Study type: Epidemiological study (observational study)

A new electromagnetic exposure metric: high frequency voltage transients associated with increased cancer incidence in teachers in a California school. epidem.

Published in: Am J Ind Med 2008; 51 (8): 579-586

Aim of study (acc. to author)

The aim of the study was to investigate the cancer incidence in teachers of a school in California, USA in relation to the school's electrical environment.

Further details

A new exposure metric (GS unit) introduced in this investigation is measured by a meter. It displays the average rate of change of high frequency voltage transients existing everywhere on electrical power wiring. Overload reading was defined as more than 2000 GS units, e.g. the average magnitude of the rate of change of voltage as a function of time.

Endpoint/type of risk estimation

Type of risk estimation: (relative risk (RR))

Exposure

Assessment

Exposure groups

Group Description
Group 1 teacher never taught in a classroom with at least one overload reading
Group 2 teacher never taught in a classroom with at least one overload reading and employed less than 10 years
Group 3 teacher never taught in a classroom with at least one overload reading and employed more than 10 years
Group 4 teacher ever taught in a classroom with at least one overload reading
Group 5 teacher ever taught in a classroom with at least one overload reading and employed less than 10 years
Group 6 teacher ever taught in a classroom with at least one overload reading and employed more than 10 years

Population

Study size

Type Value
Total 137
Other:

1,576 teacher-years

Conclusion (acc. to author)

16 teachers out of 137 teachers hired in 1988 through 2005 were diagnosed with 18 cancers. The relative risk for all cancers was 2.78 and for malignant melanomas 9.8. The relative risk for thyroid cancer was 13.4 and for uterine cancer 9.2.60 Hz magnetic fields showed no association with cancer incidence. A new exposure metric showed a positive correlation to cancer incidence.
The authors concluded that the cancer incidence of teachers at this school is unusually high and is strongly associated with high frequency voltage transients.

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