SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Ultrafine particles

42

While several cohort studies report associations between chronic exposure to fine particles (PM2.5) and mortality, few have studied the effects of chronic exposure to ultrafine (UF) particles. In addition, few studies have estimated the effects of the constituents of either PM2.5 or UF particles.

Concepts: Cohort study, Cohort, Epidemiology, Cultural studies, Particulate, Diesel particulate matter, Particulates, Ultrafine particles

27

Background:According to epidemiological research, exposure to rubber fumes can cause various types of cancer and can lead to an increase in death rate because of cardiovascular diseases. OBJECTIVES: In this study, we have assessed the characteristics of ultrafine particles emitted into the air during the manufacturing of rubber products using waste tires. METHODS: To assess the aerosol distribution of rubber fumes in the workplace from a product during curing, we have performed particle number concentration mapping using a handheld condensation particle counter.The particle number concentration of each process, count median diameter (CMD), and nanoparticle ratio (<100nm) were determined using an electrical low-pressure impactor (ELPI), and the surface area concentration was determined using a surface area monitor. The shape and composition of the sampled rubber fumes were analyzed using an ELPI-transmission electron microscopy grid method. Further, the rubber fume mass concentration was determined according to the Methods for the Determination of Hazardous Substances 47/2. RESULTS: The results of particle mapping show that the rubber fumes were distributed throughout the air of the workplace. The concentration was the highest during the final process of the work. The particle number concentration and the surface area concentration were 545 000cm(-3) and 640 µm(2) cm(-3), respectively, approximately 10- and 4-fold higher than those in the outdoor background.During the final process, the CMD and the nanoparticle ratio were 26nm and 94%, respectively. Most of the rubber fume particles had a compact shape because of the coagulation between particles. The main components of these fumes were silicon and sulfur, and heavy metals such as zinc were detected in certain particles. The filter concentration of the rubber fumes was 0.22mg m(-3), lower than the UK workplace exposure limit of 0.6mg m(-3). CONCLUSIONS: Therefore, the rubber manufacturing process is a potentially dangerous process that produces a high concentration of specific nanoparticles.

Concepts: Electron, Epidemiology, Nanoparticle, Particle physics, Nanomaterials, Heavy metal music, Ultrafine particles

4

BACKGROUND: Bicycle commuting in an urban environment of high air pollution is known as a potential health risk, especially for susceptible individuals. While risk management strategies aimed to reduce motorised traffic emissions exposure have been suggested, limited studies have assessed the utility of such strategies in real-world circumstances.Objectives: The potential of lowering exposure to ultrafine particles (UFP; < 0.1 mum) during bicycle commuting by reducing proximity to motorised traffic was investigated with real-time air pollution and intermittent acute inflammatory measurements in healthy individuals using their typical, and an alternative, bicycle commute route. METHODS: Thirty-five healthy adults (mean +/- SD: age = 39 +/- 11 yr; 29% female) completed two return trips, one each of their typical route (HIGH) and a pre-determined alternative route of lower proximity to motorised traffic (LOW; determined by the proportion of on-road cycle paths). Particle number concentration (PNC) and diameter (PD) were monitored in-commute in real-time. Acute inflammatory indices of respiratory symptom incidence, lung function and spontaneous sputum (for inflammatory cell analyses) were collected immediately pre-commute, and one and three hours post-commute. RESULTS: In LOW, compared to HIGH, there was a significant decrease in mean PNC (1.91 x e4 +/- 0.93 x e4 ppcc vs. 2.95 x e4 +/- 1.50 x e4 ppcc; p <= 0.001), the incidence of in-commute offensive odour detection (42 vs. 56%; p = 0.019), and the incidence of dust and soot observation (33 vs. 47%; p = 0.038) and nasopharyngeal irritation (31 vs. 41%; p = 0.007). There were no significant differences between LOW and HIGH in the commute distance and duration (12.8 +/- 7.1 vs. 12.0 +/- 6.9 km and 44 +/- 17 vs. 42 +/- 17 min, respectively), or indices of acute airway inflammation. CONCLUSIONS: Exposure to PNC (and the incidence of offensive odour and nasopharyngeal irritation) can be significantly lowered when utilising a route of reduced proximity to motorised traffic whilst bicycle commuting (without significantly affecting commute distance or duration), which may bring important benefits for both healthy and susceptible individuals.

Concepts: Immune system, Inflammation, Bicycle, Utility cycling, Commuting, Ultrafine particles, Bicycle lighting, Bicycle commuting

3

Scaffolded porous submicron particles with well-defined diameter, shape and pore size have profound impacts in drug delivery, bone-tissue replacement, catalysis, sensors, photonic crystals and self-healing materials. However, understanding the interplay between pore size, particle size, and mechanical properties of such ultrafine particles, specially at the level of individual particles and their ensemble states, is a challenge. Herein, we focus on porous calcium-silicate submicron particles with various diameters - as a model system - and perform an extensive 900+ nanoindentations to completely map out their mechanical properties at three distinct structural forms from individual submicron particles to self-assembled ensembles to pressure-induced assembled arrays. Our results demonstrate a notable “intrinsic size-effect” for individual porous submicron particles around ~200-500 nm, induced by the ratio of particle characteristic diameter to pore characteristic size distribution. Increasing this ratio results in a brittle-to-ductile transition where the toughness of the submicron particles increase by 120%. This size-effect becomes negligible as the porous particles form superstructures. Nevertheless, the self-assembled arrays collectively exhibit increasing elastic modulus as a function applied forces while pressure-induced compacted arrays exhibits no size-effect. This study will not only have an impact on tuning properties of individual scaffolded porous particles, but can have implications on self-assembled superstructures exploiting porosity and particle size to impart new functionalities.

Concepts: Particle physics, Ratio, Particle size distribution, Circle, Particle, Diameter, Photonic crystal, Ultrafine particles

2

It is known that ultrafine particles (UFP, particles smaller than 0.1 μm) can penetrate deep into the lungs and potentially have adverse health effects. However, epidemiological data on the health effects of UFP is limited. Therefore, our objective was to test the hypothesis that exposure to UFPs is associated with respiratory health status and systemic inflammation among children aged 8 to 11 years. We conducted a cross-sectional study among 655 children (43.3% male) attending 25 primary (elementary) schools in the Brisbane Metropolitan Area, Australia. Ultrafine particle number concentration (PNC) was measured at each school and modelled at homes using Land Use Regression to derive exposure estimates. Health outcomes were respiratory symptoms and diagnoses, measured by parent-completed questionnaire, spirometric lung function, exhaled nitric oxide (FeNO), and serum C reactive protein (CRP). Exposure-response models, adjusted for potential personal and environmental confounders measured at the individual, home and school level, were fitted using Bayesian methods. PNC was not independently associated with respiratory symptoms, asthma diagnosis or spirometric lung function. However, PNC was positively associated with an increase in CRP (1.188-fold change per 1000 UFP cm-3day/day (95% credible interval 1.077 to 1.299)) and an increase in FeNO among atopic participants (1.054 fold change per 1000 UFP cm-3day/day (95% CrI 1.005 to 1.106)). UFPs do not affect respiratory health outcomes in children but do have systemic effects, detected here in the form of a positive association with a biomarker for systemic inflammation. This is consistent with the known propensity of UFPs to penetrate deep into the lung and circulatory system.

Concepts: Inflammation, Epidemiology, Pulmonology, Asthma, Lung, Heart, C-reactive protein, Ultrafine particles

2

Epidemiological studies have shown that exposure to traffic-related pollutants increases incidence of adverse health outcomes. Transit users in cities across the globe commonly spend 15-45 min or more waiting at transit stops each day, often at locations with high levels of pollution from traffic. Here, we investigate the characteristics of concentration profiles of ultrafine particles (UFP) with 5 m spatial resolution across intersections, to determine the best place to site transit stops to minimize exposures. Cross-intersection UFP profiles were derived from 1744 profiles covering 90 m before and after each intersection center with a mobile monitoring platform. Measurements were made at 10 signalized intersections located at six urban sites, each with a distinct built environment, during both mornings and afternoons. Measurements were made within 1.5 m of the sidewalk and approximately at breathing height (1.5 m above ground level) to approximate sidewalk exposures. UFP profiles were strongly influenced by high emissions from vehicle stops and accelerations, and peaked within 30 m of intersection centers; from there concentrations decreased sharply with distance. Peak concentrations averaged about 90% higher than the minima along the block. They were accompanied by more frequent and larger transient concentration spikes, increasing the chance of people near the intersection being exposed to both short-term extremely high concentration spikes and higher average concentrations. The decays are somewhat larger before the intersection than after the intersection, however as siting transit stops after intersections is preferred for smooth traffic flow, we focus on after the intersection. Simple time-duration exposure calculations combined with breathing rates suggest moving a bus stop from 20 to 40-50 m after the intersection can reduce transit-users' exposure levels to total UFP substantially, in proportion to the reciprocal of the magnitude of elevation at the intersection.

Concepts: Epidemiology, Concentration, Pollution, Maxima and minima, Road, Pedestrian, Intersection, Ultrafine particles

2

Ultrafine particle (UFP) concentrations are elevated near busy roadways, however, their effects on prevalence of cardiovascular diseases, diabetes, and hypertension are not well understood. To investigate these associations, data on demographics, diseases, medication use, and time of activities were collected by in-home surveys for 704 participants in three pairs of near-highway and urban background neighborhoods in and near Boston (MA, USA). Body mass index (BMI) was measured for a subset of 435 participants. Particle number concentration (PNC, a measure of UFP) was collected by mobile monitoring in each area. Intra-neighborhood spatial-temporal regression models (approximately 20 m resolution) were used to estimate hourly ambient PNC at the residences of participants. We used participant time activity information to adjust annual average residential PNC values and assign individualized time activity adjusted annual average PNC exposures (TAA-PNC). Using multivariate logistic regression models, we found an odds ratio (OR) of 1.35 (95% CI: 0.83, 2.22) of TAA-PNC with stroke and ischemic heart diseases (S/IHD), an OR of 1.14 (95% CI: 0.81, 1.62) with hypertension, and an OR of 0.71 (95% CI: 0.46, 1.10) for diabetes. A subset analysis controlling for BMI produced slightly stronger associations for S/IHD (OR = 1.61, 95% CI: 0.88, 2.92) and hypertension (OR = 1.28, 95% CI: 0.81, 2.02), and no association with diabetes (OR = 1.09, 95% CI = 0.61, 1.96). Further research is needed with larger sample sizes and longitudinal follow-up.

Concepts: Regression analysis, Myocardial infarction, Hypertension, Obesity, Stroke, Body mass index, Ischemia, Ultrafine particles

2

Land Use Regression (LUR) is a popular method to explain and predict spatial contrasts in air pollution concentrations, but LUR models for ultrafine particles, such as particle number concentration (PNC) are especially scarce. Moreover, no models have been previously presented for the lung deposited surface area (LDSA) of ultrafine particles. The additional value of ultrafine particle metrics has not been well investigated due to lack of exposure measurements and models.

Concepts: Particle physics, Nitrogen, Particulate, Smog, Air pollution, Diesel particulate matter, Particulates, Ultrafine particles

1

Urban environments typically exhibit large atmospheric pollution variation, in both space and time. In contrast to traditional monitoring networks suffering from a limited spatial coverage, mobile platforms enable personalized high-resolution monitoring, providing valuable insights into personal atmospheric pollution exposure, and the identification of potential pollution hotspots. This study evaluated personal cyclist exposure to UFPs, BC and heavy metals whilst commuting near Antwerp, Belgium, by performing mobile measurements with wearable black carbon (BC) and ultrafine particle (UFP) instruments. Loaded micro-aethalometer filterstrips were chemically analysed and the inhaled pollutant dose determined from the exhibited heart rate. Considerable spatial pollutant variation was observed along the travelled routes, with distinct contributions from spatial factors (e.g. traffic intersections, urban park and market) and temporary events. On average 300% higher BC, 20% higher UFP and changing elemental concentrations are observed along the road traffic route (RT), when compared to the bicycle highway route (BH). Although the overall background pollution determines a large portion of the experienced personal exposure (in this case 53% for BC and 40% for UFP), cyclists can influence their personal atmospheric pollution exposure, by selecting less exposed commuting routes. Our results, hereby, strengthen the body of evidence in favour of further policy investments in isolated bicycle infrastructure.

Concepts: Time, Chemical element, Carbon, Nanomaterials, Toxicology, Heavy metal music, Bicycle, Ultrafine particles

1

We measured particle size distributions and spatial patterns of particle number (PN) and particle surface area concentrations downwind from the Los Angeles International Airport (LAX) where large increases (over local background) in PN concentrations routinely extended 18 km downwind. These elevations were mostly comprised of ultrafine particles smaller than 40 nm. For a given downwind distance, the greatest increases in PN concentrations, along with the smallest mean sizes, were detected at locations under the landing jet trajectories. The smaller size of particles in the impacted area, as compared to the ambient urban aerosol, increased calculated lung deposition fractions to 0.7-0.8 from 0.5-0.7. A diffusion charging instrument (DiSCMini), that simulates alveolar lung deposition, measured a fivefold increase in alveolar-lung deposited surface area concentrations 2-3 km downwind from the airport (over local background), decreasing steadily to a twofold increase 18 km downwind. These ratios (elevated lung-deposited surface area over background) were lower than the corresponding ratios for elevated PN concentrations, which decreased from tenfold to twofold over the same distance, but the spatial patterns of elevated concentrations were similar. It appears that PN concentration can serve as a nonlinear proxy for lung deposited surface area downwind of major airports.

Concepts: Airport, Ultrafine particles, World's busiest airports by passenger traffic, Delta Air Lines, Runway, Los Angeles International Airport, JetBlue Airways, Southwest Airlines