Sick building syndrome (SBS) is a condition in which people in a building suffer from symptoms of illness or become infected with chronic disease from the building in which they work or reside. The outbreaks may or may not be a direct result of inadequate cleaning or inappropriate cleaning methods. SBS has also been used to describe staff concerns in post-war brutalist-style buildings with defects in the construction materials or assembly process and-or inadequate maintenance. Certain symptoms tend to increase in severity with the time people spend in the building; often improving over time or even disappearing when people are away from the building. Exposure to toxic black mold might be a problem. SBS is also used interchangeably with "building-related symptoms", which orients the name of the condition around patients symptoms rather than a "sick" building. A 1984 World Health Organization (WHO) report suggested up to 30% of new and remodeled buildings worldwide may be subject of complaints related to poor indoor air quality.