Exposure to extremely low frequency EMF during lessons in secondary schools

2017 · Mixed · Low evidence

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MixedLow evidencePaper 2197

Spot measurements in 60 classrooms across three secondary schools found ELF-MF and ELF-EF exposure levels during lessons were below ICNIRP guideline recommendations. However, 21.67% of classrooms had magnetic field strength above 0.2 µT; the dominant frequenc…

Study snapshot

Publicationmanual · 2017

Study typecross_sectional

Reported directionMixed

Evidence ratingLow

Abstract

Exposure to extremely low frequency EMF during lessons in secondary schools Silangam W, Yoosook W, Kongtip P, Kongtawelert A, Theppeang K. Exposure to extremely low frequency EMF during lessons in secondary schools. Radiat Prot Dosimetry. 2017 Dec 5:1-5. Abstract Schools are a significant location where children are exposed to electromagnetic fields (EMFs), which may cause adverse health effects. This cross-sectional study aimed to examine exposure levels to extremely low frequency magnetic fields (ELF-MFs) with a range of 5 Hz-32 kHz, and ELF-electric fields (ELF-EFs) with a range of 5 Hz-2 kHz in secondary schools in Bangkok, Thailand. This study was conducted in 60 classrooms from three schools during class hours. Spot measurements were taken with a Narda EFA 300 field analyzer to evaluate exposure levels. This study showed that ELF-EMF exposure levels are lower than ICNIRP guidelines, while 21.67% of classrooms had a magnetic field strength above 0.2 μT, and the main sources of ELF-EMFs were electrical equipment and electrical wiring. Future studies should measure ELF-EMF levels in other areas and evaluate the effects of long term exposure to ELF-EMFs on children's health. ncbi.nlm.nih.gov In this study, exposure levels of ELF-MFs and ELF-EFs in classrooms during lessons at all three schools were lower than ICNIRP guideline recommendations. The dominant measured frequency was 50 Hz, and the main sources of ELF-EMFs were electrical equipment and electrical wiring. Future research should focus on the effect of ELF-EMF exposure during school time on children's health, should measure the ELF-EMF intensity in other areas of the school (e.g. library, canteen and walkways) to determine the level of ELF-EMFs both inside and outside the classroom. Moreover, to characterize the exposure of the children to ELF-EMF, measurements should be carried out in the children's bedrooms, where they sleep.

Machine Enhanced Logic

AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typecross_sectional

Effect directionmixed

PopulationSecondary school classrooms (Bangkok, Thailand)

Sample size60

ExposureELF · during class hours (lessons)

Evidence strengthLowConfidence: 78% · Peer reviewed: yes

Main findings

Outcomes measured

ELF magnetic field exposure levels (5 Hz–32 kHz)
ELF electric field exposure levels (5 Hz–2 kHz)
Proportion of classrooms with magnetic field strength >0.2 µT
Dominant measured frequency
Identified sources of ELF-EMFs
Comparison with ICNIRP guideline levels

Limitations

Cross-sectional design
Spot measurements only (not continuous/personal monitoring)
Measurements limited to classrooms during class hours
Only three schools in Bangkok; generalizability unclear
No health outcomes assessed

View raw extracted JSON

{
  "study_type": "cross_sectional",
  "exposure": {
    "band": "ELF",
    "source": "school/classroom electrical equipment and wiring",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "during class hours (lessons)"
  },
  "population": "Secondary school classrooms (Bangkok, Thailand)",
  "sample_size": 60,
  "outcomes": [
    "ELF magnetic field exposure levels (5 Hz–32 kHz)",
    "ELF electric field exposure levels (5 Hz–2 kHz)",
    "Proportion of classrooms with magnetic field strength >0.2 µT",
    "Dominant measured frequency",
    "Identified sources of ELF-EMFs",
    "Comparison with ICNIRP guideline levels"
  ],
  "main_findings": "Spot measurements in 60 classrooms across three secondary schools found ELF-MF and ELF-EF exposure levels during lessons were below ICNIRP guideline recommendations. However, 21.67% of classrooms had magnetic field strength above 0.2 µT; the dominant frequency measured was 50 Hz and main sources were electrical equipment and electrical wiring.",
  "effect_direction": "mixed",
  "limitations": [
    "Cross-sectional design",
    "Spot measurements only (not continuous/personal monitoring)",
    "Measurements limited to classrooms during class hours",
    "Only three schools in Bangkok; generalizability unclear",
    "No health outcomes assessed"
  ],
  "evidence_strength": "low",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "extremely low frequency",
    "ELF",
    "magnetic fields",
    "electric fields",
    "secondary schools",
    "classrooms",
    "Bangkok",
    "Thailand",
    "ICNIRP",
    "exposure assessment",
    "50 Hz",
    "Narda EFA 300"
  ],
  "suggested_hubs": [
    {
      "slug": "school-wi-fi",
      "weight": 0.35,
      "reason": "Study concerns EMF exposure in schools/classrooms (though ELF rather than Wi‑Fi)."
    },
    {
      "slug": "who-icnirp",
      "weight": 0.6,
      "reason": "Exposure levels explicitly compared to ICNIRP guideline recommendations."
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: Not supplied
PubMed: Not supplied

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