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Assessing Outdoor Air Near Schools

Vonore Middle School and Vonore Elementary School - Vonore, TN

Results and Analysis of EPA’s monitoring

EPA selected Vonore Middle School for monitoring because it was located near a boat manufacturing facility that is a source of air toxics emissions. For the purposes of this study, results from the air monitoring at Vonore Middle School are considered to be indicative of conditions at the nearby Vonore Elementary School.  Computer models were used to determine which air toxics may be present at elevated levels in the outdoor air near the schools. These models showed that diisocyanates (1,6-hexamethylene diisocyanate (1,6-HDI), 4,4-methylene diphenyl diisocyanate (MDI), and 2,4-toluene diisocyanate (2,4-TDI)) could be present in the air around the school and prompted EPA to test to see if the levels present may be of concern.   

Primary Findings Monitors located at the school did not detect any diisocyanates (1,6-HDI, MDI, 2,4-TDI) in any samples.
Pollutants Monitored
Diisocyanates (1,6-HDI, MDI and 2,4-TDI). Inhalation may affect the respiratory system if people are exposed to high levels.
Next Steps EPA has decided to continue air toxics monitoring at Vonore Middle School because information supplied by the Tennessee Department of Conservation (TDEC) indicated that during the monitoring period, the nearby source was operating at a significantly lower level than normal.   Additional monitoring will take place when TDEC has determined the facility is operating at a level closer to normal (at least 50% of capacity).

EPA remains concerned about emissions from sources of air toxics and continues to work to reduce those emissions across the country, through national rules and by providing information and suggestions to assist with reductions in local areas.

The TDEC will continue to oversee the manufacturing facility through air permits and other programs.

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Summary of Study Approach and Findings


  • A monitor collected air samples from September 4, 2009 through December 9, 2009 at the Vonore Middle School in Vonore, Tennessee.  For the purposes of this study, results from the air monitoring at Vonore Middle School are considered to be indicative of conditions at the nearby Vonore Elementary School (located within a half mile of Vonore Middle School). Diisocyanates (1,6-HDI, MDI, or 2,4-TDI) were the key pollutants of interest. 
  • We posted individual air sample results on this website throughout the monitoring period to keep your community informed during the monitoring period.
  • During the monitoring period, we evaluated the monitored concentrations to see if there was a concern from short-term exposures (up to a couple of weeks).
  • When the monitoring was complete, we analyzed the results to see if there was a concern from long-term exposures (over a lifetime).
  • Also, when the monitoring was complete, we evaluated all the air samples from the on-site monitor. We also evaluated information on wind speed and wind direction from a weather monitor at the school, along with historical weather information and information about a nearby source of diisocyanate emissions.


  • EPA has decided to continue air toxics monitoring at this school.  We determined that the source was operating at a level much lower than normal during our monitoring period.  Therefore, we will continue air toxics monitoring at this school when TDEC has determined that the boat manufacturer is operating at a normal level.
  • The process to identify schools for monitoring relied on emissions estimates and other information. Ambient air monitoring at the school allowed measurement of what was actually in the air.
  • Data collected during monitoring found no detectable levels of diisocyanates.
  • The most recently available diisocyanates (1,6-HDI, MDI, 2,4-TDI) emissions estimates for the nearby facility from the 2008 TRI are lower than the estimates used to identify this school for monitoring. 
  • Click here for additional information

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Analysis of Information on Nearby Source of Diisocyanates (1,6-HDI, MDI, 2,4-TDI) Emissions

What we looked at What we found
Whether we could determine if the source was operating as usual during the sampling period This facility was operating at a rate 20% of its capacity during the sampling period in comparison to its usual conditions of 50 to 60%. There was no detection of any diisocyanates (1,6-HDI, MDI, 2,4-TDI).
The nearby source of diisocyanates (1,6-HDI, MDI, 2,4-TDI) has operating permits issued by the State of Tennessee that includes operating requirements. 
The most recently available diisocyanate emissions reports for this source (2008 TRI) are less than 500 pounds per year. The 2007 TRI emissions report is about fifty percent higher (0.4 tons per year) than that relied upon in previous modeling analysis for the same area.

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Additional Information

Technical Report for School: Assessing Outdoor Air Near Schools: Vonore Middle School (Vonore, TN) (PDF) (17pp, 424k). The technical report is geared toward risk assessors, risk managers, and other regulatory agencies. 

Background on School Monitoring Effort

General Questions and Answers for School Monitoring Effort

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