Phenomenological study of Benzo[a]Pyrene and cyclopenteno[cd]pyrene decay in ambient air using Winter/Summer comparisons

Seasonal exposure to PM2.5-bound polycyclic aromatic hydrocarbons and estimated lifetime risk of cancer: A pilot study

Limited researches are available on seasonal variation of inhalation exposure of polycyclic aromatic hydrocarbons (PAHs) and its cancer risk assessment in China. We recruited 20 fresh postgraduates and measured outdoor and indoor (dormitories, offices and laboratories) daily PM_2.5 concentrations in four seasons (seven consecutive days in every season) during 2014 -2015, calculated daily potential doses of personal exposure to total Benzo[a]pyrene equivalent concentration (BaPeq) in the microenvironments based on the total BaPeq and the time-activity patterns, and estimated incremental lifetime cancer risk (ILCR) using Monte Carlo method. Daily average concentrations of PM_2.5-bound ∑PAHs on the campus ranked from high to low were winter, autumn, spring, summer in the dormitories and offices. Daily average concentration of PM_2.5-bound ∑PAHs were higher in indoor environments than outdoor in the same season, except for that of PM_2.5-bound ∑PAHs in laboratories in the winter. Median values of ILCR in both sexes from high to low were winter (men vs. women: 5.35e^-9 vs. 4.96e^-9), spring (3.71e^-9 vs. 4.00e^-9), autumn (2.92e^-9 vs. 3.02e^-9), summer (1.71e^-9 vs. 1.87e^-9). Indoor and outdoor PM_2.5-bound PAHs concentrations showed seasonal and spatial variations. The ILCR value for PM_2.5-bound PAHs was higher in women than in men.

Volatilization and oxidative artifacts of PM bound PAHs collected at low volume sampling (1): Laboratory and field evaluation

Laboratory and field studies were carried out to assess the effects of oxidative degradation and volatilization on PM₁₀ bound polycyclic aromatic hydrocarbons (PAHs), collected at low volume condition according to the EU sampling reference method EN12341:2014 (flow rate 2.3 m³ h^-1), on 47 mm quartz filters. For the laboratory experiments, pairs of twin samples were collected in field and, after treatments favoring decomposition or/and volatilization of PAHs on one sample, the PAH amount was compared with that of the corresponding untreated sample. Ozone exposure caused a general PAHs decay with more marked effects on benzo [a]pyrene, perylene and benz [a]anthracene; these compounds showed, similarly to benzo [ghi]perylene, correlations between ozone dose and losses. Treatments with zero air exhibited losses due to volatilization even for 5-ring PAHs up to benzo [a]pyrene, whereas a linear dependence was observed between filter PAH load and losses for benzo [a]anthracene, chrysene and benzofluoranthenes. Concentrations on samples collected simultaneously over 48, 24, 12 and 6 h were compared. Results confirmed a lack of temporal auto-consistency in the PAHs sampling methodology here adopted. In particular higher atmospheric PAH concentrations were ascertained on samples constituted by cumulative filters exposed over shorter sampling times. When 24-h and 2 × 12-h samples were compared, comparable losses were evaluated in the hot and cold seasons. This finding shows that, although in summer meteorology conditions favor sampling artifacts, the effectiveness of these phenomena continue in the winter, probably due to the larger amount of PAH available on the sampling filter (total PAHs ∼ 10 vs 0.5 ng m^-3).

Concentrations of PAHs and other gaseous pollutants in the atmosphere of a rural area

In this study, concentrations of polycyclic aromatic hydrocarbons (PAHs) bound to PM10 particles were measured in a Croatian rural area. Considering that by now only a limited number of studies have provided data on pollutant concentrations for rural areas, our aim was to do so by determining the PAH levels, their mutagenic effect and relationship with meteorological conditions and other gaseous pollutants (NO, NO2, NH3). In this investigation, samples of PM10 particles were collected on quartz filters for 1 month in the cold period and 1 month in the warm period of the year, 24 h a day. Diagnostic PAH concentration ratios and factor analysis were used as tools to identify and characterize the PAH sources. The PAHs found in the warm period of the year were characteristic for car exhaust emissions while the predominant source of these pollutants in the cold period was wood burning. The measurements showed much higher average concentrations of all PAHs in the cold period, most pronounced for fluoranthene 0.347 ng m(-3) and pyrene 0.223 ng m(-3). Mass concentrations of benzo(a)pyrene in the cold period ranged from 0.057 to 1.526 ng m(-3), while in the warm period they varied from 0.009 to 0.111 ng m(-3). Mutagenicity related to BaP (BaPMeq) was significantly higher during the cold period (1.095 ng m(-3)) than in the warm period (0.101 ng m(-3)).

Carcinogenic activity of polycyclic aromatic hydrocarbons bounded on particle fraction

Polycyclic aromatic hydrocarbons (PAHs) originate from a variety of natural and industrial processes. In this paper, concentrations of nine PAHs in PM10 particle fraction were measured concurrently at four different sites (rural, urban residential, urban traffic, and residential-industrial) in continental Croatia. Measurements at all of the four sites showed much higher average concentrations for all of the PAHs in the winter period. The highest winter average values were measured at the industrial site and the lowest at the rural and the urban residential site. In the summer, the highest average values were also measured in the industrial area, except for benzo(ghi)perylene and indeno(1,2,3-cd)pyrene, which showed the highest average values in the rural area. Factor analysis has been applied to PAH concentrations to identify their potential sources. Extracted factors have been interpreted on basis of previous studies and weather conditions. The diagnostic ratios calculated in this study indicated mixed sources at all of the sites. The contribution of gasoline and diesel from traffic was significant at all of the sites except for the urban industrial. In the winter, potential PAH sources also arose from wood combustion. The industrial site differed from the other sites with the highest influence of diesel sources and refinery during the summer months. The contribution of BaP in total carcinogenic activity exceeded 50 % in both seasons at all of the measured sites, which suggests that BaP could be suitable as a marker of the carcinogenic potential of a PAH mixture.

Burial effects of organic coatings on the heterogeneous reactivity of particle-borne benzo[a]pyrene (BaP) toward ozone

With an aerosol flow tube coupled to an Aerodyne aerosol mass spectrometer (AMS), room temperature (296 ± 3 K) kinetics studies have been performed on the reaction of gas-phase ozone with benzo[a]pyrene (BaP) adsorbed in submonolayer amounts to dry ammonium sulfate (AS) particles. Three organic substances, i.e., bis(2-ethylhexyl)sebacate (BES, liquid), phenylsiloxane oil (PSO, liquid), and eicosane (EC, solid), were used to coat BaP-AS particles to investigate the effects of such organic coatings on the heterogeneous reactivity of PAHs toward ozone. All the reactions of particle-borne BaP with excess ozone exhibit pseudo-first-order kinetics in terms of BaP loss, and reactions with a liquid organic coating proceed by the Langmuir-Hinshelwood (L-H) mechanism. Liquid organic coatings did not significantly affect the kinetics, consistent with the ability of reactants to rapidly diffuse through the organic coating. In contrast, the heterogeneous reactivity of BaP was reduced substantially by a thin (4-8 nm), solid EC coating and entirely suppressed by thick (10-80 nm) coatings, presumably because of slow diffusion through the organic layer. Although the heterogeneous reactivity of surface-bound PAHs is extremely rapid in the atmosphere, this work is the first to experimentally demonstrate a mechanism by which the lifetime of PAHs may be significantly prolonged, permitting them to undergo long-range transport to remote locations.

PAH mass concentrations measured in PM10 particle fraction

This paper presents daily, monthly and yearly variations of PAH mass concentrations measured in PM(10) particle fraction, collected at one measuring site in Zagreb air between 2001 and 2004, and seasonal differences in PAH mass concentrations in PM(10) samples collected from 21 March 2003 to 20 March 2004. Twenty-four hour samples were taken in the northern residential part of Zagreb using a low-volume (50 m(3)) sampler and glass or quartz filters. The analysis was performed using a high-performance liquid chromatograph (HPLC) and fluorescence detector with changeable excitation and emission wavelength. The annual average mass concentrations over the four-year measuring period for BaP ranged from 1.17 ng/m(3) in 2004 to 1.87 ng/m(3) in 2003 and were below the limit value (2 ng/m(3)) set by the Ordinance on Recommended and Limit Air Quality Values in Croatia. The highest concentrations of all PAHs measured in PM(10) samples collected from 21 March 2003 to 20 March 2004 were found in the winter and the lowest in the summer. Winter average of BaP was 2.94 ng/m(3) and summer average 0.12 ng/m(3). Autumn average was 2.76 ng/m(3) and was very similar to winter concentrations. Spring average of 0.58 ng/m(3) was higher than the summer average (0.12 ng/m(3)). Mass concentrations of all measured PAHs were much higher in the autumn than in the spring. Although annual averages for BaP did not exceed the limit value, autumn and winter BaP mass concentrations did, which calls for measures for reducing PAH emissions in the autumn and winter.

Personal exposures to PM(2.5) and polycyclic aromatic hydrocarbons and their relationship to environmental tobacco smoke at two locations in Greece

In the context of a large-scale molecular epidemiology study of biomarkers of genotoxicity of air pollution, 24-h mean personal exposures to airborne PM(2.5) (particulate matter <2.5 microm) and associated polycyclic aromatic hydrocarbon (PAHs) were measured in 194 non-smoking technical institute students living in the city of Athens, Greece (an area with moderately high levels of air pollution) and the nearby small town of Halkida anticipated to have lower pollution levels. Extensive information relevant to the assessment of long-term and recent exposure to PAH was obtained from questionnaires as well as a time-location-activity diary (TLAD) which was kept by all subjects during a 4-day observation period. During the last 24 h of this period, subjects underwent personal exposure monitoring for PM(2.5) and PAH, while a sample of blood was donated at the end of this period. All subjects were monitored in this way twice; once during a winter season (October-February) and once during the following summer season (June-September). Nine subjects with plasma cotinine levels above 20 ng/ml were considered as unreported smokers and excluded from the study. Winter PM(2.5) exposures were lower in Athens (geometric mean 39.7 microg/m(3)) than Halkida (geometric mean 56.2 microg/m(3)) (P<0.001), while there was no significant location difference during the summer (Athens: geometric mean 32.3 microg/m(3), Halkida: geometric mean 32.9 microg/m(3); P=0.79). On the other hand, PAH exposures (sum of the eight carcinogenic PAHs) were significantly higher in Athens than in Halkida during the winter (Athens: geometric mean 8.26 ng/m(3), Halkida: geometric mean 5.80 ng/m(3); P<0.001) as well as during the summer (Athens: geometric mean 4.44 ng/m(3), Halkida: geometric mean 1.48 ng/m(3); P<0.001). There was a significant difference in the profile of the PAH exposures at the two locations, the proportion of lighter PAH (benzo[a]anthracene, chrysene [CHRYS], benzo[k]fluoranthene, and benzo[b]fluoranthene) being higher, and that of heavier PAH (benzo[ghi]perylene [BPer] and indeno[1,2,3,cd]pyrene) lower, in Halkida than in Athens, regardless of season. This difference appeared to be related to individual exposure to environmental tobacco smoke (ETS), as indicated by (a) the correlation at the individual level between the CHRYS/BPer ratio and declared time of recent exposure to ETS as well as plasma cotinine levels, especially during the winter; (b) the parallel variation of the mean levels of all three markers (declared ETS exposure, cotinine levels, CHRYS/BPer ratio) among three subgroups of subjects (Athens subjects who had lowest levels of all three markers; Halkida subjects other than those living in the institute campus area; and Halkida subjects living in the institute campus area who had the highest levels of all three markers). This demonstrates that ETS can have a distinctive effect on the PAH exposure profile of subjects exposed to relatively low levels of urban air pollution.

The variation of street air levels of PAH and other mutagenic PAC in relation to regulations of traffic emissions and the impact of atmospheric processes

The occurrence of particle associated PAH and other mutagenic PAC was determined in 1996 in the street air of Copenhagen. In addition, particle extracts were tested for mutagenicity. The measurements were compared with previous measurements in 1992/1993. The levels had decreased in this period. The decrease was caused by an implementation of light diesel fuels for buses and the exchange of older petrol-driven passenger cars with catalyst-equipped new ones. About 65% of the reduction was caused by the application of the light diesel fuels. Under special conditions, chemical processes in the atmosphere produced many more mutagens than the direct emissions. The concentrations of S-PAC and N-PAC were 10 times lower than those of PAH, while the levels of oxy-PAH were in the same order of magnitude as those of PAH. Benzanthrone, an oxy-PAH, is proposed to be formed in the atmosphere in addition to direct emissions. Benzo(a)pyrene, often applied as an air quality criteria indicator, was photochemically degraded in the atmosphere. A strong increase in the mutagenic activities was observed to coincide with a depletion of benzo(a)pyrene.