Tracking Visibility Progress for the Regional Haze Program: Current Status and Recent Updates

摘要

The 2017 revisions to the Regional Haze Rule provide forchanges in the approach for tracking visibility progress in theregional haze program that focuses on controllable anthropogenicemission sources in the United States, rather thansources like wildfires, dust storms, and international anthropogenicemissions that are either difficult to prevent or notdirectly under the control of U.S. authorities. EPA’s 2018 technicalguidance describes a recommended approach to trackdays with the highest anthropogenic impairment, and adjust the URP to account for international anthropogenic visibilityimpacts. However, states continue to have flexibility to developalternative approaches for estimating natural and anthropogeniccontributions, and optionally adjusting the URPfor international anthropogenic impacts at individual Class Iareas. EPA is preparing to release updated photochemicalmodeling results, which includes estimated visibility impairmentcontribution information for international anthropogenicsources and prescribed fires, which may be usefulfor states that choose to use the data.