Bone marrow transplant wards: movement of airborne bacteria in the presence of electric fields

In addition to my research in the induction of leukaemia, I have been examining the movement of airborne bacteria in the presence of electric fields and its application in the related field of bone marrow transplant wards.

Bone marrow transplant patients are nursed in a protected environment. The chemotherapy and radiotherapy treatment has a profound effect on the recipient's immune system, so that a high proportion of them develop potentially life-threatening infections. We are investigating the possible role played by static electric charge acquired by different plastic medical devices in mediating some of these infections.

The attraction of radon decay products to sources of power frequency electric fields has been demonstrated by Henshaw et al (1996). Since these radioactive decay products are attached to natural aerosol particles, their behaviour reflects that of aerosols of any kind in the size range ~0.01 to ~0.6 microns. This has implications for exposure to pollutant non-radioactive aerosols in the environment in relation to proximity to sources of electric fields. Theoretically, viruses which fall in a similar size range should also be attracted to such sources and it is expected that arger airborne agents such as bacteria and fungi (~1 to ~10 microns) may demonstrate a similar action.

bacteria attached to a skin squame

Bacteria attached to a skin squame

The attraction of dust to TV and VDU screens is an everyday observation, but the attraction of particles of a specific size range does not appear to be well investigated. Sources of static electricity are commonplace in home and office environments. The possible adverse health effects of VDU screens has been extensively discussed in the literature. Some reports of 'sick building syndrome' have associated adverse health effects such as skin rashes, itching and respiratory disorders with self reported exposure to static electricity.

increased deposition with increased voltage

Increased deposition with increased voltage

Airborne bacteria in a domestic situation are usually a reflection of man's activity. Staphylococci are found in all individuals, but with variations in carriage between age groups and populations. Aerosol particles shed from the human body are, first, droplets expelled from the respiratory tract through the nose and mouth. They consist of liquid which may surround infective material and second, skin squames which are constantly being lost from the skin surface. The number of skin scales liberated is of the order of 7 million per minute, based on an equivalent diameter of 14 microns and a body surface of 1.8 m2.

increased deposition at the edge of the -2 kV plate

Increased deposition at the edge of the -2 kV plate and in air close to the plate

Special filters were used to collect airborne bacteria. for 50 Hz, filters were placed vertically against wires carrying 230 V and 2 kV potentials. For DC, filters were placed on metal plates hanging vertically in air carrying potentials of ± 4, ± 3, ± 2 or ± 1 kV and a grounded control. Deposition of airborne bioaerosols was proportional to the voltage.

increased deposition at AC wire

Increased deposition of bacteria at AC wire

Reference

Static electric charge may contribute to infections in bone marrow transplant wards
Allen JE, Henshaw DL, Wynne H, Ross F and Oakhill A, 2003
Journal of Hospital Infection, 54(1), 80-81

Biological aerosols, static charge and hospital infection
Allen JE, Wynne H, Ross F, Henshaw DL and Oakhill A. 2001
In: Aerosols, Their generation, Behaviour and Applications. pp99-102
Twelfth Annual Conference of The Aerosol Society
Bath University 18-19 June, 2001. ISBN 0 9529777 6 1

Enhanced deposition of radon daughter nuclei in the vicinity of power frequency electromagnetic fields.
Henshaw DL, Ross AN, Fews AP and Preece AW., 1996
International Journal of Radiation Biology, 69, No.1, 25-38