Metropolitan Area Of Japan Research Articles

Social capital and local public transportation in Japan

Local public transportation except in metropolitan areas in Japan faces operating difficulties due to business deficits. In recent years, central and local governments have taken social benefits into account to support local public transportation, but social benefits calculated in their cost-benefit analyses seem to be insufficient to evaluate them. Especially since the great earthquake in 2011, Japanese people have begun to rethink the importance of network and trust in neighborhoods, which can be called as ‘social capital,’ based on mobility. Therefore, focusing on ‘social capital,’ this paper tries to find the role of local public transportation beyond social benefits. Specifically, it makes an empirical analysis on the relationship between the indexes of ‘social capital’ and local bus services using cross section data. As a result, network and participation indexes standing for ‘social capital’ in each prefecture positively correlate with the level of local bus services. Also, according to our survey research in Toyama, introduction of a new LRT line is likely to have considerably changed the activities of residents along the line and has tended to promote more opportunities to come into contact with others than before. Those studies shed light on the role of public transportation from the standpoint of ‘social capital.’

A cross-sectional survey of policies guiding second stage labor in urban Japanese hospitals, clinics and midwifery birth centers.

BackgroundThe Japan Academy of Midwifery developed and disseminated the ‘2012 Evidence-based Guidelines for Midwifery Care (Guidelines for Midwives)’ for low-risk births to achieve a more uniform standard of care during childbirth in Japan. The objective of this study was to cross-sectional survey policy implementation regarding care during the second stage of labor at Japanese hospitals, clinics, and midwifery birth centers, and to compare those policies with the recommendations in Guidelines for Midwives.MethodsThis study was conducted in the four major urbanized areas (e.g. Tokyo) of the Kanto region of Japan. Respondents were chiefs of the institutions (obstetricians/midwives), nurse administrators (including midwives) of the obstetrical departments, or other nurse/midwives who were well versed in the routine care of the targeted institutions. The Guidelines implementation questionnaire comprised 12 items. Data was collected from October 2010 to July 2011.ResultsThe overall response was 255 of the 684 institutions (37 %). Of the total responses 46 % were hospitals, 26 % were clinics and 28 % were midwifery birth centers. Few institutions reported perineal massage education for ‘almost all cases’. Using ‘active birth’ were all midwifery birth centers, 56 % hospitals and 32 % clinics. Few institutions used water births. The majority of hospitals (73 %) and clinics (80 %) but a minority (39 %) of midwifery birth centers reported ‘not implemented’ about applying warm compress to the perineum. Few midwifery birth centers (10 %) and more hospitals (38 %) and clinics (50 %) had a policy for valsalva as routine care. Many hospitals (90 %) and clinics (88 %) and fewer midwifery birth centers (54 %) offered hands-on technique to provide perineal support during birth. A majority of institutions used antiseptic solution for perineal disinfection. Few institutions routinely used episiotomies for multiparas, however routine use for primiparas was slightly more in hospitals (21 %) and clinics (25 %). All respondents used fundal pressure as consistent with guidelines. Not many institutions implemented the hands and knees position for correcting fetal abnormal rotation.ConclusionsThis survey has provided new information about the policies instituted in three types of institutions guiding second stage labor in four metropolitan areas of Japan. There existed considerable differences among institutions’ practice. There were also many gaps between reported policies and evidence-based Guidelines for Midwives, therefore new strategies are needed in Japan to realign institution’s care policies with evidenced based guidelines.

Effect of Urbanization on the Urban Heat Island in Fukuoka-Kitakyushu Metropolitan Area, Japan

In the coastal cities, the use of the sea breeze to mitigate the urban heat island phenomenon has attracted attention. To accumulate data for the urban climate in the Fukuoka-Kitakyushu metropolitan area, the fourth largest metropolitan area in Japan and located in coastal area, numerical simulations with a meso-scale meteorological model, the Weather Research and Forecast model (WRF), and upper air observation with Doppler LIDAR were carried out in the summer of 2015, simultaneously. The results of this study suggested that the urbanization process weakened sea breeze penetration.

Virological characteristics of hepatitis B genotype G/A2 recombination virus in Japan.

We identified four cases of infection with hepatitis B virus genotype G and A2 recombinant (HBV/G/A2) strains, which were initially overlooked by enzyme immunoassay-based genotyping. The patients were all men who have sex with men (MSM) and inhabited several metropolitan areas of Japan, suggesting that the recombinant strains may be circulating among high-risk groups such as MSM. Here, we investigated the genomic structure and virological properties of the HBV/G/A2 strains. Complete genome sequences of the isolates were determined and phylogenetically analyzed. Replication efficiency of HBV/G/A2 was investigated by transfecting plasmids containing 1.24-fold viral genome. The in vivo viral kinetics of HBV/G/A2 were investigated using chimeric mice with humanized livers. Phylogenetic analysis revealed that the four strains were almost identical (>99.7% homologous). The preS2/S region of these strains was highly homologous to that of genotype A2 and the remaining region was almost identical to that of genotype G, reflecting inter-genotypic recombination. Interestingly, in all four cases, genotype A was co-infected as a minor population. In vitro analysis revealed that HBV/G/A2 had a low replication rate. Although detectable viremia was not measurable following the inoculation of HBV/G/A2 into chimeric mice, subsequent superinfection of HBV genotype A greatly enhanced HBV/G/A2 replication and viral spread. We found that four cases of HBV/G/A2 recombinant among MSM patients in the metropolitan areas of Japan, and HBV/A co-infections are required for its efficient replication. High-risk groups such as MSM should be carefully tested for infection of genotype G-derived variants.

Microclimate is an independent risk factor for the development of intraoperatively acquired pressure ulcers in the park-bench position: A prospective observational study.

Preventing pressure ulcers is important in patients undergoing procedures in the park-bench position. We hypothesized that the microclimate around the skin is a significant risk factor for developing pressure ulcers. This research continuously assessed factors of the microclimate in terms of skin temperature and perspiration as well as the interface pressure in order to determine whether the microclimate is an independent risk factor for the development of park-bench position-related pressure ulcers (PBP-PUs). A prospective observational study was conducted among patients undergoing elective surgery in the park-bench position at a general hospital in the metropolitan area of Japan between April and November 2014. Factors of the microclimate, including skin temperature and perspiration, in addition to the interface pressure were continuously measured throughout surgery. Twenty-nine patients were analyzed (mean age 44.4 ± 13.2 years, male 44.8%). Of these 29 patients, seven (24.1%) developed Category I PBP-PUs. The change in skin temperature from baseline to the end of surgery (2.7 ± 0.3 °C vs. 1.9 ± 0.8 °C) and the average peak pressure (119.1 ± 36.8 mmHg vs. 94.5 ± 23.1 mmHg) were significantly higher in the patients with PBP-PUs than in those without PBP-PUs. There were no significant differences in the amount of perspiration between the two groups. A hierarchical logistic regression analysis showed that the change in skin temperature was significantly related to the development of PBP-PUs (unit = 0.1 °C: odds ratio 1.44, 95% confidential interval 1.09-2.33) when adjusted for the average peak pressure and length of surgery. Our results suggest that a change in skin temperature toward a higher value is an independent risk factor for the development of PBP-PUs. Proper intraoperative management of skin temperature may therefore be a promising candidate as a preventive method against PBP-PU development.

Shifting hepatitis B virus genotypes of acute hepatitis B patients in northeast Japan.

It has been reported that acute hepatitis B (AHB) patients with genotype A HBV (HBV/A) have been increasing since the 1990s in metropolitan areas in Japan. However, little is known about the trends of HBV genotypes in AHB patients in northeast Japan where genotype B HBV (HBV/B) prevails more than in other areas. In this study, we aimed to clarify the changes in the HBV genotypes and clinical characteristics of AHB patients in this area. HBV genotypes were determined by direct sequencing (n = 125) or enzyme immunoassay (n = 9) using serum samples from AHB patients including fulminant hepatitis in 1987-2014. Among 134 patients, 26 (19%), 33 (25%), and 75 (56%) patients were infected with HBV of genotypes A, B, and C, respectively. HBV/A emerged from 2001 and the percentage was increased gradually up to 48% in 2010-2014, whereas HBV/B was reduced from 40% in 1987-1994 to 10% in 2010-2014. Phylogenetic analysis showed that three major subgenotype A2 strains had come into this area serially. The levels of HBV DNA and prothrombin time were higher in HBV/A patients than other genotypes. This study could not show significant difference in the HBsAg-positive period among genotypes nor the effect of nucleoside analogues to shorten the HBsAg-positive period. A higher level of initial HBV DNA was associated with late disappearance of HBsAg. In conclusion, the percentage of HBV/A in AHB patients has been increasing in northeast Japan since 2001, which is later than metropolitan areas, whereas that of HBV/B is decreasing.

Estimate of biogenic VOC emissions in Japan and their effects on photochemical formation of ambient ozone and secondary organic aerosol

A new gridded database has been developed to estimate the amount of isoprene, monoterpene, and sesquiterpene emitted from all the broadleaf and coniferous trees in Japan with the Model of Emissions of Gases and Aerosols from Nature (MEGAN). This database reflects the vegetation specific to Japan more accurately than existing ones. It estimates much lower isoprene emitted from other vegetation than trees, and higher sesquiterpene emissions mainly emitted from Cryptomeria japonica, which is the most abundant plant type in Japan. Changes in biogenic emissions result in the decrease in ambient ozone and increase in organic aerosol simulated by the air quality simulation over the Tokyo Metropolitan Area in Japan. Although newly estimated biogenic emissions contribute to a better model performance on overestimated ozone and underestimated organic aerosol, they are not a single solution to solve problems associated with the air quality simulation.

Influence of contemporary carbon originating from the 2003 Siberian forest fire on organic carbon in PM2.5 in Nagoya, Japan

In May 2003, high concentrations of organic carbon (OC) in PM2.5 were measured in Nagoya, a representative metropolitan area in Japan. To investigate the influence of possible forest fires on PM2.5 in Japan via long-range aerosol transport, the radiocarbon (14C) concentrations of PM2.5 samples from April 2003 to March 2004 were measured. 14C concentrations in total carbon (TC) from May to early June showed higher values than those in other periods. The OC/elemental carbon (EC) ratios from May to early June were also significantly higher than the ones in other periods. In addition, OC concentrations from May to early June were typically high. These results indicate that the abundant OC fraction from May to early June in Nagoya consisted predominantly of contemporary carbon. Furthermore, simulations of diffusion and transport of organic matter (OM) in East Asia showed that abundant OM originating from East Siberia spread over East Asia and Japan in May and early June. Backward air mass trajectories from this time frame indicate that the air mass in Nagoya likely first passed through East Siberia where fire events were prevalent. However, the backward trajectories showed that the air mass after early June did not originate mainly from Siberia, and correspondingly, the 14C and OC concentrations showed lower values than those from May to early June. Therefore, the authors conclude that contemporary carbon originating from the forest fire in East Siberia was transported to Nagoya, where it significantly contributed to the high observed concentrations of both OC and 14C.

A Comparative Analysis on the Population Re-centralization of Metropolitan Areas in Japan's Prefectural Capitals

A Comparative Analysis on the Population Re-centralization of Metropolitan Areas in Japan's Prefectural Capitals

大都市圏における駅勢圏の空間的構造

This study reveals the spatial structure of railroad station areas that are smaller than municipal divisions. A town is regarded as the areas around a station. The scale of a town is measured by the number of passengers that go in and out of the station. The chain of railroad station areas from the terminal station, the largest station in the area, in the metropolis to the suburb creates an urban area. There are two types of the above chains in metropolitan areas of Japan. In one the station nearest the terminal station is small and the second largest station is far from the terminal station. In the other the second largest station is located next to the terminal station and other stations become gradually smaller as they move away from the terminal station. This study can contribute to plans for the development of station areas in a metropolitan area as it elucidates the mechanisms of the spatial structure in the urban area. In the main body, a town is regarded as the circular railroad station area to simplify the model. Then the rank-size and gravity models were applied to perform a simulation analysis to understand how gaps in the size of stations in the metropolitan area, the number of stations, and the traffic conditions affect the relative interactions based on the relationships between stations nearest to the terminal station and the terminal station itself. As a result, the relative interactions showed that the distance between the terminal station and the next station is greater when the number of stations is small, the gap between the size of stations is small, and the size of the terminal station in the metropolitan area is large. The above model was applied to a railroad route in the metropolitan area of the Kanto region using a discriminant analysis. The results were partially similar to the simulation analysis. JEL Classification: R12, R40

Assessing dynamic externalities from a cluster perspective: the case of the motor metropolis in Japan

In this paper, we first apply the methods of exploratory spatial data analysis and investigate the geographical concentration of interrelated growing industries, or “growth clusters,” by using data from the Nagoya metropolitan area in Japan over the period 1986–2006. Second, by applying econometric models, we examine whether and which type of knowledge externalities contribute to region-industry dynamics and to the formation of the detected growth cluster. As a methodological contribution, following Porter’s (Reg Stud 37:549–578, 2003) widely recognized cluster concept, we incorporate spatial dependence caused by the geographical proximity between regions and the technological proximity between industries into the empirical models. Combining the information obtained from the ESDA and econometric analysis enables us to assess the role of knowledge externalities for regional growth from a cluster perspective. The empirical results identify the presence of a growth cluster mainly driven by the automobile and associated industries. The core of the cluster is made up of manufacturing industries, but also includes several service sectors. The periphery of the cluster has less variety, mainly including the transportation equipment and electrical machinery industries. We find that intra-industry externalities that diffuse over a broader area within the cluster help the steady growth of the transportation equipment industry. In the core of the cluster, the diversified interrelated structure also contributes to the growth of the auto-related manufacturing sectors.

Creation of Residential Land Price Maps for the Three Metropolitan Areas in Japan

Creation of Residential Land Price Maps for the Three Metropolitan Areas in Japan

GIS-Based Urbanization Prediction Model Considering Neighborhood Relationship of the Unit of the “Block” in the Outskirts of Metropolitan Area

On the outskirts of the metropolitan areas in Japan, the rapid development of urban areas and the improvement in transportation networks have brought various land use problems in their wake, including urban diffusion and the phenomenon of urban sprawl. There is a strong need for accurate predictions of land-use change and future urbanization, as well as investigation of the appropriateness of present land use controls and the land use controls that will be required in the future. This study took as its object the outskirts of the Keihanshin (Kyoto-Osaka-Kobe) Metropolitan Area, the second largest conurbation in Japan after the Tokyo Metropolitan Area, and used the digital maps and spatial analysis offered by GIS. It aimed to: 1) describe the characteristics of land use controls, land use and urbanization; 2) develop an urbanization prediction model that considers the neighboring relationship of neighboring areas on a 100 m mesh unit; 3) apply this model to the study area and verify its validity regarding the conditions of present land use; 4) compare urbanization prediction results by this model with the present land use controls; and 5) make predictions for future urbanization and propose remedial measures for future land use controls.

Significance of Imbalance in the Ratio of Serum n-3 to n-6 Polyunsaturated Fatty Acids in Patients With Acute Coronary Syndrome

This study aimed to assess the balance of serum n-3 to n-6 polyunsaturated fatty acids (PUFAs) in patients with acute coronary syndrome (ACS). We enrolled 1,119 patients who were treated and in whom serum PUFA level was evaluated in 5 divisions of cardiology in a metropolitan area in Japan. Serum levels of PUFAs, including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (AA), were compared between patients with and without ACS. We also evaluated the balance of serum n-3 to n-6 PUFAs, including EPA/AA and DHA/AA ratios. EPA/AA values were 0.46 ± 0.32 and 0.50 ± 0.32 in the ACS and non-ACS groups, respectively. DHA/AA values were 0.95 ± 0.37 and 0.96 ± 0.41 in the ACS and non-ACS groups, respectively. Next, we divided the patients into 3 groups based on the tertiles of EPA/AA or tertiles of DHA/AA to determine the independent risk factors for ACS. According to multivariate logistic regression analysis, the group with the lowest EPA/AA (≤0.33) had a greater probability of ACS (odds ratio 3.14, 95% confidence interval 1.16 to 8.49), but this was not true for DHA/AA. In conclusion, an imbalance in the ratio of serum EPA to AA, but not in the ratio of DHA to AA, was significantly associated with ACS.

Abstract C17: Cigarette smoke inhalation and lung cancer risk: Case-control study in Japan

Abstract Background: Cigarette smoking is a major cause of lung cancer (LC). Several studies have demonstrated that extent of cigarette smoke inhalation is associated with the risk of LC in European population. However, to date, there are few such studies in Asian populations. The aim of our study is to clarify the relationship between cigarette smoke inhalation and the risk of LC in Japanese population. Methods: We have conducted a case-control study of cigarette smoking and lung cancer (LC) risk in Aichi Prefecture, the third largest metropolitan area in Japan. Between 1993 and 1998, several hospitals in Aichi prefecture recruited newly diagnosed incident patients with histologically confirmed LC (n=653). The case eligibility included an age of 20–81 years, no previous diagnosis of lung, or other cancer, and ability to participate and provide informed consent. The study included both hospital controls (HC: n=453) and community-based controls (CC: n=828). The eligibility criteria of the two control groups were the same as for cases except that the hospital controls were admitted for non-malignant diseases or conditions unrelated to cigarette smoking. Odds ratios (OR) and 95% confidence intervals (CI) were derived from unconditional logistic regression analysis, adjusted for basic confounding variables such as age, sex, drinking status, family history of LC, occupation (white collar or blue collar), and years of education (less than 12 years, 12 or more than 12years). Results: The mean of age was 60.7 in cases, 60.1 in controls. Cases had a higher proportion of male, having family history of LC, heavy drinker, and current smoker. The most common histologic types of LC were adenocarcinoma (AD) (50.9%), squamous cell carcinoma (SQ) (22.1%) and small cell carcinoma (SM) (19.2%). Compared to ever smokers in controls, those in cases started smoking at younger age, smoked more cigarettes per day and longer duration. The proportion of smokers who inhale cigarette smoke was greater in cases. The risk of LC in ever smokers was significantly higher than never smokers, especially in smokers who inhale cigarette smoke. Compared with never smokers, ORs for ever smokers who do not inhale cigarette smoke (inhale-no) and ever smokers who inhale cigarette smoke (inhale-yes) were 1.72(95%CI: 1.15-2.59), 3.28(95%CI: 2.38-4.53), when adjusted for basic confounding variables. Stratified analyses by histologic types of LC showed that these associations were quite strong in SQ and SM (inhale-no: OR 10.1(95%CI: 4.96-20.7), inhale-yes: OR 19.7(95%CI: 10.3-37.6)) On the other hand, such associations seemed to be mild in AD (inhale-no: OR 0.87(95%CI: 0.51-1.48), inhale-yes: OR 1.50(95%CI: 1.01-2.21)). Stratified analysis by pack-year showed that OR of “inhale-yes” group was higher than “inhale-no” group in every categories of pack-year (<20, 20-39, 40-59, 60 or more). When the analysis was restricted to ever smokers, the OR (adjusted for basic confounding factors and pack-year) of LC risk in ever smokers who inhale cigarette smoke was significantly higher than who do not inhale cigarette smoke. OR for “inhale-yes” group compared with “inhale-no” group was 1.52(95%CI: 1.06-2.18, p=0.021). No heterogeneity was observed across histologic types of LC. Conclusion: Our case- control study demonstrated that inhalation of cigarette smoke is an independent risk for LC even in the adjustment for pack-year in Japanese population. Cigarette smoke inhalation might have an additive effect toward LC risk. Citation Format: Koichi Fukumoto, Hidemi Ito, Chiyoung Park, Hideo Tanaka, Keitaro Matsuo, Kazuo Tajima, Toshiro Takezaki. Cigarette smoke inhalation and lung cancer risk: Case-control study in Japan. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr C17.

Trends of Second‐Line Eradication Therapy forHelicobacter pyloriin Japan: A Multicenter Study in the Tokyo Metropolitan Area

In Japan, the eradication rate of first-line therapy for Helicobacter pylori (H.pylori) with a proton pump inhibitor (PPI), amoxicillin (AMPC) and clarithromycin (CAM) has been decreasing because of a high prevalence of CAM resistance. A possible decrease of the eradication rate for second-line therapy with a PPI, AMPC and metronidazole (MNZ) is of concern. The aim of this study is to assess the trends in second-line eradication therapy for H.pylori in Japan. We accumulated data retrospectively on patients administered second-line eradication therapy for Helicobacter pylori with a PPI, AMPC, and MNZ for 1 week after failure of first-line eradication therapy with a PPI, AMPC and CAM at 15 facilities in the Tokyo metropolitan area in Japan from 2007 to 2011. Trends for second-line eradication rates in modified intention-to-treat (ITT) analyses were investigated. Second-line eradication rates were categorized by three PPIs (rabeprazole (RPZ), lansoprazole (LPZ) or omeprazole (OMZ)) and evaluated. We accumulated data on 1373 patients. The overall second-line eradication rate was 92.4%. Second-line eradication rates in 2007, 2008, 2009, 2010 and 2011 were 97.7, 90.6, 94.5, 91.8 and 91.8%, respectively, with no significant trends revealed. Second-line eradication rates categorized by three PPIs for the entire 5-year period were 91.6, 93.4 and 92.4% (RPZ, LPZ and OPZ, respectively) with no significant differences among the three PPIs. From 2007 to 2011, there were no significant trends in the second-line eradication rates and the rates remained consistently high. From the viewpoint of high prevalence of CAM resistance in Japan, triple therapy with PPI, AMPC and MNZ may be a better strategy for first-line therapy compared to triple therapy with PPI, AMPC and CAM.

Determining optimal resource recycling boundary at regional level: A case study on Tokyo Metropolitan Area in Japan

Conventionally, material inputs to industries come from either natural resources or intermediate products. With the increasing attention on greening the industrial process, municipal solid waste (MSW) can be separated and utilized as inputs to large-scale industries. As such, waste flows need to be managed to meet the requirements of industries by considering both quality and scale. Small scales of municipal recycling centers (MRCs) for pre-treating recyclable wastes often lead to higher pre-treatment cost and lower recycling efficiencies. Theoretically, appropriate facility scale and recycling boundary should be based upon a balanced consideration between economies of scale and transportation costs. However, only a few empirical studies on recycling boundaries have been conducted. Existing modeling studies are mostly case studies for planning purposes and do not theoretically examine the mechanisms and factors that determine recycling boundary. Under such a circumstance, this paper fills such a gap by quantitatively seeking the determinants for recycling boundaries and the related mechanism. An optimization model applying on the recycling of waste plastics is developed and tested in the Tokyo Metropolitan Region (TMR) in Japan. The results indicate two determinants for recycling boundary at the regional level: spatial density of separated wastes and the ratio of unit transportation cost to unit treatment cost. Separated wastes that are collected in low spatial density and have a low ratio of unit transportation cost to unit treatment cost should be better recycled in a large region. The finding implies that regional recycling networks should have multiple layers designed for different types of wastes due to the differences in their spatial density, unit transportation cost and unit treatment cost.

Mode choice models' ability to express intention to change travel behaviour considering non-compensatory rules and latent variables

Disaggregate behaviour choice models have been improved in many aspects, but they are rarely evaluated from the viewpoint of their ability to express intention to change travel behaviour. This study compared various models, including objective and latent models and compensatory and non-compensatory decision-making models. Latent models contain latent factors calculated using the LISREL (linear structural relations) model. Non-compensatory models are based on a lexicographic-semiorder heuristic. This paper proposes ‘probability increment’ and ‘joint probability increment’ as indicators for evaluating the ability of these models to express intention to change travel behaviour. The application to commuting travel data in the Chukyo metropolitan area in Japan showed that the appropriate non-compensatory and latent models outperform other models.

Does the installation of blue lights on train platforms prevent suicide? A before-and-after observational study from Japan

BackgroundRailway and metro suicides constitute a major problem in many parts of the world. Japan has experienced an increase in the number of suicides by persons diving in front of an oncoming train in the last several years. Some major railway operators in Japan have begun installing blue light-emitting-diode (LED) lamps on railway platforms and at railway crossings as a method of deterring suicides, which is less costly than installing platform screen doors. However, the effectiveness of the blue lights in this regard has not yet been proven. MethodsThis study evaluates the effect of blue lights on the number of suicides at 71 train stations by using panel data between 2000 and 2010 from a railway company in a metropolitan area of Japan. We use a regression model and compare the number of suicides before and after and with and without the intervention by the blue light. We used the number of suicides at 11 stations with the intervention as the treatment group and at the other 60 stations without the intervention as the control group. ResultsOur regression analysis shows that the introduction of blue lights resulted in a 84% decrease in the number of suicides (CI: 14–97%). LimitationThe analysis relies on data from a single railroad company and it does not examine the underlying suicide-mitigation mechanism of blue lights. ConclusionAs blue lights are easier and less expensive to install than platform screen doors, they can be a cost-effective method for suicide prevention.

Seasonal differences of the atmospheric particle size distribution in a metropolitan area in Japan

We compared the effect of ambient temperature observed in two different seasons on the size distribution and particle number concentration (PNC) as a function of distance (up to ~250m) from a major traffic road (25% of the vehicles are heavy-duty diesel vehicles). The modal particle diameter was found between 10 and 30nm at the roadside in the winter. However, there was no peak for this size range in the summer, even at the roadside. Ambient temperature affects both the atmospheric dilution ratio (DR) and the evaporation rate of particles, thus it affects the decay rate of PNC. We corrected the DR effect in order to focus on the effect of particle evaporation on PNC decay. The decay rate of PNC with DR was found to depend on the season and particle diameter. During the winter, the decay rate for smaller particles (<30nm) was much higher (i.e., the concentration decreased significantly against DR), whereas it was low during the summer. In contrast, for particles >30nm in diameter, the decay rate was nearly the same during both seasons. This distinction between particles less than or greater than 30nm in diameter reflects differences in particle volatility properties. Mass-transfer theory was used to estimate evaporation rates of C20–C36 n-alkane particles, which are the major n-alkanes in diesel exhaust particles. The C20–C28 n-alkanes of 30-nm particles completely evaporate at 31.2°C (summer), and their lifetime is shorter than the transport time of air masses in our region of interest. Absence of the peak at 10–30nm and the low decay rate of PNC <30nm in diameter in the summer were likely due to the evaporation of compounds of similar volatilities comparable to the C20–C36 n-alkanes from particles near the exhaust pipes of vehicles, and complete evaporation of semivolatile materials before they reached the roadside. These results suggest that the lifetime of particles <30nm in diameter depends on the ambient temperature, which differs between seasons. This leads us to conclude that these particles show distinctly different spatial distributions depending on the season.