Arsenic is a natural element that can be found in the environment, both in inorganic or organic species. The first one is more usual in waters and grounds, and the second one in marine organisms (for example combined with sugars) and it is less toxic. The acute exposure by inhalation of steam or particles polluted with inorganic arsenic causes gastrointestinal effects (nausea, diarrhoea, abdominal pain) and injuries in the nervous, central and peripheral systems. On the other hand, the chronic exposure to inorganic arsenic causes irritations in the skin and the mucous. If the exposure is dietary, it can cause gastrointestinal effects, cutaneous injuries, anaemia, hyperpigmentation and injuries in the liver and kidneys. Arsenic is classified as carcinogen in humans, being the cause of lung, skin, liver and bladder cancers. There have been cases of strong contamination by polluted water in Bangladesh and some areas in Nicaragua.