Risk remaining from fine particle contaminants after vacuum cleaning of hard floor surfaces

In the indoor environment, settled surface dust often functions as a reservoir of hazardous particulate contaminants. In many circumstances, a major contributing source to the dust pool is exterior soil. Young children are particularly susceptible to exposure to both outdoor derived soil and indoor derived dust present in the indoor dust pool. This is because early in life the exploratory activities of the infant are dominated by touching and mouthing behavior. Inadvertent exposure to dust through mouth contact and hand-to-mouth activity is an inevitable consequence of infant development. Clean-up of indoor dust is, in many circumstances, critically important in efforts to minimize pediatric exposure. In this study, we examine the efficiency of vacuum cleaner removal of footwear-deposited soil on vinyl floor tiles. The study utilized a 5 × 10 foot (c. 152.5 × 305 cm) test surface composed of 1-foot-square (c. 30.5 × 30.5 cm) vinyl floor tiles. A composite test soil with moderately elevated levels of certain elements (e.g., Pb) was repeatedly introduced onto the floor surface by footwear track-on. The deposited soil was subsequently periodically removed from randomly selected tiles using a domestic vacuum cleaner. The mass and loading of soil elements on the tiles following vacuuming were determined both by wet wipe collection and by subsequent chemical analysis. It was found that vacuum cleaner removal eliminated much of the soil mass from the floor tiles. However, a small percentage of the mass was not removed and a portion of this residual mass could be picked up by moistened hand-lifts. Furthermore, although the post-vacuuming tile soil mass was sizably reduced, for some elements (notably Pb) the concentration in the residual soil was increased. We interpret this increased metal concentration to be a particle size effect with smaller particles (with a proportionately higher metal content) remaining in situ after vacuuming.     

Indoor particle dynamics in a school office: determination of particle concentrations,deposition rates and penetration factors under naturally ventilated conditions

Recently, the problem of indoor particulate matter pollution has received much attention. An increasing number of epidemiological studies show that the concentration of atmospheric particulate matter has a significant effect on human health, even at very low concentrations. Most of these investigations have relied upon outdoor particle concentrations as surrogates of human exposures. However, considering that the concentration distribution of the indoor particulate matter is largely dependent on the extent to which these particles penetrate the building and on the degree of suspension in the indoor air, human exposures to particles of outdoor origin may not be equal to outdoor particle concentration levels. Therefore, it is critical to understand the relationship between the particle concentrations found outdoors and those found in indoor micro-environments. In this study, experiments were conducted using a naturally ventilated office located in Qingdao, China. The indoor and outdoor particle concentrations were measured at the same time using an optical counter with four size ranges. The particle size distribution ranged from 0.3 to 2.5 μm, and the experimental period was from April to September, 2016. Based on the experimental data, the dynamic and mass balance model based on time was used to estimate the penetration rate and deposition rate at air exchange rates of 0.03–0.25 h^?1. The values of the penetration rate and deposition velocity of indoor particles were determined to range from 0.45 to 0.82 h^?1 and 1.71 to 2.82 m/h, respectively. In addition, the particulate pollution exposure in the indoor environment was analyzed to estimate the exposure hazard from indoor particulate matter pollution, which is important for human exposure to particles and associated health effects. The conclusions from this study can serve to provide a better understanding the dynamics and behaviors of airborne particle entering into buildings. And they will also highlight effective methods to reduce exposure to particles in office buildings.     

A first generation dynamic ingress,redistribution and transport model of soil track-in: DIRT

This work introduces a spatially resolved quantitative model, based on conservation of mass and first order transfer kinetics, for following the transport and redistribution of outdoor soil to, and within, the indoor environment by track-in on footwear. Implementations of the DIRT model examined the influence of room size, rug area and location, shoe size, and mass transfer coefficients for smooth and carpeted floor surfaces using the ratio of mass loading on carpeted to smooth floor surfaces as a performance metric. Results showed that in the limit for large numbers of random steps the dual aspects of deposition to and track-off from the carpets govern this ratio. Using recently obtained experimental measurements, historic transport and distribution parameters, cleaning efficiencies for the different floor surfaces, and indoor dust deposition rates to provide model boundary conditions, DIRT predicts realistic floor surface loadings. The spatio-temporal variability in model predictions agrees with field observations and suggests that floor surface dust loadings are constantly in flux; steady state distributions are hardly, if ever, achieved. A contribution from ESF Center for the Urban Environment.     

Health risk assessment for arsenic contaminated soil

This paper describes risk assessment methods for two chronic exposure pathways involving arsenic contaminated soil, namely inhalation of fugitive dust emissions over a lifetime, and inadvertent soil/house dust ingestion. The endpoint in the first case is assumed to be lung cancer and in the second case skin cancer. In order to estimate exposures, inhalation rates and soil/dust ingestion rates are estimated for different age groups; indoor/outdoor time budgets for different age groups are developed; and indoor surface dust and air arsenic concentrations are estimated based on outdoor concentration measurements. Differences observed in indoor/outdoor ratios and arsenic containing dust particle size among different types of communities are noted, as well as possible relationship of particle size to bioavailability. Calculations of risk are presented using cancer potency factors developed by the U.S. Environmental Protection Agency, and uncertainties in these toxicity estimates are described based on: (1) evidence that arsenic may be neither a cancer initiator nor promotor, but may act instead as a late stage carcinogen and (2) evidence that the arsenic dose-response relationship for ingestion may be nonlinear at low doses due to increasing methylation of inorganic arsenic. The first of these considerations influences the relative importance ascribed to arsenic doses in different age groups. The latter consideration indicates that the risk estimates described here are probably very conservative.     

Particle size distributions, PM2.5 concentrations and water-soluble inorganic ions in different public indoor environments: a case study in Jinan, China

In this study, we collected particles with aerodynamic diameter ?2.5 μm (PM_2.5) from three different public indoor places (a supermarket, a commercial office, and a university dining hall) in Jinan, a medium-sized city located in northern China. Water-soluble inorganic ions of PM_2.5 and particle size distributions were also measured. Both indoor and outdoor PM_2.5 levels (102.3–143.8 μg·m^?3 and 160.2–301.3 μg·m^?3, respectively) were substantially higher than the value recommended by the World Health Organization (25 μg·m^?3), and outdoor sources were found to be the major contributors to indoor pollutants. Diurnal particle number size distributions were different, while the maximum volume concentrations all appeared to be approximately 300 nm in the three indoor locations. Concentrations of indoor and outdoor PM_2.5 were shown to exhibit the same variation trends for the supermarket and dining hall. For the office, PM_2.5 concentrations during nighttime were observed to decrease sharply. Among others, SO ₄ ^2? , NH ₄ ⁺ and NO ₃ ^? were found to be the dominant water-soluble ions of both indoor and outdoor particles. Concentrations of NO ₃ ^? in the supermarket and office during the daytime were observed to decrease sharply, which might be attributed to the fact that the indoor temperature was much higher than the outdoor temperature. In addition, domestic activities such as cleaning, water usage, cooking, and smoking also played roles in degraded indoor air quality. However, the results obtained here might be negatively impacted by the small number of samples and short sampling durations.     

Environmental health in minority and other underserved populations: Benign methods for identifying lead hazards at day care centres of New Orleans

This study tests the hypothesis that exterior sources of lead dust are more important than interior sources in the route of exposure of children. Benign field methods were used to distinguish between potential and actual lead exposure problems. Utilising hand wipe and surface wipe techniques, hand and environmental samples were obtained from selected day care centres at different locations within New Orleans. Previous research has shown that soil lead is determined by location within the city. Private and public day care centres were selected from inner and outer city areas to estimate the extent of hand lead exposure. To measure and identify the extent of environmental lead exposure, hand wipes were taken before and after playing outdoors. Results of preliminary findings show that outdoor lead dust is a more potent contaminant of hands than indoor lead dust. An association was found between the amount of lead on children's hands after playing outdoors and the lead content in the exterior dust and soil. Although two girls out of forty children had exceptionally high hand lead quantities after playing outdoors, in general, boys have higher hand lead levels than girls. The private inner-city day care centre had a severe contamination problem in its outdoor play area. By contrast, the outdoor play area of the public inner city day care centre is of such a high quality that the quantity of lead dust is independent of location in the city.     

Garden soil and house dust as exposure media for lead uptake in the mining village of Stratoni,Greece

The relationships between two exposure media, garden soil and house dust, were studied for Pb uptake in Stratoni village in northern Greece, an industrial area of mining and processing of sulphide ore. Lead data for the two media were assessed in terms of total and bioaccessible content, measurement and geochemical variability, and mineralogical composition. It was found that total Pb was enriched in house dust samples by a factor of 2 on average. Total Pb concentration in soil samples had a maximum of 2,040 mg/kg and reached a maximum of 7,000 mg/kg in house dust samples. The estimated variability due to measurement uncertainty was dominated by the sampling process, and the proportion of sampling variance was greater for soil samples, indicating a higher degree of Pb heterogeneity in soil on the given spatial scale of sampling strata. Although the same general spatial trend was observed for both sampling media with decreasing Pb concentration by increasing distance from the ore-processing plant, Pb in dust samples displayed the highest concentrations within a 300–600-m zone from the ore-processing facility. The significant differences which were observed in Pb speciation between the studied media were explained by differences in mineralogical composition of outdoor soil and indoor dust. Lead-enriched Fe and Mn oxides predominated in soil samples while fine galena grains (<10–20 μm diameter) were the major Pb-bearing phase in dust samples. The integrated exposure uptake biokinetic model was used to predict the risk of elevated blood lead levels in children of Stratoni. Model prediction indicated an average probability of 61 % for blood-Pb to exceed 10 μg/dl. The results underline the importance of house dust in risk assessment and highlight the effect of outdoor and indoor conditions on the fate of Pb in the particular environment of Stratoni.     

广州夏季办公室内细颗粒中多环芳烃污染特征研究

大部分的都市办公人群每天在办公室至少度过8 h。而室外环境的渗透、办公室内吸烟、办公设备使用和中央通风系统均可能导致细颗粒物及多环芳烃(PAHs)在室内积聚而造成微环境污染。2015年5—6月,在广州市3种不同功能区(商住区、高新产业区、工业区)共选取了14间不同类型的办公室,对其室内外PM_(2.5)和多环芳烃进行同步监测。结果表明,(1)14间中有12间办公室内的PM_(2.5)浓度水平高于世界卫生组织(WHO)的推荐值25μg·m-3;(2)与国内外类似研究相比,办公室内外∑16PAHs及Ba P-eq的监测浓度水平均较低,并呈现一致规律:文印>室外>吸烟>多人>单人>无窗(无人),其中Ba P-eq低于欧盟规定的安全限值1 ng·m-3;(3)文印工作和吸烟行为与室内PM_(2.5)和PAHs浓度升高有密切关系,分别对5环和4环PAHs贡献明显;(4)其他无明显内源的办公室的细颗粒中PAHs污染在监测期间主要来源于室外贡献。     

Indoor and outdoor air PBDE levels in a Southwestern US city

Levels of polybrominated diphenyl ether (PBDE) flame retardants have been increasing in humans and the environment for the past few decades. Human levels are markedly higher in the US than Europe. Although food appears to be a significant route of intake, food PBDE levels are not substantially higher in the US than Europe. House and office dust appear to be major routes of exposure with air believed to usually provide a lesser route of intake. Because there are very few measurements of airborne PBDE that have been performed in relevant microenvironments in the US, increased efforts to assess airborne PBDE in the US as sources of exposure are needed. This study reports, for the first time from a Southwestern US city in Texas, the results of measurements of airborne PBDE in multiple locations, two outdoor and six indoor (residential and office) from active air sampling with collection of a combination of both vapor- and particulate-phase PBDE. Higher PBDE levels were measured in indoor than outdoor air, which confirms previous findings. Of 11 measured congeners including BDE 209, total PBDE levels in two outdoor air samples were 112 and 125 pg m^?3 and the indoor air levels ranged from 175 to 1232 pg m^?3 with a median of 572 pg m^?3. These findings suggest that sources of air contamination with PBDE may be similar in Texas as elsewhere in North America. However, more sampling is required to (1) better determine if this is the case and (2) attempt to characterize potential sources of PBDE contamination in both indoor and outdoor air by analysis of congener patterns.     

Review: Windows of exposure to pesticides for increased risk of childhood leukemia

Leukemia is the leading cause of cancer resulting in mortality of children, and there is some evidence suggesting the increased incidence rate increasing during the recent decades. Limited human evidence indicates an increased risk of developing leukemia in childhood as a result of pesticide exposure, with possible significance of exposure occurring during the developmental periods including preconception, pregnancy, and childhood. This review examines the results of relevant literature on the timing of pesticide exposure and leukemia diagnosed in childhood. Results suggest that the risk from pesticide exposure seems to be greater during pregnancy. Other findings indicate that maternal occupational exposure may be more of a greater concern than the paternal occupational exposure; and that the residential indoor use of pesticides tends to result in higher risk estimates than the residential outdoor use. Only limited data are available on particular pesticides, genetic factors, critical windows of exposure during development, and their association with different histological types of leukemia.     

Pollution characteristics of particulate matters emitted from outdoor barbecue cooking in urban Jinan in eastern China

To understand the pollution characteristics of particulate matter emitted from outdoor barbecue cooking in eastern China, measurements of the PM_2.5 mass concentration, the number concentration of particles with a diameter of 0.01 to 1.0 μm, and the particle size distribution from 0.3 to 25 μm were carried out at seven barbecue restaurants in urban Jinan. The average PM_2.5 mass concentration and sub-micron particle number concentrations at a distance of 1 m from the grills were 250 to 1083 μg/m³ and 0.90 × 10⁵ to 2.23 × 10⁵ cm^–3, respectively, which were much higher than those in the ambient air of the urban area. Compared to the ambient atmosphere, barbecue cooking emitted very high levels of particles with a larger increase in the concentrations of super-micron particles than that of sub-micron particles. The super-micron particle number concentrations at the barbecue restaurants were 10 to 100 times higher than those observed in the ambient urban atmosphere. The barbecue smoke had a significant effect on the particle concentrations in the surrounding region. Both mass and number concentrations of particles exhibited maximum values immediately near the barbecue grills and often reached a peak at a distance of 10 to 15 m. The removal efficiency of a range hood for the cooking particles was tested in an indoor kitchen. The range hood effectively cleaned the particulate matter pollution caused by cooking with a removal efficiency larger than 80%. Therefore, the use of a range hood is recommended for outdoor barbecue restaurants coupled with a smoke purifier to clean the emitted high concentrations of particles.

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邻苯二甲酸二乙基己酯(DEHP)污染及其毒性研究进展

邻苯二甲酸二乙基己酯(DEHP)作为重要的增塑剂被广泛应用于涂料、食品包装、医疗器材、儿童玩具等产品中。研究表明DEHP在水、土壤、空气等各个环境要素以及食物、饮用水中已被普遍检出,并对环境产生潜在的危害。本文通过分析国内外DEHP的环境暴露和毒性效应的研究成果,总结了DEHP在室外大气、室内空气、土壤、地表水、地下水、食品和饮用水中的污染现状,并对DEHP的替代产品进行总结;此外,本文深入探讨了DEHP对水生生物和陆生生物的生态毒性效应,以及对生殖发育、肝脏、呼吸系统和神经系统等的健康毒性效应。最后,结合DEHP在环境暴露调查和毒性效应研究方面的不足,指出需要进一步加强我国DEHP的环境暴露调查,制定相关环境基准值与标准限值,开展慢性生态毒性效应和人体健康毒性效应等方面的研究。     

Do leaf-cutter ants Atta colombica obtain their magnetic sensors from soil?

How animals sense, process, and use magnetic information remains elusive. In insects, magnetic particles are candidates for a magnetic sensor. Recent studies suggest that the ant Pachycondyla marginata incorporates iron-containing particles from soil. We used leaf-cutter ants Atta colombica to test whether soil contact is necessary for developing a functional magnetic compass. A. colombica is the only invertebrate known to calculate a path-integrated home vector using a magnetic compass. Here, we show that A. colombica requires contact with soil to incorporate magnetic particles that can be used as a magnetic compass; yet, we also show that ants can biosynthesize magnetic particles. Workers from a soil-free colony ignored a 90° shift in the horizontal component of the geomagnetic field, yet oriented homeward despite the occlusion of any geocentric cues. In contrast, workers from a soil-exposed colony oriented to an intermediate direction between their true and subjective home in the shifted field. Homeward orientations under shifted fields suggest that ants calculated a path-integrated vector using proprioceptive information. Strikingly, ants from the soil-free colony also had magnetic particles; yet, as observed by ferromagnetic resonance, these particles differed from those in soil-exposed ants and were not associated with a magnetic compass sensitive to this experimental manipulation.     

武汉市秋冬季室内外空气颗粒物以及有机碳、元素碳的污染特征

为了解秋冬季室内外空气颗粒物PM10、PM2.5以及其有机碳和元素碳的污染特征,于2009年10月及12月对武汉大学医学部学生宿舍室内、外PM10、PM2.5进行了两周连续采样。结果表明：秋季室内PM10和PM2.5的平均浓度分别为121.8和91.3μg/m3,室外为153.9和104.2μg/m3;冬季室内PM10...     

Influences of suspended particles on the runoff of pesticides from an agricultural field at Askim, SE-Norway

Field and laboratory experiments were conducted to study the loss of particles from agricultural fields, and the role of suspended particles in carrying pesticides in surface runoff and drainage water. Propiconazole, a widely used fungicide was applied to experimental fields located at Askim, SE-Norway. Samples from surface runoff and drainage water were collected and analyzed for sediment mass, pesticides, particulate and dissolved organic carbon through a whole year. The surface soil and the runoff material were characterized by its particle size distribution, organic carbon content in size fractions and its ability to bind propiconazole. The results show that (1) particle runoff mostly occurred during the rainfall event shortly after harrowing in autumn. The highest particle concentration observed in the surface runoff water was 4600 mg l(-1), and in the drainage water 1130 mg l(-1); (2) the erosion of surface soil is size selective. The runoff sediment contained finer particle/aggregates rich in organic matter compared to its original surface soil; (3) the distribution coefficient (Kd) of propiconazole was significantly higher in the runoff sediment than in the parent soil. According to our calculation, particle-bound propiconazole can represent up to 23% of the total amount of propiconazole in a water sample with a sediment concentration of 7600 mg l(-1), which will significantly influence the transport behavior of the pesticide.     

Fluid motion and particle retention in the gill of Mytilus edulis: Video recordings and numerical modelling

Particle trajectories of 6.4m Latex spheres were recorded by video, both near an isolated blue mussel, Mytilus edulis, gill filament and, in place of an intact interfilamentary canal, in a model canal of width 200, 100 or 70m, formed by a transparent plate positioned next to a gill filament. Each arrangement was placed in a 2 x 10 x 10 cm test vessel filled with seawater. Serotonin (nerve-transmitter) stimulation was used to activate lateral cilia and to either lock latero-frontal cirri at the end of an active stroke (10^-5 M), or to activate them (10^-6 M), yielding lateral cilia beat frequencies of 19 and 16 Hz, respectively. With latero-frontal cirri locked, image analysis of particle tracks gave maximum velocities of ca. 2.9±0.2mm s^-1 close to the tips of lateral cilia, for both isolated filament and model canal cases. Experimental velocity profiles along the 200-m wide model canal were recorded and used as good approximations to the fluid velocity because of the low Reynolds number. A two-dimensional steady model was proposed for the gill pump, assumed to only comprise lateral cilia. This model was solved numerically for the experimental model, canal in the vessel and the results showed satisfactory agreement with experimental volocity profiles from particle tracks. The numerical approach was also applied to a model of a single interfilamentary canal in the vessel. The resulting mean velocity in the canal was 1.70 mm s^-1, but the resistance to flow in the model was less than that in an intact mussel gill. Video graphs of particle tracks indicated that active latero-frontal cirri play a role in the transfer of particles from through current to frontal current, probably by means of a strong interaction through the motion of intervening fluid rather than through a direct physical contact. M. edulis specimens used in the present study were collected in 1990 at Helsingør and in 1991 at Kerteminde, Denmark.     

Using multi-objective classification to model communities of soil microarthropods

In agricultural soil, a suite of anthropogenic events shape the ecosystem processes and populations. However, the impact from anthropogenic sources on the soil environment is almost exclusively assessed for chemicals, although other factors like crop and tillage practices have an important impact as well. Thus, the farming system as a whole should be evaluated and ranked according to its environmental benefits and impacts. Our starting point is a data set describing agricultural events and soil biological parameters. Using machine learning methods for inducing regression and model trees, we produce empirical models able to predict the soil quality from agricultural measures in terms of quantities describing the soil microarthropod community. We are also interested in discovering additional higher level knowledge. In particular, we have identified the most important factors influencing the population densities of springtails and mites and their biodiversity. We also identify to which agricultural actions different microarthropods react distinctly. To obtain this higher level knowledge, we employ multi-objective regression trees.     

Influences of Suspended Particles on the Runoff of Pesticides from an Agricultural Field at Askim, SE-Norway

Field and laboratory experiments were conducted to study the loss of particles from agricultural fields, and the role of suspended particles in carrying pesticides in surface runoff and drainage water. Propiconazole, a widely used fungicide was applied to experimental fields located at Askim, SE-Norway. Samples from surface runoff and drainage water were collected and analyzed for sediment mass, pesticides, particulate and dissolved organic carbon through a whole year. The surface soil and the runoff material were characterized by its particle size distribution, organic carbon content in size fractions and its ability to bind propiconazole. The results show that (1) particle runoff mostly occurred during the rainfall event shortly after harrowing in autumn. The highest particle concentration observed in the surface runoff water was 4600 mg l^–1, and in the drainage water 1130 mg l^–1; (2) the erosion of surface soil is size selective. The runoff sediment contained finer particle/aggregates rich in organic matter compared to its original surface soil; (3) the distribution coefficient (K _d) of propiconazole was significantly higher in the runoff sediment than in the parent soil. According to our calculation, particle-bound propiconazole can represent up to 23% of the total amount of propiconazole in a water sample with a sediment concentration of 7600 mg l^–1, which will significantly influence the transport behavior of the pesticide.