Symptomatology and Diagnosis (Continued)—Excretion of Lead.
—The two chief channels for excretion of lead are the urine and the fæces, while some include the saliva and the sweat.
In the case of the sweat there is not much evidence, but a few observers, mainly French, claim to have discovered traces of lead in the skin of lead-workers. In such a case, however, it is exceedingly difficult to eliminate the question of surface contamination; and although brisk peripheral circulation and transudation may possibly carry off a certain amount of lead, the chance of this is highly improbable.
There seems rather more evidence that the salivary glands may eliminate lead, as a number of other substances are undoubtedly passed in this way. Mercury certainly undergoes excretion through the salivary glands and the mucous glands of the mouth, and it is therefore not improbable that a metal so closely related in its chemical, and perhaps physiological, relations may be excreted in a similar fashion. Meillère[1] cites three instances of parotitis which were considered to be of lead origin, and further quotes an instance where, in chemical examination of the salivary glands after death, lead was found in small quantities.
Chronic parotitis is not infrequently cited as a symptom in cases of reported industrial lead poisoning, and may owe its origin to impairment of the salivary gland by the passage of the metal. Chronic parotitis, or even tenderness of the parotid glands, does not occur frequently among lead-workers with symptoms of lead absorption. Excretion, however, of lead through the salivary glands is not of great importance, except from the occasional complaint of a metallic taste in the mouth in chronic lead poisoning, and in such instances possibly definite excretion of lead is taking place through the parotid glands. A case may be cited which rather supports the view that lead may be excreted through the salivary glands. A certain worker engaged in a dangerous lead process from time to time, but never as a constant symptom, showed distinct pigmentation in the internal surfaces of both cheeks in the region of the buccal papillæ of the parotid duct. The pigmentation was intermittent; at times a large patch of deep blue-black pigmentation was found in the situation on both sides, with no staining of the cheeks around or of the gum margins, although his teeth in these regions were coated with foul tartar. If the lead in this instance gained access through the mouth, why should it have been deposited merely upon the cheek in this one situation, despite the fact that several other situations in the mouth exhibited the same conditions of bacterial decomposition for the production of sulphuretted hydrogen? We have not observed this pigmentation in the neighbourhood of the ducts of the submaxillary and sublingual glands, but only in the parotid.
By far the most important organ in the excretion of lead, from the point of view of symptomatology and diagnosis, is the kidney. Lead is not uncommonly found in the urine of lead-workers and in the urine of those suffering from lead poisoning. The quantity present is usually small and in a form in which it is exceedingly difficult to detect. Yet very pronounced changes in the kidneys may take place, with little evidence in the urine itself that pathological changes are taking place.
The urine of workers in lead factories is frequently high-coloured; in fact, as a general rule the degree of pigmentation is greater than is normal, and in those persons who show some degree of icterus, with the curious yellowish-brown colour of the conjunctivæ, hæmatoporphyrin may be detected on applying suitable tests.
In well-established cases of chronic poisoning, albuminuria as a rule is found, together with certain alterations in the other constituents of the urine, such alteration frequently making its appearance before the definite onset of albuminuria. Further, the changes in the eye, referred to under a special heading, have been frequently described as albuminuric retinitis of lead origin, it being true that eye changes are often associated with chronic changes in the kidney.
In acute poisoning lead is generally found in the urine, but in chronic poisoning it is by no means a common occurrence. From time to time small quantities are excreted, and in the chemical analysis made of the kidneys in cases of fatal lead poisoning a certain amount of lead has frequently been noted. Wynter Blyth[2] found in the kidneys of two white lead workers a total of 0·003 gramme. Peyrusson and Pillault[3], quoted by Meillère, found a similar quantity, 0·003 gramme, while in experimental animals Meillère himself found considerably less, only 0·0001 gramme; Stevenson, in a case reported by Newton Pitt[4], 0·0086 per cent. of lead in the cæcum and colon. Notwithstanding a small quantity of lead which may be determined by chemical methods as present in the urine or the kidney, very definite nephritis is set up in these organs, obviously due to the irritative effect of the metallic poison.