ST. LOUIS - Researchers from several St. Louis-area universities will be part of what is being called the largest study of child and human health. The National Children's Study will follow 100,000 children from across the country from before birth to age 21. The goal is to learn more about environmental and genetic factors that affect their health and well-being. As part of the study, a team led by Saint Louis University's School of Public Health will look at 250 children in St. Louis and 250 in nearby Macoupin County, Illinois. Environmental samples will be taken from water and air. Children will also be screened for asthma, birth defects, diabetes, injury susceptibility, obesity and physical and mental development disorders.