Figure 1
Figure 2
Conductivity and skin depth of low and high water content tissues at selected EM RF
| Frequency | Tissues with low water content | Tissues with high water content | ||||||
|---|---|---|---|---|---|---|---|---|
| Fat | Bone | Muscle | Skin | |||||
| σ (S/m) | δ (mm) | σ (S/m) | δ (mm) | σ (S/m) | δ (mm) | σ (S/m) δ | (mm) | |
| 150 MHz | 0.04 | 366.1 | 0.07 | 301.0 | 0.7 | 67.2 | 0.5 | 85.0 |
| 450MHz | 0.04 | 301.9 | 0.10 | 202.2 | 0.8 | 51.3 | 0.7 | 52.9 |
| 835 MHz | 0.05 | 252.0 | 0.14 | 139.5 | 0.9 | 43.5 | 0.8 | 41.5 |
| 1.8 GHz | 0.08 | 157.1 | 0.28 | 66.7 | 1.3 | 29.2 | 1.2 | 28.3 |
| 2.54 GHz | 0.10 | 117.1 | 0.39 | 45.8 | 1.7 | 22.3 | 1.5 | 22.6 |
| 3 GHz | 0,13 | 93.6 | 0.51 | 35.2 | 2.1 | 18.0 | 1.7 | 18.9 |
| 5 GHz | 0.24 | 49.4 | 0.96 | 17.7 | 4.0 | 9.3 | 3.1 | 10.5 |
| 10 GHz | 0.58 | 19.6 | 2.13 | 7.3 | 10.6 | 3.3 | 8.0 | 3.8 |
Basic restrictions for time-varying electric and magnetic fields for frequencies 10 MHz–10 GHz according to the International Commission on Non-Ionizing Radiation Protection (24)
| Whole-body average SAR (W/kg) | Localised SAR (W/kg) | ||
|---|---|---|---|
| Head and trunk | Limbs | ||
| Occupational exposure | 0.4 | 10 | 20 |
| General public exposure | 0.08 | 2 | 4 |
Examples of Wi-Fi exposure in school indoor/classroom environment
| Reference | Country / Sample | Source / Distance from source (m) (Number of measurements) | Electric field strength (V m-1) | Power density (W m-2) | SAR (W/kg) localised (head and trunk) |
|---|---|---|---|---|---|
| Khalid et al. 2011 (55) | United Kingdom / 3 | access points*/ 0.5 | 5.7b | - | |
| Peyman et al. 2011 (19) | primary, 3 secondary schools | laptops / 0.5 | 2.9b | - | 0.00008c |
| Joseph et al. 2010 (56) | Hungary school teacher/ 31 primary d | Wi-Fi devices* | 2-5 | - | - |
| Belgium / 10 schools | 0.05a, 0.24b | - | - | ||
| Vermeeren et al. 2013 (7) | Greece / 5 schools | various Wi-Fi devices*# | 0.09a, 0.20b | - | - |
| Verloock et al. 2014 (111) | Belgium and secondary / 5 primary schools | various access Wi-points Fi clients*# | 0.34a, 2.52b | - | - |
| Gledhill 2014 (59) | New Zealand / 2 schools | access points# / 2 laptops / <0.5 | - | 0.0025a, 0.02b 0.002a, 0.03b | - |
| Karipidis et al. 2017 (54) | Australia 16 secondary / 7 primary schools | access points*# / 1.9 | - | 0.0004a, 0.04b | - |
| Prlić et al. 2021 (10) & Croatia /151 primary Yet unpublished data & secondary schools | access points*# /across the whole classroom (grid 1m x 1m) | < 0.66b | - | 0.0088 #f0.029*f | |
| Relevant ICNIRP reference levels$ | 61 | 10 | 2 | ||