Document M4noZ0b9orz7YkwpJ0D7BaeXk

FILE NAME: Avondale (AVD) DATE: 1968 Aug DOC#: AVD165 DOCUMENT DESCRIPTION: Article Presented at Annual Meeting of PNW Industrial Hygiene Association - Asbestos Exposure and Pulmonary X-Ray Changes to Pipe Coverers and Insulators at Puget Sound Naval Shipyard MD-006136 ASBESTOS EXPOSURE AND PUIMONARY X-RAY CHANGES TO PIPE COVERERS AND INSULATORS AT PUGET SOUND NAVAL SHIPYARD * C. A. MANGOLD, R. R. BECKETT, D. J . BESSMER I n d u s tr ia l Hygiana D iv isio n Pugat Sound Naval Shipyard BrasMrton, Washington August 1968 * The o p in io n s e x p re sse d in t h i s p ap er are Chose of Che a u th o rs and do not n e c e s s a rily r e f l e c t chose of che D epartm ent of Che Navy, che D epartm ent o f D efense, o r any o th e r o f f i c i a l agency. R eferen ce to a company o r a p ro d u c t name does n o t imply a p p ro v al o r recom mendation o f che p ro d u ct to th e e x c lu s io n o f o th e rs th a t may be su itab le. This paper for p re se n ta tio n a t the annual m eeting o f the P a c ific Northwest S ectio n o f the American In d u s tr ia l Hygiene A sso ciatio n a t R ichland, H ashington on October 3 - 4 , 1968. w ABSTRACT. A 2 -1 /2 y e a r com parison o f c h e s t X -rays of 6571 p ro d u c tio n w orkers and 420 c l e r i c a l w orkers a t Puget Sound Naval Shipyard show t h a t Pipe C overers and I n s u la to r s h an d lin g a sb e sto s have 21.27. diagnosed pulmonary a b n o r m a litie s as a group compared to th e n e x t h ig h e s t in c id e n c e o f 3.57. f o r b o ile rm a k e rs , w ith some a s b e s to s and s i l i c a ex p o su re, and le s s than 17. f o r c l e r i c a l w o rk e rs, w ith no known a s b e s to s ex p o su re. Exposure p a t t e r n s su g g e st t h a t th e c u r r e n t TLV o f 5 rag/M23 fo r a s b e s to s may be too h ig h . 1. INTRODUCTION. Numerous a u th o rs d e s c r ib e many case o f a s b e s to s is and th e in c re ased r i s k o f lung cancer fo r in s u la tio n w orkers w ith reg u la r exposure to asbestos or asbestos-containing m aterials (1 ,2 ,3 ,4 ,5 ,1 2 ,1 3 ,1 4 ). F le i s c h e r (1) found few c a s e s in 1946' o f a s b e s to s is among in s u l a t i o n w orkers in E a s te rn Navy S hipyards and m inim ized th e p o te n tia l hazard because d u st le v e ls were below th e th resh o ld lim it v alu e. A sbestos exposures to in s u la tio n w orkers d u rin g ship overhaul a t Long Beach Naval S h ip y ard were e v a lu a te d in 1965 by Marr (4) showing a s b e s to s is rem ains a serio u s occupational d isease a t Naval shipyards. N early a l l of M a rr's work was done w ith th e Bausch and Lomb Dust C o u n te r. B a lz e r (7 ,8 ) re p o rte d in 1968 th a t in s u la tio n workers in th e San F ran cisco Bay a r e a were exposed to o v e r a l l en v iro n m e n ta l d u s t c o u n ts n e a r th e th re sh o ld lim it v a lu e ; however, d e f in ite ra d io lo g ic lung changes were o b se rv e d in th e a s b e s to s u n io n p o p u la tio n . A pproxim ately 257. o f th e men w ith o v er 20 y e a r s work e x p e rie n c e and a 457. tim e w eig h ted exposure d isp la y e d ra d io lo g ic lung changes. His stu d ie s however, d id not include Naval shipyards. . Cooper (6) and B alzer (7 ,8 ) p o in t ou t th a t th e midget Im pinger sampling used in determ ining d u st co n cen tratio n s in clu d es a l l d u s t, and the a s b e s to s d u s t t h a t i s co u n ted i s m ain ly g r a in s alth o u g h some f i b e r s a re In c lu d e d . Lynch and Ayers (9) have suggested th a t th e 5 mppcf th re s h o ld lim it v a lu e i s no longer a good measure of a sb e sto s exposure, because s h o rt a sb e sto s f ib e r s a re la rg e ly below the re s o lv in g power of lig h t fie ld m icroscopy. C ralley e t a l (14) has suggested th a t asbestos fib ers act as c a rrie rs for carcinogenic m etals or other substances. 2 . STUDY BASIS. At P uget Sound N aval S h ip y ard , a 2 -1 /2 y e a r stu d y was begun in 1965 to com pare th e c h e s t X -ray f in d in g s and th e environm ent of 104 in s u la tio n w orkers w ith 6571 p ro d u ctio n and 420 c l e r i c a l w orkers. A sb e sto s ex p o su res have been p e r i o d i c a l l y e v a lu a te d by m idget impinger sam p lin g and counted by l i g h t f i e l d m icroscopy sin c e 1956 (1 0 ,1 1 ). The same methods were used in th is stu d y to compare d a ta c o lle c te d over th e p a s t 12 y e a r s . 1 3* COMPARATIVE REVIEW OF CHEST X-RAYS. Moat X -ray e v a lu a tio n s were based on se v e ra l reviews over the 2-1/2 year study p e rio d . Those w orkers who were exposed to lung h azardous c o n d itio n s re c e iv e d sem i-annual 14 x 17 in c h c h e s t X -ray s, a l l o th e r s rece iv ed an n u al 70 nan c h e st X -rays. Physicians lis te d the X-ray findings as " fib ro tic changes," or "pulmonary a b n o rm a litie s." T able I shows the d is tr ib u tio n of diagnosed pulmonary f i b r o s i s , or o th e r abnorm ality for each trad e category. Because the in su la to rs had th e h ig h e s t in c id e n c e (21.27.) compared to a l l o th e r tr a d e s , th e work h is to r y was in v e s tig a te d . Table I I compares th e age, employment, and f i r s t pulm onary a b n o rm a litie s fo r 22 i n s u la tio n w o rk e rs. Table I I I summarizes the only case diagnosed as a s b e s to s is rep o rted during the study. T ab le IV shows th e d i s t r i b u t i o n o f pulmonary f in d in g s compared to the years exposed. No e a s e s o f lung can c er were r e p o r te d in th e stu d y g ro u p . . 4 . ENVIRONMENTAL REVIEW. A irb o rn e sam ples were c o l le c t e d and counted a c c o rd in g to Che method adopted by th e N a tio n a l C onference o f G overnm ental I n d u s t r i a l H y g ie n ists i n 1942 ( 1 0 ,1 1 ) . P a r t i c l e s i z e d i s t r i b u t i o n s were c a l c u la te d f o r 20Z o f th e sam p les. The g eo m etric mean d iam eter d id n o t ex ceed 2 .3 m icrons by th e l i g h t f i e l d method f o r any sam ple. Many a sb e sto s fib e rs were probably below th e lim it of re s o lu tio n of the m icroscope (1 m icron) (9 ). The number o f fib e rs observed were re la te d to the type of m aterial. The m a te r ia ls d escrib ed in Table V a re used by n e a rly a l l in s u la to rs a t Puget Sound Naval Shipyard. The asb esto s p ro ducts are s im ila r to chose u sed by u n io n employees in th e San F ra n c isc o Bay a r e a (7 ,8 ) and Long Beach Naval Shipyard (4 ). Thoroughly w e ttin g am ositc o r o th e r asb e sto s m a te ria ls was found to reduce a irb o rn e p a r tic u la te le v e ls by o n e-h alf to tw o -th ird s compared to d ry handling techniques. W etting am osite or magnesia block before rlp o u t o f o ld in s u la tio n aboard sh ip is not p r a c tic a l because che adhesive and p a in t coating is w ater r e s is ta n t. I n s ta lla tio n or rip o u t of asb esto s in su la tio n aboard ship produces high concentrations of airborne asbeseos d u s t. Adequate v e n tila tio n and wet h an d lin g te ch n iq u es in the f a b r i c a t i o n shop keep th e d u s t le v e ls w e ll below th e TLV. T able VI shows che estim ated time w eighted exposure to asb e sto s d e te rm in e d from work sch ed u le s and f i e l d sam p lin g . The ex p o su re p a tte r n s f o r each i n s u l a t i o n job on new s h ip c o n s tr u c tio n , o v e rh a u l, and p r fa b ric a tio n are estim ated in Tables V II, V III, and IX. Graph A shows a ty p ic a l sawing o p e ra tio n where ex cessiv e exposures occur for b rie f periods. 2 Although d u st re s p ira to rs have been required fo r in s ta lla tio n or rip o u t o f a s b e s to s aboard s h ip s in c e 1956, t h i s su rv e y found th a t 76% o f th e in s u la tio n w orkers d id n o t use d u s t r e s p i r a t o r s . Over 50% d id n o t possess r e s p ir a to r s which are re a d ily a v a ila b le a t to o l rooms. 5. DISCUSSION. The exposure p a tte r n s of i n s u l a t o r s a t Puget Sound Naval S h ip y ard are i n t e r m i t t e n t , la r g e ly c h ro n ic low le v e l , b u t include b r ie f acute high le v e l episodes during sawing or overhaul of sh ip s when o ld in s u la tio n is rip p ed out w ith o u t p re -w e ttin g the m a te ria l. In d iv id u a l exposure p a tte rn s vary w idely w ith in work groups because of high m o b ility , in d iv id u a l work p a tte rn s , v a rie ty of job assignm ents, and th e u se o f many d i f f e r e n t m a te r ia ls . The in s u la to r s have a co m p arativ ely lig h t exposure when compared to a s b e s to s m in ers o r f a b r ic m a n u fa c tu re rs , y e t a f t e r about 10 y e a rs of exposure ch est X-rays begin to reveal increased d iffu se markings. Change of jo b s ta t u s , te rm in a tio n , or removal from th e hazardous duty l i s t may o b scu re th e p a s t o c c u p a tio n a l h i s t o r y o f in s u la tio n w o rk ers. There is a need to develop a uniform c la s s if ic a tio n fo r reading and id e n tify in g such X -rays taken o f in s u la tio n w orkers (14) and to m ain tain t h e i r o c c u p a tio n a l h is to r y . T h e -in d iv id u a l h a b its o f workmen app ear to p la y a la r g e p are in t h e i r exposure p a te e r n s . Some workmen wear t h e i r r e s p i r a t o r s , w h ile o th e rs w i l l n o t. Mosfc i n s u l a t i o n w orkers were aware th a t exposure to a s b e s to s , even ae low c o n c e n tra tio n s , is h a z a rd o u s. The a t t i t u d e p r e v a i ls th a t Che h a z a rd s a r e u n av o id ab le and must be accepted as p a rt of the trad e . T o ta l d u s t co u n ts a re b e lie v e d to be im p o rta n t because some o f th e g rain s a re a c tu a lly p a r tic le s from the asb esto s fib e rs or the p arent rock in th e asb esto s v e in . They are in fa c t c ry s ta llo g ra p h ie a lly in d is tin g u is h a b le from fib ro u s asb esto s (9 ). B inders, m etals from p ro c e s s in g (14) and s u r f a c e a b s o rp tio n may p la y y e t a n o th e r r o l e . U n til these u n c e rta in itie s are resolved, the fin e s asso ciated with asbestos products should not be tre a te d as in e rt m a te ria l. The 21.2% diagnosed lung a b n o rm a litie s found in in s u la tio n workers compared w ith 22% ( 7 ,8 ) found in union in s u l a t i o n w orkers in th e San F ra n c isc o Bay a re a . The 3.5% occurrence o f pulmonary a b n o rm a litie s among b o ile rm a k e rs w ith m a rg in al exposures to a s b e s to s and s i l i c a may be p a r t i a l l y due to a s b e s to s .6 6 . CONCLUSIONS. A 2 -1 /2 y e a r com parison o f c h e s t X -rays o f 6571 p ro d u ctio n w orkers and 420 c l e r i c a l w orkers a t Fuget Sound Naval Shipyard shoved t h a t 104 in s u la to r s h an d lin g a sb e sto s have 21.2% diagnosed pulmonary a b n o rm a litie s compared to the nex t h ig h e s t in c id e n c e of 3.5% f o r b o ile rm a k e rs w ith some a s b e s to s and s i l i c a ex p o su re , and le s s th a n 1% fo r c l e r i c a l w o rk ers w ith no known a s b e s to s e x p o su re . 3 Only one c a s e o f a s b e s to s is was diagnosed s in c e J u ly 1965 when the stu d y was begun. Exposure p a tte rn s and the high incidence o f lung ab n o rm a litie s suggest t h a t th e c u r r e n t th re s h o ld lim it v alu e o f 5 mg/MT f o r a s b e s to s may be too h ig h . Lung a b n o r m a litie s o f in s u la to r s a re f i r s t e v id e n t a f t e r about 10'year3 exposure and progress u n ti l retirem ent or term in atio n . I n s u l a t i o n w orkers h an d le a s b e s to s m a te r ia ls between 70 - 907. o f the work s h i f t . The exposure to asb esto s d u st is in te r m itte n t, although b r i e f e p is o d e s a t c o n c e n tra tio n s c o n s id e ra b ly above th e TLV do occur d u rin g saw ing o r r ip o u t. The t o t a l a irb o rn e p a r ti c le count ranges ab o u t 5 mppcf f o r ab o u t 50% o f Che work day. The a s b e s to s co n te n t of th e m a te r ia ls ran g es from 15 to 95%. The work day has p e rio d s o f i n a c t i v i t y , tim e between job changes, and tim e fo r m a te ria l a c q u is itio n s , which reduce the a c tu a l exposure to about 6 hours. A hig h in c id e n c e o f lung ab n o rm a litie s would not be expected according to tim e w eig h ted ex p o su res compared to th e p re s e n t TLV. T h is i s c o n tra ry to th e 21.2% pulmonary a b n o rm a litie s among in s u la to r s shown in T able I . P ossible explanations are: a . The pulmonary ab n o rm alities are the r e s u lt o f in te rm itte n t peak e x p o s u re s th ro u g h o u t each work day fo r more th a n 10 y e a r s . The tim e w eighted exposure e s tim a te s a re low and do n o t r e f l e c t th e tru e exposure. b . The th resh o ld lim it value has been s e t too h ig h . c . Methods o f e v a lu a tio n do n o t p ro p erly access th e exposure p a tte rn . The 21.2% pulm onary a b n o rm a litie s found among in s u la tio n w orkers a t Pugat Sound N av al S h ip y ard com pare to 25% found in union i n s u l a t i o n w orkers in th e San F r a n c is c o Bay a r e a ( 8 ) . * I f w o rk in g c o n d itio n s rem ain th e same! ab o u t 20% of th e in s u la tio n w orkers a t P u g et Sound Navel S h ip y ard can be ex p ected to have some pulmonary a b n o r m a litie s d is ti n g u is h a b le by c h e s t X -rays a f t e r 15 y e a rs in th e tra d e (Table IV ). 4 REFERENCES (1) F le i s c h e r , W .E.; V ile s, F . J . ; G lade, R .L .; and D rin k er, P ,: A H ealth Survey o f Pipe Covering O perations in C onstructing Naval V essels, J o u r n a l o f I n d u s t r i a l H ygiene & Toxicology 28:9 (Jan u ary ) 1946 (2) S e l i k o f f , I . J . ; Churg, J . , and Hammond, E .C .: A sb esto s Exposure and N eo p lasia, Jo u rn a l of American M edical A sso ciatio n 188:22 (A pril) 1964 (3) Keane, W .T., and Zavon, M.R.: O ccupational Hazards o f Pipe I n s u l a t o r s , A rch iv es o f E nvironm ental H e a lth 13:171 (August) 1966 (4) M arr, W.T.: A sbestos Exposure During Naval V essel O verhaul, . Am erican I n d u s t r i a l Hygiene A s s o c ia tio n J o u rn a l 2 5 :264, 1964 (5) S e l i k o f f , I . J . ; Churg, J . , and Hammond, E .C .: The O ccurrence o f A s b e s to s ls Among I n s u la tio n Workers in th e U n ited S ta te s New York Academy S c i. 132:139 (December) 1965 (6) Cooper, W.C.: A sbestos as a Hazard to H ealth , A rchives of Environm ental H e a lth 15:285 (Septem ber) 1967 (7 ) B a lz e r , J . L . : The Work Environm ent o f I n s u la tin g W orkers, American I n d u s t r i a l H ygiene A s s o c ia tio n J o u r n a l, V ol. 29, No. 3 (Kay, June) 1968 (8) B a lz e r, J .L .: The In d u s tria l Hygiene fo r In su la tio n Workers, Jo u rn al o f O c c u p a tio n a l M edicine, V o l. 10, No. 1 (Jan u ary ) 1968 (9) Lynch, J . , and Ayer, H .; Measurement of A sbestos Exposure, Jo u rnal o f O c c u p a tio n a l M edicine, V o l. 10, No. 1 (Jan u ary ) 1968 (10) U .S . P u b lic H e a lth S erv ice P u b lic a tio n , #614, The I n d u s tr ia l Environment I t ' s E v a lu a tio n and C o n tro l - C ounting and S iz in g A irb o rn e D u st, 1966 (11) S tandard Procedure fo r Sampling and Counting D usts, adopted by the 5th a n n u a l m eetin g o f the N a tio n a l C onference o f AGCIH, American I n d u s t r i a l H ygiene A s s o c ia tio n J o u rn a l (Nov-Dec) 1967 (12) K l e i n f i e l d , M ., e t a l ''M o r ta lity E x p erien ce i n a Group o f A sbestos W orkers, A rc h iv e s o f E nvironm ental H e a lth ," 15:177-180, (August) 1967 (13) Tabershaw, I . R . , Asbestos as an Environm ental Hazard, Journal of O c c u p a tio n a l M ed icin e, V ol. 10, No. 1 (Jan u ary ) 196814 (14) C ra lle y , L . J . e t al Research on H ealth E ffects of A sbestosis, Journal o f O c c u p a tio n a l M edicine, V ol. 10, No. I (Jan u ary ) 1968 5 IN C ID E N C E OF DIAGNOSED PULMONARY F IB R O S IS TRADE TOTAL WORKING FORCE S hipfittera Sheatmet a l Workers Forge Workers W elders Inside M achinists O utside M achinists Boilerm akera E lectricians Pipe C overers & In su la to rs P ip efitters Shipw rights & Joiners E le c tro n ic s Workers P ainters R ig g ers Temporary S erv ices C ontrol Group (c le ric a l workers) 890 489 32 998 536 490 115 574 104 765 228 280 263 664 143 420 WORKERS WITH PULMONARY FIBROSIS OTHER ABNORMAL X-RAY FINDINGS NUMBER PERCENT 6 .77. 6 1.27. - - 11 1.17. 1 .27. - - 4 3.51 as 22 21.2% 6 .81 - - - s 4 1.57. 1 .17. 1 .71 1 .2% August 1963 TABLE I IN TER V A L BETWEEN EMPLOYMENT AND FIRST X-RAY INDICATIONS OF LUNG ABNORMALITY EMPLOYEE 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 AGE WHEN HIRED 22 22 18 27 26 39 31 30 25 28 41 36 45 35 U9 38 54 31 57 47 22 YEAR HIRED 1933 1933 1936 1939 1941 1941 1942 1944 1945 1947 1947 1951 1952 1952 1953 1960 1958 1961 1961 1961 1963 1965 CHEST CONDITION 1 st NOTED 1959 1954 1958 1963 1947 1953 1961 1951 1963 1965 1964 1963 1962 1958 1962 1960 1960 1966 1961 1962 1965 1966 INTERVAL BETWEEN EMPLOYMENT AND 1 s t X-RAY ABNORMALITIES 26 y e a rs 21 22 24 6 12 * 19 7 18 18 17 12 10 6 9 m 2 5 - 1 2 1 A ug u st 1968 TABLE I I .. YEARS IN PC&I TRADE AT PSNS (WHERE KNOWN) 33 33 30 27 25 23 17 22 21 20 20 15 m - 13 6 8 5 5 5 3 ' 1 EMPLOYEE NUMBER 7 : CASE H ISTORY DATE 1942-52 1952-60 I960 1961 1967 1967 OCCUPATIONAL HISTORY PC&I a t PSNS PC&I m aintenance work, apartm ent houses PC&I a t PSNS PC&I a t PSNS PROBABLE ASBESTOS EXPOSURE unknown interm ittent, less than 5 mppcf * le ss than 5 mppcf le ss than 5 mppcf d is a b ility retirem ent com pensation awarded f o r ' d is a b ility due to a s b e s to a is CLINICAL HISTORY X-ray: negaci\ X-ray: negativ Pulmonary abnor i t i e s 1 st noted X-ray Asbestos found lung during sur * 5 mppcf is th e c u r r e n t recommended th re s h o ld lim it v a lu e f o r asb esto s A u g u s t 1968 TABLE I I I YEARS AT PSNS 0-5 . 6-10 11-15 16-20 21-25 25+ NUMBER OF WORKERS 25 28 11 20 7 7 DISTRIBUTION OF LUNG ABNORMALITIES AMONG PIPE COVERERS AND INSULATORS INCIDENCE OF DIAGNOSED PULMONARY FIBROSIS OR OTHER ABNORMAL X-RAY FINDINGS MEDIAN ACE 37 47 43 48 51 56 NUMBER WITH PULMONARY CHANGES 2 5 1 4 4 6 PERCENT OF INCIDENCE BY GROUP 8Z 18Z 9Z 20Z 57Z 90Z PERCENT OF INCIDENCE BY TOTAL PC&I WORK FORCE 2% 5Z 1Z 4Z 4Z 6Z AGGREGATE = 21.67. Aucusc 1968 TABLE IV IN SU L A TIO N M ATERIAL AND USE AHOSITS Use: P ip in g , f i t t i n g s , machinery u n it s and la r g e o r ir r e g u la r surfac C om p osition : Long f i b e r a sb e sto s 957. MAGNESIA BLOCK INSULATION Use: Tanks, b o i l e r s , v a lv es and p ip e s ., C om position: Magnesium Carbonate 857. Long f i b e r a sb eseo s 15% ASBESTOS CEMENT U se: F in is h in g and I n s u la tin g , u sed o v e r bare m e ta ls or in s u la t io n and as a f i l l e r Com position: Johns-M anvllla #301 Asbestos (C rysotile) 15% Portland Cement 171 Clay 33% M ineral wool 20% Diatomaceous esrth 15% One-Cote N odulated f i b e r and A sb esto s ( C r y s o t ile ) - l e s s than 500%3 P ortland Cement l e s s than 30% Diatomaceous earth l e s s than 20% Clay l e s s than 30% Calcium s u lf a t e or n itr a te l e s s than 5% O rgan ics trace August 1968 TABLE V IN S U L A T IO N MATERIAL AND USE ( C o a t ' d ) UNIBESTOS Use: P ip in g up to 30 in c h e s in d ia m e te r, v e r y l i t t l e i s used a t th is time Com position: F in ely ground asb estos fib e r Waterproof adhesive ASBESTOS CLOTH Use: F in a l coat or lagging on pip in g , v alv es, tanks, f it tin g s , and machinery in s ta lla tio n s C om p osition : There are th r e e w e ig h ts ran gin g from 1 .2 5 Co 2.U I b s /s q . j 801 to 95Z C r y s o tile or Am oslte a sb e sto s f ib e r w ith cotton fib er FIBERGLASS Use: Many ty p e s such a s b a t t s , s h e e t s , molded p ie c e s and f e l t are a v a ila b le for d iffe r e n t a p p lica tio n s such as ven t d u cts, p ip in g and v a lv es Com position; Fibrous g la ss w ith binder CORK Use: R e fr ig e r a tio n and a ir c o n d itio n in g p ip in g . ^ Com position: V egetable product ' . RUBBER Use: R e fr ig e r a tio n and a ir c o n d itio n in g p ip in g , r e p la c e s cork in most a p p lica tio n s C om p osition : Foam rubber A ugust 1968 TABLE V (C o n t'd ) a v e r a g e t i m e - w e i g h t e d e x p o s u r e t o i n s u l a t i o n MATERIALS * OPERATION AND MATERIAL In stallation Amos i t e I n s t a l l a t i o n Magnesia block in su la tio n c u t t in g and i n s t a l l i n g A sbestos Cloth c u ttin g , g lu ein g and f it t i n g A s b e s to s Cement nixin g F ib e r g la s s , Rubber, and Cork PERCENT OF TIME EXPOSED NEW SHIP CONSTRUCTION SHIP OVERHAUL 10% 117. 391 351 20% 137. 1% II * 30% 13% Rip-Out Am osits 4% M agnesia b lock in s u la tio n , . A m o site, and U n ib estos 171 F ib e r g la s s , Rubber, and Cork 57. P r fa b ric a tio n in Shoo M agnesia b lock in s u la tio n , A m osite and A sb e sto s Cloth F ib e r g la s s , Rubber, and Cork P ercent o f Time Exposed 50% 25% * Baaed on 6 hour work day. August 1968 TABLE VI M a te r ia l and O peration A m oaite; I n s ta lla tio n M agnesia b lo ck in su la tio n : c u ttin g and In s ta llin g A sbestos c lo th : cu ttin g, g lu e in g and f it t i n g . M ixing a sb e sto s cement F i b e r g l a s s , rubber and cork NEW SHIP CONSTRUCTION Airborne Dust Concentration In B r e a th in g Zona (M illio n P a r t ic le s per Cubic Foot) Ranee Averaae 2.6 to 8.9 3.6 2.4 to 13.3 6 .1 3.1 to 4 .6 11.3 to 82.8 amsees 3 .6 47.5 ' P e r ce n t o f Time Exposed (Average) Based on a 6 hour day 10% 39% 20% - 1% or l e s s 30% A ugust 1968 TABLE V II SHIP OVERHAUL M a te r ia l and O peration ' INSTALLATION A sbestos clo th ; cu ttin g, g lu e in g and f i t t i n g Airborne Dust concentration in B reath in g Zone (M illion P a r t ic le s per Cubic Foot) Range Aif e r a g e 2 .8 to 5.7 A .3 M agnesia block In su la tio n : c u t tin g and i n s t a l li n g 3 .5 to AO.5 16.7 Am osite 2.6 to 8.9 A .5 F ib e r g la ss, rubber and cork -- mmt m RIPOUT Amosite 1.0 to 7.7 A .A M agnesia block In su la tio n and a sb e sto s c lo th 2.6 to 6.8 5 .0 A s b e s to s c lo t h and u n ih e sto s Fiberglass 2 .8 to 17.4 6.7 P ercen t o f Time Exposed (Average) Based on a 6 hour day 15X 35X m 13% 41 nx nx M agnesia b lock in su la tio n A m osite Asbestos cloth F i b e r g l a s s , ru b b e r and cork PREFABRICATION IN SHOP Airborne Dust Concentration In B r e a th in g Zone (M illio n Range csm, Average 1.1 to 1.3 1.2 (cu ttin g) .32 (glueing) 2.4 (cutting) .39 to .41 .07 to .1 .1 to .15 .4 (sewing) .09 (glueing) .13 (pinning and narking) Percent of Tine Exposed (Average) Based on a 67% -- --. 33% A ugust 1968 TABLE IX U h O O li_ LO. CV1 O -- I en r> 3 O O O O (VI d: lu iu ____ i U) ~ LU lr io - -J JS _ cl h* i r ..J ?n. O r.. h O LO GRAPH A RELIEF SAWING AND HANDLING MAGNESIA BLOCK INSULATION CONTAINING 15% ASBESTOS FIBER a 85% MAGNESIUM CARBONATE , 2 3 rem o val of blo ck FROM COXES AND STACKING ND SAW R ELIEF \ D HANDLING \ .4 5 o' 0740 7 8  I SELECTED REFERENCES RELATED TO ASBESTOS EXPOSURES OF PIES COVERERS AND INSULATORS 1. F le is c h e r , e t e l , A H ealth Survey o f Pipe Covering Operation in Cone tru e t in g Naval V e s s e ls . J . Induet Hyg & Tox 2 8 . 9 January 1946 An e x c e lle n t re fe r en ce th a t shove hov l i t t l e th e exposure p a ttern s and tr a d e method* have changed. The a u th o rs concluded th a t th e nuaber o f diagnosed a s b e s to s is ea ses r e fle e t e d th e hazards, which h a s s in c e been found n o t t o be t r u e . Most PC&I personnel do n ot f ile claim s. 2 . M arr, W.T., A sb e sto s Exposure P u rin a N aval V a ssa l O verhaul. AIHA J 2 5 ! 264 May 1964 ` --- Marr's work b e tte r r e f le c t s th e exposure p a ttern s ewl the p o te n tia l hazards from a sb esto s exposures. 3 . S a l i k o f f , I . J . , e t e l , A s b e s to s Exposure and N e o p la s ia . JAMA A p r i l .6 1964 S e llk o ff'e a r t ic le suggested th a t a high rata o f cancer was re la ted to asb estosis. 4 . B a lx e r , J . L eroy, in d m e ^ fe l H ygiene fo r I n s u la tio n Workers. J Occup Med, V ol 10 # 1 , January 1968 T h is U n iv e r sity o f C a lifo r n ia researcher found in the union in su la to r s about eha s e n r a ta o f pulmonary a b n o r m a litie s aa found a t PSNS. 5 . S a l i k o f f , I . J . , a t a l . A s b e s to s Exposure Smoking and N e o p la sia . JAMA A p r il 18 7 o l 204 # 2 , 1968 S a l i k o f f lin k e d smoking t o h ig h r a t e s o f c a n cer among a s b e s to s w orkers. 6 . C.A . Mangold, R .B . B e c k e tt, D .J . Beesmer, A sb esto s Exposure and Pulmonary r - m v nhenoeg t o F in e C overers end I n s u la to r s a t Puget Sound N aval S hipyard. I n d u s t r ia l H ygien e D iv is io n , PSNS, August 1988 A s b e s to s worker s a t PSNS have an average o f 21Z pulmonary a b n o r m a litie s , compared t o a l l o th er work groups. The p ercen ta g e o f pulmonary a b n o r m a litie s grouped b y y e a r s in th e tre d e a r e : (1 ) 15 to 20 y r s - ---- 207. ( 2 ) 20 t o 23 y r e -- -- 57ZJ 23 y r s + ------ 901. r '5hCX. I a - r`-to.* <sjy z - \.r m- ' Asbestos as an Environmental Hazard JRVJN'G R TABKRSHAW MX) D r, rateM^&u? F r a / j o r p/ Occupational Medici School of Public Health, University of California, Berkeley. Presented at the Eleventh Annual Meeting of the W est en indtiocrwxl Wealth Conference, 5an F^ancwco, Septem ber 2$ and 30, 2S67. J n FEBKt'Aflv or n o s rEA* Cooper, m a paper I entitled, "Asbestos as a Hazard tc Health,"1 commented as follows: "We often try to emphasize that part of the challenge oi our field is that it ts at the forefront of medicine and technology where environmental hazards can first be detected m V>**'*' r.f f* rabiiys *%**> r**' V(>o%n'ra* ,.rrt <ni opportunities to study populations at risk. But when the relationships are actually suspected and gradually established, very real and practical con sequences become apparent. 5o the speculations, call them fancies if you will, that are part of the normal processes of developing new knowledge in other fields become menacing and are misused and misunderstood." You have heard today that in industries using asbestos as a basic material, that is mining, mill ing. fabrication and installation, that a relation ship has been established between asbestos exposure and fibrosis of the lung, lung cancer, and possibly with an increase in the incidence of mesothelioma and gastrointestinal malignancies. The incidence and seventy of the pulmonary fibrosis i.ashestosis) are apparently dependent on dose. This dose-response relationship ir. asbestos workers will probably be proven in time to be true also for the neoplasia of the lung, pleura and gastrointestinal tract Concern, however has been expressed that asbestos in ambient air may con* stituie a real threat to the entire public and not vast to those occupationally exposed, This grave implication is summarized in an article by Thomson,1 who raises the question of "whether a small amount of asbestos m the lung bases or in the adjacent pleura or peritoneum is an effective carcinogen or co-rarcinogen m hu mans. if it is present there for 30 years or more." This concern is reiterated by Selikoff and his co workers3 in a lengthy editorial with the state ment: "The neoplasms now encountered associated both witr. industry and environment are conse quent upon Shhaiation of asbestos associated with the limited asbestos production of some 30 years ago. The r.eoolasms associated with current utili zation and exposure to asbestos will not be evi denced until 1990." If this is true, it changes the order of magnitude of the hazard and places asbestos in the forefront of public health problems, it is to this allegation th a t I wish to address myself. A good deal of the information on which this potential threat is pos tulated is in the realm of "speculation" and it is not always possible to separate the "fact' from the "fancy." OR t 1 32 0 a PLAINTIFF EXHIBIT v SOA 5504 The data which lead to this speculation is most ly epidemiologic in character. Toere is unequiv ocal evidence that fibrosis of the lung (asbestos) occurs in asbestos workers. Pleuritis is a frequent sequela of asbestos exposure and a rare malig nancy of the pleura, mesothelioma, shows a re markable increase in asbestos workers and in individuals living near asbestos-producing mines and 'c'cr-s, h'ecpiasms of the iung occur more frequently m individuals who have asbestos or who are occupationally exposed to asbestos. These findings, per se. would not lead to the sweeping speculations made by Thomson. Selikoff and others were it not for the additional finding that a large percentage of individuals over the en tire world show "asbestos bodies" in their lungs at autopsy even though most hove had no known occupational exposure to asbestos (Table II. Since "asbestos bodies" are specific for past exposure to asbestos or similar fibers, the speculation that all of us are under some increased threat of lung cancer due to the presence cf ambient asbestos is valid. Assessment of the magnitude of this threat is the crucial question The dynamics of the situation will not permit us to wait until 1990 for a defini tive answer Forces such as the increased use of asbestos products and the general soiling of ambient air in our industrial technological society demand that we make some judgment now If we cannot make this determination, we must direct our research into those channels which will be most likely to give us early and definitive proof Epidemiological studies are of prime importance and in fact present the most convincing evidence that asbestos may be dangerous to the working population, but the likelihood of proving that there is an increased risk to the public from asbestos in ambient air. by using epidemiologic methods, is very small Even if all the factors which could influence its evaluation are known and a prospec tive study devised to demonstrate an effect by 1990, any conclusions from such a study would be subject to severe doubt because of the many TLE 1 f t f t o d U s t in Lung Sm**rs* ' *Crr'tO'' Cdw*- +f A Av jvI 9* a'. Cc & 'abe*ifie<~ `libit ,|9&55 USM' MS44I "Ui' C ad Pi+*il/rC^ Jchernffibcfg Sa* see Zo * ee r 2* - ` 1.0% 31.2% 57 6% 4 0*/a ` S o% a \>M*l*e**<j ooxy >ee*,ioiM 'or-*1 Coop*1* w OVt iMepoi j e ndjsfc **,8,**_&** Ac Arc* 6**11** `5 2i !$*s?fr're'-} Journal of Oocupatfonal Medicine 7abi"s5au* variables which Could not be controlled satisfac torily. For instance, it would be almost impossible to select a proper cohort which could be followed over the many years: the selection of matched controls would be almost insurmountable: the in creasing use of asbestos and th* differences in composition and possible exposure in various lo- rui^ies, end the ^T,cnr introduced by co* carcinogens in our environment further becloud the issues and make it very unlikely that an equivocal answer could ever be forthcoming in m this type of evidence alone. The experimental approach car. provide only tentative answers since it has been demonstrated that, while asbestos will produce irritation, plaques and malignancies in serous cavities, it is relatively inert as an over-all irritant to biologic materials Furthermore, the translation of effect from any species of animals to man is difficult at best and is made even more questionable by marked variations in respiratory tract response by different animal species. The anunal selected must most nearly resemble the human lung in order for the experiments to be meaningful. Dif ficulty ls evidenced, for instance in the fact that some animals, e g. the cat and the guinea pig. will produce fibrosis and relatively few asbestos bodies, and others such as the mouse will produce relatively few asbestos bodies but no fibrosis * This is probably related to the variations m the evolution of alveolar macrophages which Collet et aid have demonstrated to differ among humans, cats, rabbits, and guinea pigs Exposure factors are not completely under stood. Asbestos is said to be indestructible, hut the term is a relative one; high heat, chemicals and body fluids produce changes m its physical and chemical properties in time There is undoubtedly a difference m effect from a heavy, brief or con tinuous exposure as occurs in industry to a sus tained minor exposure which mat occur from ambient air pollution. Seltkoff0 has iterated many times that there is an increasing use of asbestos (Table II) and surmises that we are presently seeing lur.g malignancies "consequent upon in halation of asbestos associated with the limited asbestos of some 30 years ago " The implication is clear that if this relationship (tons of asbestos produced to incidence of lung malignancy) ts true, the multifold increase m its use has started an up ward trend which will be reflected for the next 30 years and more This extrapolation is unwarranted, Increased production cannot be equated with increased hazard, especially in a substance like 981105 H&rRdbJ 33 2652 Asbestos H aard--Environment V&A.R BBC QQC 1920 H30 {50 i960 iOM l " rA&LE H Wor Pt&iiitfion o* Aigtfte*" *AdiC'ec *e-` v* `oa VO TONS $00 3500C 200.000 *S0.0CC 1 200000 2 300 00C : : : : see 3 5*0000 isooooc asbestos which is used for the most part in products which are unlikely to become airborne. The largest amount--one can only guess at the percentage--goes into asbestos products which, once applied do not disintegrate, such as build ing materials and floor tile. A iair estimate might be that some 10 to 15% of the asbestos in the ap proximately 3.000 end-products containing this mineral, e.g. brake lining and asbestos textiles, may by deterioration, weathering, heating, etc., become airborne. However, there are no studies of asbestos concentrations in ambient air. Indi cations that asbestos may be earned considerable distances in the airstream1 are based upon: (1) Analysis of deposits on the surface of the earth, snow, etc., (2) evidence that significant numbers o: people with mesothelioma worked or lived near asbestos m.nes or plants; and (3> evidence that a significant population has asbestos bodies m their lungs at autopsy. But as yet the type, amount and panicle sue of ambient airborne asbestos has not lent itself to systematic detection and identifica tion. It should also be borne in mind that asbestos deposits have mineral outcrops and hence there vs a strong possibility that asbestos in ambient air may be a natural phenomenon and not only a result of increased industrial activity. Clinical experience indicates that the appear ance o: asbestosis (pulmonary fibrosis) is dosedependent. Children have died of asbestosis and cor pulmonale after a few years of an overwhelm ing exposure "within large shipping bags, tram pling down fluffy amosite asbestos which all day long came cascading down over their heads."8 Sluis-Cremer1' gives an average in one factory in South Africa of 6 years a: work before asbestosis was manifest. Jacob and Auspaeh,10 m Dresden, determined an over-all average of 30 years before the asbestosis became disabling. X-ray changes are induced in most cases after 20 years' employment as an insulator (Selikoff, p. 147). One of our cases showed evidence of the fibrotic process on lung biopsy some 22 years after a heavy exposure of less than 2 years' duration. t taius tn Wort*"*ihpotti? ta Aibftvtw\* ft*UmHd St'tta (1963 C*nim 1 SAW PROO'jCI UAML'l-'vClUilNG Ai>w Predytts H93} A*tr$5+0* Potr f{93! As**`*i Mries 1 Mm* of Cftmnwci] no. woaxess n$li 11,17* m i h*,A**` -Sc Cj- 'Ao-aw's ' 19^* V"Z'Z f 3 000 Aoo/errf'jM To**' US tootp $0 600- While long latency is usual and progression, of the fibrotic process may continue long after the exposure has ceased, there is little information forthcoming regarding quantitative data or. the dose which each individual was exposed to Lung clearance studies indicate a marked difference in the effects of short, heavy dust exposures as com pared to minor, low exposures. Heavy dust in halation incites an acute flammatory reaction and stasis m the respiratory bronchiole and adjoining alveolar ducts and may provide a nidus for a con tinuing effect. That asbestosis, i.e. the pneumoconiosis, does not present a major problem for the future is most ly due to the fact that the occupational population at risk, which is difficult to determine exactly, ,s still quite small and can never reach large num bers (Table 111) While members of the construction industry', for example plasterers and some automobile work ers, e.g. brake repairmen, may have greater ex posures than insulators working directly with as bestos products, it is safe to say that the kinds of exposure experienced in industry will never affect any sizable group m the general or working population. The threat from asbestos, however, lies in its possible association with lung cancer; and the ex pectation that there will be no increase in the mortality from this disease among exposed work ers is not so sanguine Cancer of the lung occurs more frequently in those with occupational ex posure. whether or not they develop fibrosis, and this evidence is amply substantiated (Table TV) Two aspects axe not known, the pathogenic factors and the dose of asbestos which produce this in creased susceptibility. We do.not know whether asbestos has properties of primary carcinogenicity or whether its effect is entirely synergistic. That other factors must potentiate the asbestos ex posure has been postulated by Selikoff and Ham mond11 who show that asbestos insulators who smoke have about 90 times the incidence of lung 34 981105 MarRsbT 11968 Volume 10 No. 1 2653 Tabersaair E piriH ttigqic S ijf l', 1 TABLE IV la p o iu r , and ly n g C , n*-* RAC; U ^ife d K i*aeJo*t C a V o '"'* w 'e va V S,A autho r D oli YEARS N O W 'T -. F O L L O W LUNS cancer 31 iiy je it ry * ivta-c-ivs & . *j*J r Sfc *." *r Ot/AH it W fl Jdcub & A jv o a i:* 1** e 20 -?v 7,1 2* 2 < /2 8 6 s /s t D M 4* * !? * * $ .'2 3 $ 1 0 /*' o ta *-! 3a/C `2 COM. P A R 'S D N C b /c io .c t.E -0 .8 e io rc ts d li6 iC > C -- 5 4>l --&.C -2 -fi t*Dcr*<* - i} S -- II o * A a o o ` * <3rr W C ' 1t C o o c o '---A $ se s*? s I a n a to r e t c `"'* 4 1CaC* a * c $ o * 3 u ie * , 3~ A r c 'Spp'pfnbpr) 'bit. : i v i c i H a!*h 15285 malign.ar.cy of smokers who are not exposed to asbestos, The metal complexes :n the asbestos fibers (nickel, chromium, etc.), benzpyrene and others carcinogenic agents absorbed on tbe asbes tos, allergic response which produces altered im munity. and the increased burden from urban populations or smoking are now postulated to be the major co-factors which make asbestos careinoger.ic.1: A dose too small to produce fibrosis, t*. asbes tosis, may, nevertheless lead to lung cancer. A dose large enough to produce asbestosis may cause malignancy if the worker does not die first from his pneumoconiosis. However, many men, after a lifetime of -work with asbestos products--specifi cally insulators--show no evidence of any unto ward pulmonary pathology. Again, in all of these, the amount of asbestos inhaled is unknown. When the dose is known to be related to the incidence and severity of a disease (send it grossly appears to be the case m asbestosis), it is safer to postulate that a non-threshold relationship exists. From a practical standpoint, however, asbestos would be ar. unusual disease agent if it did not have such a threshold. "Proof," however, will always be a speculation, as it is for example m determining the carcinogenic level of radiation There is no way of estimating this threshold level, which at present needs more industrial hygiene studies. Our findings support those of other investigators who state that pleuritis occurs in about 25% of insulation asbestos workers. The incidence of mesothelioma in this group is extremely large, considering the rarity of the tumor Selikoff re porting on a senes of 124 deaths from neoplasia m insulators found 10 with mesothelioma,' This malignancy has also occurred in increased incidence m some populations which did not work directly with asbestos. In a very large proportion in South Africa and in a considerable number of the the victims of this malignancy in the United States, environmental exposure is postulated as the cause since they lived close to asbestos plants using especially amesite or crocidolite." The evi dence is strong that the source of the gent was v'd-e-i c rrerr. me asbestos factories or mines, even though many of these individuals did not show an underlying asbestotic fibrosis- How ever, the ambient concentration or indeed the spe cific type of asbestos to which the person was exposed and which could be responsible for the disease has never been determined, either in the neighborhood or in the working environment. An increased incidence of gastrointestinal ma lignancy is still being investigated, but the statis tical inference is strong that there is an increased susceptibility m those exposed to asbestos This will probably be clarified in time Emphysema or chronic bronchitis, if it does occur as a result of inhalation of asbestos dust, would always be ob scured by the underlying pneumoconiosis; and the diagnosis of these conditions' would always be considered a secondary rather than a primary disease. A link and perhaps the key to the problems lie in understanding the role of the "asbestos body" in the pathogenesis of the different tissue re sponses. Our experience supports the statement of Gough:" "Asbestos is diagnosed histologically by th e association of asbestos bodies and asbestos fibers with fibrosis '' However, what the "asbestos body" means in individuals who apparently have never been exposed to asbestos is not clear. If this can "be explained, inferences then could he made with some certainty regarding the potential en vironmental hazard, The presence of "asbestos bodies" in the lung is a biological indicator of exposure to asbestos Whether or not other mineral fibers can produce an "asbestos body" is not pertinent in an environ mental sense The highest concentration of min eral fiber m ambient air is overwhelmingly asbestos and hence one can assume that "asbestos bodies are almost entirely derived from asbestos fibers." "Asbestos bodies" probably can be found m every lung at autopsy if searched for long and hard enough and an occasional one is adventitious and simply indicates that mineral fibers make up a p a rt of the dust in our environment. The fibrosis of asbestosis is nonspecific and has no special structural characteristics except for the presence of "asbestos bodies." Hence, interstitial Journal of Occupational Medicine 981105 NarRdsJ 35 2654 Asbestos Hazard-- Environm ent fibrosis without the presence o "asbestos bodies" cannot be called asbestosis. Conversely, however, "asbestos bodies" in sputum or lung tissue with out fibrosis is not asbestosis but simply an evi dence of exposure. Phagocytosis by macrophages is e major cleansing mechanism of the lung; they tfir~>-t-tsl ^Ke typical "asbestos boav." No relationship has beer, established between the number, type, or size of "asbestos bodies' and the tune of exposure, fiber size, concentration, or form of asbestos Individuals who show "asbestos bodies" on lung smears at autopsy do not seem to have an inincreased incidence of any- specific pulmonary dis ease. "Asbestos bodies" may be found in lung smears and not a the correlating tissue. Cauna et al,15 found that only 49c of lungs showed "as bestos bodies" on histological section, whereas smears cf the same lungs showed "asbestos bodies'' n 415b Our findings are similar--lung smears ir. consecutive autopsies without known exposure to asbestos revealed an incidence of "as bestos bodies" in i5% while search of the matched lung tissue yielded only 35c. This may be a func tion of the amount of material available for study since the lung smear represents a much greater anatomic area than the lung tissue studied in histological section. Meurman found a consider ably higher correlation of lung smears to lung sections but he used special techniques to demon strate "asbestos bodies." Our own interpretation is that while the differ ences in amount of materia) which is available for study may account for some of the disparity, there is evidence that mineral fibers are cleansed through the macrophage system and hence found m the alveoli and bronchial lumna but do not enter into the interstitial tissue. Only over whelming exposure or perhaps some other factors which permit fibers to penetrate with formation of interstitial "asbestos bodies" lead to lung ma lignancy, pleuritis and mesothelioma. "Asbestos bodies" are not seen frequently in routine his tologic study of lung pathology. This is not an oversight by the pathologist since section; of lung especially stained and studied for "asbestos bodies" do not reveal an increased incidence (only about 3%). Our present view is that asbestos fibers are phagocytized in the airways and excreted m the sputum. In some instances the fibers penetrate the bronchial tree, giving rise to fibrosis, or into the pleura producing pleuritis. Co-factors, which are not completely understood at present, operating with the asbestos cause an increase in lung cancer susceptibility and in the appearance of mesothe lioma. As the role ofthe "asbestos body" becomes clearer and more data becomes available on the distribution, type, fiber size, and concentration of airborne asbestos and the role of co-factors, the able tc assess tiic potential en vironmental hazard from this ubiquitous mineral In summary, if one accepts the assumptions (I) that asbestos minerals increase the risk of lung cancer in occupational groups, (2) that they lead to an unusual risk of mesothelioma of the pleura and peritoneum in occupational groups and those living near asbestos plants, (3) that such malig nancies usually result from exposures 30 to 50 years earlier. (4) that the "asbestos bodies" found in from 25 to 509c of lung smears from routine autopsies are probably due to asbestos m most cases, (5) that these "asbestos bodies'" may result from recent exposures as well as those many years earlier. (6) that world production and use of asbestos has increased from 500.000 tons to 3.500. 000 tons in 30 years, it is important to consider whether or not asbestos is a major threat to pub lic health. One is not yet justified in such a con clusion, in view of the fact that much of the world tonnage goes into uses that do not lead to air comaminaiion; asbestos is not actually inde structible, that the effects are dose-dependent, and that low doses probably lead to lower rates and longer latency. Nevertheless, theie is need for epidemiologic studies directed to groups with intermediate ex posures and for evaluation of the beneficial effects of cessation of smoking, Another need is for ex perimental and industrial hygiene studies to de termine the nature and degree of exposure. Biologic studies centered on the meaning of the "asbestos oody" are crucial to understanding the chmcopathoiogic response. Strict control of in dustrial and neighborhood environments is essen tial, but it is premature to extrapolate from the effects of heavy exposures to minor and low level exposures. 3206 G n tzly P e ck Berkeley, Calxj. 94705 References; 1 Cooper, V7. Clark: Asbestos as a Hazard to Health-- Fact and Speculation, ArcH Enctren HtaiiK 15:285 (September) 1967. 2 T homson, J G.' Asbestos and the Urban Dweller, Ann jV .Y . A cad S ci 132.196 { D ecem ber) 1965 981105 H R J 2655 36 January 3968 Volume 30 No. 3 ar ob 3, SLrxon\ 1. J and KAMbyD. . C.: Afioesteis and NcpUsia. Aw J Med 42:487-06 (April) 1967. 4 Career, LfRoy LV ChrysoUie Asbestos an 2nd* cator of Subtle Differences in Animal Tissues, Am Rv Tuber? 45:762-756 (June) 1942. 5. Cou*CT, A., MaRItk, J. C.t NoiWASO-RiMrr. C and Poi.!c>*B%A RiuKerches *ur lXvolution des Macro phages AlveoUires---Injnaled Particles and Vannj,e t * ll tc::cd b.* Z N Davies Rergamn* press. T/iincurg;K Lorg Island Cit\ 1057 G. Sn.:xoFr, X. J The Occurrence of Pleural Caie.fiet;on Among Asbestos Insulation Workers, Ann,KY Acad Sc%. i32.35i-3G7 (Decerneex) 1965 r Mevrman, Lai/ri*Asbestos Bodies and Pleural Plaques *n Finnish Senes of Autoosy Cases, Acta Pclh ti _ Microbwi Sccnd (Suppl 181) Finland, 1965 -* $, Schemas, G, W. Discussion, Ann NT, Acad Sci 132 246 (Decemoer) 1965. 9 SMM5-CltMP. C K.` Ashesw*i5 m South Africa--* Certain Geographical and Environmental Consider' tions. Ann AT. Acad Sex 132:2X5, iDeoember) 1965 19 lACOi, G. and A^spack, M` Pulmonary Neoplasm Among Dresden Asbestos Workers, A*u iCY Acad 5n 132.336 (December' 1965 11 Stuxorr 1 *. and Hammond, C Newspaper Clip- snnr. PG3 A ?a , f*** 12 o u l it y , f_. 7 : ICecv^^, 7\ 0 and 7.y*ch. 2 ft.- Ex posure to Metals it the Mar-'factu-e of Assesses Tex* tile Products, Am h td Hyp Awn * 2 3 452-461 (S cpl- Oet: 1967. 13 Lints. Jax: Maligruncies tn Asbestos Workers, Arch Sureron Hlih 13*6X9-621 (November) 1966. li. Golck, J. Differential Diagnosis in the Pathology of Asoestosis, Ann A`V Aecd Sc; 122.35S (Deoernoer) 1965 15 Caw a, Dzdra, Torres, R. S. and Gross, f : Asbestos Bowes in Human Lungs at Autopsy. JAMA 192:371-373 (May 3) 1965. The Urban Environment Natural resources have always been defined as those parts of the natural environment that have value to mankind because the demand tor them ex ceeds the limited supply. It is in this sense that "new" resources, other than `he tra d itio n a l ones of agricultural land, w a te r, ana minerals, hav e increased m value. In this light urban land is particularly valuable. J ust as we had to learn to use sgncu.tural land with special regard for its qualities and the demands made on n, so we will have to change o u r vigw or urban land. Today its use is Haphazard and largely unthinking We have not yet learned to ask ourselves, for example, whether we want to use a third, a half, or two thirds of our urban land for the movement and storage of cars. How much are streets worth to us--underground, on the surface, above ground' Equally important, or possibly even more important, we now have to con ceive ot yet another critical resource: th e thirc dimension o: toe cu t--tne space over the urban land This is used even more haphazardly than, the land itself, Just on the horizon is a host of problems caused by elements competing for this limited resource--htgh-nse buildings, mterbuildir.g walkways, highlevel and air-cushion highways, and private rooftops. This space over the city is an asset that must be conserved, developed, and used with the greatest rare. Two-dimensional la n d -u se p lan n in g is u u t-u f-d ate, a n d w e u ig e n tiy n e e d to learn how to prepare three-dimensional plans, --F^on; "Modernizing t>ban Deeflcproertt" by Hirvti S PeWoJ? in Daedch*$--Summer, 1967. Joumitl of Occupational Medicine 981105 MarRobJ 37 2656