Characterization, pro-inflammatory response and cytotoxic profile of bioaerosols from urban and rural residential settings in Pune, India.

Microbiota associated with airborne particulate matter (PM) is an important indicator of indoor pollution as they can be pathogenic and cause serious health threats to the exposed occupants. Present study aimed to investigate the level of culturable microbes associated with PM and their toxicological characterization in urban and rural houses of Pune city. Highest concentration of bacterial aerosols observed to be associated with PM10 size fraction in urban site (2136 ± 285 CFU/m3) whereas maximum fungal concentration has been measured in rural houses (1521 ± 302 CFU/m3). Predominantly found bacterial species were Bacillus sp., S. aureus, and Pseudomonas aeruginosa and fungal species were Aspergillus sp., Cladosporium sp., and Penicillium sp. in both urban and rural residential premises. Concentration of endotoxin measured using the kinetic Limulus Amebocyte Lysate assay exhibited that the level of endotoxin in both urban and rural sites are associated with household characteristics and the activities performed in indoor as well as outdoor. Cell free DTT assay confirmed the ability of these airborne microbes to induce the production of reactive oxygen species (ROS) varying along with the types of microorganisms. On exposure of A549 cells to airborne microbes, a significant decrease in cell viability was observed in terms of both necrosis and apoptosis pathway. Elevated production of nitric oxide (NO) and proinflammatory cytokines in epithelial cells and macrophages clearly suggest the inflammatory nature of these airborne microbes. Results derived from the present study demonstrated that the indoor air of urban and rural houses of Pune is contaminated in terms of microbial load. Therefore, attention should be paid to control the factors favoring the microbial growth in order to safeguard the health of exposed inhabitants.

Toxicological screening of airborne particulate matter in atmosphere of Pune: Reactive oxygen species and cellular toxicity.

Present study screened the toxicological assessment of airborne particulate matter (PM), mechanistic investigation, relationship between the physicochemical characteristics and its associated toxic response. The average concentration of both PM10 and PM2.5 exceeded the Indian National Ambient Air Quality Standards. In present study, PM bound metals; Fe, Cu, Cr, Ni, Mn, Pb, Cd, Zn, Sr and Co have been taken into account with total metal concentration of 0.83 and 0.44 µg m-3 of PM10 and PM2.5 mass concentrations, respectively. The contribution of redox active metals (Fe, Cu, Cr, Ni and Mn) in PM was more as compared to non-redox metals (Pb, Cd and Co) indicating significant risk to the exposed population as these metals possess the ability to produce reactive oxygen species (ROS) which are responsible for various diseases. The cytotoxicity profiles of PM samples determined by MTT assay on two different cell lines (A549 and PBMC) exhibited dose-dependent effects after 24 h exposure, but the consequences differ with respect to particle size and sampling periods. A significant decrease in cell viability with varying PM concentrations (20, 40, 60, 80 and 100 µg ml-1) with respect to control was found in both cell lines. Incubation of RBC suspension with PM samples caused pronounced disruption of RBC and thus exhibited substantial hemolytic behavior. PM samples showed a range of potency to produce reactive oxygen species (ROS). Almost all PM samples increased the level of pro-inflammatory mediator (Nitric oxide) when compared to corresponding unexposed controls suggesting the important role of reactive nitrogen species in induction of cellular toxicity.

Genotoxic effects of PM10 and PM2.5 bound metals: metal bioaccessibility, free radical generation, and role of iron.

The present study was undertaken to examine the possible genotoxicity of ambient particulate matter (PM10 and PM2.5) in Pune city. In both size fractions of PM, Fe was found to be the dominant metal by concentration, contributing 22% and 30% to the total mass of metals in PM10 and PM2.5, respectively. The speciation of soluble Fe in PM10 and PM2.5 was investigated. The average fraction of Fe3+ and Fe2+ concentrations in PM2.5 was 80.6% and 19.3%, respectively, while in PM2.5 this fraction was 71.1% and 29.9%, respectively. The dominance of Fe(III) state in both PM fractions facilitates the generation of hydroxyl radicals (·OH), which can damage deoxyribose nucleic acid (DNA), as was evident from the gel electrophoresis study. The DNA damage by ·OH was supported through the in silico density functional theory (DFT) method. DFT results showed that C8 site of guanine (G)/adenine (A) and C6 site of thymine (T)/cytosine (C) would be energetically more favorable for the attack of hydroxyl radicals, when compared with the C4 and C5 sites. The non-standard Watson-Crick base pairing models of oxidative products of G, A, T and C yield lower-energy conformations than canonical dA:dT and dG:dC base pairing. This study may pave the way to understand the structural consequences of base-mediated oxidative lesions in DNA and its role in human diseases.

Chemical fractionation and health risk assessment of particulate matter-bound metals in Pune, India.

The present study deals with the assessment of sequential extraction of particulate matter (PM)-bound metals and the potential health risks associated with them in a growing metropolitan city (Pune) of India. The average mass concentration of both PM2.5-10 and PM2.5 exceeded the National Ambient Air Quality Standards. Significant seasonal variation in mass concentration was found for both size fractions of PM with higher values in winter season and lower in monsoon. Chemical species of the studied trace metals in PM exhibited significant differences, due to difference in sources of pollution. Metals such as Cd, Pb, and Cr in both size fractions and Zn and Co in fine fraction were more efficiently extracted in mobile fractions showing their mobile nature while Ni and Fe showed reduced mobility. Fe showed the highest concentrations among all the analyzed elements in both coarse (PM2.5-10) and fine (PM2.5) PM, while Cd showed least concentration in both size fractions. PCA identified industrial emissions, vehicular activity, coal combustion, diesel exhaust, waste incineration, electronic waste processing, constructional activities, soil, and road dust as probable contributors responsible for the metallic fraction of PM. All the metals showed varying contamination in PM samples. The contamination was higher for fine particles than coarse ones. The average global contamination factor was found to be 27.0-34.3 in coarse and fine PM, respectively. The hazard quotient (HQ) estimated for Cd, Co, and Ni (both total and easily accessible concentrations) exceeded the safe level (HQ = 1), indicating that these metals would result in non-carcinogenic health effects to the exposed population. The HQ ranged from 9.1 × 10-5 for Cu (coarse) to 8.3 for Ni (fine) PM. The cancer risk for Cd, Ni, and Cr in both sized PM were much higher than the acceptable limits of USEPA.

Role of metals in free radical generation and genotoxicity induced by airborne particulate matter (PM2.5) from Pune (India).

In the present study, metal-facilitated free radical generation in particulate matter (PM) and its association with deoxyribonucleic acid (DNA) damage were studied. The examined data showed that the concentration of fine PM in Pune exhibited seasonal variations. Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to examine the metal composition, which showed the presence of metals such as Cu, Zn, Mn, Fe, Co, Cr, Pb, Cd, and Ni. Fe metal was present in the highest concentrations in both the seasons, followed by Zn. The scanning electron microscopy-energy-dispersive spectrometer (SEM-EDS) results also demonstrated that the fine PM particles deposited in summer samples were less than those of winter samples, suggesting that the PM load in winter was higher as compared to that in summer. Elemental mapping of these particles substantiates deposition of metals as Fe, Zn, etc. on particles. The electron paramagnetic species (EPR) technique was utilized for free radical detection, and plasmid DNA assay was utilized to study the genotoxicity of ambient fine PM. Obtained g values show the presence of radicals in PM samples of Pune. PM contains the C-centered radical with a vicinal oxygen atom (g = 2.003). In addition to this, the g value for Fe was also observed. Therefore, we intend that the radicals related with fine PM comprise metal-mediated radicals and produce DNA damage. The plasmid DNA assay results indicated that the TM50 values (toxic mass of PM causing 50 % of plasmid DNA damage) of PM exhibited seasonal variations with higher TM50 values for summer and lower TM50 values during winter.