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Assessing Outdoor Air Near Schools

Enterprise High School - Enterprise, MS

EPA selected this school for monitoring because it is located near at least one large industry that is a source of air toxics emissions. EPA identified key pollutants to measure in the air near this school based on information about emissions from nearby sources.   The initial air monitoring at Enterprise High School (September 2009) focused on the key pollutant acrolein.   The agency did not analyze those data, however, after results of a short-term laboratory study raised questions about the consistency and reliability of acrolein monitoring results. Since that time, EPA improved the monitoring method for acrolein and conducted additional monitoring at the Enterprise school.   Acrolein concentrations are reported in the table below. Concentrations for other toxic air pollutants collected at the site are also available below. (For example, manganese may be the key pollutant at a monitoring site but other metals, such as arsenic,  measured in the sample also are available.)  

About the Data
The table below shows the level of the key pollutant in air samples collected at the monitoring site beginning in October 2011.   The table also includes individual "sample screening levels" for the key pollutant monitored at the school.  EPA developed these screening levels for this project to help the Agency and the community get an early sense of what the data were showing. The sample screening level is a level of pollution in the air that is below what we expect to cause health problems from short-term exposures – all day, every day over a period ranging up to at least a couple of weeks (longer, for some pollutants).  These screening levels are used only as guidelines for this project. 

About The Table

Compare the sample results to the short-term screening level at the top of the table. Numbers at or below that level indicate the pollutant is not likely to pose immediate health concerns.

To use the screening level, compare it to each sample result:

  • a sample result at or below the sample screening level is not a concern for risk of health problems from short-term exposures.
  • a sample result above the screening level does not mean that there is a risk to children and adults at the school.  It is a signal for EPA to further evaluate those and subsequent results for that pollutant.  EPA is analyzing the potential for health concerns from long-term exposure now that the monitoring has been completed. Interim monitoring results are in the table below. 

After monitoring was completed, EPA analyzed the potential for health concerns from long-term exposure. This analysis can be found under the Final Analysis tab.  Monitoring results are in the table below.

Sample Results
Key Pollutants Acrolein
(Micrograms/cubic meter)
Sample Screening Level 7
10/31/2011 0.30
11/01/2011 0.25
11/07/2011 0.29
11/08/2011 0.32
11/14/2011 0.16
11/15/2011 0.28
12/06/2011 0.06
12/07/2011 0.14
12/12/2011 0.08
12/13/2011 0.09

ND = Pollutant Not Detected
–– = Sample not taken or invalid

Also monitored - 2011 data (PDF) (2pp, 47k)

Also monitored - 2009 data (PDF) (4pp, 69k)

To further evaluate sample results above a screening level, we considered:

  • information about the chemical and its health impacts,
  • information about collection of the sample (e.g., weather, activities around the monitor)
  • potential sources of the pollutant, and 
  • the pattern of levels across multiple samples within the monitoring period. 

If there had been a cause for concern before the sampling period was over, we would have informed the school and worked with the state or local air agency and with the school community to take appropriate action as quickly as possible.

About Some of the Pollutants Monitored
Some of the pollutants monitored (acrolein, acetaldehyde, benzene and 1,3-butadiene) may occur in the air at this school as a result of several different sources, including cars and trucks and the exhaust of other gasoline-powered engines. Because these types of sources are found almost everywhere where there are people, these pollutants are commonly elevated in urban areas across the country, and EPA has identified them as a national priority for reductions in the air in communities across the country.


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