Document Rp7X8Ek7qevGb8m0qjg5wvQka

ijer, 10J, 9 nalities from resented each y maintained t through to it was found favorably imnd its results, eir own meals the value of ts and ahsenant for some volved in this e worker is no ition program exhibit placed nonthly. This ion in the emisses the value straeted favortrough articles ; its aims, obid the project 3 of industry's served, too, to is more closely : great inagniye feel that it complished. i > | I | j | j Solubility and the Relative Toxicity of Lead Chromate II G. C. HARROLD, Ph. D, -- S. F. MEEK, M.D., Industrial Health, Hygiene and Safety Service, Detroit, Michigan IN A PREVIOUS study,1 we provided evidence that but some values were obtained every two weeks lead chroinate inhaled or ingested by human from different individuals. The individual differ subjects did not exhibit clinical or laboratory ences which did appear were not important to findings indicative of lead absorption after ex- the general average over a long period of time.. posure to quantities of lead chromate greatly in The actual exposure time of no worker was re excess of those regarded as safe for continuous duced for more than two weeks over the total exposure. That study involving two groups of exposure time by the wearing of test equipment. 145 men and 4Q men for 16 months was extended to 28 months for 20 men who were still exposed Efficiency of Packed Tube Collector to high concentrations based on an exposure day. 'jpHE efficiency of the "packed tube collector"1 We will, in this report, extend the observations was cheeked at 28 and 40 liters airflow per to 40 months for 26 men. The information is minute using an electrical precipitator in a series. evaluated in terms of the solubility relations of Three determinations averaged 99.7% relative lead salts in human lung fluids,2 efficiency at 28 liters per minute, and three deter I. Exposure to PbCrO* minations at 40 liters airflow averaged 99.8% relative efficiency. The lead test material was TN OUR previous report on the toxicity of lead sprayed lead chromate in concentrations of 120 1 chromate,-1 we evaluated the actual exposure to 150 milligrams of lead chromate per 10 cubic of two groups totaling 185 men to amounts of meters of air as determined by the electrical lead in the form of lead chromate, never less precipitator. than 4.0 mg. of PbCrOi per exposure day for 18 months, and to over 18 mg. PbCrO^ per exposure Air Lead Concentrations per Ten Cubic Meters day for from 12 to 15 months, with no clinical TJTOw ev er , the concentrations that this group of or laboratory symptoms of lead absorption. From 26 men were exposed to based on the amounts the above group, 26 men were selected on the of lead chromate per 10 cubic meters of air using basis of continuous exposure to the highest con the electrical precipitator and tile midget im- centrations of lead chromate. They had exposure pinger as sampling equipment were much higher. days averaging 6.2 mg. of Pb chromate for 27 The averages comprise 328 individual air tests additional months. The reports showed no lab for the first 13-month period, and 628 separate oratory or clinical results differing from the nor air determinations for the 27-month period. For mal. 13 months, the exposure average was 117.1 mg. This group of 26 men had exposure days of of lead chromate for 10 cubic meters of air. For over 18.8 mg. lead chromate per day for 18 the following 27 months, the average was 41.3 months, and to 6.2 mg. lead chromate per day mg. of lead chromate per 10 cubic meters of air. for 27 additional months. The highest exposure The lowest values found in one area where two of day was 12.2 mg. and the lowest was 2.6 mg. the men were working averaged 12.1 mg, of lead in this 27-month period. The men on the job chromate per 10 cubic meters of air for the last cooperated by wearing the test collecting devices. six months* exposure period. At the end of 40 months, the group Basophilic An outside agency checking one of the work Aggregation was .7 and the lead-in-urine aver places where some of these 26 men had worked age .039 mg. per liter, Again, no clinical or for over 15 months reported lead-in-air values laboratory results deviating from the normal of 74, 105, 118 and 121 mg. of lead per 10 cubic were found. meters of air using the electrical precipitator The above extension of the test results of as the collecting instrument. the group, whose onTy selection was on a basis of Since such methods of standards reporting, continuous exposure to high quantities of lead based on the air content of contaminant per 10 chromate, indicates that over long periods of cubic meters of air, are commonly employed, it time, such exposure does not cause demonstrable can be seen that some explanation is required as ill effects. it is determinable that lead absorption of lead In view of Silverman and Drinker's21 questions compounds such as lead oxide, when reported in about physiological breathing rates, our last re much smaller concentrations, has caused lead sults for a period of 15 months with this group absorption. of 26 men were derived mainly from the exposure Thus, our correlations4 between lead-in-urine days of the men on the job. All the men cooper and Basophilic Aggregation were good when lead ated to some extent, and no significant deviations oxide was involved. Furthermore, our first lead were noted from those results which had pre chromate report1 cites the excellent agreement viously been extended from a limited number between Basophilic Aggregation, lead-in-urine, of men. These tests were not taken every day, and lead content of the air when coarse lead oxide N40757 Page U08 INDUSTRIAL MEDICINE AND SURGERY October. 19M9 is involved. We have additional information sup porting this point. Two hundred and one (201) men exposed to concentrations of lead-in-air averaging 1.24 mg. of lead per 10 cubic meters had a Basophilic Aggregation average of .9, and the lead-in-urine average was .081 mg. per liter of urine. Other investigators5^ have somewhat similar data which refer in the main to soluble lead com pounds--compounds readily soluble in bodily fluids. We have found that when lead chromate1 was involved, this correlation was not evident. There is a correlation between the Basophilic Aggrega tion and the lead-in-urine, but none with the amounts of lead-in-air. Hypothesis QiJR WORK2 on the solubility of lead salts in human pleural fluid shows that lead oxide and lead carbonate are much more readily soluble in human lung fluid than lead chromate and lead titanate. This fact, when isolated from the actual concentrations, is only important in that it allows a prediction that the more soluble salt will prob ably cause signs of lead absorption to appear more rapidly than in the case of the Jess soluble salts. However, we believe the quantitatiye evaluation of the amounts of impure lead chromate in human pleural fluid2 indicates a possible explanation of the lack of harm due to very large quantities of inhaled lead chromate* It has been suggested that the synthetic coating on the lead chromate paint would prevent the dissolving of the lead compound in the human organism, but this is not a noticeable deterrent to lead intoxication when paints containing lead oxide, lead sulphate, or even lead carbonate are sprayed. Furthermore, we did not use a coated lead chromate in our solubility determination. These quantities had not been reported in the literature for the solubility of the lead oxide, lead carbonate, lead chromate, and lead titanate in human pleural fluid or blood serum prior to our recent paper.2 We are now suggesting a possible explanation which has been offered freely in the past based on generalized information or belief. We now have scientific data to substan tiate these beliefs. We propose an explanation based on the ex tremely low solubility of lead chromate in human pleural fluid and blood serum. The amounts found soluble in one liter of these fluids range from 1.28 mg. PbCr04 in pleural fluid to 1.14 mg. PbCr04 in blood serum. Since the total amount of tissue fluid which could act as an exchange medium between the lung and the blood is lim ited, a saturation of this limited quantity of fluid would provide total quantities of lead ion less than 1.0 mg. This quantity of lead is subject to a continuous unbalanced equilibrium with the blood, and finally with the kidney and the excre tory product, the urine. The maintenance of saturation of these fluids would require, accord* ing to the laws of mass action, very large quan tities of the less soluble lead chromate in the lung. When it is considered that usually, but not always, no clinical symptoms are observed when .2 to ,8 mg. of lead are found in a liter of the urine and amounts of .05 to ,1 mg, of lead per 100 grams of whole blood, the possibilities of getting even .5 of a milligram of lead in the body fluids from a quantity of lead chromate of 1,0 mg. per liter of body fluid concentration is re mote in even exceptional industrial exposures. This information may appear more significant if we point out that ,05 mg. to .1 mg. of lead per 100 grams of whole blood is close to .5 to 1.0 mg. of lead per liter of blood. We, therefore, are comparing .2 to .3 mg. lead in the excretory pro duct, the urine, to .5 to 1. mg. of blood lead in the same volumes of fluids to a compound which dissolves in blood serum in the range of 1.14 mg, per liter. Actually, our measurements of 26 men ex* posed to at least 6.2 mg. of lead chromate for over 40 months, and for a large portion of the time to from 15 to 20 mg. per day, showed that this saturation was not only not reached, but that the lead-in-urine and Basophilic Aggrega tion dropped to normal during a period of time when the exposure day indicated an inhalation of 6.2 mg. of lead chromate. Furthermore, for 13 months of exposure to over 18 milligrams of lead chromate, no significant deviations were noted from the results observed at the end of one month's exposure. Based on these observations, we suggest that the insoluble lead salts which prove to have solu bilities in the range of 1 milligram or less in human lung fluid at about 37 C will not he likely to be causative of lead intoxication from inhal ation in quantities of less than 20 milligrams of insoluble lead compound per 10 cubic meters of air. We do not propose this as a standard of the M.A.C. variety, but we do suggest that it is a fact based on scientific observation. It is our observation that even this figure may be extended considerably if more insoluble lead salts are considered. Thus, with purified lead titanate where the solubility is about .28 mg. PbTi03 per liter of blood serum, we may be approaching a range where a true equilibrium exists between the amounts of lead absorbable through inhalation and the amounts excreted without harm to the human organism. This.re> lation would not obtain with impure lead titanate containing lead salts readily soluble in body fluids. It is believed that any lead intoxications which may occur in a lead salt of this level of solubility would be due to the admixture, or formation, of a more soluble lead compound. Solubility, Particle Size and Excretory Rates Au r s t u d y of workers exposed to lead chromate1 ' has led to the question as to whether or not somewhat higher levels of urinary excretion than that of the general population can be maintained without the demonstration of clinical symptoms. ; -v: ' -.i *&*?"$* *** DUP050058694 obeys l `> urge qu.5>. . alt* in th. sually, h.;r e obsorv^ : j a lil r : IK. f \r;\,\ dbllitScs ,>f n the l*o.b late of "j.n tion is iv WMlVdii. sign ilka::? i. of kw* lo .5 to J..o refore, ai* etory ]u<>od lead is; und v. hii ji *f U-l mr men ex ornate for ion of th* lowed that iched, luit Aggivyik ! of time inhabit iv*;: ore, for 3 3 igrams of ions were end of one rgest .1 hathave so!u* or loss in t be likely om inhali grams of meters .of uulard < f that it L igure in;/* luble le.ol Hied lea l t .2s t o w . * may U luilibrhi:?ibsorlv^ V exer<* This t><1 ti*. dy fiui.Sns v.h:*'b solubility orma'.i? ates .or .or iv * '! *.? ?' r;i j-*/ *t * ?: - V0b. 18, No. 10 INDUSTRIAL MEDICINE ARP SURGERY Page 409 In the cases of over iOO men exposed to large sures which are likely to be encountered. This quantities of lead chromate, the urinary lead conclusion is based almost entirely on the solu excretory rate rose to .1 mg. per liter of urine bility characteristics of this compound. In those ;md remained above .06 mg. per liter of urine instances where the amounts of lead compounds for 18 months with no demonstrable damage. which can be dissolved in body fluids, are equal Certainly there must be some regulatory mech * to, or less than, the) amounts which are trans anism to adapt the organism to changed condi ported and eliminated without harm to the or tions. In a previous study,4 we were able to ganism, the potential saturation limit is the im show that the average individual in an industrial portant factor. The factor of solubility, in this environment, exposed to more lead than the nor instance, is independent of particle size and, per ma! population, did have a somewhat higher lead haps, of other possible influencing factors, where excretory rate of .05 mg. per liter of urine than as lead compounds soluble to a great degree in had been reported for the general population.7 body fluids are dependent on particle size, both in This indication has been supported by Dreessen8 regard to the rate of solution and other factors in his study on lead storage battery workers not such as the transport of extremely fine particles exposed industrially to lead, whose urine con in protecting envelopes. tained .06 mg. of lead per liter. That this rate is in equilibrium with the ex References posure is shown by the return to completely nor ma! industrial levels, both for lead-in-urine and for Basophilic Aggregation test, even though 1. Ha k r q u >, G, C., Me e k , S. F., Co l l in s , G. R., and Ma r k e l l , T. F.: Toxicity of Lead Chromate. J. Ind. Hyg. & Tox., 26: 47, 1044. 2. Har r o l d , G. C.: Solubility of Lead Salts in Human Pleura) exposed to over 6 mg. of lead chromate when in the air of the work place, apd over a longer period of time, the lead-in-urine concentration and Basophilic Aggregation percentage approach the normal values given for the genera] population. Fluid and Blood Serum. To be published in J. hid. Hyg. & Tox. Presented Am. Ind. Hyg. meeting, April, 1049. 3. Sil v e r ma n , L. and Dr in k e r , P.: Use of the Exposed Worker as an Air Sampling Unit for Contaminants. J. hid. Hyg. & Tox., 27:22, 1045. 4. Me e k , S. F., Co l l in s , G. R., and Har r o l p, G. C.: Correla tion Coefficient between basophilic Aggregation Test and Lead- in-Urine, J. Ind. Hyg. <& Tox,, 22:401, 1940. Summary and Conclusion 5. El k in s , H. B., Eg b, S. F., and Ku o t o l o , B. P.: Evaluation of Lead Hazard. ,7. Ind. Hyg. & Tox., 23:256, 1941. v o t e Do NOT conclude that lead chromate cannot cause lead poisoning under certain condi tions, but the evidence we have presented makes 6. Smu c k er , C. H., and Kis t l e r , J. B.: The Evaluation of the Lead Hazard In the Decorating Department of a Glass Plant. J. hid. Hyg. & Tox., 24:1, 1942. 7. Ke k o e, R. A., Th a k a n n , F,, and Ch l o a k , J.: Normal Ab the appearance of lead intoxication from this source highly improbable in the industrial expo sorption and Excretion of Lead. jjl.M.A., 104:90-92, 1935. 3. Dr ees een , W. C.: Health of Lead Exposed Storage Battery Workers. J, Ind. Hyg. Tox., 25:67, 1943. *1 Is The Nurse____ * A s ic k workman is a piece of humanity broken into bits. The physician picks up one to study it under his stethoscope, the bacteriologist wants another for his microscope, the psychol ogist a third one and so on. And each of them brings his own particular knowledge to bear on the particular bit, and draws particular inferences from it, sometimes right, sometimes wrong. But in the end it is the nurse who gathers up the various bits and reconstructs a whole from them with the virtue of her mother hood and the alchemy of her smilfe. While scientists keep busy sharpening their intellects in this or that particular direction the nurse enlarges her heart to include in it the whole of humanity. mc g r at h has said in her book "Nursing in Commerce and Indus try" that industry needs a superior nurse. It is better if she had used the word religious in place of superior, for only such a nurse as lives religion in her life can be a superior one. --From "Industrial Medicine: Its Religious Aspect," by H. P. Pa s t u k ., Medi cal Officer, Industrial Medical Department, Tata Industries, Ltd., Bombay. in J. Indian Med. A., 18:3, 2T9-281, May. 1940. DUP050058695