Document OE9aYXYoXjxx0Zb94YvkDKvbQ

K atharine H. Boucot, ?'.D. Chief E d ito r, Archive of Environmental H ealth ` arian *a Hectical College o f Pennsylvania 3300 Henry Avenue P h ilad e lp h ia , Pennsylvania 19129 September 21, 19&5. * Dear Doctor Poucet, 1 aa reluctant, as a r a tte r of principle, to deprecate the e ffo rts of a p h y sical s c i e n t is t to c a s t new l ig h t on b io lo g ic a l phenomena so as to c o n trib u te to the c la rific a tio n of enviromenfcal facto rs th a t influence, or appear to be capable o f in flu e n cin g , human h e a lth and. w e ll being At t h is t i r , e s p e c ia lly , the contributions of in v estig ato rs ir. a broad range of scientific d isc ip lin es are sorely needed in a id o f a mere comprehensive understanding o f the c u rre n t, complex, human environment,, as i t i s a ffe c te d by modem technology However, th e a r t i c l e by C la ir C. P atterso n , Ph.D. in the September issu e o f th e Archives of E nvironm ental Health {11:344-60, 1965), e n title d "Contaminated and N atural load .riviroasents o f Han" , c a l ls f o r c r i t i c a l comment in the i n t e r e s t o f a soewhat more balanced Judgment concerning th is s ig n if ic a n t issu e o f environ- rritntci^. l i e a l t n . In p re sen tin g an in te r p r e ta tio n of c e r ta in geochemical observations made by h im self and h is a s s o c ia te s , w ith re s p e c t to th e abundance of le a d i n c e rta in oceanic s tra ta , as a clue to the a r ti f ic i a l dissem ination of lead in the p re se n t environment o f man, th is author i s w ith in M s own f ie ld and is e n ti t le d to a re s p e c tfu l hearin g , su b je c t to th e c ritic is m s of colleague's i n cccira rafale f i e l d s . His subsequent d iscu ssio n o f various g e n eral and s p e c ific means fay which le a d , removed frees th e depth o f th e e a rth , has been subjected fay a n cien t and modem man ho & v a rie ty of processes and u se s, -and so has been s c a tte re d about in unnatural prov isio n upon the e a r th 's su rfa ce , has the au th en tic flav o r o f th e g e o lo g ist's view of such n a tte r s , and speaks o f an im aginative approach to the phenomena o f h is chosen f i e l d . His soaewhat disingenuous im p lica tio n th a t m edical in v e s tig a to rs rave ignored a r t i f i c i a l c o n trib u tio n s to th e n a tu r a l content o f le a d Sit the human environment, and th a t th e term "n o rm l" has been regarded a s synonymous w ith "n atu ra l" in t h i s re la tio n s h ip , io b e lie d by n o d ica l l i t e r a t u r e , in which many a r t i f i c i a l sources o f lead in th e environ merit have been id e n tifie d in se a s d e t a i l , and lis te d c o lle c tiv e ly by m yself ( J .I .H . 15:-- 1933), among o th e r in v e s tig a to r s , w hile "normal" in m edical parlance has been deHnsd repeatedly, and often s e t in quotation marks to in d ic ate the u su al, cu rren t s ta te of th e environment or of c e rta in responses th e r e to . T his, however, i s a m a tte r of minor semantic importance and may be taken lightly* U nfortium tely, th e re a re o th e r t a t t e r s in th e a r t i c l e which may n o t be glossed over, fo r Dr. Patterson M s ventured, w ithout caution, hum ility or appropiate c ritiq u e , in to what i s c le a rly , fo r him, an a lie n area of biology, \ lias developed h is own ic o n o c la s tic th e s e s , and lias ra is e d c e r ta in questionyin o rd er to answer them w ith th e boldness, passion and d isre g ard f o r troublesome fa c ts th a t wore b e fit z e a l in the advocacy of a cause than the a ttitu d e o f the seriouo -investigator. I f proof is needed of h is u nfam lliarity with the fie ld , V -J? atten tio n ia called , in passing,to the naivet4 which characterizes h is accept- Sr- ance o f certedn items of data with which to Illum inate hie statem ents, and to his tran slatio n of ce rta in dubious s ta tis tic a l co rrelatio n s into factu al evidence. As an example of the la tte r ty p e, th e highly questionable issue o f one's absorption o f sig n ific an t q u an tities (asureable by any acceptable means) of lead while smoking, which is based solely upon th in , in fe re n tia l s ta tis tic a l correlations (US Public Health Service Publication No.999-AP-12, 1965), in the face of the fa c t th a t the g reat bulk o f the lead in and^m^tobacco remains in * the discarded ash of the c ig a re tte (J . Roy In s t. Public^am Hyg. 24 76-77, " iy 6 l, and Tobacco 144 24, 1957),''s e ttle d fo r Dr. P atterson, who even gives i t q u an titativ e expression. Further^ as only one instance o f an unhappy choice o f evidence, is h is relian ce upon a statem ent in the lite r a tu r e (Schweis Med Wachr. 8?: 1171, 1957), th a t the p o ten tially harmful threshold of concentration o f lead in the blood may be as lew as 0.05 mg. per 100 grams (given in the te x t as 0.5 ',,arts per m illio n ). Hie cred u lity th a t is represented in th is choice i s excusable, in view of the experim ental and c lin ic a l variables th a t must be taken in to account in the quantitative ap p raisal o f even recent se rie s of analy tic a l data, but is so demonstrated, nevertheless* Hie foregoing c r itic iso s might w ell be regarded as tr iv ia l, were they not indicative of the quality of the author's judgment of the worth of evidsice - taken from unfam iliar sources. Hut a much sharper atten tio n must bo focused upon the v a lid ity o f the two p rin cip al arguments in Dr. P atte rso n 's th e sis, fo r these are crucial.- Hie f ir s t of these is his estim ate of the n atu ra l body burden of lead "which prevailed (in man) during the creation and evolution of (his) physiological responses to lead". The second ia concerned with the "definit ^indications th a t residents in th e United S tates today are undergoing chronic y vi^iead in s u lt" . As he develops these two p o in ts, and a s they are interwoven in h is te x t, they sees to derive increasing weight from the complexity of the inferences and interpolations on which they are based." The la tte r , p a rtic u la rly those concerned w ith a d e ft handling of various selected elements from th e periodic ta b le , may be viewed with scepticism , i f not d is tru s t. (Why, for example have H thitra, magnesium and aluminium, which hardly f i t the p attern s of the argument, been excluded from c e rta in tab u lar comparisons o f the elements? And by what magic have the n atu ra l body burdens o f germanium and thallium been calculated, when these elements have not bean found in the human body under ordinary circumstances^}. However, in any c r itic a l appraisal o f the major issu es, these su p erficially impressive and abstruse arguments f a i l dism ally, not so much because of th e ir in trin s ic fa u lts , which are d iffic u lt to assess, but " uut because of th e so lid weight of evidence which i s opposed to them. Only a CO portion of such evidence, presented p re fe re n tia lly here because of th is c r i t i c 's first-h an d assurance of i t s r e lia b ility , as wen by years of increasingly CO CO c ritic a l experience, ie required for th is purpose. ct> In estim ating the body burden of lead in prim itive man, as a b asis fo r the appraisal o f the re la tiv e magnitude and significance of the contribution made < Ut to th e ir environment by a rtfu l and technical men through the cen tu ries, Je Dr. Fatterson has mentioned, only to dism iss, the relev an t data obtained by the d ire c t analysis of m aterials collected in th e course o f two expeditions in to prim itive areas of the e a rth . Hie f i r s t of th e se, planned and carried out in people and th e ir environment on the Mexican plateau. The second, only a l i t t l e la te r, was concerned w ith the co llec tio n , 1jy proxy, of vegetation, prim arily, (a number of samples of s o il were obtained), from jungle areas in the Yucatan Peninsula and in the Par E ast, in containers and In s tr ic t accordance w ith instruction supplied by myself and ce rtain an aly tical associates in the s ta f f of the K ettering laboratory in the Medical Center of the U niversity o f C incinnati. (C ertain Other specimens of vegetation vero obtained from sueh widely separated p arts of the earth as Trinidad, Sarawac and Ceylon, among others, th a t were judged to be free of contamination from in d u stria l or other a r tif ic ia l sources. These data have been assembled recen tly , out o f several a r tic le s , fb r republicntion co llectiv ely (J.Eqy. In s t. Public Health and Hyg . 24 81-97, 1961) No vurther mention w ill be made of them here, since more j d e fin itiv e inform ation in scope and sig n i fcam e wifeSe obtained in the investigation of the Mexican Indians. Dr. P atterso n 's rejectio n o f the re su lts of the Mexican survey was based, i t seems, on the re la tiv e u n re lia b ility of the procedures employed a t th a t time fo r the analysis of the notarial obtained (these are described in d e ta il in association with th is and other a r tic le s published with i t ) , and on the "discovery" th a t these subjects made use of lead-glazed pottery (th is was no la te r discovery, but was, rath e r, one of the m atters duly observed and reported fu lly , together with analyses o f the p o ttery , as a p a rt o f the ap p raisal of the environment o f the Indiana (J. Ind. Hyg. 15s 257-72, 1933)* However, these findings cannot be disposed of so lig h tly , fo r reasons which must be made clear* A prelim inary survey of the experimental s ite s (chosen fren? several others w ithing the broad plateau^hhd brought to lig h t only one a r tif ic ia l fa c to r, of ancient origin, represented in the use o f lo c a l, native pottery, some of which, including the f l a t p la tte r (36-18 inches in diameter) on which to r tilla s and certain other a r tic le s , mostly meats, were codeed, had been coated th in ly with a lead-containing g la ss. These (oneto the household), and a very few other earthenware u te n s ils , were generally used for a long tim e, fo r th e possessions of the Indiana were meager, and since these had been subjected to slow heat and animal f a t, they had acquired a patina w ith time and use. Ct>nervations of g lass and glased surfaces th a t have been fired by tra d itio n a l methods^ have shown th a t when, as in cooking, they are lo f t undisturbed by scouring or by contact w ith corrosive substances, to prevent ``stick in g ', they y ield up only minute, almost n egligible amounts of lead . I t should also be^E&own to those without fa m ilia rity with iso lated Mexican Indians, th a t they were unaccustomed to the use of dining tab les or tab le ware. They ate tuch of th e ir food in i t s n atu ral s ta te , out of doors, or indoors while seated on the earthen flo o r, or on the u at of woven vegetable fib e rs which served as ta b le, ch air or bed. They employed ro lled or folded to r tilla s as p la te s, knives, forks and spoons in handling liq u id or cooked foods. Hence, i t i s h i# 3 y probable th a t the extraneous portion of th e ir ingested lead came more from the inevitable contamination o f th e ir food and beverages (and fin g ers) with pulverized earth,than fresa th e ir lim ited use of p o ttery . I t is evident th a t n eith er of these facto rs can be ignored in obtaining an estim ate of the minimum quantity of lead th a t might have been ingested d aily by the a d u lt, male Indians from purely n atu ral sources, th a t i s , from th e n atu ral ocurrence of lead in the substance o f the odible vegetation i 4. and in the flesh o f animals th a t fad on vegetation and other an in als. I t is equally evident, however, th a t earthy contamination has been an inescapable facto r in the lead content o f th e food o f the most prim itive o f men. Suffice i t here to say th a t tills experimental survey was designed to provide an answer to th e question of the abundance o f lead in a prim itive environment o f mani as compared w ith th a t in the complex in d u stria l and tech nological envir onment of modern man in the United S ta te s. I t la a lso p ertin en t to c a ll atten tio n to the fa c t th a t th e d istrib u tio n o f the degradation products o f te tra e th y l lead on th e e a rth fs c ru s t, a t th is tim e, was o f small proportions in a re la tiv e ly re s tric te d area, and th a t i t was not a fa c to r in the an a ly tic a l findings o f th is survey. Moreover, carefu l inquiry, confirmed by the records in the Federal D istric t of Mexico, demonstrated th a t no mining operations had been carried out in the general region of the in v estig atio n . Ordinary observ atio n served to show a lso , th a t there were no fa c to rie s, no in d u stria l operations, aid no w ater pipes o f any kind, in the area. As to the actual investigation, having Judged the s ite s to be sa tisfa c to ry , I arranged for the shipment, freta the K ettering laboratory,of su itab le containers fo r samples, and accompanied them to tbs s ite s , where I co llected , in person, samples o f su itab le s iz e , in re la tio n to the s e n s itiv ity of t i e an a ly tic a l .methods (see L ater), of the item s of the food th a t entered in to the d ie t o f the Indians, from the fie ld s in which many of them were growing or liv in g (ani- a ls ), end frerc th e stream, households and th e few places of storage. A number of samples o f s o il were collected a lso . From the people, representative specimens o f faces (one evacuation), urine (large volumes o f two or more l i t e r s ) , and blood (40 to 50 ml) were collected. (For reasons th a t need not be discussed here,the re su lts of the analyses of specimens of blood, as given in the o rig in al publication cited previously, nay w ell be disregarded, in favor of those obtained 3ome years la te r and analysed by present highly sen sitiv e methods. Specimens of / / urine were also obtained fo r an aly sis, a t th a t la te r tim e, by,psthods of sampling th a t have found to be sa tisfa c to ry . (The mean values o f series of resu lts, of very low v a ria b ility , were of the order of 0.02 mg of lead per 100 grams of blood, and 0.02 mg. o f lead per l i t e r o f u rin e, both o f which are in the lower th ird of the range o f the re s u lts obtained in the United S ta te s). I t was not possible, under the conditions th a t existed in the fie ld , to follow the alim entary intake and output o f lead by individuals, nor was i t feasib le to obtain sa tisfa c to ry data as to the lead content o f the ambient atmosphere. The specimens of food (and water) were viewed c r itic a lly from the aspect o f th e ir freedom from contam ination. Those th a t had been cooked or stored, and those which had been exposed to dust in the fie ld s , because of th e ir manner o f growth, were regarded as contaminated. Notes were made fro which the re su lts of analyses of th e la tte r types of growing vegetation were marked in the published data to in d icate th a t lik elih o o d . Other re su lts could safely be a ttrib u te d to the n atu ra l lead in the specimens, since these had been shielded effectiv ely from ex tern al contamination u n til they were enclosed in th e containers. An estim ate of the to ta l quantity o f lead in a composite d aily d ie t n&de up solely o f such uncontaminated a r tic le s could be made w ith a reasonable approximative to y the actu al fa c ts . A fa rth e r estim ate o f the d aily alim entary in ta k e ^ fa r1' ccaxparative purposes, could be made from the re s u lts o f tb s analyses of the j^ 000'( Bl3 5. feces o f the subject, since such findings have been found to y ield a sound portrayal o f th e q u an tities of lead ingested during th e period correspond ing physiologically to th a t involved in the accumulation o f feces fin* evacuation. Such estim ates, which w ill be given la te r , are adm ittedly rough in the s tr ic tly q u an titativ e sense, but they are cle a rly Indicative o f th e order o f magnitude of the values under discussion. The m atter o f an a ly tical precision i3 obviously p e rtin e n t. The d ata, as reported, e rr system atically on the low sid e, fo r the reason th a t the methods used a t th a t tim e, while yielding reproducible and sp ecific (fo r th e metal concerned) re s u lts , were of a lower order o f s e n s itiv ity ^ aa- uiaf a& fiiiu those which were developed la te r and used in the K ettering Laboratory since 1937-38. For th is reason they fa ile d to d etect lead in the m aterial analysed, when the to ta l quantity was le ss than 0.08 1 0.003 mg., and always gave a low value, by th is much, when lead was present in the sample, as analysed, in msasureable q u an tity . This was counteracted to some extent, but never fu lly , in view o f the^order o f magnitude o f th e q u an titie s o f lead d ealt w ith, by the co llectio n o f specimens of large volume or weight. The an aly tical data have been reported, as obtained, without any correction, since, in view of the approximations represented in the estim ates o f tbs alim entary intake of n atu ral lead on th e one hand, and o f to ta l lead on the other, such corrections would have implied a fa lse degree of precision in such estim ates. I t 3 su ffic ie n t fo r comparative purposes to indicate th a t the d aily intake of lead in the two categories (natural and to ta l) by the adult males (no women were included) among these Indians was not le ss than 0.10 or more than 0.15 nig. per day. Such an alim entary intake can be estim ated, in d ire c tly , but w ith a high degree of p robability based on extensive m etabolic data, to be consistent w ith a body burden of lead o f the order of 40 to 60 m illigram s. 2. The more im portant/ feature o f Dr. P atterson's paper is his conclusion th a t th e present le v e l o f tha contamination, by lead, o f the general environ ment in the United S tates, specially i t s atmospheric component, poses a serious th re a t to the health of the general population. This conclusion f lie s in the face of a so lid body o f re lia b le evidence to the contrary. I t should be pointed out, a t one, th a t the lead in the food and beverages o f c itiz e n s of the United S tates is a la rg e r and more variable fa c to r than th a t in the air* So one can deny th a t the exposure o f modem man to lead is considerably g reater th a t th a t o f prim itive man, nor can one be assured, a t th is point in tim e, th a t such exposure* may n o t, without appropriate surveillance and adequate precautionary measures, reach dangerous proportions a t some fu tu re tim e. I t i s precisely because o f the la tte r p o ssib ility th a t our systematic invest ig atio n s of the past th ir ty years have been undertaken and continued, to estab lish fa c ts , hygienic c r ite r ia , and methods of monitoring both environmental conditions and people, whereby the hygienic sta tu s o f our population, in th is regard, can be determined w ell in advance o f any th re a t. These ends have now been accomplished in large p a rt. C rite ria o f safety , with respect to the lead content of food and beverages, have been s e t, on physiological grounds, under conditions in vfoich the lead content o f th e a i r is maintained a t a constant le v e l. Sim ilar c r ite ria fo r the lead content of the a ir , when th a t o f food and beverages is maintained w ithin i t s present lim its of v a ria b ility , are fa r along in the making. The p rin cip le on vgrLch these c r ite r ia are based i s th a t 6. of the determ ination o f the combined q u an titie s of lead from food, beverages and a i r , which can be taken in to the healtfty human body from day to day and year to year, without a measureable degree o f accumulation of lead in the body. The evidence of balance experiments, carried out with healthy men in the Laboratory, p a rtia lly reported (J. Roy, In s t. Pub, Health and Hyg. 24:81-97, 1961), has indicated clearly th a t, under present environmmtal conditions in the United S tates, individuals take in variable q u an tities of lead reg u larly , and th a t they elim inate lead from th e ir bodies, reg u larly , in su b stan tially equivalent q u an tities (w ithin w ell defined lim its of experimental deviation), maintain ing theselves in su b stan tial equilibrium w ith th e ir environment throughout a l l but the early years o f lif e , during which tjie mixed component^of th e ad u lt d ie t are being added to the in fan t d ie t and equilibrium with the environment is being achieved. There has been no demonstrable increase in the intake and output of lead of individuals in the general population of the United S tate s, or in the le a d ^ ^ content of the urine and blood of representative groups of persons^S ij^n^^he past thfeOty y ears. On the contrary, there is highly suggestive (but inclusive) evidence th a t the to ta l intake of lead by such persons ia lower in the present decade than i t was in the two preceding decades. I t is also lik e ly , on the b asis o f in d irec t evidence, th a t th is le v el is lower in the United S tates than in certain other countries. Be the la tte r indications as they may, the hygienic problem, w ith respect to lead in the environment of man, i s not whether th ere is more or le ss lead, te r se, but whether the q u an titie s are w ithin lim its th a t do not tax , unduly, the physiological mechanisms o f the human organism for coping with them. The physiological responses to lead in the general environ ment (excluding occupational and other unusual types of exposure) of ordinary c itiz en s of the United S tates are adequate, and. the only question to be i'' raised and answered, i s whether the le v el o f c o n c e n tra tio n s' the body, incident to the stream o f lead in and out and through the tis su e s, is actu ally or p o te n tia lly harmful. Simple apprehension, because lead has so long been known to be dangerous under various poorly assessed conditions, may give ris e to th e b e lie f th a t i t may be, and therefore probably i 3 , harmful in any q uantity. The fa c ts of physiological research and c lin ic a l medicine speak otherw ise. The toxic a ffe c ts o f the absorption o f su ffic ie n tly large q u a n titie s o f lead, in c e rta in o f th e ir more obscure m anifestations, are appreciated more fu lly , in biochemical term s, than they have ever been previously, and the conditions of dosage and tim e, Tinder which lead poisoning occurs in th e in fan t or ad u lt, have been c la rifie d to such a point th a t gross differences are now d iscern ib le between the q u an titie s associated with to x ic e ffe c ts , and those which gain entrance to the individual from the sources in the general o r common environment* There a re , a t present, c lin ic a lly and s ta tis tic a lly v a lid expressions o f a ' dangerous degree of absorption of lead in the individual. (There ttfrmare than one, but I choose the most p re c ise ). I have never seen a case of lead poison ing iron the absorption of the inorganic compounds o f lead, in an untreated ch ild or a d u lt, a t th e onset o f illn e s s , l.e * in immediate temporal re la tio n ship to the period of absorption, whose whole blood contained le ss than 0.08 mg. o f lead, when analysed by methods (in p a ra lle l) of a se n sitiv ity and accuracy equivalent to those employed in th e K ettering Laboratory since 1938. ( I t should be taken in to account th a t tha body burden o f lead, as represented by th is u vq uft1<o l o 7. concentration of lead in the whole blood o f persons who have not been subjected to chelation therapy, and who have not been poisoned by a very b rie f period of ex trao rd in arily high dosage, ranges fran 4 to 20 times th a t o f persons in the general population). The d ifferen ces, then, between the q u an titie s o f lead, in terras of dosage or o f body burden, th a t are associated vrith lead poisoning, and those th a t are represented in the general environment or in the bodies of persons in the la tte r environment, are not small (in re la tio n to th e methods of measurement), nor do they overlap, nor are they lik e ly to be confused by knowledgeable persons. Dr. Patterson would have done w ell to have examined the available inform atio n more ca re fu lly , before making the astonishingly dogmatic (and absurd) statem ent th a t "the threshold fo r damage concept as i t applies to lead, is an ill-d e fin e d opinion unsupported by any ( ita lic s mine) evidence" . The fa c ts, s e t fo rth clearly in medical lite ra tu re , are th a t the periodic in v estig atio n of the content o f lead in the in d u stria l environment, hand in hand with a meticulous search fo r c lin ic a l evidence of frank or vague illn e s s attrib u ta b le to th e absorption o f lead, in association with periodic in v e sti gations of the lead content of the feces, urine and blood of workmen, has disclosed d e fin itiv e relatio n sh ip s between the chemical findings and the incidence of lead poisoning in any detectable form. The ''Threshold fo r damage concept" in actio n , on the basis o f many years o f experience in many in d u stries th a t make use o f lead , predicts th a t no case, not even an occasional mild case, o f lead; poisoning w ill occur, unless the physiological threshold value is exceeded. (The threshold value fo r lead in the a i r o f in d u stria l establishm ents is not dependable to th is ex ten t, for the reason th a t i t does not apply to the to ta l environmental hazard but only to i t s resp irato ry component). The threshold value o f lead in the ambient a ir of a community haa a d iffe re n t bases in time than th a t o f industry, th a t i s , i t is e ssen tially continuous, ra th e r than in te rm itte n t, and so i t must be worked out by a d iffe re n t experimental method. On the other hand, the composite physiological evidence o f tte extent and significance o f the exposure to lead is the same in the general as in the in d u stria l population, so th a t danger can be detected and an ticip ated , by properly designed surveys o f representative groups in the population. Such surveys, fiv e of which have been made since 1927, including the la s t in 1961-62, made jo in tly by representatives of the United S tates Public Health Service, the Departments o f Health of th e C ity o f Philadelphia and the S tate o f C alifornia, and the K ettering laboratory, have found no evidence of any current th re a t to the h ealth o f representative "urban populations in the United S tate s. basic physiological investigations o f the p ast th irty years have given t h e s e v a l i d i t y which the data concerning the lead in the atmosphere and the lead in the blood of the su b jects, could no t, of themselves, have claimed. In th e ir composite weight, they show th a t th ere is no present th re a t to the health o f the population of the United S tates from the q u an tities of lead which occur (w ithin w ell documental, ranges o f concentration or quantity) in the food and beverages and in the ambient atmosphere of our communities. They have indicated, fu rth er, the wisdom o f measures o f co n tro l th a t are now being exercised, by ce rta in governmental, in d u stria l and professional agencies, and the b en efits o f the educational e ffo rts th a t have brought improver nts in . 0 y u < .1 ^ 8. the production, handling and processing of foods and beverages in the United r - ~ -- S tates. Experience has shown th a t there is a continued need, moreover, fo r t t a constant alertn ess in hygienic c irc le s , fo r the avoidance and c o n tro l/o f'tiie * p o ten tial hazards of a technological society. ^ F inally, l e t me say, in term inating these unusually lengthy and d etailed cotstasnts, le s t i t appear th a t I am c r itic a l o f the e d ito ria l policy th a t has presented th is paper to a s c ie n tific and professional audience, th a t such is not the case. The substance of Dr. P atterso n 's paper lias been circu lated in p riv ate communications, and presented to a t le a s t one o f f ic ia l agency, so th a t i t had more than a l i t t l e impact, in professional and lay c irc le s , before i t s formal publication. I t -was e sse n tia l, I believ e, th a t i t be brought in to the open fo r professional appraisal, and i t would sesa th a t the Archives o f Fnviroisasntal Health i3 an appropriate place fo r i t s publication. Faithfully yours, Robert A. Kehoe, k f= UAuA' l!i' 0A.1 ri;