Twelve schools have reported problems with mold, which can cause health problems such as coughing, allergic reactions and even pneumonia, said Maria Mekeel, head nurse at the Chapel Hill Children's Clinic.
But Steve Scroggs, Chapel Hill-Carrboro assistant superintendent for support services, said the mold does not create problems, but merely frustrates problems people already have.
"It's triggering people's allergic reactions, not causing them," Scroggs said.
In Chapel Hill and Carrboro the affected schools are Carrboro and Frank Porter Graham elementary schools, Grey Culbreth and Guy B. Phillips middle schools and Chapel Hill High School.
In the Wake County area, Hunter, Northwoods, Powell, Underwood and Zebulon elementary schools, Martin Middle School and Enloe High School are affected.
School officials say it is impossible to tell how many students have been affected because the symptoms can be caused by a number of factors. Mold is a problem for schools in particular because children's underdeveloped immune systems are more susceptible to health complications from it, Mekeel said.
All of the schools experiencing problems are relatively old -- 40 years or more. Scroggs said mold can be a problem at older schools because older equipment, such as dirty carpets, leaky pipes and outdated heating and air conditioning systems, can encourage mold growth.
Mekeel said the best way to protect against mold in the air is to "prevent the mold from beginning" by keeping areas dry and well lit, or by spraying areas with bleach to stop mold from growing in places such as it does in air ducts.
Scroggs said the main cause of mold is moisture that remains trapped in air ducts from summer precipitation that creates the conditions mold needs to grow.