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Assessing Outdoor Air Near Schools

Sto-Rox Elementary School and Sto-Rox Middle School - McKees Rock, PA

EPA selected this school for monitoring because it is located near at least one large industry that is a source of air toxics emissions. The pollutants monitored were different from school to school. Based on emissions from nearby sources, EPA identified key pollutants to measure in the air near this school. We reported concentrations of those key pollutants in the table below. Concentrations for other toxic air pollutants collected at the site are also available (PDF) (3pp, 74k). (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 levels of key pollutants in air samples collected at the monitoring site beginning in August 2009.   The table also includes individual “sample screening levels” for each key pollutant monitored at the school.  EPA developed these screening levels 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).

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. 

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 Arsenic
(Nanograms/cubic meter)
(Micrograms/cubic meter)**
(Micrograms/cubic meter)
Chromium VI
(Nanograms/cubic meter)
Sample Screening Level 150 30 6.4 580
08/05/2009 0.08 -- 0.0000200 ND
08/11/2009 -- -- -- ND
08/17/2009 0.04 -- 0.000210 0.0266
08/23/2009 1.51 -- ND ND
08/29/2009 -- -- ND --
09/04/2009 2.97 -- 0.0000400 0.0223
09/10/2009 -- -- 0.0000800 0.0062
09/16/2009 0.007 -- 0.000190 0.0059
09/22/2009 1.33 -- 0.0000500 0.0296
09/28/2009 0.04 0.28 ND ND
10/04/2009 1.22 0.831 0.0000500 ND
10/10/2009 0.81 0.521 ND ND
10/16/2009 1.28 1.56 0.000170 0.0478
10/22/2009 1.70 -- 0.0000700 0.0195
10/28/2009 0.39 0.460 ND 0.0218
11/03/2009 0.73 0.607 0.0000500 0.0170
12/10/2009 -- -- -- --
12/14/2009 -- 0.527 -- --
12/17/2009 -- 1.12 -- --
12/21/2009 -- 0.547 -- --
12/29/2009 -- -- -- --
01/06/2010 -- 0.905 -- --

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

** EPA has replaced some data that previously were incorrectly reported. See the changes here.

NOTE: Additional volatile organic compound samples are being collected at this site. Previous samples have been invalidated due to a sampler contamination issue. Please click here for more information.

Also monitored (PDF) (3pp, 74k)

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. 

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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