Medical/biological study (observational study)

Natural killer cell activity decreases in workers occupationally exposed to extremely low frequency magnetic fields exceeding 1 microT med./bio.

By: Gobba F, Bargellini A, Bravo G, Scaringi M, Cauteruccio L, Borella P

Published in: Int J Immunopathol Pharmacol 2009; 22 (4): 1059-1066

Aim of study (acc. to author)

To study the possible effects of occupational extremely low frequency magnetic field exposure on natural killer cell cytotoxic activity in peripheral blood cells of workers engaged in different occupational activities not involving any exposure to chemical/physical factors.
The study was performed to confirm previous results with a larger study group (see Gobba et al. 2009).

Background/further details

Individual extremely low frequency magnetic field exposure of all participants (121 workers; 65 men and 56 women) was measured during two consecutive work-shifts using personal dosimeters and environmental, non-occupational exposure was also monitored. Workers were classified as low exposed (62 subjects, TWA ≤ 0,2 µT), medium exposed (35 subjects; 0.21-0.99 µT) and higher exposed workers (24 subjects; TWA ≥ 1 µT).

Endpoint

effects on the immune system: activity of natural killer cells

Exposure

- magnetic field
- low frequency
- occupational

Exposure	Parameters
Exposure 1: unspecified Exposure duration: low exposure group: 12.9 +/- 7.3 years; medium exposure group: 10.0 +/- 6.6 years; high exposure group: 12.0 +/- 8.8 years	magnetic flux density: 0.2 µT average over time (maximum value for the low exposure group) magnetic flux density: 0.21 µT average over time (minimum value for the medium exposure group) magnetic flux density: 0.99 µT average over time (maximum value for the medium exposure group) magnetic flux density: 1 µT average over time (minimum value for the higher exposure group)

Exposure 1

Main characteristics

Frequency	unspecified
Type	magnetic field
Exposure duration	low exposure group: 12.9 +/- 7.3 years; medium exposure group: 10.0 +/- 6.6 years; high exposure group: 12.0 +/- 8.8 years

Exposure setup

Exposure source	occupational exposure + domestic exposure
Additional info	exposure measurement: continuous for 8 h/day on 2 days occupational exposure and 16 h/d domestic exposure

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	0.2 µT	average over time	measured and calculated	-	maximum value for the low exposure group
magnetic flux density	0.21 µT	average over time	measured and calculated	-	minimum value for the medium exposure group
magnetic flux density	0.99 µT	average over time	measured and calculated	-	maximum value for the medium exposure group
magnetic flux density	1 µT	average over time	measured and calculated	-	minimum value for the higher exposure group

Exposed system:

human
whole body

Methods Endpoint/measurement parameters/methodology

effects on the immune system: activity of natural killer cells (detection of target cell (erythroleukemic cell line K562) lysis by chromium-51 release assay)

Investigated system:

isolated bio./chem. substance
blood samples/cell lysates

Investigated organ system:

immune system

Time of investigation:

after exposure

Main outcome of study (acc. to author)

In higher exposed workers (exceeding 1 µT) natural killer cell activity was significantly reduced compared to low exposure group. In the medium exposure group a decrease was also observed, but the difference was not significant.
In conclusion, the data suggest that occupational exposure to extremely low frequency magnetic fields, at least at TWA levels exceeding 1 µT, may induce a decrease in natural killer cell activity in peripheral blood lymphocytes.

Study character:

medical/biological study
observational study
full/main study
blind study for authors involved in NK cell analysis

Study funded by

Istituto Superiore per la Prevenzione e la Sicurezza del Lavoro (ISPESL; National Institute for Occupational Safety and Prevention), Italy

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