Fluorine Intoxication by Kaj Roholm (1937)


Below are selected quotes from Danish researcher Kaj Roholm’s 1937 book Fluorine Intoxication. All emphasis is original. Roholm reviewed the state of knowledge regarding acute and chronic fluorine poisoning at that time, and also described his own investigation into cryolite factory workers in Copenhagen, and his experiments on animals. Note that “fluorine” here refers predominantly to various forms of fluoride, including cryolite, not fluorine gas, though some covalent fluorine compounds are mentioned. Fluoride is the ionic form of fluorine.

It has to be said that although the bone and ligament changes in cryolite workers observed by Roholm are certainly of interest, as far as providing a representative sample of the general population of working age is concerned, the workers at the Copenhagen cryolite factory were about as bad as it gets. Evidently a large proportion of those who started work there could not tolerate the working conditions for long, which is likely to have been due to the fluoride poisoning they were suffering in most cases. Therefore most or all of those who were unusually susceptible to fluoride toxicity would have been weeded out, and probably also many with approximately average susceptibility. Effects on joint function were inherently self-limiting, because if a worker’s ability to do the job was seriously impaired they would presumably no longer be employed at the factory, and hence be removed from the source of high fluoride exposure. Also, the youngest worker was 20 years of age. Some of the workers may have started at an earlier age, but there is no reason to believe that any were exposed to fluoride at the factory throughout their lives, or as foetuses, in contrast to the situation with forced-fluoridation. Roholm’s investigation also lacked a control group and was not longitudinal, and must therefore be regarded as revealing only the tip of the chronic fluoride poisoning iceberg.

To mention a few highlights from other parts of the book, Roholm’s comparison of the abundance in the earth’s crust of fluorine with that of lead, arsenic and mercury has a touch of the prophetic about it, considering that all four are now known to be developmental neurotoxicants, and not nutrients. He confirms that sodium fluoride and sodium fluosilicate were used as mouse and rat poison. He is also adamant that fluoride is not necessary for healthy teeth. More than 75 years later, the US Institute of Medicine and others are still trying to claim that fluoride is some kind of quasi-nutrient.

p 2 “In commerce we find hydrofluoric acid and hydrofluosilicic acid, the minerals fluorspar (CaF2) and cryolite (Na3AlF6), silicofluorides, which are a by-product of superphosphate manufacturing, and divers synthetically made fluorides.”

p 3 “Fluorine minerals have been known since the Middle Ages.”

p 4 “A dental disease in man, mottled enamel, which Black and McKay described in 1916 as occurring in Colorado, has proved to be rather widely distributed in several parts of the world. The aetiology was unknown until 1931, when Smith, Lantz and Smith demonstrated by means of animal experiments that the disease was caused by a relatively high fluorine content in the drinking water. Independently of their work, Velu proved that a common dental ailment in North Africa among animals and man, darmous, was of the same origin.

Since the close of last century there are records of a number of cases of acute poisoning in man by various fluorine compounds. Chronic human poisoning with bone symptoms was described for the first time in 1932, by Flemming, Moller and Gudjonsson, in cryolite workers.”

p 9 “In practice it is assumed that highly diluted solutions of hydrofluoric acid are not dangerous; this, however, to a great extent depends upon how long the influence is allowed to act.”

p 26 “In Table 4 I have summarized the various symptoms in 34 cases of fatal poisoning. Broadly speaking the symptoms may be gathered into two groups, one expressing an acute local irritation of the gastro-intestinal canal, the other indicating both an irritating and a paralysing effect on the central nervous system or musculature.” This indicates neurotoxicity.

p 33 “Caries does not seem to be especially frequent in the moderately attacked [by dental fluorosis] teeth. Still, the enamel is more brittle than normally, is inclined to chip off, and fillings do not hold well.”

p 33 “At the time of Black and McKay’s investigations [into mottled enamel] it was the popular belief that the anomaly was associated with drinking water, especially from artesian wells. Where the water supply was changed it was possible to stop the development of the anomaly in an affected region. Analyses of the water showed nothing abnormal, however.”

p 34 “We may now regard it as an established fact that mottled enamel is caused by a relatively high fluorine content in drinking water.”

p 46 “According to Washington, who embarked on a calculation of the chemical composition of the earth’s crust, fluorine stands thirteenth among the elements in order of importance, before the other halogens and far ahead of toxic elements like lead, arsenic and mercury. Phosphorus occupies the tenth place with 0.13 per cent.; fluorine is at 0.077 per cent.”

p 46 “Of particular importance is the rich occurrence of native phosphate or phosphorite, deposits of calcium phosphate in amorphous form, the raw material in the manufacture of superphosphate. In almost every case they contain fluorine, most frequently 2 to 5 per cent., varying in the different deposits.”

p 53 “In 1803 Morichini observed the evolution of hydrofluoric acid vapours when treating a fossil elephant tooth with sulphuric acid.”

p 60 “Isolated cells or tissue placed in a solution of sodium fluoride are destroyed quickly as compared with equimolecular solutions of the sodium salts of the other halogens. In this respect fluorine stands out from the group.”

p 70 “The apparent difference in the toxicity of sodium fluoride and sodium fluosilicate lies in the different fluorine content. (NaF: 45.24 per cent. F; Na2SiF6: 60.54 per cent. F). Allowance being made for this, the two compounds are equally toxic, even with parenteral administration.”

p 84 “A series of rat experiments at Iowa Agricultural Experimental Station showed that on a diet containing fluorine the succeeding generations were less prolific than the first generation”

p 93 “Fluorine has a detrimental effect on the growth of the teeth, whereby the part of a tooth calcifying during the period fluorine intake will acquire permanent defects.”

p 104 “As a rule the excreted quantity [of fluoride] was about half of the intake [in a dog].”

p 106 “Fluorine seems mostly to be excreted in the urine, in what form is not known.”

p 112 “Bones were skeletonized very carefully, and periosteum and marrow removed as far as possible. Soxhlet’s apparatus, or a rotating benzine drum, was used for defatting. The material abstract it for analysis was carbonized at low temperature and pulverized in an iron mortar. Incineration proceeded as with the organs, as a rule taking 3-5 hours. No calcium oxyde was added to bones and teeth. [details of Roholm’s investigation]”

p 130 “The pay [at the cryolite factory] is relatively good, partly based on piece-work. The working week consists of 48 hours. For a number of years the workers have had a week’s summer holiday with pay, and with every form of illness about one-fourth of the wage in sick benefit for a maximum of 13 weeks. On discharge, older, deserving workers receive a small pension. The drawbacks are, apart from the toxic effect of the cryolite, the generally laborious character of the work and the almost omnipresent dust.”

p 131/2 “During the past ten years for which it has been possible to obtain information, a certain number of the workers have only been employed a short time; it is possible that to a certain degree this is due to the character of the work. In the period comprised by Table 19, 23 men (16.2 per cent.) and 39 women (19.6 per cent.) worked for less than a month. In both groups are persons who were only one or few days at work and have not since been taken on again. It seems probable that for these workers it may just as well have been discomfort at the work as unfitness for it. No doubt the work makes considerable demands on the physique, but otherwise it is not especially exacting for the great majority of the workers. The relatively large number of re-engagements in both the male and the female group (16.9 and 26.8 per cent.) on the other hand indicates that the drawbacks of the work are not deterringly great. Similar importance may be attached to the circumstance that many of the former and present workers are related to one another. Though most of the workers in the period have worked for less than two years, a number have been employed for much longer: sixteen, of both sexes (4.7 per cent.) for ten years or more, generally uninterruptedly. As will be seen later, the average period of employment for the persons working at the time of this investigation was much longer (10 years). Although suitable comparative material is lacking, it would seem to appear from the statistics, however, that the work is connected with certain drawbacks, the effect of which is that the average period of employment is rather short, but that the injurious effect is not so considerable that it prevents employment over a long stretch of years.”

p 132 “No worker was under 20 years of age.”

p 132 “In many cases the length of employment was considerable, on an average 10 years; 21 workers (30.9 per cent.) had worked there for ten years or more, 5 workers (7.4 per cent.) for 25 years or more. This picture of the length of employment is much more favourable than that of conditions considered over a longer period of years (Table 19). Probably the cause of this is that the number of hands at the factory has gone down in the course of the last few years and that on principle the hands of the discharged were those who had been employed the shortest time. Still, there is no doubt that some selection is made, whereby workers who tolerate the work best remain longest at the factory.”

p 134 “With the assistance of the factory’s books a search was also made for former workers, and it was possible to get in touch with 131 people, 69 men and 62 women, who had worked at the factory for at least six months.”

p 136/7 “Symptoms to be recorded had to be of a certain intensity or duration, so that accidental feelings and the like were disregarded. Naturally a certain amount of error is inherent in personal decisions of this kind. In such a method the numerical statement of symptom frequency leaves a summary, massive impression that does not correspond to the discomforts present at the daily work. Only two of the workers, one male and one female, denied ever having felt discomfort from the work or having noticed morbid symptoms at all. The others indicated a whole conglomeration of symptoms which are recorded in Table 22 according to frequency. The commonest complaints were of various dyspeptic phenomena, shortness of breath and rheumatic attacks.”

p 138 “The rule is that for a period of some few days to some few weeks after starting at the factory worker suffers from these acute gastric attacks, whereafter they disappear, especially the nausea and vomiting. Thereafter some of the workers tolerate the dust without observing the symptoms; others will still have transitory symptoms after holidays, or if the dust quantity temporarily becomes especially high.”

p 141 “The bone changes are very characteristic and form the basis for a division of the disease into phases.”

p 141-6 “1st Phase.

The changes are observed in pelvis and columna, but are doubtful or absent elsewhere. The density of the bone is very little increased. The trabeculae are rough, blurred and give deep shadows; this is often distinct in corpora of the lower lumbar vertebrae. The bone has both a more prominent and a more blurred structure at the same time, which is very characteristic when the operator is familiar with the phenomenon, but otherwise is easily overlooked (Fig. 17). The bone contour is sharp. In some few cases there is incipient osteophyte formation on the edge of corpora of the lumbar vertebrae. The boundary against the normal bone structure is not sharp, and in an isolated case it will be difficult to decide whether the change is a normal variation or a pathological finding. In serial examinations, however, the difference is distinct.

2nd Phase.

The bone structure is blurred, the trabeculae merging together. Over often rather large areas the bone gives a diffuse, structureless shadow. At first glance the negative seems to have been underexposed, but it is difficult or impossible to distinguish details even when the time of exposure or the tension is increased. The bone contours are uneven and somewhat blurred. The changes are most distinct in pelvis (Fig. 18) and columna (Fig. 20), but also in the ribs (Fig. 27) and in the bones of the extremities, even if there they are less pronounced and often resemble the changes described as 1st phase. In the extremity bones the medullary cavity is usually moderately narrowed. In columna there are incipient or moderate ligament calcifications, especially caudally; they appear in the form of pointed, beaked osteophytes with an inclination to form bridges between the vertebral bodies or as a diffuse blur lying posteriorly to corpora. In some cases (particularly among the younger individuals) the ligament calcifications are absent, though the bone structure is so changed that the case must be placed to be 2nd phase.

3rd Phase.

On the negative the bone presents itself as a more less diffuse marble-white shadow, in which the details cannot be distinguished. Changes are observable in all bones but are still greatest centrally, being most conspicuous in bones with cancellous structure, pelvis (Fig. 19), columna (Fig. 21-24), ribs and sternum (Fig. 28). In the bones of the extremities there are changes in the structure that recall the 2nd phase, or fairly often only the 1st phase. In the worst affected individuals changes are to be seen in the cranium, usually rather moderate in intensity (Fig. 26). Theca is denser and gives a deeper shadow than normally, sutures and vessel grooves are indistinct, and the same applies to impressiones digitatae. The air-sinuses in the cranial bones are not diminished in size. The region around sella turcica gives a deep shadow but is normal as to contour. No distinct thickening of processus clinoidei was observed.

The bone contours almost everywhere are woolly and blurred. Very often the bones or certain parts of them have a rough and slightly enlarged appearance, but otherwise the shape is not altered.…

If the result of the Röntgen [x-ray] examination is to be summarized, the first thing to emphasize is the fact that the affection is a system-disease, for it attacks all bones, though it has a predilection for certain places. The pathological process may be characterised as a diffuse osteosclerosis, in which the pathological formation of bone starts both in periosteum and in endosteum. Compacta densifies and thickens; the spongiosa trabeculae thicken and fuse together. The medullary cavity decreases in diameter. There is a considerable new-formation of bone from periosteum, and ligaments that normally do not calcify or only in advanced age undergo a considerable degree of calcification. All signs of bone destruction are absent from the picture.

The characteristic changes of the osseous system were frequently found. Of the 68 workers 57, or 83.8 per cent., had bone changes which were assignable to one of the aforesaid three phases*). Their actual distribution appears from Table 24. Taking them all round, men and women were attacked equally severely. In 11 workers (16.2 per cent.), 9 men and 2 women, conditions were normal. About the same number of cases could be placed to 1st and 2nd phases, 38.2 and 35.3 per cent. respectively. Only 7 workers had changes of the 3rd phase, and six of them were men.

The degree of the osteosclerosis was on the whole connected with the period of employment; but there were quite a number of exceptions (Fig. 32).… One point of practical importance is the shortest period of employment within each group. Cases of the 1st phase were observed after 2 [and] 5/12 years work, of the 2nd phase after 4 [and] 10/12 years, of the 3rd phase after 11 [and] 2/12 years. On the other hand the changes were slight in a certain small number of the workers, even after long employment; changes of the 1st phase were observed in persons who had been employed 18, 24 and 33 years respectively. One female worker had no bone changes, though she had been employed for 24 years with one interruption.

The relation between exposure to dust and the degree of osteosclerosis is shown in Table 24. Of the 39 workers exposed to moderate dust 9 had no bone changes; among the remainder all phases were represented, but mostly phases 1 and 2. In the group with slight exposure to dust there was only one case of 2nd phase and none of 3rd. On the other hand there were bone changes, severe as a whole, in all workers who had been exposed to much dust. Broadly speaking it is thus possible to demonstrate an actual relationship between the exposure to dust and the degree of bone changes.…

When examining the motility very considerable changes of columna were observed. In 35, or rather more than half of all workers (23 men and 12 women), motility in columna was restricted, both flexion-extension and rotation.… In the slightest cases there was merely a little stiffness of pars lumbalis and thoracalis with slight restriction especially of extension and rotation. Much the greater number, 21 persons, belonged to this group. The moderate cases presented a rather marked rigidity of the lumbar and dorsal region, but not of the cervical region. It was possible for them, as a rule with some difficulty, to pick up an object from the floor by bending the knees; this group contained 10 workers. Among the most severe cases, four elderly men…, there was practically complete rigidity of the entire spine and a more or less pronounced restriction of the head movements.”

p 147 “It was noteworthy that only some of the workers whose motility in columna was moderately restricted complained of stiffness”

p 148 “Compared with the normal weight according to Brugsch*), 49 workers were too heavy (from 1 to 42 per cent.) and 18 too light (from 1 to 14 per cent.).”

p 148/9 “On the whole the state of the teeth was bad, with a high caries frequency and unsatisfactory care.”

p 161 “The normal excretion of fluorine in the urine is very small, only fractions of a milligramme in the course of the 24 hours. As might have been expected, the fluorine excretion of the cryolite workers was much greater, up to 2.5 mg., or about 10-20 times the normal.”

p 162 “The addresses of 170 former workers were traced. To 134 of these, all who had worked at least six months at the factory, were sent the question-form mentioned on page 134”

p 162/3 “It appears from Table 34 that these symptoms [loss of appetite, nausea, vomiting, irregular movement of bowels, cough, headache and tiredness] as a whole were complained of more frequently by the former than by the present workers, but that otherwise there is great conformity between them.… With the reservation one must take when comparing particulars collected in different ways, the result seems to permit of two conclusions: (1) The statements of the present workers regarding the discomforts of their work are correct; (2) in the course of time a selection takes place, whereby the individuals suffering least discomfort from the work, either primarily or by habituation, remain at the factory. That this latter conclusion is correct is supported when we consider the relation between the length of the period of employment and the frequency of the complaints (Table 35). Of the workers who had been employed between six months and three years, 89.9 per cent. made complaints; in the group with a period of employment of five years or more, only 76.9 per cent. of the workers complained of having or of having had the discomforts concerned.”

p 169 “The average employment time in the period [January 1st, 1923 to January 4th, 1933] has been 3.3 years for men and 2.0 years for women”

p 178 “Arthritic and rheumatic affections have a marked frequency among cryolite workers, 22.6 per cent. of the men’s and 16.5 per cent. of the women’s sick-days falling within this group.…
With regard to post-employment affections only one or two points need be discussed. Affections of the nervous system and sensory organs have a very high frequency among both men and women (17-18 per cent. of all sick-days). These include especially such sickness reports as neurasthenia, neuralgia, nervous rheumatism, etc. Tuberculosis is still a disease of rather infrequent occurrence. Arthritic and rheumatic affections again are very frequent among the men, but no longer among the women.…
The marked frequency of nervous disorders after employment has ceased might indicate that cryolite has a particularly harmful effect on the central nervous system. Or it is probable that even after the termination of employment at the factory the bone changes may give symptoms for which there is no organic substratum observable during an ordinary examination.”

p 192 “The fluorine content of the bones [of two dead cryolite workers] was very high. Expressed per thousand of the bone ash the fluorine content of worker No. 55 varied from 7.6 [ie 7600 ppm] (femur) to 13.1 (lumbar vertebra), of worker No. 200 from 3.1 (os frontale) to 9.9 (sternum, costa). Thus the fluorine content was highest in the worker with the longest period of employment.”

p 194 “In costae of individuals not known to have been exposed to fluorine ingestion beyond the average I found [480-2100 ppm] fluorine, in most cases less than [1000 ppm].

In making an approximate calculation of the absolute quantity of fluorine in the osseous system it is necessary to take the weight of the bones into consideration. The total air-dried skeleton of three adult male individuals*) weighed 4270, 4805 and 4780 g. respectively, or an average of about 4600 g. If we take it that 65 per cent. of the skeleton consist of ash and that the distribution of fluorine is uniform in the bones, it means that the osseous system of adult individual normally contains between 1.5 and 6 g. of fluorine. As has been stated, the weight of the bones of the cryolite workers was considerably increased.…

The weight of the bones examined was roughly three times the normal in the first case, and twice in the second case. If we reckon the ash content as normal and the average fluorine content [10,000 and 8000 ppm] respectively, it means that the osseous system of the two cryolite workers contained about 90 and about 50 g. fluorine.”

p 200 “It is an established fact that cryolite dust contains the toxic substance, and a priori it is probable that this toxic substance is the fluorine contained in the cryolite. Sodium is not toxic in this particular connection. According to experience so far, there is good reason for the assumption that aluminium compounds are not toxic when ingested perorally, presumably because they are not absorbed at all from the alimentary canal.… In a weak hydrochloric solution cryolite splits, forming hydrogen fluoride, and we must take it that this process goes on in the stomach. In subsequent chapters it will be shown that sodium fluoride and cryolite qualitatively have the same toxic effects in animal experiments.”

p 200 “When dealing with cryolite worker No. 55, who was examined post mortem, it was calculated approximately that his bones contained about 90 g. of fluorine. That man had been employed about 25 years at the factory, or roughly 7500 working days. This corresponds to a daily absorption of 12 mg. fluorine. If to this we add the daily excretion in the urine, which according to the sample test is small (2-3 mg.), we arrive at values of 14 to 15 mg. of fluorine.”

p 205 “The fluorine content was highest in the cancellous bones”

p 207/08 “Diagnosis may cause difficulty in cases where there is no occupational intoxication with obvious exposure to fluorine. The clinical symptoms are not characteristic. Cases with rigid vertebral column may clinically resemble chronic ankylosing spondyloarthritis (Bechterew), though this principally is a joint disease. Röntgen [x-ray] examination is of vital importance to the practical question of diagnosis; the changes are first recognizable in pelvis and columna lumbalis. The Röntgen picture of the osteosclerosis caused by fluorine differs from the picture of other diffuse osteoscleroses.”

p 208 “Among the elderly workers the stiffness of columna and thorax involves a certain invalidity, but no greater than that all the workers examined could do their work. This is owing to the fact that elderly employees are put on work that makes relatively little demands on their physique.”

p 209 “The average period of employment for workers with incipient or moderate ligament calcification (2nd phase) was 9.7 years; the severe calcifications were found in workers who on an average had worked at the factory for 21.1 years. It is of practical importance that sclerosis of the 2nd phase was already observed after [4 years, 10 months’] work, of the 3rd phase after [11 years, two months]. Incipient sclerosis (1st phase) may or may not affect motility.”

p 260 “The question of the distribution of fluorine in enamel and dentine has been answered in earlier investigations by the assertion that enamel contains just as much, or even more, fluorine than dentine does. It is still the popular view that fluorine is preferably deposited in the dental enamel, but undoubtedly it is wrong. The author’s investigations… have shown that fluorine is deposited principally in dentine, and to a smaller extent in enamel

p 265 “In human intoxication death has been seen from a dose as low as about 6-8.6 mg. fluorine per kg. body weight, corresponding to 0.7-1 g. sodium fluosilicate. The lethal dose has probably been smaller still, but the records are not precise. Most lethal doses are much higher; as much as 10 g. sodium fluoride have been survived, corresponding to about 65 mg. fluorine per kg. (Table 6). Man seems to be more sensitive to fluorine compounds than the experimental animals generally employed. The risk of a fatal ending in acute peroral intoxication is considerably reduced by vomiting, which occurs almost constantly.

p 267 “The acute effects of fluorine compounds cannot be explained as the result of a purely calcioprive mechanism, or at any rate only with difficulty. For example this is true of the blocking of the cell membrane of the erythrocytes, with the subsequent inhibition of the coagulation of the blood, the formation of fluorhaemoglobin, and the destructive effect on the development of the teeth. One must here refer to the very considerable effect which fluorine has on both protoplasm and enzymatic activity in vitro (Chapter V), and which opens up wide possibilities regarding our understanding of the actual effect of fluorine in the organism.”

p 268 “A search for fluorine ought to form part of the routine of forensic-chemical investigation.

p 279 “Fluorine is deposited in the teeth, though not so much as in the bones.… The author’s analyses indicate that fluorine is deposited in the enamel in only small quantities.”

p 279/80 “Furthermore, it may be stated that a number of circumstances affect the sensitivity of the organism to fluorine; a uniform condition can be produced with varying doses. Apart from the quantity of fluorine in proportion to the body weight, there are such important aspects as the fluorine compound employed and the time factor, the nature and age of the individual, and the diet.”

p 281 “man is much more sensitive to fluorine than the rat

p 281/2 “The period in which fluorine must work on the organism before the symptoms of intoxication develop is extremely variable and chiefly dependent on the dose.”

p 282 “Sensitivity to fluorine is influenced by the content of calcium, phosphorus and vitamin D in the diet.”

p 287 “Considered from a diagnostic angle, chronic fluorine intoxication presents itself in the form of three clinical units: The tooth anomaly, the osteosclerosis, and the ostemalacic condition accompanied by general symptoms.”

p 287 “In man the tooth disease is known as mottled teeth, mottled enamel, darmous, dientes veteados and denti scritti;

p 289 “One common feature of the three manifestations of chronic fluorine intoxication is that isolated cases may be difficult to diagnose.”

p 290 “A fluorine content of more than [2000 ppm] in bone ash and more than [1000 ppm] in tooth ash would, however, cause one to suspect an abnormally high fluorine intake.”

p 291 “As to the treatment of chronic fluorine intoxication, very little may be said. Continued fluorine ingestion must be prevented, if possible. The tooth changes are unaffected by therapy; the pigment can be bleached by oxygenous means, but the effect is not permanent. On the basis of what has been explained under the pathogenesis it will be logical to put the intoxicated individual on a food rich in Ca, P, and vitamins, especially C and D.”

p 293 “The threshold concentration [in drinking water for mottled teeth] will probably prove to be variable, for example depending on the other mineral constituents of the water.”

p 295 “Working on the extraction of phosphorite presents no risk of intoxication, apparently, probably on account of the low fluorine content of the mineral and the low solubility of the fluorine compounds involved*)

*) Recent observations show that the slightly soluble complex compounds between fluorine and calcium phosphate in apatite and phosphorite may produce fluorine intoxication. Bishop describes a case of osteosclerosis in a man employed for 18 years in a fertilizer factory, where he had handled finely ground rock phosphate (3.13 per cent. fluorine). Speder found osteosclerosis in natives attacked by darmous (Morocco). The intoxication is caused by dust rich in fluorine from the great deposits of phosphorite in North Africa. Wolter, Ablina and Kremnewa have shown experimentally that the fluorine compounds in apatite, phosphorite and superphosphate are toxic. Signs of chronic fluorine intoxication (bone changes on X-ray examination, anomalies in tooth development, increased fluorine content of bones) were seen in dogs which for up to 14 months received 1-9 mg. fluorine daily per kg. body weight in the form of dust of the products mentioned above. Gastric acid plays an important role in the transition of fluorine to soluble form.”

p 296 “In the manufacture of superphosphate the raw material, phosphorite, is treated in enclosed systems with sulphuric acid, whereby the phosphoric acid is converted into a water-soluble form that is absorbable by plants. Treating with acid results in the development of hydrogen fluoride (HF) and hydrofluosilicic acid (H2SiF6), which, by absorption in water and with the addition of sodium chloride, can be converted to the by-product sodium silicofluoride (Na2SiF6). In former times it seems to have been the normal method to eject the volatile fluorine compounds into the atmosphere through the factory chimney, or to lead the liquid from the absorption chamber to the waste water after neutralization with lime. Nowadays the fluorine compounds are collected and extracted to a certain extent, but the problem is still discussed in various industrial countries. For example, DeEds calculated recently that in the manufacturing of superphosphate in U.S.A. there is an annual loss of 25,000 tons of fluorine, ejected in gaseous form.” [A discussion of the use of fluoride in other industries, including aluminium manufacturing, follows.]

p 298 “The mysterious fog disaster which occurred in the Meuse Valley near Liège (Belgium) in the beginning of December 1930, most probably was an acute fluorine intoxication.”

p 301 “The high toxicity of the fluorine compounds has led to their application as a rat and mouse poison. In most cases they are used in the form of sodium fluoride or sodium fluosilicate, which are effective, relatively cheap, and have no pronounced taste. They are sold on the market under proprietary names and seem to have been used for this purpose for the first time in Germany after the war. Their use against noxious insects dates from last century. The first case of poisoning with one of these preparations was in 1899. Judging from the many patent-preparations and the number of poisoning accidents, their use is widespread.…

A modern use, one that is constantly growing, is as an insecticide for plants.… The interest taken in it is considerable, partly because it is hoped the fluorine compounds will be a remedy just as effective as the arsenic compounds and less dangerous to man, partly because the industry requires an outlet for the fluorine compounds gained as by-products of superphosphate manufacturing.”

p 304 “Compared with the other halogens, fluorine has been little used in therapy. Most of the uses rest on a slender foundation, often indeed erroneous, and in many cases apply to diseases in which the effect of the treatment is difficult to judge.”

p 305 “On a purely speculative basis Crichton-Browne in 1892 recommended fluoric food for pregnant women and four children for the purpose of counteracting caries: there being fluorine in the teeth, the element must be of importance to their strength. Brissemoret had a similar ideas as regards the osseous system, and advocated a strengthening therapy with administration of calcium fluoride. In homoeopathy this treatment is still persisted into some extent. Calcium fluoride in small quantities is used against both otospongiosis and otosclerosis. On the basis of the productive bone changes in human cryolite poisoning Flemming Moller and Gudjonsson suggested the possibility of treating rarefying bone diseases by fluorine compounds. The use of phosphorite as a mineral supplement in animal husbandry may be regarded as abandoned, now that the toxic effect of fluorine has become known.”

p 305 “Hyperthyroidism. In 1881 Woakes tried treating struma with small doses of hydrofluoric acid administered perorally. Goldemberg reintroduced the treatment in 1930; he employed intravenous injections of sodium fluoride (0.04-0.06 g. at a time, a total of 1 g. being given over a period of several days), or peroral administration. Curative effect has been observed even in severe cases where other therapy proved ineffective. The treatment has been tried elsewhere, apparently with good results. Gorlitzer employs baths with hydrofluoric acid and considers that the undissociated HF-molecule can permeate the intact skin.”

p 305 “Inhalation of air containing hydrogen fluoride has been tried for diphtheria and malaria.”

p 308 “The addition of fluorine compounds to food of every kind should be forbidden.”

p 309 “The [insecticide] spray residue problem is one that has attracted great interest in U.S.A. From this angle fluorine is regarded as the same as arsenic and lead, for which elements the U.S. of America have established maximum permissible limits for their content in fruit”

p 310 “It would be desirable to forbid the employment of males under 18 years, and females as a whole, on work with fluorine compounds which give off dust or vapour.”

p 310 “Physicians should be obliged to notify all diseases acquired while working with fluorine compounds.”

p 311 “Examination for fluorine ought to form a part of the medico-forensic investigation of acute intoxications of vague aetiology, in the routine analysis of drinking water*), and in the chemical analysis of food.”

p 312 “The constant presence of small quantities of fluorine in organic material might indicate that the element plays some role in the physiology of the organism. The mere presence of the element is no confirmation that it does so, but a necessary consequence of the widespread occurrence of fluorine in inanimate nature.”

p 312/3 “Sharpless and McCollum gave young rats a diet which as far as possible contained no fluorine. Growth and reproduction down to the third generation were not inferior compared with rats whose diet contained 0.001 per cent. fluorine. The bones of the rats on the fluorine-free diet contained extremely small quantities of fluorine; in the teeth it was impossible to find the element. Otherwise there was no definite reason for assuming that these particular tissues were deleteriously affected by the absence of fluorine.”

p 313 “The question of the necessity of fluorine to the organism cannot be regarded as settled finally.”

p 315 “The once general assumption that fluorine is necessary to the quality of the enamel rests upon an insufficient foundation. Our present knowledge most decidedly indicates that fluorine is not necessary to the quality of that tissue, but that on the contrary the enamel organ is electively sensitive to the deleterious effects of fluorine.”