Manganese Toxicity and Its Health Effects

Introduction

Manganese is a transition element often found in minerals. They are used in multiple industrial processes, including stainless steel production, rubber additives, glass fillers, ceramics, and fertilizer production. In addition to these industrial applications, manganese plays a vital role in the human body. They are essential dietary elements important in bone formation, macronutrient metabolism, and free radical defense mechanisms.

Manganese toxicity occurs due to acute exposure to high doses of the element or chronic exposure to large quantities of the element. James Couper first identified magnesium toxicity and its adverse effects in 1837. Neurotoxicity is the most critical effect associated with manganese exposure. Environmental or occupational exposure to more significant levels of manganese (Mn) leads to the development of magnesium, which is a neurological condition with motor symptoms similar to Parkinson's disease (PD).

What Is Manganese?

Manganese (Mn) is a brittle, hard metal found in minerals. In trace amounts, they are present in the liver, bones, pancreas, and kidney. Manganese is essential for the normal functioning of nerves and the brain.

Other functions associated with manganese are the following.

• Helps in the formation of bones, connective tissue, sex hormones, and clotting factors.

• Helps in calcium absorption.

• Regulates blood sugar levels.

• Regulate immune functions.

• Hemostatic function.

• Carbohydrate and fat metabolism.

• Regulates antioxidant function (superoxide dismutase).

• Macronutrient metabolism.

• Function as a coenzyme in biological processes.

What Is Manganese Toxicity?

Manganese toxicity (manganism) occurs due to exposure to large quantities of manganese. It may occur due to occupational exposure in industrial workers or may be due to nutritional exposures. Drinking contaminated water containing industrial wastes can result in manganese toxicity and health effects. The optimal concentration of manganese needed for biochemical functions in the body can be met with a balanced diet and vitamin supplements. However, ingesting too much manganese through dietary supplements leads to high levels of manganese in the body. Abnormal manganese concentration in the body causes neurological defects similar to Parkinson's disease. In addition, exposure to elevated manganese levels in growing children impacts neurological development and cognitive performance.

What Is the Daily Recommended Amount of Manganese Needed for Humans?

Dietary and supplemental manganese intake should not increase by more than 10 milligrams per day. Ingestion of large quantities of manganese causes nervous system toxicity and side effects. The manganese needed for each individual depends on age and sex.

Average daily recommended levels of manganese are given below.

1. Infants

• 0 to 6 months - 0.003 milligrams.

• Seven months to 1 year - 0.6 milligrams.

2. Children

• 1 to 3 years of age - 1.2 milligrams.

• 4 to 8 years of age - 1.5 milligrams.

• Boys 9 to 13 years of age - 1.9 milligrams.

• Girls 9 to 13 years of age - 1.6 milligrams.

3. Teenage

• Teen boys 14 to 18 years of age - 2.2 milligrams.

• Teen girls 14 to 18 years of age - 1.6 milligrams.

4. Adults

• Males above 19 years - 2.3 milligrams.

• Females above 19 years - 1.8 milligrams.

• Pregnant women - 2 milligrams.

• Breastfeeding women - 2.6 milligrams.

What Are the Causes of Manganese Toxicity?

The most common etiologies for the development of manganese toxicity are the consumption of contaminated water, occupational exposure through industrial processes like mining, welding, smelting, and inhalation of manganese vapors from a polluted atmosphere. Occupational exposure to manganese may also occur in other industrial workers involved in metal processing and battery manufacturing factories. These environments contain elevated atmospheric concentrations of metals (manganese) inhaled by workers leading to toxicity and systemic effects. In average concentrations, ingested manganese from dietary sources is filtered through the liver to avoid toxicity. Individuals with hepatic diseases are at high risk of developing manganese toxicity due to metal accumulation in the bloodstream.

What Are the Symptoms of Manganese Toxicity?

• Tremors.

• Muscle spasm.

• Difficulty in walking.

• Headache.

• Memory loss.

• Anxiety.

• Emotional disturbances.

• Mood changes.

• Irritability.

• Reduced response to senses.

• Eye irritations.

• Insomnia.

• Sore throat.

• Muscle cramps.

• Shuffling gait.

• Speech difficulties.

• Abnormal posture.

What Are the Adverse Health Effects Associated With Manganese Toxicity?

• Manganism - Overexposure to manganese through occupational exposure or other sources causes neurotoxicity, similar to the clinical presentation of Parkinson's disease. The early stages of manganese toxicity (manganism) affect mental health leading to aggressiveness, irritability, hallucinations, apathy, and psychosis. In advanced stages, irreversible damage to the brain cells causes uncontrollable tremors, facial muscle spasms, loss of balance, and gait abnormalities.

• Inflammation - Excess manganese levels in the body trigger release of inflammatory molecules, which activate inflammatory response in the cells and cause inflammation.

• Impaired Cognition - Manganese toxicity in children causes neurodevelopmental diseases resulting in impaired abilities and delayed milestones.

• Brain Damage - Accidental ingestion of large quantities of manganese may damage brain cells (mainly in the cerebellum and globus pallidus) and cause behavioral alterations.

• Reproductive Health - Studies have shown that occupational exposure to manganese had a significant role in the reduction of fertility. Manganese toxicity causes reduced sperm motility, lower testosterone, and higher luteinizing hormone (LH) levels in males.

• Heart Damage - Too much manganese concentration in the body tissues prevents heart muscles from adequately working, leading to cardiac diseases.

How Can We Manage Manganese Toxicity?

• Chelation Therapy - It involves the use of ethylenediaminetetraacetic acid (EDTA) and para-aminosalicylic acid (PAS) to remove manganese from the body. The use of chelating agents increases the elimination of manganese and thus decreases blood concentration and toxicity.

• Levodopa - It is given for managing extrapyramidal symptoms like muscle spasms, rigidity, tremor, restlessness, and irregular movements associated with neurotoxicity induced by manganese toxicity.

• Supplemental Therapy - Additional supplemental therapy and chelation improve the patient's response and treatment outcomes. Iron supplements, vitamin E, and glutathione are commonly given to patients with manganese toxicity to improve their clinical conditions.

Conclusion

Manganese toxicity occurs due to excessive amounts of manganese in the human body. It leads to nerve cell damage, mental health issues, impaired brain function, and hormonal imbalances. Avoiding environmental exposure to manganese is the primary preventive measure to prevent toxicity. Occupational exposure to manganese can be reduced by following proper precautions and safety measures in working environments. People who take dietary supplements containing manganese must regularly monitor the dose to avoid excess consumption and toxicity.