Assessment of air quality after the implementation of compressed natural gas (CNG) as fuel in public transport in Delhi, India

Comparison of tailpipe carbonyls and volatile organic compounds emissions from in-use gasoline/CNG bi-fuel vehicles

Ground-level ozone contamination has been globally an urban air quality issue, particularly for China, which has recently made significant progress in purifying its sky. Unregulated exhaust emissions from motor vehicles, predominantly carbonyls and volatile organic compounds (VOCs), are among the leading contributors to ozone formation. In this chassis-level study, the unregulated emissions from five China-5 certified gasoline/CNG bi-fuel taxis, along with their ozone forming potential (OFP), were evaluated. It is found that carbonyls and VOCs were mainly emitted during the starting phase no matter the engine was cold or hot. Compared to gasoline, CNG fueling reduced VOCs emissions on a large scale, especially in the starting phase, but had elevated carbonyls. On a fleet average, CNG fueling derived 15% and 46% less OFP than gasoline in cold- and hot-start tests, respectively. VOCs contributed to over 90% of the total OFP of the exhaust. In terms of alleviating ground-level ozone contamination, CNG is a feasible alternative to gasoline on light-duty vehicles.

Distribution, composition and risk assessment of hydrocarbon residue in surficial sediments of El-Dakhla, El-Kharga and El-Farafra oases, Egypt

This work examined the polycyclic aromatic hydrocarbons (PAHs) and n-alkanes quantities, sources, and hazards in sediments collected from the Egyptian Western Desert Oases namely: Dakhla, Kharga and Farafra oases. The n-alkane (C9-C20) residue concentrations have ranged from 0.66 to 2417.91 µg/g recorded for the three Oases. On the other hand, the total n-alkane ranged from 448.54 µg/g to 8442.60 µg/g. Higher carbon preference index (CPI) values (> 1.0) proposed that the natural sources could be the main contributor to n-alkanes in the Oases sediment. GC-MS/MS (selected reaction monitoring (SRM) method) was used for the determination of the ΣPAHs concentrations in the studied sediments. The ΣPAHs concentrations (ng/g, dry weight) in the studied three Oases varied from 10.18 to 790.14, 10.55 to 667.72, and from 38.27 to 362.77 for the Kharga, Dakhla and Farafra Oases, respectively. The higher molecular weight PAHs were the most abundant compounds in the collected samples. Assessing potential ecological and human health issues highlighted serious dangers for living things and people. All the investigated PAHs had cancer risk values between 1.43 × 10-4 and 1.64 × 10-1, this finding suggests that PAHs in the samples under study pose a moderate risk of cancer. The main sources of PAHs in this study are biomass, natural gas, and gasoline/diesel burning emissions.

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.

Profile of atmospheric particulate PAHs near busy roadway in tropical megacity, India

Objective: This study focuses on the profile of ambient particulate polycyclic aromatic hydrocarbons (PAHs), their seasonal distribution, source identification and human health risk assessment due to inhalation exposure of ambient PAHs in Delhi, India.Materials and Methods: Two sampling sites were chosen, one at roadway (MH) and other at urban background (JNU) site in Delhi. Determination of PAHs was carried with the help of HPLC with UV detector. Principal component analysis and Molecular diagnostic ratios were used for the source apportionment of PAHs. Health risks associated with inhalation of particulate PAHs were assessed using benzo(a)pyrene equivalent concentration and incremental lifetime cancer risk (ILCR) approach.Results: The results showed that the average mass concentration of Σ₁₆ PAHs near roadway (67.8 ± 40.2 ng m^-3) is significantly higher than urban background site (56 ± 30 ng m^-3). Moreover, source apportionment study indicated that major PAH-emission sources in Delhi NCR are traffic and coal combustion. ILCR values at both the sites fall in the range of 10^-2-10^-4 that corresponds to the priority risk level (10^-3) and higher than the acceptable risk level (10^-6).conclusions: The high PAHs concentration at MH site was due to it's nearness to busy traffic area. Thus, the spatial variations in PAHs were influenced by local emission sources. The high PAHs level during the winter season can be due to their higher emissions from local heating sources, shift of gas/particle partitioning toward the particulate phase at low temperature and reduced photochemical degradation of some PAHs in winter. The low level of PAHs in monsoon season can be attributed to their wet scavenging and higher percentage in vapor phase. PCA showed that the emissions from vehicles predominate at MH site; whereas, coal combustion and traffic both are the significant PAHs sources at JNU site. Health risk assessment revealed that the highest exposure risks occur at busy traffic site, thereby indicating a significantly higher health risk to the population of Delhi.

Impact of COVID-19 induced lockdown and unlock down phases on the ambient air quality of Delhi, capital city of India

The present study deals with the impact of the pandemic outbreak of COVID-19 on the ambient air quality in the capital city of India. Real-time data were collected from eight continuous ambient air quality monitoring stations measuring important air quality parameters (NO₂, PM₁₀ and PM_2.5). Results revealed that the city's air quality had improved significantly during the lockdown period due to COVID-19 outbreak. The concentration of gaseous and particulate matter during the lockdown period (March-May 2020) declined significantly compared with the preceding years' data from the same timeframe. However, the ambient air quality deteriorates with the onset of unlocking phases and post-monsoon season (October 2020). Higher concentration of NO₂, PM₁₀ and PM_2.5 were recorded at industrial (S1 and S2) and hotspot (S4 and S5) sites. The lowest concentrations of studied pollutants were observed during the first phase of lockdown (March 24 - May 14, 2020). The present study, once again, establishes the direct effect of anthropogenic activities and deteriorating ambient air quality of Delhi.

Impact of COVID-19 lockdown on ambient air quality in megacities of India and implication for air pollution control strategies

The impact of restrictions during various phases of COVID-19 lockdown on daily mean PM_2.5 concentration in five Indian megacities (New Delhi, Chennai, Kolkata, Mumbai, and Hyderabad) was studied. The impact was studied for pre-lockdown (1st Mar-24th Mar 2020), lockdown (25th Mar-31st May 2020), and unlocking (1st Jun-31st Aug 2020) phases. The lockdown period comprises 4 lockdown phases with distinct measures, whereas the unlocking period had 3 phases. PM_2.5 concentration reduced significantly in all megacities and met the national standards during the lockdown period. The maximum reduction in PM_2.5 level was observed in Kolkata (62%), followed by Mumbai (49%), Chennai (34%), and New Delhi (26%) during the lockdown period. Comparatively, Hyderabad exhibited a smaller reduction in PM_2.5 concentration, i.e., 10%. The average PM_2.5 levels during the lockdown in the peak hour (i.e., 07:00-11:00 h) in New Delhi, Chennai, Kolkata, Mumbai, and Hyderabad decreased by 21.3%, 48.5%, 63.4%, 56.4%, and 23.8%, respectively, compared to those before lockdown period. During the unlocking period, except for Chennai, all megacities showed a reduction in average PM_2.5 levels compared to concentrations in the lockdown period, but these reductions were mainly linked with monsoon rains in India. The current study provided an opportunity to study air pollution in the absence of major anthropogenic activities and during limited activities in monsoon season having an ecological design. The study reports a new baseline of PM_2.5, except for monsoon, and explores this knowledge to plan future air pollution reduction strategies. The study also discusses how this new learning of knowledge could strengthen air pollution control policies for better air quality and sustainability.Graphical abstract.

Chemical characterization of PM2.5 and source apportionment of organic aerosol in New Delhi, India

Delhi is one of the most polluted cities worldwide and a comprehensive understanding and deeper insight into the air pollution and its sources is of high importance. We report 5 months of highly time-resolved measurements of non-refractory PM_2.5 and black carbon (BC). Additionally, source apportionment based on positive matrix factorization (PMF) of the organic aerosol (OA) fraction is presented. The highest pollution levels are observed during winter in December/January. During that time, also uniquely high chloride concentrations are measured, which are sometimes even the most dominant NR-species in the morning hours. With increasing temperature, the total PM_2.5 concentration decreases steadily, whereas the chloride concentrations decrease sharply. The concentrations measured in May are roughly 6 times lower than in December/January. PMF analysis resolves two primary factors, namely hydrocarbon-like (traffic-related) OA (HOA) and solid fuel combustion OA (SFC-OA), and one or two secondary factors depending on the season. The uncertainties of the PMF analysis are assessed by combining the random a-value approach and the bootstrap resampling technique of the PMF input. The uncertainties for the resolved factors range from ±18% to ±19% for HOA, ±7% to ±19% for SFC-OA and ±6 % to ±11% for the OOAs. The average correlation of HOA with equivalent black carbon from traffic (eBC_tr) is R² = 0.40, while SFC-OA has a correlation of R² = 0.78 with equivalent black carbon from solid fuel combustion (eBC_sf). Anthracene (m/z 178) and pyrene (m/z 202) (PAHs) are mostly explained by SFC-OA and follow its diurnal trend (R² = 0.98 and R² = 0.97). The secondary oxygenated aerosols are dominant during daytime. The average contribution during the afternoon hours (1 pm-5 pm) is 59% to the total OA mass, with contributions up to 96% in May. In contrast, the primary sources are more important during nighttime: the mean nightly contribution (22 pm-3 am) to the total OA mass is 48%, with contributions up to 88% during some episodes in April.

Air pollution trend in Chandigarh city situated in Indo-Gangetic Plains: Understanding seasonality and impact of mitigation strategies

The long-term trend of air pollutants was studied in Chandigarh, located in Indo-Gangetic Plains of India. The SPM, PM₁₀, NO_x, and SO₂ depict site-specific variation having different anthropogenic activities. The results indicate that PM₁₀ levels in Chandigarh remain higher than the prescribed annual ambient air quality standards (60 μg m^-3) of India. Seasonal Kendall test indicates a declining trend of PM₁₀ for the year 2003 to 2018 at an industrial and commercial site (1996-2016). There is a significant increase in NOx levels at all locations except at commercial sites. The results of the linear regression model and Theil-Sen slope show that SPM is declining at all locations, but results are not statistically significant. Interestingly, PM₁₀ levels at the industrial site display a significant declining trend (1.3% year^-1). Similarly, NOx levels are increasing at all sites but having a statistically significant trend at a rural location (8.9% year^-1) and residential site (15.2% year^-1). Air pollutants show strong seasonal variability having a higher concentration in post-monsoon and winter season, which found to be linked with regional anthropogenic activities such as crop residue burning and use of solid biomass fuel for cooking and other purposes. Lowest PM₁₀ levels were observed during the monsoon and having a decline of 47.4-66.4% as compared to winter levels. Site-specific variations in air pollutants were found to be associated with air quality improvement policies such as shifting of an interstate bus terminal, ban on diesel autos, including strict implementation of air quality norms on industries. As the relative contribution of various pollution sources is still unknown, the seasonal pattern of pollutants will help in knowing the background concentration of pollutants and could help to formulate evidence-based policies to mitigate air pollution under National Clean Air Programme (NCAP).

PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) and their derivatives (nitrated-PAHs and oxygenated-PAHs) in a road tunnel located in Qingdao, China: Characteristics, sources and emission factors

Daytime and nighttime PM_2.5 samples were collected at a road tunnel located in Qingdao, China. The mass concentrations and chemical compositions of polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (NPAHs) and oxygenated-PAHs (OPAHs) were analysed to determine the variation characteristics and sources. The concentrations in exit were obviously higher than those of entrance in the tunnel. Fluoranthene (FLT) and Pyrene (PYR) were the most abundant PAHs, 2 + 3-nitrofluoranthene (2 + 3N-FLA), 1-nitropyrene (1N-PYR) and 2-nitropyrene (2N-PYR) were the dominant NPAHs, and 9-fluorenone (9-FO) and 9,10-anthraquinone (9,10-ANQ) were the most abundant OPAHs. The high rings (4-6 rings) PAHs accounted for over 90% of the total PM_2.5-bound PAH concentrations, most of which were considered as motor vehicle emissions. Based on the diagnostics ratios and PCA results, the most important sources of PAHs and NPAHs were estimated as gasoline and diesel vehicles emissions in the tunnel. In addition, non-exhausts (such as road dust, brake line, asphalt and tires wear) also had some contributions to PAHs and NPAHs. The average emission factors were 60.98, 9.02 and 8.47 μg veh^-1 km^-1 for total PM_2.5-bound PAHs, NPAHs and OPAHs, respectively. The emission factors of high rings (4-6 rings) PAHs were greater than those with low rings (2-3 rings). 1N-PYR had the highest emission factor in all measured NPAHs, while the emission factors for the two highest OPAHs were 9-FO and 9,10-ANQ in this tunnel.

Source apportionment and seasonal variation in particulate PAHs levels at a coastal site in Belgium

In the present study, estimation of the atmospheric polycyclic aromatic hydrocarbons (PAHs) was done in particulate samples collected from De Haan, Belgium, during different seasons. The sampling site was situated very close to the north sea and far from the influence of local or industrial activities. The levels of PAHs depicted a distinct seasonal trend, being highest during the spring season. The observations of the study indicated a mean value of 2.6 ng m^-3 for concentration of all the 16 US EPA PAHs, thus being significantly lower when compared to results of previous studies focused on other sites. The dominating PAHs species reported were naphthalene, fluoranthene, benzo[a]anthracene, chrysene, and indeno[1,2,3c,d] pyrene. Assessment of the seasonal variation of the PAH levels was also done with respect to diagnostic ratio-based source identification, analysis of back trajectories, and principle component analysis. Burning of fossil fuels was observed to be the prominent source of atmospheric PAHs in the study area. Further, lifetime cancer risk assessment was performed to assess the detrimental health impacts on humans on being exposed to atmospheric PAHs. Particulate PAHs present in the ambient air of Belgium shows no carcinogenic health impacts. However, considering the industrial expansion in the region, efforts are required to prevent the environmental contamination of PAHs. Graphical abstract.

Current situation of polycyclic aromatic hydrocarbons (PAH) in PM2.5 in a receptor site in Mexico City and estimation of carcinogenic PAH by combining non-real-time and real-time measurement techniques

Air pollution is a public health concern. Polycyclic aromatic hydrocarbons (PAH) are ubiquitous atmospheric pollutants contained in the atmospheric aerosol. PAH in particulate matter with diameters ≤2.5 µm (PM_2.5) represent a human health risk due to their toxic properties. In this study, PAH in PM_2.5 at a receptor site of Mexico City during the dry cold season were determined. The most abundant PAH (median, 10-90th percentile, pg m^-3) were benzo[ghi]perylene (467, 291-697), followed by pyrene (427, 218-642). A decrease around 40% in the carcinogenic PAH onto PM_2.5 was calculated with respect to the same PAH measured a decade ago, at the same receptor site, despite of increase in vehicle fleet. The PAH decrease trend agrees with the decrease trend of CO, NO and NO₂, released into the air by similar emission sources than PAH. Control emissions strategies implemented by local and federal authorities are discussed. PAH analyses were carried out by non-real-time and real-time methods. The PAH non-real-time method involved PM_2.5 sampling, sample treatment and gas chromatography-mass spectrometry analysis. The PAH real-time method involved the use of a photoelectric aerosol sensor (PAS). The PAH determination by non-real time method was selective and efficient, with recoveries between 75 ± 14% and 98 ± 26%. By combining non-real-time and real-time methodologies, multivariate regression models were obtained based on PAS response, NO₂ and wind speed to estimate PAH in PM_2.5 at low-cost (r² = 0.59 to r² = 0.89). Fossil fuel combustion from vehicles was the major source around the sampling site. Diagnostic ratios (DR) based on retene, chrysene, and triphenylene, suggested biomass burning emission sources. Photo-oxidation in sunny months was observed based on benzo[a]pyrene, benzo[ghi]perylene, benz[a]anthracene, indeno[1,2,3-cd]pyrene and black carbon. The correlation analyses suggested transport of PM_2.5, O₃, BC and SO₂ to the sampling site, and local emissions of PAH, NO and CO.

High resolution vehicular PM10 emissions over megacity Delhi: Relative contributions of exhaust and non-exhaust sources

Exposure to particulate matter (PM) from traffic can cause adverse health risks. Recent studies project an increase in non-exhaust emissions in the future despite a reduction in exhaust emissions. While there is a lot of research on exhaust emissions, the challenges remain to quantify non-exhaust emissions, especially in developing countries. In this work, an approach has been developed, and on-road vehicular non-exhaust PM emissions are estimated due to brake wear, tyre wear, road wear and resuspension, at very high resolution (100 m²) over an Indian megacity Delhi. Further, the relative contribution of non-exhaust emissions to the total vehicular emission was also calculated. The total PM10 emissions in megacity Delhi were 31.5 Gg/year, which is mainly dominated by the non-exhaust sources. The non-exhaust emissions were found to be six times (86%) of the exhaust emission (14%). The highest contribution to the total vehicular PM emission comes from the cars (34%) followed by buses (23%) and heavy commercial vehicles (HCVs, 17%), which is dominated by resuspension of dust. Cars and buses contribute less to exhaust emissions and more to non-exhaust emissions. Majors roads are the largest contributors to the total emissions in Delhi. The emissions from HCVs, diesel cars along with the other diesel vehicles result in diesel vehicles contributing more than the petrol vehicles to both exhaust and non-exhaust emissions. As India target to reduce PM pollution under the national clean air program, the current study will be useful to plan a suitable intervention to mitigate air pollution and associated health impacts.

Characteristics, toxicity, source identification and seasonal variation of atmospheric polycyclic aromatic hydrocarbons over East India

Atmospheric PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs) were analyzed over urban and rural sites during January to December 2018. Total annual average concentration of PM_2.5 was 74.41 ± 24.96 μg/m³ over urban and 52.03 ± 13.11 μg/m³ over rural site during study time. The annual average concentration of PM_2.5 over urban and rural atmospheres were found approximately twice in urban and found also higher over rural site, with respect to National Ambient Air Quality (NAAQ) standard of 40 μg/m³ for PM_2.5 concentration. The annual concentration of PAHs was 750.80 ± 19.49 ng/m³ over urban, and, over rural, it was 559.59 ± 17.56 ng/m³. The seasonal variation of concentration of PAHs was in order of winter > post-monsoon > summer > monsoon. The most predominant PAHs were IcP (17.21%), B(ghi) P(15.22%), BkF (11.60%), DBahA (11.34%) and BbF (10.91%) to the total PAH concentration over urban site; over rural site, most predominant PAHs were IcP (16.02%), B(ghi)P, (15.63%), BkF (11.46%), DBahA (11.12%) and BbF (8.99%) of total PAHs. DBahA concentration was contributed approximately 46% carcinogenicity over both urban and rural sites, and BaP contributes 33.56% carcinogenicity over urban site and 34.62% carcinogenicity over rural site of total PAH samples. The Excess Life Time Cancer Risk (ELCR) values over urban were found at acceptable limit 10^-6-10^-4 given by the United States Environmental Protection Agency. Over rural site, the ELCR value was found near about acceptable limit. Diagnostic ratio analysis demonstrated that major sources of PAHs were pyrogenic sources and vehicular emission over study. Air parcel through trajectories over study site also contributed in PAH concentration.

Polycyclic aromatic hydrocarbons and their methylated derivatives in settled dusts from end-of-life vehicle processing, urban, and rural areas, northern Vietnam: Occurrence, source apportionment, and risk assessment

The occurrence and profiles of 19 polycyclic aromatic hydrocarbons (PAHs) and 15 methylated derivatives (Me-PAHs) were examined in settled dust samples collected from workplaces and living areas of an informal end-of-life vehicle (ELV) processing village, and house dusts from urban and rural areas in northern Vietnam. Concentrations of total PAHs and Me-PAHs decreased in the order: ELV workplace (median 5700, range 900-18,000 ng g^-1) > rural house (3700, 1800-6200 ng g^-1) > urban house (1800, 620-3100 ng g^-1) ≈ ELV living dusts (1000, 600-3900 ng g^-1). PAHs with 4 rings or more dominated in almost all the samples, indicating the abundance of pyrogenic sources (e.g., vehicular emissions and domestic thermal processes). Levels of Me-PAHs were exceeded those of PAHs in several ELV samples, revealing specific petrogenic sources derived from vehicle processing activities. Results from source apportionment analysis have partially identified traffic emission, biomass and coal combustion, and mixed petrogenic-pyrogenic sources related to ELV waste as the major sources of PAHs and Me-PAHs in the urban, rural, and ELV areas, respectively. Daily intake doses and health risk related to PAHs and Me-PAHs in settled dusts were estimated for ELV workers and residents living in the study areas. The worst exposure scenario of dust-bound PAHs showed a potential cancer risk for the ELV workers, meanwhile, no significant non-cancer and cancer risk was expected for other exposed groups. A more comprehensive and accurate risk assessment of PAHs and related compounds should be conducted in Vietnam.

Characterization and health risks of criteria air pollutants in Delhi, 2017

Severe air pollution events were observed frequently in north India in recent years especially at its capital, Delhi. Criteria air pollutants data at 10 sites for 2017 in Delhi were analyzed. The results show annual fine particulate matter (PM_2.5) concentrations exceeded the National Ambient Air Quality Standards (NAAQS) of 60 μg/m³ at all sites from 105.51 (site 10) to 143.23 μg/m³ (site 7). Sub-urban sites (site 8, 9 and 10) had lower PM_2.5 concentrations than urban sites. Coarse PM (PM₁₀) and ozone (O₃) were also important with annual averages of 399.56 μg/m³ and 75.69 ppb, respectively. Peak PM_2.5 occurred at the Diwali in early November and Christmas. Only PM₁₀ showed a significant weekly difference with a weekdays/weekends ratio of ∼1.5. PM_2.5/PM₁₀ ratio in episode days with PM_2.5 of >60 μg/m³ was higher than non-episode days. Pearson correlation coefficients show O₃ was negatively related with CO, SO₂, and NO₂, while PM_2.5 was positively related to these pollutants. Analysis of two extreme events from Nov. 6th to Nov. 14th and Dec. 18th to Dec. 26th shows that meteorological conditions with low wind speed and warm temperature kept PM_2.5 concentrations at a high level during these events. Backward trajectory and cluster analysis show the wind coming from northwest of Delhi, where massive anthropogenic emissions were generated, led to high concentrations of air pollutants to Delhi. Health risk analysis reveals that PM_2.5 and PM₁₀ were the two major pollutants threatening public health among the six criteria pollutants.

Interventions to reduce ambient particulate matter air pollution and their effect on health

BACKGROUND

Ambient air pollution is associated with a large burden of disease in both high-income countries (HICs) and low- and middle-income countries (LMICs). To date, no systematic review has assessed the effectiveness of interventions aiming to reduce ambient air pollution.

OBJECTIVES

To assess the effectiveness of interventions to reduce ambient particulate matter air pollution in reducing pollutant concentrations and improving associated health outcomes.

SEARCH METHODS

We searched a range of electronic databases with diverse focuses, including health and biomedical research (CENTRAL, Cochrane Public Health Group Specialised Register, MEDLINE, Embase, PsycINFO), multidisciplinary research (Scopus, Science Citation Index), social sciences (Social Science Citation Index), urban planning and environment (Greenfile), and LMICs (Global Health Library regional indexes, WHOLIS). Additionally, we searched grey literature databases, multiple online trial registries, references of included studies and the contents of relevant journals in an attempt to identify unpublished and ongoing studies, and studies not identified by our search strategy. The final search date for all databases was 31 August 2016.

SELECTION CRITERIA

Eligible for inclusion were randomized and cluster randomized controlled trials, as well as several non-randomized study designs, including controlled interrupted time-series studies (cITS-EPOC), interrupted time-series studies adhering to EPOC standards (ITS-EPOC), interrupted time-series studies not adhering to EPOC standards (ITS), controlled before-after studies adhering to EPOC standards (CBA-EPOC), and controlled before-after studies not adhering to EPOC standards (CBA); these were classified as main studies. Additionally, we included uncontrolled before-after studies (UBA) as supporting studies. We included studies that evaluated interventions to reduce ambient air pollution from industrial, residential, vehicular and multiple sources, with respect to their effect on mortality, morbidity and several air pollutant concentrations. We did not restrict studies based on the population, setting or comparison.

DATA COLLECTION AND ANALYSIS

After a calibration exercise among the author team, two authors independently assessed studies for inclusion, extracted data and assessed risk of bias. We conducted data extraction, risk of bias assessment and evidence synthesis only for main studies; we mapped supporting studies with regard to the types of intervention and setting. To assess risk of bias, we used the Graphic Appraisal Tool for Epidemiological studies (GATE) for correlation studies, as modified and employed by the Centre for Public Health Excellence at the UK National Institute for Health and Care Excellence (NICE). For each intervention category, i.e. those targeting industrial, residential, vehicular and multiple sources, we synthesized evidence narratively, as well as graphically using harvest plots.

MAIN RESULTS

We included 42 main studies assessing 38 unique interventions. These were heterogeneous with respect to setting; interventions were implemented in countries across the world, but most (79%) were implemented in HICs, with the remaining scattered across LMICs. Most interventions (76%) were implemented in urban or community settings.We identified a heterogeneous mix of interventions, including those aiming to address industrial (n = 5), residential (n = 7), vehicular (n = 22), and multiple sources (n = 4). Some specific interventions, such as low emission zones and stove exchanges, were assessed by several studies, whereas others, such as a wood burning ban, were only assessed by a single study.Most studies assessing health and air quality outcomes used routine monitoring data. Studies assessing health outcomes mostly investigated effects in the general population, while few studies assessed specific subgroups such as infants, children and the elderly. No identified studies assessed unintended or adverse effects.The judgements regarding the risk of bias of studies were mixed. Regarding health outcomes, we appraised eight studies (47%) as having no substantial risk of bias concerns, five studies (29%) as having some risk of bias concerns, and four studies (24%) as having serious risk of bias concerns. Regarding air quality outcomes, we judged 11 studies (31%) as having no substantial risk of bias concerns, 16 studies (46%) as having some risk of bias concerns, and eight studies (23%) as having serious risk of bias concerns.The evidence base, comprising non-randomized studies only, was of low or very low certainty for all intervention categories and primary outcomes. The narrative and graphical synthesis showed that evidence for effectiveness was mixed across the four intervention categories. For interventions targeting industrial, residential and multiple sources, a similar pattern emerged for both health and air quality outcomes, with essentially all studies observing either no clear association in either direction or a significant association favouring the intervention. The evidence base for interventions targeting vehicular sources was more heterogeneous, as a small number of studies did observe a significant association favouring the control. Overall, however, the evidence suggests that the assessed interventions do not worsen air quality or health.

AUTHORS' CONCLUSIONS

Given the heterogeneity across interventions, outcomes, and methods, it was difficult to derive overall conclusions regarding the effectiveness of interventions in terms of improved air quality or health. Most included studies observed either no significant association in either direction or an association favouring the intervention, with little evidence that the assessed interventions might be harmful. The evidence base highlights the challenges related to establishing a causal relationship between specific air pollution interventions and outcomes. In light of these challenges, the results on effectiveness should be interpreted with caution; it is important to emphasize that lack of evidence of an association is not equivalent to evidence of no association.We identified limited evidence for several world regions, notably Africa, the Middle East, Eastern Europe, Central Asia and Southeast Asia; decision-makers should prioritize the development and implementation of interventions in these settings. In the future, as new policies are introduced, decision-makers should consider a built-in evaluation component, which could facilitate more systematic and comprehensive evaluations. These could assess effectiveness, but also aspects of feasibility, fidelity and acceptability.The production of higher quality and more uniform evidence would be helpful in informing decisions. Researchers should strive to sufficiently account for confounding, assess the impact of methodological decisions through the conduct and communication of sensitivity analyses, and improve the reporting of methods, and other aspects of the study, most importantly the description of the intervention and the context in which it is implemented.

Emission of black carbon from rural households kitchens and assessment of lifetime excess cancer risk in villages of North India

The use of biomass solid fuels (BSFs) for cooking, contribute significantly to the household air pollution (HAP) in developing countries. Emissions resulting from a variety of BSFs (cow dung cakes, wood, and agriculture residues) contain a significant amount of air pollutants, which are now recognized for their role in climatic change and adverse human health impacts. In the current study, daily variations in black carbon (BC) or Short-Lived Climate Forcer concentrations were studied from rural household kitchens using portable aethalometer. The hourly average concentration of BC ranges from 5.4 μg·m^-3 to 34.9 μg·m^-3 for various types of household kitchens. The peak levels of BC were found to be significantly higher, when compared to World Health Organization PM_2.5 limits for ambient air and hence pose a threat to the health of the vulnerable population, i.e., women, children, older adults and those who have health problems. The study also highlights the variation of BC concentration in different kitchen type. The average BC concentration in indoor, outdoor and semi-open kitchen was observed to be 14.54, 14.28 and 24.69 μg·m^-3, respectively. The excess lifetime carcinogenic risk for cooking 4 h/day in these kitchens in the North Indian villages was estimated to be 1.25 × 10^-7, 1.22 × 10^-7, and 2.12 × 10^-7 respectively. Age-specific excess cancer deaths due to BC exposure were measured highest in children below four years of age in Chandigarh, India. Hence, there is a need to shift the BSF users to clean fuel alternatives to reduce the exposure to HAP. This can be achieved by generating local/regional evidences of BSFs associated health risks to support policy interventions. Further, more research is required to improve the air quality in indoor micro-environments and specifically in kitchens. NOVELTY: The first study reporting the near real-time measurements of BC from different types of rural households kitchens of north India. Diurnal pattern of BC concentration was also studied including the effect of chimney, ventilation and kitchen size on observed BC concentration. This study also estimates lifetime excess cancer risk due to BC exposure in rural households in India. The recent 'Global Burden of Disease' report identifies household air pollutants as a major cause of disease and disability in Asia. The study will help to plan suitable policies and intervention to reduce household air pollution in the region.

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.

Benzo(a)pyrene parallel measurements in PM1 and PM2.5 in the coastal zone of the Gulf of Gdansk (Baltic Sea) in the heating and non-heating seasons

Parallel measurements of PM₁ and PM_2.5 aerosols were conducted in the urbanized coastal zone of the southern Baltic Sea. The main aim of the research was to assess and determine annual, seasonal (heating and non-heating), and daily concentration variability of benzo(a)pyrene in aerosols, these being the most dangerous constituents to human health. The average annual concentration of benzo(a)pyrene (B(a)P) was equal to 2.6 ng·m^-3 in PM₁ and 4.6 ng·m^-3 in PM_2.5, and both values were several times higher than the level of 1 ng·m^-3 which was set out in the CAFE Directive. High mean daily concentrations of B(a)P persisted for 50 and 65% of the study period in PM1 and PM2.5, respectively. In order to determine the sources of B(a)P in both aerosol fractions, organic (OC) and elemental (EC) carbon concentrations were examined. The highest concentrations of all carbon species were reported during the heating season under local or regional land advection and at low air temperatures. The origin of pollutants was the same and was primarily related to the combustion of fossil fuels in the communal-utility sector. During the non-heating period, the role of transportation, both land and marine, increased and may have been significant in creating higher concentrations of carbon compounds in PM₁ and PM_2.5. Regardless of the size of the aerosol fractions, B(a)P loads introduced into the Baltic coastal zone were several times higher during the heating period compared to the non-heating season. Graphical abstract ᅟ.

Assessment of GHG mitigation and CDM technology in urban transport sector of Chandigarh, India

The increase in number of vehicles in metropolitan cities has resulted in increase of greenhouse gas (GHG) emissions in urban environment. In this study, emission load of GHGs (CO, N₂O, CO₂) from Chandigarh road transport sector has been estimated using Vehicular Air Pollution Inventory (VAPI) model, which uses emission factors prevalent in Indian cities. Contribution of 2-wheelers (2-w), 3-wheelers (3-w), cars, buses, and heavy commercial vehicles (HCVs) to CO, N₂O, CO₂, and total GHG emissions was calculated. Potential for GHG mitigation through clean development mechanism (CDM) in transport sector of Chandigarh under two scenarios, i.e., business as usual (BAU) and best estimate scenario (BES) using VAPI model, has been explored. A major contribution of GHG load (~ 50%) in Chandigarh was from four-wheelers until 2011; however, it shows a declining trend after 2011 until 2020. The estimated GHG emission from motor vehicles in Chandigarh has increased more than two times from 1065 Gg in 2005 to 2486 Gg by 2011 and is expected to increase to 4014 Gg by 2020 under BAU scenario. Under BES scenario, 30% of private transport has been transformed to public transport; GHG load was possibly reduced by 520 Gg. An increase of 173 Gg in GHGs load is projected from additional scenario (ADS) in Chandigarh city if all the diesel buses are transformed to CNG buses by 2020. Current study also offers potential for other cities to plan better GHG reduction strategies in transport sector to reduce their climate change impacts.

Household air pollution from various types of rural kitchens and its exposure assessment

Exposure to household air pollutants has become a leading environmental health risk in developing countries. Considering this, real-time temporal variation in fine particulate matter (PM_2.5) and carbon monoxide (CO) concentrations were measured in various types of rural household kitchens. Observed average concentrations of PM_2.5, CO, percent relative humidity (%RH) and temperature (T) in five different kitchen types were 549.6μg/m³, 4.2ppm, 70.2% and 20°C respectively. Highest CO and PM_2.5 concentration were found in household performing cooking in indoor kitchens (CO: 9.3ppm; PM_2.5: 696.5μg/m³) followed by outdoor kitchens (CO: 5.8ppm; PM_2.5: 539.5μg/m³). The concentration of PM_2.5 and CO varied according to the fuel type and highest concentration was observed in kitchens using cowdung cakes followed by agricultural residue>firewood>biogas>Liquefied Petroleum Gas (LPG). Results revealed that the pollutants concentration varied with kitchen type, fuel type and the location of kitchen. An exposure index was developed to calculate the exposure of cook, non-cook and children below 5years. Analysis of exposure index values shows that cooks, who use solid biomass fuel (SBF) in indoor kitchen, are four times more exposed to the harmful pollutants than the cooks using clean fuel. Further, using indoor PM_2.5 concentrations, hazard quotient was calculated based on evaluation of intake concentration and toxicological risk, which also shows that SBF users have higher health risks (hazard quotient>1) than the clean fuel (LPG) users.

Source Apportionment of PM10-Bound Polycyclic Aromatic Hydrocarbons by Positive Matrix Factorization in Córdoba City, Argentina

The composition and concentration of polycyclic aromatic hydrocarbons (PAHs) adsorbed on particles smaller than 10 microns (PM₁₀) were analyzed in an urban area during a 2-year period from August 2011 to August 2013. Diagnostic ratios (DR) and positive matrix factorization (PMF) were employed to assess emission sources. To discount weather influence, a multiple linear regression model was generated and also a photodecomposition index was calculated for each sample. Despite the fact that mean PM₁₀ levels showed a similar pattern all around the year, majority of PAHs showed higher concentrations during the cold than the warm period, indicating a strong seasonal variation. A 38% of PAHs variation could be explained by meteorological variables, with wind speed, wind direction, and dew point being the significant regressor variables in the model. The source apportionment of PAHs was performed using PMF although they are photosensitive compounds. The sampling period was separated in warm and cold seasons according to a photodecomposition index and cold period was used. Also, DR were calculated. DR as well as PMF analysis suggested that both gasoline and diesel vehicular emissions are the main PAHs emission sources in this urban area.

Evaluating the impacts of the clean cities program

The Department of Energy's Clean Cities program was created in 1993 to reduce petroleum usage in the transportation sector. The program promotes alternative fuels such as biofuels and fuel-saving strategies such as idle reduction and fleet management through coalitions of local government, non-profit, and private actors. Few studies have evaluated the impact of the program because of its complexity that include interrelated strategies of grants, education and training and diversity of participants. This paper uses a Difference-in-Differences (DiD) approach to evaluate the effectiveness of the program between 1990 and 2010. We quantify the effectiveness of the Clean Cities program by focusing on performance measures such as air quality, number of alternative fueling stations, private vehicle occupancy and transit ridership. We find that counties that participate in the program perform better on all these measures compared to counties that did not participate. Compared to the control group, counties in the Clean Cities program experienced a reduction in days with bad air quality (3.7%), a decrease in automobile commuters (2.9%), an overall increase in transit commuters (2.1%) and had greater numbers of new alternative fueling stations (12.9). The results suggest that the program is a qualified success.

Risk assessment of PBDEs and PAHs in house dust in Kocaeli, Turkey: levels and sources

Indoor dust samples were collected from 40 homes in Kocaeli, Turkey and were analyzed simultaneously for 14 polybrominated diphenyl ethers (PBDEs) and 16 poly aromatic hydrocarbons (PAHs) isomers. The total concentrations of PBDEs (Σ₁₄PBDEs) ranged from 29.32 to 4790 ng g^-1, with a median of 316.1 ng g^-1, while the total indoor dust concentrations of 16 PAHs (Σ₁₆PAHs) extending over three to four orders of magnitude ranged from 85.91 to 40,359 ng g^-1 with a median value of 2489 ng g^-1. Although deca-PBDE products (BDE-209) were the principal source of PBDEs contamination in the homes (median, 138.3 ng g^-1), the correlation in the homes was indicative of similar sources for both the commercial penta and deca-PBDE formulas. The PAHs diagnostic ratios indicated that the main sources of PAHs measured in the indoor samples could be coal/biomass combustion, smoking, and cooking emissions. For children and adults, the contributions to ∑₁₄PBDEs exposure were approximately 93 and 25 % for the ingestion of indoor dust, and 7 and 75 % for dermal contact. Exposure to ∑₁₆PAHs through dermal contact was the dominant route for both children (90.6 %) and adults (99.7 %). For both groups, exposure by way of inhalation of indoor dust contaminated with PBDEs and PAHs was negligible. The hazard index (HI) values for BDE-47, BDE-99, BDE-153, and BDE-209 were lower than the safe limit of 1, and this result suggested that none of the population groups would be likely to experience potential health risk due to exposure to PBDEs from indoor dust in the study area. Considering only ingestion + dermal contact, the carcinogenic risk levels of both B2 PAHs and BDE-209 for adults were 6.2 × 10^-5 in the US EPA safe limit range while those for children were 5.6 × 10^-4 and slightly higher than the US EPA safe limit range (1 × 10^-6 and 1 × 10^-4). Certain precautions should be considered for children.

Emission factors of air pollutants from CNG-gasoline bi-fuel vehicles: Part I. Black carbon

Compressed natural gas (CNG) is considered to be a "cleaner" fuel compared to other fossil fuels. Therefore, it is used as an alternative fuel in motor vehicles to reduce emissions of air pollutants in transportation. To quantify "how clean" burning CNG is compared to burning gasoline, quantification of pollutant emissions under the same driving conditions for motor vehicles with different fuels is needed. In this study, a fleet of bi-fuel vehicles was selected to measure the emissions of black carbon (BC), carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NO_x) for driving in CNG mode and gasoline mode respectively under the same set of constant speeds and accelerations. Comparison of emission factors (EFs) for the vehicles burning CNG and gasoline are discussed. This part of the paper series reports BC EFs for bi-fuel vehicles driving on the real road, which were measured using an in situ method. Our results show that burning CNG will lead to 54%-83% reduction in BC emissions per kilometer, depending on actual driving conditions. These comparisons show that CNG is a cleaner fuel than gasoline for motor vehicles in terms of BC emissions and provide a viable option for reducing BC emissions cause by transportation.

Microscale spatial distribution and health assessment of PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) at nine communities in Xi'an, China

Spatial variability of polycyclic aromatic hydrocarbons (PAHs) associated with fine particulate matter (PM_2.5) was investigated in Xi'an, China, in summer of 2013. Sixteen priority PAHs were quantified in 24-h integrated air samples collected simultaneously at nine urban and suburban communities. The total quantified PAHs mass concentrations ranged from 32.4 to 104.7 ng m^-3, with an average value of 57.1 ± 23.0 ng m^-3. PAHs were observed higher concentrations at suburban communities (average: 86.3 ng m^-3) than at urban ones (average: 48.8 ng m^-3) due to a better enforcement of the pollution control policies at the urban scale, and meanwhile the disorganized management of motor vehicles and massive building constructions in the suburbs. Elevated PAH levels were observed in the industrialized regions (west and northwest of Xi'an) from Kriging interpolation analysis. Satellite-based visual interpretations of land use were also applied for the supporting the spatial distribution of PAHs among the communities. The average benzo[a]pyrene-equivalent toxicity (Σ[BaP]_eq) at the nine communities was 6.9 ± 2.2 ng m^-3 during the sampling period, showing a generally similar spatial distribution to PAHs levels. On average, the excess inhalation lifetime cancer risk derived from Σ[BaP]_eq indicated that eight persons per million of community residents would develop cancer due to PM_2.5-bound PAHs exposure in Xi'an. The great in-city spatial variability of PAHs confirmed the importance of multiple points sampling to conduct exposure health risk assessment.

Application of PAH concentration profiles in lake sediments as indicators for smelting activity

The ability of lake sediment cores to store long-term anthropogenic pollution establishes them as natural archives. In this study, we focus on the influence of copper shale mining and smelting in the Mansfeld area of Germany, using the depth profiles of two sediment cores from Lake Süßer See. The sediment cores provide a detailed chronological deposition history of polycyclic aromatic hydrocarbons (PAHs) and heavy metals in the studied area. Theisen sludge, a fine-grained residue from copper shale smelting, reaches the lake via deflation by wind or through riverine input; it is assumed to be the main source of pollution. To achieve the comparability of absolute contaminant concentrations, we calculated the influx of contaminants based on the sedimentation rate. Compared to the natural background concentrations, PAHs are significantly more enriched than heavy metals. They are therefore more sensitive and selective for source apportionment. We suggest two diagnostic ratios of PAHs to distinguish between Theisen sludge and its leachate: the ratio fluoranthene to pyrene ~2 and the ratio of PAH with logKOW<5.7 to PAH with a logKOW>5.7 converging to an even lower value than 2.3 (the characteristic of Theisen sludge) to identify the particulate input in lake environments.

Geochemical markers and polycyclic aromatic hydrocarbons in solvent extracts from diesel engine particulate matter

Exhaust particulate from compression ignition (CI) engines running on engine and chassis dynamometers was studied. Particulate dichloromethane extracts were qualitatively and quantitatively analyzed for polycyclic aromatic hydrocarbons (PAHs) and biomarkers by gas chromatography with flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS). PAH group profiles were made and the PAH group shares according to the number of rings (2 or 3; 4; 5 or more) as well as diagnostic indices were calculated. Values of geochemical ratios of selected biomarkers and alkyl aromatic hydrocarbons were compared with literature values. A geochemical interpretation was carried out using these values and biomarker and alkyl aromatic hydrocarbon distributions. It has been shown that geochemical features are unequivocally connected to the emission of fossil fuels and biofuels burned in CI engines. The effect of the exothermic combustion process is limited to low-molecular-weight compounds, which shows that the applied methodology permits source identification of PAHs coexisting in the particulate emitted.

Chemical characteristics and mutagenic activity of PM₂.₅ at a site in the Indo-Gangetic plain, India

Airborne fine particulate matter PM2.5 was collected from May 2010 to December 2012 at Agra, a semi-urban site in north-central India. PM2.5 samples were chemically characterized for 16 polycyclic aromatic hydrocarbons by gas chromatography. PM2.5 values varied between 8.4 and 300 µg m(-3) with 55% of the values exceeding the 24h average NAAQ (National Ambient Air Quality) standard of 65 µg m(-3). Particle associated total PAHs ranged between 8.9 and 2,065 ng m(-3) with a mean value of 880.8 ng m(-3) during the sampling period, indicated an alarming level of pollution in Agra. Strong relationship was observed between PM2.5 and total PAHs (r=0.88), suggesting an increasing PAHs concentration with increasing PM2.5 mass. On a mass basis 3-ring and 4-ring compounds were dominant. Seasonal variation in mass concentration of PAHs was observed with high concentration in winter followed by post monsoon, summer and monsoon. This seasonal pattern could be attributed to differences in source strength and climatic conditions. PAHs concentration were also observed to be negatively correlated with the meteorological parameters i.e. temperature, solar radiation, relative humidity and wind speed. Molecular diagnostic ratios revealed vehicular emissions and combustion of wood and coal as the probable sources. The estimated carcinogenicity of PAHs in terms of benzo(a)pyrene toxic equivalency (B[a]PTEQ) was assessed and confirmed that benzo[a]pyrene was the dominant PAH contributor (3.64%). Health risk of adults and children by way of PAHs was assessed by estimating the lifetime average daily dose (LADD) and corresponding incremental lifetime cancer risk (ILCR) using USEPA guidelines. The assessed cancer risk (ILCR) was found to be within the acceptable range (10(-6)-10(-4)). The particulate samples indicated the presence of both base pair and frame shift mutagens using TA98 and TA100 strains of Salmonella typhimurium. Enhanced mutagenic response was observed in the presence of enzyme activation.

An investigation of potential regional and local source regions affecting fine particulate matter concentrations in Delhi, India

In this study, potential regional and local sources influencing PM2.5 (particulate matter with an aerodynamic diameter >2.5 μm) concentrations in Delhi, India, are identified and their possible impact evaluated through diverse approaches based on study of variability of synoptic and local airflow patterns that transport aerosol concentrations from these emission sources to an urban receptor site in Delhi, India. Trajectory clustering of 72-hr and 48-hr back trajectories simulated at arrival heights of 500 m and 100 m, respectively, every hour for representative years 2008-2010 are used to assess the relative influence of long-distance, regional, and subregional sources on this site. Nonparametric statistical procedures are employed on trajectory clusters to better delineate various distinct regional pollutant source regions. Trajectory clustering and concentration-weighted trajectory (CWT) analyses indicate that regional and subregional PM2.5 emission sources in neighboring country of Pakistan and adjacent states of Punjab, Haryana, and Uttar Pradesh contribute significantly to the total surplus of aerosol concentrations in the Delhi region. Conditional probability function and Bayesian approach used to identify local source regions have established substantial influence from highly urbanized satellite towns located southwest (above 25%) and southeast (above 45%) of receptor location. There is significant seasonal variability in synoptic and local air circulation patterns, which is discerned in variability in seasonal concentrations. Mean of daily averaged PM2.5 concentrations at the Income Tax Office (ITO) receptor site over Delhi at 95% confidence level is highest in winter, ranging between 209 and 185 μg m⁻³ for the entire study period. The annual variability in air transport pathways is more in winter than in other seasons. Year-to-year variability is present in aerosol concentrations, especially during winter, with standard deviations varying from a minimum of 60 µg m⁻³ in winter 2009 to a maximum of 109 µg m⁻³ in winter 2010.

Toxicity evaluation and source apportionment of Polycyclic Aromatic Hydrocarbons (PAHs) at three stations in Istanbul, Turkey

This paper focuses on the toxicity evaluation and source apportionment of Polycyclic Aromatic Hydrocarbons (PAHs) in three monitoring stations in Istanbul, Turkey. A total of 326 airborne samples were collected and analyzed for 16 PAHs and Total Suspended Particles (TSP) for the period of September 2006-December 2007. The total average PAH concentrations were 100.7±61.3, 84.6±46.7 and 25.1±13.3 ng m(-3) and the TSP concentrations were 101.2±53.2, 152.3±99.1, 49.8±18.6 μg m(-3) for URB1, URB2 and RUR stations, respectively. Benzo(a)Pyren (BaP) toxic equivalency factors to PAH concentration values were calculated indicating that the health risk of BaP and DiBenz(a,h)Anthracene (markers of traffic emissions) have the highest contribution compared to all of the other species measured at the sampling sites. In order to determine PAH sources, two different source apportionment techniques were applied to the measurements; diagnostic ratios (DR) and Positive Matrix Factorization (PMF). The results of the two applications were compatible indicating the vehicle emissions - especially diesel engines - as the major source for urban stations.

Polycyclic aromatic hydrocarbons study in atmospheric fine and coarse particles using diagnostic ratios and receptor model in urban/industrial region

Atmospheric fine and coarse particles were collected in Teflon filters in three cities of the region of the Lower Sinos River Basin of Rio Grande do Sul in the year 2010. The filters were Soxhlet extracted, and 14 priority PAHs were analyzed using a gas chromatograph coupled to a mass spectrometer (GC/MS). The principal emission sources of these compounds were assessed by using diagnostic ratios and receptor model: positive matrix factorization (PMF 3.0) of the US Environmental Protection Agency. The results of PAHs concentration for the studied year showed significant levels of high molecular weight (HMW) PAH, Ind, and BghiP, in PM2.5 in the winter season, showing the influence of mobile sources. The application of receptor model PMF 3.0 revealed that the main sources of PAHs were vehicle fleet (both diesel and gasoline), followed by coal combustion, wood combustion, and resuspension of dust. The results of the receptor modeling are in agreement with the data obtained by the ratio diagnostic.

Monitoring of polyaromatic hydrocarbons and volatile organic compounds in two major traffic tunnels in Seoul, Korea

To describe the fundamental aspects of air quality in tunnel environments, field campaigns were conducted to measure polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and some criteria pollutants from two tunnel sites of Nam San (NS) and Hong Ji (HJ) gates in Seoul, Korea. The total PAH values (ngm(-3)) for the NS tunnel (137.8 +/- 10.9) were notably higher than the HJ counterpart (91.3 +/- 7.82), while the total VOC exhibited a reversed pattern with a notable enhancement in the HJ tunnel (178.5 +/- 174.7 ppbC) relative to the NS tunnel (112.5 +/- 64.1 ppbC). A line of evidence, including the molecular diagnostic ratios of PAHs, indicates the relative dominance of diesel vehicles in the NS tunnel compared to the HJ site. The PAHs with high ring numbers (n > 6, such as benzo(g, h, i)perylene and indeno(1,2,3-cd)pyrene) were preferentially enriched in the particle phase, whereas their low ring number counterparts (n = 2-3) were in the gas phase. The results of our study suggest the possibility that the relative source processes for each tunnel site are characterized by the relative dominance of either diesel (NS) or gasoline-powered vehicles (HJ).

Preliminary characterization of polycyclic aromatic hydrocarbons, nitrated polycyclic aromatic hydrocarbons and polychlorinated dibenzo-p-dioxins and furans in atmospheric PM10 of an urban and a remote area of Chile

The composition of particulate organic fraction was determined in atmospheric aerosols emitted in two sites of central and southern Chile. In particular, polycyclic aromatic hydrocarbons (PAHs), nitrated-PAHs (N-PAHs) and polychlorinated dibenzo-p-dioxins (PCDDs) and furans (PCDFs) were investigated in both the urban site of Concepcion and the remote site of Coyhaique. The sampling was carried out with an active device during March and April 2007, and organic compounds adsorbed in air particles, having an aerodynamic diameter lower than 10 microm (PM10), were characterized using gas chromatography coupled with mass spectrometric detection (GC-MS). Aerosol contents varied from 0.004 to 3.4 ng m(-3) for PAH, from 0.007 to 3.5 pg m(-3) for N-PAH, from 0.002 to 355.7 fg Nm(-3) for PCDDs and from 0.04 to 15 fg Nm(-3) for PCDFs. As expected, the lowest values were found in the remote area. In Concepcion city, despite the low number of samples, PAH levels and diagnostic ratios of some marker compounds suggested the diesel emissions, probably coming from trucks, as the major source of particulate organic pollutants associated with direct emission. Another important source of atmospheric pollution in the urban site was likely represented by the steel industry existing in this area, outlined both by the analysis of PAH and PCDD/F levels. In the samples collected in the remote air of Coyhaique (located in the southern part of Chile), the concentration of pollutants characterized by a long lifetime, as PCDD/Fs, could be related to long-range transport phenomena, instead of local sources.

Distribution and characteristic of PAHs in snow of Fildes Peninsula

Polycyclic aromatic hydrocarbons (PAHs) investigation in different matrices has been reported largely, whereas reports on snow samples were limited. Snow, as the main matrix in the polar region, has an important study meaning. PAHs in snow samples were analyzed to investigate the distribution and contamination status of them in the Antarctic, as well as to provide some references for global migration of PAHs. Snow samples collected in Fildes Peninsula were enriched and separated by solid-phase membrane disks and eluted by methylene dichloride, then quantified by gas chromatography/mass spectrometry. All types of PAHs were detected except for Benzo(a)pyrene. Principal component analysis method was applied to characterize them. Three factors (Naphthalene, Fluorene and Phenanthrene) accounted for 60.57%, 21.61% and 9.80%, respectively. The results showed that the major PAHs sources maybe the atmospheric transportation, and the combustion of fuel in Fildes Peninsula. The comparison of concentration and types of PAHs between accumulated snow and fresh snow showed that the main compound concentrations in accumulated snow samples were higher than those in fresh ones. The risk assessment indicated that the amount of PAHs in the snow samples would not lead to ecological risk.

Chemical composition of ambient particulate matter and redox activity

Exposure to ambient particulate matter (PM) has been associated with a number of adverse health effects. Increasing studies have suggested that such adverse health effects may derive from oxidative stress, initiated by the formation of reactive oxygen species (ROS) within affected cells. The study aimed to assess physical characteristics and chemical compositions of PM and to correlate the results to their redox activity. PM(2.5) (mass aerodynamic diameter < or =2.5 microm) and ultrafine particles (UFPs, mass media aerodynamic diameter <0.1 microm) were collected in an urban area, which had heavy traffic and represented ambient air pollution associated with vehicle exhaust. Background samples were collected in a rural area, with low traffic flow. Organic carbon (OC), elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs), and metals were analyzed. The dithiothreitol activity assay was used to measure the redox activity of PM. Results showed that UFPs have higher concentrations of OC, EC, and PAHs than those of PM(2.5). Several metals, including Fe, Cu, Zn, Ti, Pb, and Mn, were detected. Among them, Cu had the highest concentrations, followed by Fe and Zn. Organic carbon constituted 22.8% to 59.7% of the content on the surface of PM(2.5) and UFPs. Our results showed higher redox activity on a per PM mass basis for UFPs as compared to PM(2.5). Linear multivariable regression analyses showed that redox activity highly correlated with PAH concentrations and organic compounds, and insignificantly correlated with EC and metals, except soluble Fe, which increased redox activity in particle suspension due to the presence of ROS.

Activity pattern and personal exposure to nitrogen dioxide in indoor and outdoor microenvironments

People are exposed to air pollution from a range of indoor and outdoor sources. Concentrations of nitrogen dioxide (NO(2)), which is hazardous to health, can be significant in both types of environments. This paper reports on the measurement and analysis of indoor and outdoor NO(2) concentrations and their comparison with measured personal exposure in various microenvironments during winter and summer seasons. Furthermore, the relationship between NO(2) personal exposure in various microenvironments and including activities patterns were also studied. Personal, indoor microenvironments and outdoor measurements of NO(2) levels were conducted using Palmes tubes for 60 subjects. The results showed significant differences in indoor and outdoor NO(2) concentrations in winter but not for summer. In winter, indoor NO(2) concentrations were found to be strongly correlated with personal exposure levels. NO(2) concentration in houses using a gas cooker was higher in all rooms than those with an electric cooker during the winter campaign, whereas there was no significant difference noticed in summer. The average NO(2) levels in kitchens with a gas cooker were twice as high as those with an electric cooker, with no significant difference in the summer period. A time-weighted average personal exposure was calculated and compared with measured personal exposures in various indoor microenvironments (e.g. front doors, bedroom, living room and kitchen); including non-smokers, passive smokers and smoker. The estimated results were closely correlated, but showed some underestimation of the measured personal exposures to NO(2) concentrations. Interestingly, for our particular study higher NO(2) personal exposure levels were found during summer (14.0+/-1.5) than winter (9.5+/-2.4).

Exposure of smoke solutions from CNG-powered four-stroke auto-rickshaws induces distressed embryonic movements, embryonic hemorrhaging and ectopia cordis

In south Asian countries, a campaign has launched to promote CNG-powered four-stroke auto-rickshaws (CNFAR) to decrease emission load in the environment. Even though, CNFAR are considered environmentally safe, emissions of some other toxic chemicals would amplify, which may effect the development of growing fetus and may result in different growth defects. By utilizing the in vivo chicken embryo model, this report analyzes the toxic potential of CNFAR smoke solutions (CNFARSS) on embryonic movements (EM) and cardiovascular development. Application of CNFARSS to embryos caused profound decline (p<0.001) in all four types of EMs. Several recovery attempts of all EMs were observed in oscillating fashion, however, EMs did not recover by the end of experiment. Exposure of CNFARSS escorted intense decline (p<0.001) with temperate recovery phases in the EM of tail. Macroscopic evaluation of all CNFARSS treated chicken embryos revealed several widespread hemorrhaging throughout the whole body. Moreover, four different types of ectopia cordis were prominently observed among all CNFARSS treated embryos, namely; incomplete ectopia cordis, complete ectopia cordis, cervico-thoracic ectopia cordis and thoraco-abdominal ectopia cordis.

Climate impacts of air quality policy: switching to a natural gas-fueled public transportation system in New Delhi

Between 2001 and 2003, public transport vehicles in New Delhi were required to switch their fuel to natural gas in an attemptto reduce their air pollution impacts. This study examines the climatic impacts of New Delhi's fuel switching policy, and outlines implications for such efforts in rapidly industrializing countries. Natural gas is mostly composed of methane, an important greenhouse gas. Emitted aerosols (black carbon, particulate organic carbon, and sulfate) also cause radiative forcing. We find that methane and black carbon emissions are critical contributors to the change in carbon dioxide equivalent [CO2(e)] emissions. In New Delhi, the switch to natural gas results in a 30% increase in CO2(e) when the impact of aerosols is not considered. However, when aerosol emissions are taken into account in our model, the net effect of the switch is estimated to be a 10% reduction in CO2(e), and there may be as much as a 30% reduction in CO2(e). There is significant potential for emissions reductions through the United Nations Framework Convention on Climate Change (UNFCCC) Clean Development Mechanism for such fuel switching projects.

Variation in particulate PAHs levels and their relation with the transboundary movement of the air masses

The levels of particulate polycyclic aromatic hydrocarbons (PAHs) were determined with a fast analytical approach to study their seasonal variations at Menen (Belgium) during 2003; they were found to be 5-7 times higher in January, February and December, in comparison to May, June and August. The annual average concentration of the sum of 16 US Environmental Protection Agency (EPA) criteria PAHs was 6.7 ng/m3 and around 63% of it was found to be probably carcinogenic to humans. The application of diagnostic ratio and principal component analysis showed vehicular emission as a major source. An increased ratio of 'combustion PAHs' to 'total EPA-PAHs' during the winter season indicated towards combustion activities. Further, the differences in PAHs concentration were assessed with relation to backward air mass trajectories, which show that the levels of PAHs increase when there is an air mass movement from Central and Western Europe and a fall when the trajectories spend most of their 4-day time over the Atlantic Ocean or in the Arctic region.

Temporal variability of benzene concentration in the ambient air of Delhi: a comparative assessment of pre- and post-CNG periods

CNG (compressed natural gas) was fully implemented in public transport system in Delhi in December 2002. The study assesses the benzene concentration trends at two busy traffic intersections and a background site in Delhi, India. Monitoring was done for two different time periods viz; in the year 2001-2002 (pre-CNG) and two winter months (January and February) of the year 2007 (post-CNG) to assess the impact of various policy measures adopted by the government of Delhi to improve the air quality in the city. Annual average benzene concentration for the pre-CNG period was found to be 86.47+/-53.24 microg m(-3). Average benzene concentrations for the winter months (January-February) of pre- and post-CNG periods were 116.32+/-51.65 microg m(-3) and 187.49+/-22.50 microg m(-3), respectively. Enhanced values could be solely attributed to the increase in the vehicular population from 3.5 million in the year 2001-2002 to approximately 5.1 millions in the year 2007.

The recent deposition of persistent organic pollutants and mercury to the Dasuopu glacier, Mt. Xixiabangma, central Himalayas

High mountains may serve as condensers for persistent organic pollutants (POPs) and the ice/snow core can provide long-term records of atmospheric deposition of pollutants. In this study, organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in firn core from Dasuopu Glacier were analyzed and the seasonal variation and deposition flux of these pollutants were investigated. PCB 28 was always detected in samples from different firn core layers and concentrations of PCB 28 were in the range of 0.09-0.3 ng/l. Hexachlorobenzene (HCB) and total DDTs (p-p'-DDD and p-p'-DDT) were not always detected and were only present in some samples. No p-p'-DDE and hexachlorocyclohexane (HCH) were detected above the level of determination limits. Concentrations of HCB ranged from 0.04 to 0.07 ng/l, and total DDTs were in the range of 0.15-0.3 ng/l. Total glacier PAHs was below 26 ng/l. The levels of OCPs and PAHs in Dasuopu glacier were roughly similar to values from the European mountain areas but lower than those from Lys glacier (Italy) and glacier from Rocky Mountain. Hg concentration (2-35 ng/l) in firn core samples was higher than that of remote region of Arctic. PCB 28 didn't show obvious variation in different seasons, however for major PAH compounds higher values were observed in summer than in winter. With regard to Hg, it displayed winter maximum. Deposition flux of OCPs, PAHs and mercury showed similar results with maximum flux occurring in the 2000s. After 2000/2001, deposition flux decreased and reflected the possible decrease of emissions of these atmospheric pollutants in the adjacent region.