The Brazilian cohort of pulp and paper workers:
the logistic of a cancer mortality study
C o o rte b rasile ira d e trab alhad o re s de ind ústria
d e c e lulo se e p ap e l: a lo g ístic a d e um e stud o
d e mo rtalid ad e p o r c ânc e r
1 De p a rt am en to de Me d i c i n a S o c i a l , Fa cu ld a d e d e M e d i c i n a , U n i ve r s i d a d e Fe d e ra l d e Pe l o t a s . C . P. 4 6 4 , Pe l o t a s ,R S 9 6 0 1 0 - 1 6 0 , Bra s i l .
An a cla u d ia Ga st a l Fa ssa 1
Lu iz Au gu st o Fa cch in i 1
Ma ri n el M ór D a ll’Agn ol 1
Abstract Th e In t ern a t i on a l Agen cy fo r Re s e a rch on Can cer (IARC) p rop osed t h is i n t ern a t ion a l h ist orica l coh ort st u d y t ryin g t o solv e t h e co n t rov ersy a bou t t h e in crea sed risk of ca n cer i n t h e w o rk ers o f t h e Pu lp a n d Pa p er In d u s t ry. On e o f t h e m o st i m p ort a n t a sp ect s p resen t ed b y t h i s st u d y in Bra z il w a s t h e st ra t egies u sed t o ov e rcom e t h e m et h od olo gi ca l ch allen ges, su ch a s: d a t a a c c e s s , d a t a a ccu ra c y, d a t a a v a i l a b i l i t y, m u lt ip le d a t a sou rc e s , a n d t h e la rge f ollow -u p p eri od . T h ro u gh m u ltip le st rat egies it w a s p o ssible t o bu ild a Braz ilia n coh ort of 3,622 w ork e r s , t o follow t h em w i t h a 93 p ercen t su ccess ra t e a n d t o id en t ify in 99 p ercen t o f t h e ca ses t h e ca u se of d ea t h . T h is p a p er, h a s ev a lu a t ed t h e d a t a a ccess, d a t a a ccu ra cy a n d t h e eff ect i v en ess o f t h e st ra t e g i e s u sed a n d t h e d ifferen t sou rces of d at a .
Key words Ep i d e m i o l o gy ; C o h o rt St u d i e s ; Dat a Sou rc e s ; Ne o p l a s m s
Resumo A Agên cia In t ern a cion a l p ara Pesqu isa sobre Cân cer (IARC) p rop ôs u m a coort e h ist órica in t ern a ci o n a l p a ra t en t a r re s o l v er a con t rov érsia sob re o risco a u m en t a d o d e câ n cer em t ra -b a l h a d o res d a s i n d ú st ria s d e celu lose e p a p el. Um do s a sp ect os m a i s re l e v a n t es d est e est u d o n o Bra si l re f e re-se à s est ra t égia s u t i liz a d a s p a ra su p era r d esa fio s m et od oló gicos, t a is co m o: a c e s s o a os d a d os, a cu rá ci a e d i sp on ib i lid a d e d o s d a d os, m ú lt i p la s fon t es d e da d o s e lon go p erí od o d e a c o m p a n h a m e n t o. At ra v és de m ú lt ip la s est ra t é g i a s , fo i p ossív el con st ru ir u m a coort e b ra s i l e i ra d e 3.622 t ra b a l h a d o re s , a com p an h a r 93% d os casos e iden t ifica r a ca u sa d e 99% d os óbit o s. Es t e a rt igo a v a li a o a ce sso a os d a d os, su a a cu rá ci a e a e fet iv id a d e da s est ra t égia s u t iliz a d a s p a ra o a com p a n h a m en t o da co ort e .
Cad . Saúd e Púb lic a, Rio de Jane iro , 14(Sup. 3):117-123, 1998
I n t ro d u c t i o n
Th e ca n ce r r isk in t h e Pu lp a n d Pap e r In d u s t r y h a s b e e n co n t rove rs ia l. Ch lor in e c o m p o u n d s a re so m e o f th e m ost im p o r t an t ch e m ical su b -st a n ce s s u sp e ct e d t o b e ca rc i n o g e n i c. T h e st u d ie s alrea d y d on e h ave su gge ste d a n e xc e s s of ce rta in ca n ce rs, e sp e cia lly lu n g can ce r, m a -lign an t lym p h om a s, b u t for m ost p a rt , t h e y a re i n c o n c l u s i ve w it h re g a rd t o co n s id e ra t io n s o f e t io lo gic age n t s (Bo ffe t t a e t a l., 1991; To ré n e t al., 1996).
T h u s, th e In t e rn a tio n al Agen cy for Res e a rc h o n Can ce r (IARC) d e cid e d t o p e rf o rm t he Mu l-t icen l-tric In l-t ern a l-tion al Co h orl-t Sl-tu dy of Wo rk e r s in th e Pu lp a n d Pa p er In d u s t rywh ich in clu d e d 18 c o u n t rie s (Bo ffe t t a e t al., 1991). Th e a im o f t h is p ro je ct w a s t o in ve st iga t e t h e m or t a l i t y a n d ca n ce r m o r b id it y in p e rs o n n e l e m p loye d in p la n t s p ro d u cin g p u lp , p a p e r a n d p a p e r p ro d u c t s, an d in m ills in vo l ved in th e re c yc l i n g , in re la t io n t o sp e cific p ro ce sse s a n d c h e m i c a l e x p o s u r e s in t h e s e in d u s t rie s (Bo f f e t t a e t a l., 1991). Th e h ist orical co h ort was p la n n ed to fol-l ow m ore t h an 100,000 worke rs (W H O, 1995).
Th e Braz ilia n Co h o rt is p a rticip a t in g in t h e m o rt a lit y st u d y wit h 3,622 wo rkers o f o n e Pu l p a n d Pap er In d u s t r y. Th e st u d ie d in d u st ry is o n e o f t h e 10 b igge st in Bra zil p ro d u cin g 300,000 t on s pe r yea r of p u lp a n d 2,000 to n s p er year o f p a p e r w it h a Kra ft p ro c e s s. Th is is o n e o f t h e fir st h ist o ric al co h o rt st u d ie s ca rr ie d o u t in Brazil an d o n e of th e fe w w hich ha d com p let ed t h e follow-u p wit h an a ccep t ab le lost .
Th is stu d y is sign ifica n t b ecau se o f m e t h o d -o l-o gica l c h a lle n ge s, su ch a s d a t a a c ce ss, d a t a a c c u ra c y, d at a ava i l a b i l i t y, m u ltip le d ata sou rc e, a n d t h e lar ge fo llo w-u p p e rio d . Th e la c k o f m o d e ls in t h e c o u n t r y a n d t h e la c k o f e xp e rie n crie o f t h rie r rie s rie a rch t rie a m wit h t h is s t u d y d rie -sign we re also im p o rt a n t ch a lle n ges.
To p e op le in t e re st e d in le a rn in g m o re a b o u t h ist o r ic a l co h o r t st u d ie s, o r t o im p le m e n t t h e m , it is in s t r u c t i ve t o e xam in e in d e -t a il -th e m e-t h od o logy an d o p e ra -tio n al issu es o f p re viou s st u d ie s (Bre s l ow & Da y, 1987). Co n s i d e r in g t h a t , t h is p ap e r d e s cr ib e s th e st r a t e -gie s u s e d t o co m p le t e t h e fo llow -u p o f t h e Bra zilia n Co h o r t , a n d d isc u ss e s s o m e cr i t i c a l issu es to ca rry ou t a hist orical co h ort stu d y.
M e t h o d o l o g y
The Brazilian cohort
Th e Bra zilia n co h o r t in vo l ve s b lu e a n d wh it e -co lla r wo rk e r s, b ot h s exe s, wit h a m in im u m of on e yea r con t in u ou s em p loym en t in th e in d u s-t ria l are a of a Pu lp a n d Pa p er In d u s s-t r y, w ich is lo ca te d in a c ity n e arb y th e ca p it a l o f t h e st a t e of Rio Gran d e d o Su l.
Th e e xp o sit io n p e r io d o f t h e c o h o r t go e s f rom Ju n e 1969 – wh e n t h e in d u st r y st a rt s – t o De ce m b e r 1991. Th e wo rke rs d ism isse d b efo re Ma rch 1972 we re e xclu d e d , b e ca u s e a gre a t p a rt o f t h e m we re workin g in t h e co n st ru c t i o n o f t h e in d u st ry. Th e fo llow -u p p e r io d st o p s in De cem b er 1994 (Fi g u re 1).
L o g i s t i c
C o h o rt constru c t i o n
To co n st ru ct th e coh o rt , th e fo llowin g id e n tify-in g d at a we re co lle ct e d : w ork e r’s n a m e , n a m e of p are n t s, d at e o f b irt h a n d se x, an d th e occu -p a t io n a l d at a , su c h a s d e -p a r t m e n t , jo b t it le s an d d a t es of st a rt in g a n d e n d in g ea ch occu p a -tion a l p er i o d .
Th is in fo rm at io n w as e xt r a ct e d a t t h e in -d u s t ry fro m t h re e -d at a b a se s: t h e a rc h i ve s, t h e a c t i ve wo rke rs file s a n d t h e c o m p u t e r i ze d re c o rd s. Th e id e n tifica tion d a t a wa s co m p u te r-i ze d t o b u r-ild t h e lr-ist o f wo rkers a n d t o st art t h e vit al sta tu s id en t ifica tion . Th e list allowed u s to ch e c k t h e w or ke r s wh o h a d b e e n e m p loye d m o re th an on e tim e to jo in t h eir d a ta .
Fo u r re s e a rch a s sista n t s h ad wo rke d in t h e c o h o rt co n st ru c tio n fo r t wo m o n t h s. Afte r t h is first d a t a co lle c t io n , it w a s re a l i ze d t h at t h e p a re n t s’ n a m e s we re n ee d ed t o lin k t h e id e n t ifica t ion d a t a wit h o t h e r d a t a b a se s. O n e re s e a rc h a s sist a n t c o lle ct e d t h is e xt ra in fo rm a -tion in six m o n t h s.
Vit al stat us identification
Electoral Court searc h
a n d s e n t t o t h e El e c t o ra l Co u rt . Th e w o rk e r s’ n a m e , p a re n t s’ n a m e s a n d d a t e o f b ir t h we re u se d b y t h e El e c t o r a l Co u rt t o ch e ck t h e d a t a -b a se of th e sta te o f Rio Gran d e d o Su l. It id e n ti-fie d t h e wo r ke r s t h a t we r e alive, so m e re c e n t d e at h s a n d t h e o n es wh o we re n ot o n th e re g i s-t e r s. A n u m b e r of vo s-tin g re g i s s-t ra s-tio n s we re n o s-t u s e d b e ca u se it h a d c h a n ge d in 1986, a n d fo r t h e m ost p a rt t h e wo rke rs with vo tin g re g i s t ra -t io n n u m b e r s in -t h e in d u s-t ry re c o rd s we re -th e old o n es.
Th e El e c t o ra l Co u rt co m p le t e d t h e s e ar c h in six m o n th s.
Identificat ion, at t he industry, of the Vo t i n g Registration Emission Place and the curre n t number of the voting re g i s t r a t i o n s
For t h e wo rke rs wh o we re n o t in t h e El e c t o ra l Co u rt re c o rd s, t h e y w e re id e n t ifie d a t t h e in -d u s t r y, a n -d t h e Vo t in g Re g i s t ra t io n Em i s s i o n Pl a c e . Also t h e vo t in g re g i s t ra t io n t h at h a d t h e c u r re n t n u m b e rs we re se n t t o t h e El e c t o ra l Co u rt , wh ich d id a n e w s e a rch . O n e in d u s t r y w o rke r wa s p a id b y t h e re s e a rch t o d o t h is s e a rch ove rt i m e . It to o k o n e m on t h.
I n f o rmation from professionals of the i n d u s t ry ’s health center and from workers employed at the industry for a long time
Re s e a ch e rs a ske d th e p r o fe s s ion a ls o f th e h ea lt h cen te r an d t h e wo rkers th a t h ad b e e n a t th e in d u str y fo r a lon g t im e to loo k a t th e list of w o rke rs t h a t we re n o t o n t h e El e c t o ra l Co u r t re c o rd s a n d if th ey kn e w, t o id e n tify t h e ir vit a l s t a t u s.
Household search in the city where the industry is located
Th is sea rch wa s d on e fo r th e 329 wo rkers re g i s-t e red a s-t s-th e in d u ss-try w ho we re livin g in s-t he cis-t y w h e re t h e in d u stry is lo ca te d .
Fi ve p e o p le we re se le c t e d fro m t h e cit y w h e re t h e in d u str y is lo ca te d t o d o t h e sea rc h . If t h e wo rke r or h is (h e r) fa m ily we re livin g a t t h e a d d re s s, t h e vit a l st a t u s wa s id e n t ifie d . If t h e re wa s an oth er p erson livin g cu rren tly at th e a d d re s s, t h e y we re a s ke d , o r t h e ir n e igh b o rs we re a ske d if t h ey kn e w a n y in fo rm a t ion con -c e rn in g t h e wo rk e r’s wh e re a b o u t s. Pe o p le liv-in g liv-in t h e c it y fo r a lo n g t im e u p d a t e d t h e n a m e s of t h e s t re e ts t h a t h a d b e e n c h an ge d . Th e h ou se h old se a rch to o k two m o n t h s.
Phone search at t he city were the indust ry is located and at the state capital
A p h o n e se a rch wa s d on e in t h e cit y wh ere t h e i n d u s t r y is lo c a t e d a n d a t t h e s ta t e c a p it a l. A s im ila r se a rc h w a s d o n e in t h e c it y w h e re t h e i n d u s t ry is, in t h e ca p it al of st a t e, an d in sm a ll c it ie s a ro u n d t h e ar e a . It u se d t h e wo rk e r’s n a m e , t h e fa m ily n a m e a n d t h e a d d re s s (in c lu d in g n e igh b o rs) t o se a rch t h e p h on e n u m -b e r s. At le as t o n e n u m -b e r w a s t rie d fo r e a c h o n e o f t h e 165 wo r ke r s se a rch e d , b u t in s o m e ca se s t wo o r t h re e p h o n e n u m b e r s we re tr i e d . On e re s e a rch assist a n t a n d t h e co o rd in at ion of t h e Bra zilian c oh o rt d id t h e id e n t ific a t io n o f t he ph on e s. Th e p h on e calls an d th e h o useh o l d s e a rch we re d on e sim u lt a n e ou sly.
Identification of the st ate to where the workers migrated: Electoral Court search in ot her states
T h r ou gh t h e in fo rm a t io n ga in e d d u rin g t h e h o u se h old se a rch an d from wo rkers e m p loye d at t h e in d u str y fo r a lo n g tim e, t h e p la ce of re s-id en ce was s-id en t ifie d for 24 wo rk e r s. Aft er th at , t h e El e c t o ra l Co u rt wa s a ske d t o s e a rch for t h em in t he registe rs o f t h e sp e cified st a te s.
S e a rch in the Death Registrat ion Office in the city where the industry is located, and in the oldest and largest Death Registration O ffice of t he capital of the st ate
Th e Dea th Re g i s t ra t io n Office of th e city wh e re th e in d u stry is located an d th e old est an d largest De at h Re g i s t ra t io n Office o f t h e c a p it a l o f t h e sta te we re se arch ed to fin d th e 297 lo st wo rk e r s wh o we re n ot fou n d t h ro ugh o t h er st ra t e g i e s.
F i g u re 1
De sig n o f the histo rical c o ho rt. Brazilian p ulp and p ape r stud y, 1998 .
F o l l o w - u p
C o h o rt Inclusio n p e rio d c o n s t ru c t i o n
1 9 6 9 1 9 8 1 1 9 9 1 1 9 9 4
Cad . Saúd e Púb lic a, Rio de Jane iro , 14(Sup. 3):117-123, 1998
In t h e De a th Re g i s t ra tio n Office o f t h e cit y w h e re t h e in d u st ry is locat ed , t h e d a ta h a d two t yp es of o rga n iza t io n : b ooks in o rd e r o f d at e o f d e at h wit h a n a lp h a b e t ic a l re su m e a t t h e e n d , a n d c a rd s in a lp h a b e t ica l o rd e r, b u t n o t ve r y w e ll o rg a n i ze d . Th e d a t a w a s n o t co m p u t e r-i ze d . On e re s e a rch a ssr-ist a n t t o o k 2 m o n t h s to d o t h e se a rc h .
In th e o ld e st an d largest Death Re g i s t ra t i o n O ffice a t t h e ca p it al o f t h e st a t e, t h e d a t a w a s c o m p u t e ri ze d . Th e wo rke rs o f t h e De a t h Re g-i s t ra t g-io n Offg-ice h a d d o n e t h g-is s e a rc h g-in o n e we e k .
Cause of D eat h Identification
Th e se a rch for cau se o f d e a t h was d o n e in t h e De at h Re g i s t ra t ion Office of t h e cit y wh e re t h e i n d u s t r y is lo cat e d an d in a ll se ven De a t h Re g-i s t ra t g-io n Offg-ice s g-in t he ca p g-ita l of t h e sta t e. T h g-i s s e a rc h wa s d on e fo r t h e 95 wo rke rs id e n t ifie d a s d e a d . Th e p ro ce ss t o o k o n e m on th . Ju st two o f th e De at h Re g i s t ration Office s we re co m pu t-e ri zt-e d , t h t-e o t h t-e rs wt-e rt-e o rg a n i zt-e d in t wo wa ys: a b oo k o rd e red b y d at e of d eath a n d card s in al-p h ab e tica l o rd e r. So m e De at h Re g i s t ra t io n Of-fic e s we re c o n t a ct e d b y p h o n e in o t h e r cit ie s w h e re so m e d ea t h s we re re g i s t e re d . Th e O ffice se n t u s a p h o t o co p y o f t h e d o cu m e n t s b y m ail o r fa x. Fo r t h e c a s e s t h a t t h e s e a rch in t h e De a t h Re g i s t r at io n Offic e s we re u n s u cce ssfu l, t h e fam ily wa s co n t act e d to ge t a p h o t oco p y o f t h e Death Ce rt i f i c a t e. Th e workers o f th e De a t h Re g i s t rat io n O ffic e s d id t h e se a rch o f ca u se o f d ea th an d on e re s e a rch assist a n t go t t h e De a t h Ce rt ifica t es with t h e fam ilie s.
R e s u l t s
C o h o rt constru c t i o n
It h a s id e n t ifie d 3,622 wo rke rs t h a t h a d b e e n w o rkin g in t h e in d u st ria l a re a fo r m o re t h a n o n e ye a r. It m ad e a carefu l search to exclu d e re-p eat ed re c o rd s, t o jo in co m re-p lem en t ar y re c o rd s, a n d t o p re s e rve t h e ho m o n ym o u s (Fi g u re 2).
Vital status ident ification
Electoral Court searc h
Fro m t h e list o f 3,622 wo rke r s o f t h e Pu lp a n d Pa p e r In d u s t r y, t h e El e c t o ra l Co u rt id e n t ifie d 81 p e rce n t alive, 0.3 p e rce n t d e a d a n d 19 p e r-ce n t w h o we re n o t in t h e ir re c o rd s. On r-ce th e El e c t o ra l Co u rt elim in a ted fro m t h e re c o rd s th e d e a t h s t h a t o ccu rre d s e ve ra l ye ar s a go, it wa s
id e n t ifie d re l a t i ve ly m o re wo rke rs a live t h a n d e ad . (Fi g u re 2).
Identification, at the industry, of the Vo t i n g Registration Emission Place and the curre n t number of voter re g i s t r a t i o n s
At t h e in d u s t ry, t h e Vo t in g Re g i s t ra t io n Em i s -sio n Pla c e wa s id e n t ifie d fo r a ll 19 p e rce n t o f th e lost wo rk e r s, b u t th e cu rre n t n u m b e r o f t h e vo t in g r e g i s t ra t io n s we r e a va ila b le o n ly fo r o n e p e rce n t o f t h e lo st wo rk e r s. Wit h th is in fo r-m a t io n , t h e El e c t o ra l Co u rt h a d d o n e a n e w s e a rch , id en t ifyin g 85 p erce n t alive, 0.3 p e rc e n t d e a d an d 15 p e rc e n t w e re st ill n o t in t h e ir re c o rd s (Fi g u re 2).
I n f o rmation from professionals of the i n d u s t ry ’s health center and from workers employed at the industry for a long time
Th is s t ra t e gy a llo we d u s t o id e n t ify 11 lo st w o rk e r s, six wo rke rs we re a live a n d five wo rk-e r s w rk-e rrk-e d rk-e a d . T h u s, t h rk-e p ro p o r t io n o f lo st w o rkers wa s re d u ce d t o 14.6 p erce n t (Fi g u re 2).
Household search in the city where the indust ry is located
Fo r t h e 329 wo rke rs re g i s t e re d a s livin g in t h e cit y wh e re t h e in d u s t r y is lo c a t e d , th e h o u se -h o ld s e a rc-h id e n t ifie d t -h e vit al s ta t u s o f 44.4 p e rce n t o f t h e m . Th is st r a t e gy d e cr e a se s t h e st u d y lo ss t o 10.6 p e rce n t (Fi g u re 2).
Phone search at the cit y where the industry is located and at the st ate capital
T h ro u gh t h e p h o n e list , it wa s s e a rch e d 165 w o rk e r s, id en t ifyin g th e vital stat u s of 44.8 p e rce n t of t h e m . Th e lo ss wa s re d u rce d t o 8.6 p e r -cen t b y th e p h o n e sea rch (Fi g u re 2).
Identification of the state for where t he workers migrated: Electoral Court search in other st ates
S e a rch in the Death Registration O ffice in the cit y where the industry is located and in the oldest and largest Death Registration O ffice of the capit al of the state
Th is st rat egy id e n t ifie s o n ly d ea d w ork e r s, re c-ogn izin g 25 p e rcen t of th e d e at h s in th e coh o rt . Aft e r t h is p ro c e d u re , t h e stu d y lo ss d e cre a s e d to 7.5 p e rce n t (Fi g u re 2).
Cause of death identification
De s p it e t h e d ifficu lt ie s in t h e De a t h Re g i s t ra -t io n O ffic e s a n d -t h e c o n s-t ra in -t s in a skin g -th e fa m ily fo r t h e Re g i s t ra t io n o f De at h , t h e cau s e o f d e a t h w a s id e n t ifie d in 99 p e r c e n t o f t h e cases ( Fi g u re 2).
D i s c u s s i o n
Aft e r fo u r ye a rs of d e ve lo p in g m u lt ip le st r a t e -gie s a n d u sin g a va rie ty of sou rce s we o b t ain e d th e su cce ss to con st ruct a coh o rt of 3,622 worke rs a n d t o fo llow t h worke m u n t il 1994 w it h a n a c -cep tab le lo st (Mo n son , 1990). Desp it e a ll lo gis-tical d ifficu lties, it was p o ssib le t o com p let e th e f o l l ow -u p o f t h is h ist o r ic a l c o h o r t s t u d y. As Bre s l ow & D a y (1987) m e n t ion e d , t h e su cc e ss wit h wh ich t h e fo llow u p is a ch ieved is p ro b a -b ly t h e -b a sic m e a su re of t h e q u a lit y o f c o h o r t s t u d i e s.
In Brazil, like o t h er co u n t ri e s, t he access to p e rso n a l d a t a is re s t ric t e d b y la w (He rn b e rg , 1992). Ho we ve r, t h is a c ce ss c a n b e fa c ilit a t e d t o re s e a rc h e r s, if e t h ica l re q u i re m e n t s a re o b -s e rve d . Thi-s -st u d y ob ta in ed a n e th ica l a pp rova l f ro m t h e IARC a n d t h e Et h ica l Com m it t e e o f t h e Fa cu lt y o f Me d icin e o f t h e Un i ve r s i d a d e Fe d e ra l d e Pelota s (UFPel), wh o con sid ere d th e re l e va n c e, t h e o b je ct ive s o f t h e s t u d y, an d t h e co n fid e n t ia lit y o f t h e d a t a . Th e in d u s t ry a n d t h e Ch ie f Ju d ge o f t h e El e c t o ra l Co u rt , t a kin g in t o a c co u n t t h e e t h ica l c om m it m e n t o f t h e s t u d y, a llowe d a cce ss fo r a ll t h e d at a . Fu rt h e r-m o re, as soo n as th e vita l st a tu s wa s id en t ifie d , th e wo rk e r’s n a m e a n d p are n t s’ n a m e s we re ex-clu d ed fro m th e d ata b a se. The grea te r p ro b l e m re g a rd in g a cce ss to t h e d ata wa s t h e re s t ri c t i o n t o d o q u a lit y co n t ro l in t h e se a rc h re a l i z e d b y t he El e c t o ra l Co u rt an d th e De ath Re g i s t ra t i o n O f f i c e s.
Th e lo gis t ic w a s fa cilit a t e d b y t h e size a n d lo c a t io n o f t h e in vo l ve d cit ie s. Th e s t u d ie d w o rke r s m o s t ly live d in t h e cit y wh e re t h e in -d u s t r y is lo ca t e -d o r in t h e ca p it a l o f st a t e . In m an y cases, in d u strie s a re loca te d in in d u stri a l a re a s wit h se ve ra l c it ie s o f d iffe re n t s ize s
a ro u n d wh e re t h e wo rke rs live. Th is c a n m a ke it im p o ssib le o r ve r y e xp e n sive fo r t h e h o u se -h old sea rc-h , a n d t-h e se arc-h in t-h e De at -h Re g i s-t ra s-t io n Office s, wh ich wa s e s se n s-t ia l s-t o re d u c e t h e losse s.
Th e m o s t im p o r t a n t p ro b le m t o d e ve l o p t h is h ist or ical co h ort wa s t h e d a ta q u a lity. Ge n -e ra l l y, s -e v-e ra l p ro b l-e m s ca n b -e fo u n d in t h -e d a t a b a se s a va ila b le in Bra zil, s u ch a s u n d e r re g i s t ra t io n , m issin g-d a t a a n d o u t d a t e d d a t a , o n ce t h ey a re co llect ed regu la rly for o th e r p u r-p o ses th a n re s e a rch (Sch illin g, 1986). Ho r-p e f u l-l y, th e sta te o f Rio Gra n d e d o Su l-l ha s o n e o f th e b est re giste rs in th e co u n try. Ot h e rw i s e, form a l w o r ke rs n e e d t o u p d a t e t h e ir re gis t e rs t o ge t n e w e m p lo ym e n t . Bo t h as p e c t s c o n t r ib u t e t o t h e d a t a q u ality o f t h e co h o rt .
O n t h e o t h e r h a n d , in Bra zil, e a ch p e rs o n h a s se ve ra l p e rso n a l id e n t ific a t io n n u m b e rs ,
F i g u re 2
Strate g ie s use d to fo llo w-up the co ho rt. Brazilian p ulp and p ap e r stud y, 19 98.
C o h o rt const ruction
(N = 3,622)
Vit al st at us ident ificat ion
Ele cto ral co urt se arc h
Alive = 2,939 De ad = 12 Lost = 671
Id e ntific atio n, at the ind ustry, o f the vo ting re g istratio n e missio n p lace and the curre nt numb e r o f the vo ting re g i s t e r s
Ele c to ral c o urt se arc h
Alive = 3,0 67 De ad = 13 Lost = 542
I n f o rmatio n fro m p ro fe ssio nals o f the ind ustry ’s he alth ce nte r and fro m wo rke rs e mp lo ye d at the ind ustry fo r a lo ng time
Alive = 3 ,073 De ad = 18 Lost = 531
Ho use ho ld se arc h in the c ity whe re the ind ustry is lo cate d (n= 329)
Alive = 3,185 De ad = 52 Lost = 385
Pho ne se arch at the c ity whe re the ind ustry is lo cate d and at the state c ap ital (n= 165 )
Alive = 3,2 41 De ad = 70 Lost = 311
Id e ntific atio n o f the state whe re the wo rke rs mig rate d: e le c to ral co urt se arc h in o the r state s (n= 24 )
Alive = 3,2 54 De ad = 71 Lost = 297
S e a rch in the d e ath re g istratio n o ffic e in the c ity whe re the ind ustry is lo c ate d and in the o ld e st and larg e st de ath re g istratio n o ffic e o f the c ap ital in the state
Alive = 3,2 54 Dead = 95 Lo st = 273
Cause of deat h id ent ificat ion (n=9 5)
S e a rch in the de ath re g istratio n o ffic e o f the c ity whe re the industry is lo c ate d and in all (7) d e ath re g istratio n o ffice s o f the c ap ital in the state
Ident ified = 94 No t id e ntifie d = 1
Cad . Saúde Púb lic a, Rio de Jane iro , 14(Sup. 3):117-123, 1998
wh ich m ake d ifficu lt t o lin k d iffere n t so u rces o f i n f o r m at ion (He rn b e rg, 1992). Wit h th e la ck o f a u n iq u e id e n t ific a t io n n u m b e r, t h e lin k wa s d on e u sin g th e wo rk e r’s n a m e, p are n t s’ n am es, an d d a te o f b irt h .
Th e d at a b a se o f t h e in d u st r y u se d t o c o n -s t r u ct t h e c o h or t h a d re l a t i ve ly a cc u ra t e d a t a o n id e n t ific a t io n a n d e xp o s u re o f wo rk e r s , w h ic h is e s se n t ia l t o t h e id e n t ific a t io n o f t h e vit a l st a t u s, a n d th e ca u se of d e a th , b u t also t o t h e d a t a a n a lys is (Sch illin g, 1986). On e of t h e fe w p ro b le m s fo u n d w as m iss in g d a t a re l a t e d t o p a r e n t s ‘ n a m e s . Ho we ve r, t h e lo s se s d u e t h is m is sin g d a t a w e re ve r y lo w (H e rn b e rg , 1 9 9 2 ) .
Th e El e c t o ral Co u rt was t h e cen t ra l st ra t e g y t o fo llow-u p t h e co h o r t , o n ce it id e n t ifie d t h e vit a l st a t u s fo r 81 p e rc e n t o f t h e co h o rt in t h e first se a rc h . Th e n , t h e o t h e r st ra t e gie s n e e d e d t o fo llow o n ly 671 u n id e n t ifie d wo rk e r s, in -s t e a d o f t h e wh o le co h o rt (3,622 wo rk e r -s ) n e e d in g t o b e d o n e. De sp it e t h is , t h e re wa s a re l a t i ve ly grea te r id e n tifica tio n o f livin g p eo p le in re lat io n t o th e d e a d p e o p le , b e c au se t h e El e c t o ral Co u rt d id n o t m a in ta in th e re c o rd s o f d e ce as e d p e o p le a lo n g t im e a go. Am o n g t h e u n id e n t ifie d w o rk e r s, t h e re we re d e ce a se d w o rk e r s, m igra n t s, or lost work e r s. Th is is a p o-t e n o-t ia l p ro b le m in a n y o-t yp e o f c o h o r o-t so-t u d y, p a r t ic u la rly t h o se in vo lvin g a lo n g fo llo w - u p p e rio d (Kle in b a u m e t a l., 1982).
Th e El e c t o ra l Co u rt u p d a t e d t h e ir re c o rd s b as e d o n t h e in for m at io n s e n t b y t h e D e a t h Re g i s t ra t io n Office s, b u t t h e y o ft e n d id n o t h a ve co n t ro l of t h e o n e s t h a t we re re s p o n s i b l e fo r t h is o b liga t io n a n d t h e o t h e rs t h a t we re l a t e.
T h u s, t h e re wa s a p o s sib ilit y o f fa lse livin g p e o p l e. To m a n a ge th is p r o b le m , it w as d ec id -e d t o w ait six m o n t h s fro m t h -e -e n d o f t h -e fol-l o w -u p t o t h e b e gin n in g o f t h e s e a rch . T h i s w a s d o n e t o a llow t h e De a t h Re g i s t ra t io n O f-fices t im e to sen d t h e d a t a of d eat h t o th e El e c-t o ra l Co u r c-t . T h e re is n o p o s sib ilic-t y o f fa lse d ead p e o p le, o n ce t h e d ea t h wa s co n firm ed by t h e Dea th Ce rt i f i c a t e. An u p -t o -d a t e d n u m b er o f th e vo t in g re gist e rs c ou ld b e ve r y u s e fu l in t h e vit a l st a t u s id e n t ifica t io n , m a kin g q u icke r a n d m o re p recise th e El e c t o ra l Co u rt sea rc h .
Th e id e n t ifica t io n o f t h e vit a l s t a t u s o f s om e wo rke r s b y t h e p ro fe ss io n als o f t h e in d u s t ry ’s h e a lt h c e n t e r a n d b y wo rke rs e m -p l oyed a t th e in d u st ry for a lo n g tim e wa s -po s-sib le b e ca u se th e y h ad a re la t ion sh ip with se v-e ra l v-ex-wo rk v-e r s. In so m v-e casv-es, t h v-e in form a t i o n a b ou t e x-wo rke rs was o b t ain e d wit h th e ir re l a-t i ves workin g aa-t a-th e in d usa-tr y in a-th e d a a-ta collec-t io n p eri o d .
Th e h ou seh old se arch an d th e p ho n e s e a rc h we re th e fir st te n t at ive t o d ep u r at e t h e gre a t e r c o n c e n t ra t io n o f d e a d p e o p le a m o n g t h e lo st w o rk e r s. On e p ro b lem in th is stra t egy wa s th a t so m e a d d r e s se s we re ve r y o ld . In t h e la s t t wo d e c a d e s, se ve ra l st re e t s ch a n ge d t h e ir n a m e s, an d se ve ra l p lac e s d id n o t e xist a n ym o re , like h o te ls a n d lod gin g h ou se s t h a t h ad b een closed or ch an ged t h eir fu n ct ion , an d h o useh o ld s th at ch a n ge d t o b u s in e s se s. Th e m o s t im p o rt a n t p ro b le m in t h e p h o n e se a rch wa s t h a t m a n y w o rke rs d id n ot h a ve a te le p h o n e an d t h at t h e wom e n te n d e d t o list th eir p h on e n u m b ers u n d e r t h e h u sb a n d ’s n a m e ( S c h o n o r r, 1993). De -sp it e th e se ob sta cle s, th e m e n t io n e d stra t e g i e s ove rco m e t h e e xp e ctat io n s. Th e y w e re a p p lied t o sixt y p e rce n t o f t h e lo s t wo rk e r s, a n d t h e y m a d e p o ssib le t o fin d a lm o st h a lf o f t h e co n -tact ed w ork e r s, re d u cin g t he losses by fou r pe r-ce n ta ge p oin ts.
Th e vit a l st a t u s of t h e id e n t ifie d m igra n t w o rke rs we re a lso m a d e b y t h e El e c t o ra l Co u rt of t h e stat e o f Rio Gra n d e d o Su l, b ecau se t h e y h a ve a c ce ss t o t h e re gis t e rs o f o t h e r s t a t e s. Howe ve r, th e El e c t o ra l Co u rt is a b le t o d o t h e s e a rch o n ly if t h e st a t e o f re sid e n ce is kn ow n . Th e cu rre n t n u m b er of t h e vo t in g re g i s t ra t i o n s cou ld h a ve e n la rged t h is typ e o f se arc h .
Th e la st st ra te gy t o estab lish th e vit a l sta tu s was t h e se a rch o f lo st w o rke rs in t h e D e a t h Re g i s t ra t io n Office s. Th is se a rch id e n t ifies ju st d e a d wo rke r s a n d co m p e n s a t e s t h e gre a t e r id en t ifica t ion of livin g p e o p le in re la tion t o t h e d e a d p e o p le in t ro d u ce d b y t h e first se a rc h at th e El e c t o ra l Co u rt .
Th e id en t ifica tion of t h e cau se of d ea th was d o n e b y t h e se a rc h in t h e De a t h Re g i s t ra t i o n Office s a n d b y th e collab ora tio n of so m e fa m i-l i e s. Th ese stra tegies we re ve ry e ffect ive o n ce it id e n t ifie d 99 p e rce n t of t h e ca u se s o f d e a t h . Th e u n id e n t ifie d ca s e wa s t h e o n e wh ich t h e ca u se o f d e a th we re n o t fo u n d in t h e se a rch a t th e Dea th Re g i s t ra tion Offices, t h e p la ce o f re g-i s t ratg-ion of d e at h wa s u n kn own a n d co m m u n g- i-cat io n with t h e fa m ily wa s n ot p o ssib le.
1989; H a l p e r in g e t a l., 19 96; He rn b e rg, 1992; Mon son , 1990).
Hi s t o r ica l co h o rt s o n m o rt a lit y d a t a m a y st ill b e u se fu l t o in ve st iga t e u n d isc ove re d o ccu p a tio n a l h a za rd s th a t a re fa tal. Th e m ost im -p o r t a n t st u d y lim it a t io n s a re re la t e d t o t h e q u a lity o f t h e in fo rm a t io n a n d t h e co m p le t e -n e ss o f t h e fo llow -u p (Bre s l o w & Da y, 1987; H e rn b e rg, 1992; Sch illin g, 1986). In t h is st u d y, th e select ed strat egie s m ad e it p o ssib le to id e n -tify t h e vit al st at u s o f 93 p erce n t o f t h e coh o rt , a n d alm ost 100 pe rcen t of th e ca u se of d e ath of t h e d e ce as e d w or k e r s, t h u s a ch ie vin g t h e re -q u i re d com p le tio n of th e follow - u p .
R e f e re n c e s
B O F F E TTA, P.; KO G EVINAS, M .; SARACCI, R. & VA I N I O, H., 1991. I A RC In tern ation al Coh ort St u d y on Ca n cer Ri sk Am on g Wo rk ers in t h e Pu lp an d Pap er In d u s t ry. Protocol of th e St u d y.Lyo n : In t e r-n a tior-n a l Age r-n cy fo r Re s e a rch or-n Ca r-n ce r (m im eo ). B R E S LOW, N . E. & D AY N . E., 1987. Th e ro le of co h or t st u d ie s in c a n c e r e p id e m io lo gy. In : St a t i s t i c a l M eth od s in Ca n cer Re s e a rc h : Th e Desi gn a n d An a lysis of Coh ort St u d ies (N. E. Br e s l ow & N. E. Da y, N. E., e d s.), p p . 2-46 . Lyo n : In t e rn a t i o n a l Agen cy fo r Re s e a rch o n Ca n c e r.
C H E CO K WAY, H .; PE A RCE, N. E. & CRAW F O R D -B ROWN , D. J., 1989. Co h o rt s t u d ie s. In : Re s e a rc h M eth od s i n O ccu p at ion al Ep i d e m i o l o gy ( H . C h e c o k w a y; N . E. Pe a rce & D. J. Cra w f o rd - Brow n , e d s. ), p p . 103- 169, N e w Yo r k: Oxfo r d Un i ve r s i t y Pre s s.
H A L P ERIN , W.; BEAU M O N T, J.; BROWN , D.; CLA P P, D.; HARING, M .; McCAMM ON , C.; M EINH ARD T, T. J. & OKU N, A., 1986. Th e co h o rt st u d y. In : Ep i-d e m i o l o gy of Occu p ation al He a l t h(M . Ka r vo n e n & M. I. M i k h e e v, ed s.), p p . 149-180, Co p e n h a g e n : World Hea lt h Org a n i z a t i o n .
H E R N B E RG, S., 1992. So u rc es o f in fo rm a tio n . In : In -trodu ction to Occu p ation al Ep idem iology(S. Hern -b e rg, e d .), p p. 39-59, Ch e lse a : Mich iga n Le wis Pu b l i s h e r s.
A c k n o w l e d g e m e n t s
Th is stu d y wa s su p p o rt ed by th e Fi n a n c i a d o ra d e Es-t u d os e Pro je Es-to s (FINEP – Co n vê n io 6694032100), Es-t h e In t e rn at io n a l Age n cy fo r Re s e a rch o n Can cer (IARC ) , th e Co n se lh o Nacion al d e D e s e n vo lvim en to Cie n t ífico e Te c n o ló giífico (CN Pq ) a n d t h e Fu n d a çã o d e Am -p a ro à Pesqu isa d o Rio Gra n d e d o Su l (FA PE RG S ) .
We a re gr a t e fu l fo r t h e co lla b o ra t io n o f t h e Rio -ce ll S.A.(p u lp a n d p a p e r in d u str y), t h e p ro f e s s i o n a l s o f th e in d u st ry ’s h e a lth ce n te r (M a rce lo Si l ve i ra a n d Ma ra Ch a ga s), th e Tr ib u n a l Re gio n a l El e i t o ra l d o Rio
K L E I N B AUM , D. G.; KUP P ER, L. L. & M ORG E N -STERN, H., 1982. Typ o lo gy o f o b serva tio n a l s t u d y d e s i g n s. In : Ep i d e m i ologi c Re s e a rc h : Pr i n c i p l e s an d Qu a n t i t a t i v e Meth od s ( D. G. Kle in b a u m & H. Mo rg e n s t e rn , ed s.), p p . 62-95, New Yo rk: Van No s-t ran d Rein o ld Co m p an y In c.
M ONSON, R. R., 1990. Th e co llect io n of e p id em io lo g-ic d a ta : re t ro s p e c t i ve co h or t stu d ie s. In : Oc c u p a-ti on al Ep i d e m i o l o gy(R. R. Mo n so n , e d .), p p . 51-56, Bost o n : CRC Pre s s, In c.
SCHNORR, T., 1993. Vid e o d isp la y te rm in a ls a n d a d -ve r se p r e gn a n cy o u t c o m e s. In : Case Stu d i es in Occu p at ion a l Ep i d e m i o l o gy (K. St e e n la n d , e d .), p p. 7- 20, Oxfo rd : Oxford Un i ve rsit y Pre s s. SCH ILLIN G, R. S. F., 1 986. So u rc e s o f d a t a . In : Ep
i-d e m i o l o gy of Occu p ation al He a l t h(M . Ka r vo n e n & M. I. M i k h e e v, e d s.), p p . 81-96, Co p e n h a g e n : Wo rld Hea lth Org a n i z a t i o n .
TOREN , K.; PERSSON , B. & WIN GREN , G., 1996. Hea lt h e ffect s o f wo rkin g in p u lp a n d p a p e r m ills: m align a n t d ise ase s. Am eri can Jou rn al of In d u s t r i-al Me d i c i n e, 29:123-130.
