Mercury poisoning, also known as mercuralism, is the phenomenon of toxication by contact with mercury. The main dangers associated with elemental mercury are that at standard conditions for temperature and pressure, mercury tends to oxidize forming mercury(II) oxide, and that if dropped or disturbed, mercury will form microscopic drops, increasing its surface area dramatically. Air saturated with mercury vapor at room temperature is at a concentration many times the toxic level, despite the high boiling point (the danger is increased at higher temperatures). Watersheds tend to concentrate mercury through erosion of mineral deposits and atmospheric deposition. Plants absorb mercury when wet but may emit it in dry air. Plant and sedimentary deposits in coal contain various levels of mercury. Like plants, mushrooms can also accumulate mercury from the soil. Mercury damages the central nervous system, endocrine system, kidneys, and other organs, and adversely affects the mouth, gums, and teeth. Exposure over long periods of time or heavy exposure to mercury vapor can result in brain damage and ultimately death. Mercury and its compounds are particularly toxic to fetuses and infants. Women who have been exposed to mercury in pregnancy have sometimes given birth to children with serious birth defects.