ArticlePDF Available

Intrusion of airborne pollen through open windows and doors

  • Centre for Economic Development, Transport and the Environment

Abstract and Figures

The importance of the transport of pollen by air movement into houses was evaluated using six to eight simultaneously collecting rotorod-type samplers, creating either a sampler line from outdoors to inside the room, or a sampler grid inside a room. The number of incoming pollen grains was highly dependent on the outdoor concentration. The highest concentrations inside (1–2m distance) and outside (1m) the room were 600 and 3,250grains/m3, respectively, in the Betula pollen season and 1,980 and 5,080grains/m3 in the Pinus season. The pollen concentration and the indoor/outdoor (I/O) ratio decreased as the distance from the ventilation opening increased. Inside the room at a distance of 1–2m 28%, and at a distance of 3–5m 12%, of the outside concentration was recorded. In the lower part of the opening the mean proportion was 63% and in the upper part of the opening it was 40%. Efficient ventilation with two open windows increased the I/O ratio and enabled the pollen to spread throughout the room. During the Pinus pollen season 3–35% of the outdoor concentration was simultaneously recorded at six locations inside the room with two open windows and only 0.1–3.6% with one open window. At the same point in the room the I/O ratio varied from <1 to 35%, depending on the sampling conditions. Only a minor effect on the I/O ratio was found between small and large ventilation windows and the door, although it was expected that more air and pollen grains would come indoors through a larger opening.
Content may be subject to copyright.
Intrusion of airborne pollen through open windows
and doors
Juha Jantunen ÆKimmo Saarinen
Received: 27 April 2009 / Accepted: 21 May 2009 / Published online: 13 June 2009
ÓSpringer Science+Business Media B.V. 2009
Abstract The importance of the transport of pollen
by air movement into houses was evaluated using six
to eight simultaneously collecting rotorod-type sam-
plers, creating either a sampler line from outdoors to
inside the room, or a sampler grid inside a room. The
number of incoming pollen grains was highly depen-
dent on the outdoor concentration. The highest
concentrations inside (1–2 m distance) and outside
(1 m) the room were 600 and 3,250 grains/m
respectively, in the Betula pollen season and 1,980
and 5,080 grains/m
in the Pinus season. The pollen
concentration and the indoor/outdoor (I/O) ratio
decreased as the distance from the ventilation opening
increased. Inside the room at a distance of 1–2 m
28%, and at a distance of 3–5 m 12%, of the outside
concentration was recorded. In the lower part of the
opening the mean proportion was 63% and in the
upper part of the opening it was 40%. Efficient
ventilation with two open windows increased the I/O
ratio and enabled the pollen to spread throughout the
room. During the Pinus pollen season 3–35% of the
outdoor concentration was simultaneously recorded at
six locations inside the room with two open windows
and only 0.1–3.6% with one open window. At the
same point in the room the I/O ratio varied from\1to
35%, depending on the sampling conditions. Only a
minor effect on the I/O ratio was found between small
and large ventilation windows and the door, although
it was expected that more air and pollen grains would
come indoors through a larger opening.
Keywords Atmospheric transport
Betula Indoor exposure Pinus sylvestris
Pollen Ventilation
1 Introduction
People spend most of their time indoors, which
makes indoor air quality important to human health.
For allergic people indoor exposure to pollen and
fungal spores is of particular concern. Several studies
have evaluated the level of indoor exposure.
Although comparison of the results is difficult,
because of different sampling methods, ventilation
conditions, building designs, and geographical loca-
tions of the studies, the conclusions are very different.
Substantial amounts of pollen have been found
inside houses and public buildings (D’Amato et al.
1996; Enomoto et al. 2004; Takahashi et al. 2008),
but there have also been studies concluding that
pollen is rare in indoor air and occurs only when
pollen production is high (O’Rourke and Lebowitz
1984). For example, during the peak flowering period
for Betula, pollen concentrations indoors remained
mostly at a level barely inducing reactions even in the
most sensitive persons (Hugg and Rantio-Lehtima
J. Jantunen (&)K. Saarinen
South Karelia Allergy and Environment Institute,
¨ritie 15, 55330 Tiuruniemi, Finland
Aerobiologia (2009) 25:193–201
DOI 10.1007/s10453-009-9124-8
2007). Measurements inside buildings have usually
revealed concentrations 2–6% of the corresponding
outdoor concentrations (Spiegelman et al. 1963;
Yankova 1991; Carin
˜anos et al. 2004; Lee et al.
2006; Hugg and Rantio-Lehtima
¨ki 2007; Ishibashi
et al. 2008) but the average values have occasionally
been as high as 30–53% (Stock and Morandi 1988;
Sterling and Lewis 1998).
Pollen is carried in on the feet and bodies of people
and pets and by airflow through windows, doors and
ventilation holes (Enomoto et al. 2004; Ishibashi
et al. 2008; Vural and Ince 2008). Takahashi et al.
(2008) found that some Japanese cedar pollen could
gain access even through small holes in window sills
and closed ventilation ducts, and another study
indicates that little or no pollen comes in because
of air movement (O’Rourke and Lebowitz 1984).
We evaluated the importance of the transport of
pollen into houses through air movement by studying
indoor pollen concentrations when windows or a door
were opened. We used six to eight simultaneously
collecting rotorod-type samplers, creating either a
sampler line from outdoors to inside the room or a
sampler grid inside a room. The main study period
coincided with the Betula pollen season in early May,
when the daily mean values in southern Finland
between the years 2002 and 2008 peaked at 3,000–
15,000 pollen grains per cubic metre of air (pollen
monitoring data of South Karelia Allergy and Envi-
ronment Institute). The main objectives were to
1. how much pollen comes inside through ventila-
tion windows and doors;
2. the importance of the airflow and the size of a
ventilation opening to the indoor pollen concen-
tration; and
3. how far inside the room pollen grains are able to
2 Materials and methods
Field sampling for airborne pollen was performed in a
two-story building in Joutseno, SE Finland, using
rotorod-type impaction samplers. Most of the data
were collected during the Betula flowering season
but, because of the short peak pollen period,
measurements were also taken during the Alnus and
Pinus sylvestris flowering season. The pollen grains
of Betula and Alnus are of approximately the same
shape and size (22–30 lm, 6.1–6.8 g 910
, set-
tling speed 1.5–1.6 cm/s), whereas the Pinus pollen
grain is considerably larger (65–80 lm) and heavier
(18.4 g 910
) and has a higher settling speed
(3.0 cm/s) (Ertdman 1969; Schwendemann et al.
Two types of sampling sets were used in the study:
(A) The intrusion of pollen through open windows
and doors was measured in three rooms with
ventilation openings of different sizes using six
simultaneously collecting samplers (Fig. 1a).
The samplers were located (1) 1 m outside the
opening, (2) in the lower and (3) upper parts of
the opening (10–20 cm from the frames), and
(4) 1–2 m and (5) 3–5 m inside the room. In
each set, one sampler was positioned at the
same location in the courtyard at a distance of
Fig. 1 a The intrusion of pollen through open windows and
doors was measured using six simultaneously collecting
samplers (Y). The sixth sampler was located in the courtyard.
bPollen dispersal inside a room was measured using eight
samplers (Out 1 m,Wl, and AF). The pattern-filled columns
on the right represent tables (3) and storage shelves (2)
194 Aerobiologia (2009) 25:193–201
10 m from the building (6). Samplers in the
yard and inside the house were placed at a
height of 1 m from the ground or floor. Indoor
samplers were placed in line with the incoming
air. Ventilation windows in the second-floor
rooms had an area of 0.25 m
(0.35 90.72 m)
and 0.55 m
(0.42 91.30 m) whereas the
doors in the first floor room were 2.1 m
(1 92.1 m) in area. Altogether 26 data sets
(156 single measurements) were collected
between 2.4.2008 and 5.6.2008. The study
rooms in the second floor were vacuum-cleaned
between sampling times and the room in the
first floor every second or third time.
(B) Indoor pollen dispersal was measured using
eight simultaneously collecting samplers in the
second-floor room with small ventilation win-
dows (0.25 m
) (Fig. 1b). An outdoor sampler
was located 1 m outside the window and a
sampler was located in the ventilation opening
in the lower part of the window. Six samplers
were systematically placed 2 m from each other
throughout the room (4 98 m). Nine data sets
(70 single measurements) were collected
between 12.5.2008 and 6.6.2008. Four sets
were measured at a height of 1 m, and five sets
at a height of 0.1 m, from the floor. The room
was vacuum-cleaned between sampling times.
The airflow through an opening was monitored by
means of an anemometer placed at a height of 0.3 m
in the middle of the opening. During a constant
sampling time of 1 h 12–15 airflow values were
recorded at intervals of 1 min. The first five mea-
surements were taken 5–10 min after the beginning
of the sampling period, then 5–7 values at the end of
the sampling period. In addition, the minimum and
maximum airflow during the sampling period were
included to calculate the mean airflow. Altogether 19
sampling periods were used with two windows/doors
open on the opposite walls of the room, together with
16 periods with one opening only. Depending on the
wind direction, pollen counts were measured on
different sides of the rooms. Outdoor temperatures
were also measured. Indoor temperatures varied
between 20 and 22°C.
The mean values of the amounts of pollen
collected at the two ends of the U-shaped rods were
used for analysis. Pollen data were converted into
concentration values (grains/m
). The multiplication
factor was 0.80 =19(rod width (0.0019 m) 9rod
height (0.019 m) 9head diameter (0.08 m) 9p9
RPM (2,300) 9time rod used (60 min))
. The
concentration of the main pollen was used in the
analysis, this being Alnus sp. from 2.4.2008 to
3.4.2008, Betula sp. from 3.5.2008 to 21.5.2008,
and Pinus sylvestris from 3.6.2008 to 6.6.2008. The
other species comprised only 2.5% of the total
number of pollen grains, on average.
The percentage proportions of pollen inside the
study rooms and in the opening were all calculated by
comparing the concentrations to the pollen count 1 m
outside the room. The sampling point near the
opening describes the concentration of incoming
pollen better than the sampler in the yard. The
reliability of the results was evaluated by comparing
pollen counts between the samplers in the yard and
outside the opening and also by comparing the
concentrations measured on the roof-top at a 1.5 km
distance from the study site with a Burkard volumet-
ric sampler (Hirst 1952).
Spearman’s correlation test was used to determine
a possible relationship between pollen concentrations
and measurement conditions: airflow through the
opening, number of open windows and doors, size of
ventilation openings, and the distance from the
opening. The difference between different concen-
tration levels, weak and strong airflow, and three
sizes of openings were statistically tested using
analysis of variance (ANOVA). The non-parametric
paired Wilcoxon test was used for a statistical
comparison between indoor/outdoor (I/O) ratios
measured at different heights and the number of
open windows.
3 Results
High pollen concentrations were recorded in both the
window and the door opening and inside the rooms
(Table 1). Compared with the outdoor concentration,
in the lower part of the opening the mean proportion
was 63% and in the upper part of the opening 40%.
Inside the room at a 1–2 m distance it was 28% of the
outdoor concentration, and at a 3–5 m distance 12%
of the outdoor concentration. The peak concentration
inside the room (1–2 m distance) was almost
Aerobiologia (2009) 25:193–201 195
600 grains/m
in the Betula pollen season and
2,000 grains/m
in the Pinus season.
The outdoor samples simultaneously measured
using rotorod-type samplers were highly comparable,
although more than half of the samples outside the
room (1 m from the building) were measured at the
height of the second floor (65%) and on the other side
of the house (54%) compared with the samples in the
yard (10 m from building). More than 20% mean
deviation from the concentrations of the yard and
Table 1 Pollen concentrations (grains/m
) in the courtyard, 1 m outside the room, in the lower and upper parts of the open windows
and doors, and at two distances inside the rooms at a height of 1 m
Date (time) Outdoor temp. Air flow Burkard (8–16) Outdoor Window/door Indoor I/O
Yard Out 1 m Lower Upper 1–2 m 3–5 m %
2.4.2008 (12:05)
11 0.4 275 109 82 63 52 7 2 2
2.4.2008 (13:25)
11 0.3 275 393 302 185 54 64 12 4
3.4.2008 (10:55)
9 0.4 223 59 54 33 31 5 3 6
3.4.2008 (12:10)
10 1.1 223 71 71
36 52 22 4 6
3.4.2008 (14:40)
11 0.4 223 216 239 234 87 102 12 5
3.5.2008 (10:25)
20 0.2 1,930 849 924 265 460 247 100 11
3.5.2008 (11:35)
20 0.9 1,930 2,353 3,248 888 508 598 276 8
3.5.2008 (12:50)
20 0.3 1,930 898 646 252 198 114 9 1
3.5.2008 (14:20)
20 0.7 1,930 364 290 140 227 32 1 0.3
4.5.2008 (11:55)
19 0.2 620 670 576 90 54 32 21 4
4.5.2008 (13:15)
19 0.0 620 120 107 143 67 94 4 4
4.5.2008 (14:25)
19 0.0 620 66 41 12 15 6 1 2
6.5.2008 (12:10)
6 0.4 51 18 48 25 8 2 2 4
6.5.2008 (13:20)
6 0.2 51 25 21 28 4 5 0.4 2
7.5.2008 (11:55)
9 0.1 17 33 27 6 7 0.4 0.4 1
7.5.2008 (13:35)
9 1.2 17 1 3 3 3 4 2 67
10.5.2008 (11:30)
14 1.0 171 84 70 36 20 38 30 43
10.5.2008 (12:40)
14 0.3 171 86
86 87 0.4 13 2 2
10.5.2008 (13:50)
15 0.4 171 155 153 89 56 1 1 1
11.5.2008 (11:20)
17 1.4 1,630 970 718 326 508 268 73 10
11.5.2008 (12:30)
17 0.6 1,630 543 366 306 188 211 149 41
11.5.2008 (13:40)
18 2.5 1,630 258 294 323 266 207 205 70
11.5.2008 (14:50)
18 0.2 1,630 235 181 119 38 35 34 19
3.6.2008 (14:30)
16 0.2 772 1,018 352 250 139 178 1 0.3
5.6.2008 (11:10)
20 0.6 5,500 1,834 2,156 1,684 9 110 78 4
5.6.2008 (12:20)
20 0.9 5,500 4,400 5,080 3,368 2,812 1,980 182 4
Means when Out 1 m =
3–86 (n=10) 11 0.5 182 55 51 33 20 10 4 8
107–366 (9) 16 0.6 987 367 254 199 125 85 48 19
576–5,080 (7) 19 0.6 2,720 1,711 1,907 982 650 478 118 6
The ratio of the indoor to the outdoor (Out 1 m) concentrations (%) is calculated from the results at a 3–5 m distance from the
openings. Measurement conditions are expressed by outdoor temperature (°C) and airflow (m/s) through the window/door opening
A room with small windows (0.25 m
Two windows or doors open
Doors (2.1 m
Large windows (0.55 m
Missing value replaced with the concentration in column ‘‘Yard’’ or ‘‘Out 1 m’
196 Aerobiologia (2009) 25:193–201
outside the opening was found only on 3.6.2008,
with low concentrations on 4.5.2008, 6.5.2008, and
7.5.2008. Both increasing and decreasing trends were
observed during the sampling days (e.g. 3.4.2008 and
4.5.2008; Table 1), which increased the differences
between the results from the rotorod-type sampler
and the Burkard sampler (Fig. 2).
Concentrations outside the opening were divided
into three levels with approximately the same number
of measurements. The threshold values occurred in
large gaps between concentrations of 87–107 and
366–576 (Table 1). The outdoor concentration had a
strong correlation with the amount of incoming
pollen but only a minor effect on the I/O ratio
(Table 2; Fig. 3). For the lowest outdoor concentra-
tion (\10 grains/m
) the I/O ratio is probably either
too high to be purely due to chance, or else there was
already pollen present inside the room (Tables 1,3).
An increase in the airflow through the opening had a
positive correlation with the I/O ratio and there was a
significant difference in the I/O ratio between weak and
strong airflows (Fig. 4). Opening the second window
or door increased the airflow and correlated with the
indoor pollen concentration and I/O ratio, especially at
a greater distance (3–5 m) from the opening.
There was no statistical difference in the I/O ratio of
rooms with different ventilation openings of different
sizes, although the one with the smallest windows had
a slightly lower I/O ratio than the other rooms. A low
sampling height (0.2 m from floor) in the lower part of
the door probably resulted in different ratios to those in
the windows (1 m from floor) (Fig. 5). Again, the
difference between the lower and upper parts of the
door (mean =59%; SD =32%) was higher than
the corresponding ratio in the windows (-2%; 21 and
11%; 22%; Anova: P=0.000).
Because of the higher settling speed of Pinus
pollen grains, Betula had a higher ratio of the indoor
to the outdoor pollen count under the same sampling
conditions, such as the same room at a distance of 3–
5 m, the same airflow (±0.1 m/s), and the same
number of ventilation openings. The mean I/O ratios
in five comparative pairs (door on 11.5–5.6.2008,
large window on 11.5–3.6.2008, small window on
3.5–5.6.2008 in Table 1and 12.5–3.6.2008, 12.5–
6.6.2008 in Table 3) were 13% (SD =13%) of
Betula pollen and 2% (SD =3%) of Pinus pollen
(Wilcoxon: P=0.043).
Two opened windows increased both the airflow
and the dispersal of pollen inside the room. The
highest concentration in the middle of the room was
almost 100 grains/m
(9–10%) and at the back of
the room (5–6 m from the window) over 70 grains/m
(5–7%) (Table 3). The mean I/O ratios were 2.8
times higher when two windows were opened
(means =34%, SD =11 and 12%, SD =5%; Wil-
coxon test: P=0.028) and 5.3 times higher at floor
level compared with a height of 1 m (37%, SD =8
and 7%, SD =5%; Wilcoxon test: P=0.028). The
importance of the ventilation and the sampling height
for indoor pollen counts was distinguishable in the
four comparable data sets during the Pinus pollen
29 1 3 5 7 9 1113151719212325272931 2 4 6
Betula (Burkard) Pinus (Burkard)
rotorod-type sampler
Fig. 2 Betula and Pinus pollen season measured on a rooftop using a Burkard sampler (grains/m
/day) and the concentrations
outside the study house measured by rotorod-type sampler (1-h samples)
Aerobiologia (2009) 25:193–201 197
season (Table 4). When only one window was opened
less than 1% of the outdoor pollen concentrations was
recorded throughout the room at a height of 1 m.
4 Discussion
Most of the people allergic to Betula pollen experience
symptoms when concentrations are [100 grains/m
(Viander and Koivikko 1978). Our study indicated that
these concentrations are commonly reached inside
houses if the door or windows are kept open during
the peak flowering season of abundant wind-
pollinated trees. High indoor concentrations of pollen
([100 grains/m
) were recorded fourteen times at a
distance of 1–2 m and nine times at a distance of
3–5 m. The number of incoming pollen grains was
highly dependent on the outdoor concentration, as
reported in previous studies (Sterling and Lewis 1998;
Lee et al. 2006). The highest concentrations both
outside (5,080 grains/m
) and inside the room (1,980
) were recorded for Pinus pollen. Because of
an abnormally short peak in the Betula pollen period
the daily average exceeded 1,000 grains/m
on three -
days only, whereas the annual average from 2002 to
2007 was seven days (pollen monitoring data of South
Karelia Allergy and Environment Institute).
Pollen concentrations both indoors and outdoors
were generally higher than recorded in most earlier
studies. Outdoor concentrations have mainly been less
than 100 grains/m
, but the sampling strategy, peri-
ods, and probably also the locations inside the houses
were different (O’Rourke and Lebowitz 1984; Stock
Table 2 Spearman correlation matrix calculated using pollen counts and percentages (pollen counts at a sampling point/1 m outside
the room)
Increasing size
of ventilation
Opening of second
Yard Out 1 m Burkard (8–16)
Air flow -0.191
1–2 openings -0.185 0.453*
Burkard (8–16) -0.012 0.159 0.129
Yard -0.062 0.178 0.206 0.870***
Out 1 m -0.037 0.222 0.267 0.979*** 0.863***
Wl 0.129 0.315 0.216 0.930*** 0.945*** 0.849***
Wu -0.216 0.309 0.381 0.776*** 0.786*** 0.740***
1–2 m 0.160 0.351 0.401* 0.802*** 0.840*** 0.806***
3–5 m 0.086 0.464* 0.484* 0.707*** 0.782*** 0.766***
Wl (%) 0.610*** 0.157 -0.123 -0.265 -0.227 -0.180
Wu (%) -0.197 0.461* 0.350 -0.176 -0.147 0.044
1–2 m (%) 0.351 0.395* 0.401* 0.006 0.054 0.097
3–5 m (%) 0.210 0.531** 0.504** 0.056 0.142 0.205
Sampling points were located in the courtyard, 1 m outside the room, in the lower (Wl) and upper (Wu) parts of the open windows
and door, and at two distances inside the room. The results of the sampling points were also compared to Burkard concentrations
(8 am–4 pm) measured at a 1.5 km distance from the study site. Pollen concentrations are given in Table 1
*** P\0.001; ** P\0.01; * P\0.05
Windows: 0.25 and 0.55 m
, doors: 2.1 m
0 %
10 %
20 %
30 %
40 %
50 %
60 %
70 %
Wl Wu 1-2m 3-5m
3 - 86 (n=10)
107 - 366 (n=9)
576 - 5 080 (n=7)
p= 0.224 p= 0.679 p= 0.655 p= 0.667
Out1m concentrations
Fig. 3 Pollen proportion in the lower (Wl) and upper (Wu)
parts of the open window and door, and indoors, compared
with the outside concentration in three concentration groups
198 Aerobiologia (2009) 25:193–201
and Morandi 1988; Sterling and Lewis 1998; Lee et al.
2006). In the same region in Southeast Finland, in the
hospital entrance hall and in two homes, indoor
concentrations were much lower (means 1.1–
3.4 grains/m
) but outdoor concentrations during the
sampling periods were also much lower (7–96 grains/
) (Hugg and Rantio-Lehtima
¨ki 2007).
The pollen concentration and the I/O ratio
decreased as the distance from the ventilation opening
increased. The highest pollen amounts are usually
found near ventilation windows and holes and in
lobbies (Kiyosawa and Yoshizawa 2001; Hugg and
¨ki 2007; Takahashi et al. 2008). The
airflow through the opening and the sampling height
also had a significant effect on the ratio. In the absence
of air movement pollen grains settle (Fahlbusch et al.
2001; Enomoto et al. 2004). At the same point in the
room the I/O ratio varied from \1 to 35%, depending
on the sampling conditions. This explains why it is
very difficult to compare I/O ratios obtained in
Table 3 Pollen concentrations (grains/m
) 1 m outside the room, in the lower part of the window opening (Wl), and at six locations
inside the room (A–F) at 1–6 m distance from the window
Date Height Window open Air flow Out 1 m Wl A B C D E F I/O
1m 3m 3m 4m 5m 6m %
12.5.2008 (12:50) 1 1 0.4 85 49
2 2 0.8 0.4 0.4 1.3
12.5.2008 (14:10) 1 2 1.1 200 63
18 18 18 24 32 11.0
13.5.2008 (11:55) 0.1 1 0.8 5 3 2 2 3 2 0.8 2 39.3
13.5.2008 (13:15) 0.1 2 2.9 5 8 5 3 4 4 5 3 80.0
21.5.2008 (13:30) 0.1 2 1.7 11 6 4 9 2 8 2 2 40.9
3.6.2008 (10:20) 1 1 0.3 1,356 480 5 3 4 2 2 3 0.2
3.6.2008 (11:40) 0.1 1 0.2 1,110 274 40 28 6 30 4 4 1.7
6.6.2008 (12:55) 1 2 1.2 1,520 296 506 280 47 82 72 79 11.7
6.6.2008 (14:20) 0.1 2 1.1 1,006 694 352 260 93 98 40 60 15.0
Two windows open, 1 m: 1.1 860 180 506
149 32 50 48 56 20.5
Two windows open, 0.1 m: 1.9 341 236 120 91 33 37 16 22 45.3
One window open, 1 m: 0.5 720 265 5
One window open, 0.1 m: 0.5 558 138 21 15 5 16 2 3 11.4
The I/O ratio is the mean indoor concentration compared with the pollen count outside the room (Out 1 m). Sampling conditions are
expressed by the height of the samplers (m), the number of open windows, and airflow (m/s) through window
Missing values
0 %
10 %
20 %
30 %
40 %
50 %
60 %
70 %
Wl Wu 1-2m 3-5m
0.0-0.7 m/s (n=19)
0.8-2.5 m/s (n=7)
p = 0.017
p= 0.007 p= 0.008 p= 0.942
Fig. 4 Pollen proportion in the lower (Wl) and upper (Wu)
parts of the open window and door and indoors compared with
the outside concentration during a weak and strong airflow
through the opening
0 %
10 %
20 %
30 %
40 %
50 %
60 %
70 %
Wl Wu 1-2m 3-5m
Small window
Big window
p = 0.596
p= 0.270
p= 0.287
p= 0.001
Fig. 5 Pollen proportion in the lower (Wl) and upper (Wu)
parts of the open windows and door, and indoors, compared
with the outside concentration in the three study rooms with
different sizes of ventilation opening (small win-
dow =0.25 m
, large window =0.55 m
, door =2.1 m
Aerobiologia (2009) 25:193–201 199
different studies. If the sampling conditions and
distances from ventilation openings are not known,
it is virtually impossible to compare the results.
Unexpectedly, the size of the ventilation opening
had only a minor effect on the I/O ratio, although
more air and pollen grains should automatically flow
indoors through a larger opening. Pollen concentra-
tions in the lower and the upper parts of the opening
differed between the windows and the door. The low
sampling height at the door, which was 20 cm from
the floor and 70 cm from ground level, probably
increased the amount of pollen. The difference
between concentrations in the lower and upper parts
of the opening was especially high for three mea-
surements, when only 4–14% of the concentrations in
the lower part of the door was found in the upper part
(6.5.2008, 10.5.2008, and 5.6.2008 in Table 1). In
each case measurements were taken only when one
ventilation door was open, probably forcing the air to
rotate vertically inside the room. Cool air (6, 14, and
20°C) flows in at the bottom and warmer indoor air
(20–22°C) flows out at the top of the door opening.
Guidelines for good indoor air quality tend towards
a preference for short but efficient ventilation now and
then. However, ventilation achieved with two open
windows also enables pollen to spread throughout the
room. During the Pinus pollen season 3–35% of the
outdoor concentration was simultaneously recorded in
the room with two open windows and only 0.1–3.6%
in that with one open window. The locations of the
ventilation openings and furniture determine the
floating and settling of the incoming particles
(Richmond-Bryant et al. 2006). Because of the
position of the window the pattern of the decreasing
trend in the amount of pollen is a clockwise rotation in
the study room. Near the window the pollen concen-
tration in the outgoing air tends to be slightly higher
than at the opposite side of the room.
It can be concluded that large amounts of pollen can
float inside the house through open windows and
doors, if the outdoor pollen concentration is high. The
number of airborne pollen grains decreased rapidly
with increasing distance from ventilation openings.
With increased airflow through an opening more
pollen grains could come inside and penetrate deeper
into a room. Allergic people can reduce indoor
exposure to pollen by keeping the windows and doors
closed during the peak flowering season, or by using
appropriate air filters in ventilation windows and
ducts. The time when ventilation occurs has an effect
on the intrusion of pollen. The highest pollen concen-
trations are recorded during a dry and sunny afternoon
and evening, but pollen grains can be found through-
out the day during the peak pollination period (Rantio-
¨ki et al. 1991; Clot 2001). Rainy weather
usually reduces the pollen concentration even during
the peak flowering period. Filters and closed doors are
unable to keep all pollen grains outdoors, because
pollen can be carried in by the house’s occupants and
pets (Ishibashi et al. 2008; Takahashi et al. 2008).
Acknowledgments The study was financially supported by
the South Karelia Regional Fund of the Finnish Cultural
Foundation. We thank Auli Rantio-Lehtima
¨ki for her valuable
comments on the manuscript.
Table 4 Outdoor pollen concentrations and the ratio of the indoor to the outdoor pollen counts at six locations inside the room (A–F
in Fig. 1b)
2 windows, 1 m/1window, 1 m Indoor
2 windows, 0.1 m / 1 window, 0.1 m
a) 33.3% / 0.4% b) 18.4% / 0.2%
Outdoor concentration Airflow (m/s) 35.0% / 3.6% 25.8% / 2.5%
1006 / 1110 grains/m31.2 / 0.3
1520 / 1356 grains/m31.1 / 0.2 c) 3.1% / 0.3% d) 5.4% / 0.1%
e) 4.7% / 0.1% f) 5.2% / 0.2% —
At each sampling point four values are given. The first column indicates the results measured when two windows were opened
(incoming air near point a and outgoing air near point f) and the second corresponding numbers when one window was opened (near
point a). The upper rows were measured inside the room at a height of 1 m, and the lower rows at a height of 0.1 m, during the Pinus
pollen season on 3.6 and 6.6
200 Aerobiologia (2009) 25:193–201
˜anos, P., Alca
´zar, P., Gala
´n, C., Navarro, R., & Dominquez,
E. (2004). Aerobiology as a tool to help in episodes of
occupational allergy in work places. Journal of Investiga-
tional Allergology and Clinical Immunology, 14, 300–308.
Clot, B. (2001). Airborne birch pollen in Neuchatel (Switzer-
land): Onset, peak and daily patterns. Aerobiologia, 17,
25–29. doi:10.1023/A:1007652220568.
D’Amato, G., Liccardi, G., Saggese, M., Mistrello, G.,
D’Amato, M., & Falagiani, P. (1996). Comparison
between outdoor and indoor airborne allergenic activity.
Annals of Allergy, Asthma & Immunology, 77, 147–152.
Enomoto, T., Onishi, S., Sogo, H., Dake, Y., Ikeda, H., Fu-
nakoshi, H., et al. (2004). Japanese cedar pollen in floating
indoor house dust after pollinating season. Allergology
International, 53, 279–285. doi:10.1111/j.1440-1592.
Ertdman, G. (1969). Handbook of palynology. Morphology,
taxonomy and ecology. Copenhagen: Munksgaard.
Fahlbusch, B., Hornung, D., Heinrich, J., & Ja
¨ger, L. (2001).
Predictors of group 5 grass-pollen allergens in settled
house dust: Comparison between pollination and non-
pollination seasons. Allergy, 56, 1081–1086. doi:10.1034/
Hirst, J. M. (1952). An automatic volumetric spore trap. The
Annals of Applied Biology, 39, 257–265. doi:10.1111/
Hugg, T., & Rantio-Lehtima
¨ki, A. (2007). Indoor and outdoor
pollen concentrations in private and public spaces during
the Betula pollen season. Aerobiologia, 23, 119–129. doi:
Ishibashi, Y., Ohno, H., Oh-ishi, S., Matsuoka, T., Kizaki, T.,
& Yoshizumi, K. (2008). Characterization of pollen dis-
persion in the neighborhood of Tokyo, Japan in spring of
2005 and 2006. International Journal of Environmental
Research and Public Health, 5, 76–85. doi:10.3390/ijerph
Kiyosawa, H., & Yoshizawa, S. (2001). Study of the control of
indoor pollen exposure. Part 1. Intrusion of airborne pol-
len into indoor environment and exposure dose. Journal of
Architecture, Planning and Environmental Engineering,
548, 63–68 (in Japanense, abstract in English).
Lee, T., Grinshpun, S. A., Martuzevicius, D., Adhikari, A.,
Crawford, C. M., Luo, J., et al. (2006). Relationship
between indoor and outdoor bioaerosols collected with a
button inhalable aerosol sampler in urban homes. Indoor
Air, 16, 34–47. doi:10.1111/j.1600-0668.2005.00396.x.
O’Rourke, M. K., & Lebowitz, M. D. (1984). A comparison of
regional atmospheric pollen with pollen collected at and
near homes. Grana, 23, 55–64.
¨ki, A., Helander, M. L., & Pessi, A. -M. (1991).
Circadian periodicity of airborne pollen and spores; sig-
nificance of sampling height. Aerobiologia, 7, 129–135.
Richmond-Bryant, J., Eisner, A. D., Brixey, L. A., & Wiener,
R. W. (2006). Transport of airborne particle within a
room. Indoor Air, 16, 48–55. doi:10.1111/j.1600-0668.
Schwendemann, A. B., Wang, G., Mertz, M. L., McWilliams,
R. T., Thatcher, S. L., & Osborn, J. M. (2007). Aerody-
namics of saccate pollen and its implications for wind
pollination. American Journal of Botany, 94, 1371–1381.
Spiegelman, J., Friedman, H., & Blumstein, G. I. (1963). The
effects of central air conditioning on pollen, mold, and
bacterial concentrations. The Journal of Allergy and
Clinical Immunology, 34, 426–431.
Sterling, D. A., & Lewis, R. D. (1998). Pollen and fungal
spores indoor and outdoor of mobile homes. Annals of
Allergy, Asthma & Immunology, 80, 279–285.
Stock, T. H., & Morandi, M. T. (1988). A characterization of
indoor and outdoor microenvironmental concentrations of
pollen and spores in two Houston neighbourhoods. Envi-
ronment International, 14, 1–9. doi:10.1016/0160-
Takahashi, Y., Takano, K., Suzuki, M., Nagai, S., Yokosuka,
M., Takeshita, T., et al. (2008). Two routes for pollen
entering indoors: Ventilation and clothes. Journal of
Investigational Allergology and Clinical Immunology, 18,
Viander, M., & Koivikko, A. (1978). The seasonal symptoms
of hyposensitized and untreated hay fever patients in
relation to birch pollen counts: Correlation with nasal
sensitivity, prick tests and RAST. Clinical Allergy, 8,
387–396. doi:10.1111/j.1365-2222.1978.tb00474.x.
Vural, C., & Ince, A. (2008). Pollen grains in the house dust of
Kayseri, Turkey. International Journal of Natural and
Engineering Sciences, 2, 41–44.
Yankova, R. (1991). Outdoor and indoor pollen grains in Sofia.
Grana, 30, 171–176.
Aerobiologia (2009) 25:193–201 201
... As many people spend at least 80% of their time indoors [24][25][26], it is crucial to understand the outdoor-to-indoor pollen transfer pathways and to analyze the factors affecting indoor pollen concentration to reduce indoor pollen concentration and prevent hay fever. Although some basic research on the pollen I/O ratio has emerged [27][28][29][30], there have been few papers that provide a systematic review. Therefore, the indoor/outdoor pollen concentration (I/O) ratio and its influencing factors need to be summarized. ...
... They speculated that this was because the smaller diameter of pollen was more likely to cause tracheobronchial deposition in humans. Similar conclusions were confirmed by subsequent studies [27,102,103], and other researchers found that different pollen types had different I/O ratios [64,104,105]. ...
... The classification of different mean pollen diameters in the present study is listed in Fig. 9, and the pollen types and I/O ratio investigated in different articles are summarized in Fig. 10 [12,[26][27][28]32,39,42,49,59,62,64,[77][78][79][80][81][82][83][84]99,[102][103][104][106][107][108][109][110][111][112][113]. Notably, we selected the average values of I/O ratio for statistics because the diverse articles had differences in the measured durations and obtained I/O ratio ranges. ...
Pollen particles enter indoor areas through various routes, negatively affecting indoor air quality and human health. Therefore, it is important to measure the indoor and outdoor concentrations of pollen and to study the factors influencing the indoor/outdoor pollen concentration (I/O) ratio. Here, we review recent developments in pollen research, focusing on experimental studies on the I/O ratio and contributing factors, and suggest avenues for further research. Based on a literature search of 108 publications, the development, basic principles, advantages, and disadvantages of pollen samplers are summarized, and factors influencing the I/O ratio are summarized. The results showed that pollen type, ventilation, indoor ornamental plants, and human activities significantly affected the value of the I/O ratio, which ranged from 0 to 0.5. Values of I/O ratio of 0.5–1 and higher were mainly found in studies with pollen diameters ranging from 15–30 μm. A window that opened perpendicular to the dominant outdoor wind direction and a larger window opening area also increased the I/O ratio. Outdoor pollen can adhere to human surfaces and enter a room through human activity, increasing the I/O ratio. The results of this study will help other researchers to understand the state of research on pollen I/O ratios and hopefully provide suggestions for future research directions.
... In other studies, the indoor pollen was measured under different conditions, according to whether the doors and windows were open or closed. Rooms with a greater number of windows were found to have higher levels of pollen [1,16,[46][47][48]. The concentrations of birch and pine pollens decreased as the distance between the pollen collector and the window increased [12,47]. ...
... Rooms with a greater number of windows were found to have higher levels of pollen [1,16,[46][47][48]. The concentrations of birch and pine pollens decreased as the distance between the pollen collector and the window increased [12,47]. A number of studies have found that the concentration of pollen in a car's passenger compartment correlates with the outdoor concentration of pollen. ...
Pollens are responsible for allergic rhinitis, conjunctivitis, and asthma. The incidence of these diseases, which have adversely impacted the social and professional lives of people who are allergic to pollen, has tripled in the past 25 years. Official institutes, health care institutions, public interest groups, and mainstream news media provide people who are allergic to pollen with advice aimed at reducing their symptoms. The aim of this work was to provide an inventory of the prevention guidelines in the world and to evaluate their scientific relevance. A PubMed search was carried out using specific keywords. The scientific relevance of the recommendations was evaluated based on the publications disproving or confirming their merit. The guidelines issued by 12 countries in Europe, North America, and Australia were inventoried. The recommendations for avoidance were most often based on scientific data regarding their impact on pollen exposures, but they have not been clinically validated. Several studies provided additional details, however, that allowed the guidelines to be further substantiated. These guidelines have been adopted in numerous industrialized countries in the world, and they generally appear to be of relevance.
... Several works have confirmed that pollen grain concentrations are frequently higher outdoors compared to indoors [54,55], effect that can be exacerbated in our case because of the urban park nearby. Even a negative gradient from the window to inner places in the same room have been described [56], which may be related to the large size of the pollen grains (usually >20 μm). ...
Full-text available
Natural passive ventilation (windows opening) is frequently used in many houses and old buildings to renovate the air, remove unpleasant odors and dust, and reduce the physicochemical pollutants indoor. However, little is known about the effect on biological particles such as pollen grains and fungal spores (both allergenic) or bacteria (potentially infectious and pathogenic). In the present research, the bioaerosols composition in a small room naturally ventilated was analyzed by high-throughput DNA sequencing. Pollen grains were the most abundant particles outdoors while microbial phyla Actinobacteria, Firmicutes, Proteobacteria and Ascomycota were predominant indoors. The main divergences in bioaerosols between indoor and outdoor environments were caused by the different abundance of the biological particles rather than the different taxa composition. Keeping the window open for 2 h did not change significantly the microbial community present indoors, although there was a tendency to mix the components of both environments. The abundance of human-related and potentially harmful microorganisms was higher indoors and was not remarkably affected by natural ventilation. In our study, natural ventilation through window opening had a poor effect on removing these microorganisms from the atmosphere indoor, suggesting that additional mechanisms such as air filtering systems would be required in order to improve the air quality of these environments from a microbiological point of view.
... It is essential to improve pollen monitoring techniques and to implement automatic methods, favoring the use of personal pollen samplers and the application of molecular methodologies [83], and taking into account the role of occupants as a potential cause of indoor pollen level variation, as highlighted in previous studies [19,66,67] and in the current study, conducted in two different occupational settings. The important role of human behavior in pollen diffusion and/or retention has also been evidenced by experimental studies, where a mean of 0.93% of the initial pollen load was retained after a single wash of hands and traces of several species were found after numerous hand-wash cycles [84]. ...
Full-text available
Pollen exposure in occupational settings involves different categories of workers. In this paper the effects of diurnal pollen variations have been evaluated in two sites characterized by different vegetation and urbanization: the suburban site of Tor Vergata (TV) and the rural site of Monte Porzio Catone (MPC). Aerobiological and meteorological monitoring was performed in the two sites during the winter of 2017. The data analysis focuses on the comparison between pollen concentrations observed in relation to meteorological variables. In general, it can be stated that the indoor and outdoor dynamics for MPC and TV are different, with the outdoor concentration of pollen for MPC always higher than for TV, in accordance with significant presence of vegetation. The high nocturnal peaks detected in MPC and completely absent in TV could be caused by the presence of particular conditions of stagnation combined with greater emissions from the pollen sources. Furthermore the higher I/O ratio observed during the working hours in TV compared to MPC could be ascribed to the workers’ behavior. Exposure to pollen can be responsible for several health effects and the knowledge of its level can be useful to improve the evaluation and management of this biological risk.
The urban atmosphere carries biological particles (bioaerosols) that may cause several diseases and allergies. These bioaerosols infiltrate and mix with those present inside the buildings, including hospitals. However, little is known about the behavior of these particles around health facilities. Here, we described the bioaerosols composition of an urban hospital indoor and outdoor at two different periods (winter and summer) using DNA sequencing. We observed that the seasonality and composition of the bioaerosols outdoor was also displayed indoor, and, in some cases, the taxa showed different trends depending on the season. Pathogenic species of bacteria and fungi were found indoors at low levels but also outdoors, being mostly environmental species, which would reject the idea that hospitals may be acting as a source of emission via aerosols. Skin-related bacteria were the most prevalent group related to human microbiome, being more abundant indoors. Air temperature was the principal factor affecting the bioaerosols composition in the samples but, in general, meteorological parameters outdoors were poor descriptors of the bioaerosols indoors. Similarly, the concentrations of the main indoor air pollutants did not correlate with microbial abundances. Globally, natural ventilation through a window opening did not significantly alter the composition of the bioaerosols indoor.
Pollen from Parthenium weed is a well-known aeroallergen. Infestation of Parthenium weed is found in many countries including Taiwan, especially in central and southern regions. Most houses in Taiwan are equipped with window screens to keep flies and mosquitoes away. Natural ventilation would allow pollens to infiltrate indoors. Hence, preventing pollen infiltration would be a strategy for allergic disease control. A full-scale exposure chamber comprising a main (outdoor) cabin and an auxiliary (indoor) cabin connected by six types of window screen was used in the test. In both cabins, two Burkard samplers continuously collected pollens emitted from Parthenium hysterophorus weed. The filtration efficacy of different window screens under three wind velocities were assessed by counting the number of pollens in both cabins using an optical microscope. Light transmittance was evaluated by picturing the parthenium plant behind the different screen materials. Natural ventilation performance in the two cabins was evaluated using a vane anemometer. Protective window screen D made of long-lasting electrostatic fiber with high pollen filtration efficacy, adequate ventilation, and clear visibility is recommended for naturally ventilated residential buildings, especially for allergic individuals.
Full-text available
Indoor air quality depends on many internal or external factors mutually interacting in a dynamic and complex system, which also includes indoor workplaces, where subjects are exposed to many pollutants, including biocontaminants such as pollen and fungal spores. In this context, the occupants interact actively with their environment through actions, modifying indoor environmental conditions to achieve their own thermal comfort. Actions such as opening/closing doors and windows and turning on/off air conditioning could have effects on workers’ health. The present study explored the contribution of human occupants to pollen and fungal spore levels in indoor workplaces, combining aerobiological, microclimate, and worker monitoring during summer and winter campaigns. We evaluated the overall time spent by the workers in the office, the workers’ actions regarding non-working days and working days, and non-working hours and working hours, during two campaigns of pollen and fungal spore monitoring. Our results showed that the biocontaminant values depend on many mutually interacting factors; hence, the role of all of the factors involved should be investigated. In this regard, aerobiological monitoring should be a valid tool for the management of occupational allergies, providing additional information to improve occupational health protection strategies.
Full-text available
Despite the progress made in recent years, reliable modeling of indoor air quality is still far from being obtained. This requires better chemical characterization of the pollutants and airflow physics included in forecasting tools, for which field observations conducted simultaneously indoors and outdoors are essential. The project “Integrated Evaluation of Indoor Particulate Exposure” (VIEPI) aimed at evaluating indoor air quality and exposure to particulate matter (PM) of humans in workplaces. VIEPI ran from February 2016 to December 2019 and included both numerical simulations and field campaigns carried out in universities and research environments located in urban and non-urban sites in the metropolitan area of Rome (Italy). VIEPI focused on the role played by micrometeorology and indoor airflow characteristics in determining indoor PM concentration. Short- and long-term study periods captured diurnal, weekly, and seasonal variability of airflow and PM concentration. Chemical characterization of PM10, including the determination of elements, ions, elemental carbon, organic carbon, and bioaerosol, was also carried out. Large differences in the composition of PM10 were detected between inside and outside as well as between different periods of the day and year. Indoor PM composition was related to the presence of people, to the season, and to the ventilation regime.
Purpose: Pollen may spread indoors through clothes contaminated during outdoor activities. This study aimed to evaluate the pollen removal efficacy of a mechanical dryer. Methods: Cotton clothes served as laundry, and fabrics measuring 2 × 5 cm served as test samples. Pollen was spread evenly on the test fabrics. The fabrics were then fixed on the cloth and left for 8 h to imitate real-life conditions. This experiment was conducted under 2 conditions, wet (after washing clothes) and dry (without washing). After drying, we counted pollen on the test fabrics to evaluate the pollen removal rate. We measured the remaining allergens in extracts from the contaminated fabrics after mechanical drying. The concentrations of allergens (Amb a 1, Bet v 1, Crp j 1, and Phl p 1) in each extracted solution were measured using 2-site ELISA. Results: For ragweed, Japanese cedar, birch, and timothy grass, the mean pollen removal ratios for the dry samples were 99.88 ± 0.09%, 99.96 ± 0.03%, 99.89 ± 0.02%, and 99.82 ± 0.11%, respectively, and those for the wet samples were 98.83 ± 0.87%, 97.91 ± 1.81%, 97.29 ± 1.19%, and 96.3 ± 0.92%, respectively. Further, for the pollen allergens Amb a 1 [ragweed], Crp j 1 [Japanese cedar], Bet v 1 [birch], and Phl p 1 [timothy grass], the mean pollen allergen removal ratios for the dry samples were 99.81 ± 0.06%, 99.94 ± 0.23%, 99.90 ± 0.11%, and 99.84 ± 0.17%, respectively, and those for the wet samples were 98.11 ± 0.14%, 96.04 ± 1.52%, 97.21 ± 0.83%, and 95.23 ± 0.92%, respectively. There was no statistically significant difference for each species. Conclusions: Mechanical drying effectively removed pollen and allergens from dry and wet fabrics. We expect that further studies on the removal of other indoor allergens would contribute to improved environmental control for allergy patients.
Full-text available
Background: Approximately 16.2% of the Japanese population suffers from pollinosis. One of the forms of management is self-care (preventive care), which can be categorized as 'indoor' and 'outdoor'. Outdoor self-care is usually emphasized, but indoor self-care is also important. Considerable pollen is found in indoor dust and this is thought to be one of the factors that worsens pollinosis and enables it to persistent for a long time, even after the pollinating period has finished. Taking this into consideration, we investigated the dynamic state of indoor pollen. Methods: Floating indoor house dust was collected in Petri dishes. The amount of pollen in the house dust samples collected was measured using an LCD laboratory highly sensitive Cry j1 assay kit. Results: The results showed that, indoors, a lot of Japanese cedar pollen (JCP) was found on the floor (tatami mats, carpets), sofas and curtains. The number of JCP in living rooms peaked in April after the pollinating period and decreased gradually; however, JCP was still found indoors, even as late as the following February. Floating JCP in the house was one-tenth of the JCP levels on the floor. Floating JCP increased on days with low humidity. Air conditioning temporarily increased levels of floating JCP in houses with an air conditioner, but the level of floating JCP decreased rapidly compared with the level of that in houses without an air conditioner. Nasal signs and symptoms disappeared completely at a level of 30 floating pollen counts/day per Petri dish. Conclusion: Considerable JCP was found floating indoors with house dust after a pollinating season.
Full-text available
Although the number of studies of pollen concentrations inside and outside buildings is increasing, little is known about the efficiency of penetration of pollen from outdoor to indoor air, and further. We studied indoor and outdoor pollen concentrations in the town of Lappeenranta and in the municipality of Rautjärvi in SE Finland from May 3–23, 2004, i.e. throughout the Betula pollen season, and assessed the risk of exposure to pollen grains. Pollen concentrations were measured inside and outside a block of flats, a detached house, and the regional central hospital, using rotorod-type samplers; in the town of Joutseno data were compared with Burkard counts. Outdoor concentrations of Betula pollen grains ranged between low and abundant (0–855grainsm−3). The corresponding indoor concentrations near the main front doors varied from low to moderate (0–17grainsm−3) in the central hospital and were low (<10grainsm−3) in both residential buildings. Indoor concentrations further from the main front door were low (<10grainsm−3) at all study sites. The concentrations of Betula pollen decreased substantially from outdoors to indoors, and further toward the centre of the building, probably indicating relatively poor penetrating properties of the pollen grains and/or the short-lived presence of pollen grains in indoor air. The concentrations of Betula pollen inside the buildings during the peak flowering period were mostly at a level barely inducing reactions even in the most sensitive persons.
The purpose of this paper is to quantitatively determine the rate of intrusion of cedar pollen to indoor environment, to estimate the exposure dose and to provide the control measures. Cedar pollens were determined microscopically on settle plates covered with adhesive material in wooden dwellings, flats, and several buildings. The settlements were variable according to the height and position of the rooms. The settlements on the floor were 1.5 to 2 times higher than at the breathing zone and those at just the inside of the windows were 5 to 6 times as much as at the center of the rooms. The rates of settlement were 0.4 to 0.8 p/cm2/day at the center of house and 1.9 to 2.8 at inside of windows. The intrusion rates were about 1.6% at the center of the house, 3.1% at the window and 26% at the places with opened windows. Throughout all the measurements, inside/ outside ratio, which is the simple ratio of settled pollen inside to those outside, was 1 to 2%. The calculated doses inside the room were 1 to 2% of outside. The doses become about twice at the windows and 10 to 20 times at places with opened windows of values at the center of house.
Summary The circadian periodicity of the five allergologically most important pollen types in S. Finland and two different spore types were studied at two sites, about 200 meters apart: one Burkard sampler situated on a roof at a height of 15 meters and the other on a garden lawn at ground level. The circadian rhythms of pollen released close to the ground (herb pollen) did not correlate at the two sampling heights used. Variations in pollen from high sources (trees) were significantly correlated at the two heights used. The circadian rhythms of spores from low source distant from the sampling sites (Suillus as an example of forest fungi) were not always correlated; instead, spores with sources at different heights (Cladosporium as an example) had similar circadian periodicity not depending on the sampling level. It was shown that, when studying circadian rhythms of atmospheric particles, the sampling height used is often of great importance. Circadian rhythms of the same pollen and spore types for ten years at the higher sampling site are presented for long-term comparison.
Three sampling techniques were used to determine how pollen concentrations obtained from atmospheric sampling devices compare to pollen concentrations in the home environment. Burkard pollen samplers were placed on rooftops at 4 locations in Tucson, Az. (USA) to sample regional atmospheric pollen; nearby, Rotorod® (rotorod) samplers collected atmospheric pollen in the home environment at 55 locations for 3 consecutive days during each season. Pollen concentrations from rotorod and Burkard traps show that pollen is rare inside homes and only occurs when pollen production is high. No differences in pollen concentration were found between rooms of any home, and frontyards generally had higher pollen concentrations than backyards. Pollen concentrations near homes were generally lower than regional pollen concentrations. Correlations were low even though pollen taxa were similar. Floor sweepings from homes contained pollen concentrations as high as 5.5 million pollen grains/g house dust. We conclude that little or no pollen gets inside houses through atmospheric transport. Pollen is most likely carried into the houses on the feet and bodies of people and pets.
For frequently two years a period of the range and quantity of pollen grains in the most inhabited rooms of each of 4 dwellings in Sofia was studied, together with the outdoors air pollen spectra. Changes in the health status of the inhabitants affected by pollinosis were recorded at the same time. The characteristic pollen taxa, pollen interference periods and the way sensitive patients were affected were evaluated
A suction trap has been made in which the spores entering a narrow orifice, directed into the wind, are impacted on a Vaseline-coated microscope slide moved across the orifice at 2 mm./hr. Estimates of spore content of the air can be made, with higher efficiency than by previous traps, at different times of day and thus be more closely correlated with variations in weather. Wind-tunnel tests with spores of Lycopodium clavatum showed maximal and minimal efficiencies of 93.8 and 62.4% respectively, with a suction rate of 10.0 1./min., in the range of wind speeds from 1.5 to 9.3 m./sec.
An accurate forecast of the starting point of thebirch pollen season in Neuchtel can be made byadding the positive daily average air temperature fromFebruary 1st onward until the figure 270 is reached.At this point, the birch trees are ready to bloom.After that, the daily average temperature has toexceed 10 C to allow pollen release.Today, the birch pollen season starts some 19 daysearlier in the year than in the 1980's, a consequenceof a recent climate change.The daily patterns of airborne birch pollen isirregular. Moreover, pollen concentrations frequentlyexceed the threshold of the appearance of allergicsymptoms, except during rainfall. Therefore, the onlybehavioral recommendation that can be given to peopleallergic to birch pollen is to shorten as much aspossible the contact with outdoor air during the mainbirch pollen season.
In order to investigate the factors affecting indoor and outdoor microenvironmental concentrations of aeroallergens, and the relationships between them, consecutive 12-hour samples of airborne pollens and spores were collected simultaneously at two fixed ambient air monitoring stations and inside and directly outside of each of 12 houses during the period June–October in Houston. Outdoor concentrations of pollen were spatially less heterogeneous than those of spores, and showed greater seasonal and diurnal variation. Indoor levels of both pollen and spores were uniformly lower than outdoor levels for all 12 air-conditioned homes, with indoor pollen counts on average 30% of outdoor values, and indoor spore counts on average 20% of outdoor values. Indoor levels of both aeroallergens in most homes were not significantly correlated with simultaneous outdoor levels. Variation in exposure to aeroallergens indoors appears largely determined by variations in both infiltration of outdoor air and activities of the household.