Traces of manganese found in household water could be sufficient to cause permanent brain damage to those who take a regular shower, according to a report published in the US journal Medical Hypotheses. John Spangler of the Wake Forest University School of Medicine in North Carolina and his team suggested that breathing in vapour containing manganese salts could be dangerous over the longer term. "Inhaling manganese, rather than eating or drinking it, is far more efficient at delivering manganese to the brain. The nerve cells involved in smell are a direct pathway for toxins to enter the brain," Spangler wrote. The team used animal studies aimed at showing how much a person who showered for 10 minutes a day would absorb.The effects are dependent on the levels of manganese in household water. In the United States, a limit of 0.5 milligrams a litre of water is imposed by the Environmental Protection Agency, while in the European Union, an upper level of just a 10th of that was set only in 1998. Spangler suggested that even levels below the US upper limit could lead to brain damage.