ObjectivesThere has been little study on the effect of traffic-related air pollution on the incidence and persistence of asthma in preschool children. We evaluated the association of exposure to ...traffic-related air pollution with the incidence/persistence of asthma during the first 3 years of life using a population-based study.MethodsA baseline survey was conducted in 1½-year-old children (n=63 266). A follow-up survey at 3 years of age (n=43 343) identified new-onset asthma cases (n=853) and persistence of asthma (n=214). In the prevalence/persistence study, the outdoor concentrations of nitrogen oxides (NOx) and elemental carbon (EC) at home during the first 1½ years of life were estimated by a dispersion model. In the nested case–control study, which regarded incidence of asthma as cases, the personal exposure levels were estimated by dispersion model including time-activity pattern.ResultsThere was no statistically significant association between the incidence of asthma between age 1½ and 3 years and personal exposure levels to NOx nor EC. However, the persistence of asthmatic symptoms (between 1½ and 3 years) was significantly associated with outdoor concentrations of NOx. ORs for the persistence of asthmatic symptoms were 6.02 (95% CI 1.51 to 23.92) for the comparison between the upper 5th and lower 25th centiles of NOx.ConclusionsWhile no statistically significant association was observed for the incidence of asthma, the persistence of asthmatic symptoms in preschool children was significantly associated with traffic-related air pollution. This supports its importance as a risk factor in childhood airway disease.
The urban model inter-comparison study (UMICS) was conducted in order to improve the performance of air quality models (AQMs) for simulating fine particulate matter (PM
2.5
) in the Greater Tokyo ...Area of Japan. UMICS consists of three phases: the first phase focusing on elemental carbon (UMICS1), the second phase focusing on sulfate, nitrate and ammonium (UMICS2), and the third phase focusing on organic aerosol (OA) (UMICS 3). In UMICS2/3, all the participating AQMs were the Community Multiscale Air Quality modeling system (CMAQ) with different configurations, and they similarly overestimated PM
2.5
nitrate concentration and underestimated PM
2.5
OA concentration. Various sensitivity analyses on CMAQ configurations, emissions and boundary concentrations, and meteorological fields were conducted in order to seek pathways for improvement of PM
2.5
simulation. The sensitivity analyses revealed that PM
2.5
nitrate concentration was highly sensitive to emissions of ammonia (NH
3
) and dry deposition of nitric acid (HNO
3
) and NH
3
, and PM
2.5
OA concentration was highly sensitive to emissions of condensable organic compounds (COC). It was found that PM
2.5
simulation was substantially improved by using modified monthly profile of NH
3
emissions, larger dry deposition velocities of HNO
3
and NH
3
, and additionally estimated COC emissions. Moreover, variability in PM
2.5
simulation was estimated from the results of all the sensitivity analyses. The variabilities on CMAQ configurations, chemical inputs (emissions and boundary concentrations), and meteorological fields were 6.1–6.5, 9.7–10.9, and 10.3–12.3%, respectively.
The radiocarbon (14C) of total carbon (TC) in atmospheric fine particles was measured at 6 h or 12 h intervals at two sites, 50 and 100 km downwind from Tokyo, Japan (Kisai and Maebashi) in summer ...2007. The percent modern carbon (pMC) showed clear diurnal variations with minimums in the daytime. The mean pMC values at Maebashi were 28 ± 7 in the daytime and 45 ± 16 at night (37 ± 15 for the overall period). Those at Kisai were 26 ± 9 in the daytime and 44 ± 8 at night (37 ± 12 for the overall period). This data indicates that fossil sources were major contributors to the daytime TC, while fossil and modern sources had comparable contributions to nighttime TC in the suburban areas. At both sites, the concentration of fossil carbon as well as O3 and the estimated secondary organic carbon increased in the daytime. These results suggest that fossil sources around Tokyo contributed significantly to the high daytime concentration of secondary organic aerosols (SOA) at the two suburban sites. A comparison of pMC and the ratio of elemental carbon/TC from our particulate samples with those from three end-member sources corroborates the dominant role of fossil SOA in the daytime.
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IJS, KILJ, NUK, PNG, UL, UM
Suspended particulate matters (SPM) collected hourly at that time of Fukushima Dai-ichi Nuclear Plant accident in 2011 on a filter tape at many automated SPM monitoring stations located widely in ...eastern Japan was analyzed in order to determine atmospheric radiocesium concentration. Precise time series of
137
Cs concentrations in wide areas of eastern Japan were revealed. Analysis of radioactivity of SPM collected on filter tapes by automated SPM monitoring stations even at 1–2 years after the accident is concluded to give very valuable information to resolve the matter of radioactive contamination by Fukushima accident.
We analyzed the source–receptor relationships for particulate polycyclic aromatic hydrocarbon (PAH) concentrations in northeastern Asia using an aerosol chemical transport model. The model ...successfully simulated the observed concentrations. In Beijing (China) benzoapyren (BaP) concentrations are due to emissions from its own domain. In Noto, Oki and Tsushima (Japan), transboundary transport from northern China (>40°N, 40–60%) and central China (30–40°N, 10–40%) largely influences BaP concentrations from winter to spring, whereas the relative contribution from central China is dominant (90%) in Hedo. In the summer, the contribution from Japanese domestic sources increases (40–80%) at the 4 sites. Contributions from Japan and Russia are additional source of BaP over the northwestern Pacific Ocean in summer. The contribution rates for the concentrations from each domain are different among PAH species depending on their particulate phase oxidation rates. Reaction with O3 on particulate surfaces may be an important component of the PAH oxidation processes.
•Source–receptor analysis was conducted for investigating PAHs in northeast Asia.•In winter, transboundary transport from China is large contribution in leeward.•Relative contribution from Korea, Japan, and eastern Russia is increased in summer.•This seasonal variation is strongly controlled by the meteorological conditions.•The transport distance is different among PAH species.
Transboundary transport of PAHs in northeast Asia was investigated by source–receptor analysis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We estimated the contributions of source regions in East Asia to PM2.5 mass concentrations over Japan for the year 2010 using a regional chemical transport model with an emission sensitivity ...approach. The horizontal distributions and temporal variations of PM2.5 concentrations were generally well reproduced by the model. The relative contribution of China to the annual mean PM2.5 concentration was estimated to be 50–60% in western Japan (from Kyushu to Kinki), and 40% in the Kanto area. Central north China (105°E–124°E, 34°N–42°N) made a particularly significant contribution, accounting for 20–40% of the annual mean PM2.5 concentration for the whole of Japan. The contribution from foreign sources increased in spring, autumn, and winter in western Japan, and in spring in the Kanto area. The domestic contribution was estimated to be 20–50%. The sum of contributions from foreign anthropogenic sources was greater than the domestic pollution in each receptor region except the Kanto region. The results were obtained from sensitivity simulations with reduced anthropogenic emissions from each source region by 20%. The uncertainties in the source-receptor relationship for annual mean PM2.5 concentrations were estimated to be within a few percent, from additional sensitivity simulations with different perturbations (a 20% increase and a 50% reduction). The model results suggest that regional-scale transport in East Asia has a significant impact on the attainment of the PM2.5 environmental standard in Japan.
The climatology of surface ozone over East Asia was investigated at a wide range of latitudes by integrating continuous measurements from Japanese monitoring networks. Although a spring maximum and a ...summer minimum were observed at all seven remote stations, significant latitudinal differences in the seasonal cycles were found, particularly in spring. At low latitudes (20–30°N) the spring maximum appears in March, while it appears in April at high latitudes (40–50°N), and in May at middle latitudes (30–40°N). A regional‐scale chemical transport model was applied to examine factors contributing to the latitudinal dependence observed. The model reproduces the latitudinal gradient and the overall seasonal variations well, and suggests that transport patterns of Asian continental outflow coupled with photochemistry result in latitudinal inhomogeneity over East Asia. These results highlight the key role of dynamical processes in modulating the amplitude and phase of the spring maximum in surface ozone.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
We conducted continuous measurements of NOy and total nitrate (T.NO3 = HNO3 + NO3−(p)) at Fukue Island, Nagasaki, and Cape Hedo, Okinawa, Japan. We compared variations of NOy or T.NO3 concentrations ...measured at two remote sites when the air masses were originated from the same regions of the Asian Continent. Long-range transport events from the Asian Continent were extracted by CO concentration peaks at Fukue and Hedo and backward trajectory analyses. We compared the transport time difference at two sites from the Asian continent with the ratios of NOy at Hedo to that at Fukue (=R(NOy)) to find the predominant factor in NOy removal. R(NOy) were less than unity and decreased with the transport time difference. The ratios of NOy/CO at Hedo to those at Fukue (R(NOy/CO)) was assumed to be affected by the deposition process. R(NOy/CO) showed negative correlation with transport time difference as the same the case of R(NOy). This indicates that NOy was mainly removed by deposition rather than dilution. Air mass ages were classified by the ratio of T.NO3 to NOy at Fukue: T.NO3/NOy < 0.2 was fresh air, 0.2–0.4 was middle-aged, and greater than 0.4 was aged. The ratios of T.NO3/NOy at Hedo to those at Fukue (R(T.NO3/NOy)) in the fresh air mass were greater than unity. In contrast, R(T.NO3/NOy) values in the aged air mass were unity and were less correlated with transport time difference. This indicates that T.NO3 generation proceeded in fresh air mass. On the other hand, T.NO3 generation rate was comparable to removal rate in the aged air mass. According to the relationship between R(NOy/CO) and transport time difference, the removal rate constant and NOy lifetime were (1.24 ± 0.33) × 10−5 s−1 and 18–31 h, respectively.
•Total odd nitrogen species and total nitrate were measured at two remote sites.•NOy and T.NO3/NOy were compared to show variation during transport.•Decreasing NOy during transport was dominated by dry and wet deposition.•T.NO3/NOy ratio variations depended on air mass age.•NOy removal rate was calculated by comparing transport time and NOy variation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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