interactions between noise and air pollution

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

INTERACTIONS BETWEEN NOISE AND AIR POLLUTION

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 interaction, 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.

INTRODUCTION: A THEORETICAL FRAMEWORK FOR THE DISCUSSION OF INTERACTION EF- FECTS

In an early review paper on influences of chemical 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 organism 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.

593

594 M. Haider et al.

I N

i i :

B i , m I

N

: ~ - - t - - ~"

V

I . Local I n t e r a c t i o n I I . Independent Ac t / on

I l l . Dependent A f t e r e f f e c t s IV . T r ~ s a c t i o n V, Genera l I n t e r a c t i o n

. . . . . . . . .

If . . . . . . . . I

" \ , ../

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 influence was present.

II - Independent action: If the environmental influences act upon different activities whose post-sets are mutually exclusive, no interaction can occur, thus all e f fects are independent . 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 action of this type can ever occur in an organism 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 effects can only occur on the higher level activities 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 interaction: 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 distinguish between studies dealing with different sites of the auditory system and studies dealing with extraaural systems.

Noise and air pollution 595

STUDIES CONCERNED WITH COMBINATION EF- FECTS AT DIFFERENT SITES OF THE AUDITORY SYSTEM

ITS 3 0 0 0 IIz E ¢ |

. . . . ¢ o n l r . I

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 solvents are discussed in relation to adverse structural or functional effects on the auditory system, including the inner ear, the auditory pathways, and the c o r t e x .

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 reversible in most cases and is associated with a central nervous system toxicity. In an extensive epidemiological 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 exposed 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 sensitive 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 cortical and, to a lesser extent, subcortical dysfunction (Makishima et al. 1977).

16

16

14

12

10

4 8 16 32 6 4 g in .

Fig. 2. Temporary threshold shift at 3000 Hz after noise exposure (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), carbon monoxide has a hyperadditive effect in combination 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 studies have verified this possibility.

Hearing disabi l i ty has been reported as a symp- tom associa ted 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 observed 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 hearing loss among industrial workers has suggested a combined effect of noise and mercury exposure (Eggemann et al. 1977).

Organic solvents: Animal experiments with rats demonstrated 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 interaction 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 examples 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 comparison 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 interaction effects with noise (Hetu et al. 1987).

Suspected Agent Probable Site of Interaction

inner auditory auditory ear pathway cortex

carbon monoxide

Heavy metals

lead

arsenic

mercury

Organic solvents

toluene

styrene

xylene

white splits (mixed solvents)

carbon disulfide

carbon tel~acl~oride

trichlorethylene

n-butanol

(*)

X*

X*

?

7

?

?

?

? ?

X*


The high-dose effects are, however, a good example for the kind of local interaction, whereby both environmental 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 simultaneous exposure to carbon monoxide and noise-induced 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 activities (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).

STUDIES CONCERNING COMBINATION EFFECTS ON EXTRAAURAL SYSTEMS

Besides the effects on the hearing system, noise also produces extraaural effects on different functional 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 during wakefulness and sleep and its interaction with acoustic information processing. As discussed previously, 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-induced behavioral impairments, while complex psychomotor tasks showed no reliable impairment. Neurobehavioral effects of moderate COHb-concentrations are summarized and the discrepant results are discussed in a review article by Laties and Merigan (1979).

Central information processing can be evaluated by recording the electrical activity of the brain at different levels of specifity, like spontaneous EEG activity, evoked potentials, slow potential shifts, or DC shifts. Spontaneous EEG has yielded no reliable difference during acute exposure to low levels of CO. Hosko (1970) found no alteration in spontaneous EEG with COHb levels as high as 33%. O'Donnell ¢t al. (1971) found alterations in EEG sleep patterns during exposure to 85 and 172 mg~m 3 for seven hours of nocturnal sleep. A nonsignificant trend toward increased duration of deep sleep (stages 3 and 4) was noted. CO-induced changes were more pronounced but not significant during the early phases of sleep when COHb levels were lower. It was hypothesized that early adaptation mechanisms were stimulated by CO exposure during the initial three hours.

The analysis of evoked potentials (EP) and slow potential changes permits investigation of processes that are more specific than those reflected in the spontaneous EEG. Changes in EPs as an indicator of CO-induced functional CNS deterioration during wakefulness were investigated by Hosko (1970). No significant changes in peak latencies of amplitudes of visual EPs were found below 15% COHb. With COHb levels between 20 and 22%, an increase in amplitude of the late potential component (70 ms) and a negative-going shift after P 120 were observed.

In earlier studies (Groll-Knapp et al. 1982) the effects of carbon monoxide on brain wave activity and auditory-evoked potentials during sleep were measured in 20 subjects (10 healthy young volunteers between 20 and 25 years and I0 healthy elderly volunteers between 55 and 72 years). The experimental nights were counterbalanced with respect to control and exposure conditions. Eight hours of carbon monoxide exposure (115 mg/m 3) gave rise to about 8% COHb. In the group of young subjects there was a signifcant (p < 0.05) increase of deep sleep (stages 3, 4) and a decrease of stage REM-slevp during exposure to carbon monoxide. The auditory-evoked potentials had significantly higher amplitudes in young subjects under the influence of carbon monoxide.


It may be concluded therefore that a high order type of interaction exists between carbon monoxide and acoustic information processing in the central nervous system during wakefulness and sleep.

Effects of combined exposure to nitric oxide and carbon monoxide on acoustic evoked potentials. In a series of animal studies the combination effects of carbon monoxide and nitric oxide on acoustic information processing were analysed. The data on the combined effects of carbon monoxide and nitric oxide have been published recently (Groll-Knapp et al. 1988). In this study the interactions were investigated at different effect levels. This included blood parameters (carboxyhemoglobine and methemoglob- ine) as well as centrally mediated effects studied on cortical acoustic evoked potentials and on behav ior in a complex discrimination learning experiment. On the level of carboxyhemoglobine and methemo- globine formation only slight changes occurred which disappeared with prolonged exposure. But the behavioral effects as well as the effects on the acoustic evoked potentials were additive at lower levels of exposure intensities and hyperadditive at higher levels of exposure intensities.

Combination effects of acoustic stimulation and carbon monoxide on cortical DC shifts. Because previously published information (Haider et al. 1984) lacked details, these are provided here.

Materials and Methods: Special agar- imbedded Ag/AgCI sintered electrodes were chronically im- planted epidurally over the prefrontal and parietal regions of both hemispheres of 12 rats, and the ref- erence electrode was fixed over the nose bone. A special DC-amplification system, which allowed a resolution of 1 ttV in the range of 1 V, was used. In an operant chamber, the rats were exposed to a series of battle cries with a mean frequency of 24 KHz, 90 dB, lasting 27 s. The battle cries were registered with a tape recorder during fights between rats. For comparison an energy-equivalent series of artificial sinustone-stimuli was presented. Ten trials during each session were computer-averaged. For each of the individual averages the amplitude of the on-effect was measured and the DC-integral over the whole stimulation period was calculated. With 5 of the 12 animals, the whole procedure was repeated under the influence of carbon monoxide.

Results: The DC shifts during the 27-s exposure of the rats to 90 dB series of battle cries resulted in a negative DC-shift of about 70 ~tV over the whole exposure time with clear on- and off-effects. The energy- equivalent artificial tone-series led to a smaller on-effect

and the curves returned to the baseline, before the acoustic exposure time ended. The amplitude of the on-effect as well as the DC integral were significantly different (Mann-Whitney U-Test, p < 0.05)

The differences in the computer-averaged cortical De-shifts of the 27-s battle cry series with and without CO exposure of one rat are shown in Fig. 3.

Under the influence of CO, the negative DC shifts, which in normal air last over the whole exposure time of 27 s, are apparently changed. There is a clear on-effect at the onset of the noise, but after a few seconds the negative DC shift is ended. The curves return to the baseline even in the case of the biologically significant series of battle cries. The CO effect, if added to a biologically significant acoustic stimulation, changed the stimulus-induced negative DC shift. The curves of the combined effect were for the biologically significant stimulation similar to the biologically insignificant artificial tone series in normal air. All five animals tested showed changes in the same direction.

The results show that functional changes of information processing are induced if CO and acoustic stimulation occur simultaneously. In this case we have a transaction effect of a higher order (Type IV1), assuming that Ai and Aj are different specific activities of the brain linked to each other, but Ak shows the interaction on a higher activity level.

Combined effects on the cardiovascular system

Included in this group are those dealing with the inf luence of physical and chemical environmental factors (noise, vibrat ion, temperature, dust, and exhaust gases) on the cardiovascular system. Navakatikyan (1984) found in persons with functional modifications or pronounced pathology of the cardiovascular system, the product of intensity of exposure by length of service (i.e., cumulative dose) to be higher than in healthy persons. It may be as- sumed that all effects are of a combined type, repre- senting general interaction (Type V).

Types and levels of annoyance effects

Evaluation of annoyance is even more complex because of problems dealing with different types and levels of effects. These are classified according to the previously described graphtheoretical approach. There are experimental studies with models about sensory interactions of combined odors and combined noises (Berglund et al. 1987; Harssema 1987; Diamond and Rice; 1987; Miedema 1987), but only little research has been directed so far to the combination of noise and air pollution. One report (Berglund et al. 1975)


N

~- CO

27 oe©

NOISE

Fig. 3. Cortical DC shifts in the rat brains induced by 27-s acoustic stimulation (battle cries of rats) with and without CO exposure.

has clearly shown that no noise-odor interaction oc- curs on a sensory level (corresponding to our Type Ih independent action). The report suggested that interactions shown in a field situation would stem from non-sensory factors, e.g., attitudes. Turning to field studies in which noise and air pollution in their disturbing effect on people have been investigated, higher order interactions, like the types V and V1 (general interaction) can be found.

Some of these field studies show that annoyance is only weakly related to the physically measured levels of noise and air pollution but that interactions between residential quarters and annoyance exist. Strong correlations were also obtained between annoyance due to noise and that due to air pollution. One example, taken from Wanner et al. (1977) shows that the frequency of annoyance due to noise and air pollution is correlated by 0.78 and the intensity of annoyance due to noise and air pollution is correlated by 0.72.

Another example is taken from the Viennese study of annoyance due to environmental factors (Wiener

Fig. 4, Frequency of annoyance due to noise, odors, and exhaust gases as well as dusts, and the correlations between these differ-

ent environmental stressors.


Umwelterhebung 1984). As seen in Fig. 4, noise is the main factor to which annoyance is attributed (62%), followed by dust (45%) and odors (40%).

The correlations between the annoyance due to different environmental factors are very strong (all above 0.9). This might be due to the fact that the whole group of environmental stressors is highly interrelated or that the individuals being annoyed by one stressor (eg., noise) are sensitized to other stressors (eg., air pollution).

Hangartner (1987) reported a correlation for annoyance due to noise and automobile exhaust of 0.81 and concluded that individuals do not distinguish between these two environmental stressors and that the self-rating is an integrated measure of allinter- venin.g annoyance factors.

In conclusion, annoyance is an index of responses of humans to combinations of environmental stimuli, including noise and air pollution, in which the effects are always linked and all effects are of a combined type of general interaction (V and VI).

A c k n o w l e d g m e n t m T h e reported studies were supported by the Austrian Fonds zur F6rderung der wissenschaftlichen Forschung.

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