Linn County Air Quality Division
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Linn County Response to Air Toxics Report

December 12, 2008


The USA Today issued a series of articles this week on toxic pollutants that are released by industry and the impact on ambient air.  Many of our local media have followed up on the USA Today article to look at the local concerns raised by the USA Today report.

So what is USA Today reporting?  The US EPA requires that certain industry types report their releases of toxic chemicals into the environment each year.  This is known as the Toxic Release Inventory (TRI) and is legislated by the US Congress under the Emergency Planning and Community Right-to-Know Act (EPCRA).  EPA Administers this program.  It is important to note that the releases reported by industry are only about one third of all pollution released to the atmosphere in Linn County.  The other major source (also about 1/3 of the total) are mobile sources such as automobiles, trucks, construction and agricultural equipment, and even trains and airplanes.  The final third are all the other agriculturalm, small business, and residential activities. 

USA Today used the information from the 2005 TRI reports and a computer model developed by EPA known as "Risk-Screening Environmental Indicators" or RSEI model to estimate public exposure from the release of these pollutant.   A maximum exposure was calculated at 1 kilometer intervals throughout our area forming a "grid."  Each value is unique for each one kilometer interval. 

It is well known that pollutants have different levels toxicity.  EPA maintains a database of scientifically reviewed toxicity studies and publishes threshold values for every pollutant where there is sufficient information to do so.  Some toxins are known or suspected to also cause cancer (e.g. carcinogens).  For these chemicals, EPA also publishes a separate carcinogenic risk value.  USA Today used the relative toxicity and carcinogenicity of each pollutant and the maximum exposure calculated from the RSEI model at each one kilometer interval to determine an overall estimated level of risk.  Risk levels are added where multiple pollutants and industrial sources overlap on the RSEI model grid.

The last step of the analysis was to overlay the school locations onto the grid of calculated risks.  The school is assigned the risk level calculated for the 1 km by 1 km area.  All schools were then ranked based on their relative calculated risk score.

The Air Quality Division at Linn County Public Health is acting on this reporting in many ways.  First, our website and the website of the Iowa DNR Air Quality Bureau and the US EPA already provide a lot of information on the pollutants and industries highlighted in their reports.  We are creating a new Air Toxics portal for this information on our web page to make it easier to find this information.  This portal will continue to be expanded as we develop more information.

Second, the Air Quality Division is performing additional analysis on the exposure of the public to the air toxics released by industry.  To perform a risk analysis for the entire country, USA Today had to make many assumptions about each invidivual source.  As a local air quality program, we are able to gather more specific data that USA Today could not.  Linn County will also be using a much more rigorous air dispersion model known as AERMOD to calculate predicted maximum exposure to each reported pollutant.  This model will allow us to include data on local meteorological conditions, terrain, and consider the effects of buildings and other structures that may affect dispersion.

Third, Linn County Public Health has been monitoring a limited number of air toxics including benzene, formaldehyde, and acetaldehyde.  Based primarily on the TRI reports for acetaldehyde and some limited monitoring results for acetaldehyde in our area, Linn County was awarded an EPA grant to further monitor and evaluate acetaldehyde concentrations associated with industrial fermentation of yeast and alcohol.  This study will begin in April and run for two years.  Additional information on this study is posted on our website.

The Air Quality Division of Linn County Public Health (LCPH) issues air quality permits for many of these industries in our area.  The Air Quality Division periodically inspects these facilities and enforces Federal, State, and Local regulations.  The permits issued to these facilities are listed on our website.  Some of them are available for download but many have not yet been scanned and posted.  Please contact us if you cannot find what you are looking for.