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Mortality Study of Talc Miners and Millers Giovanni F. Rubino, M.D.; Giovanni Scansetti, M.D.; Giorgio Piolatto, M.D.; and Canzio A. Romano, M.D. T h e purpose of this research is to ascertain the causes of death in talc miners and millers. Special attention is paid to the incidence of pulmonary, mesothelial and gastrointestinal tumors. Our studyiwas conducted on a talc w hich is mineralogically very pure in its natural state. This is the type of material used in the pharmaceutical and cosmetic industries. All the subjects of our study have worked in the mines and the mills of the talc operation in: the Germanasca and Chisone Valley (Piedmont). This particular talc has been mined for many decades and has continued to be recognized to be of the highest standard of purity (see Appendix). An epidemiological study w hich can be taken as reference for our investigation was conducted by Kleinfeld et al., and re cently reviewed w ith additional informations (1974), on talc miners and millers in the State of New York.1 2 The incidence of carcinoma of the lung and pleura in those workers was found to be about four times that w hich is observed in the general population. This Nevv York Study was on workers exposed to an in dustrial talc w hich is a mixture of talc and other materials. Kleinfeld points out that the talc to which his workers were ex posed "contained not only mineral talc but also other silicates such as serpentine, tremolite, anthophyllite, and other ingredients predominately carbonates. Moreover free silica was present in the dust in variable amounts, usually averaging not more than three percent". Therefor^, our present epidemiological study provides a basis for comparing subjects exposed to an impure industrial type of talc (e.g. Kleinfeld Study) to subjects exposed to a very pure type of talc. Type of Study and Data Collection An historic prospective study has been employed consisting in the follow -up of a cohort of male subjects w ho began work at a definite time and including retired as well as active workers. We have been able to do so because we had at our disposal a group of subjects fit for this type of investigation. Data were collected for each worker who began work in the years between 1921 and 1950 and w ho has been employed for at least one year in a job involving exposure to talc in the mines or in the mills. Necessary informations such as birth date, place of birth, last known address, type and duration of all works performed, were abstracted from pay rolls and DUST CONCENTRATION IN AIR ALONG Presented at the 60th Annual Meeting oi the American Occupational Medical Association, American Industrial Health Conference, April 15, 1975, San Fran cisco. Dr Rubino is Professor of Occupational Medicine and Director, Institute of O c cupational Medicine, Turin University Drs. Scansetti, Piolatto and Romano are assistants. Institute of Occupational Medicine, Turin University. Reprint requests to Dept, of Occupational Medicine, University of Torino, C T O -- Via Zuretti 29, 10126 Torino, Italy Decreasing trend of total dust in respirable range, following the adoption of techni cal preventive means from 1950. records of a mining company o f Pinerolo (Piedmont). Cumulative exposure for each worker was estimated from the results of successive determinations of air dust content from 1948!till today (see Figure) and quantified by calculating an approximative value of the total amount of inhaled particles during the employement period. This one was considered to be finished at the retirement time for retired workers and on |une 30, 1974 for active workers. To compute cumulative dust exposure for each man, periods of job along w hich the dust level was uniform were selected, then the number of particles per cubic foot was multiplied by the number of years w ithin each period and the resulting values for each period were summed. The cumulative exposure is then expressed as mppcf/years. Thus, if a worker has been employed for 12 years at the fo llo w ing exposure to dust: 10 years at 566 mppcf, 1 year at 440 mppcf, 1 year at 360 mppcf, his cumulative exposure w ould be (10 x 566): + (1 x 440) + (1 x 360) = 6460 mppcf/years. All workers were then classified on the basis of three ex posure levels for miners and millers as follows: (see also Table 2) Miners Exposure Level 1 mppcf/years 566 - 1699 Exposure Level 2 mppcf/years 1700- 5665 Exposure Level 3 mppcf/years 5666 - 12750 Millers Exposure Level 1 mppcf/years 25-141 Exposure Level 2 mppcf/years 142 - 424 Exposure Level 3 mppcf/years 425 - 906 However we should remember that miners and millers ex posures ate not comparable because air dust in the mines in cludes a Certain amount of inhalable silica particles (see Ap pendix). Therefore we have separately studied miners and millers obviously excluding from the cohort of millers all sub jects w ho have worked in the mines even for a very short period of time. We gathered a total of 1514 miners and 478 millers qualified by our definition of the sample For purpose of comparison w ith a non-exposed group we TtWt L -- FoMor-ap Stata* vi Tate Miatn i4 Millars (1921-1974). W an No. * Son No. % Tout 1514 100 (71 100 Fon* 134 88.9 438 91. IM aom 168 11.1 40 8.4 TiWa 2. -- Distribution <1 Telai Nnmbtr al InbaM Partidas in Wean ana W llan With CetapieM Failea-up. toon ctfteaii No. M an mppeflyoire No. by. U ni 1 566- 1699 W 849 405 30.1 25 - 141 n 76 163 37.2 y. Loool 2 1700 - 5665 V 3796 423 31.4 142 - 424 12 297 144 329 Ely. lavo! 3 5666 -12750 H 8470 518 38.5 425 - 906 V 651 131 29.9 Total 1346 100 438 100 Journal of Occupational Medicine/Vol. 18, No. 3/March 1976 Tabla 1 -- Vital Status ai 134 Miaen and 431 W llan mth Compiatad Folloor-up and Itaspettivi Centrals (an June 1974). Minore Controls Milore Controls - No. % - No. 1 No. 1 - No. % Dosa 704 52.3 851 63.2 227 51.8 275 62.8 Mho 642 47.7 495 36.8 211 48.2 163 37.2 Ksom CooSOS al Daatk ' 667 94.7 813 915 218 96 254 92.4 Tabla 4. -- reaps to be Campared: Distributieo oi Subjects bp Ape, Latency and Vital Status. thought it advisable to use an "ad hoc" control sample matched by age to the exposed workers sample, rather than a comparison w ith national death rates which could introduce some confounding variables (such as feeding habits, ethnic characteristics differences etc ) . 3 4 Control subjects were taken from the population of the town of Alba w hich presents similar ethnic characteristics and com parable social and economic conditions. Alba is a Pied montese center, about 38 miles from the Pinerolo Valleys, with a dominant traditional agricultural activity and very little indus trial development not involving any obvious hazard of occu pational diseases or carcinogenesis to its workers. Every subject in the exposed groups was individually matched to a control subject by the following procedure. From the City Hall records all subjects born in the same year as a given exposed worker and still alive at the time of his first em ployement were ordered and listed according to their month and date of birth. Among these the first available (i.e. not already used for matching) subject was selected as the matched control subject. As it turned out, by this procedure almost the full list of subjects potentially suitable for matching was in the end included in the control sample. Follow-up of Study Population A follow -up procedure was instituted for every exposed subject w ho had left employment and whose vital status could not be determined at the plant as well as for the whole control group. The City Hall registries of birth place and/or death place provided information on vital status. Follow-up is 88.9% complete on miners and 91.6% complete on millers. Table 1 shows the follow -up and vital status of the exposed population and their controls, as of June 30, 1974. The distribution of all workers on whom follow -up was complete according to the Exposure Level is shown in Table 2. 187 Table 5. -- Overall Mortality -- Observed/Cxpected Deaths by Interval Between First Exposure and Doatb (by Exposed 1 Controls Comparison). Latency yrs. 1 -10 11-20 21-30 31-40 41 - SO 50+ Tet* M ian OhsjCap. taHe 60/S4.2 0.81+ 110/119.6 203/208.8 188/207.0 0.92 0.97 0.91 126/157.5 0.80t 9/14.1 0.64* 704/791.2 0J9+ M n ObsAip. she 16/29.6 0.54+ 46/41.7 66/67.9 57/72.5 38/42.2 4/4.5 227/2514 1.10 0.97 0.79+ 0.90 0.89 0J8+ * Statistically significant at 5% level +Statistically significant at \% level The information relating to cause of death was obtained from death certificates for both exposed and controls and was coded according to the International Intermediate Classifica tion of 150 causes of death5 w ith additional items (mesothelio ma, silico-tuberculosis) related to the possible effect of oc cupational Exposure. Death certificates are the source of in formation gsed by the Italian Central Institute of Statistics (ISTAT) to compute national mortality rates. Although they may not always be completely accurate, they are available in a high percentage of cases and are suitable for epidemiological purposes arjid w idely used, by many authors,610 allowing to compare tw o populations with homogeneous diagnostic criteria. A total of 1840 death certificates were collected. When the cause of death was not found by death certificates or if there were not enough indications for diagnosis (e g car diac failure reported as death cause) a further enquiry was started w itfj relatives of deceased, attending physicians or ex amining hospital records for hospital deaths. A further number of 112 causes of death (59 for miners, 39 for miners Controls, 5 for millers, 9 for millers controls) were so obtained to give the total number of known causes of death reported in Table 3, The subsequent statistical analysis was conducted on 1346 miners and 438 millers on w hom follow -up was complete. Workers reported dead but for whom neither death certificates nor the aboive sources of information were available were con sidered as deaths due to unknown cause No smoking data were available for dead people in exposed and control groups. However, as the tw o populations (exposed and controls) come from areas previously studied from ethnic, social and economic point of view, we have no grounds for assuming tfiat there are differences in smoking as well as in feeding habits. Methods pf Analysis Statistical analysis was conducted by a comparison between exposed groups (miners and millers) and their matched con trols and, vj/ithin exposed samples, by an internal comparison among the three above mentioned groups w ith different cumulative dose of inhaled particles. For both exposed versus controls comparison and internal comparison a modified life table technique, adjusting for age by indirect standardization method11 was used to compute ex pected number of deaths. Age intervals were: < 30, 30 - 50, 51 - 70, > 70 188 Latency periods (interval between first exposure and death) were: 1 - 10, 11 - 20, 21 - 30, 31 - 40, 41 - 50, > 50. General outline is shown in Table 4 Number of deaths to be expected on null hypothesis for each age-latency period sub-group at risk under.examination (Zei) was computed as: XEi -f- Xo EXPECTED DEATHS = -------------- x Z ei Z ei + Zei W hile for the comparison between exposed workers and controls the "com bined group" (exposed + controls) was taken as the reference group ( Z ei + Z o ) , the comparison among classes of differently exposed workers the w hole ex posed group was taken as reference. Deaths to be expected were computed for overall mortality and for 22 major causes of death. Expected and observed values of deaths were added up for different ages w ithin each latency period cell in order to exam ine the total impact of mortality along the observation period (see Tables 5, 6, 7). Pooling for age and latency was performed for comparison according to specific causes of death (see Tables 8, 9, 10, 11, 12). The ratio of the number of observed deaths to the num ber to be expected provides an indication of the excess of mor tality in the group w ith risk under examination in respect of the standard population (reference group) One degree of freedom "ch i square" tests were used to assess statistical significance of individual comparisons (ex posed vs. controls, exposed at Level 1 vs. exposed at Level 2 TiM 6. -- Miners: Overall Mortality -- Observed awl Expected Deaths by Interval Between First Exposure and Death (by Internal Comparison). Latency yrs. Exp. Level 1 ObwExp. lahe 1 10 11 20 21 30 31 - 40 41 50 36/24.5 40/33.7 62/59.5 50/53.7 41/40.6 1.47+ 1.19 1.04 0.93 1.01 50+ 2/2.6 0.77 Total 231/214.6 1.08 Exp. Level 2 ObsJExp. 32/23.4 42/35.4 60/55.1 41/41.4 32/29.8 2/2.1 209/1872 naho 1.37* 1.19 1.09 0.99 1.07 0.98 1.12* Exp. Laval 3 Obt/Exp. 718.7 28/39.7 81/87.2 97/93.1 53/55.2 5/4.4 264/2913 Ratio -- 0.710.93 1.04 0.96 1.14 0J9* * Statistically significant at 5% level 7 Statistically significant at 1% level Table 7. -- Millers: Overall Mortality -- Observed/Cxpected Deaths by Interval Between First Exposure and Death (by Internal Comparison). latency yrs. 1 10 11 20 21 30 31 40 41 - 50 50+ Total Exp. Level 1 OfcuEip. 14/7.6 20/16.7 32/27 3 23/212 10/12.9 3/2.6 102/UJ Ratio 1.84+ 1.20 1.17 1.08 0.78 1.15 1.15 Exp. Level 2 ObsJExp. 2/5.2 23/18.5 20/14.5 15/10.3 4/3.7 A3.15 64/52.4 Ratio 0.38 1.24 1.38 1.46 1.08 -- 122* Exp. Level 3 Ohufxp. 72.9 3/11.0 14/22.7 19/24.4 24/21.6 1/1.4 61/14 Redo -- 0.27 0.620.78 1.11 0.71 0.73+ * Statistically significant at 5% level ^Statistically significant at \% level M o rta lity Study of Talc M iners and M illers/Rubino et al and 3, etc . . .) standardized as previously described for age or for age and latency. In each table a single asterisk indicates the ratios w hich had a probability of 0.05 of occurring by change and a dagger indi cates those which had a probability of 0.01 or less. Statistical significance of comparison between cells containing less than five cases was not tested. Results By exposed versus controls comparison the observed overall mortality of talc miners and millers is significantly lower than expected. There are 704 observed deaths compared w ith 791.2 expected among miners and 227 observed compared w ith 258.4 expected among millers. Table 5 shows that no relationship exists between the ratio of observed to expected deaths and interval between first ex posure and death. Among miners a number of individuals, who died rpore than 41 years after their initial exposure, has been found significantly below its expected values. By the comparison among different exposure classes the ratio does nbt increase w ith increasing exposure. As shown in Tables 6 antjj 7 in both miners and millers an excess of ob served to expected deaths occurs at Exposure Level 2 for the total sample, In the "h ig h " exposure groups the excess does not persist and on the contrary statistically lower than expected number of deaths is detectable. Neither in this last group nor in the others are there increases in ratio w ith increasing interval between first exposure and death for miners and millers. When the overall mortality of study populations is sub divided according to cause of death some major patterns emerge for miners. Table 8 shows that by exposed versus con trols comparison death from all respiratory diseases is signifi cantly higher than expected as opposed to malignant neoplasms as a whole, cardiovascular diseases, gastrointestinal diseases and "a ll other causes" w hich show a number of ob served cases significantly lower than expected. Splitting respiratory diseases by kind provides evidence that the excess of mortality in exposed miners is due to the high in cidence of pneumoconiosis w ith or w ithout tuberculosis. Among all malignant neoplasms, lung cancer shows an in cidence significantly below its expected values. By comparison among different exposure classes as shown in Table 9, the ratio of observed to expected deaths from respiratory cause constantly increases w ith increasing exposure because of the excess of pneumoconiosis in people w ith great est exposure. An increasing trend is also shown by larynx can cer but the number of cases is too small to assess significance of comparison. For all malignant neoplasms, oesophagic and gastric cancer as well as for tuberculosis and senility the ratio decreases w ith increasing exposure but no significant values are obtained in any cell to refuse the hypothesis of no d if ference among the three groups. No clear decreasing or increasing trends are detectable for all other causes of death in miners. Millers show an observed number of deaths below its ex pected values for cardiovascular diseases (Table 8). As shown in Table 10, for all causes of death there are no consistent relationships between the ratio and the exposure level. Considering the trend of mortality by cause and by in terval between first exposure and death all malignant neoplasms and lung cancer decrease in miners w ith increasing latency (see Table 11) as opposed to respiratory diseases as a Table t -- Miners a*4 Milton -- 0bsenr*4tipectad D e lta aad Ratio* by C a m (by Eiposed n . Control* Companion). Casato Onta Tturata (ad sita espi casa rasentati tti siiicais) Raaoiratory disaasa (all tuxpt patoneary tuberaiteij) Raspirstary diseasa. anta SHtcotabarata li Raspiratory distai**, dtraaic Otbar intoetrais d in a MikgRiat Mopttsim HaUcnMt neoplasmi, laryiti btodeunt neoplasmi. Ioni bioacbat and tra diti M iip iit neoptasms. pteun (masotbetioma) HabfMat naopiasms. ooopbafai HtlifMMt neoplasmi. stomac Mabfaaat neoplasmi, intestina Mabftuot naopiasms. bear (pnmary site or matastasas) Mab|aaat naopiasms. otbar sita Nonne! System disusa CardMacular disttses Oifastiie oriaa disama Senility Scadenti Ab olba esosa Unlumen Ulnari O bi./tip. 45/49.4 140/101.8 45/44.7 62/30.9 18/9.1 15/17.1 13/17.5 100/129.5 675.3 9/19.7 -/0.5 15/11.9 28/28.3 13/16.4 6/7.5 23/39.9 9/9.9 208/275.1 49/59.1 12/11 687164 7 23/33.5 37 Ratto 0.91 1.38+ 1.01 2.01+ 1.98+ 0.88 0.74 0.77+ 1.09 0.45+ -- 125 0.99 0.79 0.80 0.58+ 0.91 0.75+ 0 83* 1.09 1.05 0.69+ URtof* Obft.,tip. 12/14.0 25721.4 10/31.6 3/2.1 2/1.0 10/5.7 2/3 5 42/45.8 71.1 4/5.5 ffl.5 7/52 7/10.8 5/5.1 9/72 10/9.4 4/2.5 72/92.0 20721.8 4/4.8 28/26.7 979.8 9 Ratto 0.86 1.17 0.86 1.43 2.00 1.49 0.57 0.92 -- 0.62 -- 1.35 0.65 0.78 125 1.06 1.60 0.78+ 0.92 0.87 105 0.92 Statistically significant at 5% level "Statistically significant at 1% level Journal of Occupational Medicine/Vol. 18, No. 3/March 1976 189 w hole w hich significantly increase w ith increasing latency. We should underline that for silicosis w ith or w ithout tuberculosis, the ratio shows unchanged values over time because of the ab sence of pneumoconiosis in control sample (see computation of expected deaths), but the number of observed cases shows a constant increase w ith increasing latency, w hich explains the excess in ratio for all respiratory diseases. As shown |n Table 12 for millers only one pattern emerges: the ratio for gll tumors increases w ith increasing latency, but the number df observed deaths remains less than expected in any cell. Two cases of pleural mesothelioma were found in controls death certificates, confirmed by hospital records, but no autopsy data were available to the investigators. The occupa tional anamhesis carried out w ith relatives has not revealed any exposure to asbestos dust. We should also underline that in both miners and millers a number of oesophagic cancer cases higher than expected was found, even if the small number cannot provide statistical significance to the comparison. Discussion On general grounds, differences between exposed and con trols mortality as w e observed could be due to several factors: (a) a biased selection of the exposed groups; (b) a difference in recordirtg mortality in the exposed and in the control groups; (c) the well known effect whereby occupational groups experience a lower mortality than controls taken from the general population because of a selection upon starting work; and! (d) a lack of comparability of the tw o groups. Cause () can be excluded because all the workers w ho have beeri enrolled between 1921 and 1950 and w ho have worked at least one year (therefore including a substantial number w ith a very long period of observation) were included in the study. Cause (b) seems very unlikely: methods of data collection on mortality were the same for the tw o groups (exposed and controls respectively) and in both groups a similar number of cases were lost to follow -up for reasons unrelated to mortality (as accidental destruction of record files at the local .City Hall registries, carelessness of clerical workers, etc . . .). Cause (c) is less easy to discard, although a definite in dication that it cannot provide the entire explanation for the higher mortality in control group comes from the uniformity of the mortality ratio during the observation period. Assuming that lower mortality of the exposed group is due to selection of more healthy individuals, the effect w ould have vanished after one or tw o decades: on the contrary it remains practically un changed for the w hole period of observation (see latency tables). Cause (d) could be the main contributor to the observed dif ferences. As already mentioned (section Data Collection) male controls were matched by age to exposed individuals and drawn from a population similar in economic and social struc ture and general habits. However, it could be possible that the matched population exhibits (for not easily understandable reasons) a constantly higher death rate in respect to the whole population of the Piedmont Region. But this is not easy to verify because of the lack (so far back in the past) of regional statistical data fit for this comparison. It may be concluded that exposed vs. controls comparison has to be taken w ith caution and not generalized as confident ly as if no doubt w ould exist on control group adequacy. However further insight, in accordance w ith exposed versus Table 1 -- Miners -- Obsnrvtd/fctpncted D uths ind Ratios by Cans (by lirtn m l Comparison). C m at Outs .1 Tuberculosis (ail sites ucopt casts associated with silicosis) Respiratory diseases (all euapt pulmonary tuberculosis) Respiratory diseases, scute Silicosis Shcotuberculosis Respiratory diseases, chronic Other infections diseases Mailpairt neoplasms Malignant neoplasms, laryas MattCMOt neoplasms, lure bronchus and trachea Malignant neoplasm, pleura (mesnthelioms) Maiifnot MoptoflB, otsophtgus Malignant nwpfasms, stomach Matignaat neoplasms, intestine Malignant naoplasro. bwr (primary site or metastises) MMigrant neoplasm, other sites Nervous system diseases CardiovMCutor disetm Digestive organs diseases Senility Accidents AR other causes Unknoam Eap. le n t 1 Obivfap. 17/14. 26/36.9 9/12.6 8/14.9 1/4.3 8/5.1 4/3.8 38/31.9 1/1.5 3/2.7 -- 6/4.8 12/9.2 4/3.9 1/1.6 11/8.2 3/2.8.. 66763.7 16/14.8 5/4 23/20.8 11/7.7 22 Rate 1.18 0.70* 0.71 0.540.23 1.57 1.05 1.19 0.67 1.11 1.25 1.30 1.03 0.63 1.34 1.07 1.04 1.08 1.25 1.11 1.43 -- tap. Level 2 ObsvCsp, 13/12.2 38/36.3 16/11.9 14/15.8 6/5.1 2/3.5 273.1 28/28.3 1/1.4 1/1.9 -- 4/4.5 7/7.6 4/3.4 4/2.1 7/7.8 2/2.3 71/57.9 12712.7 3/2.8 27/21.4 4/5.2 9 Rate 1.07 1.05 1.34 0.89 1.18 0.57 0.65 0.99 0.71 0.53 0.98 0.92 1.18 1.90 0.90 0.87 1.23+ 0.94 1.07 1.26 0.77 -- Esp. Laval 3 ObsvCsp. 15/18.6 76/57 1 20/20.8 0/31.6 11/8.6 576.1 7/5.2 34/39.5 4/3.1 5/4.4 -- 5/5.9 9/11.7 5/5.5 1/2.1 5/5-8 4/3.9 71/86.2 21/21.5 4/4.9 18/25.4 8/9.8 , 6 Retie 0.81 1.130.96 1.27* 128 0.82 1.13 0.86 1.29 1.14 0.85 0.77 0.91 0.48 0.74 1.03 082* 0.98 0.81 0.70 0.82 -- ` Statistically significant at 5% level +Statistically significant at 1% level 190 M o rta lity Study of Talc M iners and M illers/Rubino et al controls comparison, may be gained by the internal com parisons of groups of workers exposed to different cumulative dose-of inhaled particles and splitting total mortality by cause. For millers no clear dose-effect relationship shows up either for total mortality considered over time of latency, or for cause of death For miners the only one clear pattern emerges for respiratory causes of death: here, in spite of the lower overall mortality in the exposed group, an excess of mortality is present in the ex posed versus controls comparison and as an increasing mor tality with increasing dose and latency period. The trend of mortality from respiratory diseases in relation w ith dose and latency and the different incidence of silicosis respectively in miners and in millers, allow us to assume that inducing factor is silica rather than talc. The deficit of tumors in the exposed in respect of controls is supported by the absence of any dose-effect pattern and is more easily interpreted as just one aspect of the lower mor tality of the exposed group. The lack of lung cancer in miners is similar to that observed by several authors: Kennaway and Kennaway,12 and more recently Goldm an,'3 Ashley,14 En terline15 and Liddell'6 have found a strikingly low rate of lung cancer in coal miners. Gooding'7 has found an incidence of lung cancer of 0.5% in the autopsied cases among 592 coal ' Table 10. -- Milters -- Obsaryed/Cipectad Deaths and Its bos by Causa (by Internal Comparison). Cote 1 Otate Tatarateas (ab atas ncapt casa associatati nith silicosis) Rsspiratary distorts (all cscapt putemiary tutaraitoso) Respiratory diseases, ta ta Silicosis Stati tatamitoerr Respiratory diseases, chronic Other infectious diseasa Matineet neoplasms IIta p eat taepitsms, iaryn Hetifmat naoptasms. lout bronchus and trachea Klinesat aeeptosim, pitara (mtaoteatiouia) Msttfstut MOfritsm, oesophttvs UtfifDMt ntopItsoB, stomach Makpiaat aaoptasms. intestine MsbcMOt neoplasms. liver (primary site or iw tis titts ) Mahfiiaat naoptasms. otear sita Nervteis system itistew CtrdiovMcuttr dtsetses Difettiva o rti disossa Senility Acoden Al other causa . tinlunero Esp. Lasel 1 Obsjtep. 5/4.2 11/9.9 4/3.7 1/1.1 -A0.4 8/4.7 2/1.1 18/16.5 -- 3/1.8 -- 4/3.4 3/2.7 2/1.8 -I2 A 6/4.4 2/1.5 28/26.6 7/7J 2/1.8 15/11 3/3.5 9 lata 1.19 1.11 1.08 0.91 .-- 1.28 1.82 1.09 1,67 1.18 1.11 1.11 -- 1.36 1.33 1.05 0.96 1.11 1.36 086 Esp. Latti 2 ObuEip. 6/4.5 9/6.9 5/3.7 2/0.6 1/0.9 1/1.7 -70.4 13/9.7 -- 1/0.8 -- 2/1 2/1.7 1/18 3/1.9 4/3.1 -/0.7 20/15.2 4/4.3 2/1.6 7/8.3 3/2.7 -- Ratte 1.33 1.30 1.35 3.33 1.11 0.59 -- 1.34 1.25 2.00 1.18 0.83 1.58 1.29 -- 1.32 0.93 1.25 0.84 1.11 Esp. Latti 3 Obsjtsp. 1/3.3 5/8.1 1/3.1 IO.9 1/0.3 3/3.8 /0.5 11/15.6 latte 0.30 0.62 0.32 -- 3.33 0.79 -- 0.71 71.3 -- 1/2.4 2/2.6 2/1.9 6/4.5 12.9 2/1.8 24/30.2 9/8.7 70.6 6/8.8 3/2.7 -- -- 0.42 0.77 1.05 1.33 -- 1.11 0.79 1.03 -- 0.68 1.11 Tabte IL -- M inan -- Obsenrnd/Expetted Deaths by Intanai Batanan First Espadara and Oaate and by Selectad Cansad (by Espadad n . Contrate Comparison). Canta al Baste Maftpteet neoplasms M M ifuit neoplasms, larynx Mahfnot neoptasra. lung, bronchus sud tredici U senet Moptetms, oasopfcagos Maiicmt Moptems, stomach Mitignut neoplasma intestine ttatifnast neoplasms, liter (primtry sita or matastasa) Tataratotis (ad sites eacspt casa associated trite sdtcosn) Risendory dtaaaats (id except pulmonary tuberculosis) Respiratory diseases, scute Silicosis Slkxrtetarattosrs Respiratory diseases, chronic <20 O btain. latte 19/201 2/1.9 1/1.4 2/2.4 2/2.9 3/2.9 4/1.9 23/28.6 0.95 1.05 0.71 0.83 0.69 1.03 2.11 0.71 28/23.5 9/118 11/5.4 3/1.4 5/5.5 1.19 080 2.04+ 2.14 0.91 Latency yn. 2I4P O butip. latte 55/738 3/28 6/148 10/7.0 18/158 6/9.6 1/2.9 20/18.8 76/54.4 34/30.8 24/12.1 10/5.1 8/6.4 0.75+ 1.36 0.42+ 1.43 1.14 0.63 084 135 1.40+ 1.10 198+ 1.96+ 125 >4 OtajCip. Ratte 26/35.6 1/1.2 2/4.1 3/2.5 8/9.6 4/3.9 1/2.7 0.73* 0.83 0.49 1.20 083 1.03 0.37 272.0 36/23.9 2/2.7 27/13.4 5/2.6 2/5.2 1.00 1.51+ 0.74 2.01+ 1.92 038 'Statistically significant at 5% level +Statistically significant at 1% level Journal of Occupational Medicine/Vol. 18, No. 3/March 1976 191 miner? in Sputh Wales, w hile D oll,18 in reviewing all the autopsies of male subjects in general hospitals in England, has found an autopsy lung cancer incidence of 6.2%. No risk of ex cess of lung cancer was detected by Waxweiler9 examining death certificates of potash workers. Therefore bur findings are in accordance w ith the hypothesis that lung cancer is unrelated w ith underground mining, in ab sence of specific cancerogenic agents (radon daughters, asbestos, haematite). Oesophagic cancer has shown an incidence in exposed groups higher than expected, although not statistically signifi cant. This needs further studies at a more advanced status of the follow-up. In conclusion exposure to silica in talc mines increases the risk of deafh from respiratory causes. No increase of risk is detectable for other causes of death in miners nor for any cause of death in talc exposed millers. W hile Kleinfeld's Study provides evidence of cancerogenicity risk when talc mining or m illing is a source of asbestos ex posure caused by fibrous contamination, our conclusions sup port the thesis of no cancerogenic effect attributable to pure talc. From these considerations emerges the definite indication that adequate environmental analyses must be performed in case of exposure to talc19 to assess the possible presence of fibrous materials contamination and to provide in this last case to an adequate prevention. Appendix Results of mineral samples examinations and of environ mental determinations are reported in this Appendix. Mineralogical Examinations A greatly detailed report on minerals coming from the mines and the mills of Val Chisone was carried out by Dr. Pooley* in 1972. The examined samples included footwall contact rocks, rock type inclusions, carbonate, calcite and magnesite inclu sions and talc specimens from mines as well as talc powders from mills. Specimens were examined by optical and electron microscopy and by x-rays diffraction. For specific results of each examination we should refer to complete text. However, patterns emerging from the con clusions of the authors are the following: Footwall contact rocks are mainly composed of mineral quartz, muscovite, chlorite, garnet, some carbonate material both calcite and magnesite and other materials in minor amount. Rock type inclusions in talc have similar composition to footwall rocks. In few specimens of footwall rocks as well as in inclusions Tate U. -- M ite l -- ObsaradtetncM Dutks by Ite ra i M m First Espuara a rt O tte a rt by S tectrt Causi (by Esposad . Catete Coartar*). te 4 M b ttii^paat Noplasot . a d ^ m t niqptifmi. Iirym Matitnaat Moptasan, taut tendas tod t r a t e Mtfcfoat teptawB. sophayas M tte w t naoptasms, nomadi Maipuat naoptasma, te s tili M tH firt Moptatan. te r (primary sit or Atestas!) Tubarcatoni {aU te s rapt casts associated with silicosis) Haspatom distoma (ab scapt patently tobarcutasia) Raspiratery distami, acata S ilica SMcptateeata Raspiratory d itta s ti dtrooic Lataacy yn. <2R 20 40 >40 Obste*. M a O tite * M a (te te * Rate S/9.4 A m A 2/2.5 3/2.6 1/06 065 --1 -- -- 060 1.15 2.00 24/26.1 A.I in i 5/4.1 2/60 2/2.0 6/5.1 092 -- 067 162 063 1.00 1.1 10A06 A 3/4,5 2A.1 3/26 /0.5 2A6 067 -- 0.67 162 160 -- 165 6/8.9 067 6/4.0 1.50 A.l -- Vt.l 066 17A1.7 1.45* 1A6 063 4/6.1 0.6$ 6/5.0 160 /0.5 -- ' -A -- 2A6 165 1/06 2.00 1/0.5 2.00 1/0.5 2.00 A -- 2A 6 163 6/46 1.74 J06 -- * Statistically significant at 5% level Tatto a -- Out a rt F it* Court ai ti Various Oporatioas to tiw Mtoos aiti io ti If His. Average of mppcf in the years within each period +tjtot measurable Data not available 192 M o rta lity Study of Talc M iners and M illers/Rubino et al of rock and carbonate a little amount of tremolite was detect ed. Nejther ofher types of anphybolic asbestos nor chrysotile were detected in any amount in rocks and in inclusions. Talc specimens were found very comm only contaminated by chlorite. No anphybole or chrysotile minerals were detected in any of the examined talc specimens. Free silica content in this talc is discussed-, by x-ray diffrac tion neither Parmeggiani in 1948,20 nor Rubino in 1963,21 nor Pooley in 1972 have found detectable free silica amount (quartz peaks) in mineral talc powdered specimens. By con trast an x-ry diffractogram performed by Jerry Krause (Colorado School of Mines Research Institute-- Personal com munication in 1974) on samples of commercial Val Chisone talc powder hs shown a minor amount of chlorite and quartz plus very m inr to trace amount of magnesite and dolomite in addition to ta|c. This could be due to some microinclusions in talc, observed also by Pooley, which, as well known, are not even detected, and then eliminated, by means as pre-milling photoelectron screening useb in Val Chisone mills. Analytical examinations conducted by G rill22 on mineralgi ca! composition of rock strata in Germanasca Valley have shown that is Jiot possible to state an average value for quartz amount in foofwall rocks. This value can vary in a range which is assumed by Parmeggiani in 194820 to be from 10 to 25%. Rubino21 has ihdicated an average amount of 45% in the strata mined in 1963. Environmental Determinations Environmental data were available for mines and mills since 1948. In sampling and measuring airborne particulate contami nant, termic precipitator and optical microscopy for dust count were used until 1964: these measurements were performed by the mining company. Since that year determinations were carried out by the De partment of Occupational Medicine, Turin University, using membrane collection technique and optical microscopy Conditions in microscopy examinations were the following: enlarging 500 x, transmitted light in phase contrast for free silica, polarized and dark field for fiber count. The trend of Workroom air total dust in respirable range (0.5 - 5 pas defined by British Medical Research Council criteria) and expressed in mppcf is visualized in Fig 1 for the w hole period of observation of the exposed workers. The trend was obtained by linking the points corresponding to the dust levl in the years in w hich air dust determinations were carried out. As no changes modifying the environment occurred before 1950, dust level in the years 1920 - 1950 was assumed to be qniform and equal to that of 1948. The decrease of dust content from 1950 to the actual values in mines is due to the successive applications of means of technical prevention w hich can be summarized as follows: Period before 1950 was characterized by dry drilling and the absence of any forced ventilation system. Since 1950 wet drilling was introduced and more w idely ap plied in the follow ing years. Forced ventilatory system was applied in the years 1958 1959 by air introduction and consequent dilution of dust until 1963 and by complete exhaust system after that year. It should be noted parenthetically that adoption of preven tion means was encouraged by the law n. 198 of March 4, 1958 on Rules of Policy of Mines, w hich establish in the mines Journal of Occupational Medicine/Vol. 18, No. 3/March 1976 a lim it of 650 particles (in the range 0.5 - 5 p ) per cubic centi meter (that is 18 41 mppcf) Actual values of dust level in the mills were obtained by successive improvement of dust suction systems. Table 13 shows a remarkable difference of free silica amount in air dust respectively in the mines and in the mills and w ithin the mines jobs between drilling and other operations. This is due to the high content of quartz in footwall rocks and inclu sions as opposed to the absence of free silica in talc minerals The small amount of free silica in mills operations is due, as above mentioned, to the actual incomplete screening of talc inclusions. The same explanation could be given for the very small number of fibers in air, caused by possible m icroinclu sions of rock containing little amount of tremolite. "A n examination of Italian Mine Samples and Relevant Powders" , |. Ughfoot, G. A. Kingston, F O. Pooley, Department of Mineral Exploitation, University Col lege Cardiff, 1972 Acknowledgment The authors express their indebtedness to Dr Rodolfo Saracci for his assistance in data elaboration, to Dr. Alessandro Pauna, Dr. Paolo Vergnano. Mrs. Michela Ghignone and Ms. Piera Ghignone for their assistance in data collection and to Mr Mario Vallotti and Arnaldo Forneron for their program assistance References 1. 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