An increasing number of epidemiological studies have examined air pollution as a possible contributor to adverse sleep health, but results are mixed. The aims of this systematic review are to investigate and summarize the associations between exposures to air pollutants and various sleep measures across the lifespan. PubMed, CINAHL, Cochrane, Scopus, Web of Science, and PsycInfo were searched through October 2019 to identify original data-based research examining direct epidemiological associations between ambient and indoor air pollution exposures and various sleep health measures, including sleep quality, sleep duration, sleep disturbances, and daytime sleepiness. Twenty-two articles from 2010 to 2019 were selected for inclusion in this review, including a wide range of study populations (from early childhood to elderly) and locations (10 Asian, 4 North American, 3 European, 5 other). Due to variation in both exposure and outcome assessments, conducting a meta-analysis was not plausible. Twenty-one studies reported a generally positive association between exposure and poor sleep quality. While most studies focused on ambient air pollutants, five assessed the specific effect of indoor exposure. In children and adolescents, increased exposure to both ambient and indoor pollutants is associated with increased respiratory sleep problems and a variety of additional adverse sleep outcomes. In adults, air pollution exposure was most notably related to sleep disordered breathing. Existing literature generally shows a negative relationship between exposures to air pollution and sleep health in populations across different age groups, countries, and measures. While many associations between air pollution and sleep outcomes have been investigated, the mixed study methods and use of subjective air pollution and sleep measures result in a wide range of specific associations. Plausible toxicological mechanisms remain inconclusive. Future studies utilizing objective sleep measures and controlling for all air pollution exposures and individual encounters may help ameliorate variability in the results reported by current published literature.

This study reports a characterization of indoor polycyclic aromatic hydrocarbons (PAHs) associated with dust (dust-PAHs) in household evaporative coolers and their associated health effects. Extensive analysis showed that the indoor dust-PAHs stemmed mostly from pyrogenic sources (vehicular emissions) with mean total concentrations limited between 131 and 429 ng g−1. The distribution pattern of PAHs based on number of rings exhibited the following order of decreasing relative abundance: 4 > 3 > 5 > 6 > 2 rings. Results indicate that the mutagenicity of dust-PAHs exceeded their carcinogenicity, but that the potential carcinogenic effects are still significant. The mean lifetime cancer risk for different age groups for three pathways based on Model 2 (dermal (1.39 × 10−1 to 1.91 × 10−2), ingestion (2.13 × 10−3 to 8.08 × 10−3) and inhalation (1.62 × 10−7 to 4.06 × 10−7)) was 7.4–146 times higher than values predicted by Model 1 (dermal (5.13 × 10−5 to 3.03 × 10−3), ingestion (9.34 × 10−5 to 1.31 × 10−3) and inhalation (7.13 × 10−20 to 1.68 × 10−20)). Hence, exposure to dust-PAHs in household evaporative coolers lead to high risk, especially for children (less than 11 years) (HQ = 2.71 × 10−20 to 54.8 and LTCRs = 7.13 × 10−20 to 1.39 × 10−1). Strategies should be considered to eliminate such pollutants to protect people, especially children, from the non-carcinogenic and carcinogenic effects by changing household evaporative coolers with other cooling systems.

While commuting, individuals are exposed to high concentrations of urban air pollutants that can lead to adverse health effects. This study aims to assess commuters’ exposure to particulate matter (PM) when travelling by car, bicycle, metro and bus in Lisbon. Mass concentrations of PM₂.₅ and PM₁₀ were higher in the metro. On the other hand, the highest BC and PN₀.₀₁₋₁ average concentrations were found in car and bus mode, respectively. In cars, the outdoor concentrations and the type of ventilation appeared to affect the indoor concentrations. In fact, the use of ventilation led to a decrease of PM₂.₅ and PM₁₀ concentrations and to an increase of BC concentrations. The highest inhaled doses were mostly observed in bicycle journeys, due to the longest travel periods combined with enhanced physical activity and, consequently, highest inhalation rates.

Inhalation of size-dependent particle-bound polycyclic aromatic hydrocarbons (PAHs) has been extensively studied, whereas dermal absorption has not been adequately investigated. To address this knowledge gap, dermal absorption of size-dependent particle-bound PAHs was characterized through the collection of indoor air and forearm wipe samples in the setting of an indoor barbecue. The mass of size-fractioned PAHs associated with particulate matter was greater in fine particles (<1.8 μm) than in coarse particles (>1.8 μm). Gas-particle distribution of specific PAHs from barbecue fume was ascribed to both adsorption and absorption which would probably be close to equilibrium, while that from background air was dominated by absorption. Forearm-deposited amounts of particulate PAHs suggested that removal of coarse and fine particles could minimize exposure to low and high molecular-weight (MW) PAHs, respectively. Besides, the concentrations of particulate PAHs in forearms wipe were significantly correlated to their dry deposition fluxes with coarse particles, but weakly correlated to those with fine particles. This indicated that particle size would influence dermal absorption efficiency of particle-bound PAHs with fine particles prolonging dermal exposure to PAHs. Overall, higher MW particle-bound PAHs derived from barbecue fume may pose higher risk to human health by dermal absorption than lower MW PAHs.

Road dust samples from industrial, urban, and tourist areas of the international tourist city of Guilin, China, were collected to study the concentration, spatial distribution, pollution level, and health risk of potentially toxic elements (PTEs) using an array-based risk assessment model from the United States Environmental Protection Agency. The geoaccumulation index (Igₑₒ), ecological risk index, and spatial interpolation were used to investigate the road dust pollution level. The results indicated that apart from Ni and Al, the concentration of all the heavy metals (Pb, Zn, Ni, Cu, Cr, Cd, Fe, Mn, and As) were markedly higher than the corresponding background values in the three functional areas. Based on the Igₑₒ, the study area had an uncontaminated to moderate pollution level, and the industrial area was slightly more polluted and posed a greater ecological risk than the urban and tourist areas. Comparatively, Pb, Zn, and Cu exhibited higher pollution levels in the three functional sites. Hotspots of PTEs were more concentrated in urban and industrial areas than in tourist areas. Furthermore, the health risk model revealed significant non-carcinogenic risks to children from As in urban, industrial, and tourist areas as the hazard quotients (1.64, 2.04, and 1.42, respectively) exceeded the threshold standard of 1.00. The carcinogenic risk via ingestion (RIᵢₙg) illustrated significant risks to children from Cr, As, and Ni because the RIᵢₙg values were considerably higher than the threshold standard (1.00E-6 to 1.00E-4) in the three functional areas. However, no cancer risk was observed from the dermal and inhalation pathways.

Communities in low-income and middle-income countries (LMIC) are disproportionally affected by industrial pollution compared to more developed nations. This study evaluates the dispersal and associated health risk of contaminant-laden soil and dust at a copper (Cu) smelter in Tsumeb, Namibia. It is Africa’s only smelter capable of treating complex Cu ores that contain high arsenic (As) contents (<1%). The analyses focused on the primary trace elements associated with ore processing at the smelter: As, Cu, and lead (Pb). Portable X-Ray fluorescence spectrometry (pXRF) of trace elements in soils (n = 83) and surface dust wipes (n = 80) showed that elemental contamination was spatially associated with proximity to smelter operations. Soil concentrations were below US EPA soil guidelines. Dust wipe values were elevated relative to sites distal from the facility and similar to those at other international smelter locations (As = 1012 μg/m² (95% CI 687–1337); Cu = 1838 μg/m² (95% CI 1191–2485); Pb = 1624 μg/m² (95% CI 862–2385)). Source apportionment for Pb contamination was assessed using Pb isotopic compositions (PbIC) of dust wipes (n = 22). These data revealed that the PbIC of 73% (n = 16/22) of these wipes corresponded to the PbIC of smelter slag and tailings, indicating contribution from industrial emissions to ongoing exposure risk. Modeling of carcinogenic risk showed that dust ingestion was the most important pathway, followed by inhalation, for both adults and children. Dermal contact to trace elements in dust was also determined to pose a carcinogenic risk for children, but not adults. Consequently, contemporary smelter operations remain an ongoing health risk to the surrounding community, in spite of recent efforts to improve emissions from the operations.

In this study, the distribution profiles, emission characteristics, and health risks associated with 43 volatile and semi-volatile organic compounds, including 15 phenols, 18 polycyclic aromatic hydrocarbons (PAHs), 6 BTEX, and 4 other compounds, were determined in the wastewater treatment plant (WWTP) of a coking factory (plant C) and the succeeding final WWTP (central WWTP). Total phenols with a concentration of 361,000 μg L⁻¹ were the predominant compounds in the influent wastewater of plant C, whereas PAHs were the major compounds in the final effluents of both coking WWTPs (84.4 μg L⁻¹ and 30.7 μg L⁻¹, respectively). The biological treatment process in plant C removed the majority of volatile organic pollutants (94.1%–99.9%). A mass balance analysis for plant C showed that biodegradation was the main removal pathway for all the target compounds (56.6%–99.9%) except BTEX, chlorinated phenols, and high molecular weight (MW) PAHs. Chlorinated phenols and high MW PAHs were mainly removed via sorption to activated sludge (51.8%–73.2% and 60.2%–75.9%, respectively). Air stripping and volatilization were the dominant mechanisms for removing the BTEX compounds (59.8%–73.8%). The total emission rates of the detected volatile pollutants from plant C and the central WWTP were 1,640 g d⁻¹ and 784 g d⁻¹, respectively. Benzene from the equalization basins of plant C and the central WWTP corresponded to the highest inhalation carcinogenic risks (1.4 × 10⁻³ and 3.2 × 10⁻⁴, respectively), which exceeded the acceptable level for human health (1 × 10⁻⁶) recommended by the United States Environmental Protection Agency. The results showed that BaP exhibited the highest inhalation non-cancer risk, with a hazard index ratio of 70 and 30 for plant C and the central WWTP, respectively. Moreover, the excess sludge generated during wastewater treatment should also be carefully handled because it adsorbed abundant PAHs and chlorinated phenols at coking plant C (58,000 μg g⁻¹ and 3,500 μg g⁻¹) and the central WWTP (622 μg g⁻¹ and 54 μg g⁻¹).

This study investigated the relationship between lead (Pb) speciation determined using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy in <10 μm particulate matter (PM₁₀) from mining/smelting impacted Australian soils (PP, BHK5, BHK6, BHK10 and BHK11) and inhalation exposure using two simulated lung fluids [Hatch’s solution, pH 7.4 and artificial lysosomal fluid (ALF), pH 4.5]. Additionally, elemental composition of Pb rich regions in PP PM₁₀ and the post-bioaccessibility assay residuals were assessed using a combination of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) to provide insights into how extraction using simulated lung fluids may influence Pb speciation in vitro. Correlation between Pb speciation (weighted %) and bioaccessibility (%) was assessed using Pearson r (α = 0.1 and 0.05). Lead concentration in PM₁₀ samples ranged from 782 mg/kg (BHK6) to 7796 mg/kg (PP). Results of EXAFS analysis revealed that PP PM₁₀ was dominated by Pb adsorbed onto clay/oxide, while the four BHK PM₁₀ samples showed variability in the weighted % of Pb adsorbed onto clay/oxide and organic matter bound Pb, Pb phosphate, anglesite and galena. When bioaccessibility was assessed using different in vitro inhalation assays, results varied between samples and between assays, Pb bioaccessibility in Hatch’s solution ranged from 24.4 to 48.4%, while in ALF, values were significantly higher (72.9–96.3%; p < 0.05). When using Hatch’s solution, bioaccessibility outcomes positively correlated to anglesite (r:0.6246, p:0.0361) and negatively correlated to Pb phosphate (r: -0.9610, p:0.0041), organic bound Pb (r: -0.7079, p: 0.0578), Pb phosphate + galena + plumbojarosite (r: -0.9350, p: 0.0099). No correlation was observed between Pb bioaccessibility (%) using Hatch’s solution and weighted % of Pb adsorbed onto clay/oxide and between bioaccessibility (%) using ALF and any Pb species. SEM and EDX analysis revealed that a layer of O–Pb–Ca–P–Si–Al–Fe formed during the in vitro extraction using Hatch’s solution.

In this study, total concentration and inhalation bioaccessibility (dissolution in simulated biological solution) of trace elements (TE) and rare earth elements (REE) were assessed in PM₁₀ from Canadian house dust samples with smoking (n = 25) and non-smoking (n = 25) status. Compared to the natural background concentrations in Canadian soils, median Zn, Pb, Cd and Cu concentrations in PM₁₀ were 10–23 fold higher, while median La, Ce and Pr concentrations were 1.6–2.4 fold higher. Mann-Whitney tests (α = 0.05) indicated no difference between the median TE concentrations based on the smoking status of the household; however, median REE concentrations were significantly higher in the PM₁₀ of smoking households. Additionally, Cd and Ni were positively correlated (Spearman r, p < 0.05) to La, Ce and Nd in smoking households, suggesting that tobacco combustion may have contributed REE in the PM₁₀ of these households. Median inhalation-ingestion bioaccessibility assay outcomes of arsenic (As) and lead (Pb) was higher in the non-smoking households when compared to smoking households (Mann Whitney test, α = 0.05), suggesting that tobacco combustion products may be associated with less soluble species of As and Pb. Although REE bioaccessibility was negligible in simulated lung epithelial fluid regardless of the smoking status of the household, bioaccessibility in the lung-gastric phase was 23.6–27.6% in the smoking household and 34.7–36.7% in the non-smoking households, indicating a significantly lower REE dissolution in PM₁₀ of smoking households. In contrast, between 17 and 21.9% bioaccessibility of REE was observed when artificial lysosomal fluid was used, where the outcome was not significantly affected by the smoking status. This study indicates that despite a higher median REE concentration in the PM₁₀ of smoking households, inhalation bioaccessibility may be significantly influenced by the mineralogy.

Particle-bound pollutants can pose a health risk to humans. Inhalation exposure evaluated by total contaminant concentrations significantly overestimates the potential risk. To assess the risk more accurately, bioavailability, which is the fraction that enters into the systemic circulation, should be considered. Researchers have replaced bioavailability by bioaccessibility due to the rapid and cost-efficient measurement for the latter, especially for assessment by oral ingestion. However, contaminants in particulates have different behavior when inhaled than when orally ingested. Some of the contaminants are exhaled along with exhalation, and others are deposited in the lung with the particulates. In addition, a fraction of the contaminants is released into the lung fluid and absorbed by the lung, and another fraction enters systemic circulation under the action of cell phagocytosis on particulates. Even if the release fraction, i.e., release bioaccessibility, is considered, the measurement faces many challenges. The present study highlights the factors influencing release bioaccessibility and the incorporation of inhalation bioaccessibility into the risk assessment of inhaled contaminants. Currently, there are three types of extraction techniques for simulated human lung fluids, including simple chemical solutions, sequential extraction techniques, and physiologically based techniques. The last technique generally uses three kinds of solution: Gamble’s solution, Hatch’s solution, and artificial lysosomal fluid, which are the most widely used physiologically based simulated human lung fluids. External factors such as simulated lung fluid composition, pH, extraction time, and sorption sinks can affect release bioaccessibility, whereas particle size and contaminant properties are important internal factors. Overall, release bioaccessibility is less used than bioaccessibility considering the deposition fraction when assessing the risk of contaminants in inhaled particulates. The release bioaccessibility measurement poses two main challenges: developing a unified, accurate, stable, simple, and systematic biologically based method, and validating the method through in-vivo assays.