition of PM1-10 in the human upper respiratory tract. In contrast, combustion activities, especially the diesel engine exhaust from various machines and vehicles used in the quarry, resulted in increased emissions of small particles in the accumulation mode that dominated the PNC and in their deposition in the lower respiratory tract. Simultaneous measurements of PNC and PMC revealed that the PM counts were strongly associated with PM deposition in the alveolar region (accounting for ≈ 76% of total PNC of particles less than 10 μm, N10), while the PM mass concentration was a better indicator of the deposition of PM in the head airway region (≈92% of total PMC of PM10). Overall, this study demonstrates the significance of measuring both PNC and PMC to assess PM exposure levels, regional respiratory doses, and potential health effects associated with human exposure to PM generated from stone quarrying activities. The novelty of this work is the integration of real-time mass and number concentrations of PM over the size range from 20 nm to 10 μm to provide insights into respiratory deposited doses of size-fractionated PM among quarry workers.

Environmental exposure disparities in ultrafine particles and PM2.5 by urbanicity and socio-demographics in New York state, 2013–2020

BackgroundThe spatiotemporal and demographic disparities in exposure to ultrafine particles (UFP; number concentrations of particulate matter (PM) with diameter ≤0.1 μm), a key subcomponent of fine aerosols (PM2.5; mass concentrations of PM ≤ 2.5 μm), have not been well studied. ObjectiveTo quantify and compare the aerosol pollutant exposure disparities for UFP and PM2.5 by socio-demographic factors in New York State (NYS). MethodsAmbient atmospheric UFP and PM2.5 were quantified using a global three-dimensional model of chemical transport with state-of-the-science aerosol microphysical processes validated extensively with observations. We matched these to U.S. census demographic data for varied spatial scales (state, county, county subdivision) and derived population-weighted aerosol exposure estimates. Aerosol exposure disparities for each demographic and socioeconomic (SES) indicator, with a focus on race-ethnicity and income, were quantified for the period 2013–2020. ResultsThe average NYS resident was exposed to 4451 #·cm−3 UFP and 7.87 μg·m−3 PM2.5 in 2013–2020, but minority race-ethnicity groups were invariably exposed to greater daily aerosol pollution (UFP: +75.0% & PM2.5: +16.2%). UFP has increased since 2017 and is temporally and seasonally out-of-phase with PM2.5. Race-ethnicity exposure disparities for PM2.5 have declined over time; by −6% from 2013 to 2017 and plateaued thereafter despite its decreasing concentrations. In contrast, these disparities have increased (+12.5–13.5%) for UFP. The aerosol pollution exposure disparities were the highest for low-income minorities and were more amplified for UFP than PM2.5. DiscussionWe identified large disparities in aerosol pollution exposure by urbanization level and socio-demographics in NYS residents. Jurisdictions with higher proportions of race-ethnicity minorities, low-income residents, and greater urbanization were disproportionately exposed to higher concentrations of UFP and PM2.5 than other NYS residents. These race-ethnicity exposure disparities were much larger, more disproportionate, and unabating over time for UFP compared to PM2.5 across various income strata and levels of urbanicity.

Temporal Evolution of PM2.5 Levels and COVID-19 Mortality in Europe for the 2020–2022 Period

Air pollution has a strong impact on human health, from respiratory and severe pulmonary diseases to heart attack and cancer. During the 3 years of the COVID-19 pandemic, several peaks of mortality occurred, which could be related to particulate matter (PM) pollution events. The possible effects of PM (PM10 and PM2.5, with diameters less than 10 and 2.5 µm, respectively) on COVID-19 mortality have now been established. To better understand this relationship at the European level for the period 2020–2022, data from 16 representative locations in Europe (81 million people) with PM2.5 levels (µg·m−3) ranging from low to high values were analyzed using statistical methods. The analysis confirms a temporal relation between the peaks of PM2.5 exposure and COVID-19 mortality. The best correlation was obtained considering the history of exposure to PM2.5 pollution during a 2-month integration time coupled with a one-week delay for the COVID-19 mortality. Although the trend of COVID-19 mortality vs. PM2.5 levels varies among locations, the global trend was similar, giving an estimated mean value of a 40 ± 20% mortality increase per µg·m−3 PM2.5 increase. The stronger the positive (negative) gradient of the PM peak, the stronger the positive (negative) gradient of the COVID-19 mortality. These results indicate that a succession of PM pollution peaks could be more dangerous than permanent exposure to moderate pollution levels. Finally, PM number concentrations should be used in the future rather than the PM2.5 mass concentrations (µg·m−3), with the consideration of PM composition to better evaluate the effect of submicron particles on human health, particularly for other respiratory diseases. These results must be considered in the management of future pandemics.

Comparison of PM spatiotemporal variations and exposure at adjacent signalized intersection and roundabout

As urban traffic nodes, signalized intersections and roundabouts gather a large number of vehicles, forming traffic particulate matter (PM) hotspots. However, related studies have focused only on signalized intersections, and knowledge of PM characteristics on roundabouts are still scarce. For this reason, we carried out mobile and fixed-site monitoring of PM mass and number concentrations and comparative analysis, at an adjacent roundabout and intersection. The attenuation curves of PM2.5 concentrations down the departure roads from the roundabout and intersection centers showed an exponential decay, but their distribution profiles were obviously different. Particle number concentration (PNC) first increased and then decreased at the roundabout, while it was similar to PM2.5 with exponential decay at the intersection. The temporal variation of PNC in different particle sizes differed between the roundabout and intersection. A Generalized Additive Model (GAM) quantified the contribution of background concentration, Meteorological conditions, and traffic volume to PM2.5 at the roundabout and the intersection, respectively, identifying their different influential levels. Lastly, using field data of this case study, the average respiratory deposition dose (RDD) rates were estimated for adults and children. The study can help formulate effective urban traffic pollution control strategies.

Occupational protection effect of two protective devices for manual cleaning and oiling of dental handpieces on operators

Objective: To explore the occupational protective effect of different protective devices on the operators during manual cleaning and oiling of dental handpieces, and to provide a basis for the selection of appropriate protective methods. Methods: From November 2020 to December 2021, 20 high-speed dental handpieces of the same brand were selected and randomly divided into disposable protective bag group and small aerosol safety cabinet group by drawing lots, with 10 in each group. After recording the model, they were distributed to the clinical fixed consulting room for use, and were collected by specially-assigned personnel every day for manual cleaning under the protection of the two devices. By measuring the number of airborne colonies, the concentrations of particulate matter and the satisfaction of operators, the occupational protection effect of the two protective devices on operators was evaluated. Results: Under the protection of the two devices, the average number of airborne colonies after operation was less than 1 CFU/ml. When no protective device was used, the number concentration of particulate matter produced during operation was (21595.70±8164.26) pieces/cm(3). The number concentrations of particles produced by disposable protective bag group [ (6800.24±515.05) pieces/cm(3)] and small aerosol safety cabinet group [ (5797.15±790.50) pieces/cm(3)] were significantly lower than those without any protective device (P<0.001). The number concentration of particle matter of small aerosol safety cabinet group was significantly lower than that of disposable protective bag group (P<0.001). In the satisfaction evaluation of operators, small aerosol safety cabinet group [ (3.53±0.82) points] was significantly better than disposable protective bag group [ (2.23±1.10) points] (P<0.001) . Conclusion: The use of small aerosol safety cabinet during manual cleaning and oiling of dental handpieces has good protective effect, superior safety performance and strong clinical applicability, and has advantages in occupational protection of clinical operators.

Investigating the impact of relative humidity and air tightness on PM sedimentation and concentration reduction

Exposure to particulate matter (PM) has a negative impact on human health. The hygroscopicity of PM varies with the chemical composition and particle size, and the sedimentation trends leading to decreased PM concentrations also vary. However, PM hygroscopicity has mostly been considered in terms of outdoor air quality such as visibility and radiation force. Thus, in this study, the relationship between PM and ambient humidity was evaluated through two experiments based on chemical composition and PM particle size analysis, which are representative PM classification methods. Firstly, six aerosols commonly found in indoor and outdoor atmospheres were selected, and the reduction rate of PM number concentrations by particle diameter and mass concentrations (PM10 and PM2.5) was evaluated at different relative humidity(R.H) values. The results indicated that the PM concentration was effectively decreased when indoor R.H was >70%, and the spread of PM was effectively prevented when indoor R.H was >50%. Secondly, measurements were obtained from four houses with different levels of airtightness to clarify the relationship between PM and R.H in actual living environments. Higher airtightness corresponded to lower PM concentrations due to higher R.H, but this effect was not observed when the air change rate was high. Therefore, increasing airtightness to increase R.H may not be a practical solution for reducing indoor PM concentrations in all cases. Our findings suggest that indoor air quality management strategies should consider the complex interactions between PM and ambient humidity in specific building contexts.

Impacts of PM on Indoor Air Quality of Airport Terminal Buildings in a Core City of North China Plain

With the economic growth and globalization, a great deal of airports are being or planned to be constructed or retrofitted in China. The air quality in airport terminal buildings has not been studied as in-depth as airport ambient air quality. Due to its unique architectural and operational characteristics, the airport terminal buildings have individual performance of indoor air quality. The contribution of outdoor particulate matter (PM) to indoor environment and passengers’ exposure to indoor PM is not well understood. The indoor (i.e., terminal buildings) and outdoor PM concentrations with particle sizes from 0.25 to 32 μm of Tianjin Binhai International Airport (IATA: TSN) were monitored continuously during two cases in winter and summer 2020. Higher indoor PM concentrations occurred in winter as well as in the arrival halls of TSN. During winter case, the indoor sources contributed more to the indoor environment than the outdoor sources, whereas the opposite was found during summer case. Sharp variation of indoor PM number concentrations existed in particles within the range of 0.25–0.40 μm in size, with a peak number concentration at particle size of about 0.30 μm. PM with smaller particle sizes were more likely to enter the indoor environment from outdoor. The comprehensive exposure in the TSN terminal buildings was higher than those in the transportation microenvironments, residences and other buildings. Significant diurnal variations of Respiratory deposition dose (RDD) were observed under various exposure durations. Our results highlight the need for further monitoring and improving the air quality in the terminal buildings.

The associations of particulate matter short-term exposure and serum lipids are modified by vitamin D status: A panel study of young healthy adults

Particulate matter (PM) exposure is associated to the adverse change in blood lipids. Vitamin D is beneficial to lipid metabolism, but whether vitamin D levels modifies the impact of air pollutants on lipids is unclear. The purpose of the study was to investigate if vitamin D modifies the associations of PM and serum lipids in young healthy people. From December 2017 to January 2018, a panel study with five once weekly follow-ups was conducted on 88 healthy adults aged 21.09 (1.08) (mean (SD)) years on average in Guangzhou, China. We measured serum lipids, serum 25-hydroxyvitamin D (25(OH)D) concentrations (440 blood samples in total), mass concentrations of particulate matter with diameters ≤2.5 μm (PM2.5), ≤1.0 μm (PM1.0), and ≤0.5 μm (PM0.5), and number concentrations of particulate matter with diameters ≤0.2 μm (PN0.2) and ≤0.1 μm (PN0.1) at each follow-up. Linear mixed-effect models were applied to assess the interaction of vitamin D and size-fractionated PM short-term exposure on four lipid metrics. We found the interactions between 25(OH)D and size-fractionated PM exposure on blood lipids in different lags (lag 3 days and 4 days). An interquartile range increase in PM2.5, PM1.0, PM0.5 were significantly associated with increments of 12.30%, 12.99%, and 13.66% in triglycerides (TGs) at lag 4 days at vitamin D levels <15 ng/mL group, respectively. Similar results were found for PN0.2, PN0.1 and low-density lipoprotein cholesterol (LDL-C). All the associations between size-fractionated PM and blood lipids were found null statistically significant in vitamin D levels ≥15 ng/mL group.

Seasonal Distribution of Atmospheric Coarse and Fine Particulate Matter in a Medium-Sized City of Northern China.

Atmospheric particulate matter (PM) was measured continuously at an urban site in Baoji city in northern China in 2018 to investigate the seasonal distribution characteristics. Coarse PM (PM2.5–10) was more prevalent in spring, substantially due to the regional transport of dust. High loadings of coarse PM were found at night compared to daytime, which could result from high production and unfavorable dispersion conditions. Fine PM (PM2.5) constituted, on average, 54% of the total PM mass concentration, whereas it contributed more than 97% of the total PM number concentration. The number and mass concentrations of fine PM increased substantially in the winter, which was possibly due to the enhanced production of atmospheric secondary processes and coal combustion. Precursor gaseous pollutants and meteorology greatly influenced the PM distributions. Fine PM was associated more strongly with gas pollutants than coarse PM, which suggested that it largely originated from secondary production and combustion sources. High relative humidity appeared to promote the production of fine PM, whereas it facilitated the removal of coarse PM. This study highlights that different air-pollution control strategies should be used for coarse and fine PM according to the distribution characteristics and influencing factors in similar medium-sized urban areas.

A review on morphology, nanostructure, chemical composition, and number concentration of diesel particulate emissions.

Particulate matter (PM) emitted from compression ignition (CI) engines (diesel engines) has a detrimental effect on human health and the environment. The physical and chemical characteristics of PM emitted from CI-engines are influenced by engine operating conditions and fuel properties. The morphology, nanostructure, and chemical composition of PM affect its toxicity and interaction with the environment. From automotive industry perspective, these parameters influence the design of diesel particulate filters. This study presents a review of the physical and chemical characteristics of particulate emissions from the CI-engine. The present study commences with a brief description about the composition of PM emitted from CI-engine and the PMformation mechanism in CI-engine. Later on, the detailed review of PM's physical and chemical characteristics and the effect of engine operating parameters and alternative fuels on the particle number concentration, morphology, nano-structure, and oxidative reactivity of PM is presented. Online and offline methods of diesel particulate characterization and emerging chemical characterization techniques such as X-ray photoelectron spectroscopy and X-ray absorption fine structure (EXAFS) are also discussed briefly. Correlation between physical and chemical properties, and oxidative reactivityof PM is also discussed. It was found that engine operating parameters affect the physical and chemical properties of PM. Use of alternative fuels changes the diesel particulate morphology, nanostructure, and chemical composition which enhances the oxidative reactivity of PM.

Assessment of the Oxidative Potential and Oxidative Burden from Occupational Exposures to Particulate Matter.

Oxidative potential (OP) is a toxicologically relevant metric that integrates features like mass concentration and chemical composition of particulate matter (PM). Although it has been extensively explored as a metric for the characterization of environmental particles, this is still an underexplored application in the occupational field. This study aimed to estimate the OP of particles in two occupational settings from a construction trades school. This characterization also includes the comparison between activities, sampling strategies, and size fractions. Particulate mass concentrations (PM4-Personal, PM4-Area, and PM2.5-Area) and number concentrations were measured during three weeks of welding and construction/bricklaying activities. The OP was assessed by the ascorbate assay (OPAA) using a synthetic respiratory tract lining fluid (RTLF), while the oxidative burden (OBAA) was determined by multiplying the OPAA values with PM concentrations. Median (25th-75th percentiles) of PM mass and number concentrations were 900 (672-1730) µg m-3 and 128 000 (78 000-169 000) particles cm-3 for welding, and 432 (345-530) µg m-3 and 2800 (1700-4400) particles cm-3 for construction. Welding particles, especially from the first week of activities, were also associated with higher redox activity (OPAA: 3.3 (2.3-4.6) ρmol min-1 µg-1; OBAA: 1750 (893-4560) ρmol min-1 m-3) compared to the construction site (OPAA: 1.4 (1.0-1.8) ρmol min-1 µg-1; OBAA: 486 (341-695) ρmol min-1 m-3). The OPAA was independent of the sampling strategy or size fraction. However, driven by the higher PM concentrations, the OBAA from personal samples was higher compared to area samples in the welding shop, suggesting an influence of the sampling strategy on PM concentrations and OBAA. These results demonstrate that important levels of OPAA can be found in occupational settings, especially during welding activities. Furthermore, the OBAA found in both workplaces largely exceeded the levels found in environmental studies. Therefore, measures of OP and OB could be further explored as metrics for exposure assessment to occupational PM, as well as for associations with cardiorespiratory outcomes in future occupational epidemiological studies.

Urban atmospheric particle size distribution in Santiago, Chile

A monitoring campaign of the atmospheric particulate matter (PM) size distribution (between 0.25 and 10 μm in diameter (Dp)) in an urban area with high levels of air pollution between June 2018 and May, 2019 is presented. The relative contribution of 24 size fractions to the total number and mass concentration of PM was analyzed using an aerosol spectrometer. Local meteorological parameters and their effect on the PM concentrations were also evaluated. The size-fractionated particle mass concentrations showed the accumulation (Dp < 1 μm) and coarse (1 μm < Dp < 10 μm) modes. The highest contribution of the accumulation mode was observed during autumn and winter (reaching 99.7 % and 35.2 % of the total number and mass concentrations, respectively). High relative humidity and low temperatures were strongly correlated with high concentrations for the smaller PM fractions, which can be connected to the increase of residential emissions of PM derived from wood burning sources in winter months. The larger PM fractions showed higher concentrations during the spring and summer months, potentially because of dust resuspension due to the high vehicular traffic in the vicinity. High PM concentrations of the larger fractions were favored by the lack of precipitation events and stronger winds during this time of the year. The results showed the importance of the PM1 fraction to improve the source apportionment studies in urban areas and provide information about the potential health effects associated to high PM concentration events.

Associations of Particulate Matter Sizes and Chemical Constituents with Blood Lipids: A Panel Study in Guangzhou, China.

Existing evidence is scarce concerning the various effects of different PM sizes and chemical constituents on blood lipids. A panel study that involved 88 healthy college students with five repeated measurements (440 blood samples in total) was performed. We measured mass concentrations of particulate matter with diameters ≤ 2.5 μm (PM2.5), ≤1.0 μm (PM1.0), and ≤0.5 μm (PM0.5) as well as number concentrations of particulate matter with diameters ≤ 0.2 μm (PN0.2) and ≤0.1 μm (PN0.1). We applied linear mixed-effect models to assess the associations between short-term exposure to different PM size fractions and PM2.5 constituents and seven lipid metrics. We found significant associations of greater concentrations of PM in different size fractions within 5 days before blood collection with lower high-density lipoprotein cholesterol (HDL-C) and apolipoprotein A (ApoA1) levels, higher apolipoprotein B (ApoB) levels, and lower ApoA1/ApoB ratios. Among the PM2.5 constituents, we observed that higher concentrations of tin and lead were significantly associated with decreased HDL-C levels, and higher concentrations of nickel were associated with higher HDL-C levels. Our results suggest that short-term exposure to PM in different sizes was deleteriously associated with blood lipids. Some constituents, especially metals, might be the major contributors to the detrimental effects.

Impact of Aromatic Structures and Content in Formulated Fuel for Jet Engine Applications on Particulate Matter Emissions

Abstract Fuel formulation with the particular selection of fuel components is a promising approach that offers the reduction of harmful emissions without altering the combustion system performance. Each fuel component has its own combustion characteristics and hence contribution to emissions. Aromatic is one of the main components of fossil-based fuels and has a strong correlation with the formation of particulate matter (PM) emissions. Besides, aromatics presence in fuel is essential for the compatibility of fuel with the combustion system and maintaining the energy density of the fuel. In this regard, a Rolls-Royce combustor rig was used to test 16 aromatics blended with jet fuels in three different proportions. Moreover, a novel approach of flame luminosity imaging is employed to measure the PM emissions through the soot propensity profile. The results show that PM emissions increase with the proportional increase of aromatics. The di- and cyclo-aromatics produced significantly higher PM emissions compared to alkyl-benzenes. 3-Isopropylcumene tends to lowest PM formation and thus is a consideration as a selection of aromatic type in future fuels for lower PM emissions. Furthermore, it was also observed that PM number concentration measured by the extractive method with DMS 500 instrument correlates well with imaging methods for all the tested fuels. The present study provides information on particular selection of aromatic for future fuel development.

Daily Variation of Air Pollutants Near an Elevated Highway System

I-81 is an elevated viaduct and goes through the heart of Syracuse, with local businesses and communities located underneath it. The safety limit of the viaduct is ending, and the NY Department of Transportation (DOT) is looking for recommendations to rebuild the roadway using its current elevated design or lower the highway to ground level creating a community grid. People living below I-81 are concerned about increases in air pollution if I-81 is lowered. With no knowledge of current air quality levels in this community, assessing how lowering the highway would impact the neighborhood is impossible. We began an air quality monitoring campaign to measure pollutant levels simultaneously near the highway and on the ground below. Models generated by the DOT suggest traffic levels will not change if the highway is lowered. By monitoring air quality at highway and ground levels, results will offer a glimpse of potential air quality problems that could arise. To assess daily variation in traffic-related particulate matter (PM) near this highway, a site adjacent to I-81 was selected. Two high-volume cascade impactors were placed at ground and highway levels of a building to collect daily PM samples for two weeks over two seasons. Two real-time PM monitors measured PM number concentration with elevation. For fine PM at the rooftop location, the average number of particles was 1.2 times higher with a maximum of 10 times higher. Three days in summer had exceptionally high vehicle flow and had PM concentrations ranging from 4.5 to 10 times higher at highway level. Results from gravimetric analyses agreed with measured number concentrations. This data shows particle count and PM concentration are variable with elevation and suggests that vehicle emissions may be more influential at highway level, implying air quality may be affected if the community grid option is pursued.

Impact of vacuum cleaning on indoor air quality

Vacuum cleaning can be a household source of particulate matter (PM) both from the vacuum motor and from settled dust resuspension. Despite the evidence of this contribution to PM levels indoors, the effect of this source on PM composition is still unknown. In this study, four vacuum cleaners (washable filter bag less, wet, bagged and HEPA filter equipped robot) were tested for the emission rate of particulate mass and number. The detailed PM chemical characterisation included organic and elemental carbon, metals and organic speciation. PM10 emission rates from bagged vacuum operation were much higher (207 ± 99.0 μg min−1) compared with the ones obtained from wet (86.1 ± 16.9 μg min−1) and washable filter bag less vacuums (75.4 ± 7.89 μg min−1). Particle (8–322 nm) number emission rates ranged from 5.29 × 1011 (washable filter bag less vacuum) to 21.2 × 1011 (wet vacuum) particles min−1. Ratios of peak to background levels indicate that vacuuming can elevate the ultrafine particle number concentrations by a factor ranging from 4 to 61. No increase in PM mass or number concentrations was observed during the HEPA filter equipped vacuum operation. The increase in copper and elemental carbon PM10 contents during vacuuming suggested motor emissions. Organic compounds in PM10 included alkanes, PAHs, saccharides, phenolics, alcohols, acids, among others. However, it was not possible to establish a relationship between these compounds and vacuuming due to the vast array of possible household sources. The cancer risks associated with metals and PAH inhalation were negligible.

Quantifying particulate matter reduction and their deposition on the leaves of green infrastructure

The green infrastructure (GI) is identified as a passive exposure control measure of air pollution. This work examines particulate matter (PM) reduction by a roadside hedge and its deposition on leaves. The objectives of this study are to (i) quantify the relative difference in PM concentration in the presence of GI and at an adjacent clear area; (ii) estimate the total mass and number density of PM deposited on leaves of a hedge; (iii) ascertain variations in PM deposition at adult (1.5m) and child (0.6 m) breathing levels on either side of a hedge; (iv) illustrate the relationship between PM deposition to leaves and ambient PM concentration reductions; and (v) quantify the elemental composition of collected particles of the leaves on different heights and sides of hedge. PM reduction of 2–9% was observed behind hedge compared to a clear area and followed a trend of ΔPM1 >ΔPM10 >ΔPM2.5. Counting of particles was found to be an effective method to quantify deposition than weighting methods. Sub-micron particles (PM1) dominated particle deposition on leaves at all sampling points on both sides of the hedge. PM mass deposition and number concentration to the leaves on traffic-facing side was up to 36% and 58% higher at 0.6m compared with 1.5m height, respectively. Such a difference was absent on the backside of the hedge. The SEM-EDS analysis showed up to 12% higher traffic-originated particles deposited to leaves on the traffic-facing side compared to the backside. The naturally occurring particles dominated in identified particles on leaf samples from all collection points on the hedge. These new evidence expand our understanding of PM reduction of GI in the near-road environment and its variations in particle deposition, depending on height and sides of GI, which could allow a better parameterisation of dispersion-deposition models for GI assessment at micro-scale.

Thermal degradation and pollutant emission from waste printed circuit boards mounted with electronic components

Waste printed circuit boards mounted with electronic components (WPCB-ECs) are generated from electronic waste dismantling and recycling process. Air-borne pollutants, including particulate matter (PM) and volatile organic compounds (VOCs), can be released during thermal treatment of WPCB-CEs. In this study, organic substances from WPCB-ECs were pyrolyzed by both thermo-gravimetric analysis (TGA) and in a quartz tube furnace. We discovered that board resin and solder coating were degraded in a one-stage process, whereas capacitor scarfskin and wire jacket had two degradation stages. Debromination of brominated flame retardants occurred, and HBr and phenol were the main products during TGA processing of board resin. Dehydrochlorination occurred, and HCl, benzene and toluene were detected during the pyrolysis of capacitor scarfskin. Benzene formation was found only in the first degradation stage (272–372 °C), while toluene was formed both in the two degradation stages. PM with bimodal mass size distributions at diameters of 0.45–0.5 and 4–5 μm were emitted during heating WPCB-ECs. The PM number concentrations were highest in the size ranges of 0.3–0.35 μm and 1.6–2 μm. The research produced new data on pollutant emissions during thermal treatment of WPCB-ECs, and information on strategies to prevent toxic exposures that compromise the health of recyclers.

Variation in concentrations of particulate matter with various sizes in different weather conditions in mining zone

The present study was undertaken to investigate particulate matter (PMs) (PM10, PM2.5 and PM1) mass and number concentration (0.265–10 µm) along a road network in the Jharia coalfields, Dhanbad, Jharkhand, India, using a GRIMM aerosol spectrometer during different weather conditions representing dry weather (DW) and wet weather (WW). The study area was divided into 9 locations representing mining and non-mining areas. The observed values were compared with applicable standards of India (NAAQS) and the World Health Organizations (WHO). Air quality was also determined using an Air Quality Index (AQI) as per new guidelines of the Central Pollution Control Board, India. A detailed comparison between the mining and non-mining areas for the two weather conditions is presented. The PM10 and PM2.5 mass concentrations were a maximum at Godhar (GDR) (mining area) (332; 151 µg/m3, respectively) and higher as compared to the NAAQS (100; 60 µg/m3), WHO (50; 25 µg/m3) and in the non-mining area (125; 42 µg/m3, respectively) during DW; they were reduced significantly because of precipitation by 46% and 18%, respectively, during WW. PM1 and PM1–2.5 were dominant during WW and PM2.5–10 during DW. PM number concentrations (≤ 2.5 µm) were observed almost 1.5–2.5 times lower during WW while compared to DW for all sites. The values of AQI values were significantly reduced during WW compared to DW. The study revealed that concentrations of PMs and AQI values were found lower during WW compared to DW due to light precipitation.

Characterization of particulate matter from heating and cooling several edible oils

Cooking fumes produced by oils at high temperatures release large amounts of fine particulate matter (PM). Exposure to cooking fumes increases the risk of many diseases. A chamber study investigated particle emission and decay characteristics originating from six types of edible oil (olive oil, soybean oil, rapeseed oil, peanut oil, corn oil and sunflower seed oil). The experiment determined the particle number concentration and particle size distribution of PM with diameters of 0.3 μm and less, 0.3–0.5 μm and 0.5–1.0 μm (PM0.3, PM0.3-0.5 and PM0.5-1.0, respectively) during the heating and cooling of the edible oils. The effects of heating power, indoor relative humidity and ventilation conditions on the corresponding particle emission and decay characteristics of olive oil and sunflower seed oil were discussed. Since the deposition and coagulation of the particles occur simultaneously in the experimental chamber, the deposition and coagulation rates of the cooling process were calculated. Two methods were compared to obtain an accurate coagulation rate.