SYTTY
MOULD AND MOISTURE TRANSFER IN BUILDING STRUCTURES AND BUILDINGS WITH PARTICULAR REGARD TO THE PREVENTION OF HEALTH HAZARDS
Project leader: Olli Seppänen, Helsinki University of Technology,
HVAC-Laboratory, P.O.Box 4100, FIN-02015 HUT, Finland,
tel. +358-9-451 3600, fax: +358-9-451 3611, e-mail: Olli.Seppanen@hut.fi
| PUBLICATIONS |
| TIIVISTELMÄ SUOMEKSI |
| DETECTION OF PREVIOUS EXPOSURE OF WET-DAMAGE MICROBES WITH AN IgG-AVIDITY, ENDOTOXIN AND TOXICITY ASSAY |
Researchers:
Jarek Kurnitski, Helsinki University of Technology, HVAC-Laboratory,
tel. +358-9-451 3609, e-mail: Jarek@cc.hut.fi
Miimu Matilainen, Helsinki University of Technology, HVAC-Laboratory,
tel. +358-9-451 4742, e-mail: Miimu.Matilainen@hut.fi
Pertti Pasanen, University of Kuopio, Department of Enviromental Sciencies,
tel. +358-17-163 157, e-mail: Pasanen@uku.fi
Anne Korpi and Vesa Asikainen, University of Kuopio, Department of
Enviromental Sciencies
Helena Mussalo Rauhamaa, Helsinki University Central Hospital, Departments
of Dermatology and Allergic Diseases,
tel. +358-9-1912 7545, e-mail: Mussalo@helsinki.fi
Peter Elq, Helsinki University Central Hospital, Departments of Dermatology
and Allergic Diseases and Clinical Chemistry,
tel. +358-9-4718 6423, e-mail: Peter.Elg@hyks.fi
Financing SYTTY-organization: TEKES
KEY WORDS : Mould, moisture, health, crawl space, ventilation
EXTENDED ABSTRACT
The project was divided into four tasks. In the following the objectives and the main results of each task are reported.
1 Mould growth on building materials
Moisture and mould problems causing serious health effects are found both in old as well as new buildings. Viability of fungal colonies on building materials depends on the characteristics of the material, humidity and temperature. This report deals with the main limiting factors of mould growth (temperature and humidity), the growth qualifications on common building materials, and the effect of varying humidity conditions on fungal growth and viability. The time needed for the initiation of fungal growth can be estimated with mathematical models. In addition, this report includes a list of microbially produced volatile organic compounds (MVOC) on different building materials.
The most important moisture parameter when microbial growth is considered, is water activity (or relative humidity, RH) of the substrate instead of moisture content of the material. When assessing the risk of mould growth, one short term measurement of humidity is not adequate, but prolonged observation of both relative humidity and temperature is suggested. When moisture measurements are performed in crawl space, the adequacy of air exchange needs to be evaluated.
When the relative humidity of the material is high (>75 % RH), the risk of mould growth exists within the temperature range from 5 to 35 °C. The higher the RH and temperature, the faster the mould growth. Thus, high relative humidity of a material is acceptable only for short periods of time or during cold season. There is no risk of mould growth if the prevailing conditions endure for a shorter period than that needed for the initiation of mould growth in given conditions, which can be estimated with the equations cited in this report. In certain situations, conditions even in the moisture-technically properly designed constructions may be favourable for mould growth, which however, does not presuppose repairs.
MVOC do not derive solely from active microbial growth, but are released into the air also from the (M)VOC adsorbed on materials, or merely materials which have become wet. Thus, mere MVOC measurements cannot be used when searching for mould damages.
2 Crawl space types and building physics
In the task different types of crawl spaces are given and their physical behaviour including heat, moisture and air change was discussed. The objective was to collect information on the behaviour of crawl spaces, especially concerning moisture control and optimum air change. In addition, the results of the project are given in form of preliminary guidelines for crawl spaces.
The behaviour of ordinary crawl spaces ventilated naturally or mechanically by outdoor air as well as heated crawl spaces, unventilated crawl spaces and crawl spaces ventilated by indoor air are discussed. Preliminary guidelines are given for crawl spaces ventilated by outdoor air. Ground moisture evaporation and the crawl space temperature are the most critical factors affecting the moisture behaviour of a crawl space. If the ground moisture evaporation is not reduced by ground covers, the humidity of the crawl space will rise over the limits of mould growth. Properties of ground covers and calculation methods to assess moisture evaporation are given. Air change will affect both humidity and temperature in crawl space. The need of air change is discussed based on results from previous and the present research and some guidelines for optimum ventilation are given.
The given guidelines are specific and include the control of roof-, surface- and ground water as a part of crawl space design. The guidelines are preliminary and will be revised in the second stage of the project. Publishing of preliminary guidelines is considered to be useful, as even a small improvement of the current situation might be a notable step ahead towards properly functioning crawl spaces.
3 Crawl space moisture and microbes
Decreasing the humidity in crawl spaces with ground covers and dehumidifier was tested and microbiological conditions were measured. The aim of the study was to test the behaviour of lightweight aggregate (LWA) and crushed stone ground cover and dehumidifier by field measurements and computer simulations. Another objective was to measure microbe-concentrations in crawl spaces and to find out, are the microbes and VOCs drifted from crawl spaces to apartments by leakage air flows through base floor. Field measurements of temperature and humidity behaviour were carried out during 10 months in six crawl space of apartment building and day care centre with wooden or stone base floor. The effect of air change and ground covers on crawl space humidity was studied by computer simulations. Mould and VOC-concentrations were measured from air and material samples in winter and summer.
LWA reduced effectively ground moisture evaporation. Used layers with 10-20 cm thickness cut the capillary rise completely, in the middle of the layer the relative humidity was about 85% and on the surface almost the same as in the crawl space air. Crushed stone that was used as reference for LWA did not cut the capillary rise, the moisture rose on the surface of crushed stone, where relative humidity was continuously over 90%. Thus, it is extremely important that the proper crushed stone, washed crushed stone without fine fraction, will be used in crawl spaces. The humidity of crawl space was possible to reduce effectively by dehumidifier. Used device was sufficient for the crawl space with 200 m2 area. Dehumidifier should be installed in the way that air circulation everywhere in the crawl space is brought about.
Relative humidity of the crawl space with wooden well-insulated base floor was in the summer highest, on the level of limit values for mould growth. Reducing humidity by ground cover only was not sufficient measure, since temperature in the crawl space was low (13-15ºC) and outdoor air became act as moisture source. Monthly averages of the relative humidity exceeded the 80%-level in the summer.
The effect of ground cover is based by the results on reducing the evaporation and insulating heat capacity of the massive ground. Crawl space will warm up faster in the summer if ground is insulated. Air change 0.5 ach is fully sufficient in the heating season and in the case of stone-structures over year round. In the case of well insulated wooden base floor, for increasing temperature in the summer, air change has to be increased to 3-5 ach during May-September.
Mould concentrations in crawl spaces were some thousands cfu/m3, that is more than ten times higher than concentrations accepted in indoors. Materials in crawl spaces showed high fungal contamination. In the measured apartments and in one day care centre the high mould concentrations were reflected as risen concentrations in the indoor air especially in the winter. There were under-pressure compared to crawl space in the apartments equipped with mechanical exhaust ventilation and evident reason for risen mould concentration was intake air sucked from crawl spaces.
Increasing temperature in crawl spaces in the summer by insulating massive ground and constructions and by adding air change rate will be especially studied in the second stage of the research.
4 Health studies
The aim of the study was to develop a new serum IgG avidity test in order to estimate the exposure to moulds for cross-sectional and follow-up studies. There is a shortage of good laboratory parameters to verify accurately an exposure to moulds in wet-damaged houses.
Selection of patients and reference persons
A selection of patients was done at the Clinic for Indoor Air Health
Problems. This clinic was established at the Helsinki University
Central Hospital, Departments of Dermatology and Allergic Diseases, in
1995. Patients selected for this study were examined by the staff physician.
In addition, a specially trained environmental inspector from the
clinic visited the homes of these patients and collected material samples
from the water damaged structures and surfaces. In the mycological
laboratory of Helsinki University Central Hospital different mould genera
were isolated and identified from these samples. In total 7 houses
inhabited by the patients from this clinic were examined. The condition
(e.g. dampness and ventilation) of three of them were also
investigated by the environmental inspector of the clinic in co-operation
with experts from the Technical High School and Kuopio University.
In addition, 19 workers from the day care center Matari
located in the Helsinki area participated in the study. Investigations
of Matari day care center are presented in detail elsewhere
in this report. As a reference group 12 laboratory workers from the
Helsinki University Central Hospital were examined.
Clinical examination
Health condition was examined for all the residents, whose houses
were investigated in this study. The routine medical examinations
at the clinic was as follows: interview (health symptoms and a clinical
history), clinical status examination, pulmonary function tests, chest
and maxillary sinus radiographs, complete blood cell counts, skin prick
tests to common allergens and moulds, and sputum tests (e.g., concentration
of eosinophilic cationic protein (ECP) as an indicator of inflammation
process in the mucous membranes) and determinations of IgG and IgE antibodies
to moulds. In a few cases, examinations like high-resolution computer
tomography, bronchofibercopy and/ or diffusing capasity determination were
also performed.
Laboratory methods
The amount of specific mould allergen IgE-antibody in serum was determined
by the Pharmacia CAP System RAST FEIA method against 12 moulds (Aspergillus
fumigatus, Aspergillus niger, Aspergillus versicolor, Cephalosporium acremonium,
Cladosporium herbarum, Fusarium moniliforme, Stachybotrys atra, Trichoderma
viridae, Penicillium species (6 different Penicium species) and one
bacteria Thermoactinomyces vulgaris, and the corresponding specific IgG-antibodies
using the Pharmacia CAP System Specific IgG FEIA method. In order to determine,
if the microbiological exposure is recent and in coordination with the
clinical situation, the avidity of the formed IgG-antibodies was
measured. This has previously been done for viral infections (Klaus Hedman
et al, J. Inf.Dis. 159, 4 1989). In this study the avidity of the
circulating antibodies was measured by modifying the Pharmacia IgG
CAP FEIA method.
Preliminary results
In the current project we measured the IgG avidity in 18 patients
with a known history of exposure to moulds. For comparison, the change
in avidity was also followed in a group of patients during hyposensitization
treatment for birch allergy and one person with a fresh exposure to moulds.
The basic avidity level in the population were measured from a non-randomly
selected reference group with no known history of exposure to moulds
in damp or wet buildings.
Most commonly, patients exposed at wet-damaged houses suffered blocked nose, dyspnoea, sore throat, cough, increases mucus secretion, and irritation of nose and eyes. They also report exceptional lethargy and headache. Only with one person, exposure to organic dusts caused pulmonary disease like allergic alveolitis (hypersensitivity pneumonitis) or ODTS (organic dust toxic syndrome) (e.g. ’flu-like’ episodes with chills, fever, malaise, dyspnea, cough and chest tightness occurring 4 to 6 hours after exposure to the bioaerosol). Episodes recur with each exposure. In addition, asthma was also rarely diagnosed, but patients often had asthma-like symptoms.
Increased concentration of myeloperoxidase (MPO) was found in sputum from seven day of the day care workers. Elsewhere, we have earlier shown that high MPO content in sputum may indicate an exposure to indoor air pollutants (Mussalo-Rauhamaa et al. 1999) through an increased inclination for infections.
None of the patients, day care workers or persons in reference group showed an increased level of specific IgE response towards the mould species studied. In contrast, an IgG-antibody response with a lower avidity was found in serum from several of the mould exposed persons from wet-damaged houses and against the same moulds that were isolated from their homes. This result may be interpreted as showing, that these patients have a more recent exposure. The final report will include statistical data to confirm this hypothesis.
5 Co-operation
The project was carried out within national co-operation between Helsinki
University of Technology, HVAC-Laboratory, University of Kuopio, Department
of Enviromental Sciencies and Helsinki University Central Hospital, Departments
of Dermatology and Allergic Diseases.