Measurement of personal radio frequency exposure in Japan: The Hokkaido Study on the Environment and Children's health

Abstract

Measurement of personal radio frequency exposure in Japan: The Hokkaido Study on the Environment and Children's health Yamazaki K, Ikeda-Araki A, Miyashita C, Tamura N, Yoshikawa T, Hikage T, Omiya M, Mizuta M, Ikuyo M, Tobita K, Onishi T, Taki M, Watanabe S, Kishi R. Measurement of personal radio frequency exposure in Japan: The Hokkaido Study on the Environment and Children's health. Environ Res. 2022 Sep 26:114429. doi: 10.1016/j.envres.2022.114429. Abstract The opportunities for exposure to radiofrequency electromagnetic fields (RF-EMF) among children are increasing. Children's exposure to RF-EMF in Japan was recorded using a personal exposure meter (ExpoM-RF), and factors associated with the exposure examined. A total of 101 children, aged 10-15 years old, participated in the prospective birth cohort "Hokkaido study". RF-EMF data were recorded in the 700 MHz-5.8 GHz frequency range for 3 days. The recorded data were summarized into six groups of frequency bands: downlink from mobile phone base stations (DL), uplink from mobile phones to a base station (UL), Wireless Local Area Network (LAN), terrestrial digital TV broadcasting (digital TV), 2.5 GHz and 3.5 GHz Time Division Duplex (TDD), 1.9 GHz TDD, and total (the summation of power density in all measured frequency bands). A questionnaire was used to document the internet environment (at home) and mobile phone usage. Personal RF-EMF exposure in Japanese children was lower than that reported in studies in Europe. The DL signals from mobile phone base stations were the most significant contributors to total exposure, while Wireless LAN and digital TV were only higher at home. The urban residence was consistently associated with increases in the four groups of frequency bands (DL, UL, digital TV, and TDD). TDD level has several associations with mobile phone usage (calls using mobile phones, video viewing, text message service, and online game). The association between inattention/hyperactivity subscale of the Strengths and Difficulties Questionnaire (SDQ) and higher Wireless LAN exposure at nighttime was also noted. Further studies with additional data will shed light on factors involved in RF-EMF exposure among Japanese children. Excerpts Regarding microenvironments, RF exposure from outdoor environmental sources was higher when outdoors than indoors, similar to findings of other studies (Birks et al., 2018; Gallastegi et al., 2018; Joseph et al., 2010; Verloock et al., 2014). The exposure levels for DL, digital TV from outdoor environmental sources (e.g. base station) were higher outside, and that in Wireless LAN was higher in the home. Regarding the contribution of each band to the total exposure level, the exposure to the DL contributed the most to the total exposure in all microenvironments.... ... Interestingly, Wireless LAN levels at nighttime were significantly higher among those with high hyperactivity/inattention scores of SDQ, one of the common symptoms of ADHD, than those with low scores. Although the association between ADHD symptoms and internet addiction has been reported (Ho et al., 2014; Wang et al., 2017; Yen et al., 2009), there was no relationship between internet addiction and RF-EMF exposure in the present study. Tateno et al. (2016) suggested that ADHD traits, such as impulsivity, could be related to difficulty in controlling internet use and online gaming. Therefore, the exposure to Wireless LAN recorded by the exposure meter might increase for those who could not limit the use of wireless electrical devices (mobile phones, gaming devices, among others) at nighttime because of impulsivity, rather than internet addiction.... Conclusions We recorded children’s personal RF-EMF exposures using the exposure meter and examined related factors for their exposure. The personal RF-EMF exposure in Japanese children was lower than that reported in previous European studies. Downlink from mobile phone base stations was the most significant contributor to the total exposure, while Wireless LAN and digital TV were higher at home than in other microenvironments. There were several significant associations between internet environment and mobile phone usage and exposure level in the daytime analysis. Among them, the urban residence and related characteristics were consistently associated with higher levels of DL, UL, digital TV, and TDD band. At nighttime, the association between the inattention/hyperactivity subscale of SDQ and Wireless LAN exposure was found in addition to associations between the internet environment or mobile phone usage and the RF-EMF exposure. Further studies with additional data and robust study designs are required to explore the most possible factors involved in RF-EMF exposure among Japanese children. pubmed.ncbi.nlm.nih.gov

AI evidence extraction

Main findings

Personal RF-EMF exposure in these Japanese children (measured over 3 days, 700 MHz–5.8 GHz) was reported as lower than in European studies. Downlink signals from mobile phone base stations were the largest contributors to total exposure; WLAN and digital TV exposures were higher at home. Urban residence was consistently associated with higher exposure in several bands (DL, UL, digital TV, TDD), and higher nighttime WLAN exposure was noted among children with higher SDQ inattention/hyperactivity scores.

Outcomes measured

• Personal RF-EMF exposure (power density) across 700 MHz–5.8 GHz
• Exposure contributions by band group (DL, UL, WLAN, digital TV, TDD bands, total)
• Associations of exposure with microenvironments (home/indoors/outdoors)
• Associations of exposure with urban residence
• Associations of exposure with home internet environment and mobile phone usage
• Association between SDQ inattention/hyperactivity subscale and nighttime WLAN exposure

Limitations

• Abstract does not report detailed exposure metrics (e.g., medians/means, distributions)
• Comparisons to European studies are not quantified in the abstract
• Associations reported; causal inference not supported by the abstract
• Further studies with additional data and more robust designs are stated as needed

Suggested hubs

• school-wi-fi (0.32)
  Assesses Wireless LAN (Wi‑Fi) exposure in children (including nighttime/home context).
• occupational-exposure (0)
• 5g-policy (0.22)
  Includes 3.5 GHz TDD measurements (relevant to newer cellular bands), though framed as exposure assessment rather than policy.

{
    "study_type": "exposure_assessment",
    "exposure": {
        "band": "RF",
        "source": "personal exposure (multiple sources including mobile phone base stations, mobile phones, WLAN, digital TV)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "3 days"
    },
    "population": "Children in Japan aged 10–15 years (participants in the Hokkaido prospective birth cohort)",
    "sample_size": 101,
    "outcomes": [
        "Personal RF-EMF exposure (power density) across 700 MHz–5.8 GHz",
        "Exposure contributions by band group (DL, UL, WLAN, digital TV, TDD bands, total)",
        "Associations of exposure with microenvironments (home/indoors/outdoors)",
        "Associations of exposure with urban residence",
        "Associations of exposure with home internet environment and mobile phone usage",
        "Association between SDQ inattention/hyperactivity subscale and nighttime WLAN exposure"
    ],
    "main_findings": "Personal RF-EMF exposure in these Japanese children (measured over 3 days, 700 MHz–5.8 GHz) was reported as lower than in European studies. Downlink signals from mobile phone base stations were the largest contributors to total exposure; WLAN and digital TV exposures were higher at home. Urban residence was consistently associated with higher exposure in several bands (DL, UL, digital TV, TDD), and higher nighttime WLAN exposure was noted among children with higher SDQ inattention/hyperactivity scores.",
    "effect_direction": "mixed",
    "limitations": [
        "Abstract does not report detailed exposure metrics (e.g., medians/means, distributions)",
        "Comparisons to European studies are not quantified in the abstract",
        "Associations reported; causal inference not supported by the abstract",
        "Further studies with additional data and more robust designs are stated as needed"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "RF-EMF",
        "personal exposure meter",
        "ExpoM-RF",
        "children",
        "Japan",
        "Hokkaido Study",
        "mobile phone base stations",
        "downlink",
        "uplink",
        "WLAN",
        "Wi-Fi",
        "digital TV",
        "TDD",
        "urban residence",
        "microenvironments",
        "SDQ",
        "inattention",
        "hyperactivity"
    ],
    "suggested_hubs": [
        {
            "slug": "school-wi-fi",
            "weight": 0.320000000000000006661338147750939242541790008544921875,
            "reason": "Assesses Wireless LAN (Wi‑Fi) exposure in children (including nighttime/home context)."
        },
        {
            "slug": "occupational-exposure",
            "weight": 0,
            "reason": null
        },
        {
            "slug": "5g-policy",
            "weight": 0.2200000000000000011102230246251565404236316680908203125,
            "reason": "Includes 3.5 GHz TDD measurements (relevant to newer cellular bands), though framed as exposure assessment rather than policy."
        }
    ]
}

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