NARSTO_EPA_SS_HOUSTON_TEXAQS2000_PM_SIZE_MASS is North American Research Strategy for Tropospheric Ozone (NARSTO) Environmental Protection Agency (EPA) Supersite (SS) Houston, Texas Air Quality Study 2000 (TexAQS2000) Size-specific Particulate Matter (PM) Mass Concentration Data. This file reports size segregated mass particulate data collected with a micro-orifice uniform deposit impactors (MOUDI) sampler during the TexAQS2000 at the Houston Regional Monitoring (HRM) Site 3 and LaPorte Houston Supersite monitoring locations. Daily MOUDI sampling began on August 17, 2000 and ended on September 13, 2000. The MOUDI is a model 100 rotating micro-orifice uniform deposit impactor from MSP Corporation. The Houston Supersite is one of several Supersites that was established in urban areas within the United States by the U.S. Environmental Protection Agency (EPA) to better understand the measurement, sources, and health effects of suspended PM. The overall goals were to characterize the composition and identify the sources of PM in Southeastern Texas, to develop and test new methods for characterizing fine PM, and to collect data on the physical and chemical characterization of fine PM that can be used to support exposure and health effects studies. NARSTO, which has since disbanded, was a public/private partnership, whose membership spanned across government, utilities, industry, and academe throughout Mexico, the United States, and Canada. The primary mission was to coordinate and enhance policy-relevant scientific research and assessment of tropospheric pollution behavior; activities provide input for science-based decision-making and determination of workable, efficient, and effective strategies for local and regional air-pollution management. Data products from local, regional, and international monitoring and research programs are still available.