Relationship between indoor allergen and occupants’allergic symptoms before and after moving in the housewith the countermeasure against allergy
Teruaki Mitamura*1, Kunio Dobashi2, and Hiroki Harasawa3
1 Maebashi Institute of Technology
460-1 Kamisadori-machi,
Maebashi, Gunma 371-0816, Japan*Corresponding author: mitamura@maebashi-it.ac.jp

2 Jobu Hospital for Respiratory Diseases
586-1 Taguchi-machi,
Maebashi, Gunma 371-0048, Japan

3 Harasawa Homes Co., Ltd.
565 Araicho,Ota, Gunma 373-0852, JapanABSTRACT
Allergic symptoms are closely related to indoor allergens, such as airborne particulate matter, fungi, and house
dust mite. This paper introduces a central air-conditioning system integrated with an electrical dust collector
developed as a countermeasure against allergy. Here, it was demonstrated that this air-cleaning system can remove
fine particles of PM2.5. Objectively, this study aims to elucidate the relationship between indoor allergens andoccupants’ allergic symptoms. Thereby, the concentrations of fine particles, airborne fungi, and the amount ofmite allergen in the dust were measured before and after the subject occupants moved into the house installed withan air-cleaning system. In addition, the ratio of active CD4+ T cells in the occupants’ blood was measured as anindicator of their allergic symptoms. The results showed that the concentrations of fine particles, airborne fungi,
and the amount of mite allergens in the houses with a countermeasure against allergy, as well as the ratio of active
CD4+ T cells, were significantly reduced after the occupants have moved in, demonstrating an improvement in
the state of the occupants’ allergic symptoms with the installation of the air-cleaning system in their houses.

KEYWORDS
Air-cleaning system, Indoor allergen, Filed survey, CD4+ T cells, Allergic symptom

1INTRODUCTION

The promotion of highly insulated and airtight houses in Japan since the 1980s has been aparallel move with the reduction of CO2 emissions in the region. Consequently, indoor chemical
pollution has become a social problem since the 1990s. To address the issue, the BuildingStandard Law of Japan on sick house syndrome concerns was revised in July 2003, and various
countermeasures, such as the mandatory installation of ventilation system, were carried out.
Nonetheless, it was pointed out that allergic diseases, i.e., asthma and atopic dermatitis, arerelated to the indoor environment. Despite the increasing number of allergic patients,
countermeasures against allergens in houses were not enough. One of the reasons points to theinadequate elucidation of the relationship between indoor environment and allergic symptoms
in the patients’ houses. In this study, a central air-conditioning system integrated with anelectrical dust collector was developed as a countermeasure against allergy. This air-cleaningsystem is capable of removing fine particles of PM2.5. Practically, this study aims to clarify therelationship between indoor allergens and occupants’ allergic symptoms. To date, the efficientperformance of the system has been verified based on the measurement results in 31 houses
investigated (Mitamura, T. et al., 2013). Specifically, this paper presents a comparative study

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of indoor allergens and the ratio of active CD4+ T cells, as an indicator of allergic symptoms
prior to and after moving into the houses, with a countermeasure against allergy.
2 METHODS
2.1 Air-cleaning system
Figure 1 shows an outline of the central air-conditioning, ventilation, and air-cleaning systeminstalled in the house as a countermeasure against allergy. Outside air (OA) is supplied fromthe air inlet and passes through the air-cleaning unit that consists of a net pre-filter, a medium
efficiency particulate air (MEPA) filter. A large size of particles is caught by this unit. Returnedair (RA) from the stair hall on the second floor is mixed with OA after passing through the aircleaning unit. Subsequently, RA passes through the electric precipitator, which consists of analuminium mesh filter and an electronic cell. It then moves through the collector part of theelectronic cell where alternate parallel plates are charged positively and negatively, creating auniform electronic field. The charged small particles are attached to and collect on the plates
that have the opposite electrical charge. The fractional efficiency of the electric precipitator fora small size of particle E1 (from 0.3 to 1.0 µm) based on the ASHRAE Standard 52.2-1999 is73%. Next, the fresh air passing through the electric precipitator is air-conditioned by theheating/cooling coil and is supplied (SA) to each residential room. Dirty air is exhausted (EA)
from the air outlet in the toilet, bathroom, and kitchen.
Air inlet
Air cleaning unit

OA

Air exhaust

Net pre-filter

EAToiletHeating/Cooling coil

MEPA filter

Bathroom

Electric precipitator

Aluminum mesh filter

KitchenRA

Electronic cell
Heating/Cooling coilSA

Air supply

ClosetReturned airFigure 1: The whole house air-conditioning, ventilation and air-cleaning system

2.2Investigated houses

A total of 40 family units and 107 houses were subjected to the investigation and measurements.
In these targets, at least one family member has an allergic disease. Measurements wereperformed prior to and after the subjects moved into the house installed with a countermeasureagainst allergy. In some of the houses, measurements were repeated twice in roughly 1 monthand 6 months after moving in. Before being occupied, most of the houses were apartmentbuildings used for over 10 years. Houses with a countermeasure against allergy were highly
insulated and airtight.
2.3

Measurements

Indoor allergens were measured according to the concentrations of fine particles, airborne fungi,
and the amount of mite allergen. Fine particle concentrations were measured 1.0-m above floor

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level for both the living room and bedroom. The light-scattering particle counter for aerosol
was used. Fine particles at six size levels, from >0.3 to >5.0 µm, were measured. Sampling air
volume was set at 1.0 L/min; a portable air sampler blew 50 L of air to potato dextrose agar
medium. The airborne fungi were cultured in the incubator for more than 5 days at 25 °C, andthen the number of fungal colonies was counted. An electric vacuum cleaner was used to collecthousehold dust on the living room floor and on the bottom mattress in the bedroom in a 1-m2
area for 2 min. The amount of mite allergen in the household dust was analysed by enzymelinked immunosorbent assay (ELISA). All measurements were carried out with an opening in
the closed room. Additionally, CO2 concentration was measured in an area of the houses todetermine the indoor ventilation characteristics. Mann–Whitney U test was used to compare thedifferences in these values before and after occupying a house with a countermeasure againstallergy.
Accordingly, the occupants were examined medically in Gunma University Hospital. The ratioof active CD4+ T cells was measured through a blood test as an indicator of the occupants’allergic symptoms. Here, a lower value of the ratio of active CD4+ T cells indicates less allergicsymptoms. These examinations, along with the measurements of indoor allergens, wereperformed before and after the occupants moved into the house with a countermeasure against
allergy. Comparison of the differences before and after occupying the house was carried out via
the Wilcoxon signed-rank test.
3

RESULTS AND DISCUSSION

Figure 2 shows the box-and-whisker plots of the average CO2 concentration in the living roomand bedroom before and after the occupants moved into the house with a countermeasureagainst allergy. After occupancy, there were significantly lower concentrations in both rooms(p < 0.01). Specifically, the average CO2 concentration after the occupants moved in was 645
ppm in the living room and 720 ppm in the bedroom. Prior to the occupancy, the mechanicalventilation equipment was not often installed, and ventilation airflow seemed insufficient. In
addition, some of the houses had heating appliances, such as an oil stove used in winter.
***** : p < 0.05** : p < 0.01

Figure 2: Average CO2 concentration

Figure 3 shows the box-and-whisker plots of the concentration of fine particles in the livingroom and bedroom before and twice after the occupants moved into the house with acountermeasure against allergy. Notably, significantly lower concentrations of six levels ofparticle sizes were recorded after the occupants moved in (p < 0.01). In particular, the smaller
the particle size, the lower the concentration. Fine particles causing asthma, within the size
range of 1.0 to 5.0 µm, were suggested to have been effectively removed with the air-cleaning

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system. Based on the first and second measurements made after the occupants moved in, theconcentration was kept low except for particle sizes greater than 5.0 µm. Moreover, such fineparticles were settled in the floor, which indicates that they may not have been sufficiently
removed through the air-cleaning system.
**
**

**
**

* : p < 0.05****** : p < 0.01**

> 1.0 μm

* : p < 0.05**** : p < 0.01** : p < 0.01

**
**

**
> 2.0 μm

* : p < 0.05**** : p < 0.01**

> 0.5 μm

* : p < 0.05**
> 0.7 μm

* : p < 0.05

**

**

**

**

**
**

**

**> 0.3 μm** : p < 0.01****> 5.0 μm* : p < 0.05** : p < 0.01

Figure 3: Concentrations of fine particles

Similarly, Figure 4 shows the box-and-whisker plots of the concentration of airborne fungi inthe living room and bedroom before and twice after the occupants moved into the house with acountermeasure against allergy. After the occupants moved in, significantly lower
concentrations of airborne fungi (p < 0.01) were recorded. The average concentrations ofairborne fungi prior to occupancy were 365 CFU/m3 in the living room and 296 CFU/m3 in thebedroom, and these values varied widely. In contrast, the average concentrations of airborne
fungi after the occupants moved in were below 100 CFU/m3, much lower than 1,000 CFU/m3
specified as the standard by the Architectural Institute of Japan.

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**
**

**
**

* : p < 0.05** : p < 0.01

Figure 4: Concentration of airborne fungi

Figure 5 shows the box-and-whisker plots of the amount of mite allergen (Der 1) in the livingroom and bedroom before and twice after the occupants moved into the house with acountermeasure against allergy. After the occupants moved in, the amount of mite allergenbecame significantly lower (p < 0.01). Additionally, the amount of mite allergen in the bedroom
tended to be lower than in the living room. Specifically, the average amounts of mite allergen
before occupancy were 2.6 µg/g dust in the living room and 6.8 µg/g dust in the bedroom, which
exceeded the average sensitization threshold of 2.0 µg/g dust.
**
**

**
**

* : p < 0.05** : p < 0.01

Figure 5: The amount of mite allergen (Der 1) in household dust

Figure 6 shows the box-and-whisker plots of the ratio of active CD4+ T cells for healthy
subjects before and after they moved into the house with a countermeasure against allergy. The
ratio of active CD4+ T cells after under 3 and 4–6 months of occupancy was not significantly
lower compared with that prior to the occupancy. On the contrary, the ratio of active CD4+ T
cells after over 7 months of occupancy was significantly higher (p < 0.05). However, thedifference between both average values was not significant.
Figure 7 shows the box-and-whisker plots of the ratio of active CD4+ T cells for allergic
patients before and after they moved into the house with a countermeasure against allergy. After
under 3 months of occupancy, the ratio of active CD4+ T cells was not significantly lower
compared with that prior to the occupancy. In contrast, after 4–6 months and over 7 months,
the ratios became significantly lower (p < 0.01 and p < 0.05, respectively). Thus, the allergic
symptoms of allergic patients improved with a countermeasure against allergy after moving
into the house.

326 | P a g e** : p < 0.05** : p < 0.01

Figure 6: The ratio of active CD4+ T Cells for healthy subjects**** : p < 0.05** : p < 0.01

Figure 7: The ratio of active CD4+ T Cells for allergic patients

4

CONCLUSIONSThis paper presented a comparison of the concentrations of fine particles, airborne fungi, andthe amount of mite allergen, prior to and after the subjects’ occupancy in the house with acountermeasure against allergy. Based on the results, the amount of indoor allergen wassignificantly reduced after the occupants moved in. In addition, the measured ratio of active
CD4+ T cells from the blood of the occupants indicated no significant reduction for the healthy
subjects but was considerably reduced for the allergic patients, given a time frame of after 4–6
months and over 7 months of occupancy. Such results indicate that improvement of indoor
environment led to the reduction of allergic symptoms.
5ACKNOWLEDGEMENTS

A part of this research work was supported by the Ministry of Land, Infrastructure, Transportand Tourism of Japan in 2009, and from 2013 to 2015. The authors would also like toacknowledge the occupants of the investigated houses.
6REFERENCE

Mitamura, T. et al. (2013). Verification of Indoor Air Quality Before and After Moving in theHouse with the Countermeasure Against Allergy. 11th REHVA World Congress and the 8thInternational Conference on IAQVEC Clima2013 Congress.

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