Xochitl CRUZ NUNEZ became environmental evaluation and impact subdirector for the Environment Secretariat of the Federal District in 1996. Her research entails cooperating with the environmental sciences group at the National Autonomous University of Mexico (UNAM) to develop and refine atmospheric models to improve environmental decision-making. She joined Secretariat after 10 years in academia, working first in the special studies on modeling and simulation and, in 1994, assuming responsibility for the emissions inventory department for the State of Mexico. In a previous position at the Mexican Petroleum Institute, she participated in the Mexican-American Research Initiative (MARI) to improve air quality. She has a master's degree in chemistry from UNAM, where she is currently a doctoral candidate in air quality modeling.