This presentation will review two major microbial cell wall agents (MCWA) - endotoxin and (1->3)-ß-D-glucan - concerning their toxic effects after inhalation and their role for the development of symptoms among persons in buildings with humidity problem.

Accurate and informative sampling methods are very important in the evaluation of fungalexposure in indoor air quality (IAQ) investigations. We have investigated the relationshipbetween indoor culturable airborne and dust-borne fungi and compared the performance ofculturable and non-culturable air samplersReuter Centrifugal Air Sampler (RCS) and ZefonAi-O-CellTM (AOC).

In buildings growing conditions for mould fungi can occur and cause fungus infestation. Thepossible danger for the occupants of dwellings lies in the production and spreading ofpathogens (disease causing agents). Therefore, consequent measures have to be taken to avoidhealth dangers that result from mould fungi in buildings. A strategy has to be set up thatfocuses on the growth conditions for mould fungi and also considers the complex transientprocesses of building physics.

Novel indoor air purification technology using ions generated by discharge plasma has beendeveloped. The effect of ions on airborne influenza virus has been investigated by the plaquemethod using MDCK cells and the hemagglutination test. It has been discovered that theseions can inactivate influenza virus in air world first. The infection rate of influenza virus toMDCK cells has been drastically reduced with the use of ions generated by the developeddevice. Furthermore the efficacy tests of these ions for polio virus and coxsackie virus havebeen performed.

A novel indoor air purification technology using ions generated by discharge plasma hasbeen developed. With the application of AC voltage between electrodes, dischargeplasma has been occurred and positively charged ions and negatively charged ions havebeen generated at atmospheric pressure. The chemical compositions of the ions have beenclarified to H + (H2O)m and O2 (H2O)n by time-of-flight mass spectroscopy.Bacteriostatic and fungistatic effects of these ions have been investigated.

Microclimates in moisture chambers and environment in houses were evaluated using afungal index. The index was calculated from the growth rate of a sensor fungus in a test piece,fungal detector, during an exposure period to the test environment. In the constant climates inthe moisture chambers, higher indices were obtained at higher relative humidity. In the roomswith higher fungal indices, the densities of airborne fungi were higher, indicating arelationship between the index and fungal contamination.

Microbial growth has been known as one of the major problems related to IAQ inresidential and commercial buildings. International and local standards define theupper limits of indoor relative humidity in order to avoid moisture related problems.However, setting limits on indoor relative humidity does not guarantee a mould-freeenvironment.

Japanese Building Maintenance Law defines that indoor humidity shall be maintained not lower than40%. But it is sometime very difficult to comply with the law. Indoor air humidifies in office buildingsmostly below 40% especially in wintertime. A request to deregulate the provision arises from HVACindustries. But a question concerning risk to deregulate the lower limit of humidity is arising.According to researches in 1960s, activity levels of influenza virus become higher when indoorrelative humidity becomes lower than 40%.

The aim was to study changes of symptoms and signs in an office exposed to flooding fromheavy rain. All 18 workers participated in medical investigations in January 1998. Thesubjects were first investigated on a Monday in a reference building and then all moved backand were reinvestigated in a damp building after 2 days of exposure.

A questionnaire on e.g. building characteristics including dampness, and allergic symptomsamong children from 8 918 homes was carried out in the year 2000. 18-24 months later, 6professional inspectors visited 390 of the homes and made inspections and measurements.Questionnaire reports on building characteristics, type of ventilation system, and buildingmaterials were in good agreement with observations from the inspectors (K=0.68-0.87). Individualkappa-values for the inspectors varied in the range of 0.33-0.96.