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Manganese Inorganic Compounds Toxicology

Compounds

Manganese compounds used by potters are inorganic , like manganese dioxide, oxide and manganese carbonate.

Uses

Metallic applications account for most manganese consumption, with about 90% used in steelmaking.

Slags coming from old converters, as in the Thomas process in the steel industry, can be used as fertilizers.

Certain welding operations require the use of electrodes whose coating or alloyed core contains manganese.

The chemical industry uses manganese as a catalyst.

Permaganates are powerful oxidizers.

Manganese has other uses

As a coloring material
In the manufacture of dry cells
In the manufacture of pesticides(Maneb)
As food additives for livestock
In the composition of fertilizers
In pharmaceutical products
As siccative for paints
In wood preservatives
In leather processing

Manganese is an essential mineral for humans and animals. It is necessary for normal bone formation. It has been estimated that a normal 70-kg man has a total of 12mg to 20 mg in his body.

Exposure

The inorganic compounds do not penetrate the body via skin like some organic compounds, such as certain tricarbonyls.

Inhalation of dust or fume is the major route of entry in occupational manganese poisonning. Also inhaled large particles are ingested after mucociliary clearance from the lungs.

Gastrointestinal absorption is generally low (5%). Very few poisonings have occured after ingestion.

Acute intoxication

1. Metal fume fever

Inhalation of manganse oxide fumes may cause a flu-like syndrome similar to " metal fume fever ", treatment is symptomatic.

2. Chemical pneumonia

In the case of severe exposure to fumes or dust of various manganese salts, a severe chemical pneumonia may occur.

3. Acute intoxication by ingestion

Acute intoxication by ingestion rarely occurs and is caused by accidental or voluntary ingestion of a manganese salt (as the ingestion of tablets of potassium permaganate), this chemical causes massive burns of the digestive tract, oedema of the upper respiratory tract and circulatory collapse.

Chronic intoxication

The primary target organ of manganese toxicity is the central nervous system, particularly the extra-pyramidal system ; the lungs may also be injuried in the case of chronic exposure to manganese.

1. Central nervous system

Neurological symptoms are caused by inhalation of fumes or dusts of manganese.

The extra-pyramidal system is the main target organ of manganese.

Exposure to heavy concentrations of dusts or fumes for as little as three months may produce the condition, but usually cases develop after 1-3 years of exposure.

In manganese mines where most cases have occurred, the disease has appeared after 10 to 20 years of exposure.

The symptoms may simulate progressive bulbar paralysis, postencephalitic Parkinsonism, multiple sclerosis, amyotrophic lateral sclerosis and progressive lenticular degeneration(Wilson's disease).

The best way to diagnose, at an early stage, manganese intoxication is neurological examination.

A standardized questionnaire of neurological symptoms is helpful.

Here are some symptoms, among others, to be looked for in chronic manganese intoxication

nervousness
irritability
memory loss
tiredness
insomnia
muscle weakness
muscle pain
trembling fingers
stiffness of limbs
difficulty with fine movements
stuttering
hoarse voice
urinary problems
impotence.

At physical examination your doctor should look for signs of an extra-pyramidal syndrome at its beginning.

2. Respiratory tract

Pulmonary tissue does not seem to be the critical target organ of manganese during chronic exposure.

On the other hand, various respiratory symptoms (acute and chronic bronchitis, pneumonia, functional changes of the obstructive type) were observed among workers exposed chronically to manganese at levels higher than those which cause slight neurological disturbances in certain workers.

Reproduction

Manganese could disturb libido according to certain studies. It was demonstrated that a loss of libido and impotence, sometimes preceded by a phase of hypersexuality, was observed among subjects suffering from manganism.

There are contradictory reports as for the effects of manganese on reproduction; however, certain studies showed a reduction in the number of children fathered by male workers during the time when they were exposed to manganese.

In Russia, an excess of spontaneous miscarriages occurred among wives of workers employed in manganese treatment plants.

Teratogenesis

No teratogenic action due to manganese has been described in man.

Mutagenesis and carcinogenesis

The manganese ion has not caused modifications in the DNA among mammals.

In the literature there is no indication suggesting that manganese exerts a cancerogenic action in man. In fact, experimental studies plead rather against such an association.

Exposure

The important thing is your exposure to inorganic manganese, it may vary if you are a pottery factory worker, a teacher, a full-time studio potter or a part-time.

The evaluation of the amount used over a given period of time in clays and glazes is essential in assessing your exposure in a non-parametric way i.e. without the aid of persons specialized in the field of occupational hygiene.

In the wet state, as in moist clays and glazes, these compounds are certainly much less hazardous than as dust.

Pottery factories can financially afford the monitoring of manganese exposure but, it is not the same for artists and craftpersons.

The threshold limit value for dusts of manganese metal and inorganic compounds actually proposed by the ACGIH is 0.2 mg/m3, as total dust.

Prevention

So good house keeping of your studio is very important; to do so you may, among other things, use wet processes, or even a vacuum system whose air is exhausted outside of the workshop.

Avoidance of processes generating unnecessary dust is also importan. To this, we may add work in closed systems and improvement of the general ventilation.

The wearing of an approved dust mask for this kind of hazard is also recommended when the level of exposure seems too high.

Medical surveillance

Often times the only aid to diagnosis is a history of manganese exposure.

1. Pre-employment Medical Examination

It aims at searching for the presence of a neurological and/or pulmonary impairment likely to be worsened by exposure to manganese, and it will be used as reference making it possible to better analyze the results of periodical examinations.

Here are some suggested elements

Complete history taking and physical examination,
Neurological assessment,
Spirometry,
A few psychomotor tests(for instance: evaluation of extremities tremor and reaction (response) time
Blood and urinary manganese measurements.

2. Periodical Examination

Its frequency depends on the severity of exposure and on the legislation in force. It consists in seeking, if possible, with the aid of a well standardized questionnaire, early symptoms of neuropsychological and pulmonary impairment, in repeating the pre-employment examinations and comparing them with the latter in order to detect any risk of excessive impregnation.

It is important to practise this comparison, not only at the individual level but, also at the level of the group of workers.

Urinary manganese levels may be indicative of recent exposures, days to weeks.

Tissue burden and serum concentrations of manganese do not correlate with symptomatology, and symptoms can occurr and progress even after excess metal is cleared from the tissues.

Therefore, serum, whole blood, and urine levels of manganese may be normal in acute or chronic intoxication and cannot be used to predict severity of disease or future progression.

This is contrast with lead encephalopathy.

Among workers, kept away from their job on a temporary basis, and from exposure to manganese dioxide, a good correlation was observed between urinary and blood levels and the index of cumulative exposure, on an individual basis(Lucchini and al.). A correlation was also found between these tests and different neurobehavioral tests.

Tanaka & Lieben however observed a correlation between the urinary excretion and the intensity of exposure, and Japanese authors suggested that manganese excretion higher than 40-50 micrograms/liter corresponds to a level of exposure where lesions can occur (Horiuchi & al.).

3. Synopsis of Laboratory Surveillance

Laboratory and diagnostic testing in manganese toxicity

Laboratory or diagnostic test	Abnormal findings
Urinary levels	>10 mg/L (normal reference, range 0.5 to 9.8 mg/L; up to 50 mg/L for occupational exposure)
Whole blood levels	>19 mg/L (normal reference, range 8.0-18.7 mg/L)
Serum levels	>1.3 mg/L (normal reference, range, 0.3-1.3 mg/L
Electroencephalographic parameters	Low-amplitude, weakened rhythms
Neuropsychiatric testing	Decreased memory, decreased reaction time, decreased motor coordination
CT scan, magnetic resonance imaging	Radiodense accumulations of manganese in affected areas, abnormalities in globus pallidus, caudate nucleus, putamen
Positron emission tomography	Normal fluorodopa scan

Treatment

At the beginning of the intoxication, it seems that a chelation treatment with calcium EDTA may favor an improvement of the clinical picture. At an advanced stage of the intoxication this treatment is ineffective. In this case, the treatment is identical to Parkinson's disease (levodopa).The usefulness of this treatment is however contoversial.

REFERENCES

Occupational Medicine, Carl Zenz, last edition.
Occupational & Environmental Medicine, Joseph LaDou, last edition.
Chemical Hazards of the Workplace, Proctor & Hughes, last edition.
Sax's Dangerous Properties of Industrial Materials, Lewis C, last edition.
Industrial Chemical Exposure, Lauwerys & Hoet, last edition.
Toxicologie Industrielle et Intoxications Professionnelles, Lauwerys Robert,R.1999
Encyclopedie Medico-Chirurgicale- Toxicologie-Pathologie Professionnelle - Paris, Lauwerys R, et Roels H., juin 2001.

By Edouard Bastarache

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