Document vVnkJxw3oLgLRK2O0wO5LyJOY

EXX-MOR-003130 AN ANALYSIS OF CANCER MORTALITY IN EMPLOYEES AND ANNUITANTS OF AN OIL COMPANY AND AN OIL PIPE LINE COMPANY DR, V. C. BAIRD Humble Oil if Refining Company ]. W. HAMMOND HumbU Oil if Refining Company DR. B. E. BENNISON Esso Research if Engineering Company Epidemiological studies of a group of fifteen thousand petroleum worken for a period of twenty-one yean reveal a lesser Incidence of cancer deatin than the general population In the same area. The relationship of occupation to the Incidence of certain types of cancer has been recognized by the medical profession for many yean. Among the flnt such reports waj In 1775, when Perdval Pott described scrotal carcinoma In men constantly exposed to soot. In 1915 Yomagiwt and Jchikowa reported that continuous painting of rabbits ears with tar led to the appearance of carcinoma. The similarity of the physical properties of crude oil and creosote oil, ( coal tar product) has led many Investigators to carefully study petroleum crude oil for the presence of carcinogenic compounds. The results of these investigators have been inconclusive, or without evidence of carcinogenicity. * New techniques in refining processes in the early 1940`s produced new compounds which have been shown to. have carcinogenic properties when applied experimentally to laboratory anlmali. *Thls makes It da* slrable to study the fnddenoe of tumor mortality in petroleum workers as compared to the general population. Epidemiological studies of employee groups offer one of the best methods of evaluating the relationship of a given occupation to the development of cancer.1 There are limitations In the accuracy of AM AXALTIIS OS OHCU UOtTAUTV tH tUHOUti, AHNUITAMTS Of AH OIL CWAHT studies based on information taken from death certificates generally." The United States Public Health Service has studied this problem in selected metropolitan M and rural areas.1 This Information la amplified by the experience accumulated by li/e insurance companies. Research by Industrial medical groups may augment these epidemiological analyses by studies on specific segments of the working population. We present, at this time, in analysis of the tumor mortality experience In a representative unit of the petroleum industry for a 21-year period ending In 1055. At present, Humble Oil & Refining Company and it's subsidiary. Humble Pipe Line Company, have a combined employee population of over 19,000 workers who have been engaged in the exploration, pro* duction, refining, transportation, and marketing of petroleum crude and its products in the Southwest portion of the United States. The death certificates for annuitants u well as employees. of this group were routinely subjected to medical review and verification. While no claim of 100% diagnostic accuracy Is made over this 21-year period. It is felt that the procedures used to Insure accuracy are either comparable to or better than those included In similar analyses elsewhere. We believe the first question of significance in an analysis of this type is whether the group of employees and annuitants studied shows an overall tumor mortality experience significantly different from that of the general population in the states from which the group was drawn. Because the employees under study In this analysis have gradually In creased in number during the period of observation, for the purpose at hand, the average yearly number of employees and annuitants is used. In the 21*year period extending from January 1, 1955 through December 31, 1955, there were 179 cancer deaths reported in a population which averaged 15,257 annually. This ij equivalent to an overall cancer death rate of 55.9 per hundred thousand per year. (Table 1) Since this represents an Integrated rate for the 21-yeer period, it Is best compered with public population figures reported around the midpoint of the period, i.e., 1945. This is a valid comparison as can be seen by examin ing the increase in United States cancer mortality rates durtog the period under review. This increase (i approximately a linear one. 41 I E PO 03 023 THI MlMCAL iVUXTIM AM AMAATSiS W CAMCIA MOatAUTT IM tidnCTIU. AMHUftAXTS OS AM ML CCM4PAHT COMPAilISON OF CERTAIN TUMOR MORTAUTY RATES* Rale Frequency Death rate (or canoer, all forms, (or U. S. - IMS 131.7, per 100,000 per year Arkansas 78.7 Louisiana 97.2 Oklahoma 102,1 Texas, Humble Companies, employees end ennuitents 68.0 55.9 TABLE I "Figure* (or U. S. and 4 sUtei reduced by Vfa to correct for tumor mortality 0 -20 year age group. = Tbo compeilsoD Is further supported by teldng into account the fact that the employee population U over 18-20 yean of age. The traditional method of applying a correction would be to use age specific death rates. However, with only 179 case* distributed Into five or six age decades, the groups would become so small as to reduce the statistical significance of comparisons. For this reason we have corrected for that percentage of the total tumor mortality which U experienced by the tge group 0-20 years. The best Information for this correction Is provided by Public Health Service Monograph #29*, which shows.', the percentage distribution of cancer by age groups (or the year 1947.;. From these figures, we calcu* , late that approximately 2% of the tumot mortality In the general popu lation was experienced by the age group 0*20 years. Another significant feature In (his overall comparison Is the geo graphical distribution of cancer deaths. In this connection, tbe area of Humble Companies' operations is that portion of the United States Identified by the National Office of Vital Statistics rj West South Central, comprising the stales of Arkansas, Louisiana, Oklahoma and Texas. The fact that tbe cancer death rate in the employee and annuitant population studied Is well within "normal limits* suggests that the mag nitude of any potential carcinogenicity problem which may be present Is not sufficient lo affect the overall rater. Another very general type of comparison that may be useful is the proportion of the total deaths that are due to tumors, l.e., the commonly used figure of relative fre quency. It is again apparent that by a second generally accepted yardstick, Humble Companies' overall tumor mortality experience does not significantly differ from that of control groups. These figures are presented In Table H. In addition, the "length of service* tor tbe group u a whole averaged 19 years, a period which may encompass at least a proportion of the latent period of any occupational associated lesions. RELATIVE FREQUENCY OF CANCER DEATHS Area Total Deaths* Tumor Deathsf U. S., 1945 Arkansas, 1945 Louisiana, 1945 Oklahoma, 1945 Texas, 1945 Humble Companies 1,258,744 13,203 19.888 16,991 52,850 1,481 173,015 1,457 2,333 2,171 5,891 179 TABLE II Percent 10.8% 11.0% 11.7% 12,8% 11.1% , 12.1% * Reduced by 10.2% to correct for the mortality occurring in the age group 0 - 20 yean. I* \ tReduced by 2% to correct for Lhe tumor occurring in the age group 0-20 years. If a positive correlation existed between occupation and tumor mortal ity, one might expect it to appear In organ systems most directly exposed to environmental agents. These would Include the sldn and the respira tory tract With reference to ikin cancer, the data on mortality rates and relative frequency are summarized iu Table III. < The respiratory tract would appear to be a logical target tissue for hypothetical carcinogenic factors related to occupation.. It will be useful, Iherefore, to compare tbe Humble Companies' respiratory tract tumor mortality with other experiences. This is done in Table IV. MORTAUTY EXPERIENCE DUE TO SKIN CANCER AMONG MALES Group Sldn Canoes Deaths/100,000/Yr. Humble Companies Employees and Annuitants (1935-55) Arkansas (1945) Louisiana (1945) Oklahoma (1945) Texas (1945) Above States Combined United States (1945) 3.75 5.40 4.06 8.05 7.40 8.03 5:06 TABLE HI 41 I EMO 03 02 4 EXX-MOR-003131 thi Mto+cMi auurrm MORTALITY EXPERIENCE DUE TO RESPIRATORY TRACT CANCER AMONG MALES Croup Respiratory Tract Deathj/lOO.OOO/Yr. Humble Companies Employees and Annuitants (1935-55) Arkansas (1945) Louisiana (1945) i Oklahoma (1945) \ Texas (1945) Above States Combined United States (1945) TABLE IV ia.i 14.9 25.2 1-4.7 16.5 17.6 60.8 Having looked at overall rates and relative frequencies of tumor deaths, and having followed this with an elimination of these Indices as they relate lo neoplasHo lesions of the skin and respiratory tract, let's examine the effect of occupational grouping on these indices. Table V shows the overall mortality rates and relative frequencies for cancer deaths arranged by Humble Companies* major departments. Inspection of Table V shows that, in general, departmental grouping was not as* sodated with significant Increases in tumor mortality rates nor with in creases in the relative frequency figures. One group, exploration, de serves mention however. The cancer death rate for this group U not remarkable but it appears that, as judged by the relative frequency value, about twice as high a proportion of the deaths were due to cancer than in any of the other departmental groups. Note, however, that the TUMOR MORTALITY EXPERIENCE BY MAJOR DEPARTMENTS OF HUM&IE COMPANIES Anrui Nr*b&M Humble Pipe Line Gu*m D**Uv Tool Dntia Tt4kJ C-JTcrr D**t> DtalA Kata pn 100.000 RaU rr 100,000 P*T TT- r. Xilalirt rwrwaif Company 2373 38 307 736 76.3 10.4% Humble Oil & Re fining Company: Production Refinery Sales Exploration Total 4592 61 450 473 63.3 13.4% 6239 60 531 405 45.8 11.3% 743 0 82 526 57.7 10.9% 1050 11 45 204 49.9 24.4% 15257 179 1481 462 55.9 12.1% TABLE V AN AMA1TS8 Of CANCIX MOtTAifTT IN IMPtOVIU, AHHUftAHTS Of AH CHL COMPANY total death rate for this department is about half that of the other de partments. A relatively small number of non-cancer deaths appears lo have pushed tire relative frequency higher than would be expected on the basil of the cancer death rate. - Further light on the effect of departmental grouping.on these mortality figures is ihed by some other characteristics of the departmental groups which are shown in Table VI. Here, note that certain departmental seg ments have a less seasoned group of employees than otherr, with a spread around the 19-year average length of service ranging from 13 years in exploration to 23 years In Humble Pipe Line. In this oontwetion, it Is interesting and expected to note that the highest cancer death rate, 70.3, was in the Humple Pipe Line employees, tite group with the longest service. This is also the group with the oldest avenge age, by approxi mately 7 years. While the exploration group had a relatively low total death rate, the mortality experienced appears to hive occurred at a younger age although In smaller numbers. ADDITIONAL CHARACTERISTICS OF OCCUPATIONAL GROUPS Occupational Group Pipe Line Company Production Refinery Sales Exploration Total Average Length of Service 23 yrs. 21 yn. 20 yrs. 18 yrs. 13 yn. 19 yrs. Average Age at Death 55 yn. 1 50 yn. 55 yn. 54 yn. 43 yn. 52 yn. ' TABLE VI In looking at this 21-year experience, certain questions suggest them selves. Flnt, do oil company employees differ significantly from com parable segments of the general population and uveraU tumor mortality experience? The data says "no"; in fact, the group under study ap peared to show a favorable tumor mortality experience u compared with that of the public In areas from which they were drawn. In view of potential skin contacts with certain petroleum derivatives known to be capable of producing tumors in experimental animals, how does (he death rate from skin cancer compare with that of comparable segments of the general population? Here again our employee and annuitant population experience a rate at least as good or better than that of the population from wMch they were drawn. ii EMO 03 02 5 THI MIBKAl BUUrnH In view of the potential inhalation of vapors and fume* that may be present around manufacturing operations, bow does ibe death rate from respiratory tract canoer compare with that of . the general population? The respiratory tract tumor mortality rate comperee favorably with con trol groups. Although the relative frequency figure for this group of neoplastic diseases is somewhat higher than that of the general popula tion, statistical analysis Indicated that this difference was insignificant In addition to mortality rates, certain type* of potential occupational exposures may result In the earlier development of neoplastlo lesions In the group, although the overall final rates may be the same, la there any evidence that neoplastic dlseases.occur earlier In this group than In com parable segment* of the general population? Again, the answer is "no* In view of the different types of potential exposures that are possible fa refining, marketing, producing, I'and transporting petroleum products, are there significant differences In the experience of these broad depart mental categories of the employe! population? Humble Companies' data showed there were so significant correlations between broad occupa tional groups and higher tumor mortality experience. Because of their greater exposure. It is noteworthy that the refining group had the lowest canoer death rate and the next to the lowest relative frequency rate of any of the occupational groups observed. In the petroleum industry, as in the chemical and other related In dustries, considerable attention has been devoted to possible relation!hipi between occupational exposure and neoplastic diseases. The introduc tions In UH2 of catalytic cracking in the petroleum Industry, stimulated continuing research and preventive effort The data presented above suggests that this effort may have been a successful one. BIBLIOGRAPHY 1 fsw. R- C., I. P. Holt, et all 5ympc*Jujn cn Cuwer Control Program lev Otk ARCH, IND. HYG. 4 OCCUP. MED, fi. GJtkam, A. C.i Opportunities for AppUcatioo of Epldemlolofla Method to Study of Ctocw. AM. j. PUBLIC HEALTH, 43jU47-57 (October. 1653). * 9fJRrH.fy.aDd /. L Horn: Tbs Reliability of CeittAratas of Death from Caacxr. AM. f. HYC., 54:13-13 (1041). Wilder, C. S.j Eavtrc*unaUl Canoer Id Canoecticuli II. DUTereocet to leddenec Ctwv* Axeoaf Ana*. Com. Health BulL, 70:143-150 (June, 1654). " p**? H. F.j end S. J. Cothrt Morbidity from Caacer la Ihs United State*. Put *: Variation In Incidence by Ata, Seat. Rice, Martial SUlui, and Geographic Rekia. Public Health Mpoofraph Nfc 30, 131 pp. (1655). Hasnnri, W. S., C. Marcui, and'M. C. Zltnmer Gances Morbidity la Uibas and Rural loan. Public Health Monograph No. 37, 55 pp. (1655). FORMS, INTERVALS BETWEEN EXAMINATIONS, WHAT SHOULD BE INCLUDED . Dn. RUSSELL G. BIRRELL Imperial Oil Limited Toronto, Canada When developing the forms and procedures for the inedic&J examina tion of prospective and regular employee, a great deal of time and effort was spent in reviewing forms In use by.:our:own and other com panies. Consideration had to be given to the great: distances, variation In concentration of Company population, and availability of well-trained. Interested Internists. Finally, our. forms and-a "Guido for Medical Ex aminers" were approved. The forms have been revised once, and & revision of the "Guide for Medical Examiners" is under consideration. The completed forms axe kept in our Health Centres. Where examina tions are being arranged outside tho Company Health Centres, (he ap plicant or employee is given forms, with certain portions completed by management, as well as a jell-addressed stamped envelope. The class!Bcatlon on preplacement examination Is sent to management; the other forms come, to the Medical Director or to the Regional Health Centre coo oeroed. Ail applicants for employment, except short-term temporary help, are examined completely. We examine applicants for summer or seasonal employment They account for much of our turnover. We have seen serious conditions, requiring Immediate medical care or restricted work, even in college students who have regular examinations at the beginning of the school year. During one summer season, we found two cases of active tuberculosis among sons of our own employees, one of whom had been brought a great distance but who had not been examined until oiler he made the trip. Our Medical Examination Record (foroi Med. 17) haj parts, I, II, 111, IV, and V. In addition, a family and personal history sheet, and a sum mary sheet, are used in our Health Centres. Physicians' Examination Summary cards (I.3.M. card 90133) are used lo record the results of the examinations and for statistical work. - r E f-U 0 j 026