Outdoor concentrations of asbestos in urban environments have been suggested as a potential cause of some asbestos-related diseases. This assertion is contingent upon asbestos being at detectable levels in urban environments. Unfortunately, the studies cited are outdated and utilize methodologies that fail to detect both short and thin fibers. Previous studies on urban ambient asbestos concentrations were completed in 1985 utilizing only phase contrast microscopy (PCM). The last published paper to evaluate urban ambient asbestos concentration utilizing analytical transmission electron microscopy (ATEM) was conducted in 1977. We are not aware of any published or peer reviewed study since that has sampled or analyzed ambient air in urban environments utilizing either PCM or ATEM. In this study, Eurofins J3 Resources, Inc. (EJ3) conducted an ambient air study by collecting 29 samples over 10 days from two different locations within the Greater Houston area in Texas. Houston, by population the fourth-largest city in the United states and the third-largest city by physical size, was chosen for this investigation in part because of its diverse settings from industrial (refineries, petrochemical plants, and ports) to high population density areas (downtown, shopping malls) to miles of freeways (which includes 575.5 miles of freeways) to quiet suburban neighborhoods. The collected samples were analyzed by PCM using NIOSH 7400 and by ATEM using ISO 10312 counting methods. During this investigation, no fibers or asbestos structures were identified by either PCM or ATEM, respectively. Background levels of asbestos, if present, are presumed to be below the applied method detection limits of 0.001 f/cm³ for PCM and 0.0001 f/cm³ for ATEM.