Neurobehavioural effects ofrepeated occupational …questionnaire study in which the painters were found to have raised scores in an English language version of a screening questionnaire'6

British Journal of Industrial Medicine 1985;42:291-300

Neurobehavioural effects of repeated occupationalexposure to toluene and paint solventsNICOLA CHERRY, HELEN HUTCHINS, T PACE, AND H A WALDRON

From the TUC Centenary Institute of Occupational Health, London School of Hygiene and TropicalMedicine, London WC1E 7HT, UK

ABSTRACT In studies of two workforces 44 men exposed to paint solvents and 52 men workingwith toluene were compared with age matched comparison groups of non-exposed workers.Scores on a series of performance tests were examined, the solvent exposed in each studyfunctioning less well than their comparison group. The apparent deficit among the paint exposedworkers was substantial, but this was reduced after allowance for estimated intellectual capacity.No deficit was apparent on rematching with a second comparison group of more appropriatemeasured capacity. No evidence was found of impaired nerve conduction in the ulnar or mediannerves, and few clinical signs of neurological damage were apparent. Nevertheless, in an associ-ated inquiry of neuropsychological symptoms among 236 painters and 128 non-exposed workersa highly significant excess of symptoms was found among those exposed to paint solvents.

Evidence for nervous system effects of long termexposure to organic solvents comes from severalsources. Firstly, clinical cases with disabilities attri-buted to solvent exposure have been intensivelystudied and a typical clinical pattern of solventinduced changes described.'-6 Secondly, there havebeen several studies of the peripheral nervous sys-tem changes associated with exposure to specificsolvents or solvent mixtures.7 Thirdly, an increasedrate of disabling psychiatric illness has beenreported in some epidemiological studies carried outin Scandinavia.8-" Finally, several cross sectionalstudies of signs and symptoms among apparentlyhealthy workers still in employment have been car-ried out, neurophysiological and behavioural scoresamong the exposed men being compared with thosein an unexposed referent group (see, for example,refs 12-14).The present paper reports two cross sectional

studies, using methods previously described.'5 Instudy A men were exposed to a mixture of paintsolvents in a naval dockyard. In study B exposurewas to toluene in the rubber shed of a companymanufacturing mineral fibre products.

Received 26 March 1984Accepted 12 October 1984

Material and methods

SUBJECTSStudy A-The men included in study A worked in alarge dockyard in the south of England, either aspainters or joiners. All had taken part in an earlierquestionnaire study in which the painters werefound to have raised scores in an English languageversion of a screening questionnaire'6 for neuro-psychological symptoms developed in Sweden (seeappendix). Sixty painters (25% of the originalgroup) were selected at random and invited to takepart in a further study. The selected men, allexposed to paint solvents (see below), were indi-vidually matched with a joiner working at the dock-yard, those whose tasks exposed them to glues beingexcluded from the referent group. Matching was onthe basis of age (±+3 years), alcohol consumption(regularity of drinking), and, in so far as possible, onthe highest levels of examination passed. This pro-cedure resulted in exposed and referent groups,each of 44 men, that were similar in mean age (pain-ters 41-0 years (SD 12-4); joiners 40-8 years (SD12- 1)) and alcohol consumption, but among thepainters, a lower proportion had passed publicexaminations at school or college than had thejoiners.Study B-The men included in study B worked at

an asbestos products factory in a process makingrubberised asbestos matting that necessitated a high

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exposure to toluene (see below). The aim of thestudy was to investigate the effects of long termexposure to the solvent, and initially, of the 102 menon the day shift, only the 66 who had worked in therubber shed for five years or more were invited totake part. Nevertheless, 14 of the 36 men with shor-ter exposure expressed an interest in undergoing thetests; the relation of such self-selection to the meas-ures used in this study is unknown, but it wasthought important that no one should be discour-aged, and scores for these 14 volunteers with shorterexposure are included in the analyses reported here.Among the initial group of 66 with longer expos-

ure, 17 did not wish to take part. This was a higherproportion of non-participants than would normallybe accepted, but because of other circumstances inthe factory, it was thought inadvisable to press morestrongly for participation. It was possible, however,to compare the non-participants and participants onage, duration of exposure, sickness absence, andaccident records. The two groups did not differsignificantly (p < 0.05) on any of these factors.Each of the 63 subjects finally included (49 long

term exposed and 14 volunteers) was individuallymatched with a man not exposed to solvents andemployed elsewhere in the factory. Matching was

carried out on age ( + 3 years), race (white or Asian)and duration of employment (+ 1 year). Fifty ninewell matched pairs were obtained, 52 white and 7Asian. The mean age of the exposed men was 41-8years (SD 10.4) and that of the referents, 41-7 years(SD 10.5). Although prior matching on the basis ofeducational level and alcohol consumption was notpossible, examination of questionnaire data showedno difference between the groups on these factors,nor on the taking of medicines or sickness absence.

Exposures

STUDY ATable 1 shows the constituents of the most widelyused paints in the dockyard. The solvents in thepaints included white spirit, trichloroethylene,dichloromethane, methyl n-butyl ketone, and

Cherry, Hutchins, Pace, and Waldronn-butanol. The exact composition of the paints var-ied from one manufacturer to another and betweenbatches supplied by the same manufacturer. Duringthe course of his work, a painter might work in theopen air with relatively low exposure to paint fumesbut also in confined spaces, such as ships' tanks,where exposures would be considerably higher. Acomprehensive survey to measure individual levelsof exposure in the various jobs undertaken by thepainters has not been carried out; Kuo, however,studied eight painters over two days while workingin ships' accommodation and bilges.'7 The meantime weighted average exposure to paint solventswhich she found is presented as a guide in table 2.Owing to the varied nature of the painters' work, itwas not possible to calculate an index of exposurefor each of the men in the study. Nevertheless, thetotal years working as a painter at the dockyard isused below as a crude index of cumulative exposure;the mean duration of exposure was 11-7 years.

STUDY BTable 3 shows a summary of measured atmosphericlevels of toluene in the rubber shed of the asbestosfactory. Before 1976, the levels were at least 300parts per million (ppm) on all the machines in theshed and background levels were between 100 and200 ppm. During the late 1970s, levels fell in allparts of the shed and by December 1981, when thestudy took place, toluene levels were between 100and 200 ppm on two of the processes, the spikemixers and calenders, and below 100 ppm (thethreshold limit value) in other parts of the shed. Anindividual index of exposure was computed for eachman, each period in years in a given job beingweighted by the estimate, shown in table 3, oftoluene exposure at that time.

CLINICAL EXAMINATION AND TESTINGPROCEDUREThe same protocol was followed in both studies.Each man was asked to complete a questionnaire athome, before the day of his examination, and to givedetails of job history, symptoms, personal habits

Table 1 Constituents ofpaints and other materials used at the dockyard

Paint Solvents Site of use

White interior ( Ships' accommodationBitumastic (coal black) White spirit solvent with maximum aromatic content of 20% Ships' tanksYellow zinc chromate PPrimerEpinamel Methyl n-butyl ketone, n-butanol, xylol, butyl oxitol, solvesso or Ships' tanks

cellosolveChlorinated rubber Trimethyl benzene, xylol, shellsol, or naptha Machinery spacesEpoxy tank coating (Tanclene, Xylol, trimethyl benzene, white spirit, cellosolve, n-butanol diacetone Ships' tanks

coal tar epoxy) alcoholPaint stipper Trichloroethylene or dichloromethane Paint removalFrench polish White spirit Varnished surfaces



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Neurobehavioural effects of repeated occupational exposure to toluene and paint solvents

Table 2 Mean levels ofexposure to organic solvents for eight painters on two working days in September 1980 (afterKuo17)

Paint Principal solvent Mean time weighted TLV (mg/m3) No ofpaintersaverage (mg/r3)

White interior White spirit 577-4 525-0 4Paint stripper Dichloromethane 214-7 700-0 1Chlorinated rubber White spirit 124-6 525-0 3

Table 3 Sampled levels oftoluene by job and by year in the rubber shed

Job Pre-

1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981

Spike mixer 6 6 6 6 6 6 3 3 3 3 2 2Other mixer - - - - 4 4 2 2 2 2 2 1Surface weigher 6 6 6 6 6 6 6 6 2 2 2 1Body weigher 6 6 4 4 4 4 3 2 2 2 2 1Calendar operator 4 4 4 4 4 4 4 3 3 3 2 2General background 2 2 2 2 2 2 2 2 1 1 1 1

1 = 0-100 ppm; 2 = 100-200 ppm; 3 = 200-300 ppm; 4 = 300-400 ppm; 5 = 400-500 ppm; 6 = > 500 ppm.

(smoking, drinking), and examinations passed.When he reported to the medical centre at his placeof work on the day of testing he was clinicallyexamined, with particular attention being given tothe nervous system. The physician responsible forthe examination then checked the medical andexposure history with the worker, the rest of theresearch team, who were to conduct the furthertests, not being informed of the exposure status("exposed" or " comparison"').The behavioural testing procedure outlined below

was carried out immediately after the clinicalexamination. Each man was tested alone in a quietroom away from the normal work of the medicalcentre. The procedure lasted from 30 to 50 minutes,depending on the capacities of the worker. The finalstage of the assessment was the measurement ofnerve conduction velocities in the ulnar and mediannerves of the right arm using a Medelec MS7. Motorand sensory components of the nerves were meas-ured (the method is described more fully else-where'8).

BEHAVIOURAL TESTSThe series of behavioural tests was identical in thetwo studies. The tests are described briefly below;they have been described in more detail elsewheretogether with the details of the scoring procedure.9The tests used have been shown to be sensitive indifferentiating patients with minor brain damagefrom other groups of neurological patients at arehabilitation centre.20

Dotting tests-The test session started with a sim-ple pencil and paper dotting test, in which the manwas asked to place dots, as rapidly as possible, oneither side of two parallel lines 10-5 cm apart during

the space of 10 seconds. The total number of dotswas recorded. The man then repeated the test, for afurther period of 10 seconds, the task at this stagebeing to make dots inside two circles of 1 cm radius,the centres of the circles being 10-5 cm apart. Thetotal number of dots within the circles was counted.

Trail making tests-The test2' required the subjectto join 25 circles with a pencil mark. In the first partof the test the circles contained the numbers from 1to 25 and the subject was required to join the circlesin the correct numerical order. In the second part ofthe test 13 numbers (1-13) and 12 letters (A-L)were shown in the circles and the subject wasrequired to join alternate numbers and letters (1-A-2-B... .). The time taken to complete each serieswas recorded.

Visual search test-In this test (adapted fromGoldstein et a122) the subject was presented with aseries of checkerboard grids consisting of 81 blackand white squares. Each white square was dividedinto 25 smaller squares, two of which were filled inblack. The configuration and arrangement of thelarge white squares was constant with the exceptionof the centre square which varied from grid to grid.The subject' s task was to search for the white squarein the grid which was identical with the centresquare. Twelve timed trials were given and the meantime calculated.

Digit symbol test23-The subject was required tosubstitute symbols for the numbers 1-9, making asmany substitutes as possible in 90 seconds. The totalnumber of correct substitutions was recorded.Block design test23 -The subject was presented

with nine blocks having two red sides, two whitesides, and two sides diagonally divided into red andwhite halves. The blocks were used to construct a

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series of ten designs that were presented on cards inorder of increasing difficulty. The test was scoredaccording to the highest ranking design successfullycompleted and the time taken to complete each trial.Grooved pegboard test-For this test, apparatus

supplied by Lafayette Instrument Company wasused. The subject placed 25 key shaped pegs intoholes that had the flange of the key arranged in ran-dom order. The time to complete the task wasmeasured with the subject using first his preferredand then his non-preferred hand.Simple unprepared reaction time24-The test

measured the subject's mean speed of response tosome 80 signals presented at random intervals of1-10 seconds for a period of ten minutes; the testused here was modified to mask feedback and soeliminate any differential motivational effect thismight have provided for the exposed and non-exposed groups.Memory test25-The subject was presented with a

list of 20 animal names which he was asked to recall.He was reminded of those that he had forgotten andthis procedure was carried out for five trials. Fromthe results it was possible to calculate the number ofitems recalled on each of the five trials, the totalover the five trials, the number of long term storeafter four trials and the number of intrusions-thatis, animal names-that were not on the original list.Reading test-The final test to be administered

was the National Adult Reading Test,26 originallydesigned to assess the level of intellectual attain-ment before the onset of damage to the centralnervous system. The subject was asked to read a listof 50 words with irregular pronunciation that werepresented in order of increasing difficulty, and hewas scored according to the number that he pro-nounced correctly. The fifty words in the test wereselected in such a way that they cannot be pro-nounced by applying the normal grapheme-phoneme and stress rules of the English languageand may be read correctly only if previously knownto the reader. This test is resistant to the effects ofrecent central nervous system damage.

Results

CLINICAL EXAMINATIONIn nine of the painters and five of the joiners someloss of vibration was noted in the arms or legs. Thisdifference was entirely accounted for by differencesin the use of vibrating tools. In study B vibration lossin the legs was noted in 11 of the exposed and five ofthe non-exposed men. This result is suggestive ofsome effect of the solvent but was not statisticallysignificant.

Cherry, Hutchins, Pace, and Waldron

NEUROPHYSIOLOGICAL MEASURESUsing a matched pair t test, none of theneurophysiological measures, motor conductionvelocity, sensory conduction velocity, amplitude,and distal latency in the ulnar and median nervesdiffered significantly between either group of sol-vent workers and their controls. The largest differ-ence between the groups was for sensory conductionvelocity in the ulnar nerves of the workers exposedto toluene and their controls; however, this differ-ence was only 1-5 m/sec and was not significant atthe 5% level.

BEHAVIOURAL TESTSMatched pair t tests were carried out to compare theperformance of the exposed men with their com-parison group.Study A-Table 4 shows the results for this com-

parison of the scores of men exposed to paint sol-vents and their non-exposed referent group. Thepainters had a lower mean score on the reading test;this is discussed in more detail below. They also per-formed less well on the alternating part of the trailmaking test, with a longer mean correct responsetime on the visual search and a lower mean score onthe block design test. They were also slower on thegrooved pegboard test with each hand, and theiroverall mean reaction time was slower than the join-ers. In the memory test, the painters recalled feweritems than the joiners over five trials, they had feweritems in long term store on the fourth trial, andmade more intrusions during the test. All these dif-ferences were statistically significant (p < 0.05).Study B-The referent group once again had a

higher score on the reading test than the exposedgroup (see table 5), this difference being unlikely tohave arisen by chance (p < 0.01). Differences be-tween groups on the other tests did not reach statis-tical significance, but scores on four tests, the trailmaking test (alternating series), the visual search,the pegboard test (with either hand), and the numberof intrusions on the memory test (instrusions) sug-gested, using a one tailed approach that may bemore appropriate given the hypothesis under test,that the exposed group performed less well. It maybe noted that scores on all tests, except for the reac-tion time, were somewhat worse for the exposedthan for the non-exposed workers.

CUMULATIVE EXPOSURE AND PERFORMANCEIn a working population age and exposure measuresbased on duration of employment will be positivelycorrelated. In a study of behavioural effects in whichtest scores decline with age assessment of the effectsof cumulative exposure may be interpreted onlyafter full allowance for the effects of aging, prefer-



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Table 4 Mean performance ofpainters and their controls

Exposed

Age (years) x 41-8SD 12-5N 44

Reading score x 19-8*SD 8-3

Dotting test:Lines x 31-7*

SD 9-8Circles x 24-5*

SD 5-4Trail making test:

Numerical series (sec) x 36-3*SD 15-7

Alternating series (sec) x 93-8*SD 36-6

Visual search:Mean for 12 trials (sec) x 21-3*

SD 8-1Digit symbol:

Overall score x 44-1*SD 11.1

Block design:Overall score x 33-6*

SD 9-1Grooved pegboard test: -

Preferred hand (sec) x 76-0*SD 13-5

Non-prefeffed hand x 80-2*SD 13-0

Simple reaction time:Overall mean (ms) x 369-0*

SD 115-5Buschke test:

Recall (5 trials) x 12-7*SD 3-6

Long term store x 11-1*(4 trials) SD 4 0Intrusions x 5.6*

SD 4-3

*Group with worse performance.

ably estimated in the non-exposed population. Inthe present study the years of total exposure, or, fortoluene, the index of cumulative exposure, wererelated to performance on the behavioural tests.These analyses, which were restricted to men withoccupational exposure, evaluated the contributionof exposure after allowance for age.

Study A-Having allowed for age, years of expos-ure appeared to have a greater effect on the groovedpegboard test (with the non-preferred hand) than onany of the other measures; painters with long expos-ures took longer to complete this task than men ofthe same age with shorter exposures. The level ofstatistical significance, however, was not high (5%),and with 13 tests being carried out one such resultmight reasonably be expected to have arisen bychance.

Study B-After allowance for age, the weightedcumulative index described above was not related toany of the behavioural test scores among the men

exposed to toluene.

ADJUSTMENT FOR READING SCOREIn both study A and study B the exposed menobtained lower scores than their comparison groupon the reading test. This test had been designed toassess level of verbal attainment (and hence, indi-rectly, intellectual capacity) before the onset of anydamage to the central nervous system that mighthave resulted from exposure to solvents. The resultson this test suggested that the comparison groupswere of higher ability than the exposed men withwhom they had been matched. Because of the corre-lation between the reading test scores and the per-formance tests found even in the non-exposed menit was necessary to allow for these differences inverbal attainment in assessing the effects of expos-ure on performance. Two approaches were adopted.

Statistical adjustment for reading scores

Study A-A multiple regression analysis was car-

ried out in which the effects of job (exposed to paintsolvents or not) were assessed after allowance for

295

t value

0-09

3-81

Probability

NS

<0-001

0-81

0-79

NS

NS

1-78

2-26

Control

41-812-14425-97-8

33-36-9

25-34-3

31-78-8

83-030-7

18-75.3

46-89.5

38-87-3

70-710-872-911-7

318-673.514-53-1

12-83.93-64-2

NS

<0-05

2-02

1-31

<0-05

3-01

NS

<0-01

2-29

3-06

<0-05

<0-01

2-23 <0-05

2-21

2-02

2-75

<0-05

<0-05

<0-01



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Table 5 Mean performance oftoluene workers and their controls, Asian workers omitted

Exposed Control t value Probability

Age (years) x 42-0 41-9 0-59 NSSD 10-5 10-7N 52 52

Reading score x 17-6* 21-7 2-79 <0-01SD 9-5 8-6

Dotting test:Lines x 35-0 34-4* 0-37 NS

SD 8-0 7-8Circles x 25-7 24-9* 0-91 NS

SD 4-8 4.5Trail making test:

Numerical series (sec) x 35-2* 32-7 0-85 NSSD 17-5 10-6

Alternating series (sec) x 96-0* 79 5 1-93 NSSD 49-0 25-9

Visual search:Mean for 12 trials (sec) x 22-8* 20 5 1-97 NS

SD 7-1 5-1Digit symbol:

Overall score x 42-1* 45-7 1-52 NSSD 12-8 9-1

Block design:Overall score x 31-2* 34-0 1-63 NS

SD 9-2 7-8Grooved pegboard test: -

Preferred hand (sec) x 80.4* 75 2 1-74 NSSD 19-4 10-9

Non-preferred hand x 85.5* 79.5 1 94 NSSD 19-0 12-0

Simple reaction time:Overall mean (ms) x 321 1 328-6* 0 56 NS

SD 68-6 68-6Buschke test:

Recall (5 trials) x 12-7* 13-5 1-50 NSSD 3-0 3-2

Long term store x 10-7* 11-7 1 46 NS(4 trials) SD 3-1 3-5Intrusions x 5-9* 4-1 1-90 NS

SD 4-5 4-6


ability, as measured by the reading test. Scores onfour of the performance tests were found to relate(p < 0.05) to the type of job (exposed or not) evenafter this statistical adjustment. These were blockdesign (total score), pegboard test (with non-preferred hand), reaction time (mean), and memorytest (number of intrusions).Study B-A similar analysis was carried out on

the scores of the men exposed to toluene and theircomparison group. As before, no significant relationwas found between exposure group and test score.The mathematical model used in this adjustmentdoes not allow for measurement error associatedwith the reading test. Such error may result in biasedadjustment when the population means of the twosamples differ,27 inclusion of the test score adjustinginadequately for the "true" underlying effect ofintellectual capacity. This bias does not arise if thesamples are drawn from populations with similarlydistributed values of the covariate. An opportunityto investigate the effects of paint solvents withoutthis source of bias arises here from the similarity ofthe reading test scores in the comparison group in

study B and the exposed group in study A. Themean and standard deviations on age and readingscore for the men recruited from these populationsare shown in table 6; no difference in reading scoreis apparent. It was decided to reanalyse the datausing the unexposed group from study B as a com-parison group for study A. It seemed that thisapproach would avoid the possible statistical biasassociated with measurement error in the readingtest; however, other biases resulting from differ-ences in the testing environment and study popula-tions may have been introduced in using this com-parison group.

Table 6 Mean age and reading score of48 painters and 57non-exposed white workers at the rubber factory

Painters Non-exposed t value Probability

Age(years) x 41-7 39-9 0-97 NS

SD 12-0 14-0Reading -

score x 19-9 20 5 0-46 NS.SD 8-1 10-0

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Redefinition of the comparison group for study AThe painters in study A were individually rematchedon age (+ 3 years) and reading score (+ 3 points)with non-exposed white workers from study B.Thirty four well matched pairs were obtained. Acomparison of test scores for these pairs is shown intable 7. On only one test, reaction time, is the differ-ence between groups sufficiently large to suggest asystematic effect.

Discussion

The studies reported here have shown few effectsthat may be attributed to solvent exposure. A slightexcess of minor peripheral nervous system deficitswas noted in the clinical examination in bothexposed groups but cannot with certainty be attri-buted to solvent exposure. No difference of impor-tance was found on the limited range ofneurophysiological measures of peripheral nervoussystem function.On the performance tests, men in exposed jobs,

particularly the dockyard workers exposed to paint

solvents, appeared to do appreciably less well thantheir comparison group; however, having carriedout the best available matching for reading ability(as an estimate of intellectual capacity), only thereaction time test suggested any deficit in perfor-mance among the painters. The workers exposed totoluene seemed to perform somewhat less well thantheir comparison group, but the statistical uncer-tainty associated with these results was such as toprevent any firm conclusion of damage. The relationof cumulative exposure to performance is alsounremarkable, no relation being found for thetoluene workers and only one, possibly chance,effect being related to duration of exposure amongthe men working with paint solvents. These resultsdo not suggest any widespread subclinical changeresulting from occupational exposure to eithertoluene or to the mixtures of paint solvents used inthe dockyard chosen for the investigation.The negative findings in the clinical and

neurophysiological examinations do not requirelengthy discussion; although in at least one study'3paint solvents have been reported as affecting nerve

Table 7 Mean performance ofpainters and toluene factory controls

Exposed

Age (years) x 42-7SD 11-8N 34

Reading score x 20-4*SD 7-6

Dotting test:Lines x 31-8*

SD 9-8Circles x 25-1

SD 5-7Trail making test:

Numerical series (sec) x 35-8*SD 15-2

Alternating series (sec) x 93-3*SD 36 5

Visual search:Mean for 12 trials (sec) x 20-6

SD 8-3Digit symbol:

Overall score x 45-0SD 10-7

Block design:Overall score x 34-7

SD 8-6Grooved pegboard test: -

Preferred hand (sec) x 75-8SD 12-6

Non-preferred hand x 80.0*SD 11-9

Simple reaction time:Overall mean (ms) x 380-2*

SD 125-5Buschke test:

Recall (5 trials) x 12-9SD 3-6

Long term store x 11.1*(4 trials) SD 4 0Intrusions x 5-7*

SD 3-9


Control

42-410-53420-68-4

34-78-2

24-7*4-6

33-410-880-225 9

20-8*4.7

45-09-5

33-2*8-0

76-3*12-279-713-2

331-374-5

12-93-4

11-33.54-55-2

t value

0-82

Probability

NS

0-47 NS

1-32

0-32

NS

NS

0-80

1-47

NS

NS

0-10 NS

0.01 NS

0-88 NS

0-18

0-11

NS

NS

1-97 NS

0.00

0-20

1-07

NS

NS

NS

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conduction, the findings for toluene are inconclusive(see for example, Cavanagh28). More sensitivemethods of investigation, however, might have beenable to detect minimal changes in function in theperipheral nervous system that were not apparentwith those adopted here. The failure to find a rela-tion between duration of exposure and performancedeficit is consistent with earlier studies; it is to benoted, however, that a repeated failure to demon-strate this relation must throw some doubt on thehypothesis that cumulative long term damage resultsas exposure is extended. Of greater interest, how-ever, is the absence of subclinical deficits in perfor-mance tests. This finding is at odds with many of thepublished studies of workers exposed to the groupsof solvents investigated here.The studies reporting such deficits were carefully

carried out and fully reported. For example,Arlien-Soborg et al and Hane and her colleaguesreported that painters were significantly impaired ontests of memory, reaction time, psychomotor co-ordination, and concept formation.' 12 In two otherScandinavian studies of car painters exposed totoluene Elofsson et al found that the exposed menwere significantly worse on tests of memory, percep-tual speed, reaction time, and manual dexterity bycomparison with a non-exposed referent group'3whereas Hanninen found exposed men to beimpaired on measures of memory, psychomotorco-ordination and non-verbal skills.'4 Such differ-ences in findings between these studies and thosereported here do not seem reasonably attributableeither to absolute levels of exposure (the workersinvestigated by Hanninen, for example, beingexposed to a mean concentration of only 31 ppm oftoluene) or, in our view, to synergistic effects thatmay be hypothesised to result from solvent mix-tures. While perhaps the inclusion of volunteers instudy B and the somewhat low rate of participationin both studies may have reduced the power of theinvestigation, it is nevertheless unexpected in thelight of the results of other studies, that no substan-tial effect of solvents is apparent.

In interpreting the lack of consistency betweenthe final results (table 7) of the present study andpublished accounts of others of similar design, itmay be appropriate to consider the conclusions thatmight have been drawn (from table 5) if there hadnot, by chance, been the possibility of carrying outan alternative adjustment for pre-exposure intellec-tual capacity. Without this, the poorer performanceof the solvent workers might have been more readilyattributed to solvent exposure. The methodologyadopted in this and in previously published crosssectional studies is subject to the distorting effects ofconfounding factors and may be of little use in inves-


tigating causal relation unless it can be shown thatplausible alternative explanation may be rejected. Inthe present study effects apparently attributable tosolvent exposure disappear with rematching; thisfinding puts in doubt the causality of the previouslyshown relation between exposure to paints and per-formance, and permits no firm conclusion as to theexistence of solvent induced deficit in the popula-tions investigated in the two studies reported here.

Appendix

PRELIMINARY QUESTIONNAIRE STUDY OFNEUROPSYCHOLOGICAL SYMPTOMS AMONGDOCKYARD PAINTERSIn June and July 1980 an English language versionof the screening questionnaire for solvent workersdevised by Hogstedt et a129 was administered to 236painters and 128 joiners working in a naval dock-yard. All men shown as employed as a painter orjoiner on the payroll on 2 May 1980 wereapproached to take part in the study but co-operation was voluntary. The sample completing thequestionnaire represented 84% of painters and 73%of joiners. To investigate the representativeness ofthe participants a comparison was made of age andsickness absence records for the participants andnon-participants. No significant difference wasfound on age, spells of absence, or total days ofcertified or uncertified sickness. Among those whotook part in the study, no difference was found be-tween painters and joiners on age (painters meanage 40 9 years, joiners 42-7 years), marital status,cigarette smoking, medication, or reported alcoholintake. The joiners, however, had passedsignificantly more examinations at school or collegethan had the painters.The questionnaire used was slightly modified from

the English version published by Hogstedt and hiscolleagues, the wording of questions being adaptedto more common English usage. The form of thequestionnaire was, however, the same, 15 questionson solvent related symptoms and one question act-ing as a detector item for over reporting. In thisquestionnaire the subject is required to reportwhether recently (over the past few weeks) he hasexperienced each symptom.The questionnaire was administered to the pain-

ters and joiners by one of the authors (TP) or by amember of the nursing staff at the dockyard. Groupsof between six and 22 men completed the question-naire at any one time in a room set aside for thesurvey. The administrators completed the question-naire on behalf of 17 men who were unable to do sothemselves. The questionnaire responses of the



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seven men who omitted answers to two or morequestions were excluded from the analysis.The responses of the painters and joiners were

compared for both individual questions and for thetotal of positive replies. The mean number of posi-tive responses was significantly higher (p < 0.01) forthe painters (mean 3-7, SD 3.5) than for the joiners(mean 2-6, SD 3.2), the painters being more likelyto report each symptom. The four individual ques-tions with a significantly higher response by thepainters are shown in table 8. Using the thresholdscores suggested by Hogstedt et al to identify casesfor referral to a physician (four or more symptomsfor workers aged 27 or under and six or more forolder workers), the number of "cases" among thepainters and joiners was computed. Sixty of thepainters were identified as "cases" compared with15 of the joiners, a highly significant difference(table 9).

Table 8 Numbers ofpainters and joiners respondingpositively to four items on the solvent questionnaire

Painters Joiners X2 p

Do you often havepainful tingling in 60 13 11-22 <0-001your hands or feet? (25-9%) (10.3%)

Do you often feelirritated for no 79 29 4-21 <0 05particular reason? (34-1%) (23.0%)

Do you often feeldepressed for no 68 24 3-98 <0-05particular reason? (29-3%) (19-0%)

Do you often havedifficulty 62 20 4-78 <0-05concentrating? (26-8%) (16-0%)

Table 9 Number ofcases defined by the solventquestionnaire

Painters Joiners

Non-case 170 112(73-9%) (88-2%)

Case 60 15(26-1%) (11-8%)X2 (corrected) = 9-21, p <0-01

No consistent relation was found between educa-tional level and symptom reporting, and the differ-ence between groups shown in table 2 could not beattributed to the reported difference on this factor.The men taking part in the study could not be effec-tively blinded, however, as the hypothesis under testand the possibility of reporting bias could not beruled out. In order to investigate more fully the pos-

sibility of solvent effects among the painters, thefollow up study reported above was devised.

These studies were supported by a grant from theColt Foundation. We would like to express our

appreciation of this funding and also the co-operation and help provided by the workers andmedical services concerned. Parts of the workreported here have been presented in theses forhigher degrees of the University of London.

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Documents

Neurobehavioural effects ofrepeated occupational …questionnaire study in which the painters were found to have raised scores in an English language version of a screening questionnaire'6