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Indoor allergen exposure plays a major role in the development of sensitization and triggering of asthma in children. All over the world, mites are common sources of indoor allergens. Risk levels for mite-allergen exposure have been recommended. A mite-allergen level of ≥2 μg/g dust is considered a risk level for sensitization and symptoms of asthma. Data from several ongoing prospective studies of children show that mite sensitization may occur below the suggested threshold level. However, from these studies, it seems that high mite-allergen exposure increases the risk of early sensitization, whereas low exposure levels probably take a longer time to induce Sensitization. Assessment of allergen exposure and consideration of allergen-elimination strategies should not be limited only to the home environment. High levels of mite allergens are also found in day-care centers, schools, and various other public places. such as bars. Thus, in addition to homes, these environments should also be considered when allergen-avoidance measures are taken. Allergen content in dust can be expressed in several units, e.g., ng/g, ng/m2, and ng/sampling, and as the total amount of allergen. At present, there is no consensus on the best way to measure and express mite-allergen levels. In this paper, aspects of threshold levels for mite sensitization, various exposure environments, and sampling, determination, and expression units of mite exposure will be discussed in brief. [ABSTRACT FROM AUTHOR]

This paper gives a faunistic review of mites that have been recorded in the indoor environment, particularly homes, barns, and stored products, in Norway and the other Scandinavian countries. Some preliminary results are given from unpublished investigations in Norway. Seven species of pyroglyphid mites have been recorded: Dermatophagoides pteronyssinus, D. microceras, D. farinae, D. evansi, Euroglyphus maynei, Gynsnogiyphus ion gior, and Hirstia chelidonis. D. pteronyssinus was the predominant species, followed by D. microceras in Scandinavia and D. farinae in Denmark. D. evansi was detected in poultry houses in Norway. Lepidoglyphus destructor was the predominant species in barn dust, but large populations of Acarus, Tyrophagus, Tydeus, and Tarsonemidae also occurred. In humid homes, Glycyphagus domesticus was found in high numbers. The result of quantification of mites depends on the method for examination of dust. When one proposes limits for the concentration of mites in relation to risk of allergic sensitization and provocation of symptoms. reference should be made to a well-described method for sampling and analyzing dust. The number of mites should be given per area, not only per weight unit of dust. The number of mites per area indicates the number of mites in the home. The number of mites per weight Unit of dust describes the concentration of mites in the vacuum cleaner. [ABSTRACT FROM AUTHOR]

The distribution and abundance of dust mites can be modelled on three scales: the microhabitat scale (different habitats within homes), the macrohabitat scale (between homes), and the regional scale. This paper focuses on the first. Those parts of a home in which dust mite populations thrive will tend to be homogeneous in respect of key habitat suitability determinants. The more widespread such determinants, the greater the risk of high mite populations and allergen load. Habitat suitability determinants include an adequate textile substratum, optimal temperature and humidity, and fond resources of appropriate quality, as well as other, currently unknown, requirements. Each determinant will have s characteristic distribution within any home, and they can be conceptualized as a series of overlays, or three-dimensional Venn diagrams, with the areas of overlap representing the most suitable sites for mite survival. That a population of dust mites is focused by constraining biotic and abiotic determinants means that spatial and temporal distribution and abundance are predictable, because the characteristics of the principal foci define optimal conditions for population growth. This concept, known as ‘focality’, provides a framework for prediction of sites of high density of mite population and allergen exposure, as well as a basis for manipulating the microenvironment for control purposes. [ABSTRACT FROM AUTHOR]

Several studies have shown a correlation between airborne pollutants and respiratory disorders. To determine whether professional exposure to industrial pollution might represent a risk factor for allergic respiratory diseases, we administered allergologic tests to 275 workers employed in a paper-making/printing factory and to a control population composed of 160 office workers from the same urban area. All subjects were evaluated on the basis of personal and family histories, the results of prick tests with common airborne allergens, specific serum IgE levels, pulmonary function test, and standard chest radiography. The percentage of subjects with allergies in the factory-worker group (67/275; 24.4%) was significantly higher than that observed among the office workers (20/160; 12.5%) (chi-square test: 8.17; P < 0.01). Of the 67 factory workers with allergies, 94% had histories of daily exposure to aliphatic hydrocarbons. The results of this study indicate that exposure to the latter type of industrial pollutants is associated with a significantly higher prevalence of allergic respiratory diseases.

RAST was performed using both nitrocellulose (NC) and paper discs to compare these solid supports for ability to detect IgE antibodies in sera from two patients with hypersensitivity to the industrial chemical, diphenylmethane-4,4'-diisocyanate (MDI). NC disc had distinct advantages in ease of coupling the hapten-conjugate antigen to discs, and in use of lesser amounts of antigen. With regard to sensitivity, NC discs were better able to distinguish the positive sera from 34 control sera including those with elevated levels of total IgE. In both RAST systems, inhibition studies indicated high specificity of antibodies for MDI, with no reactivity detected toward the serum albumin portion of the MDI-HSA conjugate antigen. However, only in the NC RAST did antibodies from both patients react with p-tolyl isocyanate inhibitor. Based on the above results, NC discs displayed several advantages in RAST and are recommended for routine serological assay of isocyanate-specific antibodies.