Oxidative stress, biofilm-formation and activity responses of P. aeruginosa to microplastic-treated sediments: Effect of temperature and sediment type.

Climate change and plastic pollution are the big environmental problems that the environment and humanity have faced in the past and will face in many decades to come. Sediments are affected by many pollutants and conditions, and the behaviors of microorganisms in environment may be influenced due to changes in sediments. Therefore, the current study aimed to explore the differential effects of various microplastics and temperature on different sediments through the metabolic and oxidative responses of gram-negative Pseudomonas aeruginosa. The sediments collected from various fields including beaches, deep-sea discharge, and marine industrial areas. Each sediment was extracted and then treated with various microplastics under different temperature (-18, +4, +20 and 35 °C) for seven days. Then microplastics were removed from the suspension and microplastic-exposed sediment samples were incubated with Pseudomonas aeruginosa to test bacterial activity, biofilm, and oxidative characteristics. The results showed that both the activity and the biofilm formation of Pseudomonas aeruginosa increased with the temperature of microplastic treatment in the experimental setups at the rates between an average of 2-39 % and 5-27 %, respectively. The highest levels of bacterial activity and biofilm formation were mainly observed in the beach area (average rate +25 %) and marine industrial (average rate +19 %) sediments with microplastic contamination, respectively. Moreover, oxidative characteristics significantly linked the bacterial activities and biofilm formation. The oxidative indicators of Pseudomonas aeruginosa showed that catalase and glutathione reductase were more influenced by microplastic contamination of various sediments than superoxide dismutase activities. For instance, catalase and glutathione reductase activities were changed between -37 and +169 % and +137 to +144 %, respectively; however, the superoxide dismutase increased at a rate between +1 and + 21 %. This study confirmed that global warming as a consequence of climate change might influence the effect of microplastic on sediments regarding bacterial biochemical responses and oxidation characteristics.

Culture dependent analysis of bacterial activity, biofilm-formation and oxidative stress of seawater with the contamination of microplastics under climate change consideration.

Temperature changes due to climate change and microplastic contamination are worldwide concerns, creating various problems in the marine environment. Therefore, this study was carried out to discover the impact of different temperatures of seawater exposed to different types of plastic materials on culture dependent bacterial responses and oxidative characteristics. Seawater was exposed to microplastics obtained from various plastic materials at different temperature (-18, +4, +20, and +35 °C) for seven days. Then microplastics were removed from the suspension and microplastic-exposed seawater samples were analyzed for bacterial activity, biofilm formation and oxidative characteristics (antioxidant, catalase, glutathione, and superoxide dismutase) using Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. The results showed that the activity and biofilm formation of Pseudomonas aeruginosa and Staphylococcus aureus were affected through oxidative stress by catalase, glutathione, and superoxide dismutase due to the microplastic deformation by temperature changes. This study confirms that temperature changes as a result of climate change might influence microplastic degradation and their contamination impact in seawater in terms of bacterial metabolic and oxidation reactions.

Exposure to phagolysosomal simulated fluid altered the cytotoxicity of PET micro(nano)plastics to human lung epithelial cells.

The occurrence of micro(nano)plastics into various environmental and biological settings influences their physicochemical and toxic behavior. Simulated body fluids are appropriate media for understanding the degradation, stability, and interaction with other substances of any material in the human body. When the particles enter the human body via inhalation, which is one of the avenues for micro(nano)plastics, they first come into contact with the lung lining fluid under neutral conditions and then are phagocytosed under acidic conditions to be removed. Therefore, it is important to examine the physicochemical transformation and toxicity characteristics after interaction with phagolysosomal simulant fluid (PSF). Here, we focused on exploring how the physicochemical differences (e.g. surface chemistry, elemental distribution, and surface charge) of micro(nano)plastics under pH 4.5 phagolysosome conditions impact cytotoxicity and the oxidative characteristics of lung epithelia cells. The cytotoxicity of lung epithelia cells to those treated with PSF and non-treated micro(nano)plastics was tested by various viability indicators including cell counting kit-8 (CCK-8), MTT, and LDH. Furthermore, the cytotoxicity background was examined through the oxidative processes (e.g. reactive oxygen species, antioxidant, superoxide dismutase (SOD), catalase, and reduced glutathione). The results showed that all tested surface physicochemical characteristics were significantly influenced by the phagolysosome conditions. The staged responses were observed with the treatment duration, and significant changes were calculated in carbonyl, carbon-nitrogen, and sulfonyl groups. Moreover, the negativity of the zeta potentials declined between exposure of 2-40 h and then increased at 80 h compared to control owing to the chemical functional groups and elemental distribution of the plastic particles. The tested viability indicators showed that the micro(nano)plastics treated with PSF were cytotoxic to the lung epithelia cells compared to non-treated micro(nano)plastics, and SOD was the dominant enzyme triggering cytotoxicity due to the particle degradation and instability.

A characterization and an exposure risk assessment of microplastics in settled house floor dust in Istanbul, Turkey.

The presence of microplastics in the indoor environment presents growing environmental and human health risks because of their physicochemical and toxic characteristics. Therefore, we aimed to isolate, identify, and characterize plastic debris in settled house floor dusts. This study is a rare study which assess the risks of plastic debris in settled house dust through multiple approaches including the estimated daily intake, pollution loading index, and polymer hazard index. The results indicated that polyethylene and polypropylene were the predominate polymer type of plastic debris in settled house dust with various shapes and colors. The risk assessment results also indicated the serious impact of microplastics in terms of extremely dangerous contamination as well as the fact that they present a polymer hazard. Results indicated that humans have a higher risk of exposure to microplastics via ingestion rather than inhalation. In addition, infants had a higher risk of potential intake compared to other age groups.

Characterizing the interaction between micro(nano)plastics and simulated body fluids and their impact on human lung epithelial cells.

Micro(nano)plastics are considered an emerging threat to human health because they can interact with biological systems. In fact, these materials have already been found in the human body, such as in the lungs. However, limited data are available on the behavior of these materials under biological conditions and their impact on human cells, specifically on alveolar epithelial cells. In this study, micro(nano)plastics were exposed to various simulated biological fluids (artificial lysosomal fluids and Gamble's solution) for 2-80 h. Pristine and treated plastic particles were characterized based on their surface chemistry, zeta potentials, and elemental composition. Various toxicological endpoints (mitochondrial membrane potential, lactate dehydrogenase, protein, and antioxidant levels) were examined using A549 lung carcinoma cells. The surface characteristics of the treated micro(nano)plastics and the toxicological endpoints of A549 cells were found to be influenced by the simulated biological media, specifically with high concentrations of the treated micro(nano)plastics and increasing exposure under biological conditions. Moreover, the toxicological endpoints were strongly linked to the chemistry of plastics and included multiple processes in response to the plastics; different biological pathways were obtained in artificial lysosomal fluid and Gamble's solution.

Sorption of thiamin (vitamin B1) onto micro(nano)plastics: pH dependence and sorption models.

As the carrier of various inorganics and organics from various media, micro(nano)plastics have an impact on the environment and human health. Recently, many studies have examined the sorption of various organics including antibiotics. However, while vitamins have critical roles in the environment and microsystems from humans to plant life, the sorption of vitamins onto micro(nano)plastics are still uninvestigated. Therefore, the aim of this study was to examine the sorption of vitamin B1 onto various micro(nano)plastics from food packages under different pHs using batch technique; sorption kinetics and isotherms models were investigated as well. The results indicated that higher capacities were obtained between 360 min to 1440 min in polypropylene and polyethylene micro(nano)plastics, and similar kinetic behaviors observed in different pHs. However, the sorption responses (sorption capacity, equilibrium time) of polyethylene terephthalate and polystyrene were varied. The sorption kinetics between vitamin B1 and micro(nano)plastics showed that the pseudo-first-order model was better to fit for polyethylene terephthalate and polystyrene compared to the pseudo-second-order kinetics, however it was changed for polypropylene and polyethylene. Moreover, the obtained results suggest a complex nature of vitamin B1 sorption, including both chemical and physical sorption occur under various pHs and polymer types.

Multispectroscopic Characterization of Surface Interaction between Antibiotics and Micro(nano)-sized Plastics from Surgical Masks and Plastic Bottles.

Recent studies have shown that plastic particles can sorb antibiotics, and these sorption properties have been examined in various studies; however, the possible mechanism responsible for the interactions requires a deeper investigation in terms of further interaction with living systems. Moreover, the usage of disposable surgical masks and plastic bottles has increased the plastic pollution risk for living systems like humans. Therefore, this study aimed to examine the sorption characteristics between antibiotics (amoxicillin and spiramycin) and plastic particles from surgical masks and plastic bottles through batch sorption experiments. In the study, their surface interactions were characterized using multispectroscopic approaches including FTIR, Raman spectrometry, and SEM-EDX, and various surface indicators (e.g., surface oxidation, deformation, and biological potential) were examined. The sorption results showed that adsorption kinetics and the isotherm of amoxicillin and spiramycin on micro(nano)plastics from surgical masks and plastic bottles closely fit the pseudo-second-order kinetic model and Langmiur isotherm. These results indicated that the evidence for the antibiotic interaction with particles was changes in the surface functional group intensities and up-shifting, and this correlated with the sorption of antibiotics on micro(nano)-sized plastics. The C/N ratio of the plastic particles before and after antibiotic treatment was used as an indicator for the surface biological interaction, and the results showed that C/N ratios of surgical mask particles increased with both types of antibiotic sorption. However, the C/N of the particles from plastic bottles showed antibiotic type-dependence. The surface deformation indicators (e.g., O/C, C=O, C=C, and O-H indices) showed that the O/C ratios of micro(nano)plastics from surgical masks were higher with the amoxicillin and spiramycin sorption, and the C=O indices were positively linked with the amoxicillin sorption stages, whereas the C=C and O-H had a negative correlation with the amoxicillin sorption stages. Moreover, amoxicillin sorption influenced the O/C ratio and indices of O-H and C=C of micro(nano)plastics from plastic bottles in a limited manner. The C=O groups of the micro(nano)plastics from plastic bottles were positively influenced by the spiramycin sorption stages, whereas it was negatively linked with amoxicillin sorption stages. Overall, the findings from surface indicators indicated that the micro(nano)plastics from surgical masks can be more influenced with antibiotic sorption compared to plastic bottles.

Co-occurence of antibiotics and micro(nano)plastics: a systematic review between 2016-2021.

Pollution by plastics and antibiotics are emerging issues in the areas of the environment and human health. In recent years, several studies have documented the widespread occurrence of plastic particles in various environmental, as well as human, systems, and much research has focused on possible interactions of contaminants with microplastics. Thus, the co-occurrence of plastics and antibiotics has caused another global problem for the environment and human health. Therefore, we focused on the current knowledge in the field of the co-occurrence of plastics and antibiotics to summarize the available studies. In this review, categorization of the topics, contaminants details, such as polymer type, size and source, antibiotic type, and other experimental parameters were summarized and discussed. This study indicated that the sorption of antibiotics on plastics, antibiotic susceptibility in the presence of plastics, and antibiotic resistance gene onto plastics were the most frequently examined categories in this field. Moreover, the variability in the procedures and the processes, and the heterogeneity data of reporting between different studies on similar topic make it difficult to bring all results together and produce a comprehensive picture of the current knowledge. Therefore, it is suggested that further research should be done using this systematic study.

Interaction of nanoplastics with simulated biological fluids and their effect on the biofilm formation.

Over the last decade, it has become clear that the pollution by plastic debris presents global societal, environmental, and human health challenges. Moreover, humans are exposed to plastic particles in daily life and very limited information is available concerning human health, especially interactions with biological fluids. Therefore, the aim of this study is to investigate the interaction of plastic particles with simulated biological fluids (e.g., artificial saliva, artificial lysosomal fluid, phagolysosomal simulant fluid, and Gamble's solution) using various exposure stages (2 h to 80 h) and the effect of plastic particles on the formation of Staphylococcus aureus biofilms under simulated biological conditions. The plastic particles incubating various simulated biological fluids were characterized using surface functional groups, zeta potentials, and elemental composition. The results indicated that functional group indices (C-O, C = O, C-H, C = C, C-N, S = O, and OH) decreased compared to the control group during the incubation periods, except for the hydroxyl group index. The FTIR results showed that the hydroxyl group formed with the artificial lysosomal fluid, the phagolysosomal simulant fluid, and Gamble's solution. With the impact of the declining functional groups, the zeta potentials were more negative than in the control. Moreover, EDX results showed the release of the components in the particles with the interaction of simulated biological fluids as well as new components like P and Ca introduced to the particles. The biofilms were formed in the presence of nanoplastic particles under both controlled conditions and simulated biological conditions. The amount of biofilm formation was mainly affected by the surface characteristics under simulated biological conditions. In addition, the biofilm characteristics were influenced by the O/C and N/C ratios of the plastic particles with the impact of simulated biological fluids.

Single and combined effects of antibiotics and nanoplastics from surgical masks and plastic bottles on pathogens.

Over the last decade, pollution of plastics and antibiotics has increased in its threat to the environment and human health. However, very limited information is available concerning impact of co-presence of plastics and antibiotics on environment and human health. Moreover, the potential ingestion and inhalation of nano(micro)plastics due to the disposable materials has dramatically increased. With the outbreak and spread of the COVID-19 in the world, disposable surgical masks and plastic bottles have been widely used by the public, and their rapid use and improper dispensing can cause to increase plastic pollution risk on human. However, impacts of co-presence of nano(micro)plastics and antibiotics on pathogens have yet been demonstrated. Therefore, this study aims to investigate the impact the individual and combined influences of nano-sized plastics (surgical mask and plastic bottles) and antibiotics (amoxicillin and spiramycin) towards the main susceptible bacterium (Staphylococcus epidermidis, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa) by microbial activity, biofilm formation and their biochemical characteristics. The results showed that antimicrobial efficiencies of the tested antibiotics were reduced (approximately 10-98%) with the plastics. Moreover, the biochemical pathways of the microbial activity changed by the plastics entrance. Polymer structure and sorption play the role on the reduction in the inhibition of pathogens. In the meantime, the biofilm formation changed and characteristic of the extracellular polymeric substance with the co-presence of plastics and antibiotics mostly depended on the polymer structure, exposure time and sorption.

The association between air pollution parameters and emergency department visits and hospitalizations due to cardiovascular and respiratory diseases: a time-series analysis.

OBJECTIVE: In this study, the association between cardiovascular and respiratory Emergency Department (ED) visits and hospitalizations and Sulfur Dioxide (SO2) and particulate matter with an aerodynamic diameter ≤ 10 µm (PM10) was determined. METHODS: The records of a total of 632,223 people diagnosed with cardiovascular diseases (ICD-10 code I00-I99) and respiratory diseases (ICD-10 code J00-J99) at and over the age of 18 between 2012 and 2018 in three hospitals in Karaman in Turkey were examined in the present study. The daily 24-h averages for SO2 and PM10 concentrations were acquired in National Air Quality Monitoring. A time-series analysis with Poisson Generalized Linear Model was used. RESULTS: Among the air pollution parameters, the mean ± standard deviation of SO2 and PM10 were 16.2 ± 22.1 and 75.8 ± 48.2 µg/m3, respectively. An increase of 10 µg/m3 in SO2 was associated with a 3% [Relative Risk (RR), 95% Confidence Interval (CI): 2-4)] increase in cardiovascular ED visit and 2% (RR, 95% CI 2-3) increase in respiratory ED visit, and 1% (RR, 95% CI 1-3) increase in respiratory hospitalizations. An increase of 10 µg/m3 in PM10 was associated with a 1% (RR, 95% CI 1-2) increase in cardiovascular hospitalizations. CONCLUSIONS: Increases in SO2 are a risk factor for cardiovascular and respiratory ED visits, and respiratory hospitalizations. Increases in PM10 are a risk factor for cardiovascular hospitalizations.

Interaction of amino acids with nanoplastic traces and their effect on Staphylococcus aureus.

In this study, we reported the interaction between plastic traces and vital amino acids (L-homocysteine, L-valine, and L-lysine) in an aqueous system and characterized this interaction by Fourier transform infrared spectroscopy and Scanning electron microscopy with energy-dispersive X-ray spectroscopy studies. Bacterial activity and biofilm formation and their characteristics of non-treated and amino acid-treated plastic traces was tested against the Staphylococcus aureus bacterial pathogen. The surface results showed that the carbonyl groups and oxygen to carbon ratios were increased, and the attachment of nitrogen- and sulfur-related substances on the plastic surface occurred by the homocysteine over time. Plastic traces showed particle surface deformation using the main functional groups (e. g. alkyne-alkene, vinyl, secondary alcohols, alkane-methylene) with the increasing lysine treatment; however, decreased oxygen to carbon ratio showed particle anti-aging. The most common functional groups were primarily deformed with the longer exposure to valine. The bacterial activity results showed that the Staphylococcus aureus activities were not primarily changed by the amino acid treatment compared to the non-treated plastic traces. However, amino acid treated plastic traces induced the biofilm formation and its characteristic due to surface deformation of functional groups and alteration of new substances on plastic traces.

Degradation of subµ-sized bioplastics by clinically important bacteria under sediment and seawater conditions: Impact on the bacteria responses.

In this study, we investigated the interaction of submicron-sized bioplastics with environmentally and clinically important bacteria under seawater and sediment conditions. To examine the relationship between submicron-sized bioplastics and bacteria in seawater and sediment, we focused on the bacterial activation and their biochemical key events toward the protein, carbohydrate, lipid, and antioxidant response. In addition, culture-dependent biofilm formation on submicron-sized bioplastics and their characterization was performed. The results indicated that selected bacteria increased their viability both in seawater and sediment with the submicron-sized bioplastics in that the bioplastics decreased their mass at the level of 10-23%. However, the activation level and mechanism affected the polymer type, bacteria, and environmental media, and submicron-sized bioplastics promoted biofilm formation with enhancing basophilic characteristics of biofilms.

Microplastic Occurrences in Sediments Collected from Marmara Sea-Istanbul, Turkey.

Microplastics are persistent, synthetic polymers that have managed to spread even to the most remote places on earth. Studies reporting on the abundance of microplastics have recently increased worldwide, which has raised environmental concerns among scientific communities. Nevertheless, evidence of microplastic contamination from Turkey is limited even though the location is a critical point and the population is higher than most countries in the region. Thus, we aimed to detect microplastics in sediment samples collected from the Marmara Sea in Istanbul-Turkey. In this study, fourteen sediment samples were collected and sub-sampled, then plastic debris was extracted, quantified and characterized by the morphology and polymer structure. The result revealed that all of the samples contained microplastics, and their concentrations ranged between 0.3 and 85.6 g/kg sediment, and the most abundant plastic types were acrylonitrile butadiene styrene, ethylene vinyl acetate, and polystyrene.

Similarities and Discrepancies Between Bio-Based and Conventional Submicron-Sized Plastics: In Relation to Clinically Important Bacteria.

In recent years, many studies have reported the harmful effects of plastic debris both on the environment and on human health. Therefore, the attempt has increased for the replacement of conventional plastics with bioplastics. On the other hand, not only the studies on the effects of bioplastics and conventional plastics in the field of micro-, submicron- and nano-sized are still very limited, but also knowledge of their relationship with clinically important bacteria. In this study, the effect of two end products made from bioplastics and their equivalent end products from conventional plastics were evaluated using clinically important gram-positive and gram-negative bacteria. To evaluate the effect of the submicron-sized bioplastics and conventional plastics on the bacteria, their viability and activation and/or inhibition mechanism were performed towards the main biochemical (protein, carbohydrate, lipid and antioxidant) and physicochemical (particle size, zeta potential, chemical composition, and surface chemistry) phenomenon. This work highlights the similarities and discrepancies between bio-based and conventional submicron-sized plastics in relation to bacteria.

Biofilm Formation of Clinically Important Bacteria on Bio-Based and Conventional Micro/Submicron-Sized Plastics.

Micron/submicron-sized plastic debris in the environment is a global issue of increasing concern and may harm human health. A large number of studies have shown that plastic debris has various toxicological effects on different organisms. Thus, efforts have increased to replace conventional plastics with bioplastics. However, investigations on the relation of submicron-sized bioplastics- and conventional plastics to culture-dependent biofilm formation and their similarities and discrepancies are still very limited. For this purpose, two end products made from bioplastics and their equivalent end products from conventional plastics were used to examine the response of the biofilm formation of selected clinically important bacteria. To evaluate the similarities and differences of submicron-sized bioplastics and conventional plastics on biofilm formation, the physicochemistry (particle size, zeta potential, chemical composition, and surface chemistry) of the tested plastics was examined, as well as the characteristics of the biofilms (categorization, protein/carbohydrate).

Age-related physicochemical differences in ZnO nanoparticles in the seawater and their bacterial interaction.

To assess the fate and behavior of engineered nanoparticles in the environment, it is important to examine the physicochemical and toxicological transformation of nanoparticles as they age in seawater. In this study, we investigated how aging and seawater conditions altered the physiochemical structure of nanoparticles and affected their interactions with bacteria. For this purpose, zinc oxide nanoparticles were aged under different seawater conditions by keeping them in 1%, 10%, and 100% seawater for 1 day and 20 days. The main physicochemical parameters (surface chemistry, chemical composition, particle size, and zeta potential) and toxicity of aged nanoparticles towards gram-negative Pseudomonas aeruginosa and gram-positive Staphylococcus aureus were examined. The results indicated that aged zinc oxide nanoparticles in various concentrations of seawater changed their surface chemistry, chemical composition, particle size, and zeta potentials. Growth inhibition results were observed in that the inhibition of gram-negative (Pseudomonas aeruginosa) bacteria was higher compared with the gram-positive (Staphylococcus aureus) bacteria, and Staphylococcus aureus activated with the aged zinc oxide nanoparticles. Also, the results showed that the key biochemical factors affected by the aging and seawater concentration.

An insight into the dependency on sample preparation for (eco) toxicity assessment of TiO2 nanoparticles.

Assessing the environmental hazard of nanoparticles can be a challenging task using various testing strategies. However, to our knowledge, no information is available about the impact of the sample preparation on the toxicity and toxicity mechanism of nanoparticles. For this aim, three sample preparation methods and their available toxicity procedures were conducted to examine the (eco) toxicity of TiO2 nanoparticles using bacteria model system. To detail understanding of the effect of sample preparation, the key events on the inhibition were examined by physicochemical and antioxidant responses. The findings showed that the physicochemical and toxicological behavior of the tested TiO2 NPs varied according to the sample preparation method.

Influence of Al2O3 Nanoparticles on the Soil Elements.

The behavior of nanoparticles released to the soil has been extensively studied in recent years; however, the effects of nanoparticles on the distribution of soil elements and on sowing are still unknown. To this end, to examine the distribution of selected elements in soil, soil samples were treated weekly with 1.0 mg and 20.0 mg of Al2O3 nanoparticles for 3 weeks. Additionally, different types of plants (including taproot, fibrous root and ornamental bulbous plants) were sowed in the soil samples. After each treatment, surface soil samples were collected and digested with acid digestion. The concentrations of selected elements (Ca, Mg, Fe, Al, Cu, Co, Ni) were determined using a microwave plasma atomic emission spectrometer. Al2O3 treatment for 3 weeks, both low and high doses, had no effect on the Al content in soil samples when compared to the controls. Additionally, Al2O3 showed desorption properties on the analyte elements.

Interaction of PM2.5 airborne particulates with ZnO and TiO2 nanoparticles and their effect on bacteria.

A significant knowledge gap in nanotechnology is the absence of standardized protocols for examining and comparison the effect of metal oxide nanoparticles on different environment media. Despite the large number of studies on ecotoxicity of nanoparticles, most of them disregard the particles physicochemical transformation under real exposure conditions and interaction with different environmental components like air, soil, water, etc. While one of the main exposure ways is inhalation and/or atmosphere for human and environment, there is no investigation between airborne particulates and nanoparticles. In this study, some metal oxide nanoparticle (ZnO and TiO2) transformation and behavior in PM2.5 air particulate media were examined and evaluated by the influence on nanoparticle physicochemical properties (size, surface charge, surface functionalization) and on bacterium (Gram-positive Bacillus subtilis, Staphylococcus aureus/Gram-negative Escherichia coli, Pseudomonas aeruginosa bacteria) by testing in various concentrations of PM2.5 airborne particulate media to contribute to their environmental hazard and risk assessment in atmosphere. PM2.5 airborne particulate media affected their toxicity and physicochemical properties when compared the results obtained in controlled conditions. ZnO and TiO2 surfaces were functionalized mainly with sulfoxide groups in PM2.5 air particulates. In addition, tested particles were not observed to be toxic in controlled conditions. However, these were observed inhibition in PM2.5 airborne particulates media by the exposure concentration. These observations and dependence of the bacteria viability ratio explain the importance of particulate matter-nanoparticle interaction.