By environmental conditions, we mean the physical properties of the ambient and immediate surroundings of children, youth, and families including pollutants, toxins, noise, crowding as well as exposure to settings such as neighborhoods, housing, schools, and work environments. We will also briefly cite evidence that each of these environmental factors, in turn, is linked to health. Health is defined in its broadest terms to encompass physical and psychological well being. We also note where there are relevant psychosocial processes known to be directly linked to health. For example, some physical environmental conditions affect helplessness and individual beliefs about self-efficacy. These psychological processes are well-identified precursors to psychological ill health. One can look at environmental pollutants at the tract level and rates of morbidity and mortality. It is important to remind the reader of the problem of the ecological fallacy. The ecological fallacy refers to the collection and analysis of data at one level of aggregation and the drawing of conclusions at another level of aggregation. An overarching problem that plagues much of epidemiology is the difficulty of disentangling environmental from individual-based explanations of morbidity or mortality. Many people choose where they live. . Individual health, mental, and cognitive status can affect trajectories of exposure to suboptimal environmental conditions. Research and discussion tends to be focused on specific pollutants, toxins, or particular ambient conditions such as housing quality and each respective factor’s link to income or health The poor are most likely to be exposed to not only the worst air quality, the most noise, the lowest quality housing, and schools, etc. but, of particular consequence, the poor are significantly more likely to be exposed to lower quality environments on a wide array of multiple dimensions. In rental units in the United States, 10% percent of households with incomes below the poverty line rely primarily upon hot air units without ducts and 4% use unvested gas heaters as their primary heat source. For rental households with incomes exceeding $30,000 comparable figures are 7% and 1% for ductless hot air heat and unvented gas heaters, respectively (Statistical Universe, 2000). .