The Beethoven’s deafness and its development are a riddle. In a previous article the authors (Luthe and Bischoff, 2020) suggested poisoning by ultrafine particles through lead corrosion of e.g. organ pipes. In the present article, they propose that Beethoven’s health problems, especially his deafness, were caused by a combination of exposure to lead-containing micro- and nanoparticles. In addition, high alcohol consumption weakened the defense against radical oxidative stress. The authors further hypothesize that the ear is a major portal of entry for nanoparticles, in this case causing lead poisoning of the inner ear. 

 

Beethoven’s deafness:

Consequence of lead poisoning via the nano-auditory route 

submitted Dec-12-2019, accepted Nov-23-2020, published Dec-22-2020

Gregor Luthe1, 2* , Matthias Bischoff 3

1Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, 100 Oakdale Campus, Iowa City, IA 52242, USA

2WindplusSonne GmbH, Fabrikstrasse 3, D-48599 Gronau, Germany

3Luftkurholz B.V., Bultsweg 90, 7532 XJ Enschede, The Netherlands

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* corresponding author

 

Manuscript as PDF:

LUTHE_2020_Beethoven-s_deafness_nano-auditory_route_NANOBAY.pdf

 

Abstract

The Beethoven’s deafness and its development are a riddle. Right after his death his physicians tried to clarify the causal factors via autopsy, without much success. Many facts strongly point to lead poisoning, e.g. high lead levels as indicated by the measurements of his hair. On the other hand, low levels of lead were found in his bones, contradicting the results from the hair samples. Lead poisoning is assumed to have affected many famous artists. While painters inhaled the vapors when using and preparing lead-containing paints, for musicians no connection to their clearly occupation was drawn. Non-specific ways of exposition were proposed, e.g. for Handel and Beethoven wine is suggested as the source. While this would solve the contradicting findings in the hair and bones, it does not explain the deafness. 

In a previous article we suggested poisoning by ultrafine particles through lead corrosion of e.g. organ pipes. The pipes react to exposure to acetic and formic acid from wood. The oxidized lead acetate and oxide particles become air borne by the vibrations of the instruments. In the present article, we propose a causal connection to Beethoven’s deafness. It is known that nanoparticles – a fraction of ultrafine particles – enter the middle ear and brain via the ear as portal. It is also known that nanoparticles of these compounds exhibit a higher toxicity in comparison to bulk material. The toxicity is based on an ionic mechanism and radical oxidative stress. This would complete the picture of the findings, the description of Beethoven’s symptoms and their development over time. The autopsy reported the acoustic nerves to be wrinkled and without medulla, which are typical damages of lead exposure. Nanoparticular lead uptake via the ear pathway alone would not explain why other organists did not show similar effects, while being exposed similarly. We consider Beethoven’s drinking habits to be the necessary second factor, as ethanol reduces drastically the defense mechanism against oxidative stress. The drinking habits in combination with the exposure to ultrafine lead particles with enhanced toxicity could explain his deafness. 

Introduction

We have previously argued that high lead levels in hair and low levels in bones result from micro and nano sized lead particle uptake. We discussed the potential exposure of Beethoven to micro- and nanoparticles of lead compounds, especially, lead oxide, mixed oxides with hydroxides and acetate [1]. The assumed origin of these particles is lead corrosion of organ pipes caused by acetic acid and formic acid originating from wood. More than 10.000 organs in Europe suffer from lead oxidation. Dishes and stained-glass windows can exhibit lead corrosion also [1-7]. This hypothesis could explain the non-regularly distributed high lead levels found in Beethoven’s hair, and also the normal concentrations of lead in his bones. We concluded that micro- and nanoparticles of lead compounds exhibit the potential to enter the hair follicles via the skin. The stem cells embedded in the follicles take up the lead and include it in the hair strain. This pathway of entry concentrated the lead exposure in the follicles while the total amount entering the body is remained small. This explains why the concentration in Beethoven’s bones was not elevated above average compared to people of his time [1]. Against this background, we want to explain the health implications for Beethoven some further. 

It is known that painters suffered from lead poising by occupational exposure. Painters inhaled the vapors when using and preparing lead-containing paints, for musicians no connection to their clearly occupation was drawn. However, for Handel [8] and Beethoven the poisoning was suspected to result from wine. This non-specific way of exposure offers no complete picture though. Painters drank wine as well, and the varying degrees of lead in different wines is a speculative reason for some artists to be afflicted while others exhibited no symptoms. 

In this article we focus on Beethoven’s deafness as a result of micro- and/or nanoparticle exposure of lead compounds like acetate. 

We hypothesize that Beethoven’s health problems, especially his deafness, were caused by a combination of exposure to lead-containing micro- and nanoparticles, and a weakened defense against radical oxidative stress, caused by high alcohol consumption. We further hypothesize that the ear is a major portal of entry for nanoparticles, causing lead poising of the inner ear. 

 

 

Materials and Methods 

An extensive review of the musical and medical literature was initially done. Secondly, the literature describing routes of exposure and of excretion involving micro- and nanoparticles of metal oxides was studied and compared. Thirdly, parallels between Beethoven’s case and historical records of saturnism were identified. Particular, occupational related lead poising was studied. 

 

Results and discussion

Beethoven’s deafness: Symptoms and autopsy results 

It is well known that Beethoven suffered from headache and depression on multiple occasions [9]. It was also noted that Beethoven could not tolerate the sound levels of ninety or even one hundred decibels while playing one of his concertos at the piano with a full orchestra right beside him. This may support the concept of phonophobia due to a central or cerebral cause that had progressed to the peripheral ear [10].

Beethoven showed moderate lead levels in his bones and spikes of higher levels in his hair. This demonstrates that the lead exposure was not due to salve for the skin given by his physicians. Furthermore, recent studies also show that these salves contained ammonium and not lead [11-14]. 

Even at low levels lead exposure can results in a slowly progressing high-frequency loss in hearing [12]. Increasing levels of lead correlate directly with the degree of hearing loss [8]. Findings of Beethoven’s autopsy included wrinkled cochlear nerves that lacked pith [15,16]. The recent retranslation of the autopsy report, which is in Latin originally, states that the acoustic nerves were wrinkled and were without a medulla. This damage to the central portion of the nerve suggests axonal degeneration, that is seen in humans with lead injury. Recent studies have demonstrated abnormal auditory brainstem responses to lead exposure, indicating a neural site of damage [12]. 

In the literature the lead poisoning hypothesis as the cause for Beethoven’s suffering is often opposed on the assumption that over a period of 30 years – parallel to his hearing loss – he would have developed other neurological symptoms such as wrist drop, which were not reported [17]. A remarkable article from Latvia studied 151 workers with inorganic long-term lead exposure over a period of 21,7 years on average. The researchers found similar effects as known for Beethoven namely mood disturbance, abnormal liver and kidney function, and gasturbances. These are typical signs of lower levels of exposure over a long time [18].

Wine as source of lead 

The quest for the source of Beethoven’s lead poisoning has centered on his wine consumption. Beethoven was particularly fond of adulterated or fortified Hungarian wine [19]. He is believed to have started drinking wine at the age of 17, after the death of his mother [19]. His tinnitus began at the age of 27, therefore assuming ten years of heavy drinking, based on housekeeping records [20], which show that the amounts of money spent on wine were far above moderate. Friends and tavern owners related that he was drinking a bottle of wine with each meal [21]. Alcohol dependence is known to have a strong family history, and Beethoven’s family exhibits this [9]. We do not know if Beethoven meets the criteria for continued alcohol abuse as diagnosed today, commonly known as alcoholism. At the autopsy his liver did not show the characteristics of Fatty Liver Disease. In fact, a shrunken, macronodular liver was found [22]. However, in the final stages of alcohol related cirrhosis can produce a shrunken, macronodular liver [23,24]. Wine consumption alone may play a crucial role, but does not sufficiently answer the lead symptoms, especially his deafness. 

Lead induces radical oxidative stress

Lead uptake has various deleterious effects on the hematopoietic, renal, reproductive and central nervous system, mainly through increased oxidative damage [25,26]. Modulations of cellular thiols – glutathione  (GSH) – protect against reactive oxidative stress (ROS). N-acetylcysteine, a-lipoic acid, vitamin E, quercetin and a few herbal extracts show prophylaxis against the majority of lead mediated injury. 

Reactive oxidative stress (ROS) describes the imbalance between free radicals produced and reactive intermediates detoxified by the biological system as a repair system [27]. Three simultaneous pathways are known for the onset of ROS under the effect of lead, namely:

  1. the generation of ROS, such as hyproxides HO2*, singlet oxygen and hydrogen peroxide H2O2
  2. the depletion of antioxidant reserves
  3. inactivation of antioxidant enzymes. 

The antioxidant defense mechanism of the body reacts with the antioxidant GSH and is transformed into GSSG. Further, lead results in ROS – due to its electron sharing capability with enzymes, which are thereby inactivated [28]. These include enzymes important for the ROS defense themselves, such as super oxide dismutase (SOD) and catalase (CAT). Decrease in SOD concentrations reduces the disposal of superoxide radicals, and the reduction of CAT impairs the scavenging of superoxide radicals. In addition, lead replaces zinc ions that serve as co-factors for the antioxidant enzymes. These mechanisms weaken the defense system even further.

Alcohol and its effect on antioxidants 

Glutathione (GSH) plays an important role in the detoxification of ethanol (EtOH) and acute EtOH administration leads to GSH depletion in the liver and other tissues. While little is known about the biochemical mechanisms responsible for the increased sensitivity to EtOH during aging. The depletion of GSH may be involved, considering its important role in the detoxification of EtOH [29-31]. Hepatic GSH levels are depleted six hours after acute EtOH administration in young animals. Further, when GSH levels are depleted prior to ETOH administration, an increase in toxicity is observed. Accordingly, when GSH levels are enhanced by administration of GSH or its precursors, the depletion of GSH levels by EtOH is prevented and toxicity is diminished.

As stated above, GSH depletion is also an important factor in the aging process. Previous studies showed that GSH deficiency is a common phenomenon of senescent organisms, including humans [29-31]. 

Ethanol consumption combined with lead exposure dramatically reduces the defense mechanism against ROS. The same applies to the acute and long-term toxicity of lead. 

 

 

Nanoparticles and the nano-auditory route as portal of entry

Figure 1: The ear is a portal of entry for nanoparticles via the external auditory canal. The connection of ear to inner ear offers an entrance to the most central parts for the particles. Nanoparticles go through the tympanic membrane to enter via the tympanic cavity all other parts of the inner ear and can even delocalize via the vestibular nerve, the cochlear nerve and the blood to the entire body, especially the brain. The particles can be from lead oxide, lead acetate and lead acetate coated solarium dioxide nanoparticles.Figure 1: The ear is a portal of entry for nanoparticles via the external auditory canal. The connection of ear to inner ear offers an entrance to the most central parts for the particles. Nanoparticles go through the tympanic membrane to enter via the tympanic cavity all other parts of the inner ear and can even delocalize via the vestibular nerve, the cochlear nerve and the blood to the entire body, especially the brain. The particles can be from lead oxide, lead acetate and lead acetate coated solarium dioxide nanoparticles.

 

The ear is the part of the auditory system that not only detects sounds but also plays a major role in the sense of balance and body position. The auditory canal, between the outer ear and the inner ear, offers an entrance to the most central parts of the auditory system, see Figure 1. This aspect of the auditory pathway as a channel for nanoparticle transport has found little attention in research, until recently. This may be due to the complex nature of the anatomy of the ear, which contains hollow channels filled with fluid, and sensory cells that are studded with hair cells. Some preliminary reports by Mamedova [33] of the Hough Ear Institute showed that superparamagnetic NPs can be used as a carrier for drug delivery into the inner ear and into the prilymphatic fluid of guinea pigs. Another pilot study also showed that polylactic/glycolic acid (PLGA) polymer coated with iron oxide NPs, can enter the inner ear. When applied to the round window membrane of chinchillas, and induced by a magnetic field, these particles will be found in multiple locations within the cochlea tissue [32-34]. 

 

Ionic mechanism of lead toxicity 

The ionic mechanism of action for lead mainly arises due to its ability to substitute other bivalent cations like Ca2+, Mg2+, Fe2+ and monovalent cations like Na+ (though bivalent cations are more readily substituted), affecting various fundamental biological processes of the body [35]. Significant effects have been found on various fundamental cellular processes like intra- and intercellular signaling, cell adhesion, protein folding and maturation, apoptosis, ionic transportation, enzyme regulation, and the release of neurotransmitters [36]. The ionic mechanism contributes principally to neurological deficits. After replacing calcium ions, lead is able to cross the blood-brain barrier (BBB) at an appreciable rate. Having crossed the BBB, the lead accumulates in astroglial cells (containing lead binding proteins). Toxic effects of lead are more pronounced in the developing nervous system, because immature astroglial cells lack lead binding proteins. Lead easily damages the immature astroglial cells and obstructs the formation of myelin sheath, which in turn compromises the development of the BBB.

Even in picomolar concentrations lead can replace calcium, thereby affecting key neurotransmitters like protein kinase C, which regulates long term neural excitation and memory storage. It also affects the sodium ion concentration, which is responsible for numerous vital biological activities including generation of action potentials in the excitatory tissues for the purpose of cell to cell communication, uptake of neurotransmitters (choline, dopamine and GABA) and regulation of uptake and retention of calcium by synaptosomes. This interaction between lead and sodium seriously impairs the normal functioning of the aforementioned sodium dependent processes [37].

 

Lead containing nanoparticles in the church and orchestra environment

Exposure to lead micro particles can be a result of lead corrosion – called “Bleifrass” in German [1]. Generally, lead becomes grey by oxidation to lead(II)-oxid (PbO) and lead hydroxid (Pb(OH)2). The latter reacts with carbondioxid (CO2) of the air to basic lead(II)-carbonate (Pb(OH)2 . 2 PbCO3). This process protects the metallic lead against further corrosion. In the presence of chloride and sulfur it reacts to PbCl2 (H -359 kJmol-1) and PbS (H -94 kJmol-1) in exergonic reactions [7].  In the presence of acids like phosphoric acid, hydrofluoric acid, hydrochloric acid, sulfuric acid, formic acid and acetic acid the metallic lead forms thin layers of these salts, so called plumbates. Organic acids emitted from the wood of organ cases are corrosive agents for lead-rich pipes [2, 3, 38-41]. Historical organs all over Europe – more than 10.000 have problems with corrosion [42]. There are very severe cases destroying entire organs, e.g. a Stellwagen organ in Lübeck Germany, dating from 1637 [2, 3, 38-41]. When a pipe develops corrosion it gradually develops cracks and holes and finally collapses and there is no way to solve the problem other than replacing the historic pipes with modern ones [7]. The church ambient is characterized by low temperature, relatively high humidity and the presence of large numbers of wooden structures [2, 3, 38-41]. As early as 1778 Watson reported the connection between lead corrosion and volatile acids from oak beams [38]. The windchest in particular contains high amounts of wood. Recent studies from the 2013 COLLAPSE project, entitled “Corrosion of organ pipes - causes and recommendations”, show that acetic acid and formic acid are the main contributors to the corrosion. Measurements demonstrate that values of up to 1437 ppm for acetic acid could be found in the pallet box of the organ in Oegstgeest, The Netherlands [4]. X-ray diffraction (XRD) analyses shows clearly that the pre-dominante crystalline corrosion products are lead white (Pb(CO3)2(OH)2, hydrocerussite), lead formatted hydroxide (Pb(HCOO)OH) and plumbonacrite (Pb10O(OH)6(CO3)6. Particles were also found and a-SiO38]. Surprisingly ion chromatography of metal coupons exposed demonstrated significant high amounts of acetate (74 µg/cm2) and formate (93 µg/cm2) accumulated on the pure lead (Oegstgeest, The Netherlands) [2]. In 2016, Oertel and Richards could identify organic lead crystals [2]. For pipes with a percentage of 2 % tin this is not the case [3]. This explains why not all lead devices exhibit these phenomena. 

With more than 10.000 church organs showing lead corrosion, especially in cold and humid areas like Germany and Austria, it seems reasonable to consider that Beethoven could have been exposed to lead containing micro- and nanoparticles. Moreover, this would explain the peak exposures in Beethoven’s hair. The exposure of Beethoven to the lead micro- and nanoparticles, in particular acetates, was enhanced by playing the organ or playing music in proximity to the pipes. Harpsichords are constructed with leaden key weights, and may be an additional source. In all these cases, the vibrations of the music results in an ablating process of the corroded lead surfaces. The lead salts thus become airborne and are distributed through the air. Hair – with its high surface and fatty layer – is a perfect sponge for collecting airborne micro- and nanoparticles. Human hair grows with different speeds and to different lengths. The rate of hair growth is about 1.25 cm/month, or about 15 cm/year [41].  Considering Beethoven’s hair length of 30-40 cm, the hair on his body at his time of death was exposed to lead for 2 to 3 years before he died. Beethoven spent time in several churches during this period. 

Aside from organ pipes, other exposure sources might be cabinets (285-4600 ppm acetic acid, and 175-850 ppm formic acid [40]), pine wood shelves, oak wood planks (65-379 ppm acetic acid, and 33-270 ppm formic acid), pianos, storage rooms (n.d.-195 ppm acetic acid, and n.d.- 53 ppm). Notably, the starting concentrations in fresh wood are higher than those in old wood. 

 

Increased toxicological effect of nanoparticles and lead co-exposure

Studies from 2016 by Amiri et al. [42] show clearly, that the exposure to lead oxide nanoparticles results in a higher toxicity compared to bulk lead oxide. At nanosize, materials can exhibit unique properties compared to bulk size, this finding is according to current theories.  

Lead levels were highest in the kidney, followed in decreasing order by the levels in the liver, brain and spleen. The concentration of Pb in PbO-NPs exposed rats was higher than in the PbO bulk group. Blood parameters, that are known to indicate an immune response in organ function, were changed in both groups of rats. More recently, in 2017 Lu et al. [43] published the results of focussing on the nature of nanoparticular lead acetate according to cytotoxicity. 

Lu et al. (2017) aimed at the combined cytotoxicity of silica nanoparticles and lead acetate in A549 cells. The primary question was, whether the particles induced mitochondria-dependent apoptosis. This had already been achieved by lead alone. Nano-SiO2 alone resulted in no reduction, but in combination with Pb the effect increased significantly. Synergistic interactions caused this potentiated ROS-triggered apoptosis, as established with factorial analyses. They consider nano-SiO2 to function as transporting carrier for lead, which facilitates accumulation in the cells [43].

Their study therefore investigates the combined cytotoxicity of silica nanoparticles (nano- SiO2, a typical atmospheric ultrafine particle) and lead acetate in A549 cells focusing on mitochondria-dependent apoptosis induction. The results showed that lead exposure alone induced mitochondria-dependent apoptosis in A549 cells, as evidenced by increased apoptotic rate and Bax/Bcl-2 ratio, up-regulated caspases 3 and 9 expressions, as well as decreased mitochondrial membrane potential. Non- cytotoxic concentration of nano-SiO2 exposure alone did not trigger apoptosis in A549 cells, but exponentiated the apoptotic changes under co-exposure to lead. Factorial analyses revealed synergistic interactions were responsible for the potentiation of joint apoptotic responses [43].

 

Figure 2: Mechanism underlying the development of oxidative stress (ROS) and ionic toxicity, in combination resulting in Beethoven’s deafness. The ROS is generated by lead intoxication inside the ear through two factors, the nanoparticular matter and the chemical composition. The ethanol consumption results in a depletion of the defense mechanism against ROS. Both lead to an elevated ROS inside the ear.Figure 2: Mechanism underlying the development of oxidative stress (ROS) and ionic toxicity, in combination resulting in Beethoven’s deafness. The ROS is generated by lead intoxication inside the ear through two factors, the nanoparticular matter and the chemical composition. The ethanol consumption results in a depletion of the defense mechanism against ROS. Both lead to an elevated ROS inside the ear.

 

Conclusions

Based on our previous findings [1] we hypothesize that certain ultrafine lead containing particles were responsible for Beethoven’s deafness. We suggest that Beethoven was exposed to ultrafine particles, including a mixture of various sizes of micro- and nanoparticles of lead-based compounds including lead acetate, lead oxide and lead acetate or oxide coated silica particles. In the literature nano-SiO2 Nanoparticles are reported to have been found on the surface of organs, in addition to lead oxide and acetate. To the best of our knowledge, this is the only hypothesis explaining the high levels of lead in hair compared to normal amounts in deeper layers of the bones. Here we try to understand the special circumstances of Beethoven’s deafness. 

We suggest a multiple factor impact explanation:

  1. Beethoven started drinking heavily at the age of 17. The wine could contain lead and may be responsible for a basis exposure to lead. 
  2. Modulations of cellular thiols – glutathione (GSH) – protect against reactive oxidative stress. His alcohol consumption resulted in GSH depletion in the liver and other tissues. The potential to reduce ROS was impaired. 
  3. Exposure to lead produced various deleterious effects on the hematopoietic, renal, reproductive and central nervous system, mainly through increased oxidative damage. 
  4. The antioxidant reserves were depleted by alcohol and lead exposure simultaneously.
  5. Antioxidant enzymes were inactivated by lead, and recovery from lead poisoning was hindered. 
  6. In his environment lead corrosion resulted in micro and nano lead(II)-oxid (PbO), lead hydroxid (Pb(OH)2), lead(II)-carbonate (Pb(OH)2.2 PbCO3) and lead acetate (Pb(OAc)2) entering via the auditorial route and depositing inside the ear. 
  7. Nano sized particles result in a higher ROS and enhanced toxicity. Smaller particles have a higher surface and a higher solubility, resulting in a stronger ionic toxic mechanism. 
  8. The ionic mechanism contributed principally to the neurological deficits, as lead, after replacing calcium ions, is able to cross the blood-brain barrier (BBB) at an appreciable rate. After crossing the BBB, lead accumulates in astroglial cells.

In our opinion, this big set of factors for saturnism – mainly by micro- and nano sized lead containing matter in combination with a weakened ROS defense system by alcohol consumption – is the key to the understanding of the Beethoven’s deafness. Currently, we are investigating the influence of acoustic waves on the formation of ultrafine particles composed of lead salt. 

 

Acknowledgements

We would like to thank Megan and Hein van Gills for correction of the manuscript. Larry Robertson and Gabriele Ludewig, my warm Humboldt hosts I wish to thank for their excellent training in toxicology. The Rotary Euregio Club Gronau I thank for stimulating discussion around the saturnism during a visit paid at the Beethoven house in Bonn. My friends made me aware of this scientific riddle. We would like to thank the Saxion University of Applied Sciences and the Tech For Future fund, an initiative of the Saxion and Windesheim Universities of Applied Sciences and the regional government of Overijssel, The Netherlands for friendly support.

 

Literature

[1] G. Luthe, M. Bischoff, Beethoven’s saturnism conundrum solved: High lead levels in hair and low levels in bones result from micro and nano sized lead particle uptake, Nanobay.com, 2020.

[2] C. M. Oertel and A. Richards, Music and materials: Art and science of organ pipe metal. MRS Bulletin, Volume 2, January 2017, 55-61.

[3] C. Chiavari, C. Martini, G. Poli, d. Prandstraller. Conservation of organ pipes: protetive treatments of lead exposure to acetic acid vapours. 2004, 4-5 October, Proceedings of Metal.

[4] A. Niklasson. S. Langer, K. Arrhenius, L. Rosell, C.J. Bergsten, L.G. Johansson, J.E. Svensson. Air Pollutant concentrations and Atmospheric Corrosion of Organ Pipes in European Church Environments. Studies in convervation 53, 2008, 24-40.

[5] J. Speerstra, Ed., The Noth German Organ Research Projekt at Göteborg University (GOArt Publications, Göteborg, Sweden, 2003.

[6] Watson, R., Chemical Essay, Volume II, 4th edn. T. Evans, London 1789.

[7] EC Fifth Framework Programme:
Energy, Environment and Sustainable Development
EVK4-CT-2002-00088 COLLAPSE
Corrosion of Lead and Lead-Tin Alloys of Organ Pipes in Europe
Duration: 2003 – 2006. http://goart.gu.se/collapse/

[8] Frosch, W.A., 1989. The Case of George Friederich Handel. N.Engl. J.Med. 321, 765-769.

[9] Mai, F.M., 2006. Beethovens terminal illness and death, J.R. Coll. Physicans Edinb. 36(3), 258-263.

[10] Progress in Brain Research, Volume 203, Juio Montes Santiago, 223, The lead-poisoned genius: Saturnism in famous artist across five centuries.

[11] The Beethoven Journal, Volume 23, Number 1 (Summer 2008) pp 5-17, Was Beethoven lead poisoned?, Josef Eisinger.

[12] Michael, H. Stevens, Teemarie Jacobson, Alicia Kay Crofts, Lead and the Deafness of Ludwig van Veethoven, The Laryngoscope, 2103, 123:  2854-2858.

[13] Lorenz, M. "Commentary on Wawruch's Report: Biographies of Andreas Wawruch and Johann Seibert, Schindler's Responses to Wawruch's Report, and Beethoven's Medical Condition and Alcohol Consumption." The Beethoven Journal. 1 Jan. 2007, Volume 22, Number 2: 92-100.

[14] “Beethoven May Not Have Died of Lead Poisoning, After All" by James Barron, The New York Times, 28 May 2010.

[15] D.A. Otto, D.A. Fox, Auditory and Visual Dysfunction following lead exposure, Neurotoxicol 1993, 14, 191-207.

[16] Buchanan, L.H., Contuer, S.A., Ortega F., Laurell G., Distortion product of acoustic emissions in Andean children and adults with chronic lead intoxication. Acta Otolaryngol 1999, 119: 652-658.

[17] Thomason, R.m., Parry, G.J. Neuropathies associated with excessive exposure to lead. Muscle nerve 2006, 33, 732-741.

[18]      Reubens O, Logina, I, Kravale, I., Eglite M., Donaghy, M. Peripheral neuropathy in chrionic occupational inorganic lead exposure, a clinical and electrophysiological study. J. Neurol Neurosug Psychiatry 2001, 71-200-204.

[19] PJ Davies, The Character of a Genius. Westport, CT, Greenwood Press, 2002, 12, 100.

[20] Anderson, E. The letters of Beethoven. New York, NY. St. Martins Press, 1961, 1,60.

[21] Thayer, a.W. Life of Beethoven, Forbes E., ed. Prionceton NJ, Princeton University Press 1967, 135.

[22] Brancatelli, FG, Ambrosinin R. Cirrhosis, CT and MR imaging evaluation. Europ J. Radiol 2007, 61, 57-69.

[23] Bader, TR, Beavers KL, Semelka RC, MR imaging features of primary sclerosis cholangitis, patterns of cirrhosis in relationship to clinical severity of disease. Radiology 2003, 226, 675-685.

[24] Hunter D. Miraculous recory? Handels illness, the narrative tradition of heroic strength and the oratio turn. Eighteenth- Century Music 2006, 3, 253-267.

[25] Flora SJS, 2002 Nutritional components modify metal absorption, toxic response and chelation therapty, J. Nut Environ Med 12, 53-67.

[26] Flora SJS, Pachauri V., Saena G. 2011, Arsenic, cadmium and lead, Reproductive and Developmental Toxicology, Academic Press 415-438.

[27] G. Flora, D. Gupta, A. Tiwiari, Toxicity of lead: A review with recent updates. Interdiscip Toxicol. 2012, Vol 5(2) 47-58.

[28] Flora SJS, Saxena g., Metha A. 2007. Reversal of lead-induced neuronal apoptosis by chelation treatment in rats, role of reactive oxygen species and intracellular Ca2+, J. Pharmacol Exp Ther 322, 108-116.

[29] Adachi, M., and Ishii, H. Role of mitochondria in alcoholic liver injury. Free Radical Biology & Medicine 32:487–491, 2002.

[30] Bailey, S.M., and Cunningham, C.C. Contribution of mitochondria to oxidative stress associated with alcoholic liver disease. Free Radical Biology & Medicine 32:11–16, 2002.

[31] Bondy, S.C. Ethanol toxicity and oxidative stress. Toxicology Letter 63:231–242, 1992.

[32] C.s. Yah, g.S. Simate, s.e.Lyuk, Nanoparticles toxicity and their routes of exposures, Pakistan Journal of pharmaceutical sciences, 25(2), 477-91, 2012.

[33] Memdova, n., Dormer, K., Kopke, R., Chen, K., Liu J., Ronald J., Costello M. Gibson D and Mondalek F, 2005, Feasibility of superparamagnetic NPs for drug delivery to the inner ear.

[34] Barnes AL, Wassel RA, Mondale F., chen, K., Dormer KL and Kopke RD (2007). Magnetic characterization of superparamagnetic nanoparticles pulled thourough model membranes. Biomag. Res Technol, 5, 1 .

[35] Lidsky TL, Schneider JS, 2003. Lead neurotoxicity in children: basic mechanisms and clinical correlates, Brain 126:5-19.

[36] Garza A., Vega R., Soto E. 2006. Cellular mechanisms of lead neutrotoxicity. Med. Sci Monit 12, RA57-65.

[37] Bressler J., Kim KA, Chakroborti T., Goldstein G. 1999, Moleuclar mechanisms of lead neurotoxicology. Neurochem. Res. 24, 595-600.

[38] Gibson, L.T. Cooksey, b.g., Littlejohn, D. and Tennent, N.H.. A diffusion tuber samples for the determination of acetic and formic acid vapours in muesium cabinets. Analytica Chmimica Acta 341, 1997, 11-19.

[39]  Rhyl-Svendsen, M., Glastrup., J., Acetic acid and formic acid concentrations in the museum environment measured by SPME-GC/MS, Atmospheric Environment 36, 2002, 3909.

[40] Godoi, A. F.L., van Vaeck, L. and van Grieken, R. Uso for soid-phase micro extraction for the detection of acetic acid by iontrap gas chromatography – mass spectrometry and application of indoor levels in museums, Journal of Chromatograph A, 1067, 2005, 331-336.

[41] A. Patzelt, H. Richter, F. Knorr, U. Schaefer, C.M. Lehr, L. Dahne et al.. Selective follicular targeting by modification of the particle sizes. J. Control. Release 150(1), 45-48 (2011).

[42] Amiri A, Mohammadi M, Shabani M, Synthesis and Toxicity Evaluation of Lead Oxide (PbO) Nanoparticles in Rats. Electronic J Biol, 12:2, 2016.

[43] C.F. Lu, L.Z. Li, W. Zhou, J. Zao, Y.M. Wang, S.Q. Peng, Silica nanoparticles and lead acetate co-exposure triggered synergistic cytotoxicity in A549 cells through potentiation of mitochondria-dependent apoptosis induction, Environmental Toxicologoby and Pharmacology 52, 2017, 114-120.