Concentrations of polycyclic aromatic hydrocarbons in resuspendable fraction of settled bus dust and its implications for human exposure

Impact of Skin Exposure to Benzo[a]pyrene in Rat Model: Insights into Epidermal Cell Function and Draining Lymph Node Cell Response

The skin is a direct target of the air pollutant benzo[a]pyrene (BaP). While its carcinogenic qualities are well-studied, the immunotoxicity of BaP after dermal exposure is less understood. This study examines the immunomodulatory effects of a 10-day epicutaneous BaP application, in environmentally/occupationally relevant doses, by analyzing ex vivo skin immune response (skin explant, epidermal cells and draining lymph node/DLN cell activity), alongside the skin's reaction to sensitization with experimental hapten dinitrochlorobenzene (DNCB). The results show that BaP application disrupts the structure of the epidermal layer and promotes immune cell infiltration in the dermis. BaP exposure led to oxidative stress in epidermal cells, characterized by decreased reduced glutathione and increased AHR and Cyp1A1 expression. Production and gene expression of proinflammatory cytokines (TNF, IL-1β) by epidermal cells decreased, while IL-10 response increased. Decreased spontaneous production of IFN-γ and IL-17, along with unchanged IL-10, was observed in DLC cells, whereas ConA-stimulated production of these cytokines was elevated. Local immunosuppression caused by BaP application seems to reduce the skin's response to an additional stimulus, evidenced by decreased effector activity of DLN cells three days after sensitization with DNCB. These findings provide new insight into the immunomodulatory effects and health risks associated with skin exposure to BaP.

Reduced commuter exposure to PM2.5 and PAHs in response to improved emission standards in bus rapid transit systems in Mexico

We evaluated impacts of progressive technological updates to bus rapid transit (BRT) systems on in-cabin concentrations of particulate matter with an aerodynamic diameter ≤2.5 μm (PM2.5), and the various polyaromatic hydrocarbons (PAHs) to which commuters were exposed. PM2.5 samples were collected and real-time concentrations measured from October 2017 to March 2020 inside cabins of BRT buses equipped with Euro IV, V and VI diesel emission standards in the Mexico City Metropolitan Area (MCMA). For effective comparison, similar samplings and measurements were carried out on trains in the MCMA underground (MCU) system. Peak in-cabin PM2.5 concentrations decreased significantly (p < 0.05) by 35% from Euro IV to Euro V buses, and by 80% from Euro IV to Euro VI buses. PM2.5 concentrations inside Euro VI buses were significantly lower (p < 0.05) than in Euro IV and Euro V buses and in underground trains. The in-cabin excess (ICE) of PM2.5 relative to ambient concentrations was significantly (p < 0.05) higher for Euro IV than for Euro V buses during morning the traffic peak, and consistently higher than for Euro VI buses. Indeed, ICEs calculated for Euro VI buses were always lower than those for electricity-powered underground trains. The frequency of hotspots decreased from Euro IV to Euro VI buses due to the combined effect of low emissions and closed, air-conditioned cabins. Concentrations of total PAHs including carcinogenic species also decreased from Euro IV to Euro V buses and were below limits of detection aboard Euro VI buses. This work shows that in real-life conditions, advanced diesel technologies and cabin design significantly reduce commuters' exposure to PM2.5 and to toxic PAH compounds.

Emission profiles, source identifications, and health risk of polycyclic aromatic hydrocarbons (PAHs) in a road tunnel located in Xi'an, China

Understanding the sources and characteristics of PM2.5-bound PAHs from traffic-related pollution can provide valuable data for mitigating air contamination from traffic in local urban regions. However, little information on PAHs is available regarding the typical arterial highway-Qinling Mountains No.1 tunnel in Xi'an. We estimated the profiles, sources, and emission factors of PM2.5-bound PAHs in this tunnel. The total PAH concentrations were 22.78 ng·m-3 and 52.80 ng·m-3 at the tunnel middle and exit, which were 1.09 and 3.84 times higher than that at the tunnel entrance. Pyr, Flt, Phe, Chr, BaP, and BbF were the dominant PAH species (representing approximately 78.01% of total PAHs). The four rings PAHs were dominant (58%) among the total PAH concentrations in PM2.5. The results demonstrated that diesel and gasoline vehicles exhaust emissions contributed 56.81% and 22.60% to the PAHs, respectively, while the corresponding value for together brakes, tyre wear, and road dust was 20.59%. The emission factors of total PAHs were 29.35 μg·veh-1·km-1, and emission factors of 4 rings PAHs were significantly higher than those of the other PAHs. The sum of ILCR was estimated to be 1.41×10-4, which accorded with acceptable level of cancer risk (10-6-10-4), PAHs should not ignored as they still affect the public health of inhabitants. This study shed light on PAH profiles and traffic-related sources in the tunnel, thereby facilitating the assessment of control measures targeting PAHs in local areas.

Distribution and Relationships of Polycyclic Aromatic Hydrocarbons (PAHs) in Soils and Plants near Major Lakes in Eastern China

The distributions and correlations among polycyclic aromatic hydrocarbons (PAHs) in soils and plants were analyzed. In this study, 9 soil samples and 44 plant samples were collected near major lakes (Hongze Lake, Luoma Lake, Chaohu, Changhu, Danjiangkou Reservoir, Wuhan East Lake, Longgan Lake, Qiandao Lake and Liangzi Lake) in eastern China. The following results were obtained: The total contents of PAHs in soil varied from 99.17 to 552.10 ng/g with an average of 190.35 ng/g, and the total contents of PAHs in plants varied from 122.93 to 743.44 ng/g, with an average of 274.66 ng/g. The PAHs in soil were dominated by medium- and low-molecular-weight PAHs, while the PAHs in plants were dominated by low-molecular-weight PAHs. The proportion of high-molecular-weight PAHs was the lowest in both soil and plants. Diagnostic ratios and principal component analysis (PCA) identified combustion as the main source of PAHs in soil and plants. The plant PAH monomer content was negatively correlated with Koa. Acenaphthylene, anthracene, benzo[k]fluoranthene, benzo[b]fluoranthene and dibenzo[a,h]anthracene were significantly correlated in plants and soil. In addition, no significant correlation between the total contents of the 16 PAHs and the content of high-, medium-, and low-molecular-weight PAHs in plants and soil was found. Bidens pilosa L. and Gaillardia pulchella Foug in the Compositae family and cron in the Poaceae family showed relatively stronger accumulation of PAHs, indicating their potential for phytoremediation.

Distribution and source of and health risks associated with polybrominated diphenyl ethers in dust generated by public transportation

Carcinogenic and neurotoxic polybrominated diphenyl ethers (PBDEs) are environmentally ubiquitous and have been widely investigated. However, little is understood regarding their pollution status, sources, and potential risk to persons in public transportation microenvironments (PTMs). We collected 60 dust samples from PTMs and then selected four materials typical of bus interiors to determine the sources of PBDEs in dust using principal component analysis coupled with Mantel tests. We then evaluated the risk of PBDEs to public health using Monte Carlo simulations. We found that PBDE concentrations in dust were 2-fold higher in buses than at bus stops and that brominated diphenyl ether (BDE)-209 was the main pollutant. The number of buses that passed through a bust stop contributed to the extent of PBDE pollution, and the primary potential sources of PBDEs in dust were plastic handles and curtains inside buses; BDE-209 and BDE-154 were the main contributors of pollution. We found that health risk was 8-fold higher in toddlers than in adults and that the reference doses of PBDEs in dust were far below the United States Environmental Protection Agency limits. Our findings provide a scientific basis that may aid in preventing PBDE pollution and guiding related pollution management strategies in PTMs.

The partitioning behavior of PAHs between settled dust and its extracted water phase: Coefficients and effects of the fluorescent organic matter

The occurrence and distribution of polycyclic aromatic hydrocarbons (PAHs) in a city of Central China were determined in the settled dust and its extracted water phase from different land use types and bus stops in Nanchang City. The physicochemical properties of its water extracted dissolved organic matter (WEOM) were characterized to investigate the effect of fluorescence organic matter on the dust-water partitioning coefficients (K_d) using three-dimensional excitation-emission matrix fluorescence spectroscopy combined parallel factor analysis. Results showed that the range of ∑PAHs in settled dust and the extracted water phase was 0.05-15.92 μg·g^-1 and 2-211 ng·L^-1, respectively. These PAHs mostly came from the combustion of biomass. The risk assessment showed that PAHs in dust had no obvious health risk (less than the magnitude of 10^-6). Additionally, the high molecular weight (HMW) PAHs and the low molecular weight (LMW) PAHs were preferentially adsorbed by dust and the dissolved portion, respectively. It was confirmed by the relatively high logK_d values of 4.23 for the HMW-PAHs. Pearson correlation analysis suggested that the higher concentration of dissolved organic carbon and humic-like substance were in favor of PAHs in dust released into waters. This study can provide information on pollution control when considering the impact of fluorescent organic matter on the fate and transport of PAHs.

Polycyclic Aromatic Hydrocarbons (PAHs) in Indoor Dust Across China: Occurrence, Sources and Cancer Risk Assessment

In this study, the occurrence of 16 polycyclic aromatic hydrocarbons (PAHs) was investigated in 31 household dusts that were sampled from 27 areas located in 10 provinces, China. The total concentrations of PAHs (∑ PAHs) were in the range of 613-10,111 ng·g^-1 with a median of 2565 ng·g^-1. The predominant PAHs were 2 to 3 ringed compounds, accounting for 85.3% of ∑ PAHs. The geographical location had little impact on the contents of PAHs. Higher concentrations of ∑ PAHs and individual homologues of PAHs except for naphthalene (NAP) were observed in rural areas, which is related to the higher usage of coal or biomass for cooking. Cooking method played a major role in contributing to the concentrations of PAHs. Both household cooking and petrogenic sources from outdoors were the primary sources of PAHs in household dust. Cancer risk assessment indicated that dermal contact and ingestion are the main exposure pathways to indoor residents. Furthermore, the average values of sum of incremental lifetime cancer risks (ILCRs) were 2.22 × 10^-7 for adults and 2.51 × 10^-7 for children, suggesting that there is a low health risk posed by PAHs in indoor dust. The contribution percentage of 4 to 6 rings PAHs to ILCRs was up to 96.3%, indicating that higher molecular weight PAHs in indoor dust, especially benzo[a]pyrene (BaP) and dibenzo[a,h]anthracene (DahA), are major factors contributing to cancer risk.

Chemoresistance to Cancer Treatment: Benzo-α-Pyrene as Friend or Foe?

Background: Environmental pollution such as exposure to pro-carcinogens including benzo-α-pyrene is becoming a major problem globally. Moreover, the effects of benzo-α-pyrene (BaP) on drug pharmacokinetics, pharmacodynamics, and drug resistance warrant further investigation, especially in cancer outpatient chemotherapy where exposure to environmental pollutants might occur. Method: We report here on the effects of benzo-α-pyrene on esophageal cancer cells in vitro, alone, or in combination with chemotherapeutic drugs cisplatin, 5-flurouracil, or paclitaxel. As the study endpoints, we employed expression of proteins involved in cell proliferation, drug metabolism, apoptosis, cell cycle analysis, colony formation, migration, and signaling cascades in the WHCO1 esophageal cancer cell line after 24 h of treatment. Results: Benzo-α-pyrene had no significant effect on WHCO1 cancer cell proliferation but reversed the effect of chemotherapeutic drugs by reducing drug-induced cell death and apoptosis by 30−40% compared to drug-treated cells. The three drugs significantly reduced WHCO1 cell migration by 40−50% compared to control and BaP-treated cells. Combined exposure to drugs was associated with significantly increased apoptosis and reduced colony formation. Evaluation of survival signaling cascades showed that although the MEK-ERK and Akt pathways were activated in the presence of drugs, BaP was a stronger activator of the MEK-ERK and Akt pathways than the drugs. Conclusion: The present study suggest that BaP can reverse the effects of drugs on cancer cells via the activation of survival signaling pathways and upregulation of anti-apoptotic proteins such as Bcl-2 and Bcl-xL. Our data show that BaP contribute to the development of chemoresistant cancer cells.

Molecular mechanisms of dust-induced toxicity in human corneal epithelial cells: Water and organic extract of office and house dust

Human corneal epithelial (HCE) cells are continually exposed to dust in the air, which may cause corneal epithelium damage. Both water and organic soluble contaminants in dust may contribute to cytotoxicity in HCE cells, however, the associated toxicity mechanisms are not fully elucidated. In this study, indoor dust from residential houses and commercial offices in Nanjing, China was collected and the effects of organic and water soluble fraction of dust on primary HCE cells were examined. The concentrations of heavy metals in the dust and dust extracts were determined by ICP-MS and PAHs by GC-MS, with office dust having greater concentrations of heavy metals and PAHs than house dust. Based on LC50, organic extract was more toxic than water extract, and office dust was more toxic than house dust. Accordingly, the organic extracts induced more ROS, malondialdehyde, and 8-Hydroxydeoxyguanosine and higher expression of inflammatory mediators (IL-1β, IL-6, and IL-8), and AhR inducible genes (CYP1A1, and CYP1B1) than water extracts (p<0.05). Extracts of office dust presented greater suppression of superoxide dismutase and catalase activity than those of house dust. In addition, exposure to dust extracts activated NF-κB signal pathway except water extract of house dust. The results suggested that both water and organic soluble fractions of dust caused cytotoxicity, oxidative damage, inflammatory response, and activation of AhR inducible genes, with organic extracts having higher potential to induce adverse effects on primary HCE cells. The results based on primary HCE cells demonstrated the importance of reducing contaminants in indoor dust to reduce their adverse impacts on human eyes.

Bioremediation strategies of hydrocarbons and microbial diversity in the Trindade Island shoreline--Brazil

This study analyzed the microbial diversity colonizing the surface of an oil sample during its contact with water, off the Trindade Island coast and simulated the efficiency of eight different bioremediation strategies for this environment. The diversity analysis was performed using acrylic coupons that served as the support for an oil inclusion at sea. The coupons were sampled over 30 days, and T-RFLP multiplex was employed to access the diversity of fungi, Bacteria and Archaea present on the oil surface. The bioremediation strategies were simulated in a respirometer. The results showed that the bacterial domain was the most dominant in oil colonization and that the richness of the species attached to the oil gradually increases with the exposure time of the coupons. The combination of biostimulation and bioaugmentation with a native population was proven to be an effective strategy for the remediation of oil off the Trindade Island shoreline.