Stuttering and Lead Poisoning: stories from the last century

Plagues and epidemics are remembered for the suffering they caused. Victims often had fever, sores, and rashes and perhaps they died. But there was an epidemic in the United States and elsewhere that had none of these, and only by retracing events did experts learn that a scourge had even taken place. Had they not done so, had they failed to find a cause for the effect, the events that came to define chronic lead poisoning [Note 1] in the Twentieth Century would have passed into history unnoticed, disappearing without a trace. For victims of this epidemic could not be recognized walking down a street, laying in a sick room, lounging in a hospital corridor, or sitting in a doctor’s office. They were never held under quarantine, and despite the fact that lead contamination can at times be passed from one person to the next, their contacts were seldom hunted down. Rather as a group, and stubbornly years to decades after they were poisoned, they could be found where such groups had never been seen before; arraigned in court on criminal charges, sitting in a dentist’s chair with a mouth full of cavities, falling behind in academic studies, made objects of ridicule for a stuttering speech defect, failing to achieve the American Dream. For once poisoned, the Dream was reached only by a lucky few despite opportunities afforded to, and hard work and desire from, the many who failed. It is a measure of how little we understood disorders of human behavior that more than 60 years into the Century had passed before the Nation [USA] began to awake to the epidemic's terrible toll.

Since Antiquity cases of lead poisoning have occurred sporadically but never in the numbers seen during the first half of the Twentieth Century, when industry used lead in enormous quantity. As the Century dawned, one of its first poisoning victims was surely a young boy born in 1895 in Norfolk, England. Raised in a well-to-do family his father was an avid hunter of game birds and introduced his sons to the sport. It is reported that the father killed as many as 1,000 birds in a single day with a shotgun and participated in hunts that killed as many as 30,000 in a year. (Rose 1983, Gore 1949) This he did year in and year out until in old age he could no longer shoulder a gun. Such activity, reported by more than one biographer and occurring at a time when there was little appreciation of the dangers of lead, would have required huge quantities of lead shot. In turn lead would have contaminated game meat posing a danger to all who consumed it. Together with the repeated cleaning of guns and other contaminated equipment, the father’s obsession would have set the stage for the random dispersal of lead, as dust, residue, and fragments, over a wide area impacting both people and place. It does not take much imagination to appreciate the dangers a young child would have faced when placed in such an environment. Readers of biographical texts (Bennett 1958) will find terms describing the son’s health as a young child and teenager, terms such as “...stammering...chronic stomach trouble....gastric complaint...weight loss...” (Bennett 1958, pps.17&84); “...high strung, easily excitable, and nervous…” (p.27); “…acute depression, outbreaks of anger…” (p.27), as well as learning difficulties experienced as a student (p.32). These conditions individually can have more than one cause but together they make a practically unassailable case for lead poisoning, particularly in view of the father’s hunting obsession and its connection to lead. Thus did Albert George Windsor, the son, fall victim to a hazard of the industrial age. And on May 12, 1937 following the abdication of his brother, he became King George VI of England, the subject of the film biopic “The King’s Speech”. 

Stuttering, a common problem in the Twentieth Century until its final quarter, defied efforts to discover the cause although many theories were advanced. Speech clinics sprang up to conduct research and treat affected individuals. One such clinic was established at the University of Iowa at Iowa City and in time that clinic came to be headed by Dr. Wendell Johnson, a speech pathologist. Beginning in the early 1930s Dr. Johnson became involved with a series of case-control studies comparing children who stuttered with those who did not. Most of the children enrolled in Johnson's second study (Study II) and many of the children enrolled in his third study (Study III) were members of a cohort born in the late '30s and early '40s. They and other members of the cohort were enumerated in the Biennial Survey of Education in the United States, 1952-'54. (Office of Education 1959a)

The Survey was compiled from data gathered from questionnaires sent to 4,966 school districts across the United States. Returns were said to be 99.44% complete. (Office of Education 1959a, p.5) [i] Children who stuttered were included in the subgroup labeled "Impaired Speech" in the category "Exceptional Children". That category identified children with handicaps (blind, crippled, speech impediments, deaf, etc.) severe enough to warrant the attention of school officials who then worked to accommodate their special education needs. "Special education services for speech-defective children ", wrote the authors of the Survey, "expanded at nearly 4 times the rate of enrollment growth in public schools" [Note 2] (Office of Education 1959a, p.2) [Note 3 (Office of Education 1959b, p.6)],… "[an enrollment increase] that might best be described as phenomenal" (Office of Education 1959a, p.14). Since exceptional children were not enumerated in every biennial survey, results from the 1952-'54 Survey could not be compared to those from the 1950-'52 Survey, but could be compared to the 1946-'48 Survey. When that comparison is made special education services for speech-defective children grew 68% overall, and 480% in the number of students with speech defects enrolled in special education in the secondary grades. (Office of Education 1959a, pps.8&14) The 1952-'54 Survey identified children as being either in "elementary" or secondary" grades, although "it is likely", wrote the authors, "that the majority of secondary school children in this study are in junior rather than senior high schools" (p.6). Children in those grades had been born near the start of a decade that would, due to the crush of war, see heavy, chaotic, and often dangerous use of lead, made worse by ignorance, in industries of all types. Children whose parents worked in these industries were placed at risk from lead dust and residue brought home on clothing and person. Reflecting on the ongoing sorry state of industrial hygiene in the lead trades at the end of the 1940s Dr. Robert Kehoe, the most influential occupational physician of his day, observed that the demands of World War II had led to "a large and abrupt increase in the number and volume of lead-bearing materials and commodities. Under such circumstances production schedules [likely took] precedence over precautionary measures,...lead exposure may well have increased by an increment that...[was] disproportionate to increases in production...[there was an] increased frequency of failures of plant equipment under the stress of production schedules...[there were] mistakes and failures of inadequately trained personnel...inadequacies in supervision...deficiencies in plant housekeeping". (Patty 1949, pps.644-645)

The demographic bulge that began in the late '30s and early '40s and grew to almost half a million children with speech defects requiring special education, appeared to slow if not peak by 1958. (Office of Education 1959c, p.3) [Note 4] The 1956-'58 Survey showed a reversal in enrollment rates (in the neighborhood of -20% to -40% when compared to the +480% gain seen in the 1952-'54 Survey) for children in the secondary grades. (Office of Education 1959c, p.12) Enrollment in special education of speech-defective children in the elementary grades continued to show high double digit growth however. (p.11) Enrollment figures in the 1952-'54 Survey were also broken out by state. These figures can be compared by dividing the number of children with speech problems (as reported) by the total number of children in the same age bracket, by state. Since most of those in the secondary grades were said to be in junior high school, children in elementary through secondary grades would have been in the 5 to 14 years age bracket roughly. The total number of children in New York State, for example, in this age bracket in 1950 was 1,987,210. (1950 US Census) Using this figure as the denominator and 84,483 (the number of special education speech-impaired children in both elementary and secondary grades in New York) as the numerator, a rate is established. After ranking, the ten states with the largest percentage of speech-defective children determined in this manner were, in descending order, New York, Rhode Island, California, Illinois, Michigan, Missouri, Wisconsin, Indiana, Pennsylvania, and Florida. With the exception of Florida all had supported the war effort with heavy industry: communication cable manufacturing, national defense plants, mining of metal ores, smelting, shipbuilding and repair, munitions, foundries, and mills. All of this activity continued after the war to a greater or lesser extent, and all of it involved some combination of the mining, milling, smelting, handling and shipping of lead. Florida's place in the ranking may have stemmed from its limited ship-building industry, a very large military presence in the State during the War with the accompanying use and repair of munitions, and its demographics, namely a greater level of lead use and exposure among Central American/Caribbean immigrants as was suggested by a recent survey. (CDC 2013) At the opposite end of the ranking were 10 states that had the lowest rates of speech-impaired children. [Note 5] These states had mainly contributed to the war effort in ways that did not involve heavy industry or the mining of metal ores. They were: South Carolina, South Dakota, West Virginia, Maine [Note 6 (Wikipedia 2016a)], Arkansas, New Mexico, Montana, Mississippi, Alabama, [Note 7 (Wikipedia 2016b)] and Vermont.

The conclusion that lead exposure can lead to speech impediments in children is reinforced when the distribution of colleges and universities offering undergraduate or post-graduate degrees in speech correction in the 1950s (Mackie and Dunn 1954) is examined and compared to the population each program nominally served (its constituency). If it were assumed (correctly or not) that the frequency of speech disorders requiring correction was roughly equal across constituencies, then the size of a program would have been dictated solely by the size of its constituency, that is, the number of children under the age of 15 living within a pre-defined distance from the institution. [Note 8] Although a few adults and older children may have been clinic patients as well, most would have been younger. And while an occasional patient and/or family may have been willing to travel outside a service area to reach a distant clinic on a recurring basis, this would have been beyond the means of most. Most would have expected to travel to clinic, be evaluated, receive therapy, and return home in a single day.

Speech clinics were needed to train students and offer assistance to patients. The greater the demand for clinical services the larger and more numerous the clinics. More clinics meant more training opportunities for more students who in return helped staff the clinics. Clinics needed students (to help manage the flow of patients) as much as students needed clinics (to acquire competency in their profession). And just as the number and size of clinics was an indicator of demand for services, the number of students in a program was likewise an indicator. One method of comparing demand across programs is to construct a ratio for each with the number of students in the program (graduate and undergraduate) as the numerator and the number of constituents the denominator. The resulting fraction, reduced to a decimal and read as students per constituent, adjusts for differences in the size of constituencies and can serve as a basis for comparison. The assumption is that the larger the value of the decimal fraction the greater the demand relative to the size of the constituency.

Despite the fact that Northwestern University in Chicago operated the largest program by far offering degrees in speech correction during the 1950s, [Note 9 (Mackie and Dunn 1954) (1950 U.S. Census)] that was not the program that satisfied the largest demand for clinical services relative to the size of the constituency. That honor went to three other programs, the Municipal University of Wichita (now Wichita State University) [Note 10 (Mackie and Dunn 1954) (1950 U.S. Census)] in Wichita Kansas, which headed the list by a good bit, the University of Wisconsin, and the University of Utah. It is particularly instructive to look at Wichita.

Wichita Kansas lies downwind from the northwest corner of the Tri-State Mining District, which includes portions of Missouri and the southeastern corner of Kansas, and from the site of the now closed zinc smelter in Blackwell, Oklahoma, just 60 miles south of Wichita. Blackwell was at one time the largest zinc smelter in the U.S. (irock@4grc.com 2009, Wikipedia 2016c)  Tri-State was the great lead and zinc mining and smelting area of the United States. Lead is still being mined in Missouri. Beginning in about 1870 zinc smelters began populating southeastern Kansas, in an area the center of which today is about a 3-hour drive from Wichita. Lead and zinc are often mined together and the resulting zinc ore contains lead as an impurity. Thus lead is always found in the waste slag produced by zinc smelters and lead impurities spewed from their smoke stacks when the smelters were active. All of the smelters, 15 at last count all in or very close to the southeast corner of Kansas, have long been abandoned, some for more than 100 years. While some of the slag piles have recently been cleaned-up, others are eroding to dust allowing heavy metals to become airborne and enter the water. (Junge and Bean 2006) Prior to reclamation efforts the piles collectively were many acres in size and scattered over hundreds of square miles, abetted by the repurposing of slag material for road construction in some areas. (Kansas Geological Survey 2005)

These stories are among the many thousands from the front lines of the lead poisoning epidemic of the last century. Most will never be told because poisoning was never suspected. But thanks to the power of the Internet with help from America's libraries and archives, one story, inspired by published research that sat neglected on a library shelf for more than 50 years, is having its day in the sun. If that story, now a blend of fact and conjecture, should someday be proven true, it would offer a sad footnote to our nation's history, one that has never come to light until now. Here is the conclusion to that story that began in the 1930s with Dr. Wendell Johnson at the University of Iowa.

After completing their studies in the mid-1950s Johnson and his associates published their findings in a book, The Onset of Stuttering: Research Findings and Implications (Johnson 1959) in March 1959. Each of the over eight hundred multiple-choice questions used to query parents of the approximately 400 children who participated in the studies, together with the answers they gave (collectively known as the "data"), were included in the book as a 240-page appendix, almost half the book.

As a rule researchers maintain tight control over their data so that they are able to defend them on their own terms. On the face of it, Johnson's situation was no different. He and his associates knew the data's nuances and the thinking that lay behind the wording of each question. They had worked to validate the research model, raise the money, train the work force, meet the deadlines, identify and recruit study subjects, choose the statistical models, and consult with others engaged in the same field of study. The process of generating the hypothesis, designing the questionnaires, validating them, field testing them, administering them, recording the answers, coding them, entering the codes on IBM punch cards, checking the cards for accuracy, and generally trouble-shooting the many problems that normally arise in this type of endeavor, collectively took hundreds of hours and thousands of 1950s' dollars to accomplish. To include, at considerable expense, a data appendix of this length and detail in a scientific publication and then to issue an invitation [Note 11 (Johnson 1959)] to anyone who happened to walk by to analyze and interpret the data in any manner they saw fit, is unheard-of in both instances and more to the point is not done…unless there is a compelling reason.

Ultimately why they chose to publish in this manner is unknowable prompting speculation. To begin, given the effort and expense involved not to mention loss of control over the data, it is unlikely that they released it to the public out of kindness, on a whim, or to satisfy their own curiosity. It is more likely that they saw in the data something that troubled them, enough to make the extraordinary effort they did to bring it to the public's attention. And what they may have seen was a link between stuttering and lead poisoning. By the 1950s much was known about lead poisoning in children. In addition to published research that connected hyperactivity [Note 12] (Winters 1956, Thurston et al 1955) [Note 13 (Klebanoff et al 1954)], delayed speech and speech impediments with lead poisoning [Note 14 (Mellins and Jenkins 1955)] [Note 15 (Mellins and Jenkins 1957)] [Note 16 (Byers and Lord 1943)], Cecil and Loeb's (1955) Textbook of Medicine and Mitchell-Nelson's Textbook of Pediatrics (Nelson 1950) identified constipation, (Cecil and Loeb 1958 p.538) emotional irritability, academic difficulties, sleeping difficulties, (Nelson 1950 p.755) psychological impairment, (Nelson 1950 p.756) muscular incoordination, (Nelson 1950 p.755) attention deficit, (Cecil and Loeb 1958, p.538) poor appetite, and lack of self control. (Nelson 1950 p.755) These findings and more were in evidence in the stuttering children enrolled in Johnson's studies.

Under normal circumstances Dr. Johnson and his colleagues would have brought their suspicions to the attention of others in their field; sought collaboration with experts in lead poisoning; done further testing on the children; counseled the families; designed and conducted additional studies; presented their data at meetings; sought the support of the medical community. And although one or more of these events may have occurred there is not a hint in either the book or in the medical literature that suggests that happened.

But the 1950s were not normal times in Iowa or elsewhere. America's cold war was raging and the crown jewels in the Country's strategy of nuclear deterrence were the factories that manufactured nuclear bombs and missiles. (Shiman 1997) Two such facilities, the Burlington Atomic Energy Commission plant near Burlington Iowa [Note 17], at one time the Country's only nuclear weapons production facility (Carroll 2000), and the Rock Island Arsenal in Rock Island Illinois, near the Iowa border, were within 70 miles of Iowa City. The grounds of the two facilities are widely acknowledged to have been contaminated with lead from industrial waste; lead paint, lead coatings, the milling, machining, and burning of lead and lead alloys and, for the Burlington plant, the legacy of conventional lead-bearing ordnance. [Note 18] (Bricka et al 1994, ATSDR 2010)  Clearly the wage earners of the families of at least some of the children who stuttered (and perhaps most of them) worked at the plants, as they were the largest employers in the area by far.

To threaten a production slowdown at facilities that at the height of the Cold War were feverishly manufacturing nuclear weapons for national defense, over safety concerns stemming from an uncorroborated finding based on "soft science" [Note 19 (Wikipedia 2016d)], that lead brought home by parents (who themselves seemed fairly healthy [Note 20]) on clothing, shoes, skin, hair, etc., (Baker and Landrigan 1971, Pueschell 1996, Woodcock 1977) was poisoning children, at a time when paranoia and fear of Communist aggression were running riot in Washington and elsewhere, would almost certainly have been viewed as political suicide. [Note 21 (Fuortes 2006)] [Note 22 (Carroll 2000)] Given this reality Wendell Johnson may well have been advised that for the good of the University as well as for the sake of his own job to reveal his suspicions to no one.

Assuming that happened it would have left Dr. Johnson and his colleagues with an ethical dilemma. If the data of interest suggested that lead poisoning could cause stuttering in children, how could they get that message out to the world, inspire further study, and still keep their jobs? One guess is that they hit on the idea of hiding the data of interest in plain sight by publishing as an appendix much of their research database, which included the data of interest. Under the sheer weight of an enormous amount of data the appendix would have, to the uninformed reader, dissolved in a blur of numbers allowing the data of interest to, in effect, fade from view if not disappear entirely.

Farfetched? Perhaps. But in 1959 Wendell Johnson inexplicably and uncontestably issued a challenge in the form of a riddle to readers of an otherwise dry scientific treatise. In it he suggested that unspecified data in the Appendix contained information not identified or discussed anywhere in the book. Without giving any hints he invited readers to search for the data and, in his own words, consider the "implications" of any information found. More than 50 years later a search of the Appendix was undertaken following his suggestion. And as was hinted, data in the Appendix do indeed reveal information not mentioned anywhere in the book. A full decade or more before serious research began on the effects of lead in children, the data provide strong evidence that some or all of the children who stuttered had lead poisoning.

Because the history of chronic lead poisoning is one of obfuscation, suppressed information, and missed opportunities, narratives such as these require assumptions and extrapolations of necessity. Without these "leaps of faith" the story would go mute, threatening to repeat itself at some future date. In spite of the uncertainties inherent in the telling, each of the narratives rests on one or more truths: the Cold War was a time of terror and repression for many despite the economic gains of the '50s; children's rights as research subjects were abridged (see Hornblum 2013); lead exposure and poisoning at ammunition plants was a fact of life; children were poisoned by lead brought home on parent's clothing from work; Johnson's data do show very consistent evidence of a link between lead poisoning and stuttering [Note 23]; research in the social sciences was discounted by those in medicine and the other "hard sciences"; researchers do protect their data from unauthorized use as a rule; King George VI, "the stuttering King", did show evidence of lead poisoning; concern about the effect of lead poisoning on speech in children was in evidence by the mid-'50s, and Dr. Johnson did hint in the preamble that data in the Appendix contained unrevealed information. Which if any of the truths relevant to the Iowa experience figured into Johnson's decision to publish the Appendix, and whether in fact he suspected that a link existed between lead poisoning and stuttering, are matters for debate.

Notes:

1. The definition of lead poisoning has been debated for almost a century. Today, any amount of lead in children is thought to be unacceptable.
2. The number of elementary school children enrolled in special education programs for the speech impaired was 254,179 for the 1952-'53 school year, amounting to 65% of all children enrolled in special education programs for the year. For children in secondary school (mainly junior high school) the figures were 52,568 and 48%.
3. In 1959 Johnson estimated the prevalence of speech disorders per 1000 children at 25 for "articulation problems" and 7 for "stuttering". These numbers were at least 7 fold greater than the next most frequent speech disorders, "voice problems" and "fluency and rate problems". Only disorders rated as "severe" were counted. (Office of Education 1959b, p.6). The pathologic process behind all of these disorders may in fact be one and the same, differing only in the precise location of the brain injury. Damage to the brain's basal ganglia has been observed both in individuals who stutter and in those known to have had lead poisoning. And although research has never attempted to link the two, this suggests that damage to the basal ganglia from lead poisoning could be causative for speech disorders.
4. Statistics of Special Education for Exceptional Children and Youth, 1957-'58, p.3. This was the final statistical report of the: Biennial Survey of Education in the United States, 1956-'58, Chapter 5.
5. Differences in the states' abilities to fund special education would not appear to explain the rankings. When total tax revenue for each group of 10 states was divided by the total number of residents in the group, the bottom grouping of 10 differed from the top grouping by only $4 per state resident. Furthermore, special education teaching loads for those handling speech impaired children were considerably lower for the bottom 10 then for the top 10 states in the ranking. This is the reverse of what would be expected were funding an issue.
6. Seventeen percent (17%) of children aged 5 to 14 in Maine lived in Cumberland County. However 91% of Maine's speech defective children enrolled in special education lived there, all in South Portland. South Portland was the home of Todd-Bath and South Portland shipyards, which during the War built 266 ships for the War effort (Wikipedia 2016a)
7. Seven percent (7%) of children in Alabama aged 5 to 14 lived in Mobile County. However 16% of Alabama's speech defective children enrolled in special education lived there. Mobile County was the home of Alabama Drydock and Shipbuilding Co which during the War built 123 ships for the War effort. (Wikipedia 2016b).
8. The maximum distance was arbitrarily set at approximately 100 miles (200 miles round trip) although adjustments were made if programs were adjacent. Adjacent programs tended to be in areas of high population density. One hundred miles was estimated to be what a young family with children could manage if they were to travel to clinic for an appointment, be seen, eat meals, return home in a single day, and do this on a repeated basis. In the case of adjacent programs the distance was as little as 35 miles (70 miles round trip). Adjustments in distance were made in an effort to avoid counting constituents twice due to overlapping program service areas. The availability of U.S. Census data by county necessitated interpolation when estimating population size based on precise distance from a point.
9. Six colleges and universities in Northern Illinois offered degrees in speech correction; Northwestern, Bradley, Normal, Elmhurst, College of St Francis, and Northern Illinois Teacher's College. Together they had 350 students enrolled for the 1953-'54 school year, and together they served a constituency estimated at 1,972,119. For the same school year Northwestern had 236 students enrolled, and within a 25 mile radius of the school served a constituency estimated at 1,237,267. (Enrollment figures from Mackie and Dunn 1954, Appendix A". Demographics from 1950 U.S. Census).
10. Wichita Municipal had a student enrollment of 80 in speech correction for the 1953-'54 school year, serving a constituency estimated at 289,059. (Enrollment figures from Mackie and Dunn 1954, Appendix A". Demographics from 1950 U.S. Census).
11. In the preamble to the Appendix (Johnson 1959), Dr. Johnson wrote, “the main purpose of making the findings [of Studies II and III] available in this detailed fashion are to allow essential reference to them in the body of the report and to encourage further evaluation of them and continued development of their implications, not only by students of the stuttering problem but also by…medical investigators and others."
12. Hyperactivity is sometimes referred to as "restless"; "hyperkinetic"; "overactive".
13. Although the review paper (Klebanoff et al 1954) does not address lead poisoning it does address brain damaged children. It had long been known by the 1950s that lead poisoning in children could result in anatomically demonstrable brain damage. "Descriptive studies of the motor performance of [traumatically brain damaged children], wrote the authors," characterize them as hyperkinetic, overactive, restless, impulsive, and incoordinated."
14. Mellins and Jenkins (1955) is a case study of 21 children, 7 of who were found to have serious impairment of speech and language as a result of lead poisoning; from page 18, "it appeared from the behavior of the children during the test sessions that some knew what they wanted to say but could not express it vocally. They seemed frustrated by this inability to verbalize. Six had speech impediments acquired during the acute illness. Others, though they had no speech impediment, did not talk much."
15. Jenkins and Mellins (1957) is an extension of the Mellins and Jenkins (1955) study published in J.A.M.A. in 1955; from page 75, "two years following hospitalization the damaging effects of lead can still be seen, especially in impaired speech…" [18 of the 46 cases had acutely impaired speech].
16. In a study by Byers and Lord (1943), several of the children had delayed or poor speech following lead poisoning.
17. The Burlington factory (originally, and again later, known as the Iowa Army Ammunition Plant) began manufacturing ordnance early in WWII. After the war the plant took on the additional role of manufacturing and assembling nuclear weapons. Growing the Country's nuclear arsenal was a top priority for Washington during the 1950s and a key part of the Nation's strategy of nuclear deterrence. Lead contamination of the grounds at the sprawling manufacturing facility has been widely acknowledged.
18. Whether occupational lead poisoning occurred at this plant is not known. However, lead poisoning occurred commonly in workers at ammunition plants in Indiana, Kansas, and Illinois (letters on file, file boxes 79, 36, and 43; at the Robert A. Kehoe archive, Henry R. Winkler Center for the History of the Health Professions, University of Cincinnati Libraries, Cincinnati, Ohio).
19. "Soft science" was a derogatory term sometimes used by researchers in the "hard sciences" (medicine, physics, chemistry, engineering, etc.) to describe research done in the social sciences (sociology, psychology, speech pathology, public health, etc.). "Soft" was in reference to the belief by some that social science research "endpoints", often gathered from questionnaires (e.g., the number of times a "yes" response is recorded versus the number of times a "no" response is recorded is an example of an endpoint), could not be dispassionately reproduced with the reliability and accuracy of, say, a blood pressure or temperature measurement. Acknowledging this as a weakness, social scientists, Johnson and his associates included, employed techniques that specifically addressed this problem. These included the use of "interlocking" questions (seeking exactly the same information using two or more differently worded questions), finely honed interviewing techniques, reducing distractions by interviewing study subjects individually, testing the same research hypothesis in two or more studies, seeking exactly the same information from two or more study subjects and then comparing answers, etc. Parenthetically, much of the research of the effect of cigarettes on health was the work of social scientists.
20. Although this is an assumption it is probably a safe one to make. Compared to children adults can tolerate a significantly higher dose of lead before poisoning becomes blatantly obvious. However even today the health effects of long-term exposure to low doses of lead in young and old alike are incompletely understood.
21. In testimony before Congress in 2006, Dr Lawrence Fuortes, (Fuortes 2006) Professor of Public Health at the University of Iowa gave comment on working conditions at the Plant in the 1950s;" These workers labored under a great weight of secrecy…. [They and their families] said at first that the government was only waiting for them to die. Sadly the facts and history appeared to bear this out. The impression among many workers and their families is that the workers had been put at risk, made ill, and died as a result of their work, yet the government was merely going to stall and deny."
22. Dennis J Carroll, a reporter for the Boston Globe, interviewed former Plant workers in 2000. His report appeared in the Globe on May 29, 2000. Mr. Carroll wrote, "Vaughn Moore, a former guard at the plant, painted a dark picture of conditions at the plant. 'Talking about your work was strictly taboo. Back in them days, they would tell you, ' Run your mouth and you're going to Leavenworth Penitentiary', said Moore. 'They had 15 FBI agents stationed in this town', he said. 'All they did was run around in bars listening, grocery stores listening. They knew what clubs you belonged to, they knew where you ate, they knew where you went fishing. They knew all about you', Moore said. 'They knew more about you than you knew about yourself.'" (Carroll 2000)
23. To read a description and analysis of the evidence, written by the current author, go to https://lead.org.au/bellsystemleadpoisoning/images/Johnson_analysis.pdf

References:

1950 U.S. Census. Digital census data obtained from Social Explorer, Inc., Oxford University Press, NY, NY.

ATSDR (Agency for Toxic Substances and Disease Registry), CDC (Centers for Disease Control) (2010) "Public Health Assessment: Iowa Army Ammunition Plant, Middletown Iowa." http://www.atsdr.cdc.gov/hac/pha/pha.asp?docid=1108&pg=1 Page last updated April 7, 2010.

Baker E.L. and Landrigan P.J. (1971) "Lead in children of lead workers; home contamination with industrial dust", The New England Journal of Medicine, 296 (5), pp 260-61; Feb, 1971.

Bennett, J.W.W. (1958) King George VI: his life and reign; St Martin’s Press, NY, 1958.

Bricka RM, Williford CW, and Jones, LW.; "Heavy Metal Soil Contamination at U.S. Army Installations: Proposed Research and Strategy for Technology Development. Technical Report IRRP-94-1, 1994". http://acwc.sdp.sirsi.net/client/search/asset/1004530 

Byers RK, and Lord E.E. (1943) "Late effects of lead poisoning on mental development"; American Journal of Diseases of Children, 66 (5); Nov. 1943.

Carroll, Dennis J (2000) "'Forgotten' Nuclear Weapons Factory Poisons Iowa Town." Boston Globe; Monday, May 29th, 2000. http://commondreams.org/headlines/052900-02.htm

CDC (Centers for Disease Control), 2013, "Lead screening during the domestic medical examination for newly arrived refugees"; Division of Global Migration and Quarantine, U.S. Department of Health and Human Services, 2013. http://www.cdc.gov/immigrantrefugeehealth/guidelines/lead-guidelines.html

Cecil, Russell and Loeb, Robert, eds. (1955) A Textbook of Medicine. Ninth Edition; pps. 536 ff; W.B. Sanders Co. 1955.

Fuortes, L (2006) Testimony of Laurence Fuortes, MD Professor, Occupational and Environmental Health College of Public Health University of Iowa Before the House Committee on the Judiciary Subcommittee on Immigration, Border Security, and Claims Oversight Hearing: “The Energy Employees Occupational Illness Compensation Program Act: Are We Fulfilling the Promise We Made to Cold War Veterans When We Created the Program? (Part IV)” http://cph.uiowa.edu/IowaFWP/documents/Fuortes_testimony.pdf November 15, 2006.

Gore, John (1945) King George V: a personal memoir, pps.104ff; John Murray, Albemare St., London, 1949.

Hornblum, Allen M. (2013) Against their will: the secret history of medical experimentation on children in cold war America; Palgrave Macmillan, 2013.

irock@4grc.com (2009) "Blackwell Uncovered" at http://blackwelluncovered.com/Blackwell_Zinc_Smelter.html 2009.

Jenkins M.A., and Mellins R.B. (1957) "Lead poisoning in children: a study of forty-six cases", A.M.A, Archives of Neurology and Psychiatry, 77(1); pp 70-78, 1957.

Johnson, Wendell (1959) “The Onset of Stuttering: Research Findings and Implications“ Book published by the University of Minnesota Press, Minneapolis, March 16, 1959.

Junge A, and Bean R. (2006) "A short history of the zinc smelting industry in Kansas"; Kansas Department of Health and Environment, 2006. http://www.kdheks.gov/remedial/articles/smelterhistory.pdf

Kansas Geological Survey (2005). "GeoKansas: a place to learn about Kansas geology". http://www.kgs.ku.edu/Extension/ozark/mining.html Updated May 5, 2005.

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Widipedia (2016b) Alabama Drydock and Shipbuilding Co. https://en.wikipedia.org/wiki/Alabama_Drydock_and_Shipbuilding_Company This page was last modified on 7 October 2016.

Wikipedia (2016a) New England Shipbuilding Corporation. https://en.wikipedia.org/wiki/New_England_Shipbuilding_Corporation This page was last modified on 2 October 2016.

Wikipedia (2016c) Blackwell, Oklahoma Zinc Smelter. https://en.wikipedia.org/wiki/Blackwell,_Oklahoma#Zinc_Smelter This page was last modified on 19 November 2016.

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[i] ibid, Biennial Survey 1952-'54, page 5