Document wrZ4pBgZZJkvYkXqBBzRpnV9o
A Mortality Study of Oil Refinery Workers
Cities Theriault, M.D., Dr.PH., and Lise Goulet, M.D-
Survival status of 1205 men employed for more than five years in a Canadian oil refinery in East Montreal, from 1928 through 19~6. was assessed and death certificates wore reviewed Expected numbers of deaths were estimat ed based upon age- and cause-specific death rates for the Province oi Quebec applied to person-years at work Oil refinery workers showed a standard mortality ratio lower than expected for all causes oi death (SMR = 78 43). Three cancers of the brain were found among young people who (hivl U'ss than 20 years since start of exposure. I his was
statistically higher than expected. Cancers of the digestive system, though not significantly higher than expecti'tl. re mained suspect of being associated with work. Ihere is a need to expand this research to other oil reimery workers.
Though processing in an oil refinery is carried out m
airtight compartments, the presence of hydrocarbons of nil kinds and the possibility of worker exposure to these i hemicalx at the time of sampling and maintenance rais es the possibility that cancers of occupational origin may appear in this environment.
Few epidemiological studies dealing with the health or oil refinery workers have been reported Mortality rates from genital cancers, lymphomas.1 cancers Ot the Diges tive system and lung cancers1 1 were described as con spicuous and appeared to be exposure-related, but thc*ir excess was neither large nor statistically significant and could have been a chance occurrence
Occupations other than those encountered in an oil refinery in which workers were ex|xosed to oil derivatives were associated, with the appearance of cancer Benz pyrene was associated with an increase in lung cancer deaths1 * * Benzene was suspected of inducing leuke mia 1 A high incidence of urinary bladder cancer among workers in the rubber industry led to confirmation ot a causal association between exposure to betanaphthylamine and urinary bladder cancer in man.'
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This mortality study was earned out in a Car..d..ir oi! refinery plant which has been :n operation ->;n< e yijK end which has had an average work torre of 7sf) men mc-r th-* years The purpose ot the study was to determine u c .in cer mortality among oil refinery worker ,v,n higher 'han expected.
Methods
Studv Population. -- Fhe -andy population i uprised
all men who worked at tin- ml mliuery t.n more ll. m t-c>-
years between the start of operations m IWH and i >.-r.-nhor 31, 107S
Survival Status. -- the survival status wav deie-mmed
as of December 31, 1070 The company turm l1 *he
name, date of birth, date ot employment, work term-re
tion date, last known addresi, the social insurance jr-(
unemployment insurance numbers, when known, a- .v. ,i.
as a classification ot workers according to type *>: woo
(operation, maintenance, or office work) A riet,- > I er-
vice tile showing in chronological order the m i uiieomiv
and the departments in whic h eac h person work,-, i......ig
his years of employment wav made aya.lable upon re
quest so that references couid be made to a w her, tuftvr
details were needed
People who no longer were in the company - employ
were traced through several means telephone .d-v in
quiries at the Motor Vehicle Bureau, the Qce-be: r-.i:11.
Insurance Board, the Pension Board, and the Ln.... um
rr.ent Insurance Commission and circular letteo
vsorkers Persons whose survival statu-> iouiri m: ; ,i-
cortained by a direct personal contact or thrnugi
r
family or friends, even though a c urrent addr,"
found in the registries, weri* convidered I*-: '
The list of untraced workers was linked to the d- r
titicates filed at the Quebec Population Kegwiic *
ther increase the number ot traced people Dea*`
rates were consulted and causes ot death were m d
according to the 8th Revision of the International ( aw*-
fication of Disease.
Expected Kumber oi Deaths -- A chart ot per'**" y *
worked was calculated' A man entered the * n..*- put
five years of work in the Oil refinery He remamei. .,<v*ier
observation to the time ot his death or Dec ere.-* it
Journal of Occupational Medicine/Vol. 21. No, 5/May 1979
THIS PHOTOCO?1;' CCvriitS WITH
THE 1578 COPYRIGHT LAW
e-x- A- . t
rjT'* OLI 6661
Table 1 --Distribution of 1205 Oil Relinery Workers According to Survival Status as olOeeember 31. 1976.
Table 3 --Distribution ol 1205 Oil Refinery Workers According to Survival Status and Dale ol Employment
Survival Status
Male Workers No %
Daio ol
Alive
Employment No
Dead No %
LosltoFollCw-Ul)
No %
Awe ueaa
Cause -rrwn
Ca-.se unknown k:$; i: *z ow-uo
907 103
104 4
190 i 705
o
q
`6 i;o
197b, whichever cume first For the years 1928 to 1%2, the expected number 01 deaths xxas based upon the ageand cause-specrtic death rates tor the Province of Quebec, 1951, while for the years 1963.to 1976, those of 1971 w ere used
c/i *cn?
*
'935-1937 27 3 0 1933 1942 46 i 1 ',43 '947 142 3 "
948 65? 232 ?: 3 '-53 '63` 35 ` <1 4
'958 'Hi l;53 '957
99 - 9 55 '0 5
'968 -97: 142 *5: to'ai gr,7
17 : *6 7
20 ' 8 5 31 2: 7 19 *
5' 2 19 3 23 ,1
*C3 'ZZ
3 8 8 25
36 Zv
3 7 'j
t
0"
`3 " j, *
-9 ,, * 6S
*7
between the observed and the expected numbers of deaths10
The influence ot time evolved between the start of ex posure and the cancer appearance was studied by divid ing the population into two subgroups, more than 20 years and less than 20 years of elapsed time between the date of employment and the time of death. Expected numbers of deaths were determined and the standard mortality ratios (SMR) were calculated for each sub group
The Uailur-tderer tost tor the ratio of a Poisson vari able to its expectation was used to test the differences
Results The Studv Population -- Table 1 shows the -urx.xai
status ot the people ot the studv population There were 1205 male employees vxhc worked tor more than ti\" years at the refinery Ot these, 190 men were considered lost to follow-up The studied group < omprised 1M1r. men or 84% of the total study population
Tables 2 anti i shoxs the distribution ot the empln\e*.x ' alive, dead or lost to tollow-up according to their birth
dates and their dates of employment The distribution or
Table 2.--Distribution of 1205 Oil Refinery Workers According to Survival Status and Birth Date.
Date ot Birth
'56C '364 ' 565-'889 '85C-'894 t 89b- S55 *903' `'Qu* '905 '909 S'O '9U 1915 '5'9
*925-1929 '950-1924 93b- 939 1940 '944 94;-'94S '950' `954 tfa
Alive
No. %
--_
2 07 1 C:
6 07
'5 7 '
38 4 7
44 4 9
i 0tv-<1
T. 7 0
u* 1 t ~
'34 4 8 75 6 3 99 i-. g 03 r 4
8 09 90' :C0
Dead No. %
2 '9 5 46 5 46 12 11 1 9 83 18 16 17 17 15 1 13 12 0 14 13 0 6 56 5 4S 1 09 1 09 ---- ----
'08 100
Lost to Follow-up No. %
_
----
2 11
C5 2 '1 5 26 * 7 8-9 13 6 8 37 19 5 48 25 3 36 18 9 13 6 B 10 53 6 32 ----
190 100
the lost-to-rollow*up men according to age and date or employment was similar to that of the regrouped alwe
and dead men The lost-to-follow-up group is therefore expected not to generate any bias in the overall result of the study
Mortalitv Among Oil Reriner\ Workers. -- There were 108 deaths m the employee population during the 4`t-xear observation period Ninety-one percent ot the oeath-198 men) occurred in the group ot emp.oxees who were oxer 40 years of age The person-years of exposure chart gen erated from, the study cohort is shown ,n Table 4
Table 5 shows the obserxed ano expected numbers ot deaths and standard mortality ratios according to th*time elapsed since start of exposure .Whereas the overall mortality is lower than expected among the ret.nerv workers (SMR = 78 43;, the SMR s for specm: causes, though sometimes differing from TOO, were not statistcally significant
When mortality is studied according to whether more
than 20 years or less than 20 years have elapsed between
............ .....
............. -..-----
i
Table 4 --Person-Years Worked by Time Period and Age (1015 Men who Worked tor Over 5 Years at the Oil Refinery).
|
Time Period
1926 32 1933-37 19j5 4? 1943 47 1948 52 '953-57
1958-62 1963-67 1968-72 1973-76 Total
20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 $0-64 65-69 70-74 75-79 804- Total
50 5 1 6 1 86 3 4 56 3 5
37 7
86 45 7 85 3 71 3 36 3 21 0 22 ' 9 8 i 2
O' 3
14 0 67 5 964 150 9 109 2 59 5 3' 3 27 9 10 ' 1 2
iue 0
'7 7 179 3 216 9 205 4 221 8 150 8 33 d 33 a 27 7 9 2 1 2
:Mre
32 3 243 2 448 9 421 0 281 8 241 6 156 8 78 5 31 8 27 8 43
1966 2
it 5 253 2 537 7 716 1 510 5 286 5 237 1 151 9 80 3 29 8 25 3 08
2655 3
171 178 5 560 9 715 4 777 7 511 5 263 0 223 2 145 8 73 4 '.7 8 14 3 08 3494 4
8 2 162.3 281 4 62i 7 725 5 774 4 494 a 252 5 205 9 1339 54 6 99 9 1 3734 4
0B 241 2 338 5 304 4 527 9 581 4 601 1 358 4 179 2 153 6 75 4 32 5 10 3 34Q8 7
114 2 1416 6 2572 1 3214 8 3194 1 2632 5 1893 5 1136 0 682 0 423 9 182 8 57 5 20 2 17545 6
1
| I 1
]
! 1 I 1 | j
368 Mortality Study of Oil Refinery Workers/TnSnault ana Soule!
OLI 6662
Table 5 --Observed and Expected Number ol Deaths and Standard Mortality Batso (SMRI Among O.i Refinery Workers (1928-1976) According to the Time Elapsed Since Stan ol Exposure.
Disease Category (ICDA*)
Ma.'qran; neoplasms i:40-209i
Centra- nervous system diseases i3;0-3d3, Cardiovascular cseases '390-458) Re$?'-a'sry svstem diseases 14b: 5`,9,. On?'- .9 svsiT d sease; i5?C 5'7j c=r -.Cuf na\ sys*e-. Cseases (580-607. Accidents a-u .-cence 00-999 Otne-s i ;;.tes COt 999-
-20 Years Since 1st Expos
Obs/Exp T
$MA
73 :-0 7;. i '9 05 57
or:
0*27
r:n-
rr
33'-'2 2z
73
;* t: r; s:
'Cdf5 17:7;
nrewatiOMi Cass (.mho* at o seases Eignrn ReviS'on
'Expected ceams Pasec on age specie death 'ates o! Quebec rraie^ :S;ai,si'ca. y s.grr.car:
+ 2C Years Since 1st Expos
Obs/Exp
$MR
8 20 IS
5 t9
O 3 65
4Q d2 55
53 93
5 d 79
59 93
7 'I- 9:
"5 57
-. * 17
1 5 35
'7 18:
5 5 73
59 15
7-u =5 dj
o' ij
-------------------------------
Total Obs/Exp *
78 54 .,
SMR 59 -5 * '
( iT t iV
1
i-J
35 * p *1
: : 64 3 : 7 26 7 j 90 : :7 7:
; j- : ' V
75 V ;. 25
d`:
Table 6 --Observed and Expected Number ot Deaths Due to Malignant Neoplasms and Standard Mortality Ratio SMR) Among Oil Refinery Workert According to Time Elapsed Since Start of Exposure.
Diseesi Category (tCDA*)
Nose, torctue ortK M40-t49j O'dfit'vesystem , 'oO 1591 Larynx lung, p eura (t60-163i Bone. Skin 1170-173) Kidney, gentta' .t85-169i Brain central nervous sytem (190-1921 leukemia lymphoma 1200 209) Other cance's
Ad neoplasms i '40-209)
-20 Years Since 1st Exoes
Obs/Exp. T
SMR
0,0 21
--
3'3 13 ' % 7?
G/t 80
--
0/0 23 0<G 58
--
--
3/0 46 t '0 50
652 17J
if r
0/1 08
--
7'8 36
83 73
*internanona. C.assif.cadon or Diseases. E'ghtn Revision t Expected deaths cased on age specie deair. rates ot Guecec mates
{Statistically signibcant
m20 rein Since 1st Expos.
Obs/Exp.
SMR
0/0 59 9-7 12 3'6 68 I/O 19 3/t 97 O'O 31 2/1 46 O't 67 '5'20 te
--
ikb *G
44 91
326 31 152 28
--
'36 58
--
39 '9
Total
Obs/Exp.
SMR
iVj .5
V. 'u 22
3/8 46
i/O 42
3-2 55
3 3 77
d/: 3b
0 2 95
25 28 54
H 1'
233 09 f7 64
36? 61 12/ "
-
39 2?
.
I 1
Table 7. -- List of Workers Who Died of Cancer (Among 1015 Men Who Worked tor Over 5 Veers at tha Oil Refinary).
No. Type of Cancer
1 Stomach (i5i)
2 Stomach |15H
3 Stomach (151) 4 Stomacn (151)
5 Rectum m 54)
6 Rectum (154)
7 Pancreas |157)
8 Pancreas (157)
9 intestinal 059)
iO Brain (13S)
M Lung|162) 12 Lung(162) 13 Liposarcoma of the legs (f 70)
14 PinsMlt! 118b) 15 Prost,.te (185)
16 Btodor H88)
'7 General lymphoma (200)
18 Mycogenous leukemia (205)
19 intestine 1153)
20 Bram ,19?)
21 Lymphosarcoma (200) 22 Pancreas it57) 23 Lung(1621 24 Intestinal (153)
25 Brain /191)
Age at Death
51
55
43 50 57
67
65
71
45
43
77
80
79 74
66
51
66
43
72 41
56 43 46
73 41
Occupation at the Refinery
Ma ntenance Maintenance Laccratory 0f.ee
Laocia'.xy
Operatcns Ma.n'enance Operations Mantenancs Ooeranons Maintenance ara otters Office Maintenance Ollue Mam'cn.inro Mam'erar.ce Mamtenanre Operations Operations and office Maintenance Office ana maintenance Maintenance Maintenance Office Maintenance.-operat'ons
Time Sapsed Between Starting Work 6 Death
V
24
33
2t
23
'3
'8
29
30
14
18
25
42
,36 :,lf
23
2l
25
13
36
13
29
25 20 40
19
tts. or Years of Service
i5 29 2: 23
IS 1;
23 5
U
6
153
to
w
ty
2'
20 3
28 12 29 19 8 28 18
Journal of Occupational Medicine/voi. 21. No. S/May 1979
i
I
|
369
OLI 6663
[In- hr*t exposure ,nitl thf ri.ito or death, thr "loss than 20
-ve.ir* mih f vl.irt nt i-vposiire group" h.is sliitislir allv *ig
nitirjnt I*jwor SMK s tor all causes ot death and tor the category cither diseases'' when compared with the
Quebec population In the 'more than 20 years since start of exposure"
subgroup, the observed numbers of deaths tor all causes do not ditfer from the expected numbers The SMR tor diseases or the digestive system 1520-577) is elevated but not enough to be statistically significant The SMR tor accidents and violence (800-899) is statistical signifi cantly lower than expected when compared with the Quebec population
Cancer Mortality. -- Table b shows mortality due to malignant neoplasms There is no significant difference in the total cancer mortality death rate between the refiners workers and the Quebec population (SMR = 89 29),
Three observations stand out of the detailed study of the various cancer types (1) Lung cancer was less fre quent than expected (3 vs 7 42). (2) Three brain cancers appeared in workers within an interval of less than 20 years since the start of exposure. This was unusual and showed an SMR ot 652,17 (3) Though cancers of the di gestive system were not statistically higher than expected (12 vs 10 22], an S\1R of 117 combined with an elevated number ot deaths aue to diseases ot the digestive systenr deserve turther attention
Table 7 gives the list of workers who died of cancer by type ot cancer, age at death, occupation, time elapsed between start ot work and death, and number of years of service Table 8 gives the distribution of workers who died of cancer bv occupational categories The occupa tional group "others" includes individuals who worked more than one ot the preceding categories There is no statistically significant difference in the cancer mortality between the three subgroups operators, office employ ees and maintenance workers.
Table S. --Cancer Distribution According to Occupational Categories
j |
Occupational Ciiegcnes
C3er3TC'S
C't csem; :yees
Ma -,t*ra*:e
Cne-s 'ced; '7
Sr-^'3
1
t
No ol Workers
c53
22:
12 7 C`5
No Ot NO ot Cancors Cancers Observed Expected* Cbs/Exp
i
- 29
. ~ ! * ` *.
--
*>:cc.,ec njT;e:s zmz r izt iz,.VK cea:* s ec -
Coe- a:.ai - 0 55 Cl - 3, 3 - 5:
I
i ! t
among workers exposed to hvdrorarbon*: *' Th-- smok ing history of the present workers was not known
The high number of deaths cajsed by disease and can cer of the digestive system organ* deserves particu'ar at tention. It is worth noting that similar observation* r:made in two prev.OuS mortalitv studies of oii retiner-, workers.1 1 A review of the detailed occupational hi*;-,rv of the persons deceased from these diseases did not le.id to the identification of a common exposure t< . ,i t hemn o* within the refinery Poorly documented data on the m.-i *
alcohol consumption could not account for `he two1 a*< * of cirrhosis of the liver among seven deaths due to rii* eases of the digestive system
The questions raised in this studs as to the presence <: an association between work m an oi! refiners and -he development of bram cancers and diseases or the riiges tive system will only find an answer bv extending the study to larger groups of Oil retmerv workers
`TV au'hor*
to
tV V :> c* Zr 'afeu*'- * a*;-1 - <5
.*j
i'jrr* Ijvdi vnivfcf'its and Dr jcan-Marc Fr**0!ii arc v.#i s.*'-j**' "~m
P'JOjiai.ur
Discussion The finding oi an overall mortality rate tor oil refinery
References
1 Cities W, Weaver SIS end 7aoe-'hav* ,R w -r .v,t\ - ,rl
petroleum rennets worker* The Amec,.in PetroVam. : * -'- '
>
workers better than that expected from the general popu- mgton D C . Medical Research Report, Vs t A "402 t_-
I
lation agrees with what other authors have found in simi-
2 Hams N ano Sravrakv K Ten-vearvan.-irr.iiirv stud. ........ . *
|
lar occupational mortality studies.1111 There seems to be
ir. a petroleum compins Sooets for Ep.ritan.olosic Research "c-'-.-r.1 Am; Cpidemiol 10b 244, 1974
a selective process by which healthy person* constitute
3 Weil CS. $mvth MF, and "Sale TW Que-: :or a
-1 me;: `r i
the employed portion of the population. This is rein carcinogen AM A Arch iCdHvg S 535-sa7 1352
forced bv the ract that it is the "less than 20 years since start of exposure group" which showed the lowest stan dard mortality ratios.
The occupational history of the three young workers
4 Hammond EC. Sei koit l|. Lawiner PL and SeiOTu r! mra.-t.-.n
Ot benrpv-ene and cancer in man Ann sv Acad *cr 271 V.u-124 it's
5 Do.: R Vessev mP, and Beasles Rv.P Morta'o. o- gas-mot**''
Final report oi a prospective studs Sr / t-.c vted 29 394-i,i 1972
6 Llovd JW Long-term mortalitv vtuev o: steeimo-xe-* Resc reer.
who died of brain cancer revealed that one of them was cancer in coke plant workers I Occup Meet 13 53-68 1971
assigned to the fire safety department, the second was a maintenance man in the furnace room, and the third, an operator in the heavy oil unit. No common exposure of
7 Vignjm EL Leukem.a a*socia'i`d wth oencene >-*.'"'jr(- 1" M
Acad So Z71 143-151. 1976
0 Ca*v RAM and tiorkor Mi 'uiww or the unn.i-i
I.'i
occupational di*ea*e ,n the rjboer irdu*trv m Englanc ann a.i..' /
j these men to a single or a class of chemicals could be Prev Soc Med S 39-50. 1954
I
identified which would have given clues as to what was
9 Hill ID Computinc man vt-a:* at n*k 3' I Prei Soc `-fen; 2b 1 2
associated with the appearance of these cancers. No obvious reason could account tor the low lung
134. 1972
10 Bailar ]C and tdeter F Sign-r.rare e i.i-.-to'* sr ,L|*- mVi ' i
Poivain variable io itwopevta'itm Biometrics 20 bt'Wt !'-*
cancer death rate among oil refinery workers either.
11 And.elkovic , Ta*.i0ee and Svmom M Mortalitv tiper e-1 * >>
Other authors have described elevated lung cancer rates a cohort ot ruboer worke-s, 1964-1973 / OccjP Med 18 (87 394 f'"n
370
t
i`
Mortality Study of Oil Refinery Worke'S/Thfiriauit ard Gouiet OLI 6664