Air Toxics Concentrations around a Kraft Pulp and Paper Mill Facility Located in Lewiston, Idaho


The Nez Perce Tribe Environmental Restoration and Waste Management (ERWM) Air Quality Program in co-operation with Idaho Department of Environmental Quality conducted an air toxics monitoring study in the Lewiston-Clarkston Valley and surrounding area from May 2006-April 2007. The study was funded by a grant from the US Environmental Protection Agency’s community air toxics program.


Air samples were collected from five locations to characterize concentrations around the Clearwater Paper pulp and pulp mill (Potlatch at the time of the study).  Samples were collected for 24 hours every sixth day. Concentrations of volatile organic compounds (VOCs), carbonyls (e.g., formaldehyde and acetaldehyde), and particulate metals (e.g., lead and chromium) were measured. Our objectives were to characterize emissions from Clearwater Paper with a determination of spatial patterns and gradients in air toxics concentrations, evaluate the relative contributions of Mill emissions by species to concentrations in the valley, and to characterize air toxics risks, with an emphasis on risks posed by the mill.


The intent of this document is to act as road map to the study results as presented by the contractors and ERWM Air Quality staff.


v     The concentrations from the monitoring data are found in the analytical report from RJ Lee Group, Inc. / Center for Laboratory Sciences (RJLG).


v     The Laboratory for Atmospheric Research in the Department of Civil & Environmental Engineering at Washington State University used the MM5/SMOKE/CMAQ modeling system to investigate the spatial and temporal distributions of modeled air toxics concentrations for a summer and winter time period during the study period. Model performance was evaluated using the monitoring data. Modeled air toxic concentrations of formaldehyde, acetaldehyde, and benzene were underestimated by as much as a factor of five. CMAQ modeling results showed that pollutant spatial distributions depended upon chemistry, pollutant source, and terrain. Primary pollutants emitted from a point source tended to remain in the valley because of the terrain. Elevated concentrations of primary mobile pollutants tended to occur along major roadways within the valley. Diurnal patterns of the air toxics were explained by the mixing height and chemical formation rates. Primary pollutant concentrations were lower during the day due to dilution throughout a deeper mixing layer. Formaldehyde and acetaldehyde had much higher concentrations during the August-September period due to higher chemical production rates compared to the December-January period.


v     The Idaho Division of Health, Bureau of Community and Environmental Health (BCEH) reviewed the risk presented by air toxics concentrations found from monitoring our air. The results are presented in an Agency for Toxic Substances and Disease Registry health consultation.  The levels of contaminants in the air were all below the chronic and acute exposure comparison values. Some of the individual contaminants in air (formaldehyde, acetaldehyde, chloroform, carbon tetrachloride, and chromium) were above their cancer comparison values, but none was high enough to increase the cancer risk sufficiently above the background. Therefore, BCEH concludes that breathing the air in the Lewiston and Clarkston area will not result in an elevated cancer risk. However BCEH suggests decreasing the levels of formaldehyde and acetaldehyde would benefit the community and reduce risks and recommends continued air monitoring. Cancer risk in the Lewiston area was previously thought to be elevated based on comparisons with the entire population of Idaho. An additional cancer benchmark comparison of the LC Valley population with a similar population (Coeur d’Alene) was completed by Idaho Cancer Data Registry Epidemiologist Chris Johnson and interpreted by BCEH. There is scant evidence implicating air toxics detected in the 2006-2007 monitoring with an increase in rates of specific cancers known to be associated with the air toxics detected. 


v     Sonoma Technology, Inc. (STI) performed a series of analyses to provide additional information to address the study objectives. These analyses included data validation, meteorological analysis, spatial gradient analysis, comparisons to national and regional concentrations, and temporal analysis. The full STI report and presentation are available; a summary of their findings follows. STI determined that concentrations of formaldehyde and acetaldehyde are much higher than expected for an area of Lewiston’s size. Formaldehyde is the largest contributor to cancer risk among the pollutants measured and acetaldehyde is a significant contributor. Concentrations of formaldehyde and acetaldehyde were highest in the summer months but do not appear to be related to special events like large wildfires. Secondary production of formaldehyde and acetaldehyde are most likely to be responsible for the seasonal pattern, but it is unclear why concentrations are higher than at other sites in the inland northwest. Insufficient information is available on local concentrations of anthropogenic and biogenic VOCs to determine why formaldehyde and acetaldehyde concentrations are high. Of second highest importance, analytical laboratory measurements of benzene and 1,3-butadiene concentrations reported in this study did not meet our expectations for data quality. The concentrations of benzene were particularly problematic based on both the collocated measurements and comparisons with other pollutants that are typically closely correlated with benzene (e.g., toluene, xylenes). As a result, benzene and 1,3-butadiene concentrations should be considered less reliable for generating risk values, evaluating emissions sources, and assessing spatial gradients in concentrations.  Finally, ambient concentrations of chloroform, tetrachloroethylene, and trichloroethylene were determined to be a result of emissions from Clearwater Paper. The weight-of-evidence consensus from spatial, temporal, and chemical analysis was consistent with Mill emissions. Concentrations of these pollutants were highest at the Idaho Transportation Department site, were emitted from the Mill’s chlorine bleaching process, and were high at random times throughout the monitoring period, which is consistent with fugitive (or upset) emissions. Of these pollutants, chloroform and tetrachloroethylene are small but significant contributors to chronic risk in the Lewiston area.


v     Nez Perce Tribe’s Final Report to EPA.


v     Air Quality staff presentations:

·        Air Toxics Summit, 8/5/08 in Boise, ID

·        Air Toxics Data Analysis Workshop, 10/3/07, Chicago, IL