Document MM0e7BDgEqx86D67k9r8bbxXa

INTERNATIONAL LEAD ZINC RESEARCH ORGANIZATION, INC. I -T J September 18, 1973 PBS MAOlSQN AVENUE, P.'EVV VORK, N. Y. 10017 t e l e p h o n e aa-a37ti i a r e a c o d e aiai CABLE APOWERS; NYILZBO NEW YORK ^-133 -S3a-a373 TO: H, E. Hesselberg R. ButleryV" J, C. Calandra E. J. Gay fl. Sugimoto OjST' tptsraf/" <? . FROM: D. R. Gentlemen: Enclosed ape-'Cwo items which may be of interest. entitled, "Biological Quality Guide for Inorganic Lead", by Prof, R. L. Zielhuis. This paper was received from Dr. Zielhuis who indicated that it had been sent to the Bivision of Health Protection, Economic Community of Europe. It was further indicated that the report has been submitted for publication to a Scientific Journal and at this time is not officially released. 2. Letter from Br. R. A. Willoughby, University of Guelph. At the ILZRQ Idea Meetings in May it was proposed that we ask Br. Willoughby for his comments regarding the research work of Br.. Buck in Iowa. If you have any questions or comments about these items, please let us know. Sincerely, 'V *V V 1;:- Vt iV. Donald R, Lynam, Ph.D. Assistant Manager Environmental Health jm encs. cc: J. F. Cole E, B. McCabe TEH 0470252 \P ejS/'/rfrcn On BIOLOGICAL QUALITY GUIDE FOE INORGANIC LEAD esaaaitsaaasgBsssaasaasacsaasagsgaaaSJBMgasa .+ Prof.Dr R.L.Zxelhuis, Amsterdam Environmental quality standards and guides g;sss;sga:3;sssssas=suKSSs;as:g^:s:ag:ss:=ssssssaBssA Environmental quality standards are tools for governments to achieve and maintain environmental quality$ they are the outcome of political decision making, taking into account scientific data, economic possibi lities, socio-cultural factors* etc. Environmental quality guides are .recommendations by scientific advisory bodies * mainly based upon doseresponse curves (criteria), only taking into account effects on fcuman beings .(public health), plants, animals and material (Zielhuis 1973) Standards and guides may be issued for air, water, food, etc. If a noxious, .substance is predominantly present in air, 'an air qua lity standard." may serve the objective of protecting health. However, if the target (we will limit ourselves to human beings) is exposed to this agent by various routes of entry (e.g. respiratory* oral, dermal pathways) neither'an air quality standard nor a food (water) quality .standard will achieve adequate protection. The total environmental load has to be taken into account, In the ease * of inorganic.lead it is a well established fact that in the sphere of public health oral uptake may give a greater contribution to the body burden than respiratory uptake. In industry respiratory exposure is predominant, and in that case an air quality standard (Maximum-:allowable concentration. Threshold limit value) .may serve the objective of protecting health-of workers, whereas in public health emphasis upon one single.route of exposure does not assure adequate protection. Ambient air quality standards therefore only serve the objective of protecting public health if exposure takes dace solely or predominant ly by way of inhaling ambient air. In the case of e.g. lead, cadmium, mercury, ambient air quality standards as such apparently do not achieve this objective. An other approach has to be taken. +\ . ' Coronel Laboratory, Faculty of Medicine, University of Amsterdam. 1st Constantaju Huygensstraat 20, Amsterdam, The Netherlands Part of this study was supported by a grant from Direction Health " nnnira-. Luxembourg 'TEH 0470253 ^ DUP050033071 N42444.01 't'S . f: In this paper this alternative approach will he discussed. A pro- .V posal will be worked out for inorganic lead exposure; a similar ap- V* proach appears to be feasible for many other environmental pollutants. Exposure - response In regard to exposure one should distinguish: 1. external exposure: concentration in air + duration of exposure; 't presence in food, water, etc., on skin n-? 2. external load: the real amount of agent offered to the body per V'-*. unit of time, talcing into account respiratory volume, particle a size, oral uptake, skin penetration, etc. \\ 3. internal load; the amount present in the hody as consequence of 1_ and 2 and of elimination; in the case of inorganic lead to be distinguished, into (Pietrowsky 1970): :.* - rapid exchange pool (blood, soft tissues) - intermediate exchange pool (muscles, skin) ; :r- - slow exchange pool (bone). A relationship exists between various parameters of exposure: t , 1 lead in blood (.PbB) indirectly reflects* external exposure and ex ternal load, and it also indicates the internal biologically availa ble lead, the "real" dose; lead in urin (with or without provocation) : * may serve* the same purposes. a If the no-effect level in the dose-response relationship is ex ceeded, effects will occur1; effects of biological systems serve as parameters of response; in case of lead: disturbed porphyrin synthe sis, obstipation, lead colic, encephalopathia, disturbed mental de velopment, etc. Because there exists a relationship between internal . ** load (particularly rapid exchange pool) and effect (qualitative and quantitative), effects may indirectly be used as predictors of in ternal load, and of* external exposure. < t: j >i< TEH 0470254 DUP050083072 > ^V <' $ 4 I I . 'v.V I ".-f:Cv >! 3 Sequence of operation Because the ultimate objective is to prevent adverse effects on public health, parameters of response should first be taken into ac count*, one should determine the dose-response relationship. Dependent on the acceptability of effects from the viewpoint of public health, the acceptable internal or external dose should be determined. Such a sequence of operation is implied in establishing air quality guides for e.g. SOg, particulates, NOg, 0^. The fact that Pb enters the body through various routes, complicates the setting of guides, and consequently of standards. In the case of inorganic lead as a public health problem, the se quence of operation should be: 1. determine relationship between internal load and response (effects) 2. determine acceptability of response (For extensive discussion of the sequence of decisions to be taken see Zielhuis 1973) 3. determine levels of lead in blood (hair, teeth, urine, possibly after provocation test) which correspond with no-effect-levels or no-adverse effect levels. These levels represent the acceptable quality of biological systems, e.g. expressed as Fb in blood or Pb in urine, and serve as biological quality guides 4. determine relationship between biological quality guides and to tal uptake (pro unit of time, and duration of exposure): accepta ble total external load 5. determine contribution through various routes and sources to this acceptable total external load 6. determine various quality guides for main sources of uptake: food, water, air 7. determine various emission guides based upon the contribution of sources of emission to sources of uptake 8. various guides become standards, if imposed by governmental au thorities. TEH 0470255 DUP050083073 I. -1, - Contribution from oral uptake In the USA the Env. Protection Agency (EPA) (1972) suggested that r'l O further reductions of air lead concentrations below 2,,.g/ra ap peared to be indicated; they based this suggestion upon: 1. an assumed average daily intake through food and water ). ! 2. an assumed relative contribution of traffic exhaust to sources : of uptake. ~i USSR issued ambient air quality standards for lead (0.7//") dis regarding uptake through food and water. However, there are strong indications that oral uptake of lead may differ considerably ; .< - between individuals in one region i - between various, regional groups. The average uptake does not enough take into account the tails of the distribution curves, in UK average uptake is about 200,.*g/Pb/day, with extremes up to 1(00 * Fb/day (Martin 1973) ; Thompson (1971) found a range of 70-750 .-^g Pb/day in '$ individuals in UK; Lehnert et al (1969) calculated for Germany (FRG)' ah average uptake of 518" Mg Pb/day; Wigliani et al (196 ) suggested for miland b00-500 ,g Pb/day. Zielhuis (1972a) calculated that within Western Europe average uptake probably differed by a factor 2 (and individual uptakes therefore by a factor much larger than 2) between various, regions. Considerable differences probably exist between (and also within) Western Europe and USA in e.g. 1. relative contribution of Pb in paint ' ,'T ' . 2. relative presence of pica 3 relative contribution of Pb in wine, beverages, foodstuffs U. choice of foodstuffs. .( ,:;V 4 In Europe one can only' use American data on the relationship between total uptake - internal load - response, and not data on e.g,. rela tionship between Pb in air and Pb in blood; this may even be true in comparing various European regions. The group of experts on lead, convened by the Div. Sanitary Pro tection Eur. Econ. Comm. (1972, 1973), agreed that not enough know ledge is available in regard'to oral uptake (average and range) in Western Europe; it proposed investigations to gather relevant data. The conclusion of this must be that in such a situation adequate air qualify guides and standards also cannot be recommended. DUP050083074 TEH 0470256 The UBe of biological quality guides Parameters of internal load and of response in human subjects may be used for indirect monitoring of total environmental exposure, be. cause there exists a clear relationship between external load and internal load (or response). Biological quality guides (or standards) refer to acceptable le~ ' vels of parameters in biological specimen in selected groups of human subjects; they indirectly measure the acceptability of the macroenvironment , Groups of subjects live in a certain environment (region, area, city) and are exposed to the agent under discussion through e.g. res piratory and Oral uptake. In addition some individuals may have a specific micro-environment, due to peculiar food habits, environmental situations in their house or living (working) conditions; they may . therefore exceed the given guide levels, not because the macroenvironment for the whole group exceeds acceptable levels, hut because the specific situation for these single individuals is "abnormal". If within a group one or a few individual subjects exceed the guide levels, authorities should take action in regard to the micro-environ- .. ment of these individuals. If however the group as such exceeds the guide level, there exists an unacceptable macro-environment specific for the group under discussion; this indicates a signal for action in regard to the total environment of the group. | As a matter of choice, one may take two as the percentage of exfl ceptionally exposed subjects within a group; 9&% of the group should V i not exceed acceptable level. iff Target groups 'XV- Groups serving to monitor the ambient environment should be care -1.... fully composed; ... v; 1. at least 50 subjects, preferably about 100 2. the group should represent high risk groups, either in regard to exposure, or in regard to susceptibility; if these high risk groups ' I do not exceed guide levels, one may conclude that the environment of other population groups will also be acceptable (the reverse is not necessarily true) TEH 0470257 DUP050083075 3- similar social-cultural class U, narrow age range, e.g, children 1-1 yr, pregnant women 20-30 yr, traffic policemen 30-10 yr 5, same sex 6. the subjects should live for the greater part of the day in the environment tinder discussion. percentile distribution Even within target groups, as aiscussed before, biological levels of exposure or response will not be similar, due to difference in food uptake (quantitative, qualitative), habits of playing (indooroutdoor), susceptibility, rate of absorption, etcetera. The environ ment Snd the susceptibility may differ for individual subjects, even within a carefully composed target group. The macro-environment should protect individuals living in it, even with their "normal variability" in way of living and in susceptibility, only disregarding about 2% of individuals with clearly exceptional exposure. It is therefore not allowed to propose only one acceptable level* not to be exceeded in any member of the target group, as done by EPA (1972). The distribution of levels should be taken into account. If one chooses only one acceptable level, the exposure' for all group members with lower levels could be increased. Such an approach is not feasible, because it does not take into account the "normal variabi lity" between human beings. Therefore, a biological quality guide should give an acceptable distribution of levels; it serves as a guide for a group-environment, and not for a single individual micro environment . The distribution of levels can be given as such, but it is more appropriate to give the cumulative percentile distribution up to e.g. $0? (median value), 90" and 93;? of members of the target group. If one has to propose biological guides for xenobiotie agents, one should also take into account that - due to insufficiently developed or absent homoiostatic mechanisms - levels in blood and tissues show a skewed distribution, e.g, blood levels for Pb, Cd, Hg in contrast to levels for Ca, Zn, Mg. This is another reason to use percentile distributions, because with skewed distribution average (arithmetic) TEH 0470258 DUP050083076 /< * T, '3 .i I'! & ' ,.v> * *-*.JtV-r*4H-. . .;$ -7~ levels end standard deviations do not give an adequate insight in the range of levels occurring, '.'any literature sources only present e.g. arithmetic average, standard deviation (not allowed in shewed distributions) and range; such data do not present enough informa tion on the group as such. Moreover, in setting guides and standards the tails of the distribution (increased exposure or susceptibility) very often have to determine the acceptability of exposure to the group as a whole (Sielhuis 1972b). Maximum individual acceptable level of lead in blood In the Amsterdam Symoisium on Environmental Health Aspects of Lead (1972) the author discussed the question whether "an internal chemical load as indicated by PbB levels up to 4o /4.g Pb/100 ml pre sents any risk to public health" (Zielhuis 1972). The following con clusions were drawn: 1. the no-effect level of PbB in regard to increased excretion of -aminolaevulinie acid (ALA) in urine is about 1*0 /.g Pb/100 ml (see also NAS 1972); 2. there are indications that the no-effect level of PbB in regard to decreased activity of ,c-ALA-dehydratase (ALAD) in erythrocytes is 5-15 ,.,6 Pb/100 ml; 3. the no-effect level of PbB in regard to increase of protoporphyrin in erythrocytes (PPE) is at least 40 Pb/100 ml; 4. various effects on erythrocytes (e.g. lifespan, Ha -K -ATPase activity in membranes, K+efflux), various other biochemical ef fects (e.g. immunobiological activity, alk. phosphatase, aminoacid uria, serumprotein pattern), various clinical effects on kidney function, vascular tension, cerebrovascular incidents probably do not appear in subjects who never exceeded PbB ~.40/<q Pb/100 ml. Some of these conclusions merit further discussion. Decrease of ALAD activity is apparent already with PbB <,40 Fb/ 100 ml, with a high positive eorrelationship. Data of Schaller et al (1971) suggest a no-effect-level at PbB 5-15 /'g Pb/100 ml, but ad equate -proof is not available. An important question is whether decreased ALAD has any relevance to health, even in life time exposure. Some scientists even doubt whether the decrease in ALAD determined DUP050083077 TEH 0470259 - 8- ?* in vitro necessarily reflects an inhibition in vivo: the analytical 'method requires haemolysis of erythrocytes, Pb bound to membranes is liberated and may inhibit ALAD, which becomes extracellular; ALAD in vivo hardly comes into contact with Fb; this could explain the negative eorrelatioii between PbE and ALAD. If this hypothesis should hold true, then decrease of ALAD in vitro can not be regarded as a parameter of response, but merely as an indirect parameter of internal load. However, even if decrease of ALAD should be regarded ............. . -- i ......... .. min......... J...... 'i.i........ as an effect, one should determine whether this effect is relevant for health (in broad sense: fitness, functional capacity, "quality of life'*). HAS (1972) concludes in regard to decrease of ALAD at PbB 1(0 yg Fb/100 ml that "its biologic significance is dubious, because it is unaccompanied by any detectable effects on the biolo j-v gic function of intact man". Only when PbB exceeds 1+0 .vg Fb/100 ml t? decrease of ALAD may he significant in vivo, e.g. affecting ALA *rj' synthesis and excretion. Some studies on ALAD activity in other tis sues (brain, liver) have been performed*, in rats Millar et al (1970) found a more or less parallel decrease with ALAD in blood; s. however, at PbB 30 ;,g Pb/100 ml ALAD in the brain was not significant '.'5 ly reduced. The physiological significance of decreased activity of ALAD at a range of PbB < 1+0 .,./g Fb/100 ml should he a topic for further research; at this moment, there are no reasons to regard V decrease of ALAD activity as such as an adverse effect on health. Effects on central nervous system, manifesting themselves in be havioral changes are discussed by IAS (1972): "existing studies, if not definitive, nevertheless afford some presumptive evidence of central nervous system dysfunction". However, this conclusion was mainly based upon data in children with a history of clearly unaccep table PbB ( ; >1(0/5 Pb/100 ml), although manifest encephalopathy could he absent. EPA (1972) also summarized some studies in children with manifest lead poisoning or with asymptomatic increased absorp tion (PbB 50 ,*g Pb/100 ml); the data could not discard the possibi lity of subtle brain damage. EPA pays much attention to the recent study of David et al (1972), suggesting lead as one of the causes of hyperactivity in children. The authors themselves stress the lack of 1'I|"< ' proof. of a causal relation. Bulpitt (1972) seriously criticized the '< suggestion of such a causal relation, because the statistical treat ment had been biased. We may regard this study as a relevant indica tor for future research, but at this moment the causal relationship TEH 0470260 DUP050083078 is still speculative. The same may be said for the recent study of &e la Burde et al (1972): TO children who had bad exposure to lead (PUB 40-100 ,.v'g Fh/100 ml or over 30 v6 Pb/100 ml in combination with lead lines in long bones), but who did not experience symptoms related to it, were evaluated at 4 yr of age using a series of psychological tests; TO children with similar socio-economic hackground hut presumably without unusual exposure to lead served as controls. The authors found an increased number of deficits in the lead-group (I.Q., motor development, concept formation, behavior). The control group was not matched for psychological factors as ma ternal care, intra family relationships, although both groups came from the same basic population. The authors themselves admitted that "the differences found may be due to environmental factors other than lead": the results should be regarded preliminary; they have to be confirmed in a rigidly controlled study. Moreover, the children probably had PbB levels >40 -vg/lOO ml either at the moment of investigation, or in the past. Seppalainen et al (19T2) observed peripheral nerve damage by means of a highly sensitive technique (conduction velocity) in lead workers with no clinical symptoms; however most of the workers had experienced excessive Pb absorption, many even clinical poison ing. Hot yet published data (Hernberg 19T3) on workers never having a PbB > TO '><g/100 ml suggested the possibility of similar findings. However, Hernberg himself agreed that at this moment the validity Of these data, and the relevance in regard to health are not adequa tely studied; they can not yet be taken into account in setting gui des and standards. The same group of workers (PbB >y40 -g Pb/100 ml) Was also exa mined by Hanninen (Hernberg 19T?) with psychological methods; she found slowness of performance, psychomotor disturbance, slight in telligence defects, personality changes. In both studies no good relationship existed with PbB, ALA in urine and Hb. This might sug gest an other dose-response relationship as the one valid for com monly used criteria (Editorial, 19T3). However, so far, evidence has not been brought forward that such possible neurophysiologic effects are induced at lead levels below 40-50/ g Pb/100 ml. This clearly is still an area for research. EH 047026f DUP0500S3079 - 10 - } Recently Stuyk et al (1973) found a sex difference in- a human volunteer 3tudy (20, >g Pb/kg body weight for 3 wk): female adults showed aa increase (factor about 2) in protoporphyrin levels in ery ` I throcytes in. contrast to male adults; the levels hardly exceeded the acceptable level proposed by Albahary (1971) In addition, the authors suggested, that the relatively rapid increase in PbB might he of significance. Further studies in women with PbB 2$-35 ,g Pb/ 100 ml have to be undertaken to establish the relevance of this finding for public health. Another area for concern is the possible effect on chromosomes Although some authors reported chromosomal changes in lymphocytes in workers (Schvanitz et al 1970, Fomi et al 1971), others could not confirm this, neither in human beings, nor in animal experiments. This topic was extensively discussed at a Berlin-conference wBlei und Umwelt" (Lead and Environment, 1971) and at the Amsterdam Sym posium on Lead in the Environment (1972), No agreement has yet been reached; there certainly is not enough evidence to suggest effects on chromosomes in subjects never exceeding PbB up to ItO to 50 .- g Pb/100 ml.^ This discussion on possible effects of lead had to be very limited. Extensive reviews of literature are available (De Bruin 1971, NAS 1972, and many others). This-short review of certainties, probabilities and speculations only served to strengthen the previous ly reached (Zielhuis 1972a) conclusion that: - according to present knowledge no reasonably proven or probable y. evidence exists that health in a broad sense is affected if Indi vidual blood levels never exceed ko .-.g Pb/100 ml; - the level of PbB = kO g Pb/100 ml can be used as the' upper accep table level in the sphere of public health. Pb in blood levels generally are given as Pb in g/100 ml total blood. However, over 90% of Pb is present in erythrocytes; the hae- V*. M'id.- matocrite (Ht), indicating the volume of erythrocytes per volume of total blood, is about 1.0# lower in females than in males. Therefore Pb in erythrocytes-levels more adequately portray the real internal load (Pb in g/100 ml ery); future studies should use this parameter. PbB levels as reported in literature for females should be corrected to make them more comparable to PbB levels in males: PbBcorr = PbBobs x 1,10. If PbB - lO - g/100 ml is taken as the upper acceptable le vel in males, than PbB = 36 g/100 ml should be taken as the cor responding level in females. TEH 0470262 DUP050083080 - 11 Infancy and pregnancy The- conclusions arrived at above, need some further evaluation in regard to possibly increased susceptibility of young children and pregnant women. There exists a wide spread belief that both sub groups of the population deserve special attention in regard to pos sible health effects of inorganic lead. The main question is whether the developing infant (intra- and extra-uterine) is more susceptible to lead* particularly in regard to nervous system and behavior, than the normal adult. Pregnant women as such probably may not run a higher risk at the relevant dose levels, but they determine the load to the developing fetus and newborn. The exposure of children tends to evoke emotional involvement, and such an attitude may affect rational judgement too easily. The fact that large epidemics of serious lead poisoning, with possibly disturbed mental development, and epidemics of apparently notably increased absorption occur in metropolitans -of' the OS (and also around lead smelters elsewhere) , quite rightly.has created much concern. There apparently exists increased exposure (pica. dilapidated houses, lead.emission from smelters, street dust, etc..) in some groups of young children, particularly in toddlers. However.,..as such this does not prove increased susceptibility. EPA (1972)- summed up some arguments in favour-of increased, sus ceptibility of children: - the "speculation that children may be- suffering subtle-but unre cognised .neurological impairments" - "blood lead levels considered safe for adults may not always be safe for children; clinical symptoms often occur at lower blood lead levels in children than in adults" - the possibility of increased rate of absorption may exist; - "in view of the possibility that young children may be more sus ceptible to lead .than older children, the newborn and fetus would be expected especially vulnerable. The conservative view favors a reasonable safety-factor between what is considered an acceptable lead exposure among, the fetus and newborn compared to older chil dren and .adults". Based upon these considerations EPA (1972) came to the following upper acceptable levels of lead in blood: TEH 0470263 DUP050083081 12 ~ adults ' UO : (' Fb/100 ml expectant mothers 30 " {children fetus and newborn 30 EPA itself states that this recommendation must be regarded as a --,--| T-|- . r. .. J . . r---~|i----I immiMi jiiTTfit'T IIIi r r '' --<.*e ''judgement which has not yet been adequately validated by scienti- flc^studies". MAS (1972) also discussed the possible differences between adults and children. We quote: - ''poisoning (in children) is more likely to be recognized first at a late stage on the basis of nervous-system involvement ; adult poi soning is associated with occupational exposure, which is usually less severe than the types of exposure associated with childhood lead poisoning. When the factor of dose is taken into account, the clinical response - particularly at high doses - appears to be com parable in children and adult3. nevertheless, a rapidly growing child's response to moderately increased lead may well differ from 'that of an adult, despite the current inability to perceive the response". - ''Whether asymptomatic increased lead absorption can cause subtle but permanent impaiiment of nervous system function in young children is not known". An other argument favouring higher vulnerability in children is that the relative proportion of the body burden present in the slow ex* change pool may be smaller (Barltron 1969). The Am- Aqad. of Pediatrics (1971) stated that ho,- g Pb/100 ml appeared to be a safe limit, i.e. the same as in adults. However, the biological safety margin might be smaller in children. There are some arguments not favouring increased susceptibility in the young child, although each of them as such not presents con clusive evidence: - There is a rule of thumb that medical drug dosage for children is about n of the daily dosage for adults (n - age in years); this apparently implies a higher dosage/kg body weight in children, - Effects of drugs as thalidomide have only an effect on the intra uterine development when present during a certain circumscript stage of pregnancy; such a typical effect has not been elucidated for lead. TEH 0470264 DUP050083082 - The ad hoc Copn. 3nv. Manrgement {iJspt, Iflth Welfare PSA) consi ders 300 -Kg Fb/day as the maximum permissible daily intake from all sources for children; this leaves about 150 / g Pb/day from non food sources. Bsrltrop (1972' :;ggc:sis a permissible intake of 133 ,- E Pb/dey from food- for' a 2 yr old child. These levels are much higher than the uecepoert le-^sls for t dnlts, if taken per kg body weight or per m2` body .tnn'faee. - Haas et al ('1972) determined ?bB 5..u laibilical cord and in the pregnant mother; levels were aocut the seme, with a significant correlation (r~0.53o, n~29':). fbe uitbilical blood contained con siderably more lead than blood in 8 days ~ 8 yr. old children.. These authors did. not take into account the very large difference in composition of the blood between mother end child. According to Stave (1970) r*ad Cooke (19^5) the following differences gene rally exist in blood volume, plasma- and erythrocytvol/kg, b.w.: plasma red cell blood red cell/ red cell/ ml/kg ml/kg ml/kg blood plasma non pregnant women - pregnant, 40 wk 50 72 newborn, age 0-1 hr he newborn, age 72 hr 44-51 27 27 to il-49 77 0.36 79 0.27 85-100 0.55 82-99' 0.50 0.54 0.38 1.25 1.00 Apparently thei-e 5 s an about 3 fold difference in quotient red eell/plasma and 2 fold difference in quotient red cell/blood vol between mother and newborn at the time of delivery. A PbB of e.g, 20 :,g Pb/100 m3, in the mother may have quite another biological significance than in the neonate. This can be shown in the following example - assume PbB = 20 vg/ml in mother and neonate cone, Fb iu ery (_Ce_) assum- conc > pfjj in plasma (dn) 10; Ce 10 Cp - haemotocryt (Ht) in mother 0.27? in neonate 0.55 / amount Pb in ery + amount Pb in plasma. = FbB Ht x Ce h- (1-!!t) x Cp P'-B Ht x 10 Cp (1-Ht) :< Cp PbB Cp (10 Ht + 1 - Ht) k Cp (9ht + 1) Pb3. TEH 0470265 DUP050083083 - 14 - Cp PbB 9Ht+1 Oe lOPbB 9Ht+1 If PbB * 20. <g Pb/100 ml mother Ce - 60 : .g/100 ml neonate: Ce = 34 g/100 ml Cp = 6 g/100 ml Cp = 3.^ - g/100 ml. The same lead in whole blood indicates a lower Fb content of dif fusible plasma Pb in the neonate if compared with the mother. This phenomenon indicates an extra margin of safety for the neonate. The conclusion of this short review is that: - at levels >40,..g Pb/100 ml an increased susceptibility might exist in children at levels <.40 ,:g Pb/100 ml no conclusive or suggestive evidence for an increased susceptibility has been presented pregnant women as such {in the relevant dosage range) do not ap pear to constitute a special group to be considered in establishing guides. However, it should be fully recognized that the range of uncertainty is larger in regard to young children and the developing embryo than in regard to adults. This uncertainty as such should increase the sa fety factor, and - for the time being - decrease the upper acceptablee level. Biological quality guides - taken as an acceptable percentile distribution of PbB levels - indirectly measure the environmental exposure. It is not feasible to propose different levels for pregnant women and for non pregnant (potentially pregnant) women and male adults. So, because of this the upper acceptable level in 98% of the population should be 35 R Pb/100 ml . - Available data on percentile distribution of PbB In literature most data on P1B levels are given as average (x) and standard deviation ('") or range; individual data usually are not presented; Such a procedure may - strictly spoken - only be applied if the parameters follow a Gaussian distribution. Such an unwarranted assumption does not need to be made for percentile distribution s. TEH 0470266 DUP050083084 t' i.. ,-; - k* ;' . * .*'Vfrti -.*.. 'A 'Hi - 15 - One should express guides and standards in such a way that they are consistent with the distribution of data as occurring in prac tice, So, one should evaluate the available evidence on distribution of PbB levels as occurring in target groups of the copulation as presented in literature. Taking into account the distribution of levels as occurring in practice, does not imply that the levels as such are regarded as acceptable: not the occurring levels (e.g. U0,vg/100 ml, 50..g/100 ml), but the cumulative distribution curve - an expression of oc curring variability - is taken as granted. In table 1 percentile distribution of Pb-levels for total blood are given as calcultated from available European data (groups n >50), Two categories are distinguished: -. I. children and male or female adults, non occupational exposure, no exceptional environmental condition (vicinity of lead emitting sources) II, adults, possibly with specific living conditions. In table 2 the data of the recent 7-City Study in the USA (Tepper et al 1972) are given; mainly women volunteers, 20-79 yr, living in urban and suburban conditions. Proposed biological quality guide From both sets of data (group I Western Europe and 7- City Study) one may conclude that 98$ of adult males and non-pregnant females, without any specific non-oceupational living conditions (such as garbage collecting, wine drinking (?)) have Fb in total blood levels below about 30-35 ,-.-g Pb/100 ml, 90% below 25-30 Ag Pb/100 ml, 50# below 20,. <g Pb/100 ml. This percentile distribution can therefore be taken as a biological quality guide, because it does' not exceed 35 Pb/100 ml in 98# of the female population, and it also presents the "normal'' variability of internal load, and indirectly of the "normal" total external load. Based upon the proposed maximal acceptable PbB-level of 35,ug/ 100 ml in 98# of the target poptilation, and upon the distribution of PbB levels in various target groups, the following biological quality guide for lead in total blood is proposed, to be used in i,ubli6.hg,aAth: TEH 0170267 DUP050083085 - 15a - Table 1. Percentile distribution of PbB Pb/100 ml) levels in popu lation groups (n 50) ~ Western Europe; 9&% levels (or first higher % level) underlined. Group I source yr . curve ! number n sex ;T0 <60 ',50 4o.v35 <30 <25 <20 remarks !in fig.1 HaegerAronsen lehnert adults 1It 1971 1968 ! 1 2 I ; * :' - : i t '50 ;m loo'ioo hoo .100 '100 100 ; 100 , 94 Sweden i I ' ; j i !400 : m.f 1 100iI 100 100 ' 100 i 100j100`! 95 ' 84 `er g 1968 1 3 |il01 1; m loohf ooiioof !ioo tlooh1 oo; 99 : 93 | PEG 1968 i ^ |104 j f 100:100 :100 100i100j 1001100 ' m. . FRG i I ! Haas et 1972 5 294 i f 1001100;100- 991 98 ' 95 i 82 \ 62 ]FRG pregnant i 1* i children Moncrief# 1964 ; et al I j Millar | 1970 ! et al ! ? 6 7 80 ! m .f. 100 ! 100 1100 I 92.1 95 i 69 r 52 ; 25 DK, hospital i! ichildren? 51 !I n.f. 100;100' 100! i 987 96 ; i 921 ! 90! 76 i Group II1 j Iadults ; 1 ! ! Lehnert i 1970 et al ! Viglianij 1968 et al j ' i 8 9 138 m 100!looj ! 87 m.f. lool - ; 98] 86? 69| ji ; 6oj 48 ; 1 > 32 j FRG, garbage \collectors 90 i 80! - t 53` - | 5 ; Italy, Miland Secchi i 1971 et al 10 '122 ; m.f.! 100;100' 99j 74;,60; 385 19 ! 11 . Italy, Miland TEH 0470268 DUP050083086 ;( - 15b - Table 2. Percentile distribution of PbB ( -.g Fb/100 g) levels mainly in women volunteers, 7 City Study USA (Tepper et al 1972)i 98$ levels (or first higher % level) underlined. City curve j n number '50 i <h0 35 . <30 : <25 l <20 ! i in fig.2 ; I , i - 1 j Okeana u Ardmore > Rittenhouse 162 150 136 !1 100 100 100 i 1! 23. ; 93 79 2 j 100 I 100 100 j 95 J 87' 57 i ;3 i 100 j 98 ;j 96 j 89 80 | 41 Pasadena 193 4 1! 100 |1 100 29 j 96 92 65 Los AlamOs (male) 80 5 i ! 100 i j 100 1 99 j 22 94 73 Los Alamos (fern.) 191 Washington D.C. 219 Port Washington 19'8 6 1 100 } 100 100 j 22 99 88 j 100 1 i7 100 100 95 | 89 52 8 !! 100 1 i 100 j 100 100 96 84 1 Greenwich Village i4o Lombard 208 Bridgeport 147 Houston 191 ' 9 f 100 i 100 1i 99 | 29 | 96 j 74 ] ! 68 .10 i loo ; 100 100 ! 100 " 1 22 94 11 < 100 100 97 95 :12 100 ; 100 100 1' 100 100 94 t ii i '`f TEH 0470269 DUP050083087 .4? $ j - individual maximum: *40 ;!,.g Pb/100 ml | - 98percentile : 35 -g Pb/100 ml ! >| - 90percentile ; - 50percentile : 30..3 Pb/lOO ml ; : 20 ;.g Pb/100 ml , This leaves even space for correction of PbB levels based upon the difference in Ht between males and females. Those acceptable percentiles togethershould be regarded as one combined _ level. In this way it is possible to put data of target-groups in a diagram, and see whether the percentiles exceed v. the accepted guide. If the distribution of PbB levels remains be low the guide line, then the environmental exposure is acceptable for the group as such. If individuals { :-,2%) exceed. 35-UOPb/100 ml, then this constitute a signal for action as to the individual micro-environment, If the group as such exceeds the guideline, then this constitutes a signal for action for the macroenvironment of the group. Of course, adequate expertise should determine whether action should be taken, end if so, what action; the proposed guide should not be regarded ss a sharp line dividing areas of yes- and of no- rich. 'I ' In diagram 1 and 2 the data of table' 1 and table 2 are pre / sented, together with the proposed guideline. It is clear that group II. exceeds the guideline at various points. In diagram 3 the proposed guideline and two hypothetical lines A end B are given. Distribution A shows a steep incline, and parti cularly exceeds the guideline at the high PbB levels: this indi cates clearly increased Pb uptake in a certain number of subjects in the target group; there probably Is a point source within the area in which the target group is living. Distribution B shows a generally increased level of uptake, i.e. throughout the whole area as such there exists excessive lead uptake, Reevaluation The proposed biological quality guide should he considered as U.H temporary, and should be reevaluated if new data come available, TEH 0470270 DUP050083088 It. > r-- ;:v ' ^ '.. \ r. ' -I A O' . .r. !' i ;yv' ' ` `*.1 ifi:r \ - 17 >1 However, at this moment the proposed guide could he recommended to governments, being the outcome of present available evidence. In this case, the government should reevaluate the guide after a pe riod of 5 years. Shortterm - long term goal Previously a necessary sequence of operation has been suggested. If in a region the PbB level distribution does not exceed the pro^ posed guideline, steps If to 8not need to be taken. The govern ment can devote man'povreir'and money to other environmental problems. Inorganic lead probably is a non-essential element. although re cently Schwarz (1973) has suggested otherwise. However, because Pb is present everywhere the suggested essential Uptake is easily guaranteed even in non polluted environments. As a long term goal one should try to decrease the lead body burden up to the minimal ''natural" levels; the "costs" of such an approach will exponential ly increase with decreasing FbB-levels, At this moment, the proposed biological quality guide can serve as a short term goal. Whether one wants to go further, is a matter of determijqi,v?riorities within the total effort to achieve and maintain environmental quality. Lead in urine and hair It is a wellknown fact that the concentration of Pb in Urine (FbU) reflects Pb in blood. One could also try to devise a quality guide based upon PbU-levels. However, there are some drawbacks; - influence of diuresis; necessity of correction of concentration levels - contamination of samples - relatively few data on PbU levels in the general population are available A provocation test of PbU with EDTA (Teisinger et al 1966) may give a more adequate estimation of the biologically available internal lead; however, not enough data are available to use this parameter for the purpose discussed. Pb -in hair (FbH) also reflects body burden to a certain extent (Klevay 1973). However - apart from the possibility of external ' contamination - FbH probably does not reflect the rapid exchange TEH 047027! DUP050083089 pool adequately enough. Moreover, not enough data on normal PbHlevels in various population groups are available in relation to Pb. Even if FbU- and PbH-levels could theoretically be used as a biological guide, available data do not allow to make such a proposal at this moment. Reliability of lead levels It is a vellknown fact that the analytical comparability of PbB levels sometimes is poor (Berlin et al 1972). The proposed biological guide is based upon literature data; the levels as such are accepted as reliable, i.e, as presenting the "true" Pb ii blood levels. The guide is predominantiy based upon lead in blood measurements performed in the Erlangen-Group (Lehnert, Haas et al), in Lund (Sweden) and in the Kettering Laboratory (7 City Study), These laboratories have a large experience, and may be regarded as reliable sources of lead, in blood levels. If governments want to adopt the proposed guide, then they should make sure that the validity of the lead in blood analysis is adequate. Otherwise, unjustified conclusions might be drawn from investigation of target groups. Use of parameters of response At this moment determination of lead in blood levels provides a method to estimate the internal biologically available load as indirect measurement of "total environmental exposure to lead. How-, ever, reliance on PbB levels has-some drawbacks: 1. one has to use at least about 5 ml of blood; so venous punc ture is necessary. Mieroanalytical techniques- (finger' prick) are not yet sufficiently developed to provide good compara bility with the standard method; 2., the analytical procedure is rather difficult, and preferably requires expensive laboratory equipment (atomic absorption spectrophotometer). TEH 0470272 DUP050083090 So, it might be feasible to use methods which allow measurement in drops of blood, with rather simple techniques, not using expen sive equipment. ALAB-ievels as parameter According to Hernberg et al (1970, 1972) measurement of aminolaevulinic acid dehydratase (ALAD) in erythrocytes provides a very reliable indirect indicator of PbB-levels (r=-0.90). They called it a "poor man's method". However in other studies r was much lower, particularly in the range PbB 0-50,<<g Pb/100 ml. So, one could examine the possibility to propose a biological quali ty guide based upon ALAD-levels. ALAD activity particularly de creases in the PbB range relevant for public health (0-^0 ,^g Pb/ 100 ml), whereas the concentration of ALA in urine appears to be more suitable for monitoring in Occupational health: diagram 1 (Zielbuis 1972). ALAD-levels can be measured in 0.2-0.3 ml blood. If in children venous puncture might have to be avoided, the method still needs a rather large amount of blood by finger prick: i-6 drops. As stated before, increase of ALAD activity with increasing PbB levels either may be an artifact or a highly sensitive and rather specific parameter of response. Whatever it may be, if we accept PbB = 35/.-g Pb/100 ml as the upper acceptable level, the vellknovn decrease of ALAD levels already in the range of PbB 10-%0 tg Pb/100 m3, cannot be taken as a parameter of meaningfull response. If it might prove to be feasible to propose a bio logical quality guide based upon ALAD-levels, this guide should only be used as a predictor of PbB, and so of total environmental exposure. Notwithstanding vast experience in the last decade, many more or less different techniques have been used to measure ALADaefcivity (Schaller et al 1971), resulting in quite different ab solute amounts (units of measurement) although with very similar procentual average decrease with increasing PbB-levels (zielhuis 1972)-. However, the biological, quality guide does not depend on average levels, but on individual levels. It is not possible in cross-sectional studies to determine the procentual individual TEH 0470273 DUP050083091 - ?0 - decrease in ALAB. It will therefore be necessary to adopt a standard-method. In this paper the author will try to develop a guide for two widely used methods:, if one or both methods will provide a reliable guide, it will be a matter for discussion be tween authorities and research workers to choose one standard method. Within the Common Market discussion<pn this point have already started. The author received two sets of data: 1. Dr B.Haeger-Aronsen, Lund Sweden, provided 138 sets of levels of PbB, ALAD and ALA in urine, each set determined in the same person at the same time, in the range of PbB 18-70 -g Pb/100 ml (venous puncture). The correlation coefficient between PbB and log ALAD = r =-0.83; this coefficient has been calculated on the independent data: only the lowest individual PbB, n=30. These data came from 30 male workers, observed during exposure and during recovery after the end of exposure (factory closed). The different sets of levels thcrefoi-e are not fully indepen dent from each other (diagram . 2. Dr Sv. Hernberg, Helsinki Finland, provided 206 sets of levels of PbB, ALAD and ALA in urine, each set determined at the same time, in the range of 9-70 g Pb/100 ml, the correlation co efficient between PbB and log ALAD r--0.7*4. These data came from a number of occupationally exposed male workers. The different sets of levels therefore kre independent from each other (diagram 6). Both investigators used different methods, and gave different units of measurement: Bonsignore Units (method described in Haeger-Aronsen 1971) and - mol PBG/h/1 erythr. (Hernberg:, method described by Hekkanen et al 1972). Validity of ALAD-levsIs ALAD levels highly correlate with PbB-levels; however, a high coefficient of correlation not necessarily implies a high pre dictive validity. One should calculate (Zielhuis et al 1973) the sensitivity (sc), i.e. the extent to which subjects who truly manifest a characteristic are so classified, and the speci ficity (sp), i.e. the extent to which subjects who do not mani- TEH 0470274 DUP050083092 fest a characteristic are correctly classified; se + sp yields the predictive validity, i.e, the extent to which A situation as observed reflects the "true'* situation. If se + sp ; 1.80, predic tive validity is good (max. 2); 1.50 - 1.30 is to be regarded as moderate; <1,50 as rather poor. If one wants to predict e.g.PbB ; 35Ag Pb/100 ml, one can calculate sensitivity and specificity (and therefore validity) of a certain ALAD-cutoff level, e.g. ALAD (aU (or,:,mol PBG/h/1 ery). A low sensitivity implies many false negative data: ALAD ^corresponds to FbB 35 .-"g Pb/100 ml; indivi duals with high PbB levels are overlooked. A low specificity im plies many false positive data: ALAD < a corresponds to FbB.-{ 35 rg Pb/100 ml; individuals with loir PbB levels are regarded to have high PbB levels. In examining a target population, one does not want to overlook individuals with high PbB levels: a high sen sitivity is necessary; specificity should not be too low either, because one might become too conservative (too many low PbB levels regarded as high); conclusions and actions taken will become un justified. In order to examine the feasibility of a biological quality guide based upon ALAD-levels, we calculated the validity of two cutoff levels for ALAD, based upon a sensitivity = 1,00 and 0.90 (10# false negatives). The results are given in table 3. The vali dity was only calculated for prediction of PbB , 35 and >30.?g Pb/ 100 ml; there were too few levels PbB.<` 20 to make a calculation feasible. If we take sensitivity = 1,00 (i.e, no false negatives)* Validity was rather poor; if we allow 10$* false negative data (i.e. overlooking too high PbB levels in 102 of individuals), validity is still moderate, and never exceeds 1.80. Prom this we may conclude that it is not possible to base a bio logical quality guide On individual ALAD-levels. Similar results would have been gained from other cutoff levels of ALAD, because - notwithstanding a correlation between PbB- and ALAD-levels - the range of ALAD for each PbB-level is very large, the extremes often differing with a factor ; 2. Average levels of ALAD highly discri minate between groups with different average PbB-levels (and with different .exposure); however this does not. apply to individuals, TEH 0470275 DUP050083093 21 a - i' Table 3. Validity of ALAD-cutoff levels as predictors of PbB-levels se - 1.00 and 0,90 V .* PbB ), 35 Fb/100 ml ; PbB - 30 Ag Fb/100 ml 1! data Haeger-Aronsen (in Bons.. U) ALAD < ?0 < : | 45! (in data Hernberg mol PBG/h/1 ery) <750 450 i ! data Haeger-Aronsen; data Hernberg (in Bons. U) )(in mol PBG/h/1 ery) ; 112 <62 I <850 i C560 sensitivity specificity validity 1.00 0,44 1 ,44 t 0.91! 0.76! 1.67. 1.00 D.90 0.55 0.80 1.55 1.70 1.00 2 0.17 1.17 0.90 0.61 1.51 ! 1.00 j 0,48 ! 1.48 0.90 0.82 1.72 TEH 0470276 DUP050083094 - 22 - I Other response parameters The data of Kaeger-Aronsen and of Hernberg also included le vels of i-sminolaevulinic acid in urine (ALAU): in both sets of l data increase of AIATJ starts at PbB ) ^0-50 Pb/l00 ml, and they confirm the schematic presentation of diagram A. ALAU-levels can not be used as a biological quality guide in the sphere of public health. Up to now very few data exist regarding other biochemical para meters; the scanty data available on Protoporphyrin in erythrocy tes do not suggest a high validity in predicting PbB levels in the range of O-^O.e^ Pb/100 ml; the procedure of determination is laborious, individual differences appear to be large (Stuik et al 1973). Indirect effects on health and wellbeing The proposed biological quality guide only protects human beings to direct adverse effects of lead exposure. In proposing environ mental quality standards other effects of lead pollution may have to he taken into account: ecological effects, etc. with a poten tial indirect effect on health and wellbeing. Such indirect effects are not prevented by adherence to the proposed guide. Conclusions and Summary 1, If environmental exposure of the general public to a considera ble extent takes place through various routes of entry, quality standards for one source of exposure (e.g. air, food, water) ." will not protect public health adequately. This 'is the case for inorganic lead. 2, Biologically available lead (lead in blood levels) and para- . meters of subclinieal response may be expected to be feasible for indirect estimation of total environmental exposure; the feasibility has been studied. 3, Lead in blood levels (PbB) in target groups of the general po pulation portray the total environmental exposure to Fb for this TEH 0470277 DUP050083095 group. Such groups should include at least 50 subjects, of same sex, similar socio-cultural class, with narrow age range, And preferably at high risk (exposure or susceptibility). 4. Neither average levels nor one maximum level, but the distri bution of levels in 98% of the target group should be taken as parameter of external exposure, 5. The maximum acceptable individual level for adults is PbB 4o ..'.g Pb/100 ml; because of increased incertainty in regard to pregnancy and developing neonate this level should be lowered to PbB * 35/.g Pb/100 ml. 6. Taking into account the maximum acceptable level of 35 ,,vg Pb/ 100 ml in 98% of subjects, and the normal variability of PbB levels as occurring in practice, the following distribution of PbB levels is proposed as biological quality guide: 98% i 35 >'E Pb/.100 ml 90% ^3/- Pb/100 ml 90% 20 -g Pb/100 ml PbB levels in women should be corrected to male level on the basis of hematocrite. 7. If the general distribution of PbB levels in a target group ex- . ceeds the proposed guide, total exposure in the environment studied is too high; action should be undertaken directed at the total environment. If the distribution only exceeds the guide at high PbB levels, a point source of external lead ex posure is probable; action should be directed at this source, 8. If in the environment total exposure to lead is too high, sub sequent studies should determine contribution through various routes and sources: quality standards for air, food, water may have to be imposed; the same applies to emission standards. . 9* Due attention to errors of measurement of Pb in blood is neces sary, 10. It is not yet possible to propose a biological quality guide based upon Pb in urine or hair. 11. It is not possible to propose a biological quality guide based upon ALAD-aetivity in erythrocytes, neither on ALA-excretion in urine. 12. The proposed biological quality guide for lead in blood could enter governmental regulations, and so become a biological qua- lity standard, if prevention of direct adverse effect on human DUP050083096 TEH 0470278 References % Albahary C. et C.Bcudene, Effete infra cliniques du plonib et leurs correlations avec .1'impregnation de 1'environment. In: Environ mental health aspects of lead, proe. int.Symp., Amsterdam 1972, p.667 Amer. Acad. Pediatrics, Statement on lead "based paint. Congr. re port, 8 dec, 1971, S 13175 Barltrop D., Environmental lead and its pediatric significance. 'k Postgrad, med. J. 45(1969)129 Barltrop D., Sources and significance of environmental lead for . children. In: Environmental health aspects of lead, pros. int. Symp., Amsterdam 1972, p.675 Berlin A., P.del Castilho and J.Smeets, European intercomparison 1'. _ programmes, In: Environmental health aspects of lead, proc. int. k Symp., Amsterdam 1972, p.1033 Blei pnd Umwelt, Komm. fur Umweltgefahren der Bundesgesundheitsamtes, Arheitsgruppe Blei. Berlin, Verein Wasser-Boden-Lufthygiene, 1971 , Bruin, A.de, Certain "biological effects of lead upon the animal or ganism. Arch, environm. Hlth 23(1971)249 Bulpitt C.J., lead and hyperactivity.. Lancet II (1972)1144 ( , Burde, B.de la and S.Choate Metin. Does asymptomatic lead exposure '* / in children have latent sequelae? J.Pediatr. 8l(1972)1088 Committee on biologic effects of atmospheric pollutants. Lead; air borne lead in perspective, Washington, Rational Academy Sciences, 1972 Cooke R.E., The biological basis of pediatric practice. Hew York, McGraw-Hill, 1965, p.414 David 0., I,Clark and K.Voeller, Lead and hyperactivity. Lancet II (1972)900 Editorial, Subclinical lead poisoning. 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Lek, 24(1972)77 Hernberg S. , Communication meeting of experts, Luxemburg, CEC, 1973 Klevay L.H., Hair as a biopsy material. Arch, environm. Hlth 26 (1973)169 Lehnert G. , Der Blutbleispiegel und seine Bedeutung fiir die Pathogenese und Prevention der beruflich bedingte Bleivergiftung. Stuttgart, Gentner, 1968a Lehnert G., G.Stadelmann, K.H.Schaller und D.Szadkovski, Usuelle Bleibelastung durch Nahrungsmittel und Getranke. Arch, Hyg. Bakt. 5(1969)403 Lehnert G., H.Mastall, D.Szadkovski und K.H.Schaller, Berufliche Bleibelastung durch Autoabgase in Groszstadtstrassan, Dtsch. med.Wschr. 95(1970)1097 Millar J.A., V.Battistine, R.L.C.Cumming, F.Carswell and A,Gold berg, Lead and ALAD levels in mentally retarded children and in lead poisoned suckling rats. Lancet IX (1970) 695 Moncrieff A.A., O.P'.Koumides. B.E.Clayton, A.D.Patrick, A.G.C, Renvick.and G.E.Roberts, Lead poisoning in children. Arch, Dis. Childh. 39(1964)1 TEH 0470280 DUP050083098 V . if :.- '. 4 ' * , : ir. : y/"' / # ,, * fe' .% : p * :r r-?' ; i. ' `l|>. - 26 - Nikkanen J., S.Hernberp and S.Tola, Modification of the ; -ALAD teat and their significance for assessing different intensities of lead-expo sure , Work-environment-health 9(1972)46 Nordman C.H., S.Herhberg, J.fiikkanen and A.Rijkanen, Blood lead levels and erythrocyte . ALAD activity in people living around a secondary lead smelter. Work-environment-health 10(1973)19 Pietrowsky J.K., Kinetic behaviour of lead. Congr. chem. pollution and human ecology, Prague 1970 Schaller K.H., K.Mache, T.Haas, W.Uaehe und H.Valentin, Methoden zum Bestimmung der -ALA-dehydratase-Aktivitat. Europ, Gemeinschaft Dok 3107/71 d, 1971 Schwanitz G. G.Lehnert und E.Gebhart, Chromosomen schaden bei beruflicher Bleibelastung, Dtsch.Med.Wschr, 95(1970)1635 Schwarz K., Scientist disputes lead health danger claims for auto's. Oil daily 25 april 1973, p. 1 Seechi G.C,, L.Alessio e G.Cambiaghi, Richerche sull'attivita ABAC eritrocitavia di soggesti non esposti a contatto profes sional con piomho. Med.Luvoro 62(1971)435 Seppalainen A.M. and G.Hernberg, Sensitive technique for detec ting subclinieal lead .neuropathy. Brit.J.industr. Med. 29 (1972)443 Stave U., Physiology of the perinatal`period, vol. 1, p.2,10. Hew York, Appleton, 1970 Stuik E.J., A.de Bruin and R.L.Zielhuis, Human volunteer study, lot yet published, Coronel Laboratory, Univ. of Amsterdam, 1973 Teisinger J., I.Prerpvska und V.Sedivec, Versuch urn die Bestimmung von Blei Depot ira Korper bei experimenteller Bleivergiftung. 15th Int, Congr. occup. Hlth Vienna 1966, Vol.Ill, p.79 Tepper L.B. and L.S,Levin, A survey of air and population lead levels in selected American Communities. Univ. Cincinnati, Dept, enVironm, Hlth, 1972 Thompson J.A., Balance between intake and output of lead in normal individuals. Brit.J.industr,Med. 26(1971)18? , TEH 0470281 DUP050083099 - 27 Vigliani B.C. and M.Zurlo, Lead in blood Sind lead in urine values of adults not exposed to lead, living in Milan. Report Work C'onf. inorg. lead, Amsterdam 1968 Zielhuis R.L., Lead absorption and public health: an appraisal of hazards. Environmental health aspects of lead. Comm. Europ. Comm. 1972a, p.649 Zielhuis R.L., Industrial'toxicology and public health. Arch, environm. Kith 24(1972b)112 Zielhuis R.L., Health and environmental quality standards. Proc, 3rd Int. Clean Air Congress, Diisseldorf 1973 Zielhuis R.L. and M.M.Verberk, Validity of biological tests in epidemiological toxicology. Int. Arch.occup.Hlth in the press 1973 TEH 0470282 DUP050083100 &` c , >* . *V ; VS' .' : - * 8 o o ,-*. .* O) % UJ 2: > > < LU X *> < CD . \ > .) CL '.i ' is:- 2: fa/ 0 f. v: /* , i ' b-.. h~ zd 03 a: |>i tO -/ ' * O , /? : ..1 " : V;' "r:./ . '..t .V: ` V > . & i . V.* b?v .V *T1 * /' /> +\ "f 3 LU U tr LLI a. 2 < ec CD < O 1LE O F l/> < X ( LU H> LU O -J CO CO < H- UJ |Q .1 ZD O Q LU </) O CL O oc a. UJ X l-- *% . ^ " V :; v CD x> IX Ol 3* DUP050083101 DIAGRAM 2 : PERCENTILE DISTRIBUTION OF PbB (p _ TABLE 2 _ THE PROPOSED GUIDE IS GIVEN AS A CD JZl D- D) 5U DUP050083102 V : y.V i`-V M:'.. x:*?< is yrr::,' ,v- : ...f.v. .p II .*:! H-vi C.V'tf ; 'V Q CD Z < % ~.rVo* rd I< O o --, in z cn of-- 2k f-- D 00 CD jD Ou r H- cc </) oQ u- --f LU Q < U mr o LU Q LU t/) HO 0l >* OX CL Oo q: a. CO 2 < or o < o I I JL _L_ JL oo oo jCN. e CO m <r o o 2 \ CL di TEH 0470265 1.. 1. ., -.1. oo CO CM AY O DUP050083103 D iagram 4. Percentual change in A LA D en ALAU in relationship to PfaB 80 ,PbB in jjg Pb/1 DUP050083104 I r , .(< ? V f'* , ; _V.. V *' '' y/. y! k'r / % \ . & ?.>v & > * > i*. > i,v : V r.i o o CD a. s DUP050083105 TEH 0470289 > A LA D ai t- 4) XI C OO ,-u. O CM X II C 0 Q o4 o . wIk X9h. *O4? t\i i r>9i r~<9t ( 4< tt > v2 ari 1 H o O CQ ca X'i a. :X t 9 e % e a * 3* "a A 1 o<* 9 00 0 %J e 8 8 * H $*I** <B e9A% 0 *** L ? 6 w9 9 * *> 1 *K " ^ ^ * ' <1 ! * 0 !> * I ft II I t oo ooo r*> to to <r CO a i____L o CM o o to o o CM O O CO o o sr DUP050083106