疫学研究 (observational study)

[超低周波電磁界にばく露した労働者での酸化ストレスに関する横断的研究] epidem.

A cross-sectional study on oxidative stress in workers exposed to extremely low frequency electromagnetic fields

著者: Li L, Xiong DF, Liu JW, Li ZX, Zeng GC, Li HL

掲載誌: Int J Radiat Biol 2015; 91 (5): 420-425

この研究は、超低周波電磁界（ELF-EMF）にばく露した労働者（変圧器および配電線の点検に従事）をばく露群（n=310）、物流スタッフを対照群（n=300）として、酸化ストレスに関わる種々の血液パラメータを測定した横断研究である。その結果、血中の種々の酵素活性またはマロンジアルデヒドのレベルに有意な差はなかった；リンパ球の小核発生頻度に有意差はなかった､と報告している。

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研究の目的(著者による)

A cross-sectional study was conducted in China to investigate whether exposure to extremely low frequency magnetic fields could induce oxidative stress in workers regularly performing inspection tours close to voltage transformers and distribution power lines.

影響評価項目／リスク推定のタイプ

oxidative stress: plasma total antioxidant capacity, glutathione peroxidase activity, superoxide dismutase enyzme activity, plasma malondialdehyde concentration, micronucleus cell frequency and micronuclei frequency

リスク推定のタイプ:

有病率

ばく露

- 50/60 Hz (AC)
- 磁界
- 送電線
- 変電所
- 職業的

ばく露評価

質問票: main activities during work and non-working periods
測定: spot measurements of the magnetic flux density in the 500 kV and 220 kV transformer stations started 2 m from the authorized entrance of the areas and dotted at the outdoor routes of tour-inspections at 5 m apart and 1.5 m high from the ground; indoor spots dotted in rooms where the inspection staff took rest and in rooms of the administrative staff
計算: 8 h time-weighted average magnetic flux density based on individual record of activities during work

ばく露集団

グループ	説明
参照集団 1	administrative staff: no exposure
集団 2	duration of magnetic field exposure: < 5 years
集団 3	duration of magnetic field exposure: ≥ 5 years
参照集団 4	8 h time-weighted average magnetic field strength: < 1.56 µT
集団 5	8 h time-weighted average magnetic field strength: 1.56 - 7.3 µT
集団 6	8 h time-weighted average magnetic field strength: > 7.3 µT

調査対象集団

グループ:
- 男性
- 女性
年齢: ≥ 18年
特性: employees of power supply company
観察期間: not stated
調査地域: China (Guangzhou)
排除クライテリア: history of present illness, past illness, family heredopathia of mental and cardiovascular diseases

調査規模

タイプ	値
合計	700
評価可能	560

統計学的分析方法:

ANOVA

結論(著者による)

In the 500 kV and 220 kV areas, the magnetic flux density at the spots ranged from 0.62-30.19 µT (median 18.7 µT) and from 0.51-60.11 µT (median 17.7 µT), respectively. In comparison, the magnetic flux density ranged from 0.07 to 0.72 µT with a median of 0.21 µT in the environment of the administrative staff. The 8 h time-weighted average magnetic flux density of the workers was 7.3 µT (1.56-26.3 µT).
No significant changes of the investigated oxidative stress parameters were found between workers that regularly perform inspection tours close to voltage transformers and distribution power lines and administrative staff.
The authors conclude that continual exposure to extremely low frequency electromagnetic fields might not induce oxidative stress in workers from a power supply company.