Fundamental Concepts, Current Regulatory Design and Interpretation
Development of an organism from a fertilized egg into a fully formed individual is a process that is highly regulated, amazingly complex, and at risk of disruption at many stages along its trajectory. Disturbances in development can result from a myriad of intrinsic and extrinsic factors, such as altered maternal homeostasis and exposure to substances such as pharmaceuticals, chemicals, environmental pollutants, and certain disease vectors. Developmental toxicology is the study of adverse effects on the developing organism that might result from exposures occurring during sensitive periods of development before conception (to either parent), prenatally, and in some cases, even after birth. Potential effects might include compromised survival (i.e., early embryo loss, miscarriage, or death), reduced or delayed growth, and in some cases birth defects. Additionally, there is the possibility that these exposures could compromise the function of the nervous, immune, reproductive or other systems, perhaps with long-term consequences to the individual and society. Evaluating the potential of various agents to affect biological development, using sound science and the technical and regulatory tools at our disposal, allows us to work towards prevention of the devastating consequences of disrupted development. Constantly evolving scientific advances help provide the means to protect the most vulnerable individuals of our species and population: embryos, fetuses, and children. This introductory chapter addresses the basic principles of developmental toxicology and the foundations of developmental hazard identification for pharmaceuticals and industrial or environmental chemicals.