The influence of ozone on self-evaluation of symptoms in a simulated aircraft cabin

Simulated 4-h flights were carried out in a realistic model of a three-row, 21-seat section of an aircraft cabin that was reconstructed inside a climate chamber. Twenty-nine female subjects, age 19-27 years, were split into two groups; each group was exposed to four conditions: two levels of ozone (<2 and 60-80 p.p.b.) at two outside air supply rates (2.4 and 4.7 l/s per person). A companion study measured the chemicals present in the cabin air during each of the simulated flights. The subjects completed questionnaires to provide subjective assessments of air quality and symptoms typical of complaints experienced during actual flight. Additionally, the subjects' visual acuity, nasal peak flow and skin dryness were measured. Based on self-recorded responses after 3(1/4) h in the simulated aircraft cabin, they judged the air quality and 12 of the symptoms (including eye and nasal irritation, lip and skin dryness, headache, dizziness, mental tension, claustrophobia) to be significantly worse (P<0.05) for the "ozone" condition compared to the "no ozone" condition. The results indicate that ozone and products of ozone-initiated chemistry are contributing to such complaints, and imply previously unappreciated benefits when ozone is removed from the ventilation air supplied to an aircraft cabin.     

Tuberculosis and traveling

The traveler faces two types of specific risks for tuberculosis: that of a possible contagion through the unexpected contact with an infected person during a commercial flight (the available studies dealing mostly with cases of transmission during flights, the chapter will deal mainly with this question) and that of a possible contamination during a stay in a country with strong prevalence of TB. The ventilation in airliners is designed to limit movements of air to the front or the back of the aircraft. Moreover, studies have shown that the transmission of M. tuberculosis from passenger to passenger was observed only within the same cabin. Consequently, it is usually admitted that only passengers sitting next to the patient (3 rows ahead and behind, and 3 seats on the right and on the left of the infected passenger, depending on the aircraft's seat set-up) as well as the members of crew working in this same cabin must be warned of the potential risk a posteriori. The recommendations which follow are to be considered all the more carefully that the duration of stay is long, that the country or the geographical area is more at the risk (for example urban environment in a highly endemic zone), that the traveler is more fragile (infants and elderly people, immunodepression, etc.) and that activities during the stay will be more at risk.     

民用飞机客舱空气质量标准限值及检测方法的比较

目的为飞机客舱空气质量污染事故调查、飞机适航认证及客舱环境卫生监测提供参考。方法比较目前国内外民用飞机客舱空气质量标准限值及检测方法。结果我国民用飞机客舱空气质量参数限值与国外限值要求有一定差别,主要是我国飞机客舱相对湿度限值比国外限值要求偏高;我国客舱温度限值要求按季节划分,国外则按飞机地面和巡航状态区分;我国客舱风速的限值略大于国外限值;而我国客舱二氧化碳和一氧化碳浓度限值均小于国外限值。其部分相关的检测方法也与国外存在一定差距。结论我国公共交通工具卫生标准中有关飞机客舱卫生部分参数限值及检测方法尚不够合理,建议应建立适合我国飞机客舱空气质量的卫生标准体系,包括飞机客舱空气质量各参数限值及其检测方法、评价指南等。     

冬季长途航运客轮卫生状况调查

本文对冬季长途航运客轮的卫生状况进行了调查。结果表明,客轮舱室内空气污染严重,细菌总数、CO_2超标率分别为23.64％、18.63％。舱室档次越低,CO、CO_2污染越严重,有乘客吸烟的舱室CO、CO_2浓度明显高于无乘客吸烟的舱室。CO_2浓度舱内>过道>甲板。乘客安静状态下(0～7时)舱内CO_2浓度最高,而CO浓度较低。舱室内温度按等级依次为五等>四等>三等>二等。     

Assessing total fungal concentrations on commercial passenger aircraft using mixed-effects modeling

The primary objective of this study was to compare airborne fungal concentrations onboard commercial passenger aircraft at various in-flight times with concentrations measured inside and outside airport terminals. A secondary objective was to investigate the use of mixed-effects modeling of repeat measures from multiple sampling intervals and locations. Sequential triplicate culturable and total spore samples were collected on wide-body commercial passenger aircraft (n = 12) in the front and rear of coach class during six sampling intervals: boarding, midclimb, early cruise, midcruise, late cruise, and deplaning. Comparison samples were collected inside and outside airport terminals at the origin and destination cities. The MIXED procedure in SAS was used to model the mean and the covariance matrix of the natural log transformed fungal concentrations. Five covariance structures were tested to determine the appropriate models for analysis. Fixed effects considered included the sampling interval and, for samples obtained onboard the aircraft, location (front/rear of coach section), occupancy rate, and carbon dioxide concentrations. Overall, both total culturable and total spore fungal concentrations were low while the aircraft were in flight. No statistical difference was observed between measurements made in the front and rear sections of the coach cabin for either culturable or total spore concentrations. Both culturable and total spore concentrations were significantly higher outside the airport terminal compared with inside the airport terminal (p-value < 0.0001) and inside the aircraft (p-value < 0.0001). On the aircraft, the majority of total fungal exposure occurred during the boarding and deplaning processes, when the aircraft utilized ancillary ventilation and passenger activity was at its peak.     

2010年春运期间长途空调旅客列车车厢环境与空气质量综合评价

[目的]了解春运期间旅客列车车厢空气质量。[方法]2010年2月2-5日,在南宁铁路局选择旅客流量大的8趟长途空调列车,检测风速、温度、相对湿度、噪声、二氧化碳、空气细菌总数、可吸入颗粒物,并采用空气质量综合评价方法进行评价。[结果]8趟列车合计检测40个点,风速、温度、相对湿度、噪声、二氧化碳、空气细菌总数、可吸入颗粒物超标率分别为2.50%、97.50%、22.50%、75.00%、32.50%、2.50%、12.50%。综合评价4趟旅客列车车厢的环境、空气质量,Ⅱ级（未污染）的2趟,Ⅲ级（轻度污染）的2趟;最主要污染物3趟是二氧化碳,1趟是相对湿度。[结论]春运期间部分长途空调旅客列车车厢环境和空气受到污染。     

广藏列车空气质量及乘客主观舒适度的分析

目的探讨高原旅客列车的空气质量及乘客主观舒适度,为改善车厢空气质量,提高舒适度提供依据。方法2008年9月、2009年10月分别在广州一拉萨区间往返运行的列车的软卧、硬卧、硬座各1节车厢中抽取13～20名乘客,在列车运行至〈500、501～3000、3001—4000及〉4000m不同海拔高度时分别进行空气质量监测和乘客主观舒适度调查分析。空气质量指标包括微小气候（温度、湿度、风速）、CO2、CO、可吸入性颗粒物（PM10）、噪声、细菌总数、新风量、甲醛、总挥发性有机物（TVOC）和氧气含量等;乘客主观舒适度调查采用问卷调查的方式进行,调查内容包括乘客的闷感、异味感、空气新鲜感等主观感觉。结果共监测198个监测点次,温度超标率夏季为80．16％,冬季为100．00％,湿度、CO2、PM10和新风量超标率分别为10．10％、56．06％、1．52％和22．88％;不同海拔高度间湿度、风速、氧气含量、CO、CO2、PM10、细菌总数、TVOC差异均有统计学意义（P〈0．01或P〈0．05）。共调查184名乘客,感觉有闷感的乘客占60．74％,感觉有异味的占56．77％,感觉到空气不新鲜的占19．43％。不同海拔高度乘客的闷感的发生率差异有统计学意义（P〈0．05）;CO2不达标（含量〉0．15％）与C02达标（含量≤0．15％）、氧气含量≥14．67％与〈14．67％的情况下乘客闷感的发生率比较差异均有统计学意义（P〈0．01或P〈0．05）;新风量不达标[〈20m3／（h·人）]与新风量达标[≥20m3／（h·人）]的情况下乘客的闷感、异味感和空气不新鲜感的发生率比较差异有统计学意义（P〈0．01或P〈0．05）。结论受调查高原旅客列车的空气质量的部分指标未能达到卫生标准和部分旅客主观舒适度欠佳。建议适当提高新风量和CO2等重点指标的卫生要求,以及纳入氧气含量等重要指标以改善列车内的空气质量,提高乘客的舒适度。     

空调公共汽车内空气中菌落总数及二氧化碳浓度分析

目的了解不同乘客人数、不同季节、不同天气条件的空调公共汽车内空气污染状况,为制定相应的防制对策提供依据。方法选择不同乘客人数、不同季节、不同天气条件的空调公共汽车,分别测定车厢空气中菌落总数及CO2的浓度。结果在微小气候基本相同及开启空调通风系统的条件下,空调公共汽车内空气中菌落总数及CO2浓度在不同乘客人数段差异有统计学意义(P<0.05),随着乘客人数的增加,菌落总数及CO2平均浓度也显著增高。CO2平均浓度严重超标,部分车辆的空气菌落总数亦超标。CO2的最高浓度超出我国《室内空气质量标准》GB/T18883-2002最高容许浓度的7.3倍。在车内乘客人数接近的条件下,空调公共汽车在冬、春季的菌落总数及CO2平均浓度均显著高于夏、秋季。从晴天、阴天到雨天,菌落总数及CO2平均浓度均逐渐降低,车内空气质量逐渐改善。结论空调公共汽车内空气中菌落总数及CO2浓度水平与乘客人数、天气和季节具有一定关系。空调公共汽车这个密闭的公共场所应给予高度警惕和加强防范。     

Evaluating fungal populations by genera/species on wide body commercial passenger aircraft and in airport terminals

Given the potential health effects of fungi and the amount of time aircrew and passengers spend inside aircraft, it is important to study fungal populations in the aircraft environment. Research objectives included documenting the genera/species of airborne culturable fungal concentrations and total spore concentrations on a twin-aisle wide body commercial passenger aircraft. Twelve flights between 4.5 and 6.5 h in duration on Boeing 767 (B-767) aircraft were evaluated. Two air cooling packs and 50% recirculation rate (i.e. 50:50 mix of outside air and filtered inside air) were utilized during flight operations. Passenger occupancy rates varied from 67 to 100%. N-6 impactors and total spore traps were used to collect sequential, triplicate air samples in the front and rear of coach class during six sampling intervals throughout each flight: boarding, mid-climb, early cruise, mid-cruise, late cruise and deplaning. Comparison air samples were also collected inside and outside the airport terminals at the origin and destination cities resulting in a total of 522 culturable and 517 total spore samples. A total of 45 surface wipe samples were collected using swabs onboard the aircraft and inside the airport terminals. A variety of taxa were observed in the culturable and total spore samples. A frequency analysis of the fungal data indicated that Cladosporium, Aspergillus and Penicillium were predominant genera in the culturable samples whereas Cladosporium, Basidiospores and Penicillium/Aspergillus were predominant in the total spore samples. Fungal populations observed inside the aircraft were comprised of similar genera, detected significantly less frequently and with lower mean concentrations than those observed in typical office buildings. Although sources internal to the aircraft could not be ruled out, our data demonstrate the importance of passenger activity as the source of the fungi observed on aircraft. Isolated fungal peak events occurred occasionally when concentrations of a particular genus or species rose sharply inside the cabin for a limited period. Overall, our research demonstrates that on the sampled flights the B-767 filtration system operated efficiently to remove fungal spores when two air cooling packs and 50% recirculation rate were utilized during flight operations.     

Indoor air quality in a middle school, Part I: Use of CO2 as a tracer for effective ventilation

The overall objective of the study was to evaluate the indoor air quality at a middle school with an emphasis on characterizing baseline conditions. The focus of this article is on the relationship between occupancy and measured concentrations of carbon dioxide, and an evaluation of the use of carbon dioxide as a tracer for ventilation in the school. The school was characterized as having no health complaints, good maintenance schedules, no carpeting within the classrooms or hallways, and no significant remodeling, and its officials had agreed to allow the sampling to take place during school hours. Monitoring followed the guidelines recommended in the "Preliminary Draft: Conceptual Standardized EPA Protocol For Characterizing Indoor Air Quality in School Buildings." Four indoor locations including the cafeteria, a science classroom, an art classroom, and the lobby outside the main office, and one outdoor location were sampled for various environmental comfort and pollutant parameters for one week in February 1997. A consistent relationship between hourly occupancy and corresponding carbon dioxide concentrations was seen. Carbon dioxide concentrations in the cafeteria, art room, and lobby were within specified American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) guidelines for comfort (< 1000 ppm). The science room had the highest concentrations (frequently exceeding 1000 ppm) due to high occupancy and non-functioning unit ventilators. Measured ventilation rates were within specified ASHRAE guidelines for the art room, cafeteria, and lobby. The science room, which relied on natural ventilation only, was not able to meet the ASHRAE guideline on one of the three days studied. The use of a completely mixed space, one compartment mass balance model with estimated CO2 generation rates and measured CO2 concentrations is shown to be a useful method for evaluating ventilation. Modeled effective ventilation, air changes per hour, and mixing factors reflected measured carbon dioxide concentrations and measured ventilation in each room. Mechanical ventilation afforded better mixing than natural ventilation. This study demonstrates the usefulness of collecting indoor CO2 and occupancy data when carrying out indoor air quality evaluations in schools.     

上海市黄浦区市级综合医院候诊输液室空气质量调查

[目的]了解上海市黄浦区市级综合性医院候诊输液室的空气质量及影响因素。[方法]对医院候诊及输液区域的室内卫生指标和集中空调通风系统卫生指标进行检测,根据《公共场所卫生监测技术规范》要求设点检测,以《医院候诊室卫生标准》和《公共场所集中空调通风系统卫生规范》进行评价。[结果]室内卫生学指标中噪声及二氧化碳合格率分别为0.00%和24.07%。集中空调通风设备卫生学指标中可吸入颗粒物(PM10)及细菌总数合格率分别为52.78%和83.33%。空气中二氧化碳浓度与人员密度呈直线正相关,在人员密度相同的情况下,通风条件不同的场所空气中二氧化碳浓度差异有统计学意义(P0.01)。[结论]医院候诊输液区域噪声和二氧化碳问题最为突出,二氧化碳浓度与通风条件及人员密度密切相关。医院集中空调通风设备的卫生管理亟待规范。     

人工负离子净化舰艇舱内空气的效果研究

为探讨人工负离子对军用舰艇舱内空气质量的改善,利用电晕放电原理,在舰艇舱内建立人工放电气候。结果表明,人工负离子环境下,舱内空气中的悬浮微粒、甲醛和二氧化碳分别降低了８９．５％,８３．３％,７６％和３２％,舰内船员的胸闷、头痛、头晕、恶心等症状明显减轻,说明人工负离子对舱内空气质量有较好改善。     

An evaluation of ventilation system flow rates and levels of carbon dioxide,ambient temperature,and relative humidity in restaurants

Studies of the indoor air quality of restaurants have rarely focused on ventilation system performance in relation to air pollutants and climatic factors. This study was conducted in eight restaurants to examine this issue by determining the ventilation flow rates and the levels of carbon dioxide (CO2), ambient temperature, and relative humidity during at least one complete shift of serving a meal. The mean values of number of dining patrons, ventilation flow rates, and the levels of CO2, ambient temperature, and relative humidity were not significantly different in the nonsmoking dining rooms and the smoking dining rooms. The mean ventilation flow rates in individual restaurants ranged from 42-113 cubic feet per minute per person (cfm/person), overall exceeding the recommended lower limit of 30 cfm/person. The mean levels of CO2 in two restaurants (646 and 819 ppm) were below, and in the other six restaurants (ranging 1,012-1,820 ppm) were above the recommended upper limit of 1000 ppm. The levels of CO2 in each restaurant significantly correlated with the number of dining patrons and in four restaurants accumulated gradually over time. In the nonsmoking dining rooms, the levels of CO2 increased significantly as the ventilation How rates decreased. The mean ambient temperature in restaurants (ranging from 22 degrees C - 24 degrees C) were within the recommended range of 20 degrees C - 26 degrees C. The mean relative humidity in six restaurants (ranging from 46%-59%) were within the recommended upper limit of 60 percent, and in two restaurants (62% and 71%) were slightly higher than this recommended limit. It was concluded that although the mean ventilation flow rates in all restaurants exceeded the recommended value, the design of the ventilation system or the distribution of air flow rate in some sections of restaurants were not appropriate to keep the levels of CO2 and relative humidity at some measurement locations below the recommended limits.     

Dichlorvos vapour disinsection of aircraft

The authors describe the testing of an automatic aircraft disinsection system permanently installed on a commercial DC-6B passenger aircraft. An air-compressor forces ambient cabin air, partially saturated with dichlorvos vapour at a set concentration, through the cabin, cockpit and baggage compartments of the aircraft for 30 minutes. Insecticide concentrations and insect mortality were observed in post-overhaul check flights, and insect mortality and passenger reactions were observed on scheduled flights between Miami, Florida, and Nassau, Bahamas.     

常低压低氧高二氧化碳动物实验舱的研制

介绍了一种常低压低氧高二氧化碳动物实验舱,该舱基于现代传感器变送技术、工控测控模块、组态软件程序策略的系统组合设计,首次在一个密封舱内实现模拟平原、高原环境下的低氧、高二氧化碳和温度、湿度等多参数指标的交叉自动测量与控制,为研究各种因缺氧而导致的各种循环与呼吸系统疾病的生理机理提供了一种实验技术平台。临床应用表明,其测控准确,安全可靠。     

Comparison of the constituents of two jet engine lubricating oils and their volatile pyrolytic degradation products

Leaking oil seals in jet engines, at locations prior to the compressor stage, can be a cause of smoke in the cabins of BAe-146 aircraft. Compressed combustion air is bled off to pressurize the cabin and to provide a source of fresh air. Bleed air is diverted from a location just prior to the combustion chamber at a temperature around 500 degrees C. To prevent oil breakdown products from entering the cabin air, catalytic converters have been used to clean the air. During an oil seal failure this device becomes overloaded and smoke is observed in the cabin. Some aircraft companies have removed the catalytic converters and claim an improvement in air quality. During an oil seal failure, however, the flight crew is potentially exposed to the thermal breakdown products of the engine oils. Because very little is known regarding the thermal breakdown products of jet engine lubrication oils, two commercially available oils were investigated under laboratory conditions at 525 degrees C to measure the release of CO, CO2,NO2, and HCN as well as volatiles which were analyzed using GC-Mass spectrometry in an attempt to see if the neurotoxic agents tricresyl phosphates (TCPs) and trimethyl propane phosphate (TMPP) would be present or formed. TMPP was not found in these experiments. Some CO2 was generated along with CO which reached levels in excess of 100 ppm. HCN and NO2 were not detected. GC compositions of the two bulk oils and their breakdown products were almost identical. The presence of TCPs was confirmed in the bulk oils and in the volatiles. Localized condensation in the ventilation ducts and filters in the air conditioning packs are likely the reason why the presence of TCPs has not been demonstrated in cabin air. It was recommended that this needed to be verified in aircraft.     

Analysis of CO<Subscript>2</Subscript> monitoring data demonstrates poor ventilation rates in Albanian schools during the cold season

Poor ventilation in schools is associated with accumulation of indoor-generated pollutants, which is associated with “stuffy” air, elevated risk of infectious diseases and impaired learning outcomes. This survey in Albania was conducted as part of WHO’s efforts to facilitate assessments of indoor air quality and other environmental factors in schools in the European Region. The survey was conducted in 36 classrooms in 12 middle schools (eight urban and four rural) from December 2011 through March 2012. In each school, carbon dioxide (CO₂) was continuously measured in three classrooms during one school week. Ventilation rates during classes were estimated using the build-up and steady-state mass balance equations utilizing CO₂ concentration data, classroom occupancy and classroom volume. All 12 schools had gravimetric ventilation systems. Heating systems were absent or not operational in most schools. Average classroom temperatures during lessons varied from 9.1 to 14.4 °C (median 11.7 °C) with lower temperature associated with poorer ventilation. Weekly average CO₂ levels during classes ranged from 1286 to 5546 ppm (median 2776 ppm) while average ventilation rates ranged from 0.8 to 3.6 (median 1.8) litres per second per person. Classrooms with indoor combustion heaters had higher indoor temperature, lower CO₂ levels and higher levels of carbon monoxide (CO). WHO guidelines on 1- and 8-h CO exposure levels were exceeded in one classroom. Classroom CO₂ levels were substantially above and ventilation rates below existing national and international guidelines. Detrimental impacts of poor ventilation on health and learning outcomes are likely to be substantial in Albanian schools during the cold season. Indoor temperature in most classrooms was below the commonly recommended levels.     

Indoor air quality in a middle school, Part II: Development of emission factors for particulate matter and bioaerosols

A middle school (grades 6 to 8) in a residential section of Springfield, Illinois, with no known air quality problems, was selected for a baseline indoor air quality survey. The study was designed to measure and evaluate air quality at the middle school with the objective of providing a benchmark for comparisons with measurements in schools with potential air quality problems. The focus of this article is on the development of emission factors for particulate matter and bioaerosols. The school was characterized as having no health complaints and good maintenance schedules. Four indoor locations including the cafeteria, a science classroom, an art classroom, the lobby outside the main office, and one outdoor location were sampled for various environmental comfort and pollutant parameters for one week in February 1997. Integrated samples (eight-hour sampling time) for respirable and total particulate matter, and short-term measurements (two-minute samples, three times per day) for bioaerosols were collected on three consecutive days at each of the sampling sites. Continuous measurements of carbon dioxide were logged at all locations for five days. Continuous measurements of respirable particulate matter were also collected in the lobby area. A linear relationship between occupancy and corresponding carbon dioxide and particle concentrations was seen. A completely mixed space, one compartment mass balance model with estimated CO2 generation rates and actual CO2 and particulate matter concentrations was used to model ventilation and pollutant emission rates. Emission factors for occupancy were represented by the slope of emission rate versus occupancy scatter plots. The following particle and bioaerosol emission factors were derived from the indoor measurements: total particles: 1.28 mg/hr/person-hr; respirable particles: 0.154 g/hr/person-hr; total fungi: 167 CFU/hr/person-min; thermophilic fungi: 35.8 CFU/hr/person-min; mesophilic fungi: 119 CFU/hr/person-min; total bacteria: 227 CFU/hr/person-min; gram-negative bacteria: 69.5 CFU/hr/person-min; gram-positive bacteria: 191 CFU/hr/person-min; Aspergillus: 17.0 CFU/hr/person-min; Penicillium: 161 CFU/hr/person-min; and yeasts: 16.4 CFU/hr/person-min.     

普通旅客列车硬座车厢空气污染状况调查

目的为了准确掌握普通（绿皮）旅客列车硬座车厢在严重超员情况下空气质量及微小气候,以便合理制定客车超员率,确保运输安全和广大旅客身体健康。方法对1625次列车进行6次全程监测。结果旅客列车硬座车厢在严重超员时,车厢平均温度过高（26．2℃）,湿度过大（61．2％）,空气质量恶化,二氧化碳浓度超标率为33．30％,在冬季气候变冷,车窗都关闭的情况下,细菌总数和可吸入颗粒均超标严重,平均超标率分别为0．15％和0．49％。结论绿皮无空调列车在旅客严重超员的情况下空气污浊,细菌总数超标,氧含量减少,二氧化碳等有害气体含量增加,给某些疾病的传播提供条件。     

Monitoring microbial populations on wide-body commercial passenger aircraft

Although exposure to bacteria has been assessed in cabin air previously, minimal numbers of samples have been collected in-flight. The purpose of this research was to comprehensively characterize bacterial concentrations in the aircraft cabin. Twelve randomly selected flights were sampled on Boeing-767 aircraft, each with a flight duration between 4.5 and 6.5 h. N-6 impactors were used to collect sequential, triplicate air samples in the front and rear of coach class during six sampling intervals throughout each flight: boarding, mid-climb, early cruise, mid-cruise, late cruise and deplaning. Comparison air samples were also collected inside and outside the airport terminals at the origin and destination cities. The MIXED procedure in SAS was used to model the mean and the covariance matrix of the natural log-transformed bacterial concentrations. A total of 513 airborne culturable bacterial samples were collected. During flight (mid-climb and cruise intervals), a model-adjusted geometric mean (GM) of 136 total colony-forming units per cubic meter of air sampled (CFU x m(-3)) and geometric standard deviation of 2.1 were observed. Bacterial concentrations were highest during the boarding (GM 290 CFU x m(-3)) and deplaning (GM 549 CFU x m(-3)) processes. Total bacterial concentrations observed during flight were significantly lower than GMs for boarding and deplaning (P values <0.0001-0.021) in the modeled results. Our findings highlight the fact that aerobiological concentrations can be dynamic and underscore the importance of appropriate sample size and design. The genera analysis indicates that passenger activity and high occupant density contribute to airborne bacterial generation. Overall, our research demonstrates that the bacteria recovered on observed flights were either common skin-surface organisms (primarily gram-positive cocci) or organisms common in dust and outdoor air.