We are exposed to metals and chemicals through the air we breathe, the water we drink, the food we eat, and even the things we touch. Since it is so easy to come into contact with these toxicants, it is important to learn what short and long-term effects they have on health. The Early Life Exposures in Mexico to ENvironmental Toxicants (ELEMENT) cohort includes three birth cohorts from Mexico City maternity hospitals that have been followed for over two decades to learn how environmental exposures to metals and chemicals affect pregnant women and children.