Why are there so few measures of the physical environment?

Physical environment is an important determinant but it is difficult to find good measures at a county level. We were hoping to be able to add a county-level measure of water quality but were not able to acquire reliable data on this community characteristic. We have added a new measure this year, Access to Recreational Facilities, to draw attention to the need for opportunities for exercise within communities. Ideally, we would have measures of safe sidewalks, parks, bicycle trails, etc to reflect this important need but there are no nationwide sources that we are aware of where county-level data are available on these characteristics.