Lung function in infancy predicts pulmonary function throughout life. in utero and early postnatal exposures influence both childhood and adult lung structure and function, and may predispose to chronic obstructive lung disease (COPD) and other disorders. The nutritional and endogenous chemical environment affects development of the lung resulting in altered function in the adult. Studies now suggest that similar adverse impacts may occur in animals and humans following exposure to environmentally relevant doses of certain xenobiotics during critical windows in early life. Assessment of environmental chemical impacts on the lung requires studies that evaluate specific alterations in structure or function, endpoints not regularly assessed in standard toxicity tests. Identifying effects on important signaling events may inform developmental toxicology study protocols. Such knowledge may enable policies promoting true primary prevention of lung diseases. Please click here to access the complete article in Environmental Health Perspectives.