Studying the characteristics of new particle formation (NPF) is important as it is generally recognized as a major contributor to particle pollution in urban environments. We investigated NPF events that occurred during a 1-year period in the urban environment of Brisbane, Australia, using a neutral cluster and air ion spectrometer (NAIS) which is able to monitor both neutral and charged particles and clusters down to a size of 0.8 nm. NPF events occurred on 41% of days, with the occurrence rate of 7% greater in the summer than in the winter. We derived the first diurnal event distribution of NPF events anywhere in the world and showed that the most probable starting time of an NPF event was near 08:30 a.m., being about an hour earlier in the winter than in the summer. During NPF days, 10% of particles were charged. The mean neutral and charged particle concentrations on NPF days were, respectively, 49% and 14% higher than those on non-event days. The mean formation rate of 2–3 nm particles during an NPF event was 20.8 cm⁻³ s⁻¹. The formation rate of negatively charged particles was about 10% higher than that of positively charged particles. The mean particle growth rate in the size range up to 20 nm was 6.2 nm h⁻¹. These results are compared and contrasted with corresponding values that have been derived with the scanning mobility particle sizer (SMPS) at the same location and with values that have been reported with the NAIS at other locations around the world. This is the first comprehensive study of the characteristics of NPF events over a significantly long period in Australia.

Particulate matter with diameters <2.5 μm (i.e., PM₂.₅) has multiple natural and anthropological sources. The association between PM₂.₅ and the exacerbation of respiratory allergy and asthma has been well studied, but the components of PM₂.₅ that are responsible for allergies have not yet been determined. Here, we elucidated the effects of aqueous and organic extract of PM₂.₅ collected during four seasons in November 2014–December 2015 in two cities (Kawasaki, an industrial area and Fukuoka, an urban area affected by transboundary pollution matter) of Japan on respiratory health. Ambient PM₂.₅ was collected by high-volume air samplers and extracted into water soluble and lipid soluble components. Human airway epithelial cells, murine bone marrow-derived antigen-presenting cells (APC) and splenocytes were exposed to PM₂.₅ extracts. We measured the cell viability and release of interleukin (IL)-6 and IL-8 from airway epithelial cells, the DEC205 and CD86 expressions on APCs and cell proliferation, and TCR and CD19 expression on splenocytes. The water-soluble or aqueous extracts, especially those from Kawasaki in fall, had a greater cytotoxic effect than the lipid-soluble or organic extracts in airway epithelial cells, but they caused almost no pro-inflammatory response. Extract of fall, especially the aqueous extract from Fukuoka, increased the DEC205 and CD86 expressions on APC. Moreover, aqueous extracts of fall, summer, and spring from Fukuoka significantly increased proliferation of splenocytes. Organic extract of spring and summer from Kawasaki significantly elevated the TCR expression, and organic extract of summer from Kawasaki decreased the CD19 expression. These results suggest that PM₂.₅ extract samples are responsible for cytotoxicity in airway epithelial cells and for activating APCs and T-cells, which can contribute to the exacerbation of respiratory diseases such as asthma. These effects can differ by PM₂.₅ components, collection areas and seasons.

The structure and organization of acoustic signals arise through evolutionary processes and adaptive pressures on each species. During learning, natural or anthropogenic factors, such as high noise levels in urban areas, pose challenges to acoustic communication in birds. Many species adjust their acoustic signals to higher noise levels by increasing the frequency of vocalizations. The objectives of this study were to compare the dominant frequency of songs among birds dwelling in forest fragments distant from and near to urban areas, establish correlations between the dominant frequency of song and noise levels in these environments and verified the difference of response between oscines, suboscines and non-passerines. We recorded vocalizations of birds between July/2013 and November/2014 in four forest fragments, two of them near and two distant from urban areas. We used Audacity software to measure the dominant frequency. We measured the ambient noise by a calibrated sound pressure level meter in decibels (dBA) in each of the forest fragments. We analyzed 3740 vocalizations of nine tropical bird species. Forest fragments near to urban areas have higher noise levels than more distant forest fragments. Eight of nine studied species presented higher dominant frequencies of songs in forest fragments near to urban areas. Only one species, Myiothlypis flaveola, did not change the dominant frequency of song between the four analyzed forest fragments. The difference in dominant frequency between the forest fragments distant and closer to the urban areas did not vary between oscines, suboscines and non-passerines. Eight tropical birds exhibited higher dominant frequencies of song in forest fragments near urban areas with high level of ambient noise. Oscine, suboscine and non-passerine showed song variations. Bird species that have differences in the vocalization dominant frequency can be used in environmental monitoring and in ethological studies, as they are sensitive to high noise levels.Noise pollution caused by the vehicular traffic and urbanization are correlates with changes in the vocalization of tropical birds in forest fragments.

A limited but emerging body of evidence is suggestive for a beneficial association between contact with green spaces and glucose homeostasis in adults; however, such an evidence for children is scarce. We evaluated the association between time spent in green spaces and fasting blood glucose (FBG) levels and impaired fasting glucose (IFG, FBG≥110 mg/dL) in a population-based multicentric sample of 3844 Iranian schoolchildren aged 7–18 years (2015). Participants were instructed to report the average hours per week spent in green spaces separately during each season and in each type of green space (parks, woods/other natural green spaces, and private gardens/agricultural field) for a 12-month period preceding the interview. We developed linear and logistic mixed effects models with centre as random effect to evaluate the association of time spent in green spaces (separately for each type as well as all types together) with FBG and IFG, respectively, controlled for a wide range of covariates including household indicators of socioeconomic status. We observed inverse associations between time spent in green spaces, especially in natural green spaces, and FBG levels. Specifically, 1.83 h increase in the total time spent in green spaces was associated with −0.5 mg/dl (95% confidence intervals: −0.9, −0.1) change in FBG levels. We also observed reduced risk of IFG associated with time spent in green spaces; however, the association was statistically significant only for the time spent in natural green spaces. There were suggestions for stronger associations for those residing in urban areas and those from lower socioeconomic status groups; however, the interaction terms for socioeconomic status and urbanity were not statistically significant. Further longitudinal studies are required to replicate our findings in other settings with different climates and population susceptibilities.

Urban agriculture plays an important role in sustainable food supply. However, because of the atmospheric pollution and soil contamination associated with urban areas, this activity may be of concern. In fact, contamination of soil with metals and the transference of contaminants to vegetables can represent health and safety risks associated with urban agriculture. The objective of this study was to evaluate the concentrations of selected trace metals (cadmium, copper and lead) in three lettuce cultivars produced in three different urban gardens in the metropolitan region of Belo Horizonte, Brazil and their respective soils. Samples of lettuce and soil were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (AAS-GF), respectively, and their transfer coefficients were calculated. The methods were optimized and were fit for the purpose. Copper was the prevalent metal found in soils and lettuce, with an average of 27.9 ± 13.9 and 0.608 ± 0.157 mg kg⁻¹ respectively, followed by lead (19.4 ± 7.7 and 0.037 ± 0.039 mg kg⁻¹), and cadmium (0.16 ± 0.03 and 0.009 ± 0.005 mg kg⁻¹). Cadmium presented the largest transfer coefficients, ranging from 0.34 to 1.84 with an average of 0.92 ± 0.45, which may indicate a potential risk of accumulation in vegetables in the case of high soil contamination. A significant positive correlation was observed (p < 0.01) between cadmium in lettuce and in soil. Even though lead concentrations varied in the soils from the different urban areas, ranging from 11.88 to 30.01 mg kg⁻¹, no significant difference (p < 0.05) was found among the lettuce, probably due to its low mobility (transfer coefficient = 0.02). The copper and cadmium levels found in lettuce indicate safe lettuce production in the three urban gardens.

The abundance of silver nanoparticles (AgNPs) in consumer products has led to their environmental release and therefore to concern about their impact on human health. The ingestion of AgNP-contaminated soil from urban sites is an important exposure pathway, especially for children. Given the limited information on oral bioaccessibility of soil Ag, we used a physiologically based extraction test (PBET) to evaluate the bioaccessibility of AgNPs and AgNO₃ from soil digestion. The AgNPs underwent several biochemical transformations, including their simultaneous dissolution and agglomeration in gastric fluid followed by the disintegration in the intestinal fluid of the agglomerates into NPs containing silver and chlorine. Therefore, Ag-containing soil exposed the intestine to nanoparticulate Ag in forms that were structurally different from the original forms. The bioaccessibility of AgNPs (0.5 ± 0.05%–10.9 ± 0.7%) was significantly lower than that of AgNO₃ (4.7 ± 0.6%–14.4 ± 0.1%), as a result of the lower adsorption of nanoparticles to soil residues during the digestive process. For the soils tested, the bioaccessibility of AgNPs increased with decreasing clay contents and lower pH. By identifying the soil properties that control AgNP bioaccessibility, a more efficient and accurate screening can be performed of soil types that pose the greatest health risk associated with AgNP exposure.

For human health benefits it is crucial to see if carcinogenic air pollutants like polycyclic aromatic hydrocarbons (PAHs) are reduced accordingly along with the control of the criteria pollutants including fine particles (PM₂.₅). A number of studies documented that enhanced temporary emission control during the 2014 Asia-Pacific Economic Cooperation summit (APEC) in Beijing resulted in substantial drops of observed ambient PM₂.₅, as well as PAHs, in urban areas of Beijing, yet it is not clear whether PM₂.₅-bound PAHs in the rural areas were also lowered during the APEC. Here filter-based PM₂.₅ samples were collected at a rural site in northeast of Beijing, and analyzed for 25 PAHs before (Oct. 27-Nov. 2, 2014), during (Nov. 3–12, 2014) and after (Nov. 13, 2014–Jan. 14, 2015) the APEC. Observed concentrations of PM₂.₅, OC and EC during the APEC dropped by about 30%, however, average PM₂.₅-bound PAHs and their incremental lifetime cancer risk (ILCR), 25.65 ng/m³ and 3.2 × 10⁻⁴, remained almost unchanged when compared to that of 25.48 ng/m³ and 3.5 × 10⁻⁴, respectively, before the APEC. After the APEC with the start of wintertime central heating in urban Beijing on Nov. 15, 2014, average total concentration of PAHs and their ILCR highly elevated and reached 118.25 ng/m³ and 1.5 × 10⁻³, respectively. Source apportioning by positive matrix factorization (PMF) revealed that coal combustion was the largest source that contributed 63.2% (16.1 ng/m³), 78.5% (20.1 ng/m³) and 56.1% (66.3 ng/m³) to the total PAHs before, during and after the APEC, respectively. Uncontrolled residential coal use during the APEC was found to be the reason for unabated levels of PAHs, and the largely aggravated PAHs after the APEC was resulted from increased coal consumption for wintertime residential heating. Our results suggested reducing emission from residential coal combustion is crucial to mitigate carcinogenic PAHs in ambient air, especially in rural areas.

Recent studies have indicated that urban streets can be hotspots for emissions of methane (CH4) from leaky natural gas lines, particularly in cities with older natural gas distribution systems. The objective of the current study was to determine whether leaking sewer pipes could also be a source of street-level CH4 as well as nitrous oxide (N2O) in Cincinnati, Ohio, a city with a relatively new gas pipeline network. To do this, we measured the carbon (δ13C) and hydrogen (δ2H) stable isotopic composition of CH4 to distinguish between biogenic CH4 from sewer gas and thermogenic CH4 from leaking natural gas pipelines and measured CH4 and N2O flux rates and concentrations at sites from a previous study of street-level CH4 enhancements (77 out of 104 sites) as well as additional sites found through surveying sewer grates and utility manholes (27 out of 104 sites). The average isotopic signatures for δ13C-CH4 and δ2H-CH4 were −48.5‰ ± 6.0‰ and −302‰ ± 142‰. The measured flux rates ranged from 0.0 to 282.5 mg CH4 day−1 and 0.0–14.1 mg N2O day−1 (n = 43). The average CH4 and N2O concentrations measured in our study were 4.0 ± 7.6 ppm and 392 ± 158 ppb, respectively (n = 104). 72% of sites where fluxes were measured were a source of biogenic CH4. Overall, 47% of the sampled sites had biogenic CH4, while only 13% of our sites had solely thermogenic CH4. The other sites were either a source of both biogenic and thermogenic CH4 (13%), and a relatively large portion of sites had an unresolved source (29%). Overall, this survey of emissions across a large urban area indicates that production and emission of biogenic CH4 and N2O is considerable, although CH4 fluxes are lower than those reported for cities with leaky natural gas distribution systems.

As a transitional zone between riverine and marine environments, an estuary plays an important role for the sources, accumulation and transport of microplastics. Although estuarine environments are hotspots of microplastic pollution, the correlation between microplastic pollution and aquatic organisms is less known. Here we investigated microplastic pollution in wild oysters Saccostrea cucullata from 11 sampling sites along the Pearl River Estuary in South China. The microplastic abundances in oysters ranged from 1.4 to 7.0 items per individual or from 1.5 to 7.2 items per gram tissue wet weight, which were positively related to those in surrounding waters. The oysters near urban areas contained significantly more microplastics than those near rural areas. Fibers accounted for 69.4% of the total microplastics in oysters. Microplastic sizes varied from 20 to 5000 μm and 83.9% of which were less than 100 μm. Light color microplastics were significantly more common than dark color ones. Based on the results, oysters are recommended as a biomonitor for the microplastic pollution in estuaries.

The state of practice for noise assessment utilizes established standards for emission and propagation modelling of linear and point sources. Recently, land use regression (LUR) modelling has emerged as an alternative method due to relatively low data and computing resource demands. However, a limitation of LUR modelling is that is does not account for noise attenuation and reflections by features of the built environment. This study demonstrates and validates a method that combines the two modelling frameworks to exploit their respective strengths: Emission and propagation based prediction of traffic noise, the predominant source of noise at the level of streetscapes, and a LUR-based correction for noise sources that vary on spatial scales beyond the streetscape.Multi-criteria analysis, location-allocation modelling and stakeholder consultation identified 220 monitoring sites with optimal coverage for a 1-week sampling period. A subset of sites was used to validate a road traffic noise emission and propagation model and to specify a LUR model that predicted the contribution of other sources. The equivalent 24-h sound pressure level (LAeq) for all sites was 62.9 dBA (SD 6.4). This varied by time of day, weekday, types of roads and land uses. The traffic noise emission model demonstrated a high level of covariance with observed noise levels, with R² values of 0.58, 0.60 and 0.59 for daytime, nighttime and 24-h periods, respectively. Combined with LUR models to correct for other noise sources, the hybrid models R² values were 0.64, 0.71 and 0.67 for the respective time periods.The study showed that road traffic noise emissions account for most of the variability of total environmental noise in Toronto. The combined approach to predict fine resolution noise exposures with emission and receptor-based models presents an effective alternative to noise modelling approaches based on emission and propagation or LUR modelling.