A health survey of granite workers in Finland: radiographic findings, respiratory function, hearing, electric sensory thresholds of the fingers and subjective symptoms.

AHLMAN, BACKMAN, A-L. and PARTANEN, T. A health survey of granite workers in Finland: Radiographic findings, respiratory function, hearing, electric sensory thresholds of the fingers and subjective symptoms. Scand j. work environ. health 1 (1975) 109-116. Results from a health survey of 777 granite workers, ex posed to quartz dust, noise and/or machine vibration, and 122 unexposed "controls" are reported. The survey included chest X-rays, pulmonary function tests, a hearing examination, the determination of the electric sensory thresholds of the fingers, and questionnaires on the subjective symptoms of the respiratory system and upper limbs. The exposed workers' radiographic findings (except for a 2.6 % rate of silicosis), respiratory functions, and sensory thresholds did not differ significantly from those of the controls. Granite drillers had a high prevalence of hearing defects. Respira tory symptoms were common among drillers and sandblasters, and subjective symptoms of the upper limbs due to vibration occurred among the granite dressing workers who used pneumatic hammers. Both primary and secondary measures of prevention are strongly recommended for the granite industry, primarily for quartz dust exposure and its health effects.

Expasure to quartz-oontaining dust is a well-known h~alth hazard in the granite industry, and most of the previous studies concerning the health hazards of granite work deal with the effects of granite and quartz dust, particularly silicosis (e.g., 1, 2, 4, 5, 6). However, recent changes in working methods and the introduction of new tools h(ltV~crea,tedaddi·tional health hazards, of which machine noise and vibration are considered the most ser1ous.
This report is the first in a series of reports concerning Finnish granite workers' exposure to dust, noise, and vibration and their health status, morbidity, dis-ability, and subjective opmiOns of exposure and health-.related matters. Specifically, results are reported here of a health screening offered to gran1te worikers;3 the screening was directed toward postulated effects of dust, noise, and v,ihration, namely, effects on the respiratory organs and hearing, as well as circula,tory, neurological, and other disturbances in the upper limbs.

SUBJECTS AND THEIR CLASSIFICATION
A mobile clinic visited 71 plants in the granite industry between 1970 and 1972. The plants were involved in quarrying, dressing, cutting, crushing, grinding, smoothing, polishing, loading, and transporting I!"ock, goranite pr,odiuctis .and byproducts of the stone processing. These 71 plants were selected from the total of approximately 270 granite pLants in the cOUIlitry so that their g,eogr,aphical distribution would correspond to that of the total. The total number of workers in the Finnish granite industry (tunnel and road construction workers excluded) amounts to approximately 2,100 workers. The number of wor.kers estimated to have worked in the selected 71 pLants at the time of the screening was 1,300, out of which 1,037 subjects attended the screening. The participation rate was thus about 80 0/0. 4 '!1he subjects were classified into 11 groups according to their questionnaire responses ·as to the kind of granite work they had done and for how Long. The groups were the following: Refining: 96 men who did mixed refining work, mainly crude shaping, cuttiIDg and dl'lessing. Owing to the mixed nature of the work, the exposures charaoterizing this group w.ere various degrees of dust, noise, and vibration. Minimuan exposure: 1 year.
Loading: 53 men whose predominant work in the granite industry was the dustexposed loading of .granite blocks or sand for transportation. Minimum exposure: 1 year.
Crushing and grinding: 76 men who crushed, grinded, sand sifted, or did related works involved in the processing of granite waJSte. Dust and nois'e were the predominant exposures. Minimum exposure: 1 year.
Quarrying: 91 men who worked in the quarries but had an otherwise poorly specified occupational history.
Drilling: 98 men whose predominant work was drilling and shotfiring granite rock. Minimum exposure: 1 year.
Transportation: 135 truck drivers who transported sand and oth·er for,ms of gran- 4 The reason why the participation rate is not exactly known is that the research team did not have the exact number of workers in the selected plants. In addition, the employers handled the sch~duling of. the screening in their respechve enterpnses. They had been asked to include every employee, but it is not known if they did. In open blasting the operator worked in a shed, and, if not properly protected with pe,rsooal protection equipment, he was directly exposed to granite dust and noise. A less danglerous mode of sandblasting was done by direating the sandblast from -outside a shed, which was equipped with ventilation for dust removal. Minimum exposure: 3 months.
"Control" group: 122 men employed in the granite industry at the time of the screening whose exposure to dust, noise, and vibr,ation had been, according to their own report, shorter than 3 months. Most of their working history consisted ,of work other than office work. A .total of 899 persons were included in the 11 gI10Ups. The remaining 138 were excluded for one of the following reasons: (a) insufficiently reported working history, (b) office work, (c) "confounding" exposure (e.g., mining), (d) sex (women were excluded because of their small number), (e) age (those under 15 and over 64 years of age were excluded for the same reason as the women).
The age distributions of the 11 groups can be found in table 1.

Screening procedure
The gr,anite workers were requested t,o fill out two quesHonna~res, one on respiratory symptoms and smoking habits (8) and one on different symptoms of the upper limbs (9). They were to bring the completed questiormaires to the mobile clinic where a nurse checked all the information and interviewed those men who used vibrating tools in their work. The screening procedure then followed: height and weight were recorded, two chest radiographs (antero-po,sterior and lateral) ta'ken, r,espiratory function tests (foroed vital capacity and I-second forced expkatory volume) made,5 and hearing checked. Also the electric sensory thresholds of the fingers of the 336 men who used vibrating tools were determined.

Health indicators
Two types of health indicators were considered when the results were evaluated. One type is categorized by the subjective symptoms obtained from the two ques- 5 Each subject made three expirations. The vital capacity values were determined as the percentage of the age-, sex-and heightstandardized normal values (3). The I-second expiratory volumes were computed as the percentage of the vital capacities. 4

Statistical methods
'I1he comparison of the health indicators between the ten exposed groups and the cont1"ol group was done in two ways according to the type of indicator. In the case of a yes-lno type of indicator, agestandardized prevalences were calculated for the exposed groups by using the age distribution of the controls as the standard. The standardization was made through the 15-to 64-year I1ange in 10-year age groups, except for the stone dressers whose youngest member was older than 24; in this group the prevalences were calculated and standardi:oed in the narrower range of 25 to 64 ye.ars. The difference of each standardized prevalence and the corresponding prevalence in the controls was tested for significance with Mantel and Haenszel's (7) method of comb~ning information from several 2 X 2 frequency tables. Estimates of "risk ratios" wer,e calculated by divid,ing the standardized prevalences by the prevalence in the control group. When dealing with health indicators of a continuous nature (respiratory functions), the effects of the diffe1"ent age struotures of the groups were eliminated by calculating the regression lines of each respiratory function variable with respect to age and then comparing the slopes of these lines to those of the cont1"ols. The slopes sho,wed the rate of decrease in the respiratory functions with increasing age. '"~.

Subjective respiratory symptoms
The prevalences of different respiratory symptoms were highest in the drilling, sandbla,sting, and refining groups (table  2). The drillers complained of coughs, phlegm production, runny noses, chest or throat inflammations, and the effects of weather on the chest; the age-,standardized prevalences of these symptoms were 1.5 to 2.8 times those of the controls. The sandblasters complained of phlegm production, ,runny nos1es, and inflammations of throat and chest ("significant" risk ratios 1.7-2.4). High prevalences of cough, 112 phlegm production, and inflammations were also noted in the refining group, and those for production of phlegm and inflammations in the dressing group. The quarrying group complained of inflammations, the truck drivers (tr,ansportation gr·oup) of coughs, and the granite saw operatiors of runny noses.

Subjective and objective symptoms and signs of the upper limbs
The prevalences of subjective symptoms in the upper limbs (table 3) were notably high in the dressing group, a large proportion of which had been usiJlg a pneumatic responding risk ratios. The latter are shown only if greater than unity at p < 0.05.  hammer for a considerable time. Drillers also oomplained of numb fingers in a significantly higher frequency than the contwls, while refiners reported whitening or circulatory disturhances in their fingers.
Of the 336 subjects who reported having been exposed to vibration, 322 estimated the time period from the onset of exposure to the fIrst appearance of their symptoms. The followtng median induction periods were obtained a) 5.4 years for refining, b) 4.2 years for drilling, and c) 7.4 years for dressing. In other words, symptoms developed the fastest in drillers and the slowest ,in dressers.
The same 322 wOl1kers also reported their opinions of what condition or conditions had caused their symptoms. The causing conditions, ranked according to the percentage of those who reported them as causes, were the following: (a) vibration itself (76 Ufo), (b) frost (37 Ufo), (c) working posture (18 Ufo), (d) long, uninterrupted working periods (6 Ufo), and (e) lack of varying work phases (5 Ufo).
The electric sensory threshold in the fingers was classified as a) normal, b) borderline, c) mildly deviant, or d) strongly deviant. The two latter categori~s were then combined, and the prevalences of deviant findings wel1e calculated and standardized for age in each occupal1;ional group. The standardized prevalence rates in the different groups of exposed workers ranged from 0 Ufo (crushing and grinding) to 25 Ufo (dressing); none differed significantly, however, from the prevalence in the contml ,gl'OUp (12 Ufo).

Radiographic findings
The age...,standardized prevalences of fibrosis of the lung in the eleven gmups were based on 100 X 100 antero-posterior and later,al chest rraJdi,og'raphs. The highest prevalences were noted among the dressing wmkers (6.7 Ufo), drillers (5.6 Ufo), and sandblasters (5.6 Ufo). According to the unpubliisihed ,r,esults of Ahlman et aL dressing, drilling, and sCllndblasting were also works in which high concentrations of qua,rtz dust were measured in the a,ir samples taken in the respiration region of the workers. The prevalences of fibrosis of the lung did not howelV.er differ significantly from that of the controls (0.8 Ufo). Noticeably lower rates were obtained for ref,ining (2.6 Ufo), loading (1.2 Ufo), crushing and grinding (2.8 Ufo), quarrying (0.9 0/0), sawing (1.3), smoothing and polishing (2.3 Ufo).
Silicosis was provisionally diagnosed in 20 granite workers from the chest radiographs. Three cases were formerly known, four were new and verified by full-sized chest radiogr,aphs after screening, eight turned out to be false positives, and five (1 = refining, 2 = loading, 3 = crushing and grinding, 4 = quarrying, 5 = drilling, 6 = transportation, 7 = dressing, 8 = sawing, 9 = smoothing and polishing, 10 = sandblasting, and 11 = controls) did not comply with th€ recommendation that their results be verified. The shor:test induction period (time from the onset of exposure to quartz dust to diagnosis) in the seven formerly known or freshly diagnosed cases of silicosis was 18 years, and the longest 38 years.

Respiratory function
Vital capacity (Ofo of age-, sex-and heightstandardized normal values) and forced expiratory volume (1.0 s; 0/0 of VC) were regressed aga-inst age for each group of woI'k€rs ( fig. 1 and 2). The slopes of th€ regression lines, indicating the ra.te of decrease with age, of the VC and FEV1.0 of the exposed groups did not differ significantly from the slopes of VC/age and FEVl.O/ag,e of the controls. Attention should b€ drawn to ,the fact that the vital capacity, although standardized for age, still showed a decreasing tendeney with increasing age in this analysis, even for the controls.

Hearing defects
General deviations from normal hearing (either insignificant, slight or significant) were noted in 50 Ofo of the controls (table   4). The corresponding prevalences in the exposed groups varied between 39 and 61 Ofo' The latter figure was observed in the drillers, and it diff€red from the reference value (controls) at p < 0.05.
The prevalences of hearing injury, caused by occupation, ranged from 3 to 58 %, whiJ,e the f.igur,e for controls was 44 %. No expos.ed group showed a significantly highelr pl1eval,ence than that of the controls.

DISCUSSION
The picture of granite workers' health which emerges from the results is incomplete, if interpreted in terms of the effects of exposure. There are two mutually interlocking reasons: a) the crosssectional nature of screening made it impossible to estimate incidence rates and other risk measures derived from them; instead prevalence rates, specific for the time of screening, were calculated; b) only workers employed in the granite industry at the time of the screening were included; Table 4. Age-standardized prevalences of hearing abnormalities and the corresponding risk ratios. The latter are shown only if greater than unity at p < 0.05.  this I1esulted in the exclusion of those exposed who had left the industry for various reasons, some of which have been related to health (death, incapacity for WOI1k, shift for health reasons to work without exposures typical to the gifanite industry). A longitudinal, retrospective cohort study concerning mortality and incidence of disability of the granite workers will be reported in a later article of this series. The outcome of a health screening also depends on the sensitiv,ity and the specificity of the screening tes'tsapplied. In the present study subjective symptoms proved to be more sensitive indicators of slight health disturbances than the clinical tests. Furthermore, in the unpublished results of Ahlman et al. dust, noise, and v1bration measurements, taken in different w.ork places, confirmed the questionnaire resuLts.
According to the results the present wOI1king met,hodis of the granite indus'try se,em to increase the risk of respiratory illness, hearing loss, and vibration disease. The highest health risks were noted in the groups occupied with drilling, dressing, refining, and sandblasting.
Respir,a,tory symptoms were fI1equent in the drilling, sandblasting, and refining groups. Some of the symptoms (for instance symptoms of common cold and chest and thro<lJt infllammations) may ol'iginate from weather conditions, since many wonk phases take place out-of-doo'rs. Another contributing factor may well have been the per.son-1o-person spread of infection.
The radiographic findings show.ed the highest prevalences of fibrosis of the lung among the dressing workers, drillers, and sandblasters. Accord~ng to the unpublished results of Ahlman et al. dressing, drilling, and sandblasting were also works in which high ooncentrations of quartz dust were measured in the air samples taken in the respiJr.ation regli.on of the workers. The prevalences of fibrosis of the lung did not however differ significantly from that of the controls.
Silioosis Wlas verified in seven cases. The verif,ied cases derived from the dressing, drilling, refJning, or qua,rrying group.
Dressing workers, drillers, and refiners were the most hkely to be affected by vibration. 'Ilhe median exposure time bef,ore the vibration symptoms set in ranged from 4 to 7 years. Symptoms developed the fastest in dl'illers and the sLowest in dressers. In measuring the electric sensory threshold in the fingers, we found the hiJghest pI1evalence of deviant findings in the dressing gl'OUp; the difference d1d not, however, reach the adopted significance level.
In evaluating the results, one must bear in mind thai many of ,the subjects in the control group had been exposed to the same health hazardis as the other groups, although th,eir exposure time was very ShON. The eventual effects ill exposure must therefore be considered, especially in r,espect to the audiometric findings. According to the audiometric findings, half of the control group showed devia-Hons from normal. The prevalence of noise-induced hear.i.ng loss was as high as 44 Ofo among the controls. This f.igure indicates ithai there was a possibility that the hearing of the control group was affected in spite of their short exposure time.
In the Finnish granite industry little attention has been paid to preventive measures, and the working conditions a'l"e, for the most part, unsatisfactory. It is obvious thai primary prevention, including dust control and noise and vibration abatement, must be begun on the technical level. Dust exposure should be monitored regularly with air sampling and analysis in the whole granite industry. More attention should aliso be directed toward the workers themselves. I'll the preemployment health examination, as weIll as in the annual checkups, special attention should be paid to respiratory, cireulatory, and auditory conditions. Subjective symptoms would especially help to reveal slight respiratory and circulatory disturbances. Hea,lth education ought to be implemented also to promote the importance of warm clothing and the aggravating effect of smoking when one works with vibratiI}.g tools. In addition the usefulness of personal protection devices should be emphasized. Shortening the worlci.ng periods should be seriously considered for persons using vibrating '1Jo.ols.

ACKNOWLEDGMENTS
This study has been financially supported by the Social Insurance Institution of Finland.