Juhasz

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Juhasz

  1. 1. RF Personal Exposimetry onEmployees of Elementary Schools,Kindergartens and Day Nurseries as a Proxy for Child Exposures
  2. 2. Péter JUHÁSZ József BAKOSGyörgy THURÓCZYNational Research Institute forRadiobiology and Radiohygiene Budapest, Hungary
  3. 3. Overview
  4. 4. The Objective:To assess the EMF exposure of children
  5. 5. Difficulties: Hard to work with childrenParental consent/cooperation requiredIncreased risk to expensive PEM units
  6. 6. Workaround: Exposure proxiesMeasure exposure of adults who work in close proximity to children
  7. 7. Specifically:Kindergarten/day nursery caretakers School teachers
  8. 8. They spend part of their worktime in the same microenvironment(same room) as the children they care for
  9. 9. They are expected to receive thesame exposure pattern as the children (at least from base stations and DECT/Wi-Fi sources)
  10. 10. Methods
  11. 11. RF Personal Exposimetry
  12. 12. Exposimeters used:Satimo EME Spy 121Antennessa DSP 090
  13. 13. GSM, UMTS:Separation of uplink (emitted by the phone)and downlink (emitted by the base station)
  14. 14. Measure interval: 15 or 30 s
  15. 15. Volunteer groups:
  16. 16. Group Children age n  Kindergarten caretakers 3–6  Day nursery caretakers 50 1–3  School teachers 6–14 30 (n=60 in 2009 and n=20 in 2010)
  17. 17. Activity diary
  18. 18. Each entry consists of: Description Start of activity Activity type Comment
  19. 19. Activity types
  20. 20. WorkHomeSleepTravelOther
  21. 21. WorkHomeSleepTravelOther
  22. 22. Example graph
  23. 23. Activity type 10 Work TV among children courtyard microwave oven mobile walk cooking mobile SMS computer microwave washing machine, drier Home 5 Sleep Travel 2Electric field [V/m] Other 1 FM TV VHF 0.5 TETRA TV UHF GSM 900 Phone GSM 900 Base 0.2 GSM 1800 Phone GSM 1800 Base 0.1 DECT UMTS Phone 0.075 UMTS Base 0.05 WLAN 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 08:00 Time [h:m]
  24. 24. Manual evaluation of diaries
  25. 25. Every diary entry was carefully examined and marked 0–5 as a level of certainty thatthe volunteer was actually near children during that period
  26. 26. 5 explicitly stated as such not explicitly stated,4 but can be inferred3 probably2 not likely, but possibly1 unlikely0 unrelated activity
  27. 27. Activity type 10 Work TV among children courtyard microwave oven mobile walk cooking mobile SMS computer microwave washing machine, drier Home 5 Sleep Travel 2Electric field [V/m] Other 1 FM TV VHF 0.5 TETRA TV UHF GSM 900 Phone GSM 900 Base 0.2 GSM 1800 Phone GSM 1800 Base 0.1 DECT UMTS Phone 0.075 UMTS Base 0.05 WLAN 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 08:00 Time [h:m]
  28. 28. Manual evaluation:tedious, involves a lot of guesswork
  29. 29. Simplified evaluation:Every entry marked as Work
  30. 30. Further simplified evaluation: Every data point between 8:00 – 16:00
  31. 31. Results
  32. 32. Number of acceptabledata points as a function of category and grouping
  33. 33. Number of acceptable data points 250000 All 2009 2010 Kindergarten School 200000 150000n 100000 50000 10000 0 all 8-16 work 1 2 3 4 5 all 8-16 work 1 2 3 4 5 all 8-16 work 1 2 3 4 5 all 8-16 work 1 2 3 4 5 all 8-16 work 1 2 3 4 5
  34. 34. Ratio of pointsabove detection limit
  35. 35. Hardware limitation:detection limit of 0.05 V/m
  36. 36. Points above det. limit: GSM 900 Base Station 100 All 2009 2010 Kindergarten School 80 60% 40 20 0 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5
  37. 37. Points above det. limit: GSM 900 Phone 100 All 2009 2010 Kindergarten School 80 60% 40 20 0 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5
  38. 38. Points above det. limit: GSM 1800 Base Station 100 All 2009 2010 Kindergarten School 80 60% 40 20 0 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5
  39. 39. 5 4 3 School 2 1 rk wo 6 8-1 5 Kindergarten 4 3 2Points above det. limit: WIFI 1 rk wo 6 8-1 5 4 3 2 1 rk 2010 wo 6 8-1 5 4 3 2009 2 1 rk wo 6 8-1 5 4 3 2 All 1 rk wo 6 100 8-1 80 60 40 20 0 %
  40. 40. Descriptive statistics
  41. 41. GSM 900 Base Station All 2009 2010 Kindergarten School 2 1E [V/m] 0.5 0.2 0.1 0.05 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 Max Upper quartile Median Lower quartile Mean 90th Percentile 95th Percentile Min
  42. 42. GSM 1800 Base Station All 2009 2010 Kindergarten School 2 1E [V/m] 0.5 0.2 0.1 0.05 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 Max Upper quartile Median Lower quartile Mean 90th Percentile 95th Percentile Min
  43. 43. WIFI 10 All 2009 2010 Kindergarten School 2E [V/m] 1 0.5 0.2 0.1 0.05 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 8-1 wo 6 1 rk 2 3 4 5 Max Upper quartile Median Lower quartile Mean 90th Percentile 95th Percentile Min
  44. 44. Other frequencies:Negligible exposure from TV, TETRA, UMTS DECT: negligible, but simplified evaluation overestimates FM: Above-DL but low exposure
  45. 45. Comparison by frequencies
  46. 46. Category 5 datapoints only as the best quality data for estimating exposure of children
  47. 47. Comparison by frequencies: Only points in category 5 All volunteers 10 2E [V/m] 1 0.5 0.2 0.1 0.05 900 1800 UMTS 900 1800 UMTS DECT WIFI FM Base station Phone Max Upper quartile Median Lower quartile Mean 90th Percentile 95th Percentile Min
  48. 48. Discussion
  49. 49. Quality of exposure diaries varyInformation given by volunteers often incorrect or misleading
  50. 50. Data quality is problematic
  51. 51. Robust ROS: method to estimate unbiased mean and SD of a left-censored dataset Röösli et al, BEMS 2008, 29:471-478.
  52. 52. Attempted, with inconclusive results(Too many points below DL)
  53. 53. Only a fraction of the full dataset usable for estimation of exposure of children (n ≈ 4800 out of 265000)
  54. 54. To get that usable dataset, diaries have to be manually evaluated
  55. 55. Simplified evaluation oftenunder- or overestimates exposure
  56. 56. Recommendations
  57. 57. The better the diaries,the easier to work with them → Better quality data
  58. 58. Proper instruction of volunteers is essential

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