Exposure and health risk assessment of PM2.5-bound trace metals during winter in university campus in Northeast China

Atmospheric PM2.5 induce autophagy and autophagic flux blockage in HUVEC cells via ROS/TXNIP signaling: Important role of metal components

Autophagy was involved in vascular endothelial injury caused by PM_2.5, which aggravated the pathogenesis of cardiovascular diseases. However, major toxic components and underlying mechanism responsible for PM_2.5-induced autophagy remain unclear. In this study, the effects of water-extracted PM_2.5 (WE-PM_2.5) on autophagy in human umbilical vein endothelial cells (HUVEC) were studied. Our results showed WE-PM_2.5 promoted autophagosome initiation and formation, meanwhile, lysosomal function was impaired, which further caused autophagic flux blockage in HUVEC cells. Furthermore, removal of metals alleviated WE-PM_2.5-induced autophagic flux blockage, while the artificial metal mixture reproduced the WE-PM_2.5 response. Mechanistically, ROS regulated autophagy-related proteins evidenced by BECN1, LC3B and p62 expression reversed by NAC pretreatment in WE-PM_2.5-exposed cells. WE-PM_2.5 also increased TXNIP expression mediated by ROS; moreover, knockdown of TXNIP in WE-PM_2.5-exposed cells decreased BECN1 and LC3B expression, but had little effects on the expression of p62, CTSB, and CTSD, indicating WE-PM_2.5-induced TXNIP was involved in autophagosome initiation and formation rather than autophagic degradation. Collectively, WE-PM_2.5-induced ROS not only promoted autophagosome initiation and formation, but also inhibited autophagic degradation. However, as the downstream molecule of ROS, TXNIP was only involved in autophagosome initiation and formation. Importantly, WE-PM_2.5-bound metals were largely responsible for autophagic flux blockage in HUVEC cells.

Bio-accessibility and health risk assessment of some selected heavy metals in indoor dust from higher institutions in Ondo State, Nigeria

Risks of heavy metal exposure from contaminated indoor dust constitute a major threat to human health. In this paper, heavy metals in deposited indoor dust samples from four tertiary institutions in Ondo State, Nigeria-Federal University of Technology, Akure; Federal College of Agriculture, Akure; Ondo State College of Health Science Technology, Akure; and Adeyemi College of Education, Ondo-were examined. The samples were collected from each location by dusting the surfaces of doors, windows, and bookshelves in lecture rooms, hostels, laboratories, and libraries, homogenized into a representative composite, and analyzed for Cr, Pb, Cd, Cu, and Zn using a flame atomic absorption spectrophotometer (FAAS) to assess their potential health risk to humans. Cu had the highest mean metal concentration in the range (0.18-0.31 mg/kg) and Cd had the lowest (ND-0.02 mg/kg) in the study. Samples from Federal College of Agriculture had the highest metal concentration, while those from Ondo State College of Health Science Technology had the lowest. The average daily dose (ADD) through ingestion was determined to be the key exposure pathway in a non-carcinogenic investigation followed by ADD through dermal contact and ADD via inhalation accordingly. Despite this, the hazard quotients (HQ) and hazard indices (HI) were well below the safety limit of one. The study established that carcinogenic effect cannot be experienced with exposure to the studied dust samples. To retain the status, it is suggested that a reasonable level of safety and tight rules be implemented.

Response of PM2.5-bound elemental species to emission variations and associated health risk assessment during the COVID-19 pandemic in a coastal megacity

The coronavirus (COVID-19) pandemic is disrupting the world from many aspects. In this study, the impact of emission variations on PM_2.5-bound elemental species and health risks associated to inhalation exposure has been analyzed based on real-time measurements at a remote coastal site in Shanghai during the pandemic. Most trace elemental species decreased significantly and displayed almost no diel peaks during the lockdown. After the lockdown, they rebounded rapidly, of which V and Ni even exceeded the levels before the lockdown, suggesting the recovery of both inland and shipping activities. Five sources were identified based on receptor modeling. Coal combustion accounted for more than 70% of the measured elemental concentrations before and during the lockdown. Shipping emissions, fugitive/mineral dust, and waste incineration all showed elevated contributions after the lockdown. The total non-carcinogenic risk (HQ) for the target elements exceeded the risk threshold for both children and adults with chloride as the predominant species contributing to HQ. Whereas, the total carcinogenic risk (TR) for adults was above the acceptable level and much higher than that for children. Waste incineration was the largest contributor to HQ, while manufacture processing and coal combustion were the main sources of TR. Lockdown control measures were beneficial for lowering the carcinogenic risk while unexpectedly increased the non-carcinogenic risk. From the perspective of health effects, priorities of control measures should be given to waste incineration, manufacture processing, and coal combustion. A balanced way should be reached between both lowering the levels of air pollutants and their health risks.

Soluble arsenic species in total suspended particles and their health risk and origin implication: A case study in Taiyuan, China

The inhalation is one of important exposure ways to arsenic. Traditionally, the health risk of arsenic exposure from particulate matter (PM) was assessed by using total arsenic, which may erroneously estimate the health risk of arsenic since the toxicity of arsenic depends on its chemical species and not all arsenic in PM is bio-accessible. Herein, total suspended particles (TSP) were collected from Taiyuan in China during whole year of 2018, and the species and concentrations of arsenic in TSP were investigated in order to more accurately assess the health risk of arsenic exposure from TSP and evaluate the possible sources of arsenic in TSP. Total arsenic varied within 1.16-28.4 ng/m³ with a mean value of 7.40 ng/m³, which exceeded the standard limit of China (6 ng/m³). Two arsenic species, As⁵⁺ and As³⁺, were detected out in soluble fractions of TSP, with As⁵⁺ as dominant species. Total arsenic, soluble arsenic and soluble As⁵⁺ in TSP revealed closed correlation each other, indicating that they may originate from similar anthropogenic and crust sources. Soluble As³⁺ showed no obvious correlations with total arsenic, implying that soluble As³⁺ has different dominant sources. The ratio of As⁵⁺/As³⁺ significantly varied within 1.08-32.5 and the percentages of soluble arsenic in total arsenic varied within 50%-93%, implying that arsenic in TSP of Taiyuan has multiple sources and none of them stably dominated during 2018. Non-carcinogenic risk and carcinogenic risk indicators calculated with soluble arsenic species showed significant difference to that calculated with total arsenic or soluble arsenic when TSP contained equivalent As⁵⁺ and As³⁺, verifying that it is necessary and more accurate to assess the health risk of arsenic exposure from TSP by using soluble arsenic species, rather than total arsenic or soluble arsenic.

Modeling Spatial Distribution and Determinant of PM2.5 at Micro-Level Using Geographically Weighted Regression (GWR) to Inform Sustainable Mobility Policies in Campus Based on Evidence from King Abdulaziz University, Jeddah, Saudi Arabia

Air pollution is fatal. Fine particles, such as PM2.5, in ambient air might be the cause of many physical and psychological disorders, including cognitive decline. This is why educational policymakers are adopting sustainable mobility, and other policy measures, to make their campuses carbon-neutral; however, car-dependent cities and their university campuses are still lagging behind in this area. This study attempts to model the spatial heterogeneity and determinants of PM2.5 at the King Abdulaziz University campus in Jeddah, which is ranked first among the Saudi Arabian universities, as well as in the MENA region. We developed four OLS and GWR models of different peak and off-peak periods during weekdays in order to estimate the determinants of the PM2.5 concentration. The number of cars, humidity, temperature, windspeed, distance from trees, and construction sites were the estimators in our analysis. Because of a lack of secondary data at a finer scale, we collected the samples of all dependent and independent variables at 51 locations on the KAU campus. Model selection was based on RSS, log-likelihood, adjusted R2, and AICc, and a modal comparison shows that the GWR variant of Model-2 outperformed the other models. The results of the GWR model demonstrate the geographical variability of the PM2.5 concentration on the KAU campus, to which the volume of car traffic is the key contributor. Hence, we recommend using the results of this study to support the development of a car-free and zero-carbon campus at KAU; furthermore, this study could be exploited by other campuses in Saudi Arabia and the Gulf region.

Characteristics of Particulate Matter at Different Pollution Levels in Chengdu, Southwest of China

Air pollution is becoming increasingly serious along with social and economic development in the southwest of China. The distribution characteristics of particle matter (PM) were studied in Chengdu from 2016 to 2017, and the changes of PM bearing water-soluble ions and heavy metals and the distribution of secondary ions were analyzed during the haze episode. The results showed that at different pollution levels, heavy metals were more likely to be enriched in fine particles and may be used as a tracer of primary pollution sources. The water-soluble ions in PM2.5 were mainly Sulfate-Nitrate-Ammonium (SNA) accounting for 43.02%, 24.23%, 23.50%, respectively. SO42−, NO3−, NH4+ in PM10 accounted for 34.56%, 27.43%, 19.18%, respectively. It was mainly SO42− in PM at Clean levels (PM2.5 = 0~75 μg/m3, PM10 = 0~150 μg/m3), and mainly NH4+ and NO3− at Light-Medium levels (PM2.5 = 75~150 μg/m3, PM10 = 150~350 μg/m3). At Heavy levels (PM2.5 = 150~250 μg/m3, PM10 = 350~420 μg/m3), it is mainly SO42− in PM2.5, and mainly NH4+ and NO3− in PM10. The contribution of mobile sources to the formation of haze in the study area was significant. SNA had significant contributions to the PM during the haze episode, and more attention should be paid to them in order to improve air quality.

Toxic metals in outdoor/indoor airborne PM2.5 in port city of Northern, China: Characteristics, sources, and personal exposure risk assessment

Outdoor and indoor PM_2.5 samples were simultaneously collected over four seasons (2017-2018) in Caofeidian, China, and analyzed for 15 elements to investigate the characteristics, sources, and health risks of PM_2.5-bound metals. Source-specific PM_2.5-bound metals were analyzed using positive matrix factorization, combined with the conditional probability function and potential source contribution function model. The health risks were evaluated using the health risk assessment model, which included the exposure parameters of indoor and outdoor activities of Chinese residents. The annual median of PM_2.5 concentrations (89.68 μg/m³) and total metals (2.67 μg/m³) from the outdoor samples significantly surpassed that of the indoor samples (51.56 μg/m³) and total metals (1.51 μg/m³) (P < 0.05). In addition, the indoor/outdoor concentration ratios indicated that most indoor metals mainly originated from outdoor emission sources. In the annual analysis of PM_2.5-bound metal sources, this study identified five metal sources: coal combustion, resuspended dust, traffic emissions, fuel combustion sources, and industrial sources, among which industry sources (36.6%) contributed the most. The non-carcinogenic risks of metals for adults (2.81) and children (2.80) all exceed the acceptable non-carcinogenic risk level (1). The non-carcinogenic risk of Mn (1.46 for children, 1.48 for adults) was a key factor in the total non-carcinogenic risk. The total carcinogenic risk of metals for children (3.75 × 10^-5) was above the acceptable level (1.0 × 10^-6) but within the tolerant limit (1.0 × 10^-4), and that for adults (1.48 × 10^-4) was above the tolerant limit. The lifetime carcinogenic risk of Cr⁶⁺ had the highest proportion of the total carcinogenic risk for children (87.5%) and adults (87.8%). Our results revealed that both adults and children suffered carcinogenic and non-carcinogenic risks from the PM_2.5-bound metals in Caofeidian. The corresponding emission control measures of metals in atmosphere should be considered.

Source-specific health risk assessment of PM2.5-bound heavy metals based on high time-resolved measurement in a Chinese megacity: insights into seasonal and diurnal variations

The health effects of PM2.5 associated heavy metals have caused wide public concern. To more accurately assess source-specific health risks of PM2.5-bound heavy metals, and to formulate a cost-effective control strategy to health risk reduction, it is necessary to have a better understanding of the temporal variation of source-specific health risks. For this purpose, hourly PM2.5 and associated heavy metals were measured during four seasons in 2018-2019 in a Chinese megacity. A method integrating positive matrix factorization (PMF) with the health risk assessment model was used to quantify the source-specific health risks. Results showed that the total hazard index (HI) of PM2.5-bound heavy metals was 1.35, higher than the safety level, the sum cancer risks (R) of carcinogenic elements (Cr, Co, Ni and As) were 2.8 × 10-5, implying nonnegligible risks. Industrial source 1 (61.3%), which was related with Mn posed the largest non-cancer risk, while coal combustion (36.1%) and industrial source 1 (34.9%) posed most of the cancer risk, and slightly fluctuated with seasons. Health risks of most resolved sources were higher in autumn and winter than in other seasons. In terms of the diurnal variation, they were the lowest in the afternoon. Besides, the health risks of vehicle source had a peak value in rush hours. Different scenarios were simulated to understand the influences of time resolutions and sampling periods on source-specific risk assessment. The results showed the cancer risks of coal combustion and industrial source 1 calculated from the dataset with reduced sampling periods were different from those calculated from the whole dataset. We conclude that source-specific health risks of heavy metals show seasonal and diurnal variations, which suggests that targeted strategies should be adopted on the basis of seasonal and diurnal cycles to protect public health. In addition, a sufficient sampling period is required to generate representative and reliable results for source-specific health risk assessment.

Speciation and bioaccessibility of heavy metals in PM2.5 in Baoding city, China

The health risks and toxicity of heavy metals (HMs) in PM_2.5 are not only associated with their total amounts, but also with their species and bioaccessibility. In this study, the speciation (fractions) and bioaccessibility of HMs (Pb, Cd, Cr, Cu and Zn) as well as their correlations in fine particulate matter (PM_2.5) samples from four seasons were studied. A sequential extraction procedure was applied to divide the studied HMs into four fractions: acid-soluble fraction (F1), reducible fraction (F2), oxidative fraction (F3) and residual fraction (F4). The simulated body fluids (gastrointestinal and lung phases) were used for in vitro tests in order to evaluate the bioaccessibility of HMs. The distribution of HMs in PM_2.5 was season and element dependent. It was found that Zn was the most abundant element among the five measured metals and followed by Pb, Cu, Cr and Cd. The total contents of each HM in different seasons were in the following order: winter > autumn > spring > summer. The studied HMs were mainly concentrated in acid-soluble fraction (F1) with high bioaccessibility (p < 0.05) except for Cr. Zn, Pb and Cu possessed the highest bioaccessibility in summer while Cd and Cr were the highest in winter. In vitro tests indicated that HMs in PM_2.5 were much more accessible to gastrointestinal fluids rather than lung phase (Gamble's solution). A significant correlation was found between the results from the optimized BCR sequential extraction and solubility bioaccessibility research consortium (SBRC). The fractions extracted by SBRC were consistent with the first two fractions extracted by the sequential extraction method.

Chemical Characterization of Two Seasonal PM2.5 Samples in Nanjing and Its Toxicological Properties in Three Human Cell Lines

PM2.5 pollution is of great concern in China due to its adverse health effects. Many diseases have been proven to be associated with PM2.5 components, but the effects of chemical characteristics of PM2.5 on toxicological properties, especially in different human organs, are poorly understood. In this study, two seasonal PM2.5 samples (summer and winter) were collected in Nanjing, and their chemical compositions (heavy metals, water-soluble ions, organic carbon (OC), and elemental carbon (EC)) were analyzed. Human lung epithelial carcinoma cells (A549), human hepatocellular liver carcinoma cells (HepG2), and human neuroblastoma cells (Sh-Sy5y) were employed to evaluate the toxicological properties of the collected PM2.5. The results showed that the average mass concentrations of PM2.5 were lower in summer (51.3 ± 21.4 μg/m3) than those in winter (62.1 ± 21.5 μg/m3). However, the mass fractions of heavy metals, OC, and EC exhibited an opposite seasonal difference. Among all tested fractions, water-soluble ions were the major compositions of particles in both summer and winter, especially the secondary ions (SO42−, NO3− and NH4+). Besides, the ratio of OC/EC in PM2.5 was greater than two, indicating serious secondary pollution in this area. The NO3–/SO42− ratio (< 1) suggested that fixed sources made important contributions. The toxicological results showed that PM2.5 in the summer and winter significantly inhibited cell viability (p < 0.01) and induced intracellular reactive oxygen species (ROS) production (p < 0.01). Moreover, the viability inhibition in A549, Sh-Sy5y, and HepG2 cells was more prominent in summer, especially at high PM2.5 (400 μg/mL) (p < 0.05), and the induction of reactive oxygen species (ROS) in A549 and Sh-Sy5y cells was also more evident in summer. Such seasonal differences might be related to the variations of PM2.5 components.

Seasonal Characteristics of the Chemical Composition of Fine Particles in Residences of Nanjing, China

Indoor fine particulate matter (PM2.5) and its chemical composition is important for human exposure as people spend most of their time indoors. However, few studies have investigated the multiseasonal characteristics of indoor PM2.5 and its chemical composition in China. In this study, the chemical composition of PM2.5 samples in residences was analyzed over four seasons in Nanjing, China. Indoor water-soluble ions exhibited similar seasonal variations (winter > autumn > summer > spring) to those from outdoors (winter > autumn > spring > summer) except in summer. Whereas, indoor metallic elements exhibited a different seasonal pattern from that of outdoors. The highest concentrations of indoor metallic elements were observed in summer when the outdoor concentrations were low. The different seasonal variations of the chemical composition between indoor and outdoor PM2.5 indicated that people should consider both indoor and outdoor sources to reduce their exposure to air pollutants in different seasons. The carcinogenic risks for metallic elements were within the acceptable levels, while manganese (Mn) was found to have potential noncarcinogenic risk to humans. More attention should be paid to the pollution of Mn in the study area in the future. Moreover, the cumulative effect of noncarcinogenic PM2.5-bound elements should not be ignored.

Bioavailability/speciation of arsenic in atmospheric PM2.5 and their seasonal variation: A case study in Baoding city, China

Arsenic (As) can be easily enriched in atmospheric particulate matters (PMs), especially in fine particulate matters (PM_2.5). In this study, thirty two PM_2.5 samples were collected in four seasons in Baoding, China, where the haze pollution was very serious in recent years. The total contents, species and bioavailability of arsenic in PM_2.5 samples were investigated. Species of arsenic in the PM_2.5 samples were discriminated as five fractions using a sequential extraction method: non-specifically sorbed fraction (F1), specifically-sorbed fraction (F2), amorphous and poorly-crystalline hydrous oxides of Fe and Al fraction (F3), well-crystallized hydrous oxides of Fe and Al fraction (F4) and residual fraction (F5). Bioavailabilities of arsenic in the PM_2.5 samples were evaluated by in vitro tests using both solubility bioavailability research consortium (SBRC) and Gamble's solution extraction methods. The total volume concentrations of As in PM_2.5 were significantly higher in winter than the other seasons. However, the highest mass concentration of As was found in spring. Scanning electron microscopy (SEM) characterization indicated that the physical morphology of the particles varied in different seasons. Significant differences of fraction distribution and BFs were found between different seasons. Arsenic in PM_2.5 samples mainly presented in F1 with high bioavailability factor (BF), especially for the samples in summer. In vitro tests indicated that arsenic in PM_2.5 could be dissolved more easily in gastric phase rather than intestinal and lung phases. There was a significant correlation between species and in vitro tests. Interestingly, a synergy effect was found between F2 and F3. Health risk assessment indicated that arsenic in PM_2.5via inhalation exposure for both children and adults could cause adverse effects. Principal component analysis suggested that the arsenic in PM_2.5 was from the similar sources between summer and autumn, winter and spring, respectively.

Distribution, inhalation and health risk of PM2.5 related PAHs in indoor environments

To investigate the potential cancer risk resulting from exposure to air pollutants, polycyclic aromatic hydrocarbons (PAHs) bound to airborne particles (PM_2.5) were assessed in one outdoor environment and four indoor environments before and during the Spring Festival of 2015. The average total PAH concentration was site-dependent, and the concentration decreased before and during the Spring Festival. Fluoranthene (Flt) was the most commonly occurring among the 16 priority PAHs, and benzo(a)pyrene (BaP) accounted for the largest portion of the total carcinogenic potency of PAHs in PM_2.5. The average BaP levels, in both indoor and outdoor environments, considerably exceeded the maximum permissible risk level of 1 ng/m³. Hazard quotients were found to be much less than 1, indicating little risk in terms of non-carcinogenic effects. Carcinogenic health risks resulting from possible carcinogens were determined to be much less than 1.00E-06. According to the California and WHO reference protocol, using empty room data to estimate the carcinogenic health risk produced values that were 10% lower than those calculated using outdoor environmental data.

Pollution Characteristics and Human Health Risks of Elements in Road Dust in Changchun, China

Road dust, which contains trace elements and certain organic matter that can be harmful to human health, plays an important role in atmospheric pollution. In this paper, concentrations of 16 elements in the road dust of Changchun, China were determined experimentally. A total of 100 samples were collected using plastic brushes and dustpans, and the elements were analyzed by an inductively coupled plasma optical emission spectrometer (ICP-OES). It was indicated that the elements could be divided into major and trace elements. The concentration of trace elements followed the trend: mercury (Hg) > manganese (Mn) > zinc (Zn) > lead (Pb) > chromium (Cr) > copper (Cu) > vanadium (V) > arsenic (As) > nickel (Ni) > cobalt (Co) > cadmium (Cd). Contamination-level-assessment calculated by the geo-accumulation index (I_geo) showed that the pollution-level ranged from non-contaminated to extreme contamination, while the calculations of enrichment factor (EF) showed that EF values exhibited a decreasing trend: Cd > Hg > As > Pb > Cu > Co > Zn > Ni > Cr > V > Mn > Mg > Fe > Sr > Ba. In our study, ingestion was the greatest exposure pathway for humans to intake trace elements by calculating the average daily dose (ADD) from three routes (ingestion, inhalation, and dermal contact). According to the health risk assessment results, the non-carcinogenic risks that human beings suffered from these elements were insignificant. Additionally, the hazard quotient (HQ) values were approximately one-tenth in the case of children. Meanwhile, the total excess cancer risk (ECR) was also lower than the acceptable level (10⁻⁶–10⁻⁴) for both adults and children.

Risk Reduction Behaviors Regarding PM2.5 Exposure among Outdoor Exercisers in the Nanjing Metropolitan Area, China

Aims: This study aimed to describe risk reduction behaviors regarding ambient particulate matter with a diameter of 2.5 μm or less (PM_2.5) among outdoor exercisers and to explore potential factors influencing those behaviors in the urban area of Nanjing, China. Method: A cross-sectional convenience sample survey was conducted among 302 outdoor exercisers in May 2015. Descriptive analysis was used to describe demographics, outdoor physical activity patterns, knowledge of PM_2.5 and risk reduction behaviors. Multivariate logistic regression analysis was then used to explore factors that influence the adoption of risk reduction behaviors. Results: The most common behavior to reduce PM_2.5 exposure was minimizing the times for opening windows on hazy days (75.5%), and the least common one was using air purifiers (19.3%). Two thirds of respondents indicated that they wore face masks when going outside in the haze (59.5%), but only 13.6% of them would wear professional antismog face masks. Participants adopting risk reduction behaviors regarding PM_2.5 exposure tended to be females, 50–60 year-olds, those with higher levels of knowledge about PM_2.5 and those who had children. Conclusions: These findings indicate the importance of improving knowledge about PM_2.5 among outdoor exercisers. Educational interventions should also be necessary to guide the public to take appropriate precautionary measures when undertaking outdoor exercise in high PM_2.5 pollution areas.