The suspended particulate matter (SPM) and polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air along a main road

The change in concentration of suspended particulate matter (SPM) in indoor and outdoor air in the Tokyo metropolitan area was studied using a new portable sampler (SPMP-sampler). The relationship between the airborne particle concentration in indoor and outdoor air varied with the aerodynamic diameters of the particles. The concentration of the SPM in indoor air increased in proportion to that in outdoor air. The polycyclic aromatic hydrocarbon (PAH) concentration in SPM also varied with the aerodynamic diameters of the particles. Fine particles with diameters of less than 2 microns contained high concentrations of PAH. The PAH concentration in indoor air increased in proportion to that in outdoor air. There were significant correlations between the concentrations of B(k)F, B(a)P, and B(ghi)P in indoor air. The mutagenic activities in the airborne particles also varied with the aerodynamic diameters of the particles. Fine particles with diameters of less than 2 microns had high mutagenic activities.     

Study on suspended particulate matter and polycyclic aromatic hydrocarbons in indoor and outdoor air

Summary To study changes in the concentration of suspended particulate matter (SPM) in indoor and outdoor air, a new portable sampler (AND sampler) was designed that could separately collect particles exhibiting aerodynamic diameters of > 10 m, 2–10 m, and < 2 m. The relationship between the airborne particle concentration in indoor air and that in outdoor air varied with the aeordynamic diameter of the particles. The concentration of SPM in the indoor air increased in proportion to that in the outdoor air. The concentration of polycyclic aromatic hydrocarbons (PAH) in SPM also varied with the aerodynamic diameter of the particles. Fine particles exhibiting an aerodynamic diameter of < 2 m contained high concentration of PAH. The concentrations of benzo(k)fluoranthene, benzo(a)pyrene, and benzo (ghi) perylene in indoor air increased in proportion to those in outdoor air.     

Evaluation of a personal air sampler for twenty-four hour collection of fine particles and semivolatile organics.

The U.S. EPA has conducted an evaluation of a commercially available lightweight fine particle personal sampler for use in human exposure and biomarker studies involving 24-h collections of particulate matter, particle-bound organics such as polycyclic aromatic hydrocarbons (PAHs), and semivolatile organics (PAHs). Independent laboratory evaluation of the prototype design, intended to produce a 2.5-micron aerodynamic diameter cut-point at a flow between 1.5 and 1.7 lpm (liters per minute), indicated that at a challenge flow rate of 1.5 lpm, the sampler provided an aerodynamic cut-point (dp50) of only 1.7 microns. The variance between expected size selection resulted from the prototype's jet diameter dimension being inadvertently based upon a flow rate of 2.0 lpm rather than an intended 1.5-1.7 lpm. Other aerodynamic factors not presently accounted for may also have played an influence. Extrapolated cut-points for flow rates at 1 and 3 lpm for the prototype were determined to be 2.1 and 1.2 microns, respectively. Total losses attributed to unwanted particle retention within the sampler ranged from 10% for 0.91 micron size particles to essentially zero approaching diameters greater than 2.0 microns. The ambient concentration of particles (< 1.7 microns) needed for acceptable gravimetric filter measurements involving 24-h sample collection was determined to be 10 micrograms/m3. Investigation of the sampler to retain and recover PAHs using XAD-2 resin, often of importance in human exposure biomarker studies, indicated that corrected recoveries between 94% and 108% could be obtained for 16 priority pollutant PAH species. Overall evaluation of the personal monitor indicates that it has research utility due to its modular features and size but reconfiguration should be performed that would permit true PM2.5 size selection. The current configuration collects particles less than 2.5 microns at approximately 95% collection efficiency.     

Performance evaluation of continuous air monitor (CAM) sampling heads

Continuous air monitor (CAM) samplers are used to detect radioactive aerosol particles in nuclear facilities and to provide alarm signals should the concentrations exceed a multiple of the derived air concentration (DAC) of the radionuclide of concern in a set amount of time. Aerosol particles are drawn into a CAM sampler where collection is to take place upon a filter. Radioactivity of the particles is determined with a detector that is placed in close proximity to the filter face. An important determinant of CAM performance is the ability of the inlet and body of the CAM to transport particulate matter in the inhalable-size range (less than or equal to 10 microns aerodynamic diameter) to the filter without substantial loss or bias with respect to particulate size. Three types of CAM samplers were tested in a low-velocity aerosol wind tunnel to determine the degree to which particles penetrate through the flow systems to the collection filter under conditions typical of normal room air exchange rates. Two air velocities were used: 0.3 and 1.0 m s-1. The CAM samplers were primarily operated at a flow rate of 56.6 L min-1, although some tests were conducted at a flow rate of 28.3 L min-1. The CAM units were prototypes manufactured by Kurz Instruments, Eberline Instrument Corporation, and Victoreen Inc. These three units represent three different approaches to CAM head design. At an air speed of 1 m s-1, aerosol penetration to the filters of the Kurz unit was essentially 100% for particle sizes of 3 and 7-microns aerodynamic diameter and was 86% for a size of 15 microns. For the Eberline sampler, the penetration was over 80% for 3-microns particles but was reduced to less than 2% for 7-microns particles. The victoreen sampler showed penetration values of 98% for 3-microns aerodynamic diameter particles, 88% for 7-microns particles and 4% for a size of 15 microns. Air speed had little effect on the penetration results for the two speeds which were tested. Tests were conducted to determine the uniformity of deposits on the filters of the CAM samplers. For a particle size of 10 microns, the deposits were nonuniform for all three of the instruments.     

北京一次空气重污染过程室内外微生物气溶胶的浓度变化及影响因素分析

目的 分析北京一次空气重污染黄色预警期间室内外微生物气溶胶的浓度和粒径变化特征及相关影响因素。方法 采用Andersen空气微生物采样器在北京市空气重污染黄色预警期间对室内外环境进行采样、培养,同时记录采样时的环境因素、颗粒物以及气态污染物的浓度。结果 在本次北京市空气重污染期间室外细菌和真菌气溶胶浓度显著高于室内细菌和真菌气溶胶浓度(P<0.01),室内外细菌和真菌浓度变化趋势具有显著正相关(P<0.01),发现63.62%~96.70%的细菌或真菌气溶胶粒子直径小于5μm,Spearman相关分析表明室外细菌气溶胶浓度与温度具有显著正相关(P<0.01),与相对湿度具有显著负相关(P<0.01),室内细菌气溶胶浓度与温度和相对湿度具有显著正相关(P<0.01),室外真菌气溶胶浓度与SO2、PM10、PM2.5和AQI指数具有显著正相关(P<0.01),与相对湿度具有显著负相关,室内真菌气溶胶浓度与温度、SO2、PM10、PM2.5和AQI指数具有显著正相关(P<0.01),与O3浓度具有显著负相关(P<0.01)。结论 本次空气重污染预警期间,室外微生物气溶胶浓度显著高于室内,超过60%的室外或室内微生物气溶胶粒子直径小于5μm,室内外微生物气溶胶浓度受多个环境因素参数影响。     

Particulate matter and particle-attached polycyclic aromatic hydrocarbons in the indoor and outdoor air of Tokyo measured with personal monitors

Using two types of personal monitors for suspended particulate matter of diameter under 10 microm (PM-10) and for particles of diameter under 1 microm with attached polycyclic aromatic hydrocarbons (PPAH), we measured the PM-10 and PPAH concentrations in the indoor and outdoor air in various locations in the Tokyo area. The major findings were as follows. (1) The PPAH concentrations in a clean living room increased rapidly within several minutes after one cigarette was smoked. (2) Using the average indoor concentrations of PM-10 and PPAH in a department store as control concentrations, respectively, where the average indoor PM-10 concentration was closest to an annual average outdoor concentration in Japan, the mean value for indoor air concentrations of PM-10 by location ranged from 2.2 to 6.2 times the control concentration, and the mean value for indoor air concentrations of PPAH by location ranged from 1.0 to 32.2 times the control concentration. (3) Using the same control concentrations, the mean value of outdoor concentrations of PM-10 by location ranged from 1.6 to 8.5 times the control concentration, while the mean value of outdoor concentrations of PPAH by location were up to 353.7 times the control concentration. The major polluted places were main traffic roads, highways, and street tunnels. (4) The correlation coefficient between the PM and the PPAH concentrations in the total monitoring time was 0.014, which was not significant (P>0.05).     

Characterization of PM10 in different environmental situations: studies in 2 urban sites and a rural site

BACKGROUND: Among the atmospheric pollutants detectable in the environment, the inhalable airborne particulate (PM10) is regarded with increasing concern. Indeed a number of epidemiological studies support the correlation between both acute and chronic adverse health effects and the presence of PM10 levels even lower than the WHO guide lines. Despite these epidemiological findings, it is yet unclear and still widely debated which characteristics of particulate matter are responsible for the observed health effects. The identification of one or more components of PM10 related to the health effects observed in the urban population is a research subject of primary importance for the coming years. OBJECTIVES: The aim of the present study was to characterise from a physical-chemical point of view the "coarse" (PM10-2.1) and the "fine" (PM2.1) fractions of the airborne particulate matter (PM10) sampled in three different sites dissimilar with regard to the weather conditions, the residential density and industrial activities. METHODS: The particles were collected by an eight-stage cascade impactor (Andersen particle fractionating sampler) with a pre-separator stage able to remove particles with aerodynamic diameter > 10 microns. Analysis of the particle samples was performed by a scanning electron microscopy (SEM) equipped with a thin-window system for X-ray microanalysis by energy dispersion spectrometry. RESULTS: The Hierarchical Cluster Analysis (HCA) of the analytical data revealed the presence of seven different particulate types (particle clusters) in the sampling sites: C-rich particles (cluster 1); Ca and Mg carbonates (cluster 2); Ca sulphates (cluster 3); silica particles (cluster 4); silicates (cluster 5); Fe-rich particles (cluster 6); metal compounds (cluster 7). CONCLUSIONS: Data obtained in this study demonstrated a significant correlation between the "coarse" fraction (PM10-2.1) composition and the characteristics of the sampling site. On the contrary the "fine" fraction (PM2.1) composition showed an unexpected uniformity in all the environments.     

Air sampling methodology for asphalt fume in asphalt production and asphalt roofing manufacturing facilities: total particulate sampler versus inhalable particulate sampler

In 2000, the American Conference of Governmental Industrial Hygienists (ACGIH(R)) changed its 1971 threshold limit value (TLV) for 8-hour time-weighted average (TWA) exposure to asphalt from 5 mg/m(3) total particulate (generally < or =40 micrometer [microm] diameter) to 0.5 mg/m(3) inhalable particulate (< or =100 microm aerodynamic diameter) as benzene-soluble aerosol. To date, no inhalable particulate sampling method has been standardized and validated for asphalt fume. Furthermore, much of the historical data were collected using total particulate samplers, and the comparability of total versus inhalable size fractions of asphalt fume is not known. Therefore, the present study compared results from two types of asphalt fume samplers: 1) a traditional total particulate sampler with a 37-mm filter in a closed-face cassette with a 4-mm orifice (NIOSH 5042) versus (2) an inhalable particulate sampler designed by the IOM with a 15-mm orifice. A total of 75 simultaneous pairs of samples were collected, including personal and area samples from 19 roofing and asphalt production facilities operated by 7 different manufacturers. Each sample was analyzed for total mass collected and for benzene-soluble mass. Data from the two sampling methods (total versus inhalable) were comparable for asphalt fumes up to an aerosol concentration of 10 mg/m(3). However, we conclude that the traditional total particulate method is preferable, for this reason: The vast majority of asphalt fume particles are <12.5 microm in diameter. The traditional sampler is designed to collect primarily particles < or =40 microm, while the IOM sampler is optimized for collecting particles < or =100 microm. Thus, the traditional sampler is less likely than the IOM sampler to collect the larger-size fraction of airborne particles, most of which are non-asphalt dust.     

Exposure to wood dust and heavy metals in workers using CCA pressure-treated wood

Chemical pesticide treatment enables relatively nonresistant woods to be used in outdoor construction projects. The most prevalent procedure used to protect these woods is pressure treatment with chromium, copper, and arsenic (CCA). This pilot study examined the airborne concentration and particle size distribution of wood particles, chromium, copper, and arsenic at both outdoor (measured over the whole work day) and indoor (measured during the performance of specific tasks) work sites. At the outdoor residential deck construction sites, the arithmetic mean total dust concentration, measured using personal filter cassette samplers, was 0.57 mg/m3. The mass median aerodynamic diameter (da) of the outdoor wood dust was greater than 20 microm. Indoor wood dust concentrations were significantly greater than those measured outdoor and were job category-dependent. The highest mean breathing zone dust concentration, 49.0 mg/m3, was measured at the indoor sanding operation. Personal impactor sampling demonstrated that the mean total airborne concentration of arsenic, but not chromium or copper, was consistently above recommended occupational exposure levels at the indoor work site, and occasionally at the outdoor work sites. At the indoor sanding operation, the mean total chromium, copper, and arsenic concentrations were 345, 170, and 342 microg/m3, respectively. Thus, significant exposure to airborne heavy metals can occur as a result of indoor and outdoor exposure to CCA pressure-treated wood dust. Therefore, current standards for wood dust may not adequately protect workers from the heavy metals commonly used in CCA pressure-treated wood.     

Characterization of thoracic fraction of airborne particular matter (PM10) in a urban area and in adjacent building

The aim of this study was to describe from a physico-chemical point of view the particles constituting the thoracic fraction of the airborne particulate matter (PM10) collected in two sampling stations: one in an urban area and another in an adjacent office building. The different sources contributing to the PM10 were identified and the relationship between the indoor PM10 and the outdoor PM10 assessed. Also the seasonal trend of PM10's physico-chemical characteristics was evaluated. Four particulate samplings were conducted between April 1999 and February 2000. The samples were analyzed by scanning electron microscopy with EDS X-ray attachment. The data sets, consisting of the atomic concentrations of the constituent chemical elements of the particulate, were subjected to Hierarchical Cluster Analysis to determine the principal components of PM10. The statistical analysis method allowed us to identify seven groups (clusters) of similar particles in the particulate matter: C-rich particles, carbonates, silica, silicates, sulphates, Fe-rich particles, metals. The seasonal trend of PM10 showed an increase in the alumino-silicates particles and a minor increment in sulphate particles in the summer. Moreover carbonaceous particles with a surface coating containing S were observed in the fine fraction of both outdoor and indoor particulate. This sulphurous coating turned out to be a strongly season-dependent feature. On the whole, the results suggest that the characteristics of indoor PM10 largely depend on the characteristics of outdoor PM10; the outdoor particulate quality had a major influence on the indoor particulate particularly during the summer season.     

Airborne aflatoxin in corn processing facilities in Georgia

Problems affecting the health of agricultural workers in processing facilities where grains are contaminated with aflatoxin have been noted previously. Airborne particulates produced during processing are reported to produce various carcinomas when inhaled by factory workers. Two corn processing plants within Georgia were surveyed during the fall of 1984 and 1985 with utilization of an Andersen 6-stage air sampler, a high-volume air sampler and a slit sampler. No airborne aflatoxin was found; however, 10% of settled dust samples were contaminated with aflatoxin. The average particles were found to be globular in shape with an effective diameter between 2 to 3 microns. Only 30% of the bulk corn samples contained aflatoxin, which was present at low levels (0.15 to 8 ppb).     

Volumetric assessment of airborne indoor and outdoor fungi at poultry and cattle houses in the Mazandaran Province, Iran

The aim of this study was to assess the volume of airborne fungi in the indoor and outdoor environment of poultry and cattle houses in the Mazandaran Province in Iran. Indoor and outdoor air of twenty cattle houses and twenty-five poultry houses were sampled using a single-stage impactor, which draws air at 20 L min-1 and impacts sampled material onto Petri plates containing malt extract agar. The plates were incubated at 30 °C for seven days, after which the resulting colonies were counted. The fungi were identified and counted microscopically and macroscopically. A total of 4,662 fungal colonies were isolated from 90 plates collected from indoor and outdoor air of cattle and poultry houses. Cladosporium (55.3 %), yeast (10.0 %), and Aspergillus (9.4 %) were the most common findings. The concentration of airborne fungi in cattle and poultry houses ranged from 10 CFU m-3 to 1700 CFU m-3 in indoor and 10 CFU m-3 to 2170 CFU m-3 in outdoor environments. Cladosporium had the highest mean indoor (424.5 CFU m-3) and outdoor (449.7 CFU m-3) air concentration in the cattle houses. In the poultry houses, the highest mean concentrations were measured for Cladosporium (551.0 CFU m-3) outdoors and yeast (440.7 CFU m-3) indoors. These levels might present an occupational risk, but threshold levels for these environments have yet to be established worldwide.     

Eczema increases susceptibility to PM10 in office indoor environments

The objective was to compare impact of indoor office environment on employees with eczema with those without eczema. Exposure was measured at 56 sites and modelled for 173 work places. Tear film stability, lysozyme in nasal lavage, immunoglobulin E (IgE), and Phadiatop were assessed, and symptoms and perceptions collected by questionnaires. Multiple regression analyses were applied, adjusted for age, gender, strain, current smoking, and respiratory infections. Those with eczema perceived temperature too high but not associated with measured temperature. They had increased lysozyme in nasal lavage associated with increased air temperature difference between 6 and 10 AM, more general and mucosal symptoms, and "dry or flushed facial skin" associated with airborne particulate matter less than 10 microns in diameter (PM(10)). Impact of PM(10) was most pronounced among those with eczema previous 30 days. Having eczema might be an important predictor for subjective and objective responses to indoor environment.     

Personal exposure to ultrafine particles and oxidative DNA damage

Exposure to ultrafine particles (UFPs) from vehicle exhaust has been related to risk of cardiovascular and pulmonary disease and cancer, even though exposure assessment is difficult. We studied personal exposure in terms of number concentrations of UFPs in the breathing zone, using portable instruments in six 18-hr periods in 15 healthy nonsmoking subjects. Exposure contrasts of outdoor pollution were achieved by bicycling in traffic for 5 days and in the laboratory for 1 day. Oxidative DNA damage was assessed as strand breaks and oxidized purines in mononuclear cells isolated from venous blood the morning after exposure measurement. Cumulated outdoor and cumulated indoor exposures to UFPs each were independent significant predictors of the level of purine oxidation in DNA but not of strand breaks. Ambient air concentrations of particulate matter with an aerodynamic diameter of < or = 10 microm (PM10), nitrous oxide, nitrogen dioxide, carbon monoxide, and/or number concentration of UFPs at urban background or busy street monitoring stations was not a significant predictor of DNA damage, although personal UFP exposure was correlated with urban background concentrations of CO and NO2, particularly during bicycling in traffic. The results indicate that biologic effects of UFPs occur at modest exposure, such as that occurring in traffic, which supports the relationship of UFPs and the adverse health effects of air pollution.     

Rapid detection and determination of the aerodynamic size range of airborne mycobacteria associated with whirlpools

Novel environmental air and water mycobacteria sampling and analytical methods are needed to circumvent difficulties associated with the use of culture-based methodologies. To implement this objective, a commercial, clinical, genus DNA amplification method utilizing the polymerase chain reaction (PCR) was interfaced with novel air sampling strategies in the laboratory. Two types of air samplers, a three-piece plastic, disposable filter cassette and an eight-stage micro-orifice uniform deposit impactor (MOUDI), were used in these studies. In both samplers, 37-mm polytetrafluoroethylene (PTFE) filters were used. Use of the MOUDI sampler permitted the capture of airborne mycobacteria in discrete size ranges, an important parameter for relating the airborne mycobacteria cells to potential respirable particles (aerodynamic diameter <10 microm) capable of causing health effects. Analysis of the samples was rapid, requiring only 1-1.5 days, as no microbial culturing or DNA purification was required. This approach was then used to detect suspected mycobacteria contamination associated with pools at a large public facility. PCR was also used to analyze various water samples from these pools. Again, no culturing or sample purification was required. Water samples taken from all ultraviolet light/hydrogen peroxide-treated whirlpools tested positive for the presence of mycobacteria. No mycobacteria were detected in the chlorine-treated pools and the water main supply facility. All air samples collected in the proximity of the indoor whirlpools and the associated changing rooms were strongly positive for airborne mycobacteria. The airborne mycobacteria particles were predominantly collected on MOUDI stages 1-6 representing an aerodynamic size range of 0.5 to 9.9 microm. In conclusion, using this approach permits the rapid detection of mycobacteria contamination as well as the routine monitoring of suspected pools. The approach circumvents problems associated with culture-based methods such as fungal overgrowth on agar plates, and the presence of nonculturable or difficult to culture mycobacteria strains.     

Indoor exposure to bioaerosol particles: levels and implications for inhalation dose rates in schoolchildren

Children spend most of their time inside schools and bioaerosol particles are part of their everyday environment. Although bioaerosol particles are considered to be a potential risk factor for various health concerns, information concerning the indoor exposures and inhalation doses is still limited. This study aimed (i) to quantify bacterial and fungal particles levels in indoor and outdoor air of public primary schools, (ii) to assess the influence of ambient air on bacteria and fungi presence indoors, and (iii) to estimate the inhalation dose rates for respective children (8–10 years old) in comparison with adult staff. Air samples were collected in 20 primary schools in a total of 71 classrooms during heating season with a microbiological air sampler. The results showed that indoor bacterial and fungal concentrations were higher than outdoor levels (p?<?0.05), which could be explained by differences in density of occupation, occupant’s activities, and inadequate ventilation. CO₂ levels were significantly correlated with indoor bacteria concentrations. Moreover, mean indoor bacteria concentrations were above national limit values in all the evaluated Porto primary schools, from two to nine times higher. Regarding fungi concentrations, indoor levels were above the reference value in 75% of the schools and overall indoor levels registered a 3-fold increase compared with outdoor values. Children had two times higher inhalation dose rates to bioaerosol particles when compared to adult individuals. Thus, due to their susceptibility, special attention should be given to educational settings in order to guarantee the children healthy development.     

Real-time monitoring of particles, PAH, and CO in an occupied townhouse

Beginning in October 1996, indoor and sometimes outdoor air at an occupied house in a suburban area of Virginia has been monitored continuously for particles, PAH, and CO. Two Climet monitors have been used to count particles in six size ranges between 0.3 and > 10 microns, with 1-minute averages being collected every 5 minutes. Two Ecochem PAH monitors have been used to sample for particle-bound PAHs once every minute. Also, two Langan CO monitor-data loggers have measured CO once each minute while logging the PAH data. Two Aethalometers measure black carbon. A single Scanning Mobility Particle Sizer (SMPS) measures ultrafine particles. The pairs of monitors are set up either to provide an indoor/outdoor or an upstairs office/downstairs kitchen comparison. Air exchange is occasionally measured using a Bruel & Kjaer 1302 SF6 monitor, as a parameter necessary for estimating deposition rates for particles and PAH. Results from the first 16 months of monitoring (approximately 10 M observations) include: neighborhood woodburning and morning rush hour traffic are the most important sources of PAH and black carbon outdoors; candles, matches, incense, and frying, sauteeing, broiling, deep-frying, and stir-frying are additional important indoor sources of PM. One citronella candle was an extremely powerful PAH source. Neither woodburning nor vehicles appears to be an important source of particles indoors, but frying, grilling, and sauteeing are extremely strong indoor sources, together with combustion events such as use of matches and candles. Physical movement was an important source of coarse but not fine particles. Use of the gas stove for extended periods of time led to increased CO concentrations--vehicles and woodburning were relatively minor sources in comparison. The gas oven, gas burners, and electric toaster oven were important sources of ultrafine particles (< 0.1 micron). A source-proximity effect was noted with the kitchen monitor reading two to five times higher than the upstairs monitor for particles from kitchen events, while the upstairs monitor often read higher than the kitchen monitor for events caused by physical activity alone.     

An evaluation of an ultra-high-volume airborne particulate sampler, the LEAP

A modified ultra-high-volume liquid electrostatic aerosol precipitator sampler (LEAP) was calibrated with near monodisperse aerosols of water-soluble and insoluble materials in the size range of 0.02 to 4 microns diameter. The water-soluble materials were ammonium sulfate and ammonium hydrogen sulfate. The insoluble materials included carnauba wax, stearic acid, silver chloride and Y(THD)3. The particulate collection efficiency of the unit ranged from 40 to 98%, depending on particle size, sampling air flow and also on particle material. Tests with water-soluble aerosols showed higher collection efficiency than those with the insoluble aerosols by about 2 to 10%. A sharp decline in the collection efficiency for the particles smaller than 0.1 micron was observed. A comparison with the available manufacturer's data for the particle diameters of 0.1 to 3 microns suggests that the manufacturer overestimated the collection efficiency by 6 to 20% for an air flow of 10 m3/min. We consider the LEAP to be a useful ultra-high volume sampler, especially suited for low-level or short-term sampling.     

Characterization of indoor particle sources: A study conducted in the metropolitan Boston area

An intensive particle monitoring study was conducted in homes in the Boston, Massachusetts, area during the winter and summer of 1996 in an effort to characterize sources of indoor particles. As part of this study, continuous particle size and mass concentration data were collected in four single-family homes, with each home monitored for one or two 6-day periods. Additionally, housing activity and air exchange rate data were collected. Cooking, cleaning, and the movement of people were identified as the most important indoor particle sources in these homes. These sources contributed significantly both to indoor concentrations (indoor-outdoor ratios varied between 2 and 33) and to altered indoor particle size distributions. Cooking, including broiling/baking, toasting, and barbecuing contributed primarily to particulate matter with physical diameters between 0.02 and 0.5 microm [PM((0.02-0.5))], with volume median diameters of between 0.13 and 0.25 microm. Sources of particulate matter with aerodynamic diameters between 0.7 and 10 microm [PM((0.7-10))] included sautéing, cleaning (vacuuming, dusting, and sweeping), and movement of people, with volume median diameters of between 3 and 4.3 microm. Frying was associated with particles from both PM((0.02-0.5)) and PM((0.7-10)). Air exchange rates ranged between 0.12 and 24.3 exchanges/hr and had significant impact on indoor particle levels and size distributions. Low air exchange rates (< 1 exchange/hr) resulted in longer air residence times and more time for particle concentrations from indoor sources to increase. When air exchange rates were higher (> 1 exchange/hr), the impact of indoor sources was less pronounced, as indoor particle concentrations tracked outdoor levels more closely.     

粒子数校正对空气微生物采样效果的影响

用活性生物粒子校正式对１９８７～１９８８年在北京西单６级ＡＮＤＥＲＳＥＮ生物粒子采样器采集的大气细菌粒子数进行校正。结果表明，ＡＮＤＥＲＳＥＮ生物粒子采样器采样３ｍｉｎ，空气取样量８４．９Ｌ，采集的大气细菌粒子数平均为２５７个，校正后的大气细菌粒子数平均为３１５个，校正后的大气细菌粒子数明显高于校正前的大气细菌粒子数，ｔ＝２．０１２，Ｐ＜０．０５。ＡＮＤＥＲＳＥＮ生物粒子采样器第１级（＞８．２μｍ）采集的大气细菌粒子数平均为９８个，校正后的大气细菌粒子数平均为１３６个，校正后的大气细菌粒子数明显高于校正前的大气细菌粒子数，ｔ＝２．４０９，Ｐ＜０．０５；第２级（６．０～８．２μｍ）～第６级（＜０．６５μｍ）各级校正后的大气细菌粒子数与校正前的大气细菌粒子数没有明显差别，ｔ＝１．７０１～０．０２６，Ｐ值均＞０．０５。粒数校正对ＡＮＤＥＲＳＥＮ生物粒子采样器采集的大气细菌粒子的大小分布和大气细菌粒子浓度的日变化的影响不明显。