Interactions between noise and air pollution

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  • Environment International, Vol. 16, pp. 593-601, 1990 0160-4120/90 $3.00 +.00 Printed in the U.S.A. All rights reserved. Copyright @1990 Pergamon Press pie


    M. Haider, M. Kundi, E. GrolI-Knapp, and M. Koller Institute of Environmental Hygiene, University of Vienna, 1095 Vienna, Austria

    E188-202 (Received 15 October 1988; accepted 20 January 1990)

    A theoretical framework for the discussion of interaction effects between noise and air pollutants (e.g., carbon monoxide, heavy metals, and organic solvents) on the auditory system as well as on extraaural systems is presented. The interactions are categorised into five groups: local interac- tion, independent action, dependent aftereffects, transaction, and general interaction. Information on combined effects of carbon monoxide and noise, as well as carbon monoxide and nitrogen oxide, serve as examples how the different intensities of effects, as well as the different effect levels, may be taken into account within the described theoretical framework. The problem of sensory interactions as well as combined annoyance effects are analysed with the same conceptual approach.


    In an early review paper on influences of chemi- cal agents on hearing loss (Haider 1973), it was stated that, analogue to drug studies, the combined effects might be classified as indifferent, additive, hyperadditive (synergistic, potentiating), or hypoaddi- tive (antagonistic, protective). Since this time this group has performed several experimental and epidemiological studies of combined effects but has also worked on the development of a conceptual framework, taking the different intensities of effects within the organisms as well as the different effect levels into account. This part of the work has been developed by Kundi (1987). He showed that, within a graphtheoretical approach, one may categorize the

    interaction of effects into five groups, comprising exhaustively the possible interaction types of two environmental factors.

    In this paper each observable reaction of an organ- ism to one or more environmental influences will be called "effect". These effects may be independent, linked with each other, or be distinguished according to their effect level. The complexity of effect levels increases with the number of organismic activities involved and with the number of links between these activities. For classification purposes one may con- centrate on a single activity Ai which is directly affected by the environmental influence nl and a single activity Aj (which might in fact be Ai) which is affected by the environmental influence n2. Fig. 1 gives graphic representations of five possible types of interaction.


  • 594 M. Haider et al.

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    I . Local I n teract ion I I . Independent Act /on

    I l l . Dependent Af tere f fec ts IV. T r~sact ion V, General In teract ion

    . . . . . . . . .

    If . . . . . . . . I

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    Fig. I. Graphs of five possible types of interaction between environmental influences (Kundi 1987).

    The five types may be characterized as follows: I - Local interaction: If both environmental influ-

    ences act upon the same activity (Ai = Aj), all effects on the post-set of this activity depend only on the combined effects on this activity. All effects observed on a higher level are comparable to those observed if only one in- fluence was present.

    II - Independent action: If the environmental in- fluences act upon different activities whose post-sets are mutually exclusive, no inter- action can occur, thus all effects are inde- pendent. This results in mutually dominant combined effects. If m(nt) >0 it follows that m(n2) = O and m(nl+n2) = m(nl) and vice versa (m denotes a response metameter standard- ized to give O if no response occurred and a value >0 if a response has been observed). However, it is unlikely that independent ac- tion of this type can ever occur in an organ- ism since there is nearly always some sort of linkage between any two activities. Neverthe- less, these linkages might be very weak so that for practical purposes one can classify the effects as independent.

    I I I - Dependent aftereffects: If there is an activity Ak different from activities At and Aj, but influenced by both of them, they may be called dependent aftereffects.

    IV - Transaction: If the activity which is affected by one of the environmental influences is also impacted by the activity affected by the other one, we speak of transaction. Combined ef- fects can only occur on the higher level activ- ities and their post-set.

    V - General interaction: If Ai and Aj lie in a circle, the effects of the environmental influences nt and n2 on activities Ai and Aj are always linked, hence all effects are of a combined type.

    IVt, VI ' Higher order transaction or interac- tion: Transaction or interaction may not only occur between activities A~ and Aj but also on the higher order activity AI, which is different from Ai and Aj, but influenced by both.

    In the following report the occurrence of different types of interaction between air pollution and noise are shown. Furthermore, an attempt is made to dis- tinguish between studies dealing with different sites of the auditory system and studies dealing with ex- traaural systems.

  • Noise and air pollution 595


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    Examples for ototoxic agents and their interaction with noise

    A review of the evidence on ototoxic agents other than noise has been given by Hetu et al. (1987). These authors state that two conditions are required to af- firm that an agent is ototoxic: it must induce a consistent response on the auditory system and this response must be experimentally reproducible.

    As examples for the theoretical analysis, carbon monoxide, heavy metals, and certain organic sol- vents are discussed in relation to adverse structural or functional effects on the auditory system, includ- ing the inner ear, the auditory pathways, and the cor tex .

    Carbon monoxide: Several case reports have been published on acute and chronic effects of carbon monoxide on hearing (Lumio 1948a, b; Wagemann 1960; Taniewski and Kupler 1964; Zenk 1965; Baker and Lilly 1977). The hearing loss appears to be re- versible in most cases and is associated with a central nervous system toxicity. In an extensive epidemio- logical investigation, CO was reported as a frequent cause of "industrial toxicosis" (Surjan et al. 1973). In our own studies we investigated the level of the inner ear as well as on the cortical levels. To get some information on the combined effects of noise and CO on temporary threshold shifts (TTS), 20 subjects were exposed to 223 mg/m 3 CO over a period of four hours. They reached COHb-levels with a mean of 13%. In a double-blind design they were also ex- posed to normal air for the same period. The order of these two experimental situations was randomized. In both sessions the subjects were exposed during the last 15 min to 105 dB octave band noise with a mid- dle frequency of 2000 Hz. Measurements of TTS at 3 kHz were taken after 4, 8, 16, and 64 minutes. One result is shown in Fig. 2. No significant difference between the CO condition and the control condition with normal air could be established.

    Auditory perception tasks appear consistently sen- sitive to acute effects of exposure levels between 58 to 287 mg/m 3 during 2 to 5 hours (Beard and Wertheim 1967; Groll-Knapp et al. 1972; Fodor and Winneke 1972). Acute CO poisoning of guinea pigs demonstrated severe but reversible loss of auditory sensitivity, which was clearly associated with corti- cal and, to a lesser extent, subcortical dysfunction (Makishima et al. 1977).






    4 8 16 32 64 gin.

    Fig. 2. Temporary threshold shift at 3000 Hz after noise expo- sure (105 dB, 15 min) during a CO exposure (223 mg/m *, 4 h)

    and in a control condition with normal air.

    Concerning high-dose effects (30-50% COHb), car- bon monoxide has a hyperadditive effect in combina- tion with noise as shown by histologic changes in the organ of Corti, as well as by reflex audiometry (Kittel and Theissing 1968; Fechter et al. 1987, 1988).

    Heavy Metals: Heavy metals are traditionally men- tioned as possible ototoxic agents but very few stud- ies have verified this possibility.

    Hearing disabil ity has been reported as a symp- tom associated with lead-poisoning (Ciurlo and Ottoboni 1956). Two studies conducted on guinea pigs confirmed this contention, showing VIII nerve axonopathy, the inner ear appearing otherwise in- tact (Gozdzik-Zolnierkiewicz and Moszinski 1969; Yamamura et al. 1984).

    Inner ear disorders have been repeatedly ob- served following arsenical intoxication on animal subjects (Ruedi 1951; Leonard et al. 1971; Anniko and Wersall 1975). The damage seems to appear in the stria vascularis followed by disorders in the various com- ponents of the organ of Corti. Sensorineural hearing

  • 596 M. Haider et aL

    loss (more pronounced in the low frequencies) has been measured in a significantly higher proportion of children exposed to environmental arsenic than in a group of controls. No comparable study has been conducted among the various groups of workers chronically exposed to arsenic (Landrigan et al. 1982).

    Mercury is considered as ototoxic from the results of the study on the people from Minamata Bay in Japan who showed hearing losses in a large majority (Kurland et al. 1960). Results from a study on guinea pigs intoxicated with methyl mercury demonstrated besides other symptoms, sensory cell destruction in the inner ear (Falk et al. 1974). A study of hear- ing loss among industrial workers has suggested a combined effect of noise and mercury exposure (Eggemann et al. 1977).

    Organic solvents: Animal experiments with rats dem- onstrated the toxicity of toluene as well as styrene and xylene on the sensory cells of the inner ear (Rebert et al. 1983; Pryor and Rebert 1984). Results of cross-sectional studies on samples of workers suggest that carbon disulfide, carbon tetrachloride, trichlorethylene, and n-butanol induce sensorineural hearing loss (Barregard and Axelsson 1984). Lehnhardt (1965) described clinical cases of interac- tion effects between trichlorethylene and noise. A

    review on the neurotoxicity of organic solvents suggests that the hearing loss could be an early indicator of organic solvents neuropathies (Spencer and Schaumburg 1985) and that they could interact with noise by the intermediate of their effect on the acoustic reflex.

    Types of interactions between noise and air poilu. tants in the auditory system

    Table 1 gives a summary on the described exam- ples of environmental influences with adverse effects on the auditory system and their probable site of interaction with noise. Effects of carbon monoxide in the inner ear are in parentheses since they occur only with high doses.

    A comparison is now made of the overview in Table 1 with the types of interactions outlined in the introduction and shown in Fig. 1. From this compar- ison it may be concluded that noise and heavy metals, as well as noise and some organic solvents, show local interaction effects on the inner ear, which was described in the introduction as interaction Type I. Concerning carbon monoxide effects there is a dis- tinct difference between high-dose effects and low- dose effects. Only high doses have local interaction effects on the inner ear. The typical low-dose effects are on the cortical level and will be discussed later.

    Table 1. Agents for which ototoxicity is suspected (7), demonstrated on animals (*) and humans (x), and their probable site of interac- tion effects with noise (Hetu et al. 1987).

    Suspected Agent Probable Site of Interaction

    inner auditory auditory ear pathway cortex

    carbon monoxide

    Heavy metals




    Organic solvents




    white splits (mixed solvents)

    carbon disulfide

    carbon tel~acl~oride







    7 ?



    ? ?


  • Noise and air pollution 597

    The high-dose effects are, however, a good example for the kind of local interaction, whereby both envi- ronmental influences (noise and air pollutant) act on the same common activity, namely the oxidative me- tabolism of the inner ear. Fechter et al. (1988) could demonstrate that simultaneous exposures to noise and carbon monoxide resulted in chronic effects on pure tone thresholds and hair cell survival in rats. The data showed that carbon monoxide alone did not affect either auditory thresholds or compromise hair cells at the light microscopic level. Noise exposure alone produced variable, but quite limited, perma- nent threshold shifts and a hair cell loss which was restricted to the basal turn of the cochlea. But simul- taneous exposure to carbon monoxide and noise-in- duced large threshold shifts at all frequencies studied. The authors conclude that these data complement existing evidence that hyperoxia can mitigate against noise-induced injury and reinforce the view that some types of noise-induced damage may result from met- abolic insufficiencies.

    Noise and some other pollutants, like sulfur ox- ides, may work independently on two different activ- ities (respiratory activity and hearing constitute interaction Type II). Noise and lead may show dependent aftereffects on the auditory pathways (interaction Type Ill). Noise and low doses of carbon monoxide will show transactional effects (Type IV), especially of a higher order (Type IV1).


    Besides the effects on the hearing system, noise also produces extraaural effects on different func- tional systems of the organism. The central nervous system, the cardiovascular system, and annoyance in relation to research of interactions between noise and air pollution will be discussed here.

    Combined effects on the central nervous system

    Effects of moderate carbon monoxide exposure dur- ing wakefulness and sleep and its interaction with acoustic information processing. As discussed pre- viously, the local interaction effects of high-dose carbon monoxide and its interaction with noise are based on the common actions on the oxidative metab- olism of the inner ear. Since the central nervous system has a high oxygen consumption it has to be considered as one of the critical organs in term of exposure to carbon monoxide and its interaction with noise. Many experiments under moderate and low CO exposure conditions have shown effects on acous-

    tic information processing in the central nervous system. The capacity for continuous observation of weak or infrequent acoustic stimuli, as in a vigilance task or cognitive abilities, proved to be sensitive indicators of CO-ind...