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Passive air samplers were used to monitor polychlorodibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorobiphenyls (dl-PCBs) between 2020 and 2022 in four residential areas around Bien Hoa hot spot (BHS) including Trung Dung (TD), Tan Phong (TP), Quang Vinh (QV), and Buu Long (BL). The total toxic equivalents of PCDD/Fs and dl-PCBs (∑TEQs) were highest in the TD area, from 284 to 642 fg TEQ/PUF day. Next was the QV area, where ∑TEQs ranged from 229 to 569 fg TEQ/PUF day. Then, ∑TEQs varied from 205 to 503 fg TEQ/PUF day in the TP area. The lowest ∑TEQs were between 179 and 385 fg TEQ/PUF day in the BL area. The temporal, spatial, and seasonal variations in concentrations of PCDD/Fs and dl-PCBs were related to the prevailing wind direction and the distance from each area to the dioxin hot spot. The average ∑TEQs for all four areas surrounding BHS in the dry season (423 fg TEQ/PUF day) were 1.4 times higher than in the rainy season (303 fg TEQ/PUF day). Health risk assessments from airborne dioxin exposure were estimated using the average daily doses through inhalation (ADDI). The ADDI for residents surrounding BHS ranged from 14.6 to 208 fg TEQ/kg BW/day. The ADDI values by areas were as follows: 23.2-208 fg TEQ/kg BW/day in the TD, 18.7-184 fg TEQ/kg BW/day in the QV, 16.7-163 fg TEQ/kg BW/day in the TP, and 14.6-125 fg TEQ/kg BW/day in the BL. These ADDI values remained within and below the 10% threshold of the WHO-recommended tolerable daily intake (100-400 fg TEQ/kg BW/day). It is necessary to control the excavation activities inside the BHS and cover the temporary storage sites of dioxin-contaminated materials to minimize the emissions of PCDD/Fs and dl-PCB into the ambient air.

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Chlorinated paraffins (CPs) are chlorinated alkane mixtures widely used as flame retardants and plasticizers in multiple industrial products. Systematic research on how homolog-specific properties affect their atmospheric behaviors is limited. Herein, we investigated the levels of short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) in long-timescale, seasonal, and size-fractioned particles in the urban area of Dalian, a coastal city in northern China. The average SCCP and MCCP concentrations in particles with diameters ≤ 10 µm were 3.36 and 4.89 ng/m3, respectively, and a general increase in the SCCP concentration was observed from 2.59 ng/m3 in 2018 - 2019 to 7.84 ng/m3 in 2021 - 2023. CP levels and patterns showed significant seasonal variation, with a higher abundance of C11-13Cl7-9 in winter and C10-12Cl5 in summer. Elevated particle levels in winter and high temperatures in summer contributed to the seasonal variations. SCCPs and MCCPs were concentrated on particles with diameters of < 1 µm and their geometric mean diameter increased with the increasing carbon and chlorine numbers. Total Daily intake of SCCP and MCCP was calculated to be 0.15 and 0.22 ng/kg bw/day for adults. 53.1 %, 8.5 %, and 38.4 % of inhaled SCCPs, and 60.6 %, 7.6 %, and 31.8 % of inhaled MCCPs deposited into the head airway, tracheobronchial region, and alveolar region, respectively. This study reports on how homolog-specific physicochemical properties alter the temporal variations, size distributions, and inhaled fractions of CPs.

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Next-generation risk assessment (NGRA) has emerged as a promising alternative to non-animal studies owing to the increasing demand for the risk assessment of inhaled toxicants. In this study, NGRA was used to assess the inhalation risks of two biocides commonly used as humidifier disinfectants: polyhexamethylene guanidine phosphate (PHMG-p) and chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT). Human bronchial epithelial cell transcriptomic data were processed based on adverse outcome pathways and used to establish transcriptome-based points of departure (tPODs) for each biocide. tPOD values were 0.00500-0.0510 µg/cm2 and 0.0342-0.0544 µg/cm2 for PHMG-p and CMIT/MIT, respectively. tPODs may provide predictive power comparable to that of traditional animal-based PODs (aPODs). The tPOD-based NGRA determined that both PHMG-p and CMIT/MIT present a high inhalation risk. Moreover, the identified PHMG-p posed a higher risk than CMIT/MIT, and children were identified as more susceptible population compared to adults. This finding is consistent with observations from actual exposure events. Our findings suggest that NGRA with transcriptomics offers a reliable approach for risk assessment of specific humidifier disinfectant biocides, while acknowledging the limitations of current models and in vitro systems, particularly regarding uncertainties in pharmacokinetics (PK) and pharmacodynamics (PD).

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Air pollution in opencast coal mine areas is a critical issue, resulting in harmful severe effects on human health. Therefore, it is essential to understand the air pollution factors and to assess the risks to humans. This study evaluated the potential risks (carcinogen and non-carcinogen) of inhalation exposure to PM10-bound heavy metals and Polycyclic Aromatic Hydrocarbons (PAHs) in an open pit mine in northern Colombia. During February-May 2022, PM10 samples were collected at eight sites. Heavy metals (i.e., Al, Cr(VI), Mn, Cu, Zn, As, Pb) and PAHs (thirteen priority PAHs, and one non-priority PAH) levels linked to PM10 were analyzed by X-ray fluorescence and gas chromatography-mass spectrometry, respectively. PM10 concentrations were found to range between 4.70 and 59.90 µg m-3. Out of the three different zones of the study area (i.e., North Zone, South Zone, and Populated Zone), the North Zone recorded the highest daily average concentrations of Cr(VI) (104.16 ng m-3), Mn (28.39 ng m-3), Cu (33.75 ng m-3), Zn (57.99 ng m-3), As (44.92 ng m-3), and Pb (27.13 ng m-3). The fraction of the analyzed heavy metals at all monitoring sites was 82%-89% for Al, followed by Cr(VI) with 3%-6%. Cr(VI) was the major contributor to the carcinogenic risk values, while Cu, Cr(VI), and As were the main drivers for the non-carcinogenic risk. The average cancer risk range for heavy metals was 3.30 × 10-04 -5.47 × 10-04. On the other hand, the cancer risk for PAHs exposure was acceptable. The average incremental lifetime cancer risk (ILCR) values varied between 2.87 × 10-07 and 4.21 × 10-07. Benzo[a]pyrene contributed to 54%-56% of the total risk from inhalation of PM10-bound PAHs, while Indeno[1,2,3-cd]pyrene contributed to 16%-19%. Based on the Monte Carlo sensitivity analysis, exposure to Cr(VI) was the main factor affecting cancer risk in the North, South, and Populated Zones. A suitable risk assessment and management plan requires understanding PM10-bound heavy metals and PAHs concentration levels as well as their potential health risks, mainly in open-cast coal mine zones. Our study found that people living near open-pit mines face potential health risks, so it is crucial to establish policies and regulations to control emission sources.

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Exposure to a total of 51 targeted and non-targeted polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and alkylated derivatives associated with size-segregated aerosol was investigated in rural kitchens using liquefied petroleum gas (LPG), mixed biomass (MB) and firewood (FW) fuels in northeastern India. The averaged PM10-associated parent-, alkylated-, and oxygenated-PAHs concentrations increased notably from LPG (257, 54, and 116 ng m-3) to MB (838, 119, and 272 ng m-3) to FW-using kitchens (2762, 225, and 554 ng m-3), respectively. PAHs were preferentially associated with the PM1 fraction with contributions increasing from 80 % in LPG to 86 % in MB and 90 % in FW-using kitchens, which in turn was dominated by <0.25 µm particles (54-75 % of the total). A clear profile of enrichment of low-molecular weight PAHs in cleaner fuels (LPG) and a contrasting enrichment of high-molecular weight PAHs in biomass-based fuels was noted. The averaged internal dose of Benzo[a]pyrene equivalent was the lowest in the case of LPG (19 ng m-3), followed by MB (161 ng m-3) and the highest in FW users (782 ng m-3). Estimation of incremental lifetime cancer risk (ILCR) from PAH exposure revealed extremely high cancer risk in biomass users (factors of 8-40) compared to LPG. The potential years of life lost (PYLL) and PYLL rate averaged across kitchen categories was higher for lung cancer (PYLL: 10.55 ± 1.04 years; PYLL rate: 204 ± 426) compared to upper respiratory tract cancer (PYLL: 10.02 ± 0.05 years; PYLL rate: 4 ± 7), and the PYLL rates for biomass users were higher by factors of 9-56 as compared to LPG users. These findings stress the need for accelerated governmental intervention to ensure a quick transition from traditional biomass-based fuels to cleaner alternatives for the rural population of northeastern India.

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The multi-pathway cancer risk (CR) assessment of trihalomethanes (THM) involves considering exposure via ingestion, dermal contact, and inhalation. Inhalation occurs during showering due to the volatilization of THMs from chlorinated water to the air. When assessing inhalation risks, exposure models commonly assume that the initial THM concentration in the shower room is zero. However, this assumption is only valid in private shower rooms where single or infrequent showering events take place. It fails to account for continuous or successive showering events in shared showering facilities. To address this issue, we incorporated the accumulation of THM in the shower room air. We studied a community (population ≈ 20,000) comprising two types of residences with the same water supply: population A with private shower rooms, and population B with communal shower stalls. The total THM concentration in the water was 30.22 ± 14.45 µg L-1. For population A, the total CR was 58.5 × 10-6, including an inhalation risk of 1.11 × 10-6. However, for population B, the accumulation of THM in the shower stall air resulted in increased inhalation risk. By the tenth showering event, the inhalation risk was 2.2 × 10-6, and the equivalent total CR was 59.64 × 10-6. We found that the CR significantly increased with increasing shower duration. Nevertheless, introducing a ventilation rate of 5 L s-1 in the shower stall reduced the inhalation CR from 1.2 × 10-6 to 7.9 × 10-7.

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Polybrominated diphenyl ethers (PBDEs) have been used as flame retardants in building materials, electronics, furnishings, vehicles, airplanes, plastics, polyurethane foams, and textiles for many years. Currently, the primary commercial mixtures, penta-, octa-, and deca-BDE, are globally restricted. Still, products containing PBDEs are expected to impact waste management and the environment for many years. In January 2016, an open fire in the Santa Marta landfill close to Santiago de Chile affected the city and surroundings. The fire caused several acute health effects and an increase in emergency hospitalizations. We measured PBDE levels in the areas affected by the fire in the air (gaseous and particulate) and soil, and PBDE emissions were estimated using a dispersion model. The results showed an increase in PBDE concentrations by a factor of 2-4 one day after the start of the fire. However, PBDE concentrations measured after the fire in PM10 and the gas phase were considered low compared to other regions. Interestingly, PBDEs' patterns differed across the sites; however, BDE209 was the dominant congener for all environmental matrices. A preliminary risk assessment was conducted using the daily exposure dose (DED) by air inhalation estimation. The results showed low DED values for adults and children and suggested no direct health risk due to PBDE exposure. This study brings new data useful for future solid waste management initiatives in the country.

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Differentiated Primary human bronchial epithelial cell (dpHBEC) cultures grown under air-liquid interface (ALI) conditions exhibit key features of the human respiratory tract and are thus critical for respiratory research as well as efficacy and toxicity testing of inhaled substances (e.g., consumer products, industrial chemicals, and pharmaceuticals). Many inhalable substances (e.g., particles, aerosols, hydrophobic substances, reactive substances) have physiochemical properties that challenge their evaluation under ALI conditions in vitro. Evaluation of the effects of these methodologically challenging chemicals (MCCs) in vitro is typically conducted by "liquid application," involving the direct application of a solution containing the test substance to the apical, air-exposed surface of dpHBEC-ALI cultures. We report that the application of liquid to the apical surface of a dpHBEC-ALI co-culture model results in significant reprogramming of the dpHBEC transcriptome and biological pathway activity, alternative regulation of cellular signaling pathways, increased secretion of pro-inflammatory cytokines and growth factors, and decreased epithelial barrier integrity. Given the prevalence of liquid application in the delivery of test substances to ALI systems, understanding its effects provides critical infrastructure for the use of in vitro systems in respiratory research as well as in the safety and efficacy testing of inhalable substances.

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This systematic review investigates the emissions from ultrasonic humidifiers (e.g., cool mist humidifiers) within indoor air environments, namely soluble and insoluble metals and minerals as well as microorganisms and one organic chemical biocide. Relationships between ultrasonic humidifier fill water quality and the emissions in indoor air are studied, and associated potential adverse health outcomes are discussed. Literature from January 1, 1980, to February 1, 2022, was searched from online databases of PubMed, Web of Science, and Scopus to produce 27 articles. The results revealed clear positive proportional relationships of the concentration of microorganisms and soluble metals/minerals between fill water qualities and emitted airborne particles, for both microbial (n = 9) and inorganic (n = 15) constituents. When evaluating emissions and the consequent health outcomes, ventilation rates of specific exposure scenarios affect the concentrations of emitted particles. Thus, well-ventilated rooms may alleviate inhalation risks when the fill water in ultrasonic humidifiers contains microorganisms and soluble metals/minerals. Case reports (n = 3) possibly due to the inhalation of particles from ultrasonic humidifier include hypersensitivity pneumonitis in adults and a 6-month infant; the young infant exhibited nonreversible mild obstructive ventilator defect. In summary, related literature indicated correlation between fill water quality of ultrasonic humidifier and emitted particles in air quality, and inhalation of the emitted particles may cause undesirable health outcomes of impaired respiratory functions in adults and children.

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Inhalation exposure to polycyclic aromatic hydrocarbons (PAHs) from indoor solid fuel combustion poses a high health risk, and PAHs bound to particles with smaller sizes (e.g., PM1.0, aerodynamic diameter ≤ 1.0 µm) should be of particular concern since they can penetrate deep into pulmonary alveoli. However, PAHs bound to PM1.0 was less studied compared with PAHs in total suspended particles or PM2.5. In this study, multiple provincial field measurements were conducted to investigate 28 PAHs bound to PM1.0 in rural Chinese homes. Daily averaged PM1.0-PAH28 concentrations ranged from 27 ng/m3 to 3795 ng/m3 (median: 233 ng/m3) and from 10 ng/m3 to 2978 ng/m3 (median: 87 ng/m3) in indoor and outdoor air, respectively. Higher concentrations were found in northern China in winter due to increased solid fuels consumption for space heating. The ambient pollution was lower during the non-heating season in Eastern China, where clean energy was preferred. Highly toxic congeners were more abundant in indoor air compared with outdoor air. The results of source apportionment revealed that solid fuel combustion was the primary contributor to rural household PM1.0-PAHs, but other sources such as vehicles cannot be overlooked. The transition to cleaner energy can reduce the indoor PM1.0-PAH28 and BaPeq-28 concentrations by 87% and 98%, respectively, and more efficient reduction was observed for highly toxic congeners. The estimated Incremental Lifetime Cancer Risk (ILCR) based on PM1.0-PAH28 ranged from 4.6 × 10-5 to 3.4 × 10-2, far exceeding the acceptable level of 10-6. Over 60% of the ILCR could be attributed to inhalation exposure during childhood and adolescence.

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Transformation of organophosphate esters (OPEs) in natural ambient air and potential health risks from coexposure to OPEs and their transformation products are largely unclear. Therefore, a novel framework combining field-based investigation, in silico prediction, and target and suspect screening was employed to understand atmospheric persistence and health impacts of OPEs. Alkyl-OPE transformation products ubiquitously occurred in urban ambient air. The transformation ratios of tris(2-butoxyethyl) phosphate were size-dependent, implying that transformation processes may be affected by particle size. Transformation products of chlorinated- and aryl-OPEs were not detected in atmospheric particles, and atmospheric dry deposition might significantly contribute to their removal. Although inhalation risk of coexposure to OPEs and transformation products in urban ambient air was low, health risks related to OPEs may be underestimated as constrained by the identification of plausible transformation products and their toxicity testing in vitro or in vivo at current stage. The present study highlights the significant impact of particle size on the atmospheric persistence of OPEs and suggests that health risk assessments should be conducted with concurrent consideration of both parental compounds and transformation products of OPEs, in view of the nonnegligible abundances of transformation products in the air and their potential toxicity in silico.

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Atmospheric bioaerosols contain live and dead biological components that can enter the human respiratory tract (HRT) and affect human health. Here, the total microorganisms in a coastal megacity, Qingdao, were characterized on the basis of long-term observations from October 2013 to January 2021. Particular attention was given to the size dependence of inhalable bioaerosols in concentration and respiratory deposition in different populations on foggy and hazy days. Bioaerosol samples stained with 4,6-diamidino-2-phenylindole (DAPI) were selected to measure the total airborne microbe (TAM) concentrations with an epifluorescence microscope, while a multiple-path particle dosimetry model was employed to calculate respiratory deposition. The mean TAM concentrations in the particle size range of 0.65-1.1 µm (TAM0.65-1.1) were 1.23, 2.02, 1.60 and 2.33 times those on sunny reference days relative to the corresponding values on days with slight, mild, moderate and severe levels of haze, respectively. The mean concentration of TAMs in the particle size range of 0.65-2.1 µm (TAM0.65-2.1) on severely hazy days was (2.02 ± 3.28) × 105 cells/m3, with a reduction of 4.16% relative to that on the reference days. The mean TAM0.65-2.1 concentration changed from (1.50 ± 1.37) × 105 cells/m3 to (1.76 ± 1.36) × 105 cells/m3, with TAM0.65-1.1 increasing from (7.91 ± 7.97) × 104 cells/m3 to (1.76 ± 1.33) × 105 cells/m3 on days with light fog days and medium fog, respectively. The modeling results showed that the majority of TAM0.65-2.1 deposition occurred in the extrathoracic (ET) region, followed by the alveolar (AL) region. When different populations were examined separately, the deposition doses (DDs) in adult females and in children ranked at the minimum value (6.19 × 103 cells/h) and maximum value (1.08 × 104 cells/h), respectively. However, the inhalation risks on polluted days, such as hazy, foggy and mixed hazy-foggy (HF) days, were still below the threshold for adverse impacts on human health.

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Due to the SARS-CoV-2 pandemic and restricted occupancy in work and school settings, there is a heightened risk for Legionella infection. An increase of stagnation in water pipe systems with limited water usage stimulates biofilm build-up, further facilitating Legionella proliferation. Individuals can inhale infected water aerosols and develop Legionellosis that can progress into mild flu-like symptoms or severe pneumonia. While SARS-CoV-2 vaccinations have been introduced globally, there is a concern for bacterial coinfections as individuals resume normal activities. Even with new SARS-CoV-2 variants circulating, Legionella persists as a public health threat as vulnerable communities' restrictions fluctuate. Proper water monitoring and management are critical while reopening communities. This article features Legionella characteristics and novel case reports amidst the pandemic. This article encourages greater awareness for building managers to minimize water stagnancy by disinfecting water distribution systems and promotes healthcare professionals to properly diagnose other illnesses during the ongoing pandemic to reduce morbidity and mortality.

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This study is the first attempt to assess the presence of 16 priority polycyclic aromatic hydrocarbons (PAHs) enlisted by the US Environmental Protection Agency in PM2.5 and PM10 from industrial areas of Odisha State, India. During 2017-2018, bimonthly sampling of PM10 and PM2.5 was carried out for 24 h in the industrial and mining areas of Jharsuguda and Angul in Odisha during the pre-monsoon, monsoon, and post monsoon seasons. Highest mean concentration of ∑16PAHs in PM2.5 was observed during the post monsoon (170 ng/m3) period followed by pre-monsoon (48 ng/m3) and monsoon (16 ng/m 3) periods, respectively. A similar trend of ∑16PAHs was also observed in PM10 with higher levels observed during post monsoon (286 ng/m3) followed by pre-monsoon (81 ng/m3) and monsoon (27 ng/m3) seasons. Diagnostic ratios and principal component analysis suggested diesel, gasoline and coal combustion as the major contributors of atmospheric PAH pollution in Odisha. Back trajectory analysis revealed that PAH concentration was affected majorly by air masses originating from the northwest direction traversing through central India. Toxic equivalents ranged between 0.24 and 94.13 ng TEQ/m3. In our study, the incremental lifetime cancer risk ranged between 10-5 and 10-3, representing potential cancer risk.

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Fused filament fabrication (FFF) or 3D printing is a growing technology used in industry, cottage industry and for consumer applications. Low-cost 3D printing devices have become increasingly popular among children and teens. Consequently, 3D printers are increasingly common in households, schools, and libraries. Because the operation of 3D printers is associated with the release of inhalable particles and volatile organic compounds (VOCs), there are concerns of possible health implications, particularly for use in schools and residential environments that may not have adequate ventilation such as classrooms bedrooms and garages, etc. Along with the growing consumer market for low-cost printers and printer pens, there is also an expanding market for a range of specialty filaments with additives such as inorganic colorants, metal particles and nanomaterials as well as metal-containing flame retardants, antioxidants, heat stabilizers and catalysts. Inhalation of particulate-associated metals may represent a health risk depending on both the metal and internal dose to the respiratory tract. Little has been reported, however, about the presence, speciation, and source of metals in the emissions; or likewise the effect of metals on emission processes and toxicological implications of these 3D printer generated emissions. This report evaluates various issues including the following: metals in feedstock with a focus on filament characteristics and function of metals; the effect of metals on the emissions and metals detected in emissions; printer emissions, particle formation, transport, and transformation; exposure and translation to internal dose; and potential toxicity on inhaled dose. Finally, data gaps and potential areas of future research are discussed within these contexts.

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Inhaled chemical/material exposures are a ubiquitous part of daily life around the world. There is a need to evaluate potential adverse effects of both single and repeat exposures for thousands of chemicals and an exponentially larger number of exposure scenarios (eg, repeated exposures). Meeting this challenge will require the development and use of in vitro new approach methodologies (NAMs); however, 2 major challenges face the deployment of NAMs in risk assessment are (1) characterizing what apical outcome(s) acute assays inform regarding the trajectory to long-term events, especially under repeated exposure conditions, and (2) capturing interindividual variability as it informs considerations of potentially susceptible and/or vulnerable populations. To address these questions, we used a primary human bronchial epithelial cell air-liquid interface model exposed to ozone (O3), a model oxidant and ubiquitous environmental chemical. Here we report that O3-induced proinflammatory gene induction is attenuated in repeated exposures thus demonstrating that single acute exposure outcomes do not reliably represent the trajectory of responses after repeated or chronic exposures. Further, we observed 10.1-, 10.3-, 14.2-, and 7-fold ranges of induction of interleukin (IL)-8, IL-6, heme oxygenase 1, and cyclooxygenase 2 transcripts, respectively, within in our population of 25 unique donors. Calculation of sample size estimates that indicated that 27, 24, 299, and 13 donors would be required to significantly power similar in vitro studies to identify a 2-fold change in IL-8, IL-6, HMOX1, and cyclooxygenase 2 transcript induction, respectively, to inform considerations of the uncertainty factors to reflect variability within the human population for in vitro studies.

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BACKGROUND: Hydrogen peroxide and ozone have been used as chemical decontamination agents for N95 masks during supply shortages. If left behind on the masks, the residues of both chemicals represent a potential health hazard by skin contact and respiratory exposure. AIM: Characterization of hydrogen peroxide and ozone residues on mask surfaces after chemical decontamination. METHODS: Various N95 masks were decontaminated using two commercial systems employing either aerosol spray or vaporization of hydrogen peroxide in the presence of ozone. Following the decontamination, the masks were aired out to eliminate moisture and potential chemical residues. The residual hydrogen peroxide and ozone were monitored in the gas phase above the mask surface, and hydrogen peroxide residue directly on mask surfaces using a colorimetric assay. FINDINGS: After decontamination, hydrogen peroxide and ozone were detectable in the gas phase in the vicinity of masks even after 5 h of aeration. Hydrogen peroxide was also detected on all studied masks, and levels up to 56 mg per mask were observed after 0.5 h of aeration. All residues gradually decreased with aeration, likely due to decomposition and vaporization. CONCLUSION: Hydrogen peroxide and ozone were present on N95 masks after decontamination. With appropriate aeration, the gaseous residue levels in the vicinity of the masks decreased to permissible levels as defined by the US Occupational Safety and Health Administration. Reliable assays to monitor these residues are necessary to ensure the safety of the mask users.

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Environmentally persistent free radicals (EPFRs) was considered unrecognized composition of air pollutants and might help explain the long-standing medical mystery of why non-smokers develop tobacco-related diseases like lung cancer. EPFRs in airborne fine particulate matter (PM2.5) can induce oxidative and DNA damage when inhaled. We assessed the inhalation risk of EPFRs in PM2.5 and factors influencing this risk in Beijing as a large city with frequent haze events. The average concentration of EPFRs in PM2.5 was 6.00 × 1017 spins/m3 in spring, autumn, and winter; lower concentrations were recorded in the summer. To estimate the daily inhalation risk of EPFRs in PM2.5, we used the equivalent EPFRs in cigarette tar. The average daily inhalation exposure of EPFRs in PM2.5 was estimated to be the equivalent of 33.1 cigarette tar EPFRs per day (range: 0.53-226.9) during both haze and non-haze days. The major factors influencing EPFR concentrations in the atmosphere were precipitation and humidity, which reduced airborne concentrations. Levels of PM2.5 and carbon monoxide were positively correlated with EPFR concentrations. The health risks of inhaling airborne EPFRs could be significant and should be recognized and quantified.

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In order to assess and optimize frequently used in vitro inhalation bioaccessibility procedures for heavy metals in the inhalation risk assessment, in vivo inhalation bioavailability of Pb in simulated atmosphere fine particles (PM2.5) from aging soils spiked with lead compounds and field soils in lead-zinc mining areas was investigated via intranasally instilled experiments with these PM2.5 suspensions to mice and Pb bioaccessibility was extracted by using four frequently used in vitro procedures (Gamble Solution, simulated lung fluid, simulated epithelial lung fluid and artificial lysosomal fluid). Mouse exposure experiments showed that Pb was mainly distributed in the liver, kidneys, blood and spleen. Based on the kidney model, in vitro inhalation bioaccessibility of Pb extracted with optimized Gamble Solution, in which solid to liquid ratio (S/L) was optimized to 1:1000 g ml-1 and DTPA was proved to be the key effective component, showed a strong linear relationship with its in vivo inhalation bioavailability (y = 1.07x - 3.86, R2 = 0.73). Moreover, in vitro bioaccessible and bioavailable fractions of Pb were mainly from acid exchangeable and reducible fractions of Pb in PM2.5. Altogether, optimized Gamble Solution was suggested for the analysis of in vitro bioaccessibility for risk-based assessments.

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Short-chain chlorinated paraffins (SCCPs) were added to the Stockholm Convention on Persistent Organic Pollutants (POPs) at the eighth meeting of the conference of the parties in 2017. As a consequence, increasing environmental attention and international regulation on SCCPs is expected in the future. Inhalation uptake of particulate matter (PM) was an important exposure pathway for POPs into the human body. In the present study, a total of eighty PM2.5 samples were collected in the four seasons of the year at an urban site (Shandong University, Jinan) in Shandong province to investigate the seasonal changes of SCCPs and their inhalation exposure risks to human health. The concentrations of SCCPs ranged from 9.80 to 105 ng m-3, with the mean value of 38.7 ng m-3. The highest concentrations of SCCPs were detected in winter, while the lowest concentrations were in summer. SCCPs concentrations were positively correlated with the mass concentrations of PM2.5 (r = 0.629, p < 0.01), and negatively correlated with the ambient temperature (r = -0.447, p < 0.01). The SCCPs congeners with 10 carbon atoms (C10 congeners) and 7 chlorine numbers (Cl7 congeners) were the predominant congeners, which contributed 35% and 37% of the total SCCPs contamination, respectively. The average inhalation exposure was estimated to be 1.75 × 10-4 mg kg-1 day-1 for adults, which is much lower than the "no observed adverse effect level" (NOAEL) of 100 mg kg-1 day-1 given by European risk assessment for SCCPs.

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