Buildini; S.mJ . Eng. Res. T~chnol. 10(1 ) 1-11 (1989) Primed in Grc:i.c Britain
Review paper
Summary This paper reviews published information on 'sick building syndrome', i:he cause of a repucedly high incidence of s i~km:ss among occupancs of sealed, mechanically ventila[ed buildings. le discusses sympcoms, common fe:Hures of 'sick buildings' and posrulaces possible causes. On [he basis of reported cases, mere appears to be no single cause buc a series of concriburing fac:ors.
Sick building syndrome
J M Sykes BSc CEng MCIBSE MIGasE MinstE ,\HOH Hea!ili & Safery Executive, Magdalen House, Scanley Precinct, Boo cle L20 3QZ, .\1. erseyside, UK
Received H April 1988, in final form 7 Occober 1988
1 Introduction building syndrome' based on their particular area of interest:",s . Such an approach may have advantages if the Concern about the reportedly high incidence of sickness different symptoms suffered by the occupants of sick build among people who work in sealed buildings, especially ings can be shown to have many different causes. offices, has attracted considerable attention. In the UK this is a comparatively recent problem, most reports having been 3 Reported cases published since 1980, but in other countries, especially in North America and Scandinavia, the problem was first Reports of 'sick building syndrome' fall into two caregories reported some 30 years ago, in both the workplace and the investigation of cases in order to prescribe a remedy, and home. surveys of office and other buildings to assess the extent of Various terms have been used to describe the phenomenon the proble:n and its likely causes. ,\-lany in the latter category 'building sickness', 'sick building syndrome', 'sick office usefully include 'sick' and 'control' buildings to enable syndrome', 'tight building syndrome', 'office eye syndrome' comparison. Table 1 lists the reports considered and possible and others. None adequately describes the condition but the causes. term 'sick building syndrome' has been accorded recognition One notable shortcoming is that few investigations are com by the World Health Organisation (WHOPl and is the most pletely multidisciplinary in approach so that papers often widely used. separately consider the medical aspects, measurement of 'Sick building syndrome' continues to attract both specu airborne contaminants or an assessment of the physical lation and controversy and, unforrunately, many of the environment and the ventilation or air conditioning system. plethora of papers on the subject are devoted more to specu Few simultaneously study all three aspects of the problem. lation than to fact. Its nature, prevalence, causes and even This means that some investigations have drawn conclusions its existence are open to debate. This paper reviews current which do not appear to be fully supported by the reported published information on the subject. facts, possibly because not all of the information found in the investigation is reported or possibly because the investigators 2 Definition have made assumptions. Whatever the reason, some con jecture appears to be subsequently reported as fact, especially in the press. Unfortunately, few investigations have con 'Sick building syndrome' is, by its nature, ill defined. One clusively proven a cause by the successful selective appli definition used is 'a building in which complaints of ill health cation of remedial measures in a controlled sequence. are more common than might reasonably be expected'r.3l. This has some drawbacks since it does not address the In addi~n ro case investigation and studies, a number of question of whether such complaints are, or are not, justified. papers consider a particular, narrow aspect of 'sick building However, the common feature of sick buildings is that their syndrome' or one postulated cause. Some provide a useful occupants suffer, or appear ro suffer, a measurably higher and detailed insight inro that aspect whilst in others it incidence of illness than expected for no readily identifiable appears that the particular author has used 'sick building reason. Clinically diagnosed. illnesses which can readily be syndrome' as an excuse, rather than a reason, for the work. attributed to a particular cause such as humidifier fever, Legionnaires' disease or to exposure to a toxic agent in 4 Symptoms and prevalence the environment are not usually regarded as 'sick building syndrome'. Most repom of outbreaks detail a common list of symptoms. Various authorities and authors have attempted to divide There are summarised by WH0(1l as: 'sick building syndrome' into different categories. Most eye, nose and throat irritation notably, WHO © 1989 The Chartered Institution of Building Services Engineers · ·~"'\ ~-~--~------.. ------·-··- - -- ·--·--· · . ··- ·-- - --· .. . JM Sykes Table I Investigation and rocarch n:pons on building sickness Ref. Au tho~ Counll)' Compantivc Number of Cawcs (1 = suoog link; b = postulated but unconfirmed: c = dllcounted or disproren) Measured Year srudy affected effect OD Buildinp Peopie NI Humi- lnadequ:ue Tempcnru.rc, Poor Humidity NI P•ycho- Gen=! performance pollution di.6cn vcntibtioo, thermal lighting ions logical dissatis- fresb air comfon etc. O>USC faction etc. Finnepn UK Yes b b b "aJ 1984 Whonoo USA No 11: "aJ 1987 Fcrahrian Canada No 1000 1984 Wilson & UK Yes 46 43j3 Hedge 1987 10 Sterling & Canada No NOQC Sterling J9B 11 Berglund Denmark Yes None "aJ 1983 13 Steilnwl USA None er al 1985 15 Washington USA No 10 A Univcn.icy 1982 35 Brown- USA No Skeen 1984 37 Taylor USA "a/ . 1984 41 Pickering . UK Yes 280 et al 1984 42 Robertson UK Yes b tl al 1985 45 Hawkin• UK No 1982 56 Hawkins & UK No Morris 1984 57 Finnegan UK No er al 1987 58 Roberr:son UK Yes 2/1 /9 b/c b/c & Burge 1986 73 Waller UK 1984 84 Hanssen & Norway No Rodahl 1984 headaches, high frequency of airway infections and building syndrome' and performance/neurological tests. cough Sterling and St:erling(lo) used 'tremor' tests and 'T crossing' tests but failed to show a difference between the test and hoarseness, wheezing, itching and unspecified hyper control groups .. Bergund 2 Building Services Engineering Research and Technology Sick building syndrome 5 Common features of sick buildings Many of these are interrelated subjects and 'sick building syndrome' may well result from the simultaneous effect of a The WHOOl identiiies a number of features common to sick number of challenges. Except in a few cases where sympcoms buildings. Summarised, these are: follow a specific change in the working environment, e.g. 151 the installation of a new carpd , isolation of the cause is (a) They often have 'forced' ventilation (WHO does not notoriously difficult. Comparative studies between 'sick' and make specific reference rn air conditioning although air 'control' buildings will highlight those features which are conditioning will fall into this general category). common to 'sick buildings' and do not occur in others, but (b) They are often of lightweight construction. identification of the cause may well become a procedure of 'trial and error', and since many supposed causes would (c) Indoor surfaces are often covered in textiles (carpets, involve major and very expensive remedies, such a course is furnishing fabrics etc). rarely tried and the cause remains a matter of conjecture. (d') They are energy efficiem, kept relatively warm and The possible causes, as identified from published papers, have a homogeneous thermal environmem. are discussed in the following paragraphs. (e) They are airtight, i.e. windows etc. cannot be opened. Subsequent comparative studies in the UK have tended 7 Airborne pollutants 38 39 41 42 to confirm these common features( • • • l although sick building syndrome does not occur in all buildings with these The potential range of pollutants in the office and similar 9 features. Wilson and Hedge' 1, in their survey of 46 buildings environments is enormous. However, levels actually occur in the lJK, considered the building environment and air ring have generally been found to be minute, sometimes conditioning system design in relation to the prevalence of requiring tec!utlques more sensitive than normal occu 161 symptoms and found significant differences even among pational hygiene practice for their measuremen • Hicks~Sll buildings conforming to the WHO list offeatures. In general, reports typical levels of air pollution measui:ed in tight cheaply constructed buildings with cheap air conditioning building' investigations (Table 2). Various sources of air systems, especially public secror buildings constructed in borne pollution can be identiiied; the main ones are as the 1970s, showed more problems than well constructed follows. buildings with more expensive air conditioning systems dat ing from the 1980s. The type of glazing also appeared to be 7.1 Building occupants significant-all of the least healthy buildings, but none of Pollutants released by occupants of the building include the healthier _buildings, had tinted glazing. C02, water vapour, micro-organisms and organic matter. Carbon dioxide levels due to respiration alone can rise to several thousand parts per million in well sealed buildings. 6 Possible causes Although there are no reports of levels above the occu pational exposure limit (5000 ppm) levels of up to 1800 ppm Many causes have been suggested for sick building have been reported07J and since, in some cases, building syndrome, including: ventilation systems are controlled by C0 2 monitoring with the monitors set to operate at levels of up to 2500 ppm, it is (a) Airborne pollutants: possible that C02 levels will, in some circumstances, (i) Chemical pollutants from the building occupants, approach the exposure limit (this will be discussed later with fabric and furnishings, office machinery and from other aspects of ventilation). It is unlikely that C02 at these outside. levels is itself the cause of illness but it mav be an indicator ... for the presence of other airborne pollut~rs. The Ontario 81 (ii) Dusts and fibres. Ministry of Labour l, for example, has adopted an indoor (iii) Microbiological contaminants from carpets, fur nishings, building occupants or from the ven tilation or air conditioning system. Table 2 Air contaminants de[ected in tight build- These may have a directly toxic, pathogenic or irritwt ing invesri!ncions', 711 effect on occupants or they may have an allergenic effect (i.e. once occupants are sensitised, subsequent Substance Concenrrai:ion exposures, even to very low concentrations, may cause Tocal dust 20--IQ ,ug m · 1 illness). Respi.rabie dust 10-25 ,ug m-1 (b) Odours. Coal tar pitch rnlatiles 0.05~.oz ,ug m- 3 (c) Lack of negatively charged small air ions. Formaldehyde 5-40 ppb Toluene 10-30 ppb (d') Inadequate ventilation/ fresh air supply. o,m,p-Xykne 10-20 ppb Ethylbenzene S-15 ppb (e) Low relative humidity. Hexane 10-25 ppb ({) Poor working environment/discomfort due to: I, 1,1-Trich.Joroet:hane 50-150 ppb I, 1,2,2-Perch.Joroet:hylene 40-80 ppb (i) High temperatures. C,·C Alkanes 10-50 ppb Ozone 5-10 ppb (ii) Inadequate air movemi:nt/sruffiness. NO, 200 ppb (iii) Poor lighting. Carbon monoxide 2-5 ppm Carbon dioxide 0.05-0.09% (g) General disatisfaction or psychosomatic curves. Vol. 10 No. I (1989) 3 ---·-- ·---· . ·- · ·---... ~--.. .. ---·--""'· ~· -...... · ";,. • .-·- :.;.· · ..;· ··i.i.\&;s.;·;;.._. JM Sykes Table 3 Gases found in cigarette smokeil 8l 'sick building syndrome' (or even whether it contributes to airborne pollutant levels). Some researchers have suggested Species Cone. Threshold Ratio Toxic that smoking does not affect either contaminant levels or (ppm) limit above action 'sick building syndrome'; Sterling et az 7.2 Building fabric and furnishings C0 2 standard of 600 ppm on this basis. However, such a Many sources of pollution have been attributed to releases standard will only be valid if there are no other sources of (or 'off-gassing') from the fabric and furnishings of the C02• building and in some cases a strong link has been shown with cases of illness among occupants. Pollutants include: Smoking creates a much more considerable source of air borne contamination. Table 3 lists those gases ro be found (a) Formaldehyde, especially from urea formaldehyde in cigarette smoke(IUoi. There are many reports analysing insulation and certain rypes of board. Formaldehyde is 20 pollutants from tobacco smoke; a review by Brundrett< l an irriram and may therefore, cause sotne symptoms listed carbon monoxide, carbon dioxide, nicotine, furfal, similar co those of 'sick building syndrome'. Its release aldehydes, ammonia, phenols, hydrogen cyanide, pyridines, from urea .formaldehyde insulation into domestic oxides of nitrogen, acrolein and particulates, many of which premises has caused concern in some countries where have toxic or irritant properties. measurement by various researchers has revealed substantial levels, with peak values up to 2.8 mg Brundrett also lists physical symptoms caused to smokers 3 m - O,l5-ZS) and indoor air standards have been in and passive smokers (Table 4) which bear similarities to troduced, for example, in Germany (0.12 mg m- 3), some symptoms of 'sick building syndrome'. The Netherlands (0.12 mg m- 3) and Sweden 3 There is debate over whether smoking does contribute to (0.10 mg m- ), although their precise status is unclear. Table 4 Physical irritation caused by smokers'20J Bogen Speer Cameron Which consumer magazine I929 1968 19i2 February I 975 US; sample size not given US; 250 non-allergic US; li!O children British; 1155 adults Smokers Non-smokers 7-15 years old Non-smokers lll-effects % population JU-effects % population Ill-effects % population Irritation rype % population Non- Allergic allergic Shortness of breath 35% Eye irritation 69% . 73% Eye irritation 47% Stinging eyes 26% Biting and irritation 30% Nose symptoms 29% 67% Cough 37% Coughing I6% Coughing 30% Headache 32% 46% Headache 12% Difficult breathing 8% Burning 15% Cough 25% 46% Nasal irritation 11% Nasal irritation 6~ · o Nausea 10% Wheezing 4% 22% Throat, nausea 5-10% Sore throat 6°/o Palpitation of heart 5% Sore throat 6% 23% Nausea 5°10 Hoarseness 5% Nausea 6% 15% Headache 3% Salivation 5% Hoarseness 4% 16% Dizziness 1% Dizziness 6% 5% 4 I ~· Sick building syndrome Other building materials have also been shown ro 'sick building syndrome' and such buildings are unlikely to release formaldehyde; for example, particle board has have unflued heaters. 3 been shown to cause levels of 1.0 ppm (1.25 mg m- ) wht::n newly installed, dropping with time and ven 7.5 Ventilation and air conditioning systems 25 29 tilation rare: • \. This has prompted speculation that Ventilation and air conditioning systems can transmit air formaldehyde is a cause of 'sick building 127 borne disease including Legionnaires' disease, humidifier syndrome'ns,m. In ont:: investigation, Dement " found fever, and various infections:.\!)). Some, particularly Legion complaints of upper respirawry tract and eye irritation naires' disease, originate outside the system. Others, of in a temporary building with particle board panelling which humidifier fever is the prime example, are caused by etc. where formaldehyde levels of up to 0.23 ppm 3 organic and/or microbial growth in typical items of plant in (0.29 mg m - ) were measured. On 'fumigation' wir...!.i the air conditioning system. Most of these illnesses have ammonia and increased ventilation, formaldehyde readily identifiable causes and their symptoms are different levels dropped to below 0.1 ppm and complaints from those of 'sick building syndrome'. subsided. Some reports from the l:SA and other countries link formaldehvde wirh 'sick building However, there may sometimes be a link between cases of syndrome' bur other su.rveys, for example, by 'sick building syndrome' and humidifier fever. Papers by NIOSH 151 have discounted it. Smdies in the l'K have Finnegan and others:3 . .iuz: report two cases of humidifer also discounted it. fever among the population of a 'sick building', and a higher incidence of respiratory symptoms among people in a (b) Organics and solvent vapours. These can be produced humidifier building than a non-humidified building. They from various sources including adhesives used in fur did not find a higher incidence of other symptoms. Wilson nirure and for sticking carpers, floor tiles etc. One and Hedge:9l also report a higher incidence of symproms outbreak of illness in the C'SN15l was attributed either among occupants of buildings with 'non-sterile' forms of to the carpet or the adhesive used bur most inves humidification than those with steam humidification. tigations have failed to show the presence of organic vapours in sufficient quantity to cause illness. Several Even where air conditioning systems do not contain humidi papers have attributed symptoms to a 'photochemical fiers, items of plant can act as breeding sites for organic smog' caused by the action of ultraviolet light on organic growth. This is true of items such as cooling coils \vhere contaminants but these are based on a single srudy of condensed water can collect, and these have been shown to 2 two buildings001 and the theory does not appear to have release microoganisms into the airstream; ). No link has been been conclusively proven (see section 14). shown between causes of 'sick building syndrome' and other 9 items of air conditioning planr, although Wilson and Hedge: l (c) Dust and fibres. Some authors have attributed 'sick report different symptom rates with different types of air buildin"g syndrome' to dust and fibres from carpets, conditioning system which are not explained by differences furnishings and insulating materialsC34l. General papers in temperarure ere., so a link cannot be entirely discounted. also consider organic dusts from carpets suggesting that they can harbour organisms such as house mites which Some authors have attempted to link 'sick building cause asthmatic anacks, or that dampness can lead to syndrome' with insulating materials associated with building microbial contamination which in rum causes illness services and heating and ventilating systems, particularly 31 among building occupants;30-Hl. Many papers are with asbestosC \ but this is purely speculation and none speculative and some give more opinion than fact. have justified their views. However, a few cases of 'temporarily sick buildings' 15 35 It may be possible for ventilation or air conditioning systems may have been caused by airborne dust' • l. to transport contaminants or pathogens from one area to another within a building. Aerobiologists in the health ser 7.3 Office machinery vice have shown that pathogens can be carried in hospital ventilation systemsC4-0l, thus spreading infection. Despite Although photocopiers have been suggested as a cause of some speculation, this has not been shown to be a cause of building sickness, and pollutants such as ozone can collect 36 'sick building syndrome'. There is also little evidence to in very poorly ventilated photocopying rooms< ), only one suggest that outside pollution drawn in through the ven investigation links a photocopier ('wet type') with 37 tilation system is a cause of 'sick building syndrome'. One symproms: l. Another investigation, involving a large num 15 case rep9fted by NIOSH ) involves complaints of 'noxious' ber of buildings, discounts ozone from photocopiers. HSE odours possibly drawn in from a parking area but there is investigations have shown pollution levels in photocopier no record of symptoms. rooms to be generally low, so they appear unlikely to be a major cause of symptoms other, perhaps, than among some staff working in poorly ventilated photocopier rooms. 8 Effect of airborne contaminants 7.4 Heaters If airborne contaminants are responsible for the symptoms of 'sick building syndrome', whether acting alone or syn Direct fired hearers can release toxic gases, particularly ergistically as components of a complex 'cocktail', this may carbon monoxide and oxides of nitrogen, into occupied 3 39 be due to several mechanisms, including the following. areas. Various studies of airborne pollution in homes; s. l have suggested that nitrogen dioxide from combustion prod 8.1 Toxicity ucts may cause illness among children and some outbreaks of illness among building occupants investigated by HSE All investigations where levels of contamination are reported have been attributed to products of combustion from faulty indicate that these are low, and often very low indeed, in hearing equipment. However, rhere is no evidence to link relation to the appropriate occupational exposure limits. heating or combustion equipment with published cases of However, whilst there is as yet no proven link between Vol. 10 No. 1 (1989) 5 ;.- ~ - ~----· . .. ··-· .. .. ·-----'------... JM Sykes 'sick building syndrome' and the toxic effects of airborne 10 Air ions poUurants, the coxicology on which exposure limits are based is not necessarily relevant to the low-level, chronic exposure Ions in the atmosphere are molecules of its constituent gases which might occur in sick builclings, so the toxic effect of which have either a positive or negative charge. They occur airborne pollutants cannot be discounted. naturally by various means, or may be created artificially using an air ioniser. Small numbers of charged air ions exist in outside air, typically one in 10 16 molecules, but these 8.2 Irritation become depleted indoors to perhaps one tenth of the outdoor Several reports attribute 'sick building syndrome', or some levell451. Several reasons are suggested for this depletion of its symptoms, to the irritant effect of airborne loss of ions in metal ventilation ducts, water vapour, dust contamination. Some of the contaminants are known to and smoke acting as condensation nuclei, the depleting have irritant properties formaldehyde for example. Frank ( ~ > effects of VDUs. specifically attributes eye symptoms to drying of the eyes Air ions are claimed to have a number of effects on human possibly caused by the altered stabiliry and composition of physiology and health. For example, medical research papers the eye film due to irritants such as formaldehyde, although from Israel claim that in certain weather conditions the he does not report levels of onraminant in air. Molhaveil 9l increased positive ion concentration in air causes increases suggests that levels of volatile organic compou.tci berween neuroticism (Serotin Irritation Syndrome) which can be 0.16 and 2.0 mg m-3 are responsible for mucous irritation overcome in some patients either by the use of tranquillisers and that there should be further investigations to establish 46 17 or by the generation of negatively charged small air ions( ,' l. a dose-response relationship for organic compounds in sick Other researchers suggest that negative air ions act as cata buildings. However, these hypotheses do not appear to have lysts to remove trace gases, kill micro-organisms, affect the been established experimentally. dispersal of aerosols containing microorganisms, and claim that they relieve anxiety in rats and mice and reduce the 8.3 lnfeciion death rates in rats and mice injected with influenza virusC 48 l. Although micro-organisms can be released from air con Negative ions have also been shown to afk:t the mammalian respiratory tract although the researchers doubted whether ditioning systems etc., and ventilation systems in hospitals 49 52 this would also apply to manC • l. Some papers have shown have been shown to transmit pathogens, there is little reason that positive ions increase air uptake in exercise:so) and there to believe that 'sick building syndrome' is due to this mode is some evidence, albeit conflicting, that air ions may be of cross-infection. Outbreaks of other illness may occur 5 among occupants, for example, influenza or even Legion beneficial to asthmatid I). naires' disease, but these are not to be confused with 'sick Considered selectively, some published information on this building syndrome'. The continuing nature of symptoms of subject can be interpreted to show that negative ions have 'sick building syndrome and the fact that they occur only great benefits. Some suppliers of negative ion generators when at work, suggests that they are not due to infection. have shown great selectivity in their interpretation, claiming benefits for their products which include relief from bron 8.4 Allergy chitis, hay fever:, catarrh, asthma, rheumatism, headaches, colds, eczema, high blood pressure, palpitations, con The nature of the symptoms suggests that allergenic reaction junctivitis, and laryngitis, plus resistance to influenza, to airborne pollutants whether chemical or microbiological increased ability to concentrate and reduced fatigue'. 53 ) and, agents is possible. The allergenic effect of many agents is of course, a reduction in the incidence of 'sick building well recorded and sensitised people can be affected by even syndrome''54l. A number of such claims prompted action by minute quantities of some agenrs, which might explain why authorities, particularly the US Food and Drug Ad.minis symptoms occur even where air sampling fails to reveal cration!53.m who seized nine brands of generator for mis significant levels of contamination. Unfortunately unless leading claims between 1959 and 1967, and the UK the allergenic ageor can be traced and affected pe~sons tested Advertising Standards Authority. for their reaction ro it, proof is particularly difficult and the differences between 'sick' air conditioned buildings and their The claim in the UK that negative ion generators have a narurally ventilated controls cannot readily be explained by beneficial effect on 'sick building syndrome' is largely based 45 an allergy unless c.he agent originates in the air conditioning on work by Hawkins at Surrey Universiryr l. However, system itself. A few investigators have indicated such a link in subsequent work, Hawkins failed to repeat his earlier 49 in particular cases but it has a0t been universally established. findings( l. Investigation by other researchers showed either that negative ions had no effect in sick buildings~ 56 l or that thev had no measurable effect on human mood and perform~ncer 54 ~. One investigation report'. 57 •58 ) gave higher negative ion concentration in the 'sick' building than in the 9 Odours control. A few papers consider odours in relative to 'sick building There may be reasons, besides the obvious one, why tests syndrome'. Bergund et al 5 ~ discuss sensory perception on negative ion generators have failed to show benefit. 4 (including smell) and suggest that 'sick building syndrome' Krueger and Reedl B) suggested errors in observation caused is caused by sensations in response to imperceptibly small by pollutants (including 0 2 and N02 from the generator) stimuli of all sons; some case investigations mention odours and failure to earth the subject. Even if they were correct, but there is little suggestion that they are, or might be, their suggestions do not augur well for the practical benefirs the cause of symptoms. Two papers(43 ,-1-1i link odours with of negative ion generarors. The research shows that negative outbreaks of psychogenic illness (see section 16) but there is and positive ions may well have some effect on comfort no reason to relate such outbreaks to 'sick building and well being-either detrimental or beneficial-and it is syndrome'. difficult to prove beyond all doubt that negative ion gen- 6 Building Services Engineering Research and Technology Sick building syndrome erators have no benefit whatsoever, but the balance of evi building occupants because of inadequacies in the ventilation dence suggests that they are of little practical benefit for etc. system are legion. Youle(60l and Waller73 l detail a num dealing with 'sick building syndrome'. ber of such problem buildings where an excessive number of complaints were received because of inadequacies in the ventilation or air conditioning systems due to poor design, 11 Inadequate ventilation installation and maintenance. Since the reports give no details of medical symptoms, these cases cannot be con Of all the fearures corrunon to 'sick buildings', the system sidered as 'sick building syndrome', but they do indicate a of ventilation is often reg:i.rded as most significant; sick possible contributory factor. building syndrome gener;ily affects buildings which are The practice, rarer in the UK than USA, of using C0 sealed and have mechanical ventilation or air conditioning. 2 monitors to control mechanical ventilation rates mav also This le:i.ds to a presumption that lack of fresh air is a major cause problems. Jansen and Hill< 61 l describe such a system cause of 'sick building syndrome'. set to operate at 2500 ppm COz, i.e. the system would not Mechanical ventilation of buildings differs from natural ven draw in fresh air until the C02 level reached 2500 ppm. tilation in a number of ways, most significantly: However, since C02 levels did not rise above 1800 ppm the While mechanical ventilation and air conditioning can svstem did not draw in fresh air. The ASHRAE standard of exercise more precise overall environmental control, i.5 litres second- t person-t was based on an indoor CO: only rarely do they allow personal choice or local standard of 2500 ppm. control. The evidence suggests that inadequate fresh air is a con The make-up air supply into mechanical ventilation tributory factor rather than a sole cause of 'sick building systems can often be varied during operation in order syndrome'. Many authors have advocated increased ven to increase the proportion of air that is recirculated and tilation, either alone or in conjunction with other reduce the quantity of fresh air drawn in from outside. precautions; few have studied the direct effect of increased ventilation rate in sick buildings. However, several 'tem 1\1.echanical ventilation and air conditioning systems porarily sick buildings' have been 'cured' by increased ven have components which are susceptible to failure and tilation, among other measures( 151 . Two papers dealing with to poor design or installation. buildings which appeared to be 'permanently sick' were able to show a reduction in symptoms with increased Recirculating ventilation and air conditioning systems 3 10 can harbour organic growth and may distribute con ventilationl i, ). In one, the fresh air rate was increased tamina!J.ts from one area throughout the building (this from 3 to 10 cfm 1 s - I per person; the fresh air rates were aspect has already been considered). not given in the other. Fresh air is required for various reasons, the main ones being It would therefore appear that while some cases of 'sick to supply air for respiration and to dilute COz, odours, building syndrome' are related to an inadequate fresh air cigarette smoke and other contaminants. Ventilation, supply, this is not universally true. although not necessarily by fresh air, may also be required to maintain personal comfort, i.e. for the control of air temperature. 12 Relative humidity Several standards have been set for ventilation and fresh air Various researchers have shown that low relative humidity supply rates to offices, usually based on the air required can lead to an increase in the incidence of respiratory to dilute cigarette smoke or body odours. The Chartered infection~ 62 • 63 • 64l. The GIESE Guide< 59l recommends that Institution of Building Services Engineers<59l and BS5i2d93l relative humidity be maintained between 40 and 70%. set a standard which ranges from 5 litres per second per person in general offices up to 25 litres per second (1 s-1) per The reasons for increased incidence of infection are a subject person for personal offices or boardrooms where smoking for debate. Four possible reasons are given: is heavy. In the USA, the American Society of He:iting, 24 (a) Humidity may affect the survival of bacteria and Refrigeration and Air Conditioning Engineers (ASHRAE)C J 66 viruses<63 ,65 · l so airborne micro-organisms are less standard is most widely accepted and has been periodically Iik#iy to survive in relative humidities of the order of revised downwards. In the early 1900s it is reputed to have 50%. However, it is also true that humidities over 70% been 30 cfm (151 s-1) per person, which dropped to 10 cfm 1 can cause dampness which may encourage the growth (5 1s- ) in the 1930s as a result of work by Yaglou on body 64 of micro-organisms< ' and humidifiers can, themselves, odour, then to 2.51 s-1 per person in 1981 (7.5 l s-1 per release airborne micro-organisms. person for offices where smoking was permitted). This last rate was based on achieving an indoor C02 level of2500 ppm; (b) Higher humidities encourage the agglomeration of air it also requires that 80% of the occupants should be borne particles and these larger particles are believed 'satisfied'. Fortunately this standard is now being changed; to be less likely to cause infection<63l. the latest ASHR..-\E standard will require l s- 1per person 7. 5 (c) Dry air may produce microfissures in the upper res for all offices, whether or not smoking is permitted. piratory tract which act as landing sites for infection< 67 ~. The impetus to seal buildings and increase the control over (cf; Increased mucous flow flavours rejection of micro the environment is usually motivated either by necessity organisms. There is, however, some debate about ('deep' buildings with open plan offices are difficult to ven whether mucous flow increases at higher humidities, tilate naturally) or by a desire to save energy (and money). with researchers finding both for and against the The practice of tight control over the indoor environment theoryC6S,69l. poses problems if the ventilation of air conditioning system is in any way imperfect. Tales of dissatisfaction amongst It is debatable whether much of this work is relevant to 'sick Vol. 10 No. 1 (1989) 7 ~ - 1 JM Sykes building syndrome' since the balance of evidence suggests A sensation of 'stuffiness' may also play a part. Stuffiness that the syndrome is not caused by infection. generally indicates dissatisfaction with the environmem. BedfordC7 ?l amibutes stuffiness to lack of stimulation, sug Few investigations have included derai.Jed consideration of gesting that a change of air velocity will stimulate the nerve humidity and comparative srudies by Robertson et a/c4z> tactile endings in the skin, which firs in pan with the theory showed similar relative humidities in 'sick' and control build by Berglund et alm thar imperceptibily small stimuli may be ings, suggesting that low relative humidiry was not the cause. to blame. Two papers report investigations where it was However, low humiditv is known rn cause some of the possible ro reduce complainrs of sruffiness by the use of symptoms noted in sick buildings. Erythema (skin rash) may individual fans ro increase the air velocity from 0.05 to be caused by low humidity; Griffiths and Wilkinson<76>quote 0.6 m s- 1<74> and by reducing~ temperature by 2K C75}(from an incidence of itchy erythema of the face and neck amongst 23 ro 21 °C). factory workers which was cured by raising the ambient humidity from 30-35% ro -+5-50%. Mclncyre<7 °1 was able to Clearly discomfort and dissatisfaction with the thermal demonstrate some increase in eye irritation at very low environment will lead to complaints and many articles have humidities (20%), presumably due to drying effect. Thus, equated 'sick building syndrome with those complaints. A while low humidity is unlikely to be a major ca~se , it may building cannot be classed as 'sick' just because its occupants sometimes be responsible for symprnms. are uncomfortable, but some inv.estigations have shown that symproms are often more prevalent where occupants find their environmenc uncomfortable. However others have 13 Working environment, comfort and , sensory per failed co link symptoms with comforc and in some cases, ception 'sick building syndrome' has remained even when problems of discomfort have been dealt with 8 Sick building syndrome Some outbreaks of illness amongst workers have been attri (b) Temperature and air movement; there is some evidence buted to psychological causes. Guidottf971 describes an out to suggest that high, uniform temperatures and lack of break of illness in a telephone exchange when 81 members air movement result in more symptoms. of staff were taken ill. Air sampling results were negative and the outbreak was eventually attributed to an employee (c) Humidity; low relative humidity may sometimes cause with a 'military history of involvement in psychological erythema and eye irritation. operations'. Smith et <.J.l 62 ~ describe three outbreaks of mass (cf) Lighting standards; symptoms have been shown to psychogenic illness in industrial plants with many symptoms be more prevalent in buildings with certain types of similar to those of'sick building syndrome'. These outbreaks lighting, especially where the lighting and decor are were found to affect workers in a predominantly female dull and uniform and there is little daylight. workforce who were under some physical and psychological (e) Airborne pollution; although pollutant levels have been job stress, and were triggered by a physical stimulus of some found to be very low, pollution may have been respon sort, most commonly a strange odour (Guidotti also mentions sible in some cases. The mechanism is unclear; pre a strange odour in his paper). sumably symptoms are due to irritation or sensitisation Clearly, there are some similarities between symptoms of but this is nor proven. 'sick building syndrome' and those of psychological origin. (j) Airborne organic matter from the air conditioning However, there is little evidence to link sick building syn system; matter of organic origin from the air con drome with outbreaks of psychogenic illness of the type ditioning system, especially from humidifiers, may be reported by Guidotti and Smith Pickering and Finne et al. responsible for some chest symptoms. ganCm suggest that symptoms are only likely to be of psy chological origin in a small number of cases. In further (g) Low morale and general dissatisfaction; although 'sick studies, Robertson ec al found none of the symptoms of mass building syndrome' is unlikely to be a psychogenic hysteria amongst workers examined and therefore conclude illness, there is strong evidence to suggest rhat it is that the symptoms are physical rather than psychological. partially caused or exacerbated by gene:-al dissat isfaction with work and/or the workplace environment. While mass hysteria is discounted, there is a suggestion by some investigators that dissatisfaction with the working It therefore seems that this is a complex phenomenon with environment, especially with lack of control, and with other a number of potential causes, possibly exacerbated by the working conditions may play some part in 'sick building victim's reaction and attitude towards the workplace syndrome'. Waller;481 in a case study of a large air conditioned environment. On the basis of current knowledge it appears insurance office attributes complaints to frustration at lack unlikely that building related sickness will be completely of environmental control, poor management, discomfort and eradicated since symptoms occur, albeit at a very much lower dislike of O!)en plan offices. However, the paper does not rate, in control as well as in sick buildings. mention medical symptoms. WHQCll also discusses com The potential impact of 'sick building syndrome' on the plaints and a 'negative attitude' towards air conditioning, ventilation and air conditioning industry cannot be ignored. again without mention of symptoms. Wilson and HatchC9l Its incidence is far higher among air conditioned buildings consider the link between symptoms and employees' work than those which are naturally ventilated and, in the absence ing environment, their perceived ability to control the of any readily identifiable cause, this may lead to claims that environment and their job satisfaction. They found more air conditioning is itself to blame. Even if such claims cannot symptoms in buildings where occupants had little perceived be substantiated, once made they are difficult to disprove. control over the environment (temperature, ventilation, lighting, noise etc), and the highest rates were in public It is therefore particularly important that the industrf pays sector 'clerical factory' environments. adequate attention to the design, installation and com missioning of air conditioning systems, and that the customer maintains and uses his system properly. Cases such as those 17 Conclusion described by Youle:601 are not uncommon and while the link between such c1ses and sick building syndrome is not From the many cases reported there can be little doubt that proven, they make it difficult for the industry to proclaim the occupants of certain buildings suffer from a higher its innocence. incidence of illness whilst at work than would normally be expected. Although symptoms are generally mild, and there , is little evidence in most cases to suggest that they result in References higher rates of absenteeism, they do appear to cause distress to a large number of people employed in those buildings. Indoor air pollucancs: exposure and healch effeccs Report on a World Despite the great number of papers on 'sick building Health Organisation meeting, Norlingen, ?r-11 June 1982 ISBN 92 890 12447 (1982) syndrome', no single cause has been identified. Table 1 2 H ealrh aspects re/aud to indoor air quality Report on a World Health gives information on the results of many of the published Orglnisation meeting, Bilchoven, 3-6 .\pril 1979 ISBN 92 9020 160 6 investigations into 'sick building syndrome'; few common (1979) threads appear amongst their findings. While the evidence 3 Finneg:in ~l S, Pickering C .\ C and Burge P S The Sick Building is largely circumstantial, it is useful to summarise rhe factors Syndrome: prevalence studi~s Brit . •'.ted. ]. 289 1573-1575 (Dec. which may contribute towards symptoms associated with 1984) building sickness. These are: 4 F rlnk C Eye symptoms and signs in buildings with indoor climate problems ('Office eye syndrome') Acea Opchalmologica 64 306-311 (a) Ventilation rates; in a number of cases symptoms have (1986) been reduced by increasing the fresh air inpur, although Bc:rglund B, Berglund U and Lindvale T ec ul Characcmsation of there is insufficient evidence ro stipulate a minimum, Indoor .-!ir Quality Vol. 10 No. 1 (1989) 9 ~ .. .__. ___ _ . ·-----· ~ ...... " ·· '· ----- ·--· &••· -·--· ··· - - ·· - - - - JM Sykes 6 Whorton M D el al Investigation and work up oi Tight Building 33 Gravesen S ec al Demonstration of micro organisms and dust in Syndrome]. Occ. Medicine 29 142-147 (Feb. 1987) schools and offices. An observational study of non-industrial buildings 7 Ferahrian R H Indoor Air Pollution-Some Canadian Experiences Allergy 41 520-525 ISSN Dl05-4538 (Sept 1986) ind.oar Air Vol l 207-212 (Swedish Council for Building Research) 34 Reisenberg D E and Arehard-Treichel J Sick Building Syndrome (1984) Plagues Workers, Dwellers]. Am. Medical Assoc. 255 3063 (13 June 8 Building Relaced illnesses (London: Crown Eagle Communications) 1986) (l 987) 35 Brown Skeers V M The Puzzling Case of rhe S.O.B. (State Office 9 Wilson S and Hedge H The Offic• Environment Sur-Jey: A study of Building) Occ. Health Nursing (May 1984) pp 251-254 Building Sickness (London: Building Studies) (May 1987) 36 Rajhans GS Indoor Air Quality and C02 Levels Occupacional Health 10 Sterling E and Sterling T The Impac: of Different Ventilation Levels in Ontario 4(4) 160-167 (Oct 1983) and Fluorescent Lighting on Building Illness: An Experimental Study 37 Taylor P R ec al Illness in an office building with limited fresh air Ca111ldian]. Public Health 74 385-392 (1983) access J. Environ. Health 47(1) 24-27 (1984) 11 Bergund B el al Do sick buildings affect Human Performance? How 38 Mant D C and Muir Gray J 'A Building Regulation and Health shouid one assess chem? (Stockholm: University Psycilology Dept) (Garston: Building Research Establishment) (1986) (1983) 39 Melia R J W et al The relationship between respiratory illness in 12 Colligan M J The psychologicil effect of indoor air pollution Bull. primary school children and the use of gas for cooking inc. J . Epid New York Acad. Medicine 1014-1026 (1981) mniology 8 333-338 (1979\ 13 Stellman M J ec al Air Quality and Ergonomics in rhe Office: Survey 40 Blowens R, Lidwel! 0 Mand Williams R G 0 Infection in operating Resulrs and Merholologic Issues .4m. ind. Hyg. Assoc. ! 46!5) 286- theatres in relation to air conditioning equipment]. Insc. Heating Vent. 293 (l 985) Eng. 30 244-245 (1962) 14 Evans G W and Jacobs S Air pollution and human behaviour J. 41 Pickering A C el al Sick Building Syndrome Ind.oar Air Vol. 3 Social issues 37 95-125 (1981) (Swedish Council for Buiiding Research) (1984) 15 Indoor air problems-the office environment-A National Epidemic 42 Robertson A S et al Comparison of health probiems related to work Proc. Univ. Washingcon Conj., 7-9 Dec. 1982 and environmental measurements in rwo office buildings with different 16 Pr~c. America! inJ.usrrial Hygiene Con[. Monireal, Quebec, Canada, 31 ventilation systems Brit . .\!ed. J. 291 373-376 (10 Aug 1985) May-5 June, 1987 43 Guidoni T L ec al Epidemiologicil features that may distinguish 17 Janssen J E and Hill T J Ventilation for Control of Indoor Air between building associated illness outbreaks due to chemical exposure Quality: A Case Study Environment inr.ernational 8 487~96 (1982) or psychogenic origin]. Occ. Medicine 29 (2) 148-150 (Feb 1987) 18 Hobbs M E, Osborne J S and Adamek S Some compounds of gas 44 Smith M J, Colligan M J and Hurell J J Three Incidents of Industrial phase of cigarette smoke Atllll. Chem. 28 211-215 (1956) Mass Psychogenic Illness J. Occ. Medicine 20 399-400 (June 1978) 19 Molhave L Indoor air quality in relation to sensor:)' irriumon co volatile 45 Hawkins L H Air Ions and Office Health Occ. Health 116-124 organic compounds ASHR.4E Trans. 92(1A) 306-316 (1986) (March 1982) 20 Brundren G W V encilation Requiremenr.s in Rooms Occupied by 46 Assael M, Pfeifer Y and Su!man F G Influence of Aniiicial Air Smokers: A Rl!'/,-iew (Cape:iliurst, Ches•er: Electricity Council Research Ionization on the Human Eiecr:roencephalogram Int. J. Biomecior. 18 Centre) (l 975) (4) 30~-Jl2 (1984) 21 Sterling T D and Sterlng E M I nvescigations on the Ef[ecc of Regulating 47 Rim Y Psychological Test Performance oi Different Personality S making on Levels of Indoor Pollution and on the Perceprion of Health Types on Sharov Days in .\rti.ficial Air Ionisation Int. J. Biometior. 21 and. Comforc of Office Worker E:.irop. J. Resp. Diseases 65(133) 17-32 (4) 337-340 (1977) (1984) 48 Krueger A P and Reed E J Biological Impact of Small Air Ions 22 Sterling T D el al. Environmental Tobacco Smoke and Indoor Air Science 1209-1213 (24 September 1976) Qualiry in Modern Office Environments J. Occ. MediciM 29 Si-62 49 Krueger A P and Smith R F Negative Air ion effects on the con (Jan. 1987) centration and metabolism of S hydroxyrripramine in the mammalian 23 Wallace L and Bromberg S Plan and Preliminary Results of the US respiratory tract J. General Physiol. 44 269-276 (1960) Environmental Protection Agency's Indoor Air Monitoring Program 50 David T A ec al The Sedating Effect of Polarised Air Proc . 2nd Inc. 1982 Indoor Air Vol. 1 (Swedish Council for Building Researcll) Bioclimacological Congress, Royal Soc. Medicine, London4-10 Sepe 1960 (1984) (Oxford: Pergamon) (1962) 24 Ventilation for Acceptable Indoor Air Qualicy ASHRAE Standard 62- 51 Albrechtsen 0 et al Influence of Small Atmospheric Ions on the 1981 (Atlanta, GA: American Sociery of Heating, Refrigeration and Airways in Patients with Bronchial Asthma (Technical University of Air Conditioning Engineers) (1981) Denmark) 25 Meyer B Formaldehyde Release from Building Products indoor Air 52 Hamburger R J On the Influence of Artificial Ionisation of the Air Vol. 3 (Swedish Council for Building Research) (1984) on the Oxygen Uptake During Exercise Proc. 2nd In1. Bioclimatological 26 Wanner H U and Kuhn M Indoor Air Pollution by Building Cong. London 4-10 Sepe 1960 Materials indoor .4.ir Vol. 3 (Swedish Council for Building Research) 53 Ball D J A Sceptic's View of Air Ionisation Building Ser.:. Environ. (1984) Eng. 21-22 (September 1982) 27 Dement JM ec al An Evaluation of Formaldehyde Sources, Exposure 54 Hedge A and Collis M D Do negative ions affect human mood and and Possible Remedial Actions in Two Office Environments Indoor performance? Ann. Occup. Hyg. 31(3) 285-290 (1987) Air Vol. 3 (Swedish Council for Building Research) (1984) 55 Negative ion generators US Food and Drug Administration (5 Feb 1980) 56 Hawkins L H and Morris L Air Ions and Sick Building Syndrome 28 Matthews T G ec al Formaldehyde Emissions from Consumer and Indoor Air Vol. l (Swedish Council for Building Research) (1984) Construction Products: Potential Impact on Indoor Formaldehyde 57 Finnegan M J ec al Effect of negative ion generators in a sick building Concemrations Ind.oar Air Vol 3 (Swedish Council for Building Bri1. Med]. 294 1195-1196 (1987) Research) (1984) 58 Robenson A and Burge S Building Sickness-all in the mind? Occu 29 Sundin B Formaldehyde emission from wood products; technicil pational Health (March 1986) experiences and problem solutions from Sweden Proc. 3rd Medical 59 CIBSE Guide (London: Chartered Institution of Building Services Legal Symposium on Formaldehyde Issues, Washingcon, DC, Oct 22-23 Engineers) (1988) 1982 60 Youle A Occupational Hygiene Problems in Office Environments: 30 Anderson I and Korsgaard J Asthma and the Indoor Environment: The Influence of Building Services Ann. Occ. Hyg. 30 (3) :75-287 Assessment of the Health Implications of High Indoor Air Humidity (1986) Indoor Air Vol. 1 (Swedish Council for Building Research) (1984) 61 Janssen J E and Hill T J Ventilation for Control of Indoor Air 31 Bishop V L, Custer D E and Vogel RH The Sick Building Syndrome. Quality: A Case Study Environmenc incernational 8 487~96 (1982) What it ls and How to Prevent It Narional Safety & Health News 31- 62 Gil per in A Humidification and upper respiracory infeccicm incidence 38 (December 1985) HeacingiPiping i.4ir ConJ.icioning 77-78 (March 1973) 32 Custer D E Sources of Building Contamination Nacional Safety & 63 Green G H Field Studies of che effecc of air humidity on respiratory Health News 38-10 (December 1985) diseases. Indoor climate 10 Building Services Engineering Research and Technology Sick building syndrome 64 Green G H The Health Implications of the Level of !ndoor Air 80 Visual Display Uniu ISBN 0 11 883685 -4 (London: Health & Safety Humidity Indoor Air Vol 1 (Swedish Council for Building Research) Executive/HMSO) (1983) (1984) 81 Hicks J B Tighe Building Syndrome: When Wark Makes You Sick 65 Sale C S Humidification to reduce respiratory illnesses in nursery Occuparional Health & Safer; 51-57 (January 1984) school children Southern Med.]. 65 (7) (1972) 82 Rittficld R et al Indoor air pollutancs due ro door tiles Indoor Air 66 Dimmick R Land Akers AB An Inaoducrion UJ Experimenll1.l Aero Vol. 1 (Swedish Council far Building Rese:irch) (1984) biology (New York: Wiley) (1969) 83 Hansen T B and Andersen B Ozone and Other Air Pollutants from 67 Tromp S W Medical Biameuorology (Amsterdam: Elsevier) (1963) . Photocopying Machines Amer. Ind. Hyg. :!ssoc. ] . 47(10) 65~65 68 Andersen I, Lundqvist G R and Proctor D F Human Mucosa! (1986) function under four controlled humidities :!.mer. Rev. Respiratory 84 Hanssen S 0 and Radahl E An Office environment-problems and Diseases 101 43!1-+49 ( 1972) improvements Indoor Air Vol. 3 (Swedish Council for Building 69 Ewart G On the mucous fiow rate in the human nose Acli1. Oto. Research) (1984) Laryng. (S1ocklwim) 200 (suppl 21) 56 (1965) 85 Andersen I, Lundqvist G Rand Molhave L Indoor air pollution due 70 Mcintyre D A Subjecrive Responses UJ Relarive Humidiry: A Second ro chipboard used as a construction material Al7110spheric Environment Experimen1 (Capenhurst, Chester: Electricity Council Research Centre) 9 1121-1127 (1985) (February 1975) 86 Bell S J and Khati B !ndoar Air Quality in Office Buildings Occu 71 Imemarional SUJndard ISO 7730-1984 : Moderaie thermal mviron pational Health in Onll1.rio 4(3) (July 1983) ments-Deierminarion of 1he PMV and PPD indices and specificarion of 87 Repace J M [ndoor Air Pollution Environment Incernarional 8 22-36 the condirion.s for thermal comfart ( 1984) (1982) 72 Bedford's Basic Principles ofVenrilarion and Hearing (London: Lewis) 88 Woods J E Ventilation, Health & Energy Consumption: A Scams . (1974) Report ASHRAE ] . 2>-27 (July 1979) 73 Waller RA Case Srudy of a Sick Building Indoor Air Vol. l (Swedish 89 McNall P E Building Ventilation Me::i.surements, Predictions and Council for Building Research) (1 984) Standards Proc. Symp. Indoor .4ir Pollurion , New York Academy oj 74 Int Hout L Tight Building Syndrome: Is it hot air? Heating /Piping! Medicine, 1981 Air Condirioning 99-103 (January 1984) 90 Schulte J H Sealed Enviromnents In Relaricm to Health and Disease 15 Marthews R Pollution Begins at Home New Scienrist (5 December (US Navy, Submarine Medicine Division) (.\1arch 1964) 1985) 91 Walkinshaw D S Indoor air quality research in Canada Proc. Indoor 76 Griffiths W A D and Wilkinson D S Essenriais of Industrial Der Air Quaiicy Seminar, .4tianta, Georgia, 1984 macology (Oxford: Blackwell) (1985) 92 Air Conditioning. ls it good for you? (London: Heating and Ventilating 77 Hanssen S 0 and Rodahl E An Office Environment-Problems and Contractors' Association) Improvements I ndour Air Val. 3 (Swedish Council for Indoor Research) 93 BS 5720: 1979: Code of pracrice fur mechanical ventilation and air (1984) conditioning in buildings (M.i.lton Keynes: British Standards Instirution) 78 Richards A Office Sickness syndrome Occuparional Health & Safery (1979) (February 1986) 94 Kroeling P Health and wellbeing disorders in air conditioned build· 79 McLellan R K The Health Hazards of Office Work Toxic SubsUJnces ings: Comparative investigations of the 'Building Illness Syndrome· ]. 5(3) l'!i2-181 (Oct. 1983) Energy and Buildings 11 277-282 (1988) .. Vol. 10 No. 1 (1989) 11 ~~~~'· ..··~G~.zy~n~ . !~, "4~: •9~. ·~- ·~·~· -~--~·"""'~~~7~>..-~~-...... CMO~ ...... ~s~~~·~· ~"~"...... ,._.....-"'f'1 -~