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Lead: the debate goes on, but not over science Research on the extent oflead contamination of the modern environment and on the health effects oflow levels oflead has done much to remove scientific uncertainty and to shift debatefrom the scientific to the political realm It is two millenia since the first de scription of lead poisoning appeared, two centuries since Benjamin Franklin wrote on the effects of lead, halF a century since lead paint was tracked down as the cause of lead poisoning in children, "Why," asks Herbert L, Needleman of the Harvard Medical School, "does the problem of lead continue to be debated? And why is the orderly process of decreasing lead in the human environment slowed in the face of what many consider an overwhelming body of facts docu menting its toxicity at low dose?" 'The answer, says Needleman, is no longer scientific uncertainty, but eco nomics and politics. On one side are six government agencies charged with regulating and studying lead. They face an enormous task. Lead appears in food from the solder used on cans; in water from the lead pipes used in older plumbing; and in air from lead addi tives used in gasoline, from the dust of dd lead paint and putty, and from the initial smelting of lead ore that makes lead available for ail its uses. Several of those agencies are playing a game of musical chairs, each trying to pass the responsibility to another by showing that the source of lead exposure it regulates is insignificant compared to the others (Chemical and Engineering News, June 23, 1980, p. 23). On the other side is an industry that is fighting for its very existence, and will fight all the harder as more take up the cry of Clair C. Patterson, a geochemist at the California Institute of Technology: "ft is intrinsically wrong to mine and smelt millions of tons of a highly toxic, poi sonous substance such as lead each year and disperse it within human en vironments." Two controversies Research that in the last few years has done much to settle two long standing scientific controversies con cerning lead in the environment has in particular made it clear that the con tinuing debate hinges on politics, not science. The first, over the extent of Contamination of the contemporary environment, has been all but put to rest by Patterson's work; he has shown contamination of the oceans of the Northern Hemisphere 10-fold over prehistoric levels; the atmosphere, 50-fold; the Greenland ice cap, 300fold; and most Americans' bodies, 600-fold. Most significantly, he has demonstrated that conflicting results obtained by others were the result of contamination of samples and labo ratory equipment, leading to analytic errors of as much as three orders of magnitude in the numbers they ob tained for prehistoric levels. The other controversy--the effects of low levels of lead--while not put to rest, is at least not thrashing about in the quagmire of a few years ago. This is largely the consequence of a care fully controlled epidemiological study by Needleman that showed poorer performance and more behavioral problems among children with ele vated, but subacute, levels of lead in their bodies. Natural or industrial? Patterson's work is the climax of a story that began in 1924, a story of analytical chemistry with a touch of imaginative detective work. In 1924, j. C- Aub et al. published a paper in the Journal ofthe American Medical Association which reported that lead did not occur naturally in humans; only workers improperly exposed to industrial lead were Contaminated. Improved analytical techniques al lowed R. A. Kehoe to refute this claim a decade later; he showed that lead occurred at low levels even in the blood 0013-936X/31/0915-0243$01.25/0 1981 American Chemical Society Volume 15, Number 3, March 198 1 243 0531879 X and excreta of typical adults. His facts Were correct but his con clusion was not. He believed that the levels be detected in typical adults were natural, not the result of industrial activity. This view survived intact for three decades. Even by the mid-1960s, the prevailing medical opinion was that no more than one-half of the lead in humans was of industrial origin. It was Patterson's early work on lead contamination of the environment that unleashed the controversy. "Pat terson claimed that humans were contaminated with industrial lead by a factor of 100," explains Robert W, Elias of Virginia Polytech. "This esti mate was based on his estimate oflead contamination in the environment. It has taken almost 20 years to verify Patterson's numbers, and he was right." Patterson was right because he takes elaborate precautions to prevent con tamination of his samples and his lab oratory by the elevated levels of lead that are omnipresent in the modern environment. The interior of his lab is lined with plastic; an air-lock and pressurized ultra-clean air prevent outside contaminated air from enter ing; and his reagents are cleaned of lead contamination within the lab. His precautions--and his use of the most sensitive analytic technique for lead, isotope dilution mass spectros copy--have given him the edge needed to detect the true, minute quantities of lead occurring in samples that reflect the prehistoric environment. And he has shown time and time again that conflicting results obtained by other workers are the result of sample con tamination and inadequate analytic techniques. The most recent instance was data that questioned Patterson's analysis of deep, ancient arctic ice. Patterson's group had found that 3000-year-old ice contained only 2 ng lead/kg, com pared with 200 ng/kg a t present. Three other groups subsequently reported finding prehistoric levels to be much higher, in fact nearly the same as present levels--findings that suggested Kehoe was right, that current typical levels of contamination are natural and not the result of industrial activity. But in a paper to be submitted to Geochimica et Cosmochimica Acta, Patterson and a graduate student, Amy Ng, report that their analyses of the ice cores used by the other groups revealed considerable contamination of the cores during drilling and han dling. Lead concentrations at the center ofthe cores turned out to be less than a tenth of the values reported. Concentrations on the outside of the cores were six orders of magnitude over the true uncontaminated values. Patterson's group has dug out other Obscure records of the ancient envi ronment--pond sediments, deep pcean water, bones of prehistoric Peruvi ans--and all have confirmed his basic contention; Industrial lead is ubiqui tous in the modern environment at concentrations orders of magnitude above natural levels. The Peruvian bone data has a spe cial significance because it provides a direct measure of the natural level in humans, some two to three orders of magnitude below present typical levels. The data also lend concrete support to the "biopurification" theory that Elias has used to estimate natural levels in humans and other organisms. Elias explains that nonpollutant trace metals such as barium and strontium are increasingly purified with respect to calcium as they move up the food chain. Calcium is essential to the workings of all living things, and they therefore actively concentrate calcium at the expense of the other trace metals. By analogy, the ratio of lead to calcium should drop as well in going from plants to herbivores to carnivores. Elias's predicted value for natural lead in humans so obtained is within a factor of two of the value found in the Peruvian bones. Politics and pride In the face of this overwhelming body of evidence, resistance to Pat terson's findings can be attributed largely to politics and professional pride--no one likes to be told that his analytic technique is off by a factor of 1000, and Patterson hasn't balked at stepping on toes, Patterson, who was reached in American Samoa where he is doing field work, believes it is a matter of time for his results and methods to sink in: "knowledgeable and competent scientists who understand the signifi cance and who are aware of the quality and integrity of the work of my col leagues and myself are in uniform agreement. A large number of applied chemists have made an enormous number of measurements of environ mental occurrences of lead that are in error by many orders of magnitude. This is a fact which is not controver sial. The problem is the length of time it will take for applied chemists to recognize this fact. "Here at the U.S. NOAA Air Re sources Laboratory in Pago Pago, American Samoa, I and my colleagues are determining the input fiux of lead to the South Pacific. One of the pa rameters we measure is the concen tration of lead in the easterly trade winds. It is difficult to properly collect filtered samples of such air that are scientifically significant because of interference by local sources of in dustrial lead contamination. So elab orate precautions must be taken to properly locate theair collector, whiph can be operated only a fraction of the time, under suitable meteorological conditions. During the past week, we operated our air filters only for five hours. "During this same period, an air filter device placed nearby, but at a scientifically meaningless and totally unacceptable location, droned on and on 24 hours a day for days on end, collecting local lead pollution on filters that had been packaged and handled in the most crude and unacceptable fashion. In past years, these filters were sent to the U.S. National Health and Safety Laboratory of the Department of Energy. And their mindless, mean ingless analytic results which have been published as reports oflead in air at remote locations typify the quality and significance of most of the large amount of environmental lead data now being collected and which will continue to be collected and published for some time to come," Patterson's case does not end with his showing the analytic errors ofoth ers. He believes that the extent the modern environment is contaminated with lead is proof itself that we must stop the further mining and smelting of lead. And his argument takes a striking form when he points out that we have already increased our dietary intake of lead 100 times over natural levels--and that a further increase of a factor of only five brings us into the level of acute toxic effects. The "en gineering approach," which demands subacute effects to be demonstrated before they are believed, ignores the extent of contamination, he says. No other metal may be increased in the diet by a factor of 100 without delete rious effect. But not everyone buys this conclu sion. The Food and Drug Adminis tration, which has responsibility over canned foods, continues to use the typical levels of lead in canned foods as the reference point. When Patterson, in a paper published in Science last year, showed that tuna packed in lead-soldered cans is contaminated 4000-fold over fresh raw tuna--and that, once again, analyses of fresh tuna by others (including the FDA) came up with values 1000 times too high-- FDA called it a "meaningless aca demic exercise." "For the quantities of lead that are 244 Environmental Science & Technology TEH 0531880 DUP050032376 found in these food samples, you don't need the kind of laboratory setup that Dr. Patterson has," says Kathryn R Mahaffey, assistant to the di rector of FDA's division of nutrition. Patterson calls this circular bu reaucratic reasoning. "We have proved that they made 1000-fold errors in the determination of lead in raw tuna. Their response to this disclosure of their flagrant ineptitude is that the FDA is required only to correctly de termine when lead concentrations in crease above typical levels of about a half a part per million in canned tuna fish." Patterson insists that the refer ence point is not that half a ppm, but the natural levels, 1000 times less. Subtle effects But even while Mahaffey argues that "the assertion that the level of lead in the food supply causes health effects is not proved" and takes Patterson, a geochemist, to task for venturing into biology ("One thing that's important for scientists to recognize is that there are limits to their expertise"), she is convinced that progressively more subtle health effects of low-level ex posures to lead will be indentified. This is the second issue, really the other side of the coin of the environmental con tamination issue, and one which has also seen considerable progress in the last few years. Spearheading that progress is an epidemiologic study by Needleman of some 2000 school children in the Bos ton area. His principal finding: "Lead in children at levels below that which bring them to a doctor are dangerous to their brains." Children are particularly sensitive to lead. They absorb 30-50% of in gested lead, as opposed to the 5-10% that adults absorb. Theacute effects of lead poisoning--constipation, vomit ing, anemia, swelling of the brain, palsies, and eventually death--are well documented. Needleman set out to document more subtle effects that he believed showed up at subacute expo sure levels--behavioral problems, poor intellectual performance, short atten tion span. But epidemiology is an inexact science. Even studies that look for acute effects, such as lung cancer, are plagued with uncertainty. It is not unusual to find as many different re sults as there are epidemiological studies on a given subject. The subtle effects that Needleman was looking for make the problem all the harder. He set out to design a study that would answer the objections leveled at previous studies of the subtle effects of lead, studies that are a morass of in- Increasing lead production... 5000 4000 3000 2000 Years before present 1000 Man began releasing lead to the environment with the discovery of cupellation, the process of separating silver from base metals including lead. Note that the vertical scale Is logarithmic. Sourca: National Academy of Sciences, "Lead In the Human Environment" ... and environmental accumulation f/.g lead/kg snow 0.20 0.15 0.10 0.05 0 8Q0B.C. 1750A.P. 1800 1850 Age of samples 1900 1950 Samples of snow from the Greenland ice cap show the increasing contamina tion of the environment with tead. Source: C- Patterson. California Institute of Technology ' Volume 15, Number 3, March 19S1 245 DUP050032377 TEH 0531881 conclusiveness. He identified four tention to one of these studies, carried specific problems: out among children who had lived near Poor markers of past exposure. a lead smelter in El Paso. Cole quoted The almost universally used marker of from the findings of a committee set up exposure, blood lead concentration, by the Society of Occupational and reflects current exposure only. Environmental Health to evaluate that Ascertainment bias. Subjects who work: "In summary, the committee agree to participate in a study may concluded, reports and data made differ markedly from those who -available in these studies of El Paso refuse. have not clearly demonstrated psy Weak measures ofoutcome. Tests chological or neurological effects in the of behavior and performance are often children under study." limited or insensitive. Yet Cole admits in passing that the Confounding Variables. Factors committee also found that the studies other than lead exposure may affect were not powerful enough to demon the outcome. strate the absence of health impair Needleman used lead concentra ments--which is the very essence of tions in lost primary teeth--lead ac why negative results from insensitive cumulates in teeth as in bone--as the studies are of little value. And that is marker of lifetime exposure, and he Needleman's key message: A negative collected teeth from 70% of the chil result does not simply cancel out a dren studied. A variety of double-blind positive result, "The point at which performance tests (IQ. reaction time, brain effects show up will depend on sentence repetition) were used along the sensitivity of the study and the with teachers' ratings of the children's rigor of the epidemiology," he main classroom behavior ("distractable," tains. "impulsive," "does noi follow in But Cole argues that since "there is structions") to measure the outcome. an impossibility of proving the absence And after separating children into ofan effect--you can never, ever prove high-lead and low-lead groups, Nee the negative"; the scale is unfairly dleman looked at some 30 nonlead tipped towards positive findings. He variables (medical histories, race, sex, points to an EPA evaluation of 22 parents' income, parents' attitudes studies of health effects of lead; only towards school, mother's number of five of these were considered to be any pregnancies) and controlled for five good, and of these only two--including that he found to differ significantly Needlcman's--showed any effects. between the two groups, And from this he concludes that "if "High-lead children were found to there is an effect, it isn't all that se be significantly less ableon a number vere." of performance measures," Needle- Punctuating this conflict in basic man says. "High-lead subjects were approaches is continuous sniping over also significantly more likely to be re details of the scientific methods and ported as disordered in their classroom conclusions of the various studies. behavior." The high-lead group had a Cole, for example, argues that the four-point lower mean IQ than the four-point difference in IQ that Nee low-lead group. And when Needleman dleman found is quite small; Needle separated the children into six groups man responds that "a lot of people who according to lead levels, he found a make that point should really know continuous dose-response relationship better" since a four-point difference in on each of the items of the teachers' the mean can translate to a large dif ratings. There appeared to be no ference in the wings of the distribution. threshold. There may be many more children in Insensitive or negative? the high-lead group who are, say, below 75 in IQ. Cole counters that we The resistance to Needleman's don't know what the actual distribu findings may once again be more a tion is. matter of politics than science. The Needleman says that the El Paso lead industry continues to cart around study has "serious problems"; for ex results of studies that Needleman and ample, "a lot of those people did not others call poorly controlled and in participate--there was litigation sensitive; these show no correlation against the industry, and it is possible between lead exposure and perfor that the families of the kids most in mance of children. At the recent an jured, who were bringing suit, would nual meeting of the American Asso not participate in an industry-spon ciation for the Advancement of sored study." Cole claims that the ex Science, Jerome F. Cole of the Inter cluded group did not differ in blood national Lead Zinc Research Orga lead levels, Needleman argues that nization (ILZRO), an industry-sup blood lead is an inadequate marker of ported group, gave considerable at- past exposure. And so on. Both ILZRO and Needleman are now working on prospective studies of lead's effect on children; the results of these studies may lake away some of the ammunition of future sniping. Needleman plans to examine children from pregnancy on, measuring their total exposure to lead from air, food, water, and paint. Unanswered questions That work may also help to answer one of the genuine scientific questions that remains: What are the relative contributions of different sources of lead to typical human exposures. Getting the answer to that question could do much to halt the runaround among the regulatory agencies. (A recent report issued by the General Accounting Office confirms that the runaround continues. GAO found that the Department of Housing and Urban Development, which is charged with eliminating lead paint from federally assisted housing and which maintains that lead from sources other than paint is more important, is "not fully complying with its own regulations and procedures directed at eliminating the hazards of lead-based paint." Mean while, EPA continues to move slowly and cautiously on enforcing its ambi ent air standard for lead, even after it was recently upheld by the Supreme Court.) Patterson is quick to insist that re search on the relative contributions of different sources should not be relevant. to regulatory strategies, however. He is convinced that the scientific evidence already in hand makes the case for eliminating exposures from all sources--and for halting mining of lead altogether. The political reality, though, is that technical fixes will be the short-term answer to lead pollu tion, and that until the buck-passing among the agencies stops, even these fixes will not be enforced. Patterson points to a second unre solved scientific issue, one that is a sobering reminder and a capsule summary of the extent of lead con tamination of the modern environ ment. "It is highly probable that many biochemical processes within the cells of humans and animals, universally subjected to lead pollution on a wide spread scale, are highly perturbed and unnatural. It is a matter of great sci entific interest to discover bow natural biochemical processes operate under lead-free conditions. This means that such studies should be carried out in the future in lead-free sanctuaries." In our lead-contaminated world, Patter son is saying, there are no unperturbed controls. --Stephen Budiansky 24$ Environmental Science & Technology TEH 0531882 DUP050032378