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  Atmospheric Environment 41 (2007) 5224–5235 The effects of electric fields on charged moleculesand particles in individual microenvironments K.S. Jamieson a,  , H.M. ApSimon a , S.S. Jamieson a , J.N.B. Bell a , M.G. Yost b a Centre for Environmental Policy, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK  b Department of Environmental and Occupational Health Sciences, School of Public Health,University of Washington, Box 357234, Seattle, WA 98040, USA Received 21 February 2006; received in revised form 13 November 2006; accepted 5 February 2007 Abstract Measurements of small air ion concentrations, electrostatic potential and AC electric field strengths were taken in anoffice setting to investigate the link between electric fields and charged molecule and particle concentrations in individualmicroenvironments. The results obtained indicate that the electromagnetic environments individuals can be exposed towhilst indoors can often bear little resemblance to those experienced outdoors in nature, and that many individuals mayspend large periods of their time in ‘‘Faraday cage’’-like conditions exposed to inappropriate levels and types of electricfields that can reduce localised concentrations of biologically essential and microbiocidal small air ions. Such conditionsmay escalate their risk of infection from airborne contaminants, including microbes, whilst increasing localised surfacecontamination. The degree of ‘‘electro-pollution’’ that individuals are exposed to was shown to be influenced by the type of microenvironment they occupy, with it being possible for very different types of microenvironment to exist within the sameroom.It is suggested that adopting suitable electromagnetic hygiene/productivity guidelines that seek to replicate the beneficialeffects created by natural environments may greatly mitigate such problems. r 2007 Elsevier Ltd. All rights reserved. Keywords:  Air ions; Electric fields; Microbes; Charged ultrafine particles 1. Introduction The nature of the electromagnetic environmentsthat most humans are now regularly exposed to haschanged dramatically over the past century andoften bears little resemblance to those created innature. In particular, the increased masking/shield-ing of individuals from beneficial types of naturalelectromagnetic phenomena, the presence of syn-thetic materials that can gain strong charge andincreased exposures to inappropriate electric fieldlevels and polarities have greatly altered theelectromagnetic nature of the microenvironmentsmany individuals usually occupy.Considerable electrostatic and alternating current(AC) electric fields, poor specification of materialsand relative humidity (RH)/dew-point tempera-ture levels, ‘‘Faraday cage’’-like conditions plusfailure to appropriately ground conductive objects ARTICLE IN PRESS www.elsevier.com/locate/atmosenv1352-2310/$-see front matter r 2007 Elsevier Ltd. All rights reserved.doi:10.1016/j.atmosenv.2007.02.050  Corresponding author. Tel.: +442075949263;fax: +442075949334. E-mail address:  keith.jamieson02@imperial.ac.uk(K.S. Jamieson).  (including humans), can create highly localisedincidents of electromagnetic pollution capable of significantly reducing concentrations of biologicallyvital and microbiocidal small air ions (SAI), suchas charged oxygen. Evidence (Ghaly and Teplitz,2004; Altmann, 1974, 1969; Barron and Dreher, 1964; Lang, 1972a,b; Kritzinger, 1957) indicates that if the body is exposed to poorly designedelectromagnetic environments it is more prone todemonstrate reduced activity levels, oxygen uptakeand performance, whilst potentially increasingstress and likelihood of succumbing to degener-ative illnesses. Research by Cohen et al. (1998)also suggests that in certain instances electromag-netic pollution can increase the body’s alveolarburden of potentially harmful particulate matter byenhancing retention rates of contaminants wheninhaled. 2. Background  2.1. Charged molecules (small air ions) These are also known as fast air ions or clusterions and are charged gaseous molecules that canpossess complex geometries. Negative cluster ionsare 0.36–0.85nm in size with mobilities of 1.3–3.2cm 2 V  1 s  1 , whilst positive cluster ions are0.85–1.6nm in size with mobilities of 0.5–1.3cm 2 V  1 s  1 . Their average lifetime is be-tween 50 and 250s, depending on the aerosolcontent of the air. They have a complicated andvaried chemical nature, usually independent of nearby aerosols, which normally changes severaltimes a second. They each possess a singleelementary charge of 1.6  10  19 C, and theirdirection of movement is greatly influenced byelectric fields, with a large degree of attractionbeing shown towards opposite or ‘‘mirror’’ charges.They are repelled by charges of similar polarity andattracted to those of opposite polarity. Both smallnegative and small positive air ions have beenshown to be microbiocidal, further details are givenin Jamieson and Jamieson (2006). Whilst prolongedlong-term exposure to unipolar negative ionisationappears capable of shortening life-span (Kelloggand Yost, 1986), experiments by Goldstein andArshavskaya (1997), indicate that charged oxygenappears vital to life and that animals can diewithin weeks of being completely deprived of thisform of SAI.  2.2. Charged particles 2.2.1. Intermediate and large air ions These are solid or liquid charged aerosol parti-cles/ultrafine particles. Both long- and short-termexposures to elevated concentrations of such parti-cles are associated with raised admissions tohospital and premature death. At present, they areseldom measured in air pollution or air ion studies.Intermediate air ions are 1.6–7.4nm in size withmobilities of 0.034–0.5cm 2 V  1 s  1 and are nor-mally present in far lower numbers than large airions. There are two main types of large air ions (alsoknown as slow ions because of their lower mobility).Light large air ions are 7.4–22nm in size and havemobilities of 0.0042–0.034cm 2 V  1 s  1 , whilst heavylarge air ions (charged Aitken particles) are22–79nm in size and have mobilities of 0.00087–0.0042cm 2 V  1 s  1 . Both follow air-streamflows like uncharged aerosols unless very largeelectric fields are present. Their chemical nature issimilar to that of uncharged aerosols, and they canpossess more than one elementary charge. Increas-ing charge increases their likelihood of depositionon oppositely charged surfaces (Dolezalek, 1985).  2.2.2. Charged ultrafine particles These are charged particles of particulate matter o 0.1 m m (100nm) in size and are classed as PM 0.1 .Ultrafine particles can induce greater cytotoxicityand epithelial damage than fine particles composedof similar materials, partially due to their far greatersurface area per given mass, a factor which can alsoincrease their ability to carry toxic co-pollutants.  2.2.3. Charged fine particles These are charged particles from 0.1 to o 2.5 m min size. Electrical effects can predominate as atransport and deposition mechanism for particles p 1 m m in size (McMurry and Rader, 1985).Particles  p 1 m m in size can greatly exacerbatehealth problems. In excess of 90% of PM 10  particlescan be in this size range (Rao et al., 2005). Suchparticles can be composed of dust, lint, tobaccosmoke, diesel soot, fresh combustion particles,ozone and terpene-formed aerosols, nitrates andsulphates, heavy metals, mineral fines, respiratorydroplets, skin squamae and a variety of othersubstances. Airborne biological contaminants inthis size range include allergens, bacteria, fungalspores and viruses. The greater the charge theypossess the higher the likelihood of their deposition. ARTICLE IN PRESS K.S. Jamieson et al. / Atmospheric Environment 41 (2007) 5224–5235  5225   2.3. Alternating current (AC) electric fields AC fields are measured in volts per metre (Vm  1 )and can be created by high-voltage power lines,electrical wiring and items of electrical equipment.They increase in strength as voltage is raised. Whilstelectrical equipment has to be switched on beforemagnetic fields are registered, electric fields can bedetected even if the equipment is switched off butnot unplugged from the mains power socket.Frequencies within the range being measured inthe present case study (10–2000Hz 7 3dB) can bebiologically active (Lang, 1972a,b).  2.4. Electrostatic fields Under natural fair weather conditions an electro-static vertical potential gradient of 100–200Vm  1 can exist near the ground, with the positivelycharged ionosphere acting as an anode and theearth as a cathode causing a transfer of negativeions from the earth to the sky and positive ions fromthe ionosphere to the earth along electrostatic linesof force. When poor weather conditions, suchas thunderstorms, arise this situation is reversedand triboelectric inversion occurs, with the airbelow positively charged clouds becoming morenegatively charged than the ground underneath,causing the vertical electric current to flow in theopposite direction—in such situations fields of 3000–10,000Vm  1 can be encountered (Sulman,1980; Sheppard and Eisenbud, 1977; Bach, 1967). Distorted current flow and higher fields than thiscan however be created indoors, particularly whenconditions of low RH or dew-point temperatureexist.  2.5. Standards and guidelines 2.5.1. Standards regarding air ion concentrations The Ministry of Health of the Russian Federa-tion’s ‘Sanitary and Epidemiologial Norms’ guide-lines (SanPiN, 2003) stipulate mandatory maximumand minimum levels of bipolar air ion concentra-tions in the computer workplace. SAI concentra-tions must not be  o 600 negative (NSAI) and 400positive small air ions (PSAI) cm  3 , and levels mustnot exceed 50,000 NSAI or PSAIcm  3 . Theseregulations state that optimum recommended ionconcentrations to reduce fatigue and enhancecapacity for work are 3000–5000 NSAI and1500–3000 PSAIcm  3 . These air ion concentrationsare also required to have a factor of unipolarity  Y  ,with a minimum and maximum ratio of positive tonegative ions being given by 0.4 p Y  p 1.0.Though the recommended optimal and manda-tory maximum small air ion concentrations sug-gested by the Russian SanPiN guidelines are farhigher than often found in nature, such levels canhelp to reduce incidences of excess charge.Though no formal legislation appears to exist inthe western world, in the USA, the Federal AviationAuthority (F.A.A.) acknowledged that both verylow SAI concentrations, and high ion concentra-tions with a factor of unipolarity with a strongimbalance of positive air ions can produce detri-mental effects (Rosenberg, 1972).  2.5.2. Standards regarding AC fields Whilst International Commission on Non-Ionis-ing Radiation Protection (ICNIRP, 1998) guidelinesstipulate that 60Hz AC electric fields encounteredby members of the general public should be p 4200Vm  1 , Russian and Swedish guidelines forcomputer users advocate AC field levels of  p 25 and p 10Vm  1 , respectively, at 0.5m from computersin the ELF 5–2000Hz (Band I) range (SanPiN,2003; TCO, 2003). AC fields may partially influence ion deposition,coagulation rates along with localised contamina-tion levels if they are sufficiently strong.  2.5.3. Standards regarding electrostatic fields The Russian guidelines for computer usersstipulate that the electrostatic potential at 0.5mfrom computers should be p 500V (SanPiN, 2003),whilst the Swedish guidelines specify a maximumsurface potential of  7 500V (TCO, 2003).However, whilst such standards can be of greatuse in reducing incidences of electrostatic discharge,induced charge and surface contamination, they donot take into account the fact that the body appearsto function best when exposed to constant verticalelectrical fields and that exposure to distorted fieldregimes and ‘‘Faraday-cage’’ conditions may actu-ally prove detrimental to health (Jamieson et al.,2006).  2.6. Hypothesis and scientific evidence The presence of inappropriate levels and typesof electric fields in individual microenvironmentsmay greatly reduce localised concentrations of SAI, whilst increasing localised concentrations of  ARTICLE IN PRESS K.S. Jamieson et al. / Atmospheric Environment 41 (2007) 5224–5235 5226  charged ultrafine particles, such as large air ions(LAI).The possible presence of high concentrations of LAI in the room being assessed for the case study isindicated by the fact that the air is highly conductivewhilst having low concentrations of SAI—large airions normally add little to the air’s conductivityapart from when SAI are absent (Wait andParkinson, 1951). Note: though LAI are categorisedas being  p 79nm in size, electrical effects canpredominate as a transportation and depositionmechanism for ultrafine particles and fine particlesup to 1 m m in size. 3. Case study Measurements of SAI concentrations, electro-static potential and AC electric field strengths weretaken in an office environment. It was intended thatthis work would indicate the link between inap-propriate levels and types of electric fields, lowconcentrations of SAI and high concentrations of LAI, whilst also showing how the electromagneticenvironments individuals can be exposed to whenindoors often have little resemblance to thatgenerally experienced in nature. This work was alsoundertaken in conjunction with a critical literaturereview. 3.1. Methodology3.1.1. Room description The office studied was a computer work-suite,with both natural ventilation and air conditioning,which is situated in a reinforced-concrete building inBergen, Norway. Data were collected on separatedays in July 2005 whilst the main workstation wasoccupied. A listing of the materials and finishesfound in this room are given in Table 1, and a plan,section and photograph of it are shown in Fig. 1. 3.1.2. Measurement procedures For the vertical sections created through theroom used for this work, continuous measurementswere taken at 0.1m increments from a height of 2.1m to a height of 0.1m, with further readingsbeing taken 0.05m from the finished floor level ineach instance. These were taken at 0.35m intervalsalong a line that passed diagonally directly throughthe sitting area occupied by the main computeroperative and the 0.25m horizontal grid-work usedfor measuring the horizontal sections. Two hundredand seventy-six individual sampling points wereused for constructing the vertical isopleths of thisroom, and 202 sampling points for the creation of the horizontal isopleths. As the measurements weretaken at grid points, it was possible to missmaximum and minimum readings that appearedoff-grid. 3.1.2.1. Ion measurements.  The concentrations of SAI present were measured using an air ion counterby Alpha Lab Inc., which had accuracy guaranteedto  7 25% for ions in this range (mobility 4 0.8cm 2 V  1 s  1 ) though the unit itself is cali-brated to an accuracy of   7 5%. The lowestcharacterisable mobility for the unit is0.5cm 2 V  1 s  1 . It had been intended to extend thiswork to include the measurement of large air ions,but this part of the project was postponed due tolack of equipment/funding. ARTICLE IN PRESS Table 1Materials and finishes specificationsItems CommentsRoom dimensions 2.4m  4.4m  2.8mCeiling Paint finish on plasterboardCabinets 2 No. metal constructionChairs (synthetic covering) 2 No.Cathode ray tube (CRT)monitors with hard drives5 No. plus grounded laptopTimber door 1 No. with paint finishFlooring VinylPlastic letter trays 3 No.Main lighting—fluorescentand incandescentNot used during measurementsperiod as low light levelspreferred by normal occupantsAnglepoise desk-light 1 No. used duringmeasurementsOscillating desk fan 1 No. used duringmeasurementsPrinter 1 No.Walls Paint finish on plastered blockWindows Double-glazed external windowwith blinds and curtains.Observation window fromindoor passagewayHeating/ventilation Natural, fan and air-conditioningWork-stations 2 No. with wood veneer finishand metal frameworkTelephone 1 No. DECT digital phone unitMiscellaneous (includingpersonal items andparaphernalia)Plastic-finish Lever Arch files,plastic filing-pockets andcardboard magazine files onshelving K.S. Jamieson et al. / Atmospheric Environment 41 (2007) 5224–5235  5227
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