Atmospheric Distribution of PAHs and Quinones in the Gas and PM1 Phases in the Guadalajara Metropolitan Area, Mexico: Sources and Health Risk

Gene expression profiles to clarify the effect of low-dose benzo(a)pyrene on crystalline silica induced acute lung injury in mice

Published evidences have suggested that air pollutant benzo(a)pyrene (BaP) may modify the toxicity and adverse effects produced by other toxicants. However, the precise role of short-term exposure to low-dose BaP on acute lung injury (ALI) induced by crystalline silica (CS) and the underlying mechanisms remain to be clarified. To investigate this issue, a mouse co-exposure model was established by intratracheal instillation of 2.5 mg CS and BaP alone or in combination. Our data found that CS exposure resulted in ALI as evidenced by lung histological changes, elevated lactate dehydrogenase activity, increased level of pro-inflammatory markers and enhanced oxidative damage. Although exposure to BaP alone had little effect on the pathological changes of mice lung tissues except for occasionally mild inflammation, it could aggravate the CS-induced ALI in a dose-dependent manner. Bioinformatic analysis of transcriptome sequencing suggested that the expression changes of significantly differentially expressed genes were closely related to the severity of ALI. The joined analysis of STC and WGCNA found that "NOD-like receptor signaling pathway", "toll-like receptor signaling pathway", "TNF signaling pathway", and "NF-kappa B signaling pathway" associated with immune and inflammatory response were the most prominent significant pathways. TLR2/9 and Nod2 might be the key inflammation-related genes that were differentially expressed in the combined lung toxicity induced by CS and BaP exposure. All these findings suggest that co-exposure of CS and low-dose BaP can cause more severe lung inflammation and oxidative damage in mice than exposure alone, which may be useful in the management and prevention of silicosis. The roles of TLR2/9 and Nod2 as candidate targets in the combined toxicity need further exploration.

Long-Term Analysis of Tropospheric Ozone in the Urban Area of Guadalajara, Mexico: A New Insight of an Alternative Criterion

Tropospheric ozone is an obligatorily-regulated pollutant, to ensure health protection and better air quality. Most countries have established maximum permissible limits (MPL) equal to 0.06 or 0.070 ppmv, but these could be insufficient considering the strictest MPL of the World Health Organization (WHO) guidelines. Such concentrations may still cause health damage to some groups of the population in urban areas. Additionally, the mean value is the principal statistical parameter for monitoring air pollution. This factor may be hiding critical ozone concentrations for public health. This work examines the mean and maximum ozone based on a multi-temporal analysis, to explore the use of a maximum average value as an air quality standard. The mean ozone had a remarkably stationary contrast; while, the maximum ozone emphasized a semi-permanent state of high pollution over the year. Diurnal variation highlights the differences of frequency between the mean and maximum ozone above any MPL, which is accentuated when compared with the WHO guidelines. Under the WHO-MPL, the mean ozone underestimates the highest concentrations; while the maximum ozone represents the extremely high concentrations observed over the year. Instead, the maximum average ozone becomes moderate; this preserves the proper, but conservative high concentrations, following similar temporal patterns as the mean ozone. This parameter is proposed to be adapted as an alternative statistical criterion to prevent negative effects on public health due to high and frequent ozone concentrations in subsequent years.

Phase distribution and risk assessment of PAHs in ambient air of Hamadan, Iran

In the present study, both gaseous and particulate (PM with dae <2.5 µm) phases of polycyclic aromatic hydrocarbons (PAHs) were measured in the ambient air of Hamadan city, Iran. For this reason, two low-volume samplers equipped with glass fiber filters were used for sampling of particulate phase (N = 30) and XAD-2 sorbent tubes were applied for sampling gaseous phase of PAHs (N = 30). The sampling was conducted during warm and cold seasons in 2019. The average of cold/warm season ratios for Σ₁₆PAH and PM concentrations were 1.14 and 0.62, respectively. Summed PAHs concentration were determined to be in the range 0.008-59.46 (mean: 11.61) ng/m³ and 0.05-40.83 (mean: 10.22) ng/m³ for the cold and warm seasons, respectively. A negative Pearson correlation coefficient was obtained for wind speed and relative humidity. The average Benzo (a) Pyrene equivalent carcinogenic (BaP_eq) levels in the cold season were lower than the maximum permissible risk level of 1 ng/m³ for BaP. The BaP toxicity equivalency (ΣBaP_TEQ) and BaP mutagenicity equivalency (ΣBaP_MEQ) appeared to be significantly higher in the cold season (averaging 0.35 and 1.65 ng/m³, respectively) than those in warm season. Health risk assessment was performed for children and adults based on BaP_eq, inhalation cancer risk. The diagnostic ratios of individual PAHs concentration showed that the significant sources of PAH emissions may be related to light duty vehicles (LDVs) in Hamadan. Although, some other sources such as pyrogenic source and petrol combustion were also suggested.

Pollution Sources and Carcinogenic Risk of PAHs in PM1 Particle Fraction in an Urban Area

Airborne particles are composed of inorganic species and organic compounds. PM₁ particles, with an aerodynamic diameter smaller than 1 μm, are considered to be important in the context of adverse health effects. Many compounds bound to particulate matter, such as polycyclic aromatic hydrocarbons (PAH), are suspected to be genotoxic, mutagenic, and carcinogenic. In this study, PAHs in the PM₁ particle fraction were measured for one year (1/1/2018–31/12/2018). The measuring station was located in the northern residential part of Zagreb, the Croatian capital, close to a street with modest traffic. Significant differences were found between PAH concentrations during cold (January–March, October–December) and warm (April–September) periods of the year. In general, the mass concentrations of PAHs characteristic for car exhausts (benzo(ghi)perylene (BghiP), indeno(1,2,3-cd)pyrene (IP), and benzo(b)fluoranthene (BbF)) were higher during the whole year than concentrations of fluoranthene (Flu) and pyrene (Pyr), which originated mostly from domestic heating and biomass burning. Combustion of diesel and gasoline from vehicles was found to be one of the main PAH sources. The incremental lifetime cancer risk (ILCR) was estimated for three age groups of populations and the results were much lower than the acceptable risk level (1 × 10⁻⁶). However, more than ten times higher PAH concentrations in the cold part of the year, as well as associated health risk, emphasize the need for monitoring of PAHs in PM₁. These data represent a valuable tool in future plans and actions to control PAH sources and to improve the quality of life of urban populations.

Characteristics of Polycyclic Aromatic Hydrocarbons (PAHs) and Common Air Pollutants at Wajima, a Remote Background Site in Japan

Background: Background sites are mainly affected by long-range-transported air pollutants, resulting in potential adverse effects on local atmospheric environments. A 4–5 year observational study was conducted to illustrate the air pollution profile at the Kanazawa University Wajima air monitoring station (KUWAMS), an ideal remote background site in Japan. Methods: Nine polycyclic aromatic hydrocarbons (PAHs) in the particulate phase and various air pollutants were continuously monitored for 4–5 years. Diagnostic ratios of PAHs and back-trajectory analysis were applied to trace the possible sources of the air pollutants collected at the sampling site. Results: The atmospheric concentration of PAHs in the atmosphere at the site decreased from 2014 to 2019, benefit from the predominant air pollution control policy in China and Japan. Common air pollutants including sulfur dioxide (SO₂), nitrogen oxides (NO_x), ozone, methane (CH₄), and non-methane hydrocarbon (NMHC) were detected in low concentrations from 2016 to 2019, while ozone (O₃) and particulate matter (PM_2.5, PM with a diameter less than 2.5 μm) were present in high levels that exceeded the Japanese standards. Most air pollutants peaked in spring and showed evident diurnal variations in spring and summer. Conclusions: This is the first study to clarify the atmospheric behaviors of multiple air pollutants at a background site in Japan. Significant external air pollutant impact and unneglectable air pollution were demonstrated at KUWAMS, indicating the importance of studying atmospheric pollution at remote sites.