The claim that visual display units (VDU)-screen filters improve health by
reducing exposure to electrical fields and/or improving screen legibility w
as investigated by introducing VDU screen filters into an office environmen
t. The study design was quasi-experimental, with the first part conducted a
ccording to a simulated control group design with one intervention and one
control group. In the second part, which served as a partly switched replic
ation, the control group also received screen filters. The first group cont
inued their use. The dependent measures were sick leave, productivity. subj
ective symptoms, and musculoskeletal condition. Subjectively reported sympt
om improvement was found in the group that received screen filters during t
he initial part of the study, but that was followed by an aggravation of sy
mptoms during the second part for the same group. No effect was observed in
the control group in either part of the study. The discontinuity observed
between the study parts indicates that factors other than VDU-screen filter
use were responsible for the results. However, the results appear to be ex
plained by subject reactivity, i.e. the Hawthorne effect. The results cauti
on against premature conclusions drawn from short-term interventions and em
phasise the need for a better understanding of the various psychological an
d task-related factors that influence subjects.
Relevance to industry
Visual display units (VDU) are widely used in industry. Knowledge of potent
ial VDU-related health hazards can improve workers health and performance.
(C) 2001 Elsevier Science B.V. All rights reserved.