Document 5LpbQpx1M7g7YDj84djO84oE0

ST0005329 A STATISTICAL EVALUATION OF RESPIRATORY SYSTEM INDICATORS AMONG PIPE CQVERERS____________ MGOtt INTRODUCTION This report presents statistical findings developed from an epidemiologic study of pipe eoverers. The report does not include a review of literature on the subject or a medical interpretation of the results. In the location under study, the job of pipe coverer has existed since 1910. A list of 173 men who have held this job was prepared from company personnel records. Virtually all men who worked on the job for at least a year are included in the list, as well as most of the men who worked less than a year. As of January 1970, the status of the 173 men was as follows: Still Working For Company 130 Active Pipe Coverers 94 No Longer Pipe Coverers 36 Quit or Released From Company 18 Retired "tt* \\ Deceased |H Within the identified exposed-to-risk population, the relationship between time-on- job and health indicators reflective of the well-being of respiratory function was investigated. The health indices examined in this study include (1) the mortality rate for cancer of the respiratory system (based on company insurance records, 1940-1970; (2) the incidence of morbidity episodes involving diseases of the respir atory system (based on company insurance records, September 1969-August 1970); and, (3) vitalometer measurements (derived from a multiphasic health screening program, 1967-1970). METHODOLOGY Selection Of Exposed-To-Riak Population And Controls Pipe coverers were identified through personnel lists prepared on a monthly basis by the company. The personnel lists are ordered by department and job classifi cation within department and are retained as far back as the 1920's. However, only the January listings are retained beyond ten years. Since pipe coverers tend to remain on the job for a long period of time, this method is adequate for identifying the exposed-to-risk population. Two sets of controls were utilized in this study. The first set of controls consisted of the total plant population and the second consisted of pipe fitters. While the total DOW CONFIDENTIAL DOW 06637 ST000S330 - 2- plant population was selected for. convenience, a probability sample of the pipe fitter population was selected because these men had-jobs-ciosely related to the pipe coverers except for exposure to asbestos. The pipe fitters were identified by the same method as was used ta-fdehtify-the pipe coverers. Because there are many more pipe fitters than coverers, a thirty percent sample was drawn By terminal digit sampling of company identification numbers. Method of Morbidity Analysis For the purpose of this study, a morbidity episode is an absence characterised by the filing of a proper accident and sickness benefits claim covering a continuous period of absence from work. The claim includes a physician's certification of the medical cause of the absence. In most cases, the morbidity episode must extend beyond seven calendar days before a record of the event is created. The program, as such, is available to hourly employees of the company. The expected number of disability days shown in Tables 1 and 2 are based on a five year age grouping of data on over 3,000 hourly employees. Method of Vitalometer Analysis The company's multiphasic screening program, offered on a voluntary basis, call for F.E.V. Total and F.E. V. 1 See measurements to be recorded for each partic pant. A Collins Vitalometer produces the tracings which are digitized by a tech* nician. For analysis purposes, the most positive of three repeated tracings for each individual is computerized. A regression equation was developed from the total screened population to adjust for height and age. Monthly comparison of measured results has shown that, over the three years of the program, consistent readings have been obtained. Using data generated through a multiphasic screening program has the advantage that neither the subject nor the technician is aware of uses to which the results might be put. Participation in the health inventory program was about 67% during the first cycle of the program. By combining first and second cycles, vitalometer readings were obtained for 101 men in the pipe coverer population. Several selection factors which could bias somewhat the findings of this study should be noted. First, it was not feasible to follow up on the 18 employees who left the company; two of these men were known to have left because of poor health. Secondly, a morbidity study covering a period two years following the first cycle of the multiphasic screening program revealed that participants in the program experience fewer illness-absence episodes than non-participants. The study did not enable us to determine the reasons for this difference. DOW CONFIDENTIAL DOW 06638 ST000533I -3 - While the same seleetioA factors apply to the control populations, caution must be exercised in interpreting results because of these unknowns. Method of Mortality Analysis The mortality analysis is based on copies of death certificates received by the com* pany Group Insurance Department as proof of death. As mentioned previously, individuals released from the company, excluding retirees, will be lost to a mor tality study based on insurance records. The two control groups referred to in Table 6 were studied over a more recent time period than the pipe eoverers, even though the first twenty years following initial placement on the job was not accumu lated as part of the exposure-to-risk. years for pipe eoverers. However, since the mortality rate due to cancer of the respiratory system has been increasing over the years, this comparison should error slightly on the conservative side. The mortality rates for the three groups were calculated on an age-adjusted basis: =t: Smoking History A smoking history collected as part of the multiphasic screening program was not judged as satisfactory for use in this study. The set of questions concerning smoking history has been restructured and appears to be producing results that can be useful in the future. The lack of smoking history does impose considerable limitations on the conclusions that can be drawn from the study. RESULTS Table 1 shows that while no pipe fitter employment groups differ from the total plant in disability days due to respiratory disease, there are differences among the pipe eoverers. The largest difference occurs among pipe eoverers with 10 years or more of continuous employment on the job. These differences, however, are not fully reflected in total disability days. In Table 2, the number of episodes involving respiratory disease are compared. Based on a poisson approximation test, significant differences between observed and expected episodes were found for three employment groups among the pipe eoverers and for no pipe fitter groups However, the significant differences in the continuously employed group might be expected to carry over to the total group. Vitalometer Analysis The readings shown in Table 3 are height and age corrected. Only after ten years of employment do significant differences between corresponding groups of pipe eoverers and fitters appear. The prior-to-employment group consists of men who worked at other jobs during the first cycle of the multiphasic screening pro gram and later became coveTers or fitters. A non-linear regression equation DOW CONFIDENTIAL DOW 06639 -4- was developed for F.E,Y. Total and F.E. V. l.See using years since first exposure as a pipe coverer for the independent variable. The regression lines, along with the scatter plot of individual readings, are shown in Figure 1 through Figpre XV for both fitters and coverers. Mortality Analysis All causes of death among pipe coverers up to 1970 are listed in Table-5* These deaths are categorized by interval between initial employment as a pipe coverer and death, and by length, of employment as a pipe coverer. An excess of total deaths and respiratory cancer deaths among pipe coverers, as compared to two other groups, is indicated in Table 6. The number of observations |s quite small. In addition, two of the men dying from respiratory cancer, also worked with lead arsenate. SUMMARY The data presented in this study were derived only from ongoing routine functions of the company Medical Department. The investigation of vitalometer readings, morbidity episodes due to respiratory disease, and mortality due to respiratory cancer, indicated that pipe coverers performed less well than did the comparison groups. There are two important limitations of the study aside from the size of the exposedto-risk population. First, no smoking history was obtained. Second, follow-back of individuals no longer with the company was not undertaken. m soooi! DOW CONFIDENTIAL DOW 06640 MGOtt Table 1. DISABILITY DAYS*1* PER PERSON PER YEAR AMONG PIPE TITTERS AND PIPE COVERERS ACCORDING TO LENGTH OF EMPLOYMENT CAGE CORRECTED). Employment as a Pipe Fitter Continuous <10 Years 10 Years or more Both Continuous and Non-Continuousft) <10 Years 10 Year* or more Pipe Fitter* Number, of Men*12*3 4 Total Disabilitv Days ... Observed Exoecte<frV Disability Days Due To Respiratory Disease Observed Expected 56.3 34.5 5.8 8.4 0.8 1.4 9.3 12.6 1.7 1.9 58.3 6.7 8.5 0.8 1.6 12.1 12.2 1.-4 1.9 > ji Employment as a Pipe Coverer Continuous <10 Years 10 Years or more Both Continuous and Non-Contin uous <10 Years 10 Years or more Pipe Covereri Number of Men -- -- Total Disabilitv Dave Observed Expected Disability Days Due To Respiratory Disease Observed Expected 57,0 33.7 8.0 8.8 2.1 1.5 13.8 13.0 7.4 1.9 70.1 57.0 12.6 8.5 4.7 1.4 11.9 12.7 5.0 1.9 (1) Disability days include non-working days. The analysis period is from September 1969 to September 1970. (2) Number of men take on fractional values because some men may have retired or quit the company within the study period. (3) Expected values are calculated from the total plant experience and are age-corrected. (4) This category includes men who may have worked for several years as a fitter or coverer and then changed jobs within the company. DOW CONFIDENTIAL JSTOO05333 DOW 06641 10-13-70 MGOtt Tablf 2. DISABILITY EPISODES DUE TO RESPIRATORY DISEASE AMONG PIPE-FITTERS AND PIPE COVERERS. Eznnlovment Continuous <10 Years 10 Years or more Both Continuous ind Non-Continuous <10 Years 10 Years or more Number of Episodes PiDe Coverer Pfoe Fitter Observed Exoeeted Observed Expected 9 14** 5.4 3.7 5 5.T 2 3.7 16** 14** 6.4 6.2 5 5.3 5 7.3 Significant at .01 level. There were na statistical differences between expected and observed episodes among pipe fitters. ST0005334 DOW CONFIDENTIAL DOW 06642 10-13-70 MGOtt Table 3. VITALOMETER READINGS FOR PIPE COVERERS AND PIPE FITTERS BY EMPLOYMENT CATEGORY BASED ON HEALTH INVENTORIES,--------------------------------------------------------------- Employment Category Total Prior to Employment Continuous Employment <10 Years 10. Years or more Pine Cover*>re F.E.V. F.E.V. PiiPC--Elite n________ F.E.V. F.E.V. Nbr. Total 1 See. Nbr. Total 1 See. 101 3.87 3.31 Ill 4.13 3.60 20 3.90 3.38 14 4.03 3.67 21 4.17 3.58 3Q 3.76** 3.28 24 4.14 34 4.12 3.62 3.51 <10-Years 10 Years or more 27 4.10 3.61 27 4.14 54 3.75** 3.23** 70 4.15 3.63 3.57 (X) Years are calculated from date of first exposure regardless of the duration of employment. **Mean value for Pipe Coverers significantly different than mean value for Pipe Fitters at the . 01 level (Student's -t Test) ST000S335 DOW CONFIDENTIAL Ej^urt Plot of FEMjtoUl. rcacfi'ings .poy 9*7 pipe. /Vyr ^i&.SSrs/L.x,'f>foy.H*efltar~JLS.iiijL}U^Qjt^ajiJ. _JbcijfvLcorreAiJjk v.i " i "' ; : . - F..v( *! EST0005336 _Vjrtal--------------------------- ofe^>A4 -w r;A * 3 H----- F.'jjurfc .SimtitxJl o t of. ECV^LSt^--TMJ.l*j s .ak .' 7 7-^aiyLi____ C i*nfrf___hy yn fj_jJ* gif f>Vf t *to>p)oy me n ds o f/Hfyfajf 1a*A Kfi^Kt lorrtcftj )______ DOW 06645 'W 'r 'VPTi Table 5. CAUSES OF DEATH BY YEARS WORKED AS FIFE COVERER AND BY INTERVAL BETWEEN INITIAL EMPLOYMENT AS A FIFE COVERED AND DEATH. (BASED ON DEATHS REPORTED THROUGH SEPTEMBER 1972) fAWtC Interval Between Initial Employment A Pipe Coverer And Death 0-9 Years 10 19 Years 20 - 29 Years 1 30-39 Years Yrs. Cause of Death Yrs. Cause of Death Yrs. Cause of Death Yrs. Cause of Death 2 Ca. Rasp.* 14 Myocardial Infarction 6 Suicide 29 Ca^ Respu, _ _ 27" Ca. Rasp. Post Op. 24 Ca. Rasp. 22~ Faill"At Work" T(T Aortic"* Mitral Valve Disease_ 12 Ca^ Fancreae_ "6" Coronary " _0cclusion_ _ "l" Ca^ Respj. _ __ Ti" MyocTrdlal"In* ' farction (Fibrous adhes ions of apex of left lung) *** ; 1 1 m*|ui |ur ii H CSj. Resp^ _ _ C*j_ Esopha&uj* Arteriosclerotic _RimlJDisease__ Had previously spent 1*1/2 years in Pb Arsenate 19 years prior to death. **Had previously spent 3 months in Pb Arsenate 29 .years prior to death. ***Had previously spent 1 year in Pb Arsenate 27 years prior to death 1 Mesothelioma sot included In above population--Died 1970--Worked grinding asbestos pipe cover to make "cement" for about 1 year (1945?). ST0005338 Table 6. OBSERVED DEATHS FOR PIPE COVERERS BEGINNING AT 20 YEARS AFTER INITIAL EMPLOYMENT VS. EXPECTED DEATHS BASED ON TOTAL PLANT POPULATION AND U.S. POPULATION MORTALITY RATES (ADJUSTED FOR ACE DIFFERENCES). Total Deaths Ca. Resp. Other Ca. Pipe Coverers* 1930 - 1969 13 6 2 Total Plant 1954 - 1969 5.9 .6 .9 U.S. Population 1966 7.6 .5 1.0 Over 91 percent of the exposed-to-risk years occurred after 1953. DOW CONFIDENTIAL DOU 06646