A rural North Carolina county and a New York City borough are the first locations for the largest long-term study of children's health and development in the U.S.

The National Children's Study will eventually include 100,000 children in 105 locations who will be followed from before birth until age 21. Researchers will study the effects of genetic and environmental influences on chronic diseases such as asthma, autism, birth defects and diabetes.

For now, researchers are focused on Duplin County and Queens, N.Y.

Duplin County is home to about 52,000 people in eastern North Carolina, about 72 percent of them white and 27 percent black. That compares to Queens, N.Y., where the number of babies born annually equals more than half of Duplin County's population. Queens has immigrants from more than 100 nations.