Subway Cabin Research Articles

Unacknowledged health costs of subway transportation: Commuting time dominant environmental inequality in PM2.5 exposure

IntroductionThe subway network offers economical and swift transportation for long-distance commuters, simultaneously mitigating urban congestion and environmental challenges in sprawling metropolises. Nonetheless, studies have revealed that subway represent a microenvironment with heightened exposure to fine particulate matter (PM2.5), a facet of air pollution overlooked by the majority of commuters. Focusing on the case of Beijing's subway commuters, we assess the health and economic impact of personal exposure to PM2.5 during their commuting, as well as the distributional effects of these impacts across subgroups of populations with different daily commuting durations. MethodThis study adopts an integrated process to estimate the health outcomes and associated economic loss caused by subway commutes under different exposure scenarios. The overall daily exposure was estimated by aggregating exposure in different microenvironments using the microenvironmental exposure model. The health impact was then evaluated using the integrated exposure-response (IER) model. The economic value of the health impact was assessed based on the value of statistical life (VSL) of the affected population. ResultOur findings indicate that subway commutes lead to an increase of 11.6% and 26.3% in health damage and corresponding economic loss attributable to PM2.5 exposure through “crowding out” of exposure duration in relatively “cleaner” microenvironments in 2017 and 2020, respectively. Long-distance commuters who travel over 100 min per day, make up 25% of subway commuters and are disproportionately responsible for 40% of the total health damages and economic losses caused by subway PM2.5 exposure. Reducing PM2.5 concentration in subway cabins can more effectively offset the additional impacts brought about by the extended and rather inelastic subway commuting. ConclusionThe result unearthed by our study advocates for urgent measures to ameliorate the air quality within subway systems, a move that promises to mitigate the unequal burdens and rectify the inequities borne by at-risk demographics.

Reducing Virus Transmission from Heating, Ventilation, and Air Conditioning Systems of Urban Subways.

Aerosols carrying the virus inside enclosed spaces is an important mode of transmission for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as supported by growing evidence. Urban subways are one of the most frequented enclosed spaces. The subway is a utilitarian and low-cost transit system in modern society. However, studies are yet to demonstrate patterns of viral transmission in subway heating, ventilation, and air conditioning (HVAC) systems. To fill this gap, we performed a computational investigation of the airflow (and associated aerosol transmission) in an urban subway cabin equipped with an HVAC system. We employed a transport equation for aerosol concentration, which was added to the basic buoyant solver to resolve the aerosol transmission inside the subway cabin. This was achieved by considering the thermal, turbulent, and induced ventilation flow effects. Using the probability of encountering aerosols on sampling surfaces crossing the passenger breathing zones, we detected the highest infection risk zones inside the urban subway under different settings. We proposed a novel HVAC system that can impede aerosol spread, both vertically and horizontally, inside the cabin. In the conventional model, the maximum probability of encountering aerosols from the breathing of infected individuals near the fresh-air ducts was equal to 51.2%. This decreased to 3.5% in the proposed HVAC model. Overall, using the proposed HVAC system for urban subways led to a decrease in the mean value of the probability of encountering the aerosol by approximately 84% compared with that of the conventional system.

공기질 개선장치 가동에 따른 도시철도 차량 내 미세먼지 농도 변화에 대한 수치해석 연구

도시철도 차량 객실의 미세먼지 저감을 위해 공기질 개선장치가 설치되고 있으나 가동 조건에 따른 미세먼지 농도저감 특성 관련 연구는 부족하다. 따라서 현재 운영되고 있는 공기질 개선장치의 정화 수준을 검토하고자 공기질 개선장치와 냉난방 환기시스템(HVAC) 가동 조건에서의 객실 내 기류 특성과 시간에 따른 미세먼지 농도 변화를 수치해석을 통해 분석하였다. HVAC(3,180 m3/h)과 배출팬(990 ㎥/h) 가동 시 외부에서 100 μg/㎥ 농도의 미세먼지가 유입될 경우, 공기질 개선장치가 가동되더라도 시간이 지남에 따라 정화 속도가 느려지는 것을 확인하였다. 또한 외부 미세먼지 유입 조건에서 48명의 착석 승객 외에 60명의 입석 승객이 존재할 경우 객실 하부의 공기 순환이 원활하지 않으며, 미세먼지 농도 개선이 둔화되는 것으로 나타났다. 따라서 승객이 밀집한 객실의 신속한 오염물질 정화를 위해서는 객실 전체 공기순환 시간을 단축시키고, 터널로부터 미세먼지가 유입되는 것을 최소화하는 것이 중요할 것으로 보인다.

Prediction of Individual Dynamic Thermal Sensation in Subway Commute Using Smart Face Mask

Wearable sensors and machine learning algorithms are widely used for predicting an individual's thermal sensation. However, most of the studies are limited to controlled laboratory experiments with inconvenient wearable sensors without considering the dynamic behavior of ambient conditions. In this study, we focused on predicting individual dynamic thermal sensation based on physiological and psychological data. We designed a smart face mask that can measure skin temperature (SKT) and exhaled breath temperature (EBT) and is powered by a rechargeable battery. Real-time human experiments were performed in a subway cabin with twenty male students under natural conditions. The data were collected using a smartphone application, and we created features using the wavelet decomposition technique. The bagged tree algorithm was selected to train the individual model, which showed an overall accuracy and f-1 score of 98.14% and 96.33%, respectively. An individual's thermal sensation was significantly correlated with SKT, EBT, and associated features.

Study on the Ventilation Method to Maintain the PM10 Concentration in a Subway Cabin below 35 μg/m3.

The city of Seoul will limit the maximum particulate matter (PM10) concentration to ≤35 μg/m3 (from 2024). Herein, a numerical parametric study was conducted on the PM removal efficiency of the heating, ventilation, and air conditioning (HVAC) filters installed in the ceiling of subway cabins. The PM10 concentration distribution was explored according to the flow rate and flow rate ratio of the air introduced into the cabin. Under the current ventilation conditions of the subway train HVAC system, the PM10 concentration was highest in the cabin central area where exhaust outlets are located and decreased toward both ends of the cabin. The indoor airflow was improved and the PM10 concentration was reduced by increasing the flow rate of the supplied air at both ends of the cabin while decreasing it in the central area. It was found that the strengthened PM10 concentration criterion of Seoul can be met by increasing the ventilation flow rate to 700 CMH (currently, 500 CMH) and the filter efficiency to 85% (currently, 70%) while maintaining the current flow rate ratio. These results are expected to be used as important reference data for reducing the PM concentration in subway cabins and thereby improving indoor air quality.

Particulate Matter in the Korea Train eXpress (KTX) Cabin and its Exposure

This study aims to assess the particulate matter (PM1, PM2.5, PM10) and black carbon (BC) in the Korea Train eXpress (KTX) cabin during train running, and the personal exposure of PM2.5 for the female/male passengers who use the KTX 20 days a month to commute. Intensive measurements were made on the day when the outside ambient PM concentration was much higher than usual. To compare with the PM concentration in the subway cabin, a measurement was also performed in some sections of the Seoul Metro subway (from Namyoung Station (hereafter referred to as the “Sta.”) to Jonggak Sta.). The amount of PM2.5 exposure was calculated for the male/female passengers who regularly board the KTX. The , which is the amount of PM2.5 exposure when moving by car in the same section, was also calculated. The PM concentration in the KTX cabin elevated and fallen off at train staying and train running, respectively. The PM2.5 concentrations inside KTX cabin at the stop station exhibited a remarkable positive correlation with those of outdoor. Compared to the PM concentration measured in the cabin of Seoul Metro subway, PM1, PM2.5, and PM10 in the KTX passenger cabin were 74.9%, 73.3%, and 62.7% of those in the cabin of Seoul Metro subway, respectively. The PM2.5 exposure amount (exposure PM2.5 (μg)) when moving the same section using the KTX and passenger cars was calculated, and as a result, the exposure PM2.5 (μg) for both male and female were 5.7 times lower in the KTX than that in car. The mapping result of BC concentration drawn on the KTX line from Iksan Sta. to Gwang-myeong Sta. shows that it fluctuated greatly for each service section or stop station.

Assessment of visual comfort in the lighting environments of subway cabins in China

ABSTRACT This paper presents a multi-dimensional evaluation and comparison of the visual comfort of the cabin lighting environments of five subways lines in Chengdu. The study proposes a visual comfort evaluation procedure that integrates objective and subjective methods combined with existing visual comfort measurement methods. Based on this evaluation procedure, the lighting conditions (illuminance and glare) in each cabin were measured using an illuminance metre and high-dynamic image technology, and an online questionnaire was used to understand passengers’ subjective experiences of cabin lighting. The results show that: seating layout has no significant influence on the visual performance of mobile phones or on spatial brightness; horizontal illuminance in the lighting environments of subway cabins has no significant influence on task performance of passengers using mobile phones; the overall perception of subway cabin spatial brightness increases with vertical illuminance; and passengers have no obvious preference for a cabin correlated colour temperature.

A Real-Time Comparison of Four Particulate Matter Size Fractions in the Personal Breathing Zone of Paris Subway Workers: A Six-Week Prospective Study

We developed a Bayesian spline model for real-time mass concentrations of particulate matter (PM10, PM2.5, PM1, and PM0.3) measured simultaneously in the personal breathing zone of Parisian subway workers. The measurements were performed by GRIMM, a gravimetric method, and DiSCmini during the workers’ work shifts over two consecutive weeks. The measured PM concentrations were analyzed with respect to the working environment, the underground station, and any specific events that occurred during the work shift. Overall, PM0.3 concentrations were more than an order of magnitude lower compared to the other PM concentrations and showed the highest temporal variation. The PM2.5 levels raised the highest exposure concern: 15 stations out of 37 had higher mass concentrations compared to the reference. Station PM levels were not correlated with the annual number of passengers entering the station, the year of station opening or renovation, or the number of platforms and tracks. The correlation with the number of station entrances was consistently negative for all PM sizes, whereas the number of correspondence concourses was negatively correlated with PM0.3 and PM10 levels and positively correlated with PM1 and PM2.5 levels. The highest PM10 exposure was observed for the station platform, followed by the subway cabin and train, while ticket counters had the highest PM0.3, PM1, and PM2.5 mass concentrations. We further found that compared to gravimetric and DiSCmini measurements, GRIMM results showed some discrepancies, with an underestimation of exposure levels. Therefore, we suggest using GRIMM, calibrated by gravimetric methods, for PM sizes above 1μm, and DiSCmini for sizes below 700 nm.

Study on Occupancy Behaviors of Passengers in the Subway Cabin: An Observation in Chengdu, China

Insufficient attention has been paid to how subway cabins are used by passengers and especially the distribution of passengers and occupancy of facilities. In this study, passengers were observed in 133 sections from the beginning to the end of the early peak of Chengdu Metro in the working days. The differences in occupancy behaviors of passengers to different areas, seats, and standing auxiliary facilities in the cabin were analyzed by the nonparametric test. The occupancy curve was fitted by the least square method from the minimum to the maximum load factor, and the prediction and explanatory model for the use of cabin was established. As expected, the distribution of passengers in the cabin is uneven. The highest occupancy rate has been maintained at the cabin end. Female passengers accounted for the largest proportion in the door area, while male passengers accounted for a larger proportion at the end of the cabin. There is no difference in the use of different seat types by passengers. There are more seats in female passengers, and females are more likely to get the remaining seats when the seat load is nearly saturated. For the auxiliary standing facilities, there are always passengers who do not use the facilities and the proportion is increasing. The facilities that can be relied on account for a greater median proportion of the passengers with facilities, but service capacity is limited. In response to these conclusions, measures to improve the design of the cabin are proposed.

Co-Exposure to Multiple Pollutants and Its Cardiovascular Effects in a Subway System - Beijing Municipality, China, 2017.

What is already known on this topic?With rapid urbanization, traffic-related air pollution has become a global concern. However, its association with cardiovascular health has not been fully elucidated.What is added by this report?This study provided novel evidence of the joint cardiovascular effect of multiple pollutants in subway cabins, further identified two pollutants that played dominant roles, and validated the effectiveness of targeted interventions.What are the implications for public health practice?The findings were helpful to guide the formulation and development of prevention and control strategies for key traffic-related pollutants that endanger the cardiovascular health of commuters.

Cancer and non-cancer risk associated with PM10-bound metals in subways

Non-cancer and cancer health risks to humans associated with respirable particulate matter ≤10 µm (PM10) in an indoor microenvironment such as a subway cabin are currently a public concern. In this study, detailed investigations of human health risks due to PM10-bound metals in a subway cabin were conducted for the first time. Cancer risks (CRs) were estimated for inhalation exposure (CRinh) using a Monte Carlo probability density function and were compared with incremental lifetime CRs (ILCRs). Moreover, the percentage contributions of each metal to the risk levels were calculated to identify the elements potentially responsible for human health risks. The significant (>1) for non-CRs levels as HI (hazard index) was estimated for children and adults for all types of exposure (inhalation, ingestion, and dermal). Pb, Cr, and Ni were recognized as the foremost contributors to the HQ (hazard quotient) levels for all types of exposure. For subway commuters, the CRinh and ILCR levels for adults were marginally higher than the satisfactory maximum point of confinement of the lifetime carcinogenic risk level (1 × 10−5) where as CRinh for children was within the acceptable limit (1 × 10−6–1 × 10−5). Cr was identified as the predominant carcinogenic element, with 91% contribution to the total CR level in the subway cabin on the Seoul Metropolitan Subway.

Commuter exposure to particulate matters in four common transportation modes in Nanjing

Particulate matter (PM) is one of the major air pollutants in China. Traffic-related microenvironments are the typical scenarios exposed to high PM concentrations. This paper investigates the personal exposure to PM during commuting in Nanjing in four transportation modes, i.e. subway, bicycle, bus and walking. The measurements were conducted in a heavy-traffic street during rush hours in summer and winter. The result reveals significant PM concentration differences between various commuting modes. Passengers in subway cabin are exposed to lowest PM1 (38.3 μg/m3) and PM2.5 (54.4 μg/m3) concentrations, while passengers in subway station are exposed to highest PM2.5 (90.5 μg/m3). Pedestrians are exposed to highest PM1 (59.5 μg/m3). Both outdoor and indoor-generated particles contribute a lot to the particles in subway station and 63.4% of the PM2.5 generated in subway station are between 1 μm and 2.5 μm in size. Most particles in subway cabin are from subway station and most particles in bus cabin come from the outdoor air, while indoor sources contribute little. Spatial particle concentration variations were observed in subway station. The particle concentration at a deeper level is usually higher than the concentration at a shallower level. Substantial particles within 1–2.5 μm in size were observed at the platform and the portion within 1–2.5 μm decreased at shallower levels. The PM inhalation during subway trip is lowest while the inhalations during walking and cycling are more than 5 times higher. During a short distance subway trip, the exposure in subway station contributes most of the total particle inhalation during the entire subway trip.

Analysis of induced interior air flow in subway train cabin due to accelerating and decelerating

ABSTRACTDue to the importance of air-conditioning system in public transport vehicles, some researches focused on improving the efficiency of Air Conditioning (AC) systems, especially in urban and high speed trains. This study investigates the induced airflow in long corridor of metro train in accelerating and decelerating modes, analytically and experimentally. The simplified governing equation of Navier-Stokes for a three-dimensional time-dependent viscose flow is solved analytically using mixed method of separation of variables and Duhamel integral. The pure closed form solution is introduced and compared with experimental data in real Metro train with good accuracy. Finally the effects of this airflow on the performance and efficiency of the train's ventilation system is tested, analyzed and discussed to depict the homogenization of air temperature alongside the train. The results of this study can be used as benchmark for other numerical analysis and as a base for design of the train ventilation system.

Generation Characteristics of Nanoparticles Emitted from Subways in Operation

In this study, measurements were carried out to identify the generation characteristics of wear particles emitted under a subway cabin during operation. Along with a fast mobility particle sizer, probes were installed under a subway cabin and in a subway tunnel to measure the size distributions of nanoparticles at 1-s intervals. Based on the particle density measured under the cabin minus that measured in the tunnel, the size distribution of wear particles generated under the cabin during deceleration was estimated to be bimodal at 165.5 nm and 6.98 nm. These particles were most likely generated from wheel-rail contact, as the train utilized electric braking (no mechanical force applied). In addition, a change in the wear mechanism appears to have arisen due to the increased temperature of the wheel-rail contact while nanoparticles were being emitted, leading to an initial generation of 165.5-nm particles followed by 6.98-nm particles 1 s later.

기기 중성자방사화 분석을 이용한 대전 지하철 객차 내 PM10과 미량성분의 특성

기기 중성자방사화 분석을 이용한 대전 지하철 객차 내 PM10과 미량성분의 특성

Particulate Matters Levels in Subway Tunnels and Cabins

This research aims to discern the characteristics of PM₁₀ concentrations measured in subway cabins, tunnels and outdoors at the Seoul Metropolitan subways. PM₁₀ concentrations in cabins were found between the range of 45.3 and 101.9μg/m³, and in tunnels the ranges were between 155.3 and 230.6μg/m³. PM₁₀ concentrations in cabins and tunnels during rush hours were 16.5% and 3.8% respectively higher than non-rush hours. Fine particles were higher than that of coarse particles both in subway cabins and tunnels.

서울시 일부 지하철 전동차 객실 시트의 먼지 진드기 알레르겐 농도와 세균 내독소 농도 조사

서울시 일부 지하철 전동차 객실 시트의 먼지 진드기 알레르겐 농도와 세균 내독소 농도 조사

지하철 전동차 객실 내부 공기질 조사 연구

지하철 전동차 객실 내부 공기질 조사 연구

Status of PM in Seoul metropolitan subway cabins and effectiveness of subway cabin air purifier (SCAP)

The increasing importance of indoor air quality management on public transport led the Korean government to amend the indoor air quality control in public use facilities, etc. Act including modes of public transport under the Act from June 2013. Particulate matter (PM) in subway systems is reported as being mostly generated by friction—between the wheels and the rails, between the wheels and the brake pads, and between the catenaries and the pantographs. In order to reduce PM level in subway cabins, a newly developed subway cabin air purifier (SCAP) was installed on the ceilings of the cabins. In this study, we analyzed indoor PM concentrations through continuous measurement of PMs less than 10 μm in diameter (PM10) and PMs less than 2.5 μm in diameter (PM2.5) in the cabins of line 2 and line 5 of the Seoul metropolitan subway network, comparing the concentrations in cabins where SCAP devices were installed to cabins without them in order to verify SCAP effectiveness. In both cabins with and without SCAP, the ratio of indoor to outdoor PM10 (I/O for PM10) showed a two-times higher value in line 5 than in line 2, which indicated that the entirely underground line 5 was less ventilated with outdoor air. In addition, the ratio of indoor PM2.5/PM10 showed that coarse mode PM was more abundant in line 5 due to poor ventilation in the tunnel sections compared to that of line 2. Regarding the effectiveness of SCAP, it was found that changes of PM10 concentrations in line 2 and line 5 were from 132.8 to 112.2 μg/m3 (15.5 % efficiency) and from 154.4 to 114.2 μg/m3 (26.0 % efficiency) after SCAP installation, respectively.

수도권 지하철 전동차에서의 라돈 농도 분포 조사

In this study, we have observed the airborne radon levels in the subway cabins before and after platform screen doors (PSD) installation. The measurements have been conducted at Seoul metropolitan subway lines in 2008, 2009 and 2010. The mean concentration of the radon inside subway cabins were increased by approximately 53% from to by installing PSD. After PSD installation, measured values for the different lines were rather different, and varied between 8.2 and . And mean radon concentrations were in the decreasing order for subway lines 5, 6, 7, 8, 3, 4, 2, 9 and 1. It was also found that the indoor radon concentrations in the subway cabins were highly dependent on the management approach of a ventilation system at the subway stations. By assuming an average of and spent in subway cabin, effective doses to passengers and employee were estimated. The expected annual effective dose, in case of an equilibrium factor of 0.4, were and , respectively.