Document 2jEN2j6j4EpnGeeLLzwz1Nbbp

Int Arch Occup Environ Health (1989) 61:527-541 International Archives of Occupational*** Environmental Health Springer-Verlag 1989 Health hazards from fine asbestos dusts An analysis of 70656 occupational preventive medical investigations from 1973 to the end of 1986 H.J.Raithel, D.Weltle, H.Bohlig, and H. Valentin Institut fur Arbeits- und Sozial-Medizin und Poliklinik fur Berufskrankheiten der Universitat Erlangen-Nurnberg, Schillerstrafie 25/29, D-8520 Erlangen, Federal Republic of Germany Summary. For the period from 1973 to the end of 1986, 70656 data sets on occupational preventive medical examinations in employees exposed occupa tionally to asbestos dust (G 1.2) were made available to us by the Central Registry for Employees Exposed to Asbestos Dust (ZAS). On the basis of this data, an analysis of asbestosis risk was to be made in relation to specific areas of work, taking into consideration the beginning and duration of exposure. Proceedings for declaratory appraisal in accordance with occupational disease no. 4103 were instituted in 1760 cases in the re port period. In accordance with the character of the available data, the X-ray findings in the lungs were available from the persons investigated as parameters of possible asbestosis risk on the basis of coding con sistent with the International Pneumoconiosis Clas sification (ILO U/C 1971 and/or ILO 1980 West Ger many). The major result of the statistical analyses on the mainframe macrocomputer of the University of Erlangen-Nuremberg was that the relatively highest risk of asbestosis was present in persons whose expo sure began before 1955. On the other hand, with in creasing duration of exposure, an unequivocal rise of the asbestosis risk could not be detected on the basis of the overall population. In relation to the individual fields of work, the relatively highest risk of asbestosis was shown to be in the asbestos textile and paper in dustry, as well as in the asbestos cement industry. No detectable risk of asbestosis was present in the fields of mining, traffic and health service and for women in the industrial sectors of building material, gas and water, catering trade, building, commerce as well as banking and insurance. Accordingly, it can be assumed that certain fields of work are or were exposed to such a small extent or not at all that a risk of asbestosis which is relevant in terms of occupational medicine is Offprint requests to: H. J. Raithel no longer to be assumed or was not to be assumed. This applies above all to certain work in the frictional coat ing (brake lining) and asbestos paper industry. Fur thermore, the analysis of the data material did not provide any unequivocal indications that inhalative smoking habits have a negative effect on the risk of as bestosis. In prinicple, it can be stated that the occupa tional preventive medical investigations according to G 1.2 are effective. However, irrespective of this, the analysis has shown that a regular exchange of experi ence on the part of authorized physicians should be in stitutionalized and the second X-ray appraisal should be retained in order to ensure a high measure of relia bility and diagnostic relevance of the available investi gation data. Besides this, all expert appraisal results from patients with recognized occupational diseases according to subparagraphs, 4103,4104 and 4105 BeKV (no. 4103: asbestosis, no. 4104: asbestosis in connec tion with lung cancer, no. 4105: mesothelioma of the pleura or peritoneum) should be centrally registered and coded in the future. In this way, progress studies, both in persons exposed to asbestos dust and in per sons with asbestosis and accompanying malignant dis eases, would then be possible. Key words: Asbestos dust - Asbestosis - Health hazards - Preventive medical investigations Introduction In the last two decades, asbestos has increasingly been the subject of occupational and social medical as well as of environmental policy discussions. On the one hand, the excellent material properties and the multi farious possible industrial applications resulting from this have been emphasized. On the other hand, atten tion has been drawn to the various health risks. Good 528 reviews on this topic have been published by Worth and Worth (1979); Woitowitz (1972); Bohlig and Otto (1975); Bohlig (1976); Woitowitz and Valentin (1977), Selikoff and Hammond (1979); Woitowitz and Rodelsperger (1981) and Becklake (1986). Whereas health risks from fine asbestos dusts could not be systematically registered previously, it has been possible on the basis of our initiatives since the beginning of the 1970s to investigate all notified occupationally exposed persons in the context of pre vention according to professional trade cooperative association principles (,,Mineral Dust", G 1.2) and to monitor the asbestos-processing enterprises better. The essential data from the professional preven tive medical investigations according to professional trade cooperative association principle G 1.2 (= first examinations and follow-up investigations as well as subsequent supplementary investigations after the end of occupational asbestos exposure) have been col lected by the professional trade cooperative associa tion initially on an experimental basis, and from 1971 on a general basis by a ,,Central Registry of Employees Exposed to Asbestos Dust" (ZAS) in the Textile and Clothing Professional Trade Cooperative Assocation in Augsburg. Since 1973, all information has been stored there on electronic data carriers. Precondition for this was that occupational medical, clinical and radiological findings are documented in a form appro priate for EDP on standardized investigation sheets (VA 2- G 1). The X-ray findings were coded in accor dance with the International Pneumoconiosis Classifi cation (ILO U/C 1971 and ILO 1980/West Germany) in set III of the above investigation sheet or on the sec ond appraisal sheet specifically developed for this. Altogether, 70656 persons exposed to asbestos dust had been investigated in accordance with G 1.2 up to the end of 1986, and the data obtained had been stored. This data material constitutes the basic popula tion of the study and is the basis of all statistical analyses carried out. Materials and methods The objectives of this study can be outlined as follows: 1. The fibrogenic risk of exposure to fine asbestos dust of all persons registered by the Central Registry of Employees Ex posed to Asbestos Dust (ZAS) was to be investigated. The "risk" is characterized as a ratio of the number of radio logically abnormal persons (variation 1/0 and more in accor dance with ILO Pneumoconiosis classification) and the total number of persons in the population or the respective subpopu lation. 2. In the context of the risk appraisal, the beginning and du ration of exposure to fine asbestos dust was to be especially con sidered. H. J. Raithel et al.: Health hazards from fine asbestos dusts 3. The fibrogenic risk from exposure to fine asbestos dust was to be rendered objectively in various fields of work and for particular industrial sectors. 4. It was to be investigated whether the fibrogenic risk entailed in exposure to fine asbestos dust had remained the same for the entire period or whether it could be reduced by suc cessively introduced industrial hygiene and industrial medical measures. 5. Furthermore, it was to be established whether there are fields of work which have or had such a low exposure that no asbestosis cases could be observed. 6. Finally, the extent to which possible inhalative smoking habits influence the fibrogenic risk was also to be examined. The following factors are to be specified as limiting the in formation potentially available from this study: 1. The available empirical-casuistic data collection of persons exposed to asbestos dust is not accessible to any of the usual epi demiological methods owing to its unique character. The evalu ations we have carried out are hence not to be interpreted as a cross-sectional or a longitudinal study and also not as an inter vention study. A reference population was not available. 2. Exact statements on the incidence or prevalence of asbes tos-induced fibrosis are not possible on ths basis of the regis tered data, since neither histological results nor expert appraisals are available. On the contrary, besides some fundamental occu pational history data such as occupation, beginning and dura tion of exposure, only coded X-ray findings are available for ap praisal. These are regarded as an indirect indication of asbestosis with a variation of 1/0 and greater. 3. Data on pleural alterations have not been evaluated in this study because of the limited objective character on the one hand and the inadequate possibilities of coding with their un satisfactory relevance on the other hand especially X-ray exam inations of the thorax (Bohlig and Calavrezos 1987). 4. Because of the relatively long time intervals between in vestigations (three to five years), the data do not allow any reli able appraisals on the frequency of malignant diseases induced by asbestos dust (bronchial carcinoma and pleural meso thelioma). 5. Information on the further fate of the "abnormal" per sons detected in the preventive examinations cannot be given, since the data obtained in the context of expert appraisals were not regularly coded on the standardized investigation sheet ap propriate for EDP. 6. Reliable and adequate measurement data on the dust ex posure at the workplaces are not provided by the available data. A classification in terms of intensity of the exposure to fine asbestos dust in various fields of work can thus be made at best only on an empirical basis. 7. Since it is probable that not all persons exposed to asbes tos dust were registered, especially in the earlier years, an esti mated proportion of unknown cases is to be expected. Investigation data and statistical workup. The Central Registry of Employees Exposed to Asbestos Dust in Augsburg provided us with 70656 data sets on occupational preventive medical in vestigations in employees exposed occupationally to asbestos dust from the period 1973 to the end of 1986. This is based on the standardized investigation sheets "Mineral dust dangerous to health" and the relevant data they contain on -- occupational history (nature of exposure, beginning and du ration of exposure, work characteristics), -- results of medical investigations (physical examination, re sults of standardized tests of lung function, X-ray findings in ac cordance with ILO Pneumconiosis Classification U/C 1971 and 1980/West Germany and H. J. Raithel et al.: Health hazards from fine asbestos dusts - occupational medical appraisal by the authorized physicians of the data obtained. The data sets were checked for completeness and plausibil ity. In order to be able to make appraisals in terms of the objec tives formulated, we have stratified the basic population as fol lows: according to sex and age of the investigated persons, ac cording to industrial sectors and fields of work, according to the beginning and duration of exposure, and according to smoking habits. As X-ray finding, the coding of the second appraiser was re garded as authoritative when available. In the absence of a sec ond appraisal, the results of the first appraiser had to be in cluded in the analysis. The radiological findings of the structure of the small irregu lar lung radio-opacities (s, t, u) were classified into the categories 0, 1, 2, and 3. We assigned the subcategories of the variation 0/-, 0/0 and 0/1 to the category 0, the last being regarded as the highest subcategory of "normal". The three subcategories 1/0, 1/1 and 1/2 were subsumed in category 1. In agreement with the international scheme, categories 2 and 3 represent the sub categories 2/1, 2/2, 2/3 and 3/2, 3/3, 3/+. In the interest to dif ferentiate an appraisal as far as possible, the subcategories 0/1 and 1/0 are shown separately in Tables 2 and 4 in order to be able to appreciate better the borderline between normal and patho logical findings. This differentiated assignment of the results ap peared to be especially important, since experience shows that unequivocal appraisals in terms of fibrotic lung changes are fre quently not yet possible in these ranges of variation. However, in the following any X-ray finding will be rated as "abnormal" when the variation 1/0 (as a possible indication of an incipient asbestosis) is reached. The data material was analysed in strict observance of data protection regulations and laws. Results The respective last investigation data of 70656 em ployees exposed to asbestos dust were analysed. This data had been collected in accordance with the profes 529 sional trade cooperative association principle G 1.2. Of the persons investigated 63445 (= 89.8%) were men, and 7211 (= 10.2%) were women. In 19286 cases, the data derived from first investigations (= 27.3%), from follow-up investigations (= 44.0%) in 31085 cases and from subsequent supplementary investi gations (= 20.7%) in 14605 cases. In 5680 persons (= 8%) (!), the data sets did not contain any informa tion on the nature of the investigation. In 1760 cases, the proceedings for declaratory appraisal had been in stituted by medical occupational disease notifications in accordance with occupational disease no. 4103. We have no information on the outcome of these notifica tions. The radiological data (= coding of the findings in accordance with the ILO Pneumoconiosis Classifica tion) were collected towards the end of the report period by more than 500 authorized physicians ( = first appraisers). In some of the cases, a supplementary coding of the lung results was carried out by doctors with special experience in the appraisal of diseases in duced by asbestos dust (= "second appraisers"). In this way, a data bank which is as "hard" and reliable as possible was to be attained. However, since about 1980 an increasing reduction in the second appraisals has occurred. In the overall population we analysed statistically, there were only 34212 second appraisals as compared to 62293 first appraisals, and in 6510 cases of the first appraisals (!), no X-ray findings appropriate for EDP were coded at all. In 29934 investigations, only first appraisals were carried out, whereas second appraisals were carried out in merely 1853 cases. The image quality is of major importance for the establishment of findings in the chest scout-view X- Table 1. Medians and central 68-percentiles of age, beginning and duration of exposure, VC (actual/predicted value) and relative one-second expiration capacity for male and female patients with normal (category 0) and abnormal X-ray findings (categories 1-3) X-ray findings Age (years) Beginning of exposure Duration of exposure (years) VC (act./pred.) in % FEVj/FVC in % n No X-ray signs of fibrosis JX-ray signs of fibrosis X16/84 n Xm x16/84 49600 41.5 27.5-54.0 8167 53.0 42.5-63.5 46831 1973 1960.5-1979.5 8031 1964 1952.5-1974.5 38079 9.0 2.5-21.5 7667 15.0 5.5-26.5 48887 102.0 85.0-117.0 8002 93.0 73.0-109.0 48867 81.0 71.5-87.5 7997 78.0 66.5-84.5 n No X-ray signs of fibrosis X-ray signs of fibrosis x16/84 n x16/84 6061 42.0 28.5-55.5 729 58.0 46.5-68.5 5724 1973.5 1966-1979.5 708 1963.5 1953.5-1973.5 4427 7.0 2.5-14.5 201 11.0 4.5-18.5 5934 101.0 83.0-117.0 707 86.0 69.0-105.0 5926 81.5 74.5-88.5 707 79.0 69.5-85.5 530 H. J.Raithel et al.: Health hazards from fine asbestos dusts Table 2. Medians and central 68-percentiles of the vital capacity (actual/predicted value in %) and the one-second expiration capac ity (FEV 1 in %) in dependence on the X-ray findings X-ray findings Normal Abnormal Category 0 1 23 Sub-category 0/-,0/0 0/1 1/0 1/1, 1/2 2/1,2/2,2/3 3/2, 3/3, 3/4- VC (act./pred.) in % FEV 1 (%) n Xm x16/84 Xm x16/84 29048 103.0 87.0-119.0 82.0 72.5-88.5 25773 100.0 83.0-115.0 79.5 70.5-86.5 6876 93.0 75.0-109.0 78.0 68.5-85.5 1600 87.0 67.0-104.0 76.0 64.5-84.5 202 79.0 59.0-101.0 73.0 62.0-81.5 31 80.0 46.0-101.0 77.0 63.5-87.5 ray. For this reason, X-rays (hard radiation technique) were regarded as an adequate radiological procedure in the preventive investigations according to G1.1 and G 1.2. In the preventive investigations we evaluated, 74.5% of the X-rays were rated as legible without re strictions (+ resp. ) by the first appraisers, and 79.1% of the X-rays were rated as legible without re strictions by the second appraisers. On the other hand, the classification to the categories "adequate" () or "useless" (u) was made relatively more fre quently by the second appraisers. In this connection, it is also noteworthy that the first appraisers did not provide any data on the image quality in 9076 cases (= 12.8%!). This must be attributed above all to the fact that the second appraisals have been restricted since 1980 and have been largely omitted completely since 1985. The completeness and "hardness" of the data aimed for automatically suffered from this. All abnormal X-ray findings (= variation category 1/0 and over) are compared and contrasted with the thorax X-rays (= category 0) classified as normal sepa rately for men and women in Table 1. The median and central 68% regions of age, beginning and duration of exposure as well as vital capacity (actual/theoretical value in %) and one-second expiration capacity (FEV 1) in % are reproduced. It is shown that in men and in women the average age in abnormal X-ray findings is 11.5 and 16 years higher in the median respectively than in the subjects of the category 0. The beginning of exposure was on average about ten years earlier than in the "normal" persons both in the abnormal men and the abnormal women (1964 and 1963.5 respectively). The duration of exposure is also 15 and 11 years higher in the median in the cases with abnormal X-ray find ings than in those with normal lung X-ray findings (nine and seven years respectively). It appears to be important that evidently lower average duration of ex posure was sufficient in women (11 years as compared to 15 years in men) in order to become "abnormal". The parameters of lung function display a 10 to 15% lower value on average for vital capactiy in the persons with abnormal X-ray findings. On the other hand, on the median basis, there were no fundamental differences between "abnormal" and "normal" sub groups in the relative one-second expiration capacity (FEV 1). The characteristics of the two major analytical parameters of lung function (vital capacity actual/the oretical as well as FEV 1 in % ) are shown in Table 2 in relation to the coded X-ray findings. The vital capacity decreases in terms of a restrictive disorder of ventila tion with increasing variation category, whereas the relative one-second capacity does not show any ap preciable fluctuations and is within the normal range. In the context of this evaluation, the frequency of abnormal radiological findings in various fields of work is of particular significance. These categories are shown in Table 3 with inclusion of their subgroups and the pertinent professional trade cooperative associa tion index numbers. In Table 4, the number and percentage frequencies of X-ray findings are compiled according to variation categories or subcategories for men and women in var ious fields of work. The listing already shows that radiologically abnormal results were found relatively more frequently in the manufacture and processing of asbestos textiles, asbestos cement products, felts con taining asbestos, fleeces, in certain sectors of the as bestos rubber industry and in insulators. This is also confirmed by Table 5. Here, the figures for the radio logically "abnormal" and "normal" results as well as their relative frequencies (in %) are listed separately for different workplaces and in relation to smoking habits. Table 6 provides a synoptic overview on the relative fibrogenic risk set out in decreasing frequency according to fields of work. Accordingly, the greatest risk of radio logically abnormal alterations in terms of the variation categories defined above was present in the fields of the classical asbestos textile industry (weaving, sort ing, packaging, dispatch, carding, spinning, twining division, spooling and braiding) as well as in the asbes- H. J. Raithel et al.: Health hazards from fine asbestos dusts 531 Table 3. Code numbers together with the work places in the asbestos preparing and processing industry Code Work places no. Code Work places no. 110 Preparation of asbestos-materials 120 Transportation of raw asbestos (fibres) and asbestos- containing materials (only trade and transportation) 130 Storage and packaging of raw asbestos (fibres) and asbestos-containing materials (only trade and transportation) Production and preparation of asbestos-textiles (e.g. yarns, ropes, fabrics) 141 Storage of raw materials 142 Preparation 143 Carding 144 Spinning, twisting, coiling, plaiting 145 Wet-spinning 146 Weaving 147 Cutting and sewing 148 Sorting, packaging, dispatch of the final products 149 Miscellaneous Production and processing of asbestos-containingfelts, fleeces, papers, cardboards and plates 151 Storage of materials 152 Preparation 153 Wet-processing (beater, pulp, paper machine) 154 Drying 155 Cutting, sawing, punching 158 Sorting, packaging, dispatch of the final products 159 Miscellaneous Manufacture and preparation of asbestos cement products (e.g. plates, pipes) 161 Storage of raw materials 162 Preparation 163 Sawing, milling of asbestos sheets 164 Grinding 165 Drilling, punching 166 Processing of molded pieces and pipes like sawing, rotating, milling, grinding 167 Preparation of fibrous fracture 168 Sorting, packaging, dispatch of the final products 169 Miscellaneous Production and processing offriction coatings 171 Storage of raw materials 172 Preparation 173 Mixing 174 Pressing, hardening 175 Grinding, sawing, milling 176 Drilling, punching 177 Repair of brakes and clutches 178 Sorting, packaging, dispatch of the final products 179 Miscellaneous 180 Production and processing of rubber products containing asbestos (e.g. tires, washers) 190 Production and processing of asbestos-containing plastics (e.g. synthetic resin molding compounds, thermoplastic, laquer, insulation compound, floor covering) 200 Manufacture of other products containing asbestos 210 Usage of asbestos and materials containing asbestos for insulation (e.g. thermal- and sound insulation, fire protection) 220 Usage of asbestos fabrics and -textiles and asbestoscontaining textiles, as far as asbestos dust is emitted (e.g. blankets, awnings, aprons, gloves, tapes and cords) 230 Further usage of asbestos and asbestos-containing products with dust development (e.g. use of asbestos in cooling beds in the glass- and steel-industry) tos cement and paper industry and the work with raw asbestos. In the stratification according to industrial sectors, a relatively high incidence of radiologically abnormal results could be demonstrated in the sectors of "paper and printing" and "textiles and leather goods" in men, but also in the industries "building materials", "gas and water", "iron and metals", "chemicals" and "elec trical engineering, fine mechanics and optics" as well as finally "commerce, banking and insurance" (Table 7). There were evidently lower risks of acquiring ab normal radiological alterations in terms of asbestosis for women, above all in the industrial sectors "build ing materials", "iron and metals", "building" as well as "commerce, banking and insurance". In these fields, women are in some cases only now being employed or have been employed in very small numbers. Accord ing to our data, there was no risk of asbestosis in men and women in the industrial sectors "mining", "cater ing trade" and "health service". In the context of this appraisal, the stratification according to duration and beginning of exposure was of particular interest. Three subgroups were formed. The persons investigated are characterized with re gard to the duration of exposure into the groups up to 15, 16 to 25 as well as 26 years and over, and into the subgroups 1955 and earlier, 1956 to 1970 and 1971 to 1986 with regard to the beginning of exposure. This subdivision appeared to be reasonable, since succes sive improvements in industrial hygiene and medicine had been introduced into the asbestos industry in West Germany in the 1960s and 1970s. Figures and relative incidences (in %) of the ab normal X-ray results in relation to the beginning and Total no S n 532 9 n% X-ray findings available ----------------------- X -ray findings o f the lungs n% N orm al A bnorm al JO co CM + CM co co co JM CM t-h co CM CM CM CM d CM H CM CM d 00 CM iri in 00 d t-H CO Ht o Io od CM n 00 00 CO d CO CM in NO ON NO NO ON ON m ON Tf NO NO ON 00 CM CM CO CM 00 in CM t-H NO CM NO d Ht in CM d r-~ in r-t-H 00 T-H ON T-H nfr in NO CO CM H. J.Raithel et al.: Health hazards from fine asbestos dusts CO CM CM t-h d I o rf cm co in d d I d d d rn CM ^ rt; O hhO CO CM cO CO l in CM d CO in O rO t-h in cm tT d d d , d d in cm ^H t-H ^H t-H I CM t-H t--H co 00 00 in 00 CO r-' CO NO op t-H CM in CO d Tt CO co CM CO CO Tt- CO On oo in ON ON *1; 00 00 d d CM d d 00 in CO CO in 00 CO n CO Ht CO '0- t-H C-; CM 00 CO Ht in t-H ON d On CM CO 00 00 in in NO NO inct^hinoo-Tt O\'O00COH00'CH T}- -h CO On in 0- CM ON 00 00 CO Tf Tf in CO CO in NO* r-H d t-H t-H 0- CO NO CM CM no in t-h r- NO Tj* 00 00 CM 00 NO in CM CM CM NO CM r^ NO co NO d d d NO d CO 00 CO 00 00 CM NO n CO r- 00 NO CM T-H CO CM NO NO CO CM NO NO t-H CO in CO CO t-H 0- ^fONr-ooocMt^cMin NOT-HNOT-H^HOCMr*-. t-H^htJ- no 00 CM On CM II 0 CM I dt-h Tt CO CM odd H d oo co in t-h t-h t-h in in rI rf t-h CM Tj- t-H t-H in O O CM CO d d co CO in 00 NO T-H CO n co in CM NO Ht CO cO NO Tj- ^H ^H NO CM n 00 NO n CO 1 d CO d CO in CO ON NO CO ON NO CO CM 00 CO 00 On Ht 00 00 d d d 00 NO <n On r-> rr**-- CM On NO t-- CM 00 t> CO Tf CM d 00 n CM CO in H CM CO t-H CO i1 t-H1 d in NO* CM H NO NO CM t-H 11 CCOO t-H CO t-H CM in 00 in no' 00 NO* 00 CM d 00 o- ^H in Ht O" >n in r~- r- 00 ^H n t-H r- CM CM o t-H c- in oo on nf n cm cnoo -noh ON CO O CM in Table 4. Figures and relative frequencies in per cent o f the X -ray findings depending on w ork places Code no. W orkplace Q* il> a j? 5 H. J. Raithel et al.: Health hazards from fine asbestos dusts co co p+ co co ^H o1 CJ CM hh co CM CM t> co od CM p SO d rH 00 O p 00 Os CM r1o 1d p CO so p ddo oq p p p CM CM d d t-H p p d 00 d d t-h t-H 1o p SO do t-h p 00 Tt CM P Hd CM t-H 1111111 CM 1 1d t-H CM r-H 1 1 odo 1 o ^3- CO p ddd p as p rd CM rH p p p Tj- p O 00 00 00 d SO sd On pp p d ppp vs 00 vs 533 p 1d 1 t-H 1d p Os pp dod d p p t-H p p CM* d d cm' CM p p pp CM CM d CM CM H T-H T-H ^H t-H VS CM vs pP CM P Os CM o vs Os d Os CM O ro G- o- co CO 'G" CO p p p so O p p 00 d d o d o OS CO CM co CO CO CO p d vs CM CO TC Tt p Tt p O 00 On d d o CO CO rt Tt vs SO Os co CO P T--H p p t-H CM SO SO vs p pP p o p t-H p dX d SO co d d cm' P vs Tt CO d 00 CO CO P CM d On o d o SO vs so vs vs vs vs d SO vs CO so d sd sd d Tt CO CO CO 00 c 73 g n > 3 G Gm 'G > XG CM p d sd On 00 ppOp d d Os 00 On 00 c- On VS CM CM t-H On t"- T-H Tj* vs fTi r- r> CM t-H 00 00 On -=t m Os cn vs T-H so ^H m so r- Tf CM 00 ^H ppppppp 00 CM d d vs d d os On Os On OS Os Os t-H p p vs sd d Os On On vs o so o Os "3* r- CM o r- CM O vs VS so t-H cn CM CM SO CM ~H 00 ao vs CM p CM p p p sd sd VS 00 sd On On os 00 OS O SO c- -<1- CM c<s VS so Os CM 00 os vs vs CM r--t so T--H vs vs do p p r- d 00 ^ 1 pp dd CM I> o NO O O I T"( 1 CO 00 CM 00 pppp ppO sd d CM sO dd CM CM p vs p od d vs C*S T^ CM O' hH CM O' VS CM t-H CM CM o CO VS t-H CO oo t-h t-H CO CO CO CO ON oCO CO T-H p Tf p p 00 d d d dd vs o c- CO VS vs CM vs ^H CM CM t-H t-h *0 Ho s O. u I O a oo U vs p On On On On On SO CM roo sO T^ ppp Os Os On VS On 8 T*H r- CM On rvs On TfO t-H CM pp CM CM OS On CM so r- o CM CM 0\ p O p r- p o d CM 00 d oo d sd as Os On On c- On pPp ^H sd d SO GO 00 o Tt cn T-h c- cn r~~ rt-H CM o os Tf 00 O so tT cn CM C*S vs rs t-H t-h vs vs "3- CM p p p pp CM CM sd SO CM O' O' On Os Os cn so On OS ^H oo so tJ* VS r- 00 SO so <rs CM so t-H CO CO CO 00 r-- O' O' On r- On -=t 'G" vs CM t-H t-H t-H CM On Tf vs On CM vs CM r- t-h so SO co CO CO Tf Os O' vs CM Os os T^ CM o r- Os VS t" T-H CO CM SO Tj- CO SO o vs 00 O' vs CM NO CO CO CM CO CO 00 C" r- os o 00 SO rr CM CM SO t--H W> oo G 00 G G ga oo o 0C0 g.00 2 {2 , g> -c .3 0oC f3oe c u CS -'Scsfl *gG2> 533.s33 3.3 OV3 S3 ^ "S 00r. 5o0 2 *> a> TMs Xan) C/3 G *o a r`C,,h U O G 3 a. ca CD O ^s . =,,3 o<D a. go a5T ut>- X> Q 1| Qh 3 5/5 U*> Q = g 00 ^ a <u o CO 41 a -S ox ao u \n 3O oo *c ** M-l Ph O H-* c/3 H 0) .5 sZ a > 73 *- G G 00 o-o C r00 G"-j Q.h cj0-_0 `C `C SOQ JZ CL o o G a 3 Q 2 1/5 O J= "3 O G W) T-- G 0* Ou G o o X) o G *3 3 -O 3 `6 cu O o 3 ^ s o C/3 % 1h M-( Oh O O 00 tg _G ^2 (D ` v! Cl, c/5 X> 8 c5 SG 2O 00 J> G X) 2 3 to x C- g jC- ^--* to g G C0 oo W t3 G Op 2 co , G 50 .`X2 2to O co ft> o 00 _G to G &3 O 0) *3 o 2T3 c>o 3G TP3 mO-h JaO) JOh <hG-i 3 O Oh O K3 D oo o oo CM CO CM CM CM CM Table 4. Continued 534 H. J. Raithel et al.: Health hazards from fine asbestos dusts Table 5. Numbers of persons with normal and abnormal X-ray findings together with the relative frequency in % in dependence on the work places for smokers, ex-smokers and non-smokers Workplaces Code no. X-ray findings Normal Abnormal NS S + Ex no total info NS n% S + Ex n% No info n% Total n% Raw asbestos Asbestos textile Asbestos paper Asbestos cement Friction coatings Asbestos rubber Asbestos plastic Further asbestos containing products Insulation Asbestos textile Asbestos production 110 120 130 141 142 143 144 145 146 147 148 149 151 152 153 154 155 158 159 161 162 163 164 165 166 167 168 169 171 172 173 174 175 176 177 178 179 180 190 200 210 220 230 136 302 3 441 80 315 4 399 63 125 1 189 20 61 0 81 40 100 2 142 79 216 17 312 793 833 34 1660 2 12 1 15 193 233 6 432 298 369 7 674 52 113 5 170 282 477 16 775 13 36 2 51 18 52 - 70 122 296 3 421 1 3- 4 698 1436 25 2159 106 193 1 300 1045 2689 22 3756 48 145 3112 111 287 384 15 48 386 88 391 8155 340 728 995 95 141 1090 2 138 13 549 74 11341 2 453 3 1018 9 1388 - 110 3 192 12 1488 37 91 3 131 67 168 6 241 182 733 6 921 1225 3001 42 4268 1118 2312 36 3466 190 340 0 530 916 1431 18 2365 255 503 7 765 892 1612 19 2523 161 266 4 431 748 1639 17 2404 460 1149 10 1619 1519 3764 46 5329 161 336 2 499 384 808 17 1209 12 8.1 12 13.0 13 17.1 5 20.0 5 11.1 27 25.5 152 16.1 -64 24.9 48 13.9 11 17.5 55 16.3 2 13.3 1 5.3 9 6.9 -157 18.4 9 7.8 155 12.9 16 25.0 47 24.5 297 8.7 23 17.1 36 11.1 62 13.9 4 21.1 19 28.4 63 14.0 2 5.1 8 10.7 25 12.1 56 4.4 77 6.4 14 6.9 79 7.9 17 6.3 71 7.4 35 17.9 101 11.9 71 13.4 28 83 24 8 17 45 122 86 46 30 107 3 8 46 450 19 568 31 149 1082 65 81 241 25 61 288 11 19 79 173 192 34 198 38 214 80 321 261 8.5 20.9 16.1 11.6 14.5 17.2 12.7 27.0 11.1 21.0 18.3 7.7 13.3 13.5 23.9 9.0 17.4 26.1 27.6 11.7 16.0 10.0 19.5 20.8 30.2 20.9 10.8 10.2 9.7 5.5 7.7 9.1 12.2 7.0 11.7 23.1 16.4 18.5 -- i 20.0 2 66.6 1--10 22.7 -4 40.0 1 12.5 3 37.5 2 11.1 --1 25.0 -6 19.4 1 50.0 7 24.1 2 50.0 6 31.6 14 15.9 -3 50.0 7 43.8 -1 25.0 7 36.8 1 25.0 2 25.0 1 14.3 4 8.7 5 12.2 12 10.0 4 36.4 4 17.4 -- 4 19.0 5 33.3 40 96 39 14 22 72 284 154 95 44 164 5 9 56 613 29 730 49 202 1393 88 120 310 29 81 358 14 29 105 233 274 49 279 59 289 115 426 337 8.3 19.4 17.1 14.7 13.4 18.8 14.6 26.3 12.4 20.6 17.5 8.9 11.4 11.7 22.1 8.8 16.3 26.2 26.9 10.9 16.3 10.5 18.3 20.9 29.7 19.4 9.7 10.7 10.2 5.1 7.3 8.5 10.6 7.1 10.3 21.1 15.1 17.2 247 14.0 19 10.6 38 9.0 980 20.7 76 18.4 171 17.5 11 19.3 1238 -- 95 4 19.0 213 18.9 16.0 15.0 NS = non-smoker; S = smoker; Ex = ex-smoker H. J. Raithel et al.: Health hazards from fine asbestos dusts Table 6. Abnormal X-ray findings (in %) depending on work places Code no. Work place 168 Asbestos cement Sorting, packaging, dispatch of the final products 162 Asbestos cement Preparation 146 Asbestos textile Weaving 161 Asbestos cement Storage of raw materials 155 Asbestos paper Cutting, sawing, punching 180 Asbestos rubber 167 Asbestos cement Preparation of fracture material 148 Asbestos textile Sorting, packaging, dispatch of the final products 169 Asbestos cement Miscellaneous 120 Raw asbestos Transportation of raw asbestos (fibres) and asbestos-containing products (only commerce and transportation trade) 210 Usage of asbestos and materials containing asbestos for insulation (e.g. thermal- and sound insulation, fire protection) 143 Asbestos textile Carding 166 Asbestos cement Molded piece and pipe-processing: Sawing, twisting, milling, grinding 149 Asbestos textile Miscellaneous 200 Production of other asbestos-containing products 130 Raw asbestos Storage and packaging of raw asbestos (fibres) and asbestos-containing products (only commerce and transportation trade) 159 Asbestos paper Miscellaneous 164 Asbestos cement Plate processing: grinding 220 Usage of asbestos fabrics and -textiles and asbestos-containing textiles, as far as asbestos dust is emitted (e.g. blankets, awnings, aprons, gloves, tapes and cords) 190 Production and processing of asbestos-containing plastics (e.g. synthetic resin molding compounds, thermoplastics, lacquers, insulation material, floor covering) 230 Further usage of asbestos and asbestos-containing products with dust development (e.g. use of asbestos in cooling beds in the glass- and steel-industry) 141 Asbestos textile Storage of raw materials 144 Asbestos textile Spinning, twisting, coiling 142 Asbestos textile Preparation 147 Asbestos textile Cutting and sewing 153 Asbestos paper Wet processing (beater, pulp, paper machine) 152 Asbestos paper Preparation 163 Asbestos cement Plate processing: drilling, punching 172 Friction coatings Preparation 177 Friction coatings Repair of automobiles, brake and clutch service 165 Asbestos cement Plate processing: drilling, punching 179 Friction coatings Miscellaneous 173 Friction coatings Mixing 171 Friction coatings Storage of raw materials 151 Asbestos paper Storage of raw materials 158 Asbestos paper Sorting, packaging, dispatch of the final products 176 Friction coatings Drilling, punching 110 Raw asbestos Preparation of asbestos materials 175 Friction coatings Grinding, sawing, milling 178 Friction coatings Sorting, packaging, dispatch of the final products 174 Friction coatings Pressing, curing 154 Asbestos paper Drying 145 Asbestos textile Wet-spinning 535 Abnormal X-ray findings in % 29.7 26.9 26.3 26.2 22.1 21.1 20.9 20.6 19.4 19.4 18.9 18.8 18.3 17.5 17.2 17.1 16.3 16.3 16.0 15.1 15.0 14.7 14.6 13.4 12.4 11.7 11.4 10.9 10.7 10.6 10.5 10.3 10.2 9.7 8.9 8.8 8.5 8.3 7.4 7.2 5.2 - 536 H. J. Raithel et al.: Health hazards from fine asbestos dusts Table 7. Figures and relative frequencies of normal and abnormal X-ray findings in various industrial branches Industrial branches X-ray findings of the lungs Men Women Normal Abnormal Normal n n% n 1. Mining 2. Mineral industry 3. Gas and water production 4. Iron and metal industry 5. Electronic, fine mechanics and optics 6. Chemical industry 7. Wood and associated industries 8. Paper and printing industry 9. Leather and textile industry 10. Foodstuff industry incl. alcohol and tobacco 11. Construction 12. Trade, banking, insurance 13. Transport 14. Health service 1489 133 13252 2390 15927 350 682 2095 17 11385 1376 502 - 392 25 2645 369 2654 47 213 318 1250 208 66 - 20.8 15.8 16.6 13.4 14.3 11.8 23.8 13.2 - 9.9 13.1 11.6 - 41 1059 423 2244 4 262 1951 31 44 - Total 49598 8187 14.2 6059 Abnormal M% -2 4.7 -67 6.0 38 8.2 236 9.5 1 51 16.3 330 14.5 -- 1 3.1 3 6.4 --- 729 10.7 duration of exposure are shown for the individual fields of work in Table 8. According to the definition, only those cases whose thorax X-rays displayed the varia tion categories 1/0 or over according to ILO Pneumo coniosis Classification were rated as "abnormal" here. With regard to the duration of exposure, Table 8 shows that the number of proceedings for declaratory appraisal was greatest amongst the employees whose exposure began before 1955 for all three subgroups. On the other hand, the duration of exposure in a later beginning of exposure (1956 and later) appears to have less effect on the fibrogenic risk to the extent that the absence of subgroups with a longer duration of exposure permits an appraisal. These results are also confirmed synoptically by a graphic representa tion of percentage incidences of abnormal X-ray find ings in relation to the duration and beginning of expo sure (Fig. 1). However, it must be pointed out that the evalua tion of the data available did not consider all those persons exposed to asbestos dust at an earlier time who had died in the period before registration in the context of occupational preventive medical investiga tions was possible. With regard to smoking habits, Table 9 shows that smokers and exsmokers displayed radiologically ab normal findings relatively more frequently than non smokers. Above all it is shown (in accordance with general clinical experience) that bronchitis had occurred relatively more frequently in smokers and exsmokers (Table 10). In this connection, it must be assumed that incipient and slight reticular-linear structural prolifer ations in the X-ray (= subcategory 0/1 and 1/0) may be correlates both of asbestotic and chronic bronchitic alterations. It has to be borne in mind that these dis eases are also frequently present in combination and cannot be differentiated in radiodiagnostic terms. Discussion Occupational diseases induced by asbestos dust con stitute a topical theme in all industrialized countries. This applies despite the fact that prevention has been appreciably improved both in the fields of occupa tional hygiene and occupational medicine in the last 30 years. In West Germany, the financing agencies of the statutory accident insurance have intensified the re gistration of industries processing asbestos and using asbestos products in the last 20 years. At the same time, compulsory occupational preventive medical exami nations have been introduced for employees with expo sure to asbestos dust. The data from these preventive examinations according to G 1.2 (= first and follow up investigations as well as subsequent supplementary investigations) have been collected since 1971 by the "Central Registry of Employees Exposed to Asbestos Dust" (ZAS) in the Textile and Clothing Professional Trade Association in Augsburg. Up to the end of 1986, the results of more than 70000 persons for- Table 8. Figures and relative frequencies (in % ) o f cases w ith abnormal X -ray findings depending on the beginning and duration o f exposure H.J.Raithel et ah: Health hazards from fine asbestos dusts 537 16-25 26- Or"n1 1 1i 1 1111111 11111 \1111 1 I1111 ot\Q-l- IT) OrHN in' o' CM m rH co .1 o' oorrs-H--Hs .1 oorH o in rH CM 1. PP o CO NO CO 1 CO PP On CO in 0rH0 .1 1. ON rH m P P oo in CM rH 00 CM Pp CO CO rH rH CO CM in CM |1 rrHH ,-H rH CO PPpP in CM m CrHO TrHf* .i CM CO CM P 00 O o rH P P p rH s P P Os Tt P P P P P rH P p P P rH P P iiOnnn l oo dCO in CM d Oo oroH CCOr On w CCOO n m dm NO d w CM CrHO in iTnf OrHn Ht CM cO CM CTOt ON NO w cino. 0CM0 CO 00 CM, rH rj- CM CM CM Tt OrHN C- CO n CCOO T"H 1 r00- NO rrr-HHH -d- rH HNOt NO tHJ- ON CM rH On i0n0 CM CM i in CM 0roH011 OrHN 1 1 1 11 1 1 i11 or-I P P o' 00 00 P P P p P 00 cm CM CM 0rH0 tJ* dm CCOO 00 CoO CCMO OrHn N>OrHO0n NO H00 CO co ^H NO c- Tf r-* O CM CM CM sPpPP d CM CO CM CCOO CM ^H 00 r0H0 CM rHn P P P CO P CO On w CM in NO CM^ irnH rOHn Tj- 0CO0 CCMO CM CM r- P P O) in NO CM OrHN OC-n rH rH P P s P NO CM co CM^ iCnO On rH CM CO CM CCOO Ht CrHM P P CO p P P P S p IIDD ccoo NTOf, CCOO NO NO dn ooT--1 r-H CinO oC' d NO n OrHN 1 CM NO rH CM ^H CO 00 c*- NO rH-H p rH P P P P P in CO P P rH n SC--Mz irnf CCOO CinO' cn- imn 0rH0 CrHM CmO in 'r--H^ 0c~0 in r-H C0M0 CO NCOO co rH NCOO rH 00 NO CM CM rrHH HrHt p P rH P P CcOO m COOn 00 Tf* CM, CM On l> t-H Code no. D uration o f exposure (years) -15 N0O0 ^H OCrHn- P 00 CM in -rHrf irnH irnH CM CO CM 0s in p P P P p in NO NO On , irn"1 NO ON K CO NO CM CM r0H0 CTMf NCOO On cco- PPPppp NO 00 rH y--i CM in Tf CM c00- CO CM p P rH P p P hH P 00 'CrwHM' CrHM NO rrHH On 'riwnH' CM 'w' NO On mco NO c>on CinM (c*h- m CO P P oo rH in CO in 00 n in n rH C0O0 CrHM crHo rH ocNITO) OrHN in' P rH rH CM CO CM c-* o On CM P NO NO p P P rH 00 CO oCO in CM *fr CM CCMO* 0rH0 NO CO CM CM rrHH rH CM 0o0o r- NO CM ON orj- P P 00 p P rH rrHH Tt- CO CM NO CM CM CM 00 CM CM m CM CM CrHM CO CM P P 00 y--n P P p P rH NCOO C0O0 rH CO CM CM CM On w CM in CM NrHO NO NO Oinn 0rH0 NrHO 0NO0 CM r- CM P rH P 00 P CO rH CM rH 'ro--H6y rCHO 1 rH tJ- CM 0CO0 0m0 On rH O iinn cn >n CM CM, OrHN CO r-H /o--s 00 P P O d 'CwM'' CM rmH din rH CO CM CM CM 1 CM p __^ ^^ P P rH oTf r-H 00 CM, m CM On 1 r-H r-H r~ rH CM p 00 r- CCMO .1 Ht CM OrHn Pp NinO "3- NO CM PP NO in in CM 1 P in P CCOO in. 00 1 CO CM o^rHH o CrHM OCO rH Tt CTM|- rH CO "rdH- NTOf rH cTrHt oo rH ON rH rHn rCHMn CmO rmHn r0inH0 OmN rH rH CM NO CO NO NrHO m NrHO NO rNHO O rH oo ON rH rcH- CM rr-H~ CO rrH-- c- ricnH- r- D TZS <oA X 0) (oA cfl > O d <U cd on OS < 0> G<u> cad Or 0 <ou <A O (o/) on cfl <L> D << <3J0 c *cd Oo G O o *n W orkplace 538 H. J.Raithel et al.: Health hazards from fine asbestos dusts 16-25 26- r- Ov rH 1 1l 4) t"* | q SO (/> to o Q, On rH X 4> I** o D _C *3 q ID '5b 4) in 05 r"1 03 1 V CO r- cm' CD SO 05 rH CM rH s---' '--' o ID r- 7--4 rH orH CD SP rH sd ww SO 05 y*^ y-^ y--^ y^ y-^ y--^ CM CD 05 00 so CD sd ID SO 00 05 CD 7--1 w CM ID CD CM CM ID o O 00 CD Tf rH ID SO 0011 rH t> Os rH 1 1 OO p P 05 CM 00 rH rH '--' w CM CM SO tC y-^ y--V, y-^ 05 rH CM ID 00 CD CD w SO D O t-~- ID (M 1 r- 4) lx 3 l y0 id Q a 05 rH X 4) o 0 S *3 q id `5b IQD\ 4) rH 03 1 P P 00 CD rH SO sd rH CD SO rH 00 VO P so CD SO Tf CM so ID <N C- S' w VO C- y--^ y--^ y--V y--V y-^ y--V 00 rH o CM 05 7-4 o CM o so ID wCD CD w ID 00 o CD ID rH /--V 00 P rH CD "t d CM CM rH O rH 00 Th CM CD CD y-y y--N y--^ o 00 d Ov d WCD rH CM 05 Tf ID 00 rH PkO oo 00* CD1 PP 00 d CM ID rH 05 j rH H l> os oo o 7-4 SO 00 rCD rH so tjr- rH rH P P rH 05 rH 00 rH I> 00 rH CD CM ID CM C- 4u3> | lsO ID Q aX Ov rH V4+H) o A .5 qa D *4>b X ID 0H5 1 ID p p S oo CM 00 sd sd rH rH rH 'w' 'rHw' CM CM CM SO O CD rH D 05 CM CoD rH S CM* CM 0050 y--S y--^ y--S, so CM vO 00 CM rH CM s--' w CD CM CM CM rH oO rH Tj- y--^ y--^ do D vC--D' Tt l> s sc" P d Tf" sd rH rH rH 'x' rH CD SO 05 CM CD rH y--^ y--^ rH o o CD d 00 rH sC-M"/ rH rH r- CD rr--~ 0l>0 0r5- o00 O 05 O rH rH rH rH rH CM Ooo CM CD CM CM CM C/3 o3 C o 'C lx 4) x> 3 lx a 'SC/3 C/3 0 o lx C/3 0- CIS a. aj XC/)3 t30 fT _4) X 4) 3o o o a S/3 o c/3 O CO c lx `c3 XUl <X> o o 8 8 8 83c/3 4> C/3 4) XI t3s o 4) c5 1 6C 4) u: 4) < < Uh &<< merly or currently exposed occupationally to asbestos dust could be registered. The data sets of the last in vestigation performed were available to answer the questions we formulated above. The present study at tempts to detect the consequences of asbestos dust in filtration in empirical-casuistic terms on the basis of occupational preventive medical investigations. It also attempts to appraise the fibrogenic risk in various fields of work with consideration of the beginning and duration of exposure. It is thus not an epidemiological study in the classical sense; on the contrary, the results and data of occupational preventive medical investi gations have been analysed statistically. As far as we know, comparable investigations have not been pub lished up to now. In our analysis, the appraisal of the risk of asbestosis is oriented to the coding of the X-ray findings of the lungs. An X-ray finding was rated as "abnormal" in terms of asbestotic alterations when at least the varia tion 1/0 of the small irregular lung radio-opacities (s, t, u) or a higher subcategory had been attained in accor dance with International Pneumoconiosos Classifica tion (ILO U/C1971 or ILO 1980 West Germany). On the other hand, the initiation of the proceedings for declaratory appraisal could not be regarded as a reli able criterion for radiological asbestotic lesions, since it is shown in the data analysis that normal lung results of category 0 were recorded in more than 23% of the proceedings for declaratory appraisal instituted, so that according to the definition there were no indica tions of asbestosis (Otto 1976).This discrepancy will be discussed in more detail elsewhere. A major result of our evaluation so far is that the intensification both of industrial hygiene and occupa tional medical measures has led to an appreciable re duction of the risk of asbestosis. The decrease of the risk from 1956 to 1970 and to a greater extent for the period from 1971 to 1986 is shown inter alia in that the relative frequency of the higher variation categories decreases, and the prevalence of normal findings in creases. The conditions in the individual industrial sectors and fields of work require a differentiated appraisal. There was thus a relatively high risk of as bestosis inter alia for women in the asbestos textile in dustry up to the middle of the 1950s; here, relatively short exposure times were sufficient in order to give rise to clinical manifest asbestosis. In the asbestos cement industry, besides asbestos processing surprisingly the departments involved in sorting, packaging, dispatch of endproducts and the raw materials store were found as industrial sectors or fields of work with a relatively high risk of asbestosis (cf. Table 8). However, it must be borne in mind here that the fields of work specified last are areas of pre dilection for switching of workplaces within the enter- Code no. D uration o f exposure (years) -15 W o rk place H. J. Raithel et al.: Health hazards from fine asbestos dusts 539 0) c<ur >+- at cac> Fig-1* Relative frequencies (in %) of findings with abnormal X-ray findings (sub-category 1/0 and/or more) in relation to the duration and beginning of exposure Table 9. Numbers and relative frequencies of normal and ab normal X-ray findings in smokers (including ex-smokers) and non-smokers X-ray findings Smoking habits NS S + Ex n% n % No information n% Abnormal Normal 2180 11.4 16986 88.6 6603 14.8 38159 85.2 133 20.5 516 79.5 Table 10. Numbers and relative frequencies (in %) of patients with chronic bronchitis depending on the smoking habits and the X-ray findings X-ray findings Smoking habits NS n% S + Ex n% No information n Abnormal Normal 259 23.0 869 77.0 1000 28.2 2552 71.8 10 16 prise when a workplace with lower risk is to be found for employees with abnormal lung findings. It is thus to be assumed that persons with a formerly more inten sive exposure have also been registered here. How ever, the data available to us only show the last field of work. Less danger with regard to the risk of asbestosis were and are present in the frictional coating (brake lining) industry, especially in car repair, in brakes and clutch service, in certain areas of the asbestos cement industry as well as evidently in areas of drying work in the asbestos paper industry and the wet spinning divi sion in the asbestos textile industry. The fact that absolute figures for the asbestoses compensated for the first time and malignancies in duced by asbestos dust (occupational disease no. 4103 4105) are still rising at present in the "Occupational Disease Documentation" is essentially due to the la tency periods of 20 to 30 and more years on the one hand and on the other hand is due to the fact that rela tively slight or brief exposures to asbestos dust appear to be relevant, in particular for the induction of malig nant mesotheliomas. In this connection, it must also be taken into consideration that the number of persons exposed to asbestos dust increased markedly in the 1960s and 1970s. The data material available to us does not allow any appraisals of the cancer risk from inhalation of fine asbestos dust (IARC1977; Becklake 1986). The symbol "ca" (carcinoma) was entered 51 times and the coding "me" (mesothelioma) 12 times in set III of the investi gation sheet, i.e. suspicion of a neoplasia of the thorax region. However, it was not possible to verify these diagnoses on the basis of our data from preventive in vestigations. To what extent a putative cancer diag nosis has been confirmed at all and in particular with regard to asbestos as the cause is not apparent from the investigation data, since these cases could not be followed further either in time or with regard to the outcome of the occupational disease proceedings. The professional trade cooperative associations are therefore recommended to have all investigation results in the context of occupational disease proceed ings and expert reports coded on standardized sheets according to G 1.2, and thus to bring together in the Central Registry of Employees Exposed to Asbestos Dust in Augsburg all data of all exposed persons irre spective of the question of recognition of an occupa tional disease in accordance with subparagraphs 4103 4105 BeKV. Finally our evaluations have confirmed once more that relevant investigation results have not been docu mented or have only been documented incompletely in a substantial percentage by the authorized physi cians. Irrespective of the radiological coding accord 540 ing to ILO Pneumoconiosis Classification (Bohlig et al. 1981), its application requires that the basic rules of clas sification must be followed (here in particular compari sons with adequate standard films). Important anam nestic data such as areas of work, beginning and dura tion of exposure were not specified or only partially specified. These parameters were thus not available in a percentage which varies between ca 10 and 25%! This situation can be improved by regular exchange of experience between authorized physicians and second appraisers at seminars. This has repeatedly been sug gested by the doctors concerned. In particular the capacity to code X-ray findings cannot be learned solely from papers and slide presentations, but can be ac quired and promoted in seminar work in small groups. On the part of the professional trade cooperative associations, essential instruments rendering the in vestigation data more precise would be to monitor more consistently the instrumental and especially the professional prerequisites for authorized physicians, and in particular to keep the number and fluctuation of these doctors as small as possible. In addition, the system of second appraisal by especially experienced physicians which is plausible from a medical point of view and which is also required by the International Labour Organization (ILO) in Geneva should be re tained and intensified. Only in this way is the strict ob servance of the given coding instructions to be en sured. At the same time, however, the reliabilty and information content of the data contained in the inves tigation sheets "Mineral Dust" could be further im proved in this way. Conclusions and recommendations In terms of the objectives specified at the beginning, the following conclusions can be drawn: 1. On the basis of the overall population, the high est relative pathogenic risk induced by fine asbestos dust was present in persons whose exposure commenced before or up to 1955. In these cases, a duration of ex posure of a few years was often sufficient to result in a clinically manifest asbestosis later. With a later begin ning of exposure, the risk of asbestosis must be re garded as considerably lower. This also applies even considering the relative long latency periods of 20 years and over. 2. With increasing duration of exposure, no un equivocal rise of the fibrogenic risk can be detected on the basis of the overall population. This applies even when it is considered that occupationally exposed per sons have been repeatedly switched from workplaces with high exposure to areas of less risk. 3. Abnormal radiological findings as indications of asbestosis were found relatively frequently in men and H. J.Raithel et al.: Health hazards from fine asbestos dusts women in the industrial sectors "paper and printing" as well as "textiles and leather". Previously women were at risk above all in the classical fields of the asbes tos textile industry (weaving, carding). It is important in this regard that women were frequently employed formerly as unskilled or semiskilled staff under un favorable conditions of industrial hygiene. For men, there was evidently a relatively high fibrogenic risk in the industrial sectors "building materials", "iron and metal", "gas and water", "chemicals" as well as "elec tronic engineering, fine mechanical engineering and optics". On the other hand, no appreciable fibrogenic risk was present in the industrial sectors "mining", "catering trade" as well as "health service" and for women in the areas "building materials", "gas and water", "building" as well as "iron and metals". How ever, it should be considered here that women were practically not employed in certain areas of industry, or that processing of asbestos generally did not occur (Table 7). 4. The fibrogenic risk has decreased appreciably since 1955 with a later beginning of exposure. The consistently performed industrial hygiene cleanup measures and the occupational preventive medical ex aminations according to G 1.2 are responsible for this. No appraisals can be made about the oncogenic risk on the basis of the data material available. 5. Certain fields of work are or were evidently sub ject to such low exposure that a fibrogenic risk induced by asbestos dust which is relevant in terms of occupa tional medicine cannot be assumed. This applies irre spective of the fact that asbestos is increasingly being replaced in production by other materials or fibers for certain work in the brake lining, but also in the asbes tos paper industry. 6. The analysis of the data material did not provide any unequivocal indications that inhalative smoking habits affect the fibrogenic risk in principle. A rela tively higher number of radiologically abnormal find ings were found in the group of smokers and exsmokers only in occasional areas of work. These tendencies which are significant in subpopulations cannnot be extrapolated to the overall population, however (cf. Table 5). Finally, our evaluation has also shown that preven tive investigations according to G 1.2 have proved in principle to be a useful instrument for occupational medical monitoring and prevention in persons ex posed to asbestos dust. This does not rule out the pos sibility that on the basis of experience further im provements should be carried out where necessary. For this reason, the following concluding recommen dations are made: I. In future, all those patients where an occupa tional disease is recognized and if necessary also com H. J. Raithel et al.: Health hazards from fine asbestos dusts pensated in accordance with occupational diseases no. 4103,4104, or 4105 should be generally registered and coded. Only in this way would a follow-up study of all persons exposed to asbestos dust be possible. 2. In the context of postgraduate training, an ex change of experience at seminars should be organized for authorized doctors in order to restrict appraiser variation and to ensure as high a state of training as possible. 3. Finally, the second appraisal of X-rays by espe cially experienced doctors should be retained and in tensified. The reliability and informative content of the available investigation data could be appreciably improved by this measure. References Becklake MR (1986) Asbestos-related diseases of the lung and other organs: Their epidemiology and implications for clini cal practice. Am Rev Respir Dis 114:187 Bohlig H (1976) Asbestose. In: Ulmer WT und Reichel G (Hrsg) Pneumokoniosen. Springer, Berlin Heidelberg New York (Handbuch der Inneren Medizin, Bd IV) Bohlig H, Calavrezos A (1987) Development, radiological zone patterns, and importance of diffuse pleural thickening in re lation to occupational exposure to asbestos. Br J Ind Med 44:673-681 541 Bohlig H, Hain E, Valentin H, Woitowitz HJ (1981) Die Weiterentwicklung der Internationalen Staublungen-Klassifikation und ihre Konsequenzen fur die arbeitsmedizinischen Vorsorgeuntersuchungen staubgefahrdeter Arbeitnehmer. Prax Pneumol 35:1134-1139 Bohlig H, Otto H (1975) Asbest und Mesotheliom. Fakten, Fragen, Umweltprobleme. Thieme Verlag, Stuttgart IARC monographs on the evaluation of carcinogenic risk of chemicals to man (1977). Asbestos, vol 14. International Agency for Research on Cancer, Lyon Otto H (1976) Morphologie der Silikose und Asbestose und ihre klinisch-diagnostischen Risiken. Internist Praxis 16:43-50 Selikoff IJ, Hammond ED (eds) (1979) Health hazards of asbes tos exposure. Ann NY Acad Sci 330:1 Woitowitz HJ (1972) Arbeitsmedizinisch-epidemiologische Untersuchungen zu den unmittelbaren Gesundheitsgefahren durch Asbest. In: Arbeit und Gesundheit, Heft 86. Thieme, Stuttgart Woitowitz HJ, Valentin H (1977) Zur arbeits- und sozialmedizinischen Begutachtung von Asbest-Inhalationsfolgen. Prax Pneumol 31:153-159 Woitowitz HJ, Rodelsperger K (1980) Umweltbelastung durch Asbest und andere faserige Feinstaube. Tumorepidemiologie. In: UBA-Berichte 7/80. Schmidt, Berlin Worth G, Worth H (1979) Erkrankungen durch Inhalation von Asbeststaub. Prax Pneumol 33:701-725 Received January 26 / Accepted July 13,1989