A Test of the Scientific Validity of the Visual Air Quality 'Preference Study' Method

摘要

The U.S. Environmental Protection Agency (EPA) is considering setting a secondary National Ambient Air Quality Standard (NAAQS) for fine particulate matter (PM_(2.5)) to maintain urban visual air quality (VAQ) above the level that adversely affects public welfare. EPA is relying on a type of survey it calls a "VAQ preference study" to determine this level. Individuals are shown photographs of the same vista under a range of different visibility conditions, and asked to state whether the VAQ in each photograph is "acceptable" or "unacceptable." EPA considers the effect on public welfare to be adverse at the VAQ level that at least 50% of respondents deem unacceptable (the "VAQ cutpoint"). Given its central role in setting a NAAQS, the scientific validity of this method is an important question. This paper describes a controlled experiment of the robustness of results from the VAQ preference study method, and is the only known exploration of its scientific validity.