The monitoring of indoor air pollution in classrooms

The levels of indoor air pollutants measured in the investigated classrooms in the 100 selected schools from the 10 participating SEARCH countries are presented in Table 2. The same environmental monitoring methodology was used in all the classrooms. According to the project protocol, the same equipment was used during the SEARCH I and SEARCH II environmental monitoring.

TABLE 2 Summary of indoor air measurements in schools under SEARCH I and II

Pollutant

ALB

BIH

BLR

HUN

ITA

KAZ

SRB

SVK

TJK

UKR

PM10
(μg/m3)

69

102

28

56

82

65

81

80

91

33

Formaldehyde
(μg/m3)

5.61

7.13

7.50

2.41

33.07

10.40

1.73

8.71

12.90

11.50

Benzene
(μg/m3)

4.06

6.29

2

2.16

1.95

6.30

5.94

4.84

7.40

2.50

Toluene
(μg/m3)

15.45

27.58

6.20

4.56

5.01

18.10

21.94

29.47

17.40

4.90

Ethylbenzene
(μg/m3)

1.24

1.60

0.90

1.64

1.82

1.60

1.60

1.38

1.50

0.80

Xylenes
(μg/m3)

5.03

7.65

5.90

7.04

7.10

9.10

7.65

5.07

7

4.30

NO2
(μg/m3)

12

21

9.90

16

19

17.30

21

14

13

12

The selected pollutants were measured inside and outside schools in the participating countries during the heating season. The concentrations of BTEX (benzene, toluene, ethylbenzene and xylenes), NO2 and formaldehyde were examined using a passive sampling method (Radiello-type samplers). One sampling point per classroom was designated for indoor measurements and one for outdoor measurements. Samples were collected in classrooms where the children spent most of their time. The passive samplers were placed at a height of 1.5 to 2 m in the classrooms. Outdoors, the passive samplers were placed on the wall of the building closest to the classroom window. Exposed BTEX samples were analysed using the GC-FID method; NO2 samples by spectrophotometer, and formaldehyde samples using HPLC apparatus in Hungary.

The determination of physical parameters, CO2, CO and PM10 was performed via real-time monitoring using the TSI IAQ-Calc Indoor Air Quality Meter (Model 7545-CO/CO2/RH/T) and a Haz-Dust particulate matter (PM10) air monitor. Continuous monitoring over one day during the teaching period was carried out in each classroom and measurements were made of five-minute averages without interval. In parallel, outdoor air pollution was also measured. The monitor was used for 10 minutes outdoors in the morning and again in the afternoon.

Results of air quality measurements

In practice, indoor exposure levels are assessed on the basis of existing guidelines and recommendations. Unfortunately, it was not possible to evaluate indoor air pollution measured during SEARCH I and II in this way due to the differences between the sampling times used in the SEARCH initiative and those specified in the guidelines and recommendations.

Each EU member state sets limit values for workplace environments, but only some member states have guideline values for public places, and limit values for private spaces are very rare. The WHO and other recommendations are presented in Table 3.

TABLE 3 Guidelines and recommendations for concentrations of pollutants in the indoor air

Substance

Unit

Value

averaging time

References

Formaldehyde

µg/m3

100

30 minutes

WHO Guidelines for Indoor Air Quality: Selected Pollutants, 2010

Benzene

µg/m3

No safe level of exposure can be recommended

WHO Guidelines for Indoor Air Quality: Selected Pollutants, 2010

5

annual

Directive 2008/50/EC

Toluene

µg/m3

260

1 week

WHO Air Quality Guidelines for Europe, 2nd edition (2000) – Outdoor

NO2

µg/m3

200
40

1 hour
annual

WHO Guidelines for Indoor Air Quality: Selected Pollutants, 2010

PM10

µg/m3

50

24 hours

WHO Air Quality Guidelines for Particulate Matter, Ozone, Nitrogen Dioxide and Sulphur Dioxide (2005) – Outdoor

CO2

ppm

700 ppm difference between indoor and outdoor concentrations

ASHRAE 62.1-2004

Indoor concentrations of PM10 measured in the classrooms during teaching hours are shown in

Figure 1.

Average one-day indoor PM10 concentrations measured in classrooms in the 10 SEARCH countries during teaching hours

(In Tajikistan, the measurements were made every 5 minutes, and in Italy during 24 hours.)

Average concentrations varied between 28 and 102 μg/m3, although the maximum values were three to four times higher. The lowest concentrations were measured in Belarus and Ukraine. In the other countries, PM10 pollution was very high: in 51 to 98 percent of the examined classrooms PM10 concentrations exceeded 50 μg/m3.

Concentrations of BTEX (benzene, toluene, ethylbenzene and xylenes) in the classrooms, measured over four days, are presented in Figures 2 to 5.

Average benzene concentrations varied between 1.95 and 7.4 μg/m3. The lowest concentrations were found in Belarus, Ukraine, Hungary, Albania and Italy, where the average level was no higher than 5 µg/m3. In 33 to 61 percent of classrooms in Kazakhstan, Tajikistan, Bosnia and Herzegovina, Serbia and Slovakia, the measured benzene concentrations exceeded 5 µg/m3

(
Figure 2).

Indoor levels of benzene measured over four days in classrooms in the 10 SEARCH countries

Average concentrations of toluene showed a wide range (4.6 to 29.5 μg/m3). The highest maximum values were measured in Serbia and Slovakia, where the values were higher than 260 µg/m3

(
Figure 3).

Indoor levels of toluene measured over four days in classrooms in the 10 SEARCH countries

 

Concentrations of ethylbenzene were in the range of 0.8 and 1.82 μg/m3 and maximum values were not high in most of the countries. The highest levels of ethylbenzene pollution were measured in some classrooms in Italy and Hungary (10.88 and 12.9 µg/m3)

(
Figure 4).

Indoor levels of ethylbenzene measured over four days in classrooms in the 10 SEARCH countries

 

Average concentrations of xylenes varied between 4.3 and 9.1 μg/m3, and maximum values were in the range of 15.9 to 69.3 μg/m3 The highest value was measured in a Hungarian classroom.

(
Figure 5).

Indoor levels of xylenes measured over four days in classrooms in the 10 SEARCH countries

 

Concentrations of NO2 and formaldehyde measured over four days in the classrooms are shown in Figures 6 and 7.

Average concentrations of NO2 varied between 9.9 and 22.1 μg/m3, and the maximum value exceeded 40 μg/m3 in Kazakhstan, Bosnia and Herzegovina and Italy

(
Figure 6).

Indoor levels of NO2 measured over four days in classrooms in the 10 SEARCH countries

Average concentrations of formaldehyde varied between 1.7 and 33.07 μg/m3, although maximum values between five and six times higher were also recorded. The highest level of formaldehyde pollution was found in classrooms in Italy

(
Figure 7).

Indoor levels of formaldehyde measured over four days in classrooms in the 10 SEARCH countries

The relationship between indoor and outdoor concentrations is illustrated in

Figure 8.

Relationship between concentrations measured inside the classrooms and outside the schools

The results shown in the figure suggest that the main source of NO2 pollution was the ambient air, and that formaldehyde was primarily emitted from indoor sources.

 
Ministero Dell'ambiente Italian Trust Fund