Yes, if the concentration exceed the limit value it became very dangerous, please review the following links:

https://www.who.int/water_sanitation_health/dwq/chemicals/manganese.pdf

Article Manganese Removal from Drinking Water Sources

Manganese (Mn) element can impart undesirable taste and odour in drinking water. Mn is an essenti al element that is required by humans for normal growth. Mn deficiency affects bone, the brain and reproducti on. The greatest source of Mn is usually from food and intake from drinking water is substanti ally lower. The health effects from over-exposure of Mn are dependent on the route of exposure, the chemical form, the age at exposure, and an individual’s nutriti onal status.

Toxicity has occurred mainly as a result of inhalati on of Mn dust

over long periods in occupati onal setti ngs. The nervous system has been determined to be the primary target with neurological eff ects generally observed. In contrast to inhalati on exposure, Mn is regarded as one of the least toxic elements via the oral route. In one case involving

heavy consumpti on of highly contaminated well water that contained Mn concentrati ons > 14 mg/L the symptoms included lethargy, increased muscle tone, tremor and mental disturbances, however, concentrati ons of other metals were also high and the reported effects may not have been due solely to Mn.5

Evidence of neurological, cognitive, and neuropsychological effects of Mn exposure from drinking water in children has generated widespread public health concern.

Different countries have set different guild line staandard for drinking. An Australian health-based guideline value for Mn is set at 0.5 mg/L and at this concentrati on it is considered that Mn will not impact negatively upon human health for a lifeti me of exposure through drinking water. Even though the assumpti ons applied by the USEPA and the WHO are slightly

diff erent, their recommended health based limits are similar; 0.3 mg/L and 0.4 mg/L respecti vely.

https://www.google.com.pk/url?sa=t&source=web&rct=j&url=https://www.waterra.com.au/publications/document-search/%3Fdownload%3D542&ved=2ahUKEwji6afh5OLpAhWGDWMBHetrAlMQFjAMegQIBRAB&usg=AOvVaw2dc5cKkUNP6CMPDQjo4c9q

The Department of Public Health recently set a drinking water Action Level for manganese of 0.5 mg/l to ensure protection against manganese toxicity. This Action Level is consistent with the World Health Organization guidance level for manganese in drinking water.

Manganese effects occur mainly in the respiratory tract and in the brains. Symptoms of manganese poisoning are hallucinations, forgetfulness and nerve damage. Manganese can also cause Parkinson, lung embolism and bronchitis. When men are exposed to manganese for a longer period of time they may become impotent.

Manganese above 0.5 mg/l is toxic to human health and can cause discolouration and an unpleasant taste in drinking water.

A number of recent studies have demonstrated that Mn consumed through drinking water is correlated with intellectual deficits in children. Despite some challenges with confounding factors, and the biases associated with measuring intellectual capacity, there is mounting evidence demonstrating the adverse neurological impacts of consuming Mn contaminated drinking water, especially in children who exhibit greater absorption of Mn coupled with a reduced capacity for biliary excretion.

This is a good systematic review that summarizes the last 15 years or so of research on this topic:

Iyare, P. U. (2019). The effects of manganese exposure from drinking water on school-age children: A systematic review. Neurotoxicology.

These two Bouchard et al. studies were what got me reading about this topic in the first place:

Bouchard, M., Laforest, F., Vandelac, L., Bellinger, D., & Mergler, D. (2007). Hair manganese and hyperactive behaviors: pilot study of school-age children exposed through tap water. Environmental health perspectives, 115(1), 122-127.

Bouchard, M. F.; Sauve, S.; Barbeau, B.; Legrand, M.; Brodeur, M.-E.; Bouffard, T.; Limoges, E.; Bellinger, D. C.; Mergler, D. (2011). Intellectual Impairment in School-Age Children Exposed to Manganese from Drinking Water. Environ. Health Perspect. 119 (1), 138−143.

That`s for sure. Being an biophilic element several plants tends to take t form the soil. On aqueous systems near mining areas, critical health issues have been documented by clinical studies on wide number of individuals.

Different countries have set different guidelines/standard for drinking water. An Australian health-based guideline value for Mn is set at 0.5 mg/L and at this concentration, it is considered that Mn will not impact negatively upon human health for a lifetime of exposure through drinking water.

However, Manganese (Mn) element can impart undesirable taste and odour in drinking water. The nervous system has been determined to be the primary target with neurological effects generally observed.

Mn is essential element but if the concentration exceed the limit value it became dangerous for human.

Yes, Mn can be toxic at elevated concentration. The MCL for Manganese is 0.5mg/L. Note, "All substances are poison, the dose makes the difference".....Paracelsus

Yes, children exposed to high concentrations of manganese in drinking water suffer from intellectual impairment.

Article Intellectual Impairment in School-Age Children Exposed to Ma...

Mn is very much essential for our health. Although beyond threshold limit it causes damage of the same. So, overdose and deficiency of manganese, both are bad.

At elevated exposures, manganese (Mn) has been associated with increased levels of externalizing behaviors, including irritability, aggression, and impulsivity in children.

Article Manganese Exposure from Drinking Water and Children’s Classr...

It depends on the concentration.

However, David Ozomata Balogun has already answered.

Please have a look at the link below:

Article Manganese Exposure from Drinking Water and Children’s Academ...

It should be noted that the presence of manganese in drinking-water will be objectionable to consumers if the manganese is deposited in water mains and causes water discoloration. Concentrations below 0.05 mg/l are usually acceptable to consumers, although this may vary with local circumstances.

Hello,

thanks for all the feedback. In 2019 and 2020 alone there were many substantial articles on the subject of human health and Mn:

Aung, M.T. et al., 2020. Manganese is associated with increased plasma interleukin-1beta during pregnancy, within a mixtures analysis framework of urinary trace metals. Reprod Toxicol, 93: 43-53.

Frndak, S. et al., 2019. Latent subgroups of cognitive performance in lead- and manganese-exposed Uruguayan children: Examining behavioral signatures. Neurotoxicology, 73: 188-198.

Kullar, S.S. et al., 2019. A benchmark concentration analysis for manganese in drinking water and IQ deficits in children. Environ Int, 130: 104889.

McRae, N. et al., 2020. Blood manganese levels during pregnancy and postpartum depression: A cohort study among women in Mexico. Neurotoxicology, 76: 183-190.

Miah, M.R. et al., 2020. The effects of manganese overexposure on brain health. Neurochem Int, 135: 104688.

Rolle-McFarland, D. et al., 2019. The association of bone, fingernail and blood manganese with cognitive and olfactory function in Chinese workers. Sci Total Environ, 666: 1003-1010.

Sachse, B. et al., 2019. Dietary Manganese Exposure in the Adult Population in Germany-What Does it Mean in Relation to Health Risks? Mol Nutr Food Res, 63(16): e1900065.

Tang, B. et al., 2019. High-throughput assessment of toxic effects of metal mixtures of cadmium(Cd), lead(Pb), and manganese(Mn) in nematode Caenorhabditis elegans. Chemosphere, 234: 232-241.

Yoon, M. et al., 2019. Assessing children's exposure to manganese in drinking water using a PBPK model. Toxicol Appl Pharmacol, 380: 114695.

Yes, please review the following articles contain good information:

1. https://www.who.int/water_sanitation_health/dwq/chemicals/manganese.pdf

2. https://www.canada.ca/en/health-canada/programs/consultation-manganese-drinking-water/manganese-drinking-water.html

high concentrations of manganese cause nervous system disease with symptoms like Parkinson’s disease.

Refer IS 10050---Specifications for drinking water.

Here is our latest contribution to the topic of manganese:

Hamer, K., Gudenschwager, I. and Pichler, T., 2020, Manganese (Mn) Concentrations and the Mn-Fe Relationship in Shallow Groundwater: Implications for Groundwater Monitoring. SoilSystems, 4, 49; doi:10.3390/soilsystems4030049, p. 19.

As per the IS10500 Standards for drinking water, Mn requirements/ acceptable limit for the body is 0.1 ppm, whereas the permissible level is 0.3 ppm. So, we have to stick to these limits. Further, the daily intake can also be accounted for from food standard limits. The toxic effect starts beyond that.