Lewiston Clarkston Valley Air Toxics Measurement Campaign

Abstract: Lewiston Clarkston Valley Air Toxics Measurement Campaign

The purpose of this study is to identify primary sources of elevated levels of formaldehyde (HCHO) and acetaldehyde in the Lewiston-Clarkston valley (L-C valley), located on the Idaho/Washington border. This study is based on a previous air toxics study done between May 2006 - April 2007 by the Nez Perce Tribe Environmental Restoration and Waste Management Air Quality Program and the Idaho Department of Environmental Quality which suggested that levels of formaldehyde were too elevated in the L-C valley and that a further study should be conducted. Formaldehyde and acetaldehyde are known carcinogens that after continuous exposure pose a combined cancer risk level resulting in 89 extra cancers per one million people exposed. Potential causes of high contamination in the area include a pulp and paper mill, a lumber mill, car emissions and secondary formation of formaldehyde. 

In order to identify concentrations of formaldehyde and acetaldehyde, three sites were chosen in the L-C valley where two 12-hour air samples, as well as meteorological data, were collected per day for a 4-week period in July 2016. The sites consisted of two auxiliary sites that were strategically chosen because of their upwind and downwind components and an intensive site. The intensive site hosted a collection of instruments in a trailer, the Mobile Atmospheric Chemistry Laboratory, which made continuous measurements of HCHO and other gases such as carbon monoxide (CO) and nitric oxide (NO). 

Preliminary results indicate that formaldehyde levels were high for a rural area like the L-C Valley and the highest levels (around 10 ppb) were observed between 6:00 and 9:00 am. This has a correlation with the amount of traffic in the studied area during this time period as well as the lower mixing layer height. Measurements indicate that the high levels of formaldehyde are mainly caused by primary emissions, however, there was also a good correlation between levels of formaldehyde and temperature, which indicated that secondary formation was also present. Continued work with air quality models is in progress to confirm the results. An additional field campaign is also planned for the summer of 2017.