A screening assessment of emissions of volatile organic compounds and particles from heated indoor dust samples

This paper characterizes and compares emissions during heating of different dust samples relevant to the indoor environment. Characterization includes emission of volatile organic compounds when dust samples were heated to 150 and 250 degrees C (gas chromatograph-mass spectrometer), weight loss during heating to 450 degrees C (thermogravimetric analysis), and the number of particles emitted during heating towards 200 degrees C (condensation nucleus counting). Element analyses were performed for non-heated dust (inductively coupled plasma discharge instrument). Emissions of volatile organic compounds from heated dust from different sources were surprisingly similar. However, the temperature at which the emission of volatiles started varied with the dust source. For most of the samples studied, the emissions were considerable already at 150 degrees C, and increased in number of peaks and peak area at 250 degrees C. Particle emissions started around 70 degrees C regardless of the dust source. Particle emissions seemed to be affected by the content of organic material.     

Lead and cadmium composition in indoor dust

Pb and Cd levels in different size fractions of indoor dust have been analyzed by differential pulse anodic stripping voltammetry (DPASV) after digestion with HNO₃ and HF using a microwave oven. The relationship between Pb and Cd levels with dust size have been investigated and the metal levels in different sources of indoor dust are compared. In addition, the Pb and Cd composition in different size fractions of dust have been investigated by a sequential extraction method. Dusts are dominated by particulate matter < 500 μm. Pb levels in office dust in the particulate fraction > 75 μm are clearly shown to be higher than that in domestic dust. Generally, for domestic premises, Pb and Cd levels increase with a decrease in the particle size and with an increase in house age, while for office dust, the Pb level increases with an increase of particle size. For domestic houses, most of the metals are bound to carbonate and FeMn oxides in fine dust. For office dust, the situation is more complicated, with a clear increase in Pb in the organic and residue fractions in coarse dust.     

Inflammatory and allergic responses to airborne office dust in five human provocation experiments

Five studies on the effects of dust have been published from The Department of Environmental and Occupational Medicine, the University of Aarhus, Denmark. These five studies support that exposures to normal office dust for up to 5 h at concentration ranges occasionally seen in non-occupational indoor environments may cause health effects which can be measured both objectively and subjectively in healthy subjects and subjects with different types of hypersensitivity. In these five studies, the lowest observed effect level was indicated to be 75 microg/m3 (total suspended particulates). However, dust from different buildings may have different toxicity and some of the five studies had higher No Observed Effect Level (NOEL) than this value. The studies give strong evidence that dust exposures cause decreased tear film stability or break-up time and increased number of eosinophil cells in nasal lavages. There is also strong evidence that general well-being decrease during exposures. This is also reflected in increasing general irritation in eyes, nose, and throat. The combined findings support the theory that the subjects' responses to indoor dust exposures are caused by sensory perceptions, weak allergic, or weak inflammatory responses at or in the exposed tissues. More than one biological mechanism may be involved at the same time or subsequently. No signs of effects in non-exposed organs or tissues were seen, not even in sensitive persons. PRACTICAL IMPLICATIONS: The studies indicate that dust exposures indoors may explain many reported symptoms and health effects and underlines the importance of source reduction.     

House dust induces IL-6 and IL-8 response in A549 epithelial cells

The in vitro potency of house dust to induce cytokine response in A549 lung epithelial cells was studied. Dusts collected from carpet, bed, shelf and floor of a villa and an apartment by vacuuming were found to trigger the production of interleukin-8 (IL-8) and interleukin-6 (IL-6) in a dose-dependent manner, and the interleukin production was several-fold higher than of swine dust (used as a positive control). The IL-8 and IL-6 production of pure Escherichia coli lipopolysaccharide was significantly lower than of the dusts and a peptidoglycan-polysaccharide complex did not show any stimulatory effect at all. The lipopolysaccharide and peptidoglycan contents of the samples were determined by gas chromatography-tandem mass spectrometry analysis of, respectively, 3-hydroxy fatty acids and muramic acid; in addition, ergosterol was monitored for fungal biomass. The inflammatory properties of house dust upon inhalation may be reflected in its high potency to induce cytokine response in lung epithelial cells.     

A multi-element profile of housedust in relation to exterior dust and soils in the city of Ottawa, Canada

This paper presents multi-element profiles of indoor dust versus exterior soils and dusts from 50 residences located in 10 neighborhoods across Ottawa, the capital city of Canada. Mercury concentrations were determined using nitric-sulphuric acid digestion and cold vapor AAS. Concentrations of 31 other elements were determined using nitric-hydrofluoric acid digestion and ICP-MS. Comparisons of household dust, garden soil and street dust at the individual residence scale and at the community scale were based on a consistent 100-250-microm particle size fraction. Results showed housedust samples to contain significantly higher concentrations of many key elements, including lead, cadmium, antimony and mercury, than either street dust or garden soil samples. Also, housedust profiles revealed a distinct multi-element signature in relation to exterior dust and soil samples. Interestingly, garden soil contained higher concentrations of aluminum, barium and thallium than either house or street dust. Geometric mean concentrations (mg/kg) of these elements in household dust/garden soil were: lead 233/42; cadmium 4.42/0.27; antimony 5.54/0.25; mercury 1.728/0.055; aluminum 24281/55677; barium 454/763; and thallium 0.14/0.29. Street dust contained lower geometric mean concentrations than garden soil for 23 out of a total of 32 elements. In general, indoor/outdoor concentration ratios varied widely from one element to another, and from one residence to another within the community. In the case of Ottawa, which is a city with a low concentration of heavy industries, it would be difficult-to-impossible to accurately predict indoor dust concentrations based on exterior soil data. It is concluded that dust generated from sources within the house itself can contribute significantly to exposures to certain elements, such as lead, cadmium, antimony and mercury.     

Linear alkylbenzene sulfonates in indoor floor dust

A method was developed to analyse linear alkylbenzene sulfonates (C10-C13 LAS) in vacuumed floor dust in office buildings by the use of HPLC chromatography. Floor dust was sampled with a specially designed vacuum cleaner and fractionated into fibres and particles. The content of LAS in the particle fraction of floor dust sampled from seven different public buildings varied between 34 microg LAS g(-1) dust and 1,500 microg LAS g(-1) dust, while the content of the fibre fractions was generally higher with up to 3,500 microg LAS g(-1) dust. The use of a cleaning agent with LAS resulted in increases approximately 30% of the amount of LAS in the floor dust after floor wash relative to just before floor wash. However, the most important source of LAS in the indoor floor dust appeared to be residues of detergent in clothing. Thus, a newly washed shirt contained 2,960 microg LAS g(-1) clothing. The analysis of the office dust samples indicated that LAS (and probably other detergents) might be of importance for the indoor environment.     

Surface dust contamination and perceived indoor environment in office buildings

The purpose of the study was to evaluate the impact of cleaning on indoor environment quality. Surface dust contamination and occupants' perception of the work environment factors and symptoms were the parameters studied. Six multi-floor office buildings were selected. Dust contamination on surfaces was sampled with gelatine foils and quantified using a BM-Dustdetector. Occupants' perceptions of the environment were assessed with modified MM-40 questionnaires. The results indicated that each building had its own surface dust contamination profile. Weekly cleaning maintained the surface dust contamination at the highest acceptable level for indoor environments. The occupants and their activities have a major effect on the level of dust particle contamination on desks. The correlation between the perceived surface dust contamination and the level of satisfaction with cleaning was as expected. Furthermore, surface dust contamination appeared not to be associated with work-related symptoms. PRACTICAL IMPLICATIONS: The results provide information about current program for contractors and clients, e.g. appropriate cleaning intervals of different surfaces, and the influence of disorder on result. After the evaluation of surface dust contamination levels, it will be possible for cleaning companies to focus on the most important surfaces to clean in order to enhance the quality of the indoor environment in office buildings. This should lead to future development work, which will require cooperation between contractors, clients, and research scientists. In office environments where high cleanliness is required, objective measurements (with instruments) are needed in addition to subjective measurements (the perceptions of occupants). It is essential to evaluate the efficiency of cleaning programs regularly with effective and appropriate quality-monitoring methods.     

北京四合院可吸入颗粒物浓度测试分析

本文测定了北京四合院内4户人家室内空气中可吸入颗粒物的计数浓度,分析了粒径分布,并考察了影响四合院室内可吸入颗粒物污染的不同因素。实验表明,空气内可吸入颗粒以细颗粒为主,粒径小于2.5μm的颗粒物占97%以上,煤球炉是四合院内空气中可吸入颗粒物污染的重要来源。     

家用空气源热泵热水器的设计

介绍了家用空气源热泵热水器的工作流程,研究了目前国内市场上3种家用空气源热泵热水器——户内整体机、户内分体机、户外分体机的结构。分析了空气源热泵热水器的设计要点。     

粒径对中密度纤维板粉尘爆炸特性影响实验研究

为探究粒径对中密度纤维板粉尘爆炸及相关特性的影响,采用20 L爆炸球、粉尘云最低着火温度装置、锥形量热仪和哈特曼管装置,对不同粒径粉尘的爆炸下限、最大爆炸压力、最低着火温度、热释放速率和火焰传播规律进行研究。结果表明,随着粉尘粒径减小,爆炸下限和粉尘云最低着火温度降低,最大爆炸压力逐渐增大;粉尘燃烧过程分为升温、着火、过渡、加剧和熄灭5个阶段,并出现2个峰值,热释放速率变化时间和吸热时间随着粒径减小而增加,热释放速率峰值增大;火焰在管道内的传播随着粒径减小先增强后减弱,管道外“火球”形状更大,火焰消散后火星数量变少,火焰尾端更加细长。     

Occurrence of endocrine-disrupting chemicals in indoor dust

Human exposure to indoor dust enriched with endocrine-disrupting chemicals released from numerous indoor sources has been a focus of increasing concern. Longer residence times and elevated contaminant concentrations in the indoor environment may increase chances of exposure to these contaminants by 1000-fold compared to outdoor exposure. To investigate the occurrence of semi-volatile endocrine-disrupting chemicals, including PBDEs (polybrominated diphenyl ethers), PCBs (polychlorinated biphenyls), phthalates, pyrethroids, DDT (dichlorodiphenyltrichloroethane) and its metabolites, and chlordanes, indoor dust samples were collected from household vacuum cleaner bags provided by 10 apartments and 1 community hall in Davis, California, USA. Chemical analyses show that all indoor dust samples are highly contaminated by target analytes measured in the present study. Di-(2-ethylhexyl)phthalate was the most abundant (104-7630 microg/g) in all samples and higher than other target analytes by 2 to 6 orders of magnitude. PBDEs were also found at high concentrations (1780-25,200 ng/g). Although the use of PCBs has been banned or restricted for decades, some samples had PCBs at levels that are considered to be concerns for human health, indicating that the potential risk posed by PCBs still remains high in the indoor environment, probably due to a lack of dissipation processes and continuous release from the sources. Although the use of some PBDEs is being phased out in some parts of the U.S., this trend may apply to PBDEs as well. We can anticipate that exposure to PBDEs will continue as long as the general public keeps using existing household items such as sofas, mattresses, and carpets that contain PBDEs. This study provides additional information that indoor dust is highly contaminated by persistent and endocrine-disrupting chemicals.     

Concentration of atmospheric particulates during a dust storm period in central Taiwan, Taichung

In this study we monitored concentrations of particles in central Taiwan using PS-1 (GPS1 PUF Sampler) and Model 310 Universal Air Sampler (UAS) from 02/23/2001 to 03/12/2001 at two sampling sites. During this period, an Asian dust storm moved across central Taiwan from 3/3 to 3/6. The total ambient air particle concentrations during the dust storm period were than compared with previous data from this region. In general, the average total suspended particulate (TSP) concentration order was during dust storm period > after dust storm period > non-dust storm period at both HKITT (traffic) and THUC (rural) sampling sites. The ratio of PM2.5/PM10 was 60% before and after the dust storm period. However, this ratio was decreased to less than 50% during the dust storm. This demonstrates that the coarse particulate concentrations (PM2.5-10) increased during the dust storm period. In contrast the increase of ambient air particles concentrations after the Taiwan Chi-Chi Earthquake were mainly due to fine particles (PM2.5). And, the increased of ambient air particles concentrations after dust storm period were mainly coarse particle (PM2.5-10) concentrations in central Taiwan.     

Review of methods to collect settled dust and isolate culturable microorganisms

Examination of settled dust is often included in investigations of indoor environments to identify the types and concentrations of particles to which building occupants may be exposed. Fungi and bacteria are among the many components in dust that have been studied. Isolation by culture is an established method that is used widely to quantify and identify microorganisms in environmental samples. However, no standard procedures for culturing fungi or bacteria from dust have been adopted widely to ensure the validity of comparing findings from different studies. This paper reviews methods various researchers have used to study surface particles and to isolate culturable microorganisms from dust. Factors that were found to differ included the method of sample collection, the ways dust was prepared for inoculation onto growth media, and the culture media chosen for specific categories of agents. The need for reference methods in environmental microbiology for use in the assessment of indoor environmental quality is discussed.     

Determining source strength of semivolatile organic compounds using measured concentrations in indoor dust

Consumer products and building materials emit a number of semivolatile organic compounds (SVOCs) in the indoor environment. Because indoor SVOCs accumulate in dust, we explore the use of dust to determine source strength and report here on analysis of dust samples collected in 30 US homes for six phthalates, four personal care product ingredients, and five flame retardants. We then use a fugacity‐based indoor mass balance model to estimate the whole‐house emission rates of SVOCs that would account for the measured dust concentrations. Di‐2‐ethylhexyl phthalate (DEHP) and di‐iso‐nonyl phthalate (DiNP) were the most abundant compounds in these dust samples. On the other hand, the estimated emission rate of diethyl phthalate is the largest among phthalates, although its dust concentration is over two orders of magnitude smaller than DEHP and DiNP. The magnitude of the estimated emission rate that corresponds to the measured dust concentration is found to be inversely correlated with the vapor pressure of the compound, indicating that dust concentrations alone cannot be used to determine which compounds have the greatest emission rates. The combined dust‐assay modeling approach shows promise for estimating indoor emission rates for SVOCs.     

Determinants of house dust endotoxin in three European countries - the AIRALLERG study

The comparison of endotoxin levels between study populations and countries is limited as a result of differences in sampling, extraction, and storage procedures. The objective of this study is to assess the levels and determinants of endotoxin in mattress and living room floor dust samples from three European countries, namely, Germany, the Netherlands, and Sweden, using a standardized sampling, storage, and analysis protocol. The mattress and living room floor dust was collected from the homes of 1065 German, Dutch, and Swedish (pre-)school children. All the samples were collected in the cool season and analyzed for endotoxin in a central laboratory. The determinants were assessed by a standardized questionnaire. The endotoxin concentrations in mattress and living room floor dust were found to be the highest in German homes and lowest in the Swedish ones. Differences between the geometric means were small (factor 1.1-1.7). Most of the associations between endotoxin concentrations and potential determinants were not statistically significant and heterogeneous across countries. However, keeping pets and having more than four persons living in the home were consistently associated with up to 1.7-fold higher endotoxin concentrations in mattress and floor dust. Furthermore, having carpets or rugs, and opening the windows frequently was associated with up to 3.4-fold and 1.3-fold higher endotoxin concentrations in living room floor dust, respectively. The proportion of variance explained by the questionnaire variables was generally low. In conclusion, the data on housing characteristics did not accurately predict the endotoxin concentrations in house dust, and could only partly explain the differences between countries. PRACTICAL IMPLICATIONS: The differences between the endotoxin concentrations in German, Dutch, and Swedish homes are small. House dust endotoxin concentrations are associated with a number of housing factors, such as pet-ownership, floor cover, number of persons living in the home, and ventilation. The variability of the endotoxin levels between homes and countries can only be partly explained by these factors.     

Indoor and outdoor PM2.5 and PM10 concentrations in the air during a dust storm

Asian dust storms (ADS) originating from the arid deserts of Mongolia and China are a well-known springtime meteorological phenomenon throughout East Asia. The ventilation systems in office utilize air from outside and therefore it is necessary to understand how these dust storms affect the concentrations of PM_2.5 and PM₁₀ in both the indoor and outdoor air. We measured dust storm pollution particles in an office building using a direct-reading instrument (PC-2 Quartz Crystal Microbalance, QCM) that measured particle size and concentration every 10 min for 1 h, three times a day. A three-fold increase in the concentrations of PM_2.5 and PM₁₀ in the indoor and outdoor air was recorded during the dust storms. After adjusting for other covariates, autoregression models indicated that PM_2.5 and PM₁₀ in the indoor air increased significantly (21.7 μg/m³ and 23.0 μg/m³ respectively) during dust storms. The ventilation systems in high-rise buildings utilize air from outside and therefore the indoor concentrations of fine and coarse particles in the air inside the buildings are significantly affected by outside air pollutants, especially during dust storms.     

Assessment of human exposure to indoor organic contaminants via dust ingestion in Pakistan

Ingestion of indoor dust has been acknowledged as an important route of exposure to organic contaminants (OCs). We investigated the presence of polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), organophosphate flame retardants (OPFRs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) in indoor floor dust from rural homes (N=31) and mosques (N=12) in Gujrat, Pakistan. Low concentrations were observed for most contaminants. OPFRs were the principle contaminants, with tri-(2-butoxyethyl)-phosphate (TBEP) and tri-phenyl-phosphate (TPP) having medians of 66 and 109 ng/g, respectively. PBDEs were only minor constituents in the investigated samples, with BDE 209 (median 40 ng/g) being the most important congener. Levels and profile of ∑PBDEs, ∑NBFRs, ∑HCHs, ∑DDTs, and ∑PCBs revealed no difference (P<0.05) between samples of dust from homes and mosques, indicating similar emission sources. Exposure scenarios using 5th percentile, median, mean, and 95th percentile levels were estimated for both adult and toddlers. Typical high-end, using median levels and high dust ingestion, exposure for adults were 0.02, 0.02, 0.03, <0.01, and 0.65 ng/kg bw/day and for toddlers 0.39, 0.45, 0.69, 0.01, and 15.2 ng/kg bw/day for ∑PBDEs, ∑NBFRs, ∑OCPs, ∑PCBs, and ∑OPFRs, respectively. To the authors' knowledge, this is the first study to document the presence of indoor OCs in Pakistani dust. PRACTICAL IMPLICATIONS: This is the first report on the analysis of various contaminants in indoor dust from Pakistan. Some of these chemicals are currently being used in different consumer products. The study will help to further an understanding of the levels of different organic contaminants (OCs) in Pakistani indoor environments and will enlighten the generally ignored area of environmental pollution in Pakistan. Furthermore, studies based on animal models have shown that some of the analyzed chemicals can cause different types of chronic toxicities. However, our results showed that the levels of estimated exposure via dust ingestion for all chemicals were several orders of magnitude lower than their reference dose (RfD) values or than those reported in studies from Belgium, China, Singapore, and the UK (Ali et al., 2011a; Harrad et al., 2008; Tan et al., 2007a,b; Van den Eede et al., 2011a; Wang et al., 2010).     

The effect of mineralogy, texture and mechanical properties of anti-skid and asphalt aggregates on urban dust

In northern latitudes mineral dust is formed when cars use studded tyres and roads are sanded to obtain more traction on the icy surfaces. Anti-skid and asphalt aggregates with different textural, mineralogical and mechanical properties were tested with an indoor road simulator fitted with studded and friction tyres. The particle size distribution and proportions of dust from pavement and anti-skid aggregate were analyzed using SEM-EDX. The wear on the road pavement depends on the properties of the anti-skid and asphalt aggregate (particle size distribution, mechanical/physical and textural properties). Anti-skid aggregates, which contain mainly hard minerals (e.g. feldspars and quartz) and which have a low resistance to fragmentation, should be used with caution as they may break more easily into smaller particles and are likely to wear the pavement. By using high-quality anti-skid aggregates it is possible to reduce the amount of urban dust.     

The influence of soil remediation on lead in house dust

Lead in house dust has long been recognized as a principal source of excess lead absorption among children at the Bunker Hill Superfund Site (BHSS) in northern Idaho. House dust lead concentration from homeowner's vacuum cleaner bags has been monitored since the epidemic of childhood lead poisoning in 1974. Geometric mean house dust lead concentrations decreased from >10000 mg/kg in 1974 to approximately 4000 mg/kg in 1975, in response to air pollution control initiatives at the defective primary lead smelter. After smelter closure, 1983 mean dust lead concentrations were near 3000 mg/kg and were most dependent on soil sources. Following emergency soil removals from public areas and roadsides and fugitive dust control efforts in the mid-1980s, house dust lead decreased by approximately 40-60% to 1200-1500 mg/kg. In 1992, a cleanup goal of 500 mg/kg dust lead community average, with no individual home exceeding 1000 mg/kg, was adopted. This goal was to be achieved by a combination of contaminated soil removals and fugitive dust control efforts throughout the 21 square mile BHSS. Continual reductions in house dust lead concentrations have been noted throughout the residential area soil cleanup. Geometric mean house dust lead concentrations averaged approximately 500-600 mg/kg from 1996 to 1999 and dropped below 500 mg/kg in 2000. Analysis of these data indicates that approximately 20% of the variance in dust lead concentrations is attributed to yard, neighborhood, and community soil lead concentrations. Since 1996, dust lead concentrations and dust and lead loading rates have also been measured by dust mats placed at entryways into the homes. Neighborhood soil lead concentrations, household hygiene, the number of adults living in the home, and the number of hours a child spends outdoors in summer explain approximately 26% of the variance in mat dust lead loading rates. It is estimated that post-remedial house dust lead concentrations will stabilize at 400-500 mg/kg, as compared to approximately 200 mg/kg in socio-economically similar background communities; the difference possibly attributed to residual soil concentrations (3-6 times background), recontamination of rights-of-way, tracking of non-residential mining district soils and dusts, fugitive dusts associated with the remediation, and residual structural or carpet dusts.     

Phosphorus flame retardants in indoor dust and their relation to asthma and allergies of inhabitants

Organophosphate esters are used as additives in flame retardants and plasticizers, and they are ubiquitous in the indoor environment. Phosphorus flame retardants (PFRs) are present in residential dust, but few epidemiological studies have assessed their impact on human health. We measured the levels of 11 PFRs in indoor floor dust and multi‐surface dust in 182 single‐family dwellings in Japan. We evaluated their correlations with asthma and allergies of the inhabitants. Tris(2‐butoxyethyl) phosphate was detected in all samples (median value: 580 μg/g in floor dust, 111 μg/g in multi‐surface dust). Tris(2‐chloro‐iso‐propyl) phosphate (TCIPP) was detected at 8.69 μg/g in floor dust and 25.8 μg/g in multi‐surface dust. After adjustment for potential confounders, significant associations were found between the prevalence of atopic dermatitis and the presence of TCIPP and tris(1,3‐dichloro‐2‐propyl) phosphate in floor dust [per log₁₀‐unit, odds ratio (OR): 2.43 and 1.84, respectively]. Tributyl phosphate was significantly associated with the prevalence of asthma (OR: 2.85 in floor dust, 5.34 in multi‐surface dust) and allergic rhinitis (OR: 2.55 in multi‐surface dust). PFR levels in Japan were high compared with values reported previously for Europe, Asia‐Pacific, and the USA. Higher levels of PFRs in house dust were related to the inhabitants' health status.