Lead poisoning and lead absorption

by Sir Thomas Morison Legge; Kenneth Weldon Goadby

Persistent headache is an exceedingly grave feature, and although it may at times disappear quickly on treatment, mental clouding and alteration of the higher functions is always to be feared; not infrequently persistent headache ushers in a final and fatal encephalopathy. In such a case the headache persists, becomes more and more excruciating, the patient rapidly shows loss of mental power, and may gradually sink into a condition of delirium. On the other hand, an attack of acute delirium may suddenly supervene, commencing with sudden loss of consciousness, followed by irregular movements of all the limbs, frothing at the mouth and nose, and finally mania. Recovery is by no means uncommon, and after a sudden attack of this description the patients are entirely ignorant of the whole circumstance; they may occasionally recover powers of locomotion, and wander to long distances, unable to give an account of themselves or to remember their names, and only after a considerable time recover consciousness of their identity; but this type of case is comparatively rare.

The case quoted by Mott[10] gives a typical history of mental affection due, no doubt, to lead, but partially complicated by alcohol.

The Burtonian Line.

—Much controversy has raged around the significance of the blue line on the gums to be seen in certain persons working in lead, as to whether this particularly well-marked sign is to be regarded as a diagnostic symptom of lead poisoning or not.

For a long time it was regarded, and by many is still regarded, as sufficient evidence in itself to determine that a person is suffering from lead poisoning. On the other hand, those who have had considerable experience of industrial lead poisoning, particularly in the routine examination of workmen occupied in various lead industries, do not regard the occurrence of the Burtonian line as of more value than that the person showing such pigmented gums has been exposed to lead absorption.

There are two kinds of Burtonian line:

1. A fine bluish line is seen around the gingival margins, more pronounced on the interdental papillæ of the gum, and always more marked around such teeth as are coated with a deposit of tartar than around teeth which are clean. This line is undoubtedly due to the decomposition of the lead salts which have gained access to the mouth, by the sulphuretted hydrogen produced by the decomposition and putrefaction of food, epithelial débris, and other materials, which have accumulated around the edges of the teeth and in the interdental spaces. Peculiar evidence of this may often be seen in the mouths of certain persons whose parotid glands are discharging saliva which promotes deposits of calculus. Thus, one may often find merely the two first upper molar teeth on both sides of the upper jaw coated with tartar, no other teeth in the upper jaw being similarly affected. This deposit of calcium phosphate and carbonate is exceedingly porous, and becomes saturated with the products of decomposition, evolving sulphuretted hydrogen in fairly large quantities. In the mouths of such persons working in lead factories a dark bluish staining of the cheek in apposition to the filthy tooth may be frequently seen, and where the rest of the teeth are free from deposit no such staining is observable. Viewed with a hand-lens, the blue line is seen to be made up of a large number of minute granules of dark colour which are deposited, often deeply, in the tissue. It is a matter of importance to note that a blue line is rarely seen in the mouths of those persons who pay attention to dental hygiene; where the teeth are clean, the gums closely adherent to the teeth, and entire absence of pus and freedom from deposit we have never seen a Burtonian line produced. Many of the so-called healthy mouths with perfect teeth have yet infected gums.

On examining sections of such a line, it is interesting to note that at first sight the particles appear to be situated deeply in the tissue, and mainly in relation to the bloodvessels supplying the gum. A little closer attention shows that the particles are really aggregated, particularly in the deficiencies between the epithelial cells which are constantly thrown off from the surface of the gum, a process which has its origin in an inflammatory condition, the whole gum becoming hypertrophied, with numerous small areas of ulceration. In these positions a certain amount of direct absorption of dust and fine particles takes place from the ulcerated surface, and becomes converted into lead sulphide by the sulphuretted hydrogen produced locally from the decomposing tissue. A certain amount of pigmentation is also referable to the mucous glands. It is well known that, in infections of the mouth of the type of pyorrhœa alveolaris or of rarefaction of the alveolar process, a good deal of infection coexists in the mucous glands of the buccal membrane, especially along the gum margins themselves, and the lead dust also becomes deposited in these glands, and later forms a sulphide. It is possible that some blue lines are due to excretion of lead from the blood.

Some little care is required to differentiate between the early lead Burtonian line and the curious bluish-grey appearance of the gum edges in cases of pyorrhœa alveolaris; when once the two conditions have been studied, little difficulty exists, but the use of a hand-lens will at once settle the matter. The bluish appearance of the gum in many cases of gum disease is due to local cyanosis. A few other forms of pigmentation of the gum edges exist, such as an occasional blue line seen in workers with mercury, a black line in coal-miners, and so on, but these hardly call for discussion in the present instance. Any pigmentation of the nature discussed above is to be regarded as a sign that the worker has been subjected to the inhalation of lead dust, and is therefore suspect of lead absorption, in whom definite symptoms of lead poisoning may be expected to occur if the exposure to the harmful influence be long-continued.

2. In the second variety of blue line the pigmentation is not confined to the gum edge or to a band rarely exceeding a millimetre in width, as is the ordinary common blue line. In this case the whole of the gingival mucous membrane from the edges of the teeth, and extending some way into the buccal sulcus, five or six millimetres or even a centimetre wide, may be seen.