Gram Of Dust Research Articles

Characterization of human DNA in environmental samples

Environmental samples from indoor surfaces can be confounded by dust, which is composed largely of human skin cells and has been documented to contain roughly tens of micrograms of total DNA per gram of dust. This study complements previous published work by providing estimates of the quantity of amplifiable human DNA found in environmental samples from a typical indoor environment, categorized by the intensity of human traffic and visible quantity of dust. Dust was collected by surface swabbing standard 576 cm 2 areas in eight locations, and evaluated for total DNA quantity, presence of human DNA (mitochondrial and nuclear loci using conventional PCR), quantity of human nuclear DNA using quantitative PCR, and STR analysis. The total DNA content of 36 dust samples ranged from 9 to 28 ng/cm 2, and contained 0.2–1.1 pg/cm 2 of human DNA. Overall, human DNA was detected in 97% of 36 dust samples and 61% of samples yielded allele distributions of varying degrees of complexity when subjected to STR analysis. The implications of this study are twofold. First, the presence of dust in evidence can be a significant contamination source in forensic investigations because the human DNA component is of sufficient quality and quantity to produce allele calls in STR analysis. This can be effectively managed by implementing stringent protocols for collection and analysis of potential biological samples. A second implication is the use of dust as a source of evidence for identification of inhabitants within a defined location. In the latter case, a number of additional studies would be necessary to identify relevant pretreatments for environmental dust samples and to develop the necessary deconvolution techniques to separate the composite genotypes obtained.

Identificación de ácaros del polvo casero en colchones y almohadas de niños alérgicos de Santa Marta, Colombia

The increasing prevalence of allergic diseases in Colombia makes necessary to research about factors that influence their etiology. The aim of this study was to investigate the mite fauna present in homes of allergic child from Santa Marta. A total of 70 samples were collected from 42 houses through vacuuming mattresses and pillows, during the months of July to October 2007. Mites were identified under light microscopy using taxonomic keys, count and expressed as mites per gram of dust. The prevalent mite family was Pyroglyphidae (84.58%), having Dermatophagoides farinae as the major specie (23.85%), followed by D. pteronyssinus. Other mites prevalent were Cheyletus spp, Euroglyphus maynei and Blomia tropicalis, with levels up to 500 mites/ gram, considered like of high risk for the allergic sensitization. These results improve the knowledge of house dust mite fauna in Santa Marta, important by the diagnosis and therapy of allergies..

Comparative study of simple semiquantitative dust mite allergen tests

Two simple, commercially available and semiquantitative dust mite allergen tests, namely, the Acarex test(®) and Mitey Checker(®), were compared using 2 and 10 μg of Der 1 allergen per gram of dust, as evaluated by enzyme-linked immunosorbent assay (ELISA), to clarify which method is better suited for practical use. Mite allergen exposure levels of 106 floor, bed and sofa surfaces were evaluated by the Acarex test(®), Mitey Checker(®), and ELISA. A template of 100 cm×100cm was placed on the same surfaces to identify the examined areas. A dust collection filter was attached to a vacuum cleaner, and the area in the template (1 m(2)) was vacuumed. Then, to evaluate the other two tests, samples from the two other areas in the template (1 m(2)) that neighbored each other and did not overlap were vacuumed. To predict Der 1 levels of 2 μg/g dust or higher, the sensitivity and specificity of the Acarex test(®) were 100% and 13.3%, and those, of Mitey Checker(®) were 91.8% and 71.1%, respectively. To predict Der 1 levels of 10 μg/g dust or higher, the sensitivity and specificity of the Acarex test(®) were 50.0% and 96.2%, and those of Mitey Checker(®) were 85.7% and 79.5%, respectively. Compared with Der 1<2.0, 2.0-9.9.≥10.0 (μg/g dust), the percent agreement and kappa of the Acarex test(®) were 47.2% and 0.234, and those of Mitey Checker(®) were 70.0% and 0.505, respectively. To evaluate mite allergen exposure level for practical use in Japanese living environments, Mitey Checker(®) is better than the Acarex test(®) because of its higher sensitivity and specificity.

Thermodynamic analysis of the selective carbothermic reduction of electric arc furnace dust

Electric arc furnace (EAF) dust, which is produced as a result of the melting of automobile scrap in an electric arc furnace, contains considerable amounts of zinc and lead, which are of significant economic value. Typically, the other major components are iron oxide and calcium oxide with minor amounts of other metal oxides. In this research, a detailed thermodynamic study of the pyrometallurgical processing of the dust, using carbon as a reducing agent was performed. The SOLGASMIX solver of Outokumpu HSC Chemistry ® 5.1 was used to calculate the equilibrium composition under reducing conditions. The control input dust composition was as follows (in mass percent): 8.100% CaO, 8.250% 2CaO·SiO 2, 11.200% CaCO 3, 8.830% CaO·Fe 2O 3, 7.840% Fe 3O 4, 3.770% PbO, 38.150% ZnFe 2O 4 and 13.860% ZnO. Selective reduction and separation of both the zinc and the lead as metallic vapours, from the iron, in oxide form, was examined. The separation of the zinc or the lead from the iron, was defined quantitatively in terms of the selectivity factor (log β) as follows. for zinc β Zn / Fe = X Z n g X F e m Y F e o Y Z n o for lead β Pb / Fe = X P b g X F e m Y F e o Y P b o + l where the subscript symbols refer to the metal being present in gaseous (g), metallic solid (m), solid oxide (o) or metallic liquid (l) form, respectively. The standard calculations were performed for one hundred grams of dust at atmospheric pressure. The variables investigated were as follows; temperature in the range of 1273–1873 K, reactant ratio (i.e. moles of carbon per gram of dust), dust composition, addition of inert gas and reduced total pressure. The calculated values were in reasonable agreement with those from previously published studies and also industrial results.

Repeated measurements of mite and pet allergen levels in house dust over a time period of 8 years

Studies of the association between indoor allergen exposure and the development of allergic diseases have often measured allergen exposure at one point in time. We investigated the variability of house dust mite (Der p 1, Der f 1) and cat (Fel d 1) allergen in Dutch homes over a period of 8 years. Data were obtained in the Dutch PIAMA birth cohort study. Dust from the child's mattress, the parents' mattress and the living room floor was collected at four points in time, when the child was 3 months, 4, 6 and 8 years old. Dust samples were analysed for Der p 1, Der f 1 and Fel d 1 by sandwich enzyme immuno assay. Mite allergen concentrations for the child's mattress, the parents' mattress and the living room floor were moderately correlated between time-points. Agreement was better for cat allergen. For Der p 1 and Der f 1 on the child's mattress, the within-home variance was close to or smaller than the between-home variance in most cases. For Fel d 1, the within-home variance was almost always smaller than the between-home variance. Results were similar for allergen levels expressed per gram of dust and allergen levels expressed per square metre of the sampled surface. Variance ratios were smaller when samples were taken at shorter time intervals than at longer time intervals. Over a period of 4 years, mite and cat allergens measured in house dust are sufficiently stable to use single measurements with confidence in epidemiological studies. The within-home variance was larger when samples were taken 8 years apart so that over such long periods, repetition of sampling is recommended.

Upper-airway inflammation in relation to dust spiked with aldehydes or glucan

Organic dust is associated with adverse effects on human airways. This study was done to investigate whether the addition of beta-(1,3)-D glucan or aldehydes to office dust causes enhanced inflammation in human airways. Thirty-six volunteers were exposed randomly to clean air, office dust, dust spiked with glucan, and dust spiked with aldehydes. The three dust exposures contained between 332 and 379 microg dust/m(3). Spiking with 1 gram of dust was done with 10 milligrams of glucan or 0.1 microliters of aldehydes. Acoustic rhinometry, rhinostereometry, nasal lavage, and lung function tests were applied. After the exposures to dust spiked with the glucan and aldehydes, the nasal volume decreased (-1.33 and -1.39 cm(3) (mean), respectively) when compared with the -0.9 cm(3) after clean air or office dust (P=0.036 for a difference in decrease between exposures). After 2-3 hours the aldehyde-spiked dust caused a 0.6-mm swelling of the inferior turbinate, and glucan-spiked dust produced a 0.7-mm swelling (P=0.039 for a difference in the swelling between the four exposures). The preexposure nasal lavage cleaned off the mucosa, and lower cytokine concentrations were found after all of the exposures. For interleukin-8, this decrease in concentration was smaller after the dust exposures spiked with glucan and aldehydes (-2.9 and -25.8 pg/ml, respectively) than after office dust or clean air (-65.9 and -74.1 pg/ml, respectively) (P=0.042). The nasal eosinophil cell concentration increased after exposure to dust spiked with glucan (P=0.045). beta-(1,3)-D glucan and aldehydes in office dust enhance the inflammatory effects of dust on the upper airways.

Variation of biocontaminant levels within and between homes — the AIRALLERG study

Few epidemiological studies report on reliability of exposure measurements even though this significantly influences the results of correlation and regression analysis often used in these studies. Poor reliability of exposure measurement reduces the ability to detect a true association between a certain component and health outcome variables. The aim of this study was to determine the ratio of the within-home and between-home components of variance of a number of biocontaminants measured in house dust in the framework of an international study conducted in the Netherlands, Germany and Sweden (the AIRALLERG study). To this end, duplicate dust samples were collected from children's beds and from living room floors in over 100 homes. Samples were taken at the same point in time. Variables considered were the dust mass collected in mg/m2 and the concentrations of the house dust mite allergens Der p 1 and Der f 1, cat allergen Fel d 1, endotoxin, (1 --> 3)-beta-D-glucan and extracellular polysaccharides, all per gram of dust and per square meter of sampling surface. An analysis of variance showed that the within-home variance was small compared to the between-home variance for most variables (mostly less than half) with the exception of glucan on mattresses, when expressed in mug/g. Investigation of variation over time is needed for a more complete assessment of the use of these variables in epidemiological analyses of exposure-response relationships.

Clinical effectiveness of a mite allergen–impermeable bed-covering system in asthmatic mite-sensitive patients

Exposure to allergens plays a role in the development of bronchial hyperresponsiveness and in the chronic inflammatory response seen in asthmatic patients. House dust mites (HDMs) are an important source of allergen. Reduction of these allergens might lead to better lung function and reduction of asthma symptoms. The effect of HDM-impermeable covers on HDM allergen levels, peak flow values, and asthma symptoms were measured. Therefore a randomized clinical trial was carried out. Fifty-two allergic asthmatic patients were randomly allocated to use the HDM-impermeable or placebo covers. During the study period, daily peak flow and asthma symptom scores were recorded. Dust samples were taken from the mattresses. We observed a significant reduction in HDM allergen levels on the mattresses after encasing them with HDM-impermeable covers (reduction of 87% of Der p 1 in micrograms per gram of dust; P <.001). Baseline symptoms were so low that no improvement could be established. Morning peak expiratory flow is significantly higher in the intervention group compared with that seen in the placebo group during the study period (beta=20.2; P <.01). HDM-impermeable covers significantly decreased the level of HDM allergens. Furthermore, morning peak flow was significantly increased during the intervention period. This study indicates that HDM allergen-avoidance measures might have beneficial effects on allergen reduction and asthma outcome.

Dog allergen (Can f 1) and cat allergen (Fel d 1) in US homes: Results from the National Survey of Lead and Allergens in Housing

BackgroundExposures to dog and cat allergens are believed to play important roles in the etiology of asthma; however, the levels of these allergens have never been assessed in a representative sample of US homes. ObjectiveThe objective of this study was to estimate and characterize exposures to Can f 1 (dog allergen) and Fel d 1 (cat allergen) in US homes. MethodsData were obtained from the National Survey of Lead and Allergens in Housing, a nationally representative survey of 831 US homes. Vacuumed-collected dust samples from the bed, bedroom floor, living room floor, and living room sofa were analyzed for concentrations of Can f 1 and Fel d 1 (micrograms of allergen per gram of dust). ResultsAlthough a dog or cat had lived in only 49.1% of homes in the previous 6 months, Can f 1 and Fel d 1 were detected in 100% and 99.9% of homes, respectively. Averaged over the sampled sites, geometric mean concentrations (μg/g) were 4.69 for Can f 1 and 4.73 for Fel d 1. Among homes with an indoor dog and cat, respectively, geometric mean concentrations were 69 for Can f 1 and 200 for Fel d 1. Among homes without the indoor pet, geometric mean concentrations were above 1.0. The independent predictors of elevated concentrations in homes without pets were all demographic variables that were also linked to a higher prevalence of pet ownership. ConclusionsCan f 1 and Fel d 1 are universally present in US homes. Levels that have been associated with an increased risk of allergic sensitization were found even in homes without pets. Because of the transportability of these allergens on clothing, elevated levels in homes without pets, particularly among demographic groups in which pet ownership is more prevalent, implicate the community as an important source of these pet allergens.

Abatement of cockroach allergens (Bla g 1 and Bla g 2) in low-income, urban housing: Month 12 continuation results

Background In the first 6 months of this previously published, randomized trial, the combined intervention of occupant education, insecticide bait application, and professional cleaning significantly reduced cockroach numbers and Bla g 1 allergen levels in inner-city homes. Objective This continuation study investigated whether the cockroach allergen reductions achieved by month 6 could be maintained through month 12 with insecticide application alone. Methods Because we had agreed to place insecticide bait in control homes at the conclusion of the first study, intervention and control homes were treated with insecticide bait at months 6 and 9. No other intervention was conducted in either arm. Vacuumed dust and swab samples were collected at month 12. Twenty-one of the 31 original homes completed the 12-month study. Results Among the original intervention homes, Bla g 1 concentrations remained essentially unchanged from months 6 to 12. However, among the crossed-over control homes, the geometric mean Bla g 1 concentrations (Units per gram of dust) decreased from 287 to 14.4 for kitchen floors (95% reduction), from 28.8 to 5.6 for living room floors/sofas (81% reduction), from 26.7 to 4.7 for bedroom floors (82% reduction), and from 7.2 to 2.4 for beds (67% reduction). At month 12, Bla g 1 concentrations did not significantly differ between intervention and crossed-over control homes ( P > .64 at each location). Similar results were seen for the allergen Bla g 2. Conclusions Reductions in cockroach allergen concentrations achieved through the combined intervention of occupant education, insecticide application, and professional cleaning can be maintained with continued cockroach control. Surprisingly, and in contrast to other studies, insecticide application alone significantly lowered allergen concentrations in the crossed-over control homes. This unexpected result is being tested further in another randomized trial.

Mites in facilities for laboratory animals.

Two laboratory animal facilities were examined for storage and house-dust mites. Samples of settled dust or material were investigated microscopically, and all of the found mites were identified. Every fourth sample contained mites. On the average, 86 mites were found in a gram of dust. Measurement with a two-way enzyme-linked immunosorbent assay revealed only one sample containing a minor amount of allergen from Dermatophagoides pteronyssinus. It seems that, in addition to house-dust mites, other mites may be important occupational contaminants in animal facilities.

The role of dust in supplying nitrogen and phosphorus to the Southeast Mediterranean

This study assesses the role of the atmospheric dry fallout as a source of new nitrogen and phosphorus to the surface Levantine seawater. Leaching experiments of inorganic nitrogen (LINO3−, LINH4+) and phosphorus (LIPO4), using SE Mediterranean surface seawater, were performed on 41 aerosol (hereafter dust) samples collected on Whatman 41 filters between April 1996 and January 1999 at Tel Shikmona, Israel and on four desert‐event dust powder samples. A geometric mean of 2.8 and 3.2 mmol NO3− and NH4+ per gram of dust was leached by seawater from normal (background) dry deposition captured by the filters. Significantly lower amounts of IN with lower NH4+:NO3− ratios were leached from both the 1 2 filters and the dust powder sampled during dust events (mean of 0.18 and 0.02 mmol NO3− and NH4+ per gram of dust). Similarly, relatively lower values of LIPO4 were measured in desert type events, attributed to systematic decrease in IP solubility with increased rock/soil component. The calculated LINO3− and LINH4+ fluxes were 34 and 20 mmol m−2 yr−1 from normal dry deposition, 2.5 higher than the wet IN deposition, and twice the riverine input (23 mmol m−2 yr−1, Guerzoni et al.). This high ratio is due to the semiarid climate in this basin. The estimated flux of total dry IP was 1 mmol P m−2 yr−1, approximately 3 times higher than the input of wet IP and somewhat lower than the estimated riverine input (1.4 mmol m−2 yr−1, Guerzoni et al. 1999). The similarity of atmospheric and burial fluxes of P in the Levantine basin reinforces the hypothesis that the atmosphere is the dominant source of P to the sediments in the deeper parts of the basin. It was estimated that the leachable fluxes of IP and IN (dry 1 wet) can support between ~15 or ~70% (1–4 g C m−2 yr−1) of the new production in the SE Mediterranean, effective mainly during dust events and stratification. This input may contribute significantly to the relatively high N: P ratios in Levantine deep water (~27).

Experimental methodologies and preliminary transfer factor data for estimation of dermal exposures to particles.

Developmental efforts and experimental data that focused on quantifying the transfer of particles on a mass basis from indoor surfaces to human skin are described. Methods that utilized a common fluorescein-tagged Arizona Test Dust (ATD) as a possible surrogate for housedust and a uniform surface dust deposition chamber to permit estimation of particle mass transfer for selected dust size fractions were developed. Particle transfers to both wet and dry skin were quantified for contact events with stainless steel, vinyl, and carpeted surfaces that had been pre-loaded with the tagged test dust. To better understand the representativeness of the test dust, a large housedust sample was collected and analyzed for particle size distribution by mass and several metals (Pb, Mn, Cd, Cr, and Ni). The real housedust sample was found to have multimodal size distributions (mg/g) for particle-phase metals. The fluorescein tagging provided surface coatings of 0.11-0.36 ng fluorescein per gram of dust. The predominant surface location of the fluorescein tag would best represent simulated mass transfers for contaminant species coating the surfaces of the particles. The computer-controlled surface deposition chamber provided acceptably uniform surface coatings with known particle loadings on the contact test panels. Significant findings for the dermal transfer factor data were: (a) only about 1/3 of the projected hand surface typically came in contact with the smooth test surfaces during a press; (b) the fraction of particles transferred to the skin decreased as the surface roughness increased, with carpeting transfer coefficients averaging only 1/10 those of stainless steel; (c) hand dampness significantly increased the particle mass transfer; (d) consecutive presses decreased the particle transfer by a factor of 3 as the skin surface became loaded, requiring approximately 100 presses to reach an equilibrium transfer rate; and (e) an increase in metals concentration with decreasing particle size, with levels at 25 microns typically two or more times higher than those at 100 microns--consistent with the earlier finding of Lewis et al. for the same sample for pesticides and polycyclic aromatic hydrocarbons (PAHs).

Allergenic materials in the house dust of allergy clinic patients.

Environmental agents including animal, fungal, tree, and weed antigens are known to cause allergic rhinitis and asthma. The following study was performed to measure the antigen concentration of several of these in house dust of children seen in an allergy clinic. Comparisons are made between household allergen levels of children seen for asthma and children seen for other reasons. Dust samples were solicited from patients in a pediatric allergy specialty clinic and other individuals associated with the clinic. Persons submitting dust were asked to complete a questionnaire describing their house. Samples were extracted, centrifuged, and filtered for sterility. Samples were stored in 50% glycerol at -20 degrees C. Specific antigens for Alternaria, Cladosporium, Aspergillus, Candida, Dermatophagoides farinae, cat, dog, oak, fescue, ragweed, plantain, and cockroach were measured using inhibition assays developed with whole antigen extract. Allergens Der p1, Der f 1, Alt a 1, and Alt a 70 kD were measured using double monoclonal antibody assays. Significant concentrations of whole antigen from cat, dog, oak, Alternaria, and Cladosporium were detected. Between 0.1 and 18 microg of Der f1 and Der p1 per gram of dust were also measured. Alt a 1 and Alt a 70 kD levels varied between 3.0 and 1000 U/g of dust. Significant positive correlations were observed in levels of dust mite and Alternaria allergen for patients with an evaluation of asthma. We found measurable levels of fungal antigens (Alternaria, Cladosporium), mite antigens, and animal antigens (dog and cat) in the majority of dust samples in this self-selected set of allergy clinic patients. Specific allergens Alt a 1, Alt a 70kD, and Der p 1 were significantly higher in the homes of asthmatic patients when compared with patients seen for reasons other than asthma. These studies support the hypothesis that fungal allergen exposure is an important component in the pathogenesis of the clinical condition known as asthma.

B(1-&gt;3)-Glucan in House Dust of German Homes: Housing Characteristics, Occupant Behavior, and Relations with Endotoxins, Allergens, and Molds

beta(1-->3)-Glucans are potent proinflammatory agents that have been suggested to play a role in indoor-related respiratory health effects. The aim of this study was to assess whether beta(1-->3)-glucan concentrations in house dust are correlated with levels of endotoxins, allergens, and culturable mold spore counts in house dust. Further, the associations of beta(1-->3)-glucan with housing characteristics and occupant behavior were assessed. beta(1-->3)-Glucan was measured in settled house dust from living room floors of 395 homes of two German cities, Erfurt and Hamburg, with a specific enzyme immunoassay. Concentrations ranged from below the limit of detection to 19,013 microg/m(2) (22,588 microg/g dust). Concentrations per square meter were found to be correlated with endotoxins, mite and cat allergens, and culturable mold spores. Correlations were weaker when concentrations were expressed per gram of dust, indicating that variance in concentrations of all factors is largely determined by the amount of dust sampled. Associations between beta(1-->3)-glucan, housing characteristics, and occupant behavior were found for concentrations per square meter but not for concentrations per gram of dust. The following characteristics were associated with a significant increase in beta(1-->3)-glucan levels: carpets in the living room [means ratio (MR) = 1.9-2.1], keeping a dog inside (MR = 1.4), use of the home by four or more persons (MR = 1.4), use of the living room for > 180 hr/week (MR = 2.1), lower frequency of vacuum cleaning (MR = 1.6-3.0) and dust cleaning (MR = 1.2 and 1.4, respectively), and presence of mold spots during the past 12 months (MR = 1.4). We conclude that that the amount of dust sampled can be used as a proxy for hygiene and that beta(1-->3)-glucan concentrations per square meter are related to the amount of dust sampled.

Beta(1-->3)-glucan in house dust of German homes: housing characteristics, occupant behavior, and relations with endotoxins, allergens, and molds.

beta(1-->3)-Glucans are potent proinflammatory agents that have been suggested to play a role in indoor-related respiratory health effects. The aim of this study was to assess whether beta(1-->3)-glucan concentrations in house dust are correlated with levels of endotoxins, allergens, and culturable mold spore counts in house dust. Further, the associations of beta(1-->3)-glucan with housing characteristics and occupant behavior were assessed. beta(1-->3)-Glucan was measured in settled house dust from living room floors of 395 homes of two German cities, Erfurt and Hamburg, with a specific enzyme immunoassay. Concentrations ranged from below the limit of detection to 19,013 microg/m(2) (22,588 microg/g dust). Concentrations per square meter were found to be correlated with endotoxins, mite and cat allergens, and culturable mold spores. Correlations were weaker when concentrations were expressed per gram of dust, indicating that variance in concentrations of all factors is largely determined by the amount of dust sampled. Associations between beta(1-->3)-glucan, housing characteristics, and occupant behavior were found for concentrations per square meter but not for concentrations per gram of dust. The following characteristics were associated with a significant increase in beta(1-->3)-glucan levels: carpets in the living room [means ratio (MR) = 1.9-2.1], keeping a dog inside (MR = 1.4), use of the home by four or more persons (MR = 1.4), use of the living room for > 180 hr/week (MR = 2.1), lower frequency of vacuum cleaning (MR = 1.6-3.0) and dust cleaning (MR = 1.2 and 1.4, respectively), and presence of mold spots during the past 12 months (MR = 1.4). We conclude that that the amount of dust sampled can be used as a proxy for hygiene and that beta(1-->3)-glucan concentrations per square meter are related to the amount of dust sampled.

Reducing relative humidity is a practical way to control dust mites and their allergens in homes in temperate climates

Background: Maintaining a relative humidity (RH) of less than 50% is one recommendation for reducing numbers of house dust mites and their allergens in homes. Objective: The purpose of this study was to determine whether, in a humid temperate climate, indoor RH could be sufficiently lowered to control dust mites and their allergens. Methods: During a period spanning 2 humid summers (May 1998 to October 1999), dust mite and allergen densities were determined in 3 groups of homes. One group (low RH group, n = 23) maintained an RH of less than 51%. Most of these homes used a high-efficiency dehumidifier and air conditioning. A second group of homes (group A) used air conditioning only (n = 19) or air conditioning and dehumidification (n = 5) but did not maintain an RH of less than 51%. A third group of homes (group C, n = 24) controlled climate by opening windows and had an RH of greater than 51%. Normal housecleaning was maintained in all homes during the study. Results: The low RH group homes started in June with a mean ± SE of 401 ± 124 live mites and 17 ± 3 μg of total Der 1 allergen per gram of dust. After 17 months of maintaining an RH of less than 51%, these declined significantly to 8 ± 3 live mites per gram (P = .004) and 4 ± 1 μg of Der 1 per gram of dust (P < .001). In contrast, group A and C homes exhibited seasonal peaks of 500 to 1000 mites and 40 to 70 μg of Der 1 per gram of dust. At all time points after the baseline sample, the low RH group homes had significantly less (P < .001) allergen than the group A and C homes. After 17 months, allergen levels were more than 10 times lower in low RH homes compared with humid homes. Conclusion: This study showed that it is practical to maintain an indoor RH of less than 51% during the humid summer season in a temperate climate, and this resulted in significant reductions in mite and allergen levels. (J Allergy Clin Immunol 2001;107:99-104.)

In-Flight Plasma Reduction of Electric Arc Furnace Dust in Carbon Monoxide

In a typical electric arc furnace (EAF) operation for melting iron-containing scrap, approximately 1 to 2% of the charge is converted into dust which is collected in the baghouse. These EAF dusts have been classified as hazardous wastes due to their lead, cadmium and hexavalent chromium contents; however, these dusts also contain large quantities of zinc and iron whose recovery is economically attractive. In the present work, a high zinc-containing EAF dust was processed in-flight using a 24 kVA AC plasma arc furnace in a carbon monoxide (CO(g)) atmosphere. The volatile elements were collected in a condenser and the remaining elements formed a slag phase. The degree of zinc removal, RZn, was determined as a function of the three operating parameters: reactor temperature (°C), EAF dust feed rate (g/min) and reactant ratio (grams of dust per litre of CO(g)). Increased process temperatures resulted in an increased recovery of zinc to the condensate. An optimum reactant ratio was found at about 4.5 grams of dust per litre of CO(g). In general, the degree of lead removal from the EAF dust, RPb, was found to be approximately equal to that of zinc. Under all the processing conditions, the cadmium in the dust was found to be totally recovered in the condensate.Lors de l'opération typique d'un four à arc (EAF) pour la fonte de rebut contenant du fer, approximativement 1 à 2% de la charge est convertie en poussière qui est récupérée par l'unité de filtration. Ces poussières du four à arc ont été classées comme déchets dangereux à cause de leur contenu en plomb, en cadmium et en chrome hexavalent; cependant, ces poussières contiennent également de grandes quantités de zinc et de fer dont la récupération est économiquement intéressante. Dans le présent travail, on a traité, en vol, de la poussière de four à arc ayant un contenu élevé en zinc, en utilisant un four à arc-plasma de 24 kVAAC dans une atmosphère de monoxyde de carbone (CO(g)). On a récupéré les éléments volatiles dans un condenseur et les éléments qui restaient ont formé une phase de scorie. On a déterminé le degré d'enlèvement du zinc, RZn, en fonction de trois paramètres d'opération: température du réacteur (°C), taux d'alimentation de la poussière de four à arc (g/min) et proportion de réactant (grammes de poussière par litre de CO(g)). Une augmentation de la température de traitement résultait en une augmentation de la récupération du zinc dans le condensat. On a trouvé qu'une proportion optimale de réactant était d'environ 4.5 grammes de poussière par litre de CO(g). En général, on a trouvé que le degré d'enlèvement du plomb de la poussière de four à arc, RPb, était approximativement égal à celui du zinc. Sous toutes les conditions de traitement, on a trouvé que le cadmium de la poussière était complètement récupéré dans le condensat.

Abundance of house dust mites in relation to climate in contrasting agricultural settlements in Israel.

The correlation between climatic conditions and mite numbers in houses from rural areas was studied in 13 agricultural communities (kibbutzim and moshavim) in nine geo-climatic subregions of Israel. Mites were present in 97% of the dust samples. The average number of mites per gram of dust in the different localities ranged between 84 and 2053. The maximum number of mites (7440/g dust) was found in a carpet from a house in Geva Carmel in the northern coastal region. The most prevalent species of mites were Dermatophagoides pteronyssinus and Dermatophagoides farinae, which were found in 85.6% and 71.3% of the samples, respectively. The house dust mites D. pteronyssinus, D. farinae and Euroglyphus maynei constituted 94.8% of the mites. Most of the mites were isolated from the carpets and sofas (37.0% and 33.7%, respectively), and a smaller number from beds (29.3%). The smallest number of mites (< or = 250/g dust) were found at a minimum relative humidity (RH) of 30% and lower, with a maximum temperature of 32 degrees C and higher, i.e. in the Jordan valley and Negev mountains. A greater number of mites (250-500/g dust) were found at a minimum ambient RH of 35-40% and a maximum temperature of 32 degrees C and higher, i.e. the Hula valley. A large number of mites (500-1000/g dust) were found at a minimum RH of 35-40% with a maximum temperature of 30 degrees C and lower, i.e. in the Judean and Samarian range, as well as in upper Galilee. The largest number of mites (1000-2000/g dust) was found at a minimum RH of 45% and higher, with a maximum temperature ranging between 30 and 32 degrees C. These conditions occur in the coastal strip, the coastal plain and in the Judean and Samarian foothills. A monthly examination of two houses in Zova, a kibbutz in the Judean hills next to Jerusalem, and two houses from Palmachim, a kibbutz in the coastal region, revealed that the highest prevalence of mites was found in the months April-November and May-November, respectively. In Zova, the highest number of mites were found during the months of June and July while the highest concentrations of D. pteronyssinus-antigen (Der p I) were measured during the month of September. A positive correlation between mite numbers and the quantity of Der p I in house dust was found.

Exposure of submarine personnel to house dust mite allergens

House dust mite (HDM) allergens play an important role in the pathogenesis of perennial allergy and bronchial asthma. There is broad consensus that assessment of exposure to HDM allergens is mainly based on measurements of allergen concentrations in dust and that the “threshold” level for sensitization in atopic children is approximately 2000 ng of group I allergen (sum of Der p 1 and Der f 1) per gram of dust.1,2 Many data are available about exposure to HDM allergens for persons in private homes and public buildings (eg, schools and day care centers) but hardly any for military personnel at their places of duty. In this article we present the results of a pilot study of HDM allergens in German submarines.