ONESNAŽENJE V STANOVANJU

V zadnjih desetletjih so v industrijsko razvitih državah zasledili zaskrbljujočo rast alergijskih obolenj. Onesnaženje v stanovanjih ima pri tem primarno vlogo. V istem časovnem razdobju , se je prebivalstvo začelo zadrževati več v lastnih stanovanjih, katera so toplotno izolirana in zatesnjena, zaradi energetskemu varčevanju. Z uporabo sodobnih tehnik gradnje in dvojne zasteklitve, postajajo naša stanovanja bolj vlažna. S tem smo ustvarili idealno okolje za širitev pršic, plesni in gob.

During the last few decades, many countries have experienced an increase in the prevalence and severity of asthma. Over the same period, the population in the developed world has retreated indoors, and homes have become better insulated and more energy efficient, resulting in a warm and humid environment with low ventilation rates, ideally suited to house-dust-mite population growth throughout the year. Increasing exposure and increasing sensitivity to indoor allergens represent a progressively higher risk factor for the development of asthma. The development of sensitivity to indoor allergens and the symptoms and severity of asthma in later childhood are directly related to the exposure to allergens in infancy. It was relatively straightforward to demonstrate a quantitative linear dose-response relationship between exposure to house-dust-mite allergens and subsequent sensitization. However, showing the same for exposure and asthma severity has been more difficult, as the relationship between exposure and asthma symptoms in already sensitized individuals is much more complex than in the case of exposure and sensitization. Nevertheless, sensitized individuals are likely to have more severe asthma if exposed to high allergen levels than if their level of exposure is low. Sensitization to house-dust mites is a major independent risk factor for asthma in all areas where climate is conducive to mite population growth. The relevance of allergens other that mite is not consistent between different areas, and depends on the climate, habits, and socio-economic features of the local community. It would appear that presence of mite allergens in homes "overshadows" other allergens (e.g., cat, dog, or cockroach) as a risk factor for sensitization and subsequent development of allergic disease. It is possible that this is the consequence of the difference in inherent potency between allergen sources, and the question of why mite allergens are so potent in inducing sensitization and atopic disease remains to be answered.

Izvleček iz: Custovic A, Simpson A, Woodcock A. Importance of indoor allergens in the induction of allergy and elicitation of allergic disease. Allergy 1998; 53 (suppl 48): 115-120.
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We inescapably share our homes with numerous microscopic life forms. These organisms - arthropods, fungi, bacteria, etc. - share many of our needs and preferences and consume what we provide, either in the form of our own shed skin scales and other biological excreta, or rich organic materials (preferably damp) in the fabric and furnishings of the buildings we inhabit. Increasingly we keep our "gardens-homes" warm and moist all year round; it keeps us comfortable and our commensals thriving. Indeed, our homes are generally so comfortable that we are content to spend a very large proportion of our time there; for some people this can-be 90% or more. Of course, sometimes the home construction is faulty or resources are limited so that the home is not just moist, from condensation for example, but becomes structurally damp. This can result in the marked and noticeable proliferation of particular organisms. The presence of our various cohabitants has come to be associated with a variety of detrimental impacts on health and well-being. We now know that house dust mites, which love to share our beds, pillows, chairs and carpets, produce a potent allergen, Der p 1 . Exposure to this leads to sensitization and can exacerbate or possibly cause one of the principal diseases of current public health concern: asthma.

Izvleček iz: Harrison P.T.C. Creature comforts - living with mites and moulds. Clinical and Experimental Allergy 1999; 29: 148-149.

Danes, večina ljudi preživi 90% časa v stanovanju. V zadnjih 30 letih se je naše stanovanje zelo spremenilo. Oblazinjeno pohištvo, itisoni in preproge, centralno ogrevanje.

Prezračevanje se je zmanjšalo: izmenjava zraka je danes 10 krat manjša kakor pred 30 leti, kar ima za posledico povečanje vlažnosti in prisotnost škodljivih snovi ter alergenov.

Nowadays most people spend more than 90% of their lives indoors. Over the past 30 years, the home environment has changed enormously with the introduction of soft furnishings, fitted carpets, and central heating. Indoor ventilation has decreased - the rate at which indoor air is exchanged for fresh air is now 10 times lower than it was 30 years ago - with a considerable increase both in humidity and in concentrations of indoor pollutants and airborne allergens. As exposure to allergens is an important cause of symptoms in sensitised patients, reducing exposure should improve disease control. In spite of this, few patients in Britain with asthma, eczema, or perennial rhinitis, or any combination of these, are skin tested.

Izvleček iz: Woodcock A, Custovic A. Avoiding exposure to indoor allergens. BMJ 1998; 316: 1075-1078.

Pomembnost prezračevanja prostorov v povezavi z prisotnostjo pršice , je bila potrjena v treh skandinavskih raziskavah, enotne so v tem da populacija pršič narašča eksponentno z zmanjšanjem prezračevanja zaradi energetskega varčevanja. Na danskem se je poraba energentov za ogrevanje zmanjšala za 30 % v obdobju od 1972 do 1984. Dve raziskavi na danskem o prisotnosti pršice v naključno izbranih stanovanjih, sta pokazali da je v letu 1977 samo v 23 % stanovanj bil dosežen nivo 100 pršic/g prahu, 9 let kasneje, je bil ta nivo presežen v 82 % stanovanj.

The crucial importance of building ventilation in relation to the occurrence of house-dust mites has been confirmed by three different Scandinavian studies, all showing an exponential increase in the occurrence of house-dust mites with decreasing ventilation. Over the last 25 years, accelerating after the energy crisis of 1973, in an effort to save heating energy, the building of dwellings in Western Europe and elsewhere has been expedited by the extensive use of large preformed elements, as well as the use of thermal-insulated double-glazed windows and extensive sealing of the building envelope. The possible effects of this change in building style and character have been investigated. In Denmark, the national reduction in overall use of heating energy fell by more than 30% from 1972 to 1984. Two different surveys on the occurrence of house-dust mites in dwellings randomly selected from the general Danish population showed that in 1977 only 23 % of dwellings had a concentration of mites above the threshold limit value of 100 mites/g dust, while 9 years later, 82% of randomly chosen Danish dwellings had a concentration of house-dust mites in mattress dust above 100/g dust. It was similarly believed that in 1977 the Stockholm area was without significant occurrence of house-dust mites, and extracts of house-dust mites were not included in the standard panel for skin testing. A decade later, Wickman documented an occurrence of significant quantities of house-dust mites in about 30% of Stockholm dwellings.

Izvleček iz: Korsgaard J. Epidemiology of house-dust mites. Allergy 1998; 53 (Suppl 48): 36-40.

Obdržati nivo relativne vlage pod 50%, znižuje število pršic.
Maintaining indoor humidity below 50%, will reduce mite allergen.

Izvleček iz: Ad Hoc Working group on Environmental Allergens and Asthma. Environmental allergen avoidance in allergic asthma. J Allergy Clin Immunol 1999; 103: 203-5.

Mnoge raziskave so dokazale povezavo med vlago v stanovanju in koncentracijo alergenov pršic v njem. Nizek nivo alergenov so zasledili v stanovanjih z nizko relativno vlažniostjo prostorov. To je ohrabrujoče, saj bi z znižanjem vlažnosti prostorov dosegli znižanje alergenov.

Many studies have shown a significantly positive correlation between the air humidity in the home and the concentration of mite allergens in the house dust. Within a single city, homes may be found that contain very high concentration of dust-mite (exceeding 50 mg of Der p 1/g dust), whereas other homes have only clinically insignificant amounts (<1 mg/g). Low allergen levels are usually associated with low humidity of indoor air. This association is often statistically significant. This is encouraging; perhaps through reducing air humidity, low allergen levels can be achieved. It is not surprising that many authors regard humidity as the key factor in controlling house-dust-mite allergens.

Izvleček iz : de Boer R. Reflections on the control of mites and mite allergens. Allergy 1998; 53 (Suppl 48): 41-46.

Znižanje vlage v prostoru na zelo nizek nivo (celo 0% RV) za kratek čas, ne prizadene pršice. V kolikor želimo prizadeti populacijo pršic, moramo obdržati RV konstantno (tedne) pod nivojem CEH ( kritično ravnovesje vlažnosti).

Reducing air humidity to very low levels (even 0%) for a short period, will not affect mite survival. In order to destroy a dust-mite population, it is much more important to ensure that the RH remains continuously below the CEH, even if only slightly so. Izvleček iz: de Boer R. Reflections on the control of mites and mite allergens. Allergy 1998; 53 (Suppl 48): 41-46.

Izvleček iz : Hart BJ. Life cycle and reproduction of house-dust mites: environmental factors influencing mite populations. Allergy 1998; 53 (Suppl 48): 13-17.

Vgradnja cenenih klimatskih naprav v stanovanjih brez ustreznega odvoda vlage, ima za posledico povečanje populacije pršic.

The technological development in warmer areas in the last two decades has led to an increased use of air conditioning to achieve higher human thermal comfort. Table 4 shows an example of the consequences of air conditioning on temperature and humidity in warm climates. It appears that the maintenance of low humidity with air cooling would imply air cooling to 8°C to achieve dehumidification to a RH below 45%, as compared to the normal 16°C (the lowest possible air temperature to deliver incoming air to a room without the feeling of draft by the room's inhabitants). However, air conditioning with sufficient dehumidification is very expensive. On the other hand, widespread and uncritical introduction of air conditioning without sufficient dehumidification for private homes in warmer parts of the world could have serious consequences in the establishment of temperature and humidity conditions extremely favourable to the survival and growth of house-dust mites.

Tabela 4
Example of effects of air conditioning (air cooling) on indoor air humidity. If maximum indoor air humidity of 45% relative humidity is wanted, this first implies cooling of incoming air to 8°C with rewarming to avoid draft. Secondly, this low level of indoor air humidity would entail large dehumidification with removal of more than 15 l per h (example B). In contrast (example A), usual air cooling to 16°C leads to very humid indoor air which would favour mite growth. Example has been calculated for Seville (Spain) with mean outdoor air temperature in summer of 27°C and mean relative humidity of 57%. Desired indoor air temperature was set to 20°C in house of 100 m2 with volume of 250 m3. Needed air-exchange rate to keep temperature down was set to 10 ach.