Most of the person's exposure to many air pollutants comes through inhalation of indoor air, both because of the amount of time spent indoors and because of the higher pollution levels indoors. According to the World Health Organization, about one third of new buildings worldwide are not fit for human use due to severe indoor air pollution. Important sources of indoor pollutants include, the human body and human activities, emissions from building materials, furnishings and appliances and use of consumer products.