- Effect of ultraviolet germicidal lights installed in office
ventilation systems on workers' health and wellbeing: double-blind
multiple crossover trial
Dick Menzies, Julia Popa,
James A Hanley, Thomas Rand, Donald K Milton
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Respiratory Epidemiology and Clinical Research Unit, Montreal
Chest Institute (D Menzies MD, J Popa MEng) and Department of
Epidemiology and Biostatistics, McGill University, Montreal,
Canada (D Menzies MD, J A Hanley PhD); Department of Biology,
St Mary's University, Halifax, Nova Scotia, Canada (T Rand PhD);
and Department of Environmental Health, Harvard School of Public
Health, Boston, MA, USA (D Milton PhD)
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Correspondence to: Dr Dick Menzies, Respiratory Epidemiology
Unit, Montreal Chest Institute, McGill University, 1110 Pine
Avenue West, Room 103, Montreal, Quebec, Canada H3A 1A3 (e-mail:dick.menzies@mcgill.ca)
Summary
Background Workers in modern office buildings frequently have
unexplained work-related symptoms or combinations of symptoms.
We assessed whether ultraviolet germicidal irradiation (UVGI)
of drip pans and cooling coils within ventilation systems of
office buildings would reduce microbial contamination, and thus
occupants' work-related symptoms.
Methods We undertook a double
blind, multiple crossover trial of 771 participants. In office
buildings in Montreal, Canada, UVGI was alternately off for
12 weeks, then turned on for 4 weeks. We did this three times
with UVGI on and three times with it off, for 48 consecutive
weeks. Primary outcomes of self-reported work-related symptoms,
and secondary outcomes of endotoxin and viable microbial concentrations
in air and on surfaces, and other environmental covariates were
measured six times.
Findings Operation of UVGI
resulted in 99% (95% CI 67-100) reduction of microbial and endotoxin
concentrations on irradiated surfaces within the ventilation
systems. 771 participants appeared to remain masked, and reported
no adverse effects. On the basis of within-person estimates,
use of UVGI was associated with significantly fewer work-related
symptoms overall (adjusted odds ratio 0·8 [95% CI 0·7-0·99]),
as well as respiratory (0·6 [0·4-0·9])
and mucosal (0·7 [0·6-0·9]) symptoms than
was non-use. Reduction of work-related mucosal symptoms was
greatest among atopic workers (0·6 [0·5-0·8]),
and never-smokers (0·7 [0·5-0·9]). With
UVGI on, never-smokers also had large reduction of work-related
respiratory (0·4 [0·2-0·9]), and musculoskeletal
symptoms (0·5 [0·3-0·9]).
Interpretation Installation
of UGVI in most North American offices could resolve work-related
symptoms in about 4 million employees, caused by microbial contamination
of heating, ventilation, and air-conditioning systems. The cost
of UVGI installation could in the long run prove cost-effective
compared with the yearly losses from absence because of building-related
illness.
Lancet 2003; 362: 1785-91
