Indoor Air, 4, 357-376 (1991) © 1991 Munksgaard, DK-Copenhagen Volatile Organic Compounds, Indoor Air Quality and Health Lars Mfl)lhave1 AbstraC:t lntrodudion 'I'his publication summarizes field investigations and Volatile Organic Compounds controlled experiments on the relation between low le­ vels ofindoor air pollution with volatile organic com-­ and Health pounds (VOC) and human health and comfort. 1'he Volatile organic compounds (VOC's): VOC's Henle-Kock criteria from epidemiology are reoised for are :frequent air-pollutants-in non-industrial the dose-response relation between VOC's and health environments. A WHO working group cate­ as comfort effects and existing e'lJidence for each criter­ gorized the entire range of organic indoor ion are discussed. A biological model for human re­ pollutants into four groups, as indicated in sponses is suggested, based on three mechanisms: sen­ Table 1. The four categories were defined by sory perception of the environment, weak inflammatory boiling-point ranges and no sharp limits ex­ reactions, and environmental stress reactions. Further, ist between them. The VOC category was de­ the TVOC-indicator concept for exposure is discussed. fined by a boiling-point range with a lower 1'he conclusion is that no experimental or field data contradict the proposed causality. On the contrary, evi­ limit between 50 °C and 100 °C and an upper dence supports the suggested causality. 1'he biological limit between 240 °C and 260 °C, where the model, however, is not yet based on acceptable meas­ higher values refer to polar compounds ures of the variables for exposures, co-variables or (WHO, 1989). health effects. A tentative guideline for VOC's in A recent review lists 307 VOC's identified non-industrial indoor environments is suggested. 1'he in indoor air in different countries (Berglund 3 no-effect level seems to be about 0.2 mg/m • A multi­ et al., 1986). The WHO report (WHO, 1989) factorial exposure range may exist between 0.2 and 3 on VOC's indoor summarized the concentra­ 3 mg/m • Above 3 mg/m3 discomfort is expected. tions found in four major European studies (Krause et al., 1987; De Bortoli et al., 1986; Le­ bret et al., 1986; Wallace, 1987). In summary, normally 50 to 300 volatile organic compounds are found in air samples from most non-indus­ trial environments. Each compound seldom 3 exceeds a concentration of about SO µglm , KEYWORDS: which is 100 to 1000 times lower than relevant Health, Comfort, Perceived indoor air quality, En­ occupational threshold values (TLV's) (AC­ vironmental stress, TVOC, Volatile organic com­ GIH, 1988). An upper extreme average total pounds. concentration of all VOC's in normal homes seems to be 20 mglm3 (M~lhave, 1986). The to­ Manuscript received: 22 October 1990 3 Accepted for publication: 19 December 1991 tal concentration of all VOC's (mglm ), how­ 3 ever, is normally well below 1 mglm , which is ' Institute of Occupational and Environmental Medi­ cine, University of Aarhus, Building 180, Universitet­ only 0.2% of the occupational threshold limit sparken, DK-8000 Arhus C., Denmark. value (TLV) for toluene. 358 M0lhave: Volatile Organic Compounds, Indoor Air Quality and Health Table 1 Classification of indoor organic pollutants •. Description Abbreviation Boiling-point range ("C)b Very Volatile (gas~us) Organic Compounds woe < 0 to 50-100 Volatile Organic Compounds voe 50-100 to 240-260 Semivolatile Organic Compounds svoc 240-260 to 380400 Organic Compounds Associated with Parti­ culate Matter or Particulate Organic Matter POM > 380 • From WHO 1989. b Polar compounds appear at the higher end of the range. Health of the special effects are not caused by the air Health has been defined by WHO as "A state pollutants themselves, but by e.g. metabolites of complete physical, mental and social as in the case of the neurotoxicity of n-hex­ well-being and not merely the absence of dis­ ane and certain ketones, the ocular toxicity ease or infirmity'' (WHO, 1961). The toxic ef­ of methanol, or the hepatoxicity of certain fects of volatile organic compounds may be chlorinated hydrocarbons. A list of special defined as any significant change caused by effects of VOC's and commonly used tests VOC's on a person when compared to other­ for such effects are shown in Table 2, which wise comparable, but unexposed persons. is adapted from Andrews et al. (1986). This Such effects may be classified in effects com­ table lists effects or tests commonly used in mon to most VOC's and effects specific for human studies of normal industrial organic individual compounds. solvents at or above TLV-levels. Reviews of The special properties of individual com­ such special effects are found in textbooks. pounds may result in unusually high intens­ Special effects like genotoxic effects or ef­ ity or prevalence of common effects (such as fects on the immune system are severe for neurotoxic effects, cancer, or allergy). Many the few unlucky occupants affected by them. Table 2 Symptomatology and commonly used tests for behavioral effects caused by VOC°. Symptomatology Test Sensory: Parasthesias, visual or auditory deficts Neurologic, sight, and hearing examinations Cognitive: Memory (both shon-tenn and long-tenn), Wechsler Memory Scale confusion, disorientation Wechsler Adult Intelligence Scale (WAIS) Affective: Nervousness, irritability Eysenck Personality Inventory depression, apathy, compulsive Rorschach Test behavior Digit-symbol Substitution Task Bourdon-Wiersma Vigilance Task Motor: Weakness in hands, incoordination, Neurologic examination fatigue, tremor Santa Ana Dexterity Test Finger-tapping Test Simple or Choice Reaction Time a Andrews et al., 1980. \ ' \ L 1~ : Mr1.1lhave: Volatile Organic Compounds, Indoor Air Quality and Health 359 They are, compared to what we know, rare ginally were developed for the causality of effects in relation to low-level voe expo­ diseases described by a spectrum of re­ :-point range (oC)b sures in normal indoor environments. Such sponses and caused by specific agents. These effects, however, may evade registration if criteria have been revised in this paper for : 0 to 50-100 their prevalence is too small to cause a statis­ 00 to 240-260 tically significant association in a population Table 3 Henle-Kock-criteria for causation revised for 60 to 380-400 of the size found in most normal non-indus­ the effects of low-level voe exposure among occu­ trial buildings. In the future, they should be pants of non-industrial indoor environments". > 380 investigated further. 1) A spectrum of responses should follow exposure to This paper is focused on the causality be­ VOC's along a predicted biological gradient from hind the more common effects of VOC's ac­ mild to severe. cording to the above definition. These also 2) A measurable response following exposure to VOC's happen to be the most frequent effects of should regularly appear among occupants lacking low-level voe exposure. For simplicity, the this before exposure or should increase in magni­ caused by the air tude if present before exposure. r e.g. metabolites effects of low-level exposures to VOC's will be divided into a) disturbances of body func­ 3) Exposure to VOC's should be present more com­ oxicity of n-hex­ monly in those showing the effect than in controls e ocular toxicity tions and b) perception of the environment without the effect when all risk factors are held xicity of certain or of body conditions. Further, to avoid con­ consomt. A list of special fusion, the term perceived indoor air quality 4) Temporality: The effects should follow exposure to nonly used tests (PIAQ) will be used for the subjectively per­ VOC's (possibly with a delay time). n Table 2, which ceived air quality in contrast to measured in­ 5) Elimination ofmodification of the VOC exposure or t al. (1986). This door air quality (MlAQ) which is the chemic­ prevention or modification of the occupants' sensi­ ally or physically measured indoor air qual­ tivity to exposure should decrease or eliminate the mmonly used in effect. idustrial organic ity, e.g. in the form of air temperature, air humidity, pollution concentrations, etc. A 6) Experimental reproduction of the effects should pro­ :vels. Reviews of duce higher incidence in animals or humans ap­ l in textbooks. distinction will be made between the occu­ propriately exposed to VOC's than in those not so >Xie effects or ef­ pants' adapted perception after exposure for 1 exposed. n are severe for hour or more and the visitors' immediate 7) The etiology must make biological sense. 1ffected by them. and adapted response upon entering the room. Generally, in this paper these two • Evans 1976. types of evaluation are referred to as subacute and acute responses. Also, the term "irrita­ Table 4 Four criteria for acceptable biological expla­ tion" will be specified as either stimulation nation of the etiology between low-level voe exposure of sensory systems, inflammatory-like skin and observed effects". a.ations reactions, or a psychologic mood condition. 1) Reasonable and documented biological mechan­ If not specified, sensory irritation is meant. ism, must be used for the explanation of the ob­ served symptoms or effects. Criteria for Causality 2) The variables (effects, exposures and cofactors) in­ Tables 3 and 4 show a suggested set of criter­ volved in the suggested etiology must be measur­ ia for causality and for biologically reason­ able: alternatively acceptable indicators must be available. able etiologies in relation to voe exposures at low levels and health effects as they may 3) The effects or symptoms and expected mechan­ isms should preferably be known from similar or occur in non-industrial indoor environ­ higher exposure levels to VOC's. ments. In epidemiology, the criteria in Tables 4) The etiology must explain any delay (latency) in 3 and 4 are known as the Henle-Kock-criter­ responses following exposure to VOC's.