Revisiting the atmospheric particles: Connecting lines and changing paradigms.

Historically, the atmospheric particles constitute the most primitive and recent class of air pollutants. The science of atmospheric particles erupted more than a century ago covering more than four decades of size, with past few years experiencing major advancements on both theoretic and data-based observational grounds. More recently, the plausible recognition between particulate matter (PM) and the diffusion of the COVID-19 pandemic has led to the accretion of interest in particle science. With motivation from diverse particle research interests, this paper is an 'old engineer's survey' beginning with the evolution of atmospheric particles and identifies along the way many of the global instances signaling the 'size concept' of PM. A theme that runs through the narrative is a 'previously known' generational evolution of particle science to the 'newly procured' portfolio of knowledge, with important gains on the application of unmet concepts and future approaches to PM exposure and epidemiological research.

Placental levels of polycyclic aromatic hydrocarbons (PAHs) and their association with birth weight of infants.

As an alarming group of pollutants, polycyclic aromatic hydrocarbons (PAHs) gather much public health concern not only because of their carcinogenic or co-carcinogenic risk but also by interfering with hormone systems or by causing oxidative damage, henceforth liable to toxic actions on reproduction. Accordingly, the present study was aimed to explore the association between in-utero exposure to PAHs by evaluating their placental levels and infant birth weight among 110 healthy and nonsmoking pregnant women. Placental tissue samples were collected instantly after delivery and were analyzed for the presence of sixteen Environmental Protection Agency (EPA) listed PAHs with the help of Gas chromatography equipped with flame ionization detector (GC-FID). Chrysene and benzo(k)fluoranthene were the predominant PAHs detected in tissue samples. To assess the source of origin of PAHs in placenta tissue samples, the ratio of low molecular weight PAHs to high molecular weight (∑LMW/∑HMW PAHs) was calculated, showing the predominance of pyrogenic sources of PAHs possibly responsible for the exposure of the studied population. Results of regression analysis demonstrated the inverse although not significant association of naphthalene (Nap), acenaphthylene (Acy), anthracene (Anth), pyrene (Pyr), benzo(b)fluoranthene (BbF), benzo(k)Fluoranthene (BkF), benzo(a)pyrene (BaP), indeno (123 cd pyrene (IcdP), dibenzo(ah)anthracene (DahA) and benzo(ghi)Perylene (BghiP) with birth weight of neonates. Additionally, the regression model lay light upon the significant association of fluoranthene (Fla) (coefficient= -1.41 gram, p < 0.05) to the depletion trend of birth weight after adjusting for potential covariates. These findings suggest the possible role of an environmental contaminants like PAHs on impairment of fetal growth.

Assessing effectiveness of air purifiers (HEPA) for controlling indoor particulate pollution.

The present study deals with an evaluation of the air purifier's effectiveness in reducing the concentration of different sized particulate matter (PM) and ions in the real-world indoor environment. Two types of air purifiers (API and APII) mainly equipped with High-Efficiency Particulate Air (HEPA) filters that differed in other specifications were employed in general indoor air and the presence of an external source (candles and incense). The gravimetric sampling of PM was carried out by SKC Cascade Impactor and further samples were analyzed for determining ions' concentration while real-time monitoring of different sized PM was done through Grimm Aerosol Spectrometer (1.109). The result showed that API reduced PM levels of different sizes ranged from 12-52% and 29-53% in general indoor air and presence of external source respectively. Concerning the APII, a higher decrease percent in PM level was explored in presence of an external source (52-68%) as compared to scenarios of general indoor air (37-64%). The concentrations of the ions were noticed to be decreased in all three size fractions but surprisingly some ions' (not specific) concentrations increased on the operation of both types of air purifiers. Overall, the study recommends the use of air purifiers with mechanical filters (HEPA) instead of those which release ions for air purification.

The incorporation of lemongrass oil into chitosan-nanocellulose composite for bioaerosol reduction in indoor air.

The bioaerosols present in indoor air play a major role in the transmission of infectious diseases to humans, therefore concern about their exposure is increased recently. In this regard, the present investigation described the preparation of lemongrass essential oil (LGEO) loaded chitosan and cellulose nanofibers composites (CH/CNF) for controlling the indoor air bioaerosol. The evaluation of the inhibitory effect of the composite system on culturable bacteria of the indoor air was done at different sites (air volume from 30 m3 to 80 m3) and in different size fractions of aerosol (<0.25 µm-2.5 µm). The composite system had high encapsulation efficiency (88-91%) and citrals content. A significant reduction in culturable bacteria of aerosol (from 6.23 log CFUm-3 to 2.33 log CFUm-3) was observed in presence of cellulose nanofibers and chitosan composites. The bacterial strains such as Staphylococcus sp., Bacillus cereus, Bacillus pseudomycoides sp., Pseudomonas otitidis, and Pseudomonas sp. Cf0-3 in bioaerosols were inhibited dominantly due to the diffusion of aroma molecules in indoor air. The results indicate that the interaction of diffused aroma molecule from the composite system with bacterial strains enhanced the production of ROS, resulting in loss of membrane integrity of bacterial cells. Among different size fractions of aerosol, the composite system was more effective in finer size fractions (<0.25 µm) of aerosol due to the interaction of smaller aroma compounds with bacterial cells. The study revealed that LGEO loaded chitosan and cellulose nanofibers composites could be a good option for controlling the culturable bacteria even in small-sized respirable bioaerosol.

Atmospheric polychlorinated biphenyls in a non-metropolitan city in northern India: Levels, seasonality and sources.

Recent studies from India reported polychlorinated biphenyls (PCBs) associated with incomplete combustion processes. In this study we have monitored atmospheric PCBs in Agra, a non-metropolitan city of northern India. During first month of summer and winter of 2017, polyurethane foam based passive air sampler (PUF-PAS) was deployed at each of 14 locations across urban, suburban and rural transects and one background site. Range of Σ25PCBs varied between 25 and 1433 pg/m3 (Avg ± Stdev: 460 ± 461) in summer and 26-205 pg/m3 (Avg ± Stdev: 106 ± 59) in winter. Mean Σ25PCBs concentration, showed an urban > suburban > rural trend in summer while, in winter a rural > urban > suburban trend was observed. PCB-52 was the dominant congener and after excluding this congener no significant difference was observed between summer and winter PCB concentrations. Using a combination of K-means cluster and principal component analysis (PCA) four major source types were identified. Open burning source accorded 80% of atmospheric PCBs, majorly indicator PCBs while the remaining 20% was contributed by atmospheric transport, petrogenic combustion and biomass burning. From the ten days back trajectory of the air mass it can be suggested that atmospheric transport from the hotspots resulted in a minor percentage of dioxin like PCBs in Agra. Maximum TEQs was accorded by PCB-77 (30%) and it is consistent with previous observations from Agra. Levels observed in the current study are well within the public health guideline based on inhalation unit risk (10 ng/m3) and United States Environmental Protection Agency's regional screening level high risk tier (4.9 ng/m3) for ambient air.

Particle size dynamics and risk implication of atmospheric aerosols in South-Asian subcontinent.

Presented here are size-resolved aerosol measurements conducted using cascade impactor set at breathing zone in indoor-outdoor residential microenvironments. PM2.5 contributed about 64-80% of PM10 in which over 29% of mass was shared by PM0.25. Total PM concentration varied from 261 ± 22 µg/m3 (indoors) to 256 ± 64 µg/m3 (outdoors) annually; whilst summer and monsoon demonstrated 1.2- and 1.9- times lower concentration than winters. The measured metals ranged between 9% (in PM2.5-10) to 18% (in PM1-2.5) of aerosol concentration; whereby crustal elements dominated coarse fractions with relatively higher proportion of toxic elements (Ba, Cd, Co, Cr, Cu, Ni) in ultrafine range. Considering lognormal particle size distribution (PSD), accumulation mode represented the main surface area during entire monitoring period (Mass Median Aerodynamic Diameter (MMAD) < 1). PSD of metal species reflected their different emission sources with respect to season integrated samples. High air exchange conditions permitted the shift of indoor PSD pattern closer to that of outdoor air while low ventilation in winters reflected modal shift of metals (Pb, Mg. K) towards larger size particles. Relative surge towards smaller diameter size of soluble metal fraction relative to the total concentration of toxic elements was noted on an annual basis with high infiltration capacity of smaller size particulates (Finf =1.36 for ultrafine particles in summers) identified through indoor-outdoor regression analysis. Principal Component Analysis identified sources such as vehicular traffic, combustion, crustal emission with activities viz. smoking and those involving use of electric appliances.

Environmental toxic metals in placenta and their effects on preterm delivery-current opinion.

Preterm birth is a significant public reproductive health concern globally; Furthermore, preterm birth has long-lasting medical and pecuniary burdens on the society. Moreover, preterm birth is well-established as the underlying cause of low birth weight in infants as well as neonatal mortality. A growing body of literature suggests that the etiology of preterm delivery in women is elusive; however, countless environmental factors are considered responsible for preterm birth. Environmental contaminants that are toxic metals such as lead, cadmium, arsenic, and mercury are familiar confounding factors for preterm birth globally. Recent studies have indicated that these toxic heavy metals induce oxidative stress in the trophoblastic placental tissue by producing reactive oxygen species that alter the mechanism of antioxidants possibly leading to preterm birth. Moreover, no obvious mechanism underlying metal-induced oxidative stress in the placenta has been identified until date. Consequently, this review offers an outline of the currently existing scientific information on the association of toxic metals and redox status of the placental tissue with preterm birth. Furthermore, this study critically recognizes the gaps related to the deleterious effect of metals on the gestation period in scientific literature.

Concentration and sources of fine particulate associated polycyclic aromatic hydrocarbons at two locations in the western coast of India.

PM2.5 particulate matter (PM) and their associated polycyclic aromatic hydrocarbons (PAHs) were studied at Urban and Sub-urban sites in the western coast of India. The concentration of PM2.5 ranged from 66.29 µg m-3 to 182.15 µg m-3, being the highest at Sub-urban site than the urban site. There were total six carcinogenic PAHs found to be dominated in particulate samples at these locations. The general trends observed for individual carcinogenic PAHs concentration at urban location was, benzo(a)pyrene (BaP)

Exposure levels and health risk assessment of ambient BTX at urban and rural environments of a terai region of northern India.

Benzene, toluene and xylene (BTX) belong to an important group of aromatic volatile organic compounds (VOCs) that are usually emitted from various sources. BTX play a vital role in the tropospheric chemistry as well as pose health hazard to human beings. Thus, an investigation of ambient benzene, toluene and xylene (BTX) was conducted at urban and rural sites of Gorakhpur for a span of one year in order to ascertain the contamination levels. The sampling of BTX was performed by using a low-flow SKC Model 220 sampling pump equipped with activated coconut shell charcoal tubes with a flow rate of 250 ml/min for 20-24 h. The analysis was in accordance with NIOSH method 1501. The efficiency of pump was checked weekly using regulated rotameters with an accuracy of ±1%. The samples were extracted with CS2 with occasional agitation and analyzed by GC-FID. The total BTX concentration ranged from 3.4 µg m-3 to 45.4 µg m-3 with mean value 30.95 µg m-3 and median 24.8 µg m-3. The mean concentration of total BTX was maximum during winter (39.3 µg m-3), followed by summer (28.4 µg m-3) and monsoon season (25.1 µg m-3). The mean concentration of BTX at urban site (11.8 µg m-3) was higher than that at rural site (8.8 µg m-3). At both the sites, T/B and X/B ratios were highest in monsoon and lowest in winters. Toluene against benzene plot shows R2 value of 0.96 and 0.49 at urban and rural sites respectively. Higher R2 value at urban site clearly indicates similar sources of emission for benzene and toluene. At both the sites, the estimated integrated lifetime cancer risk (ILTCR) for benzene exceeded the threshold value of 1E-06 whereas the individual hazard quotients (HQ) for BTX did not exceed unity at any of the sites.

Indoor-outdoor association of particulate matter and bounded elemental composition within coarse, quasi-accumulation and quasi-ultrafine ranges in residential areas of northern India.

Attempts have been made to comprehend size distribution pattern of Particulate Matter (PM) and associated elemental concentration within coarse (2.5-10µm), quasi-accumulation (q-Acc) (0.25-2.5µm) and quasi-ultrafine (q-UF) (<0.25µm) ranges at indoors and outdoors of residential homes of Agra. Overall, the average mass concentrations of PM10 and PM2.5 in indoors were found to be 263.24±59.24 and 212.01±38.06µgm-3 while in outdoors the concentrations accounted to 194.28±15.25 and 152.88±16.31µgm-3 respectively; exceeding WHO standards. In view of geographical variation, significantly higher (t=2.461; P=0.044) PM mass was found in outdoor samples of roadside location when compared to homes located far away from busy traffic; whereas indoor concentration exhibited non-significant relationship (t=1.887; P=0.095) between the two categorized homes. Findings of size partitioning trend through deployment of Sioutas Cascade Impactor evidenced presence of high proportion of PM and elemental concentrations within q-Acc and q-UF modes with their distribution pattern and probable emission sources conferred upon. Absence of modal peak in coarse range indicated predominance of anthropogenic emissions with presumed wash-out of coarse particles during frequent precipitation coincidental with sampling event. Seeming modal shifts for some elements (K, Cd, Zn) from q-Acc to q-UF were perceived during infiltration process. Presence of high traffic emission in homes near busy road stemmed the shifting of particles (Cu, K, Co, Zn) towards finer size (preferably q-UF mode) thus exposing residents to adverse health effects through their penetration (Finf=0.14) into indoor environment. Flat slopes (0.11) and poor correlation (8.4%) for metals in coarser range obtained through regression model hypothesized their high deposition velocities and low penetration efficiency. Our findings suggest enhanced resident exposure to fine particles (81%) especially q-UF range (37%) through indoor and outdoor (through infiltration) sources along with complexity of size distribution of airborne particles that prerequisites surplus consideration to achieve a healthier environment within residential area.

Association Between Placental Polycyclic Aromatic Hydrocarbons (PAHS), Oxidative Stress, and Preterm Delivery: A Case-Control Study.

Polycyclic aromatic hydrocarbons are known to disturb the antioxidant defense system, which may indirectly contribute to induction of early pregnancy in women. Therefore, the present investigation was designed to offer preliminary information about exposure to PAHs by estimating their placental levels and its association with oxidative stress as well as with preterm birth. Placenta tissue samples were drawn after delivery from 84 healthy pregnant women, recruited at a local nursing home of Agra, India, and levels of PAHs were quantified by gas chromatograph equipped with flame ionization detector. To evaluate redox status biomarkers, malondialdehyde (MDA) and glutathione (GSH) were determined in placenta tissue. Significantly elevated levels of benzo(a)pyrene and MDA while decreasing trend of GSH was found in women with preterm delivery group (study) than women with a full-term delivery group (control). Results demonstrated higher, but statistically insignificant (p > 0.05), levels of naphthalene, anthracene, fluorene, pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, indeno[1,2,3-cd]pyrene, dibenzo(ah)anthracene, and benzo(ghi)perylene in the study group than the control group. However, higher and lower molecular weight PAHs showed significant correlation for the depletion trend of GSH sights upon an example of oxidative stress mechanism. Because of limited statistical power and absence of controlled confounders, this study does not provide an ample involvement of PAHs with preterm delivery but increased MDA and decreased GSH in cases than controls gives the possible contribution of PAHs to early delivery.

Chemical characterization and health risk assessment of soil and airborne particulates metals and metalloids in populated semiarid region, Agra, India.

Rapid industrialization and urbanization have contaminated air and soil by heavy metals and metalloids from biogenic, geogenic and anthropogenic sources in many areas of the world, either directly or indirectly. A case study was conducted in three different microenvironments, i.e., residential sites, official sites and official sites; for each sites, we choose two different locations to examine the elemental concentration in fine particulate matter and soil and health risk assessment. The concentration values of heavy metals and metalloid in the air and soil in the Agra region were measured using inductively coupled plasma-atomic emission spectrophotometry. The exposure factor and health risk assessment for carcinogenic and non-carcinogenic effects due to heavy metals and metalloid contaminants have been calculated for both children and adults by following the methodology prescribed by USEPA. For the elements As, Cr, Cd, Ni and Pb selected for the carcinogenic health risk assessment, the calculated results lie above the threshold ranges. We observed the lifetime exposure to heavy metals through mainly three pathways, ingestion, inhalation and dermal contact of soil and air from that particular area. Therefore, the overall hazard quotient (HQ) values for children are more than that of adults. The assessment of health risk signifies that there were mainly three exposure pathways for people: ingested, dermal contact and inhalation. The major exposure pathway of heavy metals to both children and adults is ingestion. The values of HQ are higher than the safe level (=1), indicating a high risk exists in present condition. Meanwhile, HQs value for children is higher than that for adults, indicating that children have higher potential health risk than adults in this region.

Surface ozone scenario and air quality in the north-central part of India.

Tropospheric pollutants including surface ozone (O3), nitrogen dioxide (NO2), carbon monoxide (CO) and meteorological parameters were measured at a traffic junction (78°2' E and 27°11' N) in Agra, India from January 2012 to December 2012. Temporal analysis of pollutants suggests that annual average mixing ratios of tropospheric pollutants were: O3 - 22.97±23.36ppbV, NO2 - 19.84±16.71ppbV and CO - 0.91±0.86ppmV, with seasonal variations of O3 having maximum mixing ratio during summer season (32.41±19.31ppbV), whereas lowest was found in post-monsoon season (8.74±3.8ppbV). O3 precursors: NO2 and CO, showed inverse relationship with O3. Seasonal variation and high O3 episodes during summer are associated with meteorological parameters such as high solar radiation, atmospheric temperature and transboundary transport. The interdependence of these variables showed a link between the daytime mixing ratios of O3 with the nighttime level of NO2. The mixing ratios of CO and NO2 showed tight correlations, which confirms the influence of vehicular emissions combined with other anthropogenic activities due to office/working hours, shallowing, and widening of boundary layer. FLEXTRA backward trajectories for the O3 episode days clearly indicate the transport from the NW and W to S/SE and SW direction at Agra in different seasons.

Exposure profiles, seasonal variation and health risk assessment of BTEX in indoor air of homes at different microenvironments of a terai province of northern India.

BTEX are known for their ability to deteriorate human health. A monitoring study was conducted at Gorakhpur, for a span of one year. BTEX were sampled by drawing air through activated charcoal tubes, using a low flow SKC model 220 pump. Samples were extracted with CS2 followed by subjecting the aromatic fraction to GC-FID. The mean concentration of BTEX was highest at agricultural (54.3 µg m-3) followed by industrial (18.2 µg m-3), roadside (12.3 µg m-3) and residential site (6.1 µg m-3). Toluene levels were higher than benzene at all the sites except agricultural site, where benzene concentration exceeded toluene. Seasonal variation showed highest BTEX concentration during winters (32.56 µg m-3) followed by monsoon (19.90 µg m-3) and summers (14.44 µg m-3). At each site, BTEX levels increased with decrease in temperature. Benzene and toluene levels were plotted against indoor temperature, which revealed a significant linear correlation (p < 0.001) for each plot. BTEX concentrations were compared between different sites using Student's t and Mann Whitney U tests. Value of integrated lifetime cancer risk (ILTCR) was higher than 10-6 for benzene at all the sites, while for ethylbenzene, it was only higher at agricultural site. Cumulative hazard index (HI) was lower than 1.0 at all the sites.

Trace element concentration in fine particulate matter (PM2.5) and their bioavailability in different microenvironments in Agra, India: a case study.

Exposure to airborne particulate matter results in the deposition of millions of particle in the lung; consequently, there is need for monitoring them particularly in indoor environments. Case study was conducted in three different microenvironments, i.e., urban, rural and roadside to examine the elemental bioavailability in fine particulate matter and its potential health risk. The samples were collected on polytetrafluoroethylene filter paper with the help of fine particulate sampler during August-September, 2012. The average mass concentration of PM2.5 was 71.23 µg m(-3) (rural), 45.33 µg m(-3) (urban) and 36.71 µg m(-3) (roadside). Elements in PM2.5 were analyzed by inductively coupled plasma atomic emission spectroscopy. Percentage bioavailability was determined to know the amount of soluble fraction that is actually taken across the cell membrane through inhalation pathway. Cadmium and lead were found to have cancer risk in a risk evaluation using an Integrated Risk Information system.

Exposure profiles of mercury in human hair at a terai belt of North India.

Human hair is frequently used as a bioindicator of mercury exposure. Mercury (Hg) has for centuries been a useful metal in a variety of applications. Unfortunately, this usefulness is counterbalanced by its neurotoxicological health impact. The US Environmental Protection Agency recommends keeping the hair Hg level <1.0 µg/g. Therefore, an investigation has been performed in order to ascertain the hair Hg levels among the people living at the terai belt of North India. Hair samples were collected from 111 individuals and were placed in an identified plastic bag, stapled to prevent the shift of the hair strand. Samples were analyzed by combustion, gold amalgamation, atomic absorption spectrometry (C-GA-AAS). The mean Hg level in hair was 0.28 µg/g for the whole group ranging from 0.0012 to 1.9091 µg/g. The mean hair Hg levels were 0.16 µg/g for men and 0.12 µg/g for women, indicating that men had higher hair Hg levels than women. Total hair Hg was found to be significantly associated with age, gender and fish consumption frequency. 98 % of the total sample had hair Hg concentrations less than 1.0 µg/g, i.e, within safe dose, whereas only 2 % had Hg concentrations greater than 1.0 µg/g, thereby exceeding the safe dose.

Sources and characteristics of carbonaceous aerosols at Agra "World heritage site" and Delhi "capital city of India".

Agra, one of the oldest cities "World Heritage site", and Delhi, the capital city of India are both located in the border of Indo-Gangetic Plains (IGP) and heavily loaded with atmospheric aerosols due to tourist place, anthropogenic activities, and its topography, respectively. Therefore, there is need for monitoring of atmospheric aerosols to perceive the scenario and effects of particles over northern part of India. The present study was carried out at Agra (AGR) as well as Delhi (DEL) during winter period from November 2011 to February 2012 of fine particulate (PM2.5: d < 2.5 µm) as well as associated carbonaceous aerosols. PM2.5 was collected at both places using medium volume air sampler (offline measurement) and analyzed for organic carbon (OC) and elemental carbon (EC). Also, simultaneously, black carbon (BC) was measured (online) at DEL. The average mass concentration of PM2.5 was 165.42 ± 119.46 µg m(-3) at AGR while at DEL it was 211.67 ± 41.94 µg m(-3) which is ~27% higher at DEL than AGR whereas the BC mass concentration was 10.60 µg m(-3). The PM2.5 was substantially higher than the annual standard stipulated by central pollution control board and United States Environmental Protection Agency standards. The average concentrations of OC and EC were 69.96 ± 34.42 and 9.53 ± 7.27 µm m(-3), respectively. Total carbon (TC) was 79.01 ± 38.98 µg m(-3) at AGR, while it was 50.11 ± 11.93 (OC), 10.67 ± 3.56 µg m(-3) (EC), and 60.78 ± 14.56 µg m(-3) (TC) at DEL. The OC/EC ratio was 13.75 at (AGR) and 5.45 at (DEL). The higher OC/EC ratio at Agra indicates that the formation of secondary organic aerosol which emitted from variable primary sources. Significant correlation between PM2.5 and its carbonaceous species were observed indicating similarity in sources at both sites. The average concentrations of secondary organic carbon (SOC) and primary organic carbon (POC) at AGR were 48.16 and 26.52 µg m(-3) while at DEL it was 38.78 and 27.55 µg m(-3), respectively. In the case of POC, similar concentrations were observed at both places but in the case of SOC higher over AGR by 24 in comparison to DEL, it is due to the high concentration of OC over AGR. Secondary organic aerosol (SOA) was 42% higher at AGR than DEL which confirms the formation of secondary aerosol at AGR due to rural environment with higher concentrations of coarse mode particles. The SOA contribution in PM2.5 was also estimated and was ~32 and 12% at AGR and DEL respectively. Being high loading of fine particles along with carbonaceous aerosol, it is suggested to take necessary and immediate action in mitigation of the emission of carbonaceous aerosol in the northern part of India.

Fine particles characterization in residential homes located in different microenvironment of India.

Aerosol Spectrometer was used for monitoring the indoor and outdoor mass concentration of fine PM2.5, PM1.0, PM0.5 and PM0.25 in homes, located in urban, roadside and rural area of Agra city located in the north central part of India. For chemical characterization samples are collected with medium volume sampler on PTFE filters. The collected filters were extracted in an ultrasonic extractor for the determination of water soluble ions. Concentrations for F-, Cl-, NO3-, and SO42- were determined by ion chromatography. Na+, K+, Ca2+, Ba+, and Mg2+ determined by Atomic Absorption Spectrometer. The trends of particulate mass concentration indoors were rural>roadside>urban and for outdoors were roadside>rural>urban. PM2.5 concentration in our results exceeded WHO guidelines by 8-10 times for outdoor and by 7-9 times for the indoor environment during the collection period. Water soluble species ranged from 60% to 92% (Avg 72%, SD 13%) for PM2.5 total mass. The total sum of ionic concentrations in PM2.5 follow the same trend as that by mass concentration. The average I/O ratios are found to be higher in PM2.5 particles at rural and roadside sites indicating additional sources indoors at these sites.

Study of air-soil exchange of polycyclic aromatic hydrocarbons (PAHs) in the north-central part of India--a semi arid region.

Soil is the major environmental reservoir of organic compounds and soil-air exchange is a key process in governing the environmental fate of these compounds on a regional and global scale. Samples of air and soil were collected to study the levels of PAHs in the air and soil of the Agra region. Concentrations of PAH measured at four locations in the city of Agra, covers industrial, residential, roadside and agricultural areas. Samples were extracted with hexane by ultrasonic agitation. Extracts were then fractioned on a silica-gel column and the aromatic fraction was analysed by GC-MS. The mean concentration of the total PAH (T-PAH) in the air of Agra was 24.95, 17.95 and 14.25 ng m(-3), during winter, monsoon and summer respectively. The average concentration of T-PAH in the soil of Agra was 12.50, 8.25 and 6.44 µg g(-1) in winter, monsoon and summer seasons respectively. The aim of this study was to investigate the rate of approach to equilibrium partitioning of PAHs between air and soil compartments and to determine the direction of net flux of the studied PAH between air and soil. Calculated soil-air fugacity quotients indicate that the soil may now be a source of some lighter weight PAHs to the atmosphere, whereas it appears to be still acting as a long-term sink for the heavier weight PAHs to some extent in this region.

Characteristics of polycyclic aromatic hydrocarbons in indoor and outdoor atmosphere in the North central part of India.

Twenty-three polycyclic aromatic hydrocarbons (PAHs) were measured simultaneously in indoor and outdoor environment of ten homes at urban and roadside sites in the north central part of India during winter season (November 2006 to February 2007). The average concentration of total PAH (TPAH) was 1946.84 ng/m(3) in kitchen, 1666.78 ng/m(3) in living room and 1212.57 ng/m(3) in outdoors at urban site, whereas at roadside site it was 2824.87 ng/m(3), 2161.26 ng/m(3)(,) and 3294.28 ng/m(3) in kitchen, living room and outdoors respectively. The two, three and four ring PAHs were predominant in vapour phase, while the five, six ring PAHs were primarily associated with the particulate phase. The concentration trends of the PAHs in present study were naphthalene>2-methylnaphthalene>1-methylnaphthalene>biphenyl>acenaphthylene in indoor and outdoor environment of both the sites. The spatial trend of total PAHs concentrations in the house located at urban sites, was kitchen>living room>outdoors whereas at roadside site, the trend was outdoors>kitchen>living room. Correlation analysis has been used to identify the sources of PAHs. The correlation between CO(2) and ratio of living room/outdoors (L/O) and kitchen/outdoor (K/O) of total PAHs concentration for two sites was found to be significant.