text: ATSDR maintains registries of people who were exposed to certain toxic substances or have certain diseases. Participation in these registries is voluntary, and individual data and personal information is kept private. The information collected is used by epidemiologists and other researchers to examine long-term health outcomes or risk factors for illness. It can also help doctors diagnose those health conditions in other individuals and treat them earlier. The agency also uses registries to contact registered individuals with important health information.