The persistence of dust in occupied rooms

Abstract

Various factors are involved in determining the possible role of dust as a vehicle of infection. We know something about the rate at which bacteria from mouth and nose are contributed to dust (Bourdillon, Lidwell & Lovelock, 1942;Hamburger, Green & Hamburger, 1945; Duguid, 1946;Dumbell, Lovelock & Lowbury, 1948). We also have information on the death-rate of such bacteria in dust under various environmental conditions (Cornet, 1889;Garrod, 1944; Lidwell & Lowbury, 1950). It would be a further link in the chain of evidence to know how quickly dust is removed from occupied rooms. An attempt to obtain such information is described in this paper. METHODSSmall amounts of insoluble fluorescein were dispersed from an insufflating bottle into the air of twelve bedrooms used by volunteers at the Common Cold Research Unit. On the following day the volunteers were asked to sweep and collect the dust from the floor of their bedrooms, and to continue doing so daily. The complete sweepings each day were weighed and extracted by shaking in bottles containing 10 ml. of decinormal sodium hydroxide and glass beads. After 10 min. centrifugation at 2000 r.p.m. the supernatant was removed, and the fluorescence of a suitable dilution was matched in daylight against a standard range of fluorescein solutions.The optimum range in the fluorescein standard was between the 9th and 15th tubes in a series of doubling dilutions of 0 05 g. 'insoluble' fluorescein dissolved in 10 ml. decinormal sodium hydroxide. The dilutions were colourless when held up to the light but were clearly fluorescent. More concentrated solutions were coloured and showed little obvious difference in fluorescence in adjacent tubes. Matching of dust samples containing little fluorescein was difficult because of the green or brown colour of undiluted extracts. Quantitative assessment of these specimens was impossible, and where fluorescence was obvious they were recorded as containing a 'trace'.The physical properties of fluorescein cannot be assumed to correspond with those of house dust. An attempt was made to overcome this difficulty by saturating a piece of blanket material in a concentrated solution of fluorescein in decinormal sodium hydroxide, washing the blanket in decinormal hydrochloric acid to precipitate fluorescein, and then in water to rinse. The blanket was dried in the incubator at 370 C., and then beaten vigorously in two of the volunteers' bedrooms. As the duist obtained from bedrooms contains a large proportion of recognizable J. Hygiene

Introduction: the first 100 years

“…But to understand some of the problems of hospital infection in the preantibiotic era, the paper by Wright [17] provides some perspective on modern problems. Similarly, if modern commentators were more aware of the work by Lidwell and Lowbury [18][19][20][21][22] on the role of dust in hospital infection, some of the discussions on the cleaning of hospitals would have a more rational basis.…”