Air quality conditions in the Lake Tahoe Region can affect human health, visibility, forest health, and regional lake water quality, including the famed clarity of Lake Tahoe. The primary factors known to influence the basin’s air quality are motor vehicle emissions, vehicle entrainment of road dust, wildfire, residential wood smoke, topography, meteorology, and pollutants transported from sources outside the Region (Green et al. 2011; Chen, Watson, and Wang 2011; Zhu, D. et al. 2009; Zhu et al. 2011; Gertler, A.W. et al. 2006; Gertler, A.W. et al. 2008; Cliff and Cahill 2000). Attainment of state, federal and TRPA air quality threshold standards represent conditions that reflect the public’s values for protecting human and environmental health. Achievement of air quality threshold standards could also provide partial evidence that the TRPA Regional Plan and associated programs, and state and federal air quality regulations and programs, are effective at improving air quality in the Region.
This chapter provides an evaluation of current air quality conditions and trends in air pollutants relative to adopted air quality threshold standards and applicable state and federal air quality standards. It also assesses indicators related to factors such as traffic volume that potentially influence air pollutant concentrations. In TRPA Resolution 82-11, TRPA adopted threshold standards for carbon monoxide, ozone, visibility (atmospheric haze), respirable and fine particulate matter, nitrate deposition and odor. National Ambient Air Quality Standards (NAAQS) addressed in this evaluation fulfill requirements of the Bi-State Compact to measure and address the status of compliance with state and federal standards, and in part, requirements of California Air Resources Board (Mulford-Carrell Act) and the Federal Clean Air Act (40 CFR part 50). For air quality threshold standards, this evaluation addresses the status of several numerical standards, management standards with numerical targets, and one policy statement (Table 3-1). This threshold evaluation follows the conventions of the 2011 threshold evaluation report and organizes the findings based on the indicator reporting categories adopted in TRPA Resolution 82-11 (Table 3-1). Overall, 16 of 20indictors were in attainment with almost all having improving trends. Two indicators had insufficient data to make a status determination.