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Assessing Outdoor Air Near Schools

NW Harllee Elementary School - Dallas, TX

Results and Analysis of EPA’s monitoring

EPA selected this school for monitoring because it is located near a paper processing facility and is surrounded by an interstate highway and other roadways sources, which are sources of air toxics emissions.  Computer models were used to determine which air toxics may be present at elevated levels in the outdoor air near the school.  These models showed that acetaldehyde could be present in the air around the school and prompted EPA to test to see if the levels present may be of concern.   Mobile source pollutants, such as acrolein, benzene and 1,3-butadiene, were also monitored, as this school is also located in an area surrounded by an interstate and other roadway sources.

Primary Findings Measured levels of acetaldehyde, benzene and 1,3-butadiene in the air are below the levels of concern suggested by previously available information; however, these results indicate the influence of mobile source pollutants of concern that are the focus of EPA actions nationwide.

Results of a recent short-term laboratory study have raised questions about the consistency and reliability of monitoring results of acrolein.  As a result, EPA will not use these acrolein data in evaluating the potential for health concerns from exposure to air toxics in outdoor air as part of the School Air Toxics Monitoring project.
Key Pollutants Monitored Acetaldehyde. Exposure to high levels can cause irritation of the eyes, skin and upper respiratory tract.
Benzene.  Inhalation of benzene at high levels can affect the bone marrow and can cause anemia and leukemia.
1,3-Butadiene.  Inhalation may affect the reproductive system if people are exposed to high levels.

Acrolein.  Exposure to high levels can cause irritation of the eyes, nose, and throat.
Next Steps Based on the analysis described here, EPA will not extend air toxics monitoring at this school.

EPA remains concerned about emissions from stationary 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.  Additionally, EPA remains concerned about mobile source emissions 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 Texas Commission on Environmental Quality (TCEQ) will continue to oversee industrial facilities in the area through air permits and other programs.  TCEQ will continue to implement reductions in mobile sources through implementation of national programs and its own programs.

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Summary of Study Approach and Findings

Approach:

  • A monitor collected air samples from September 16, 2009 through December 15, 2009 at the Norman Washington (NW) Harllee Elementary School in Dallas, TX. 
  • 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 (e.g., several 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 nearby sources of acetaldehyde, benzene, and 1,3-butadiene emissions.

Findings:

  • Our analysis found that levels of acetaldehyde, benzene, and 1,3-butadiene in the air at the school are below the levels of concern for long-term exposure suggested by previously available information, although these results do indicate the influence of mobile source pollutants of concern.
  • Results of a recent short-term laboratory study have raised questions about the consistency and reliability of monitoring results of acrolein.  As a result, EPA will not use these acrolein data in evaluating the potential for health concerns from exposure to air toxics in outdoor air as part of the School Air Toxics monitoring project.
  • The concentrations of acetaldehyde, benzene, and 1,3-butadiene measured at the school are lower than those suggested by the information that helped identify this school for monitoring.
  • The analysis indicates that acetaldehyde concentrations in the air near the school are not influenced by a paper processing facility.
  • Information from the nearby source indicates that the door manufacturing facility was operating at a typical rate of 80% during the sampling period.
  • Acetaldehyde, benzene, and 1,3-butadiene are common in the outdoor air in urban areas where many sources are located near one another, particularly mobile sources such as cars and other motor vehicles and off-road machinery.  Concentrations of benzene and other air toxics released by mobile sources are often elevated in locations close to roadways, such as at NW Harllee Elementary School.  EPA remains concerned about mobile source emissions 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 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.
  • Based on the analysis described here, EPA will not extend air toxics monitoring at this school.  However, EPA’s ongoing research and national air toxics monitoring programs (e.g., the National Air Toxics Trends Stations) will continue to collect information on mobile source impacts on outdoor air nationally.
  • Click here for additional information

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How We Analyzed the Information We Collected at this School

The analysis considered whether the information collected at the school might raise concerns for the health of children or adults at the school. We looked at the following types of information:

  • Measured acetaldehyde, benzene, and 1,3-butadiene concentrations and information on acetaldehyde, benzene, and 1,3-butadiene
  • Measured wind direction and wind speed at the school
  • Information about nearby sources of acetaldehyde, benzene, and 1,3-butadiene emissions

Analysis of Measured Acetaldehyde Concentrations:

1. Calculate the average: We calculated the average of the acetaldehyde measurements (shown by the black diamond in the graph below). We compared this average to the long-term comparison level (thick line on the graph below). 

Result:  The average acetaldehyde level for the samples collected was well below the long-term comparison level.   The health concern is low.


2. Calculate a range: To account for varying air concentrations of acetaldehyde, we calculated a range around the average. We did this by estimating high and low values that the longer-term concentrations might reach using common statistical tools. We compared the highest point in the range (called the “upper bound”) to the long-term comparison level.

Result: The high end of the range is lower than the comparison level. The health concern is low.

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Analysis of Measured Benzene Concentrations:

1. Calculate the average: We calculated the average of the benzene measurements (shown by the black diamond in the graph below). We compared this average to the long-term comparison level (thick line on the graph below).

Result: The average benzene level for the samples collected was below the long-term comparison level. 

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2. Calculate a range: To account for varying air concentrations of benzene, we calculated a range around the average. We did this by estimating high and low values that the longer-term concentrations might reach using common statistical tools. We compared the highest point in the range (called the “upper bound”) to the long-term comparison level.

Result: The high end of the range is lower than the comparison level.

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Analysis of Measured 1,3-Butadiene Concentrations:

1. Calculate the average: We calculated the average of the 1,3-butadiene measurements (shown by the black diamond in the graph below).  We compared this average to the comparison level (thick line on the graph below). 

Result:  The average 1,3-butadiene level for the samples collected was below the comparison level.  

image

2. Calculate a range: To account for varying air concentrations of 1,3-butadiene, we calculated a range around the average. We did this by estimating high and low values that the longer-term concentrations might reach using common statistical tools. We compared the highest point in the range (called the “upper bound”) to the comparison level.

Result: The high end of the range is lower than the comparison level.


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Analysis of Measured Wind Direction and Wind Speed at the School

We took measurements of wind direction and speed every day during the sample period. We took special note of the wind speed and direction on the days we took measurements of acetaldehyde, benzene, and 1,3-butadiene.

What we looked at What we found
We looked at whether the wind data taken on the days we took measurements of acetaldehyde, benzene, and 1,3-butadiene are similar or different from the wind patterns during the entire sampling period. We found the wind patterns taken on the days we took measurements of acetaldehyde, benzene, and 1,3-butadiene to be somewhat similar to those observed during the entire sampling period.
We looked at whether the wind pattern during the sampling period is reflective of regional wind pattern over the long term. We lack long-term wind data at the monitoring site, and the wind pattern at the NWS station during the sampling period is generally similar to the historical long-term wind flow pattern at that same NWS station.  This suggests that on a regional scale, the 3‑month sampling period may be representative of year-round wind patterns.

Analysis of Information on Nearby Sources of Acetaldehyde, Benzene, and 1,3-Butadiene Emissions

What we looked at What we found
Whether we could determine if the source was operating as usual during the sampling period Information from the nearby source of acetaldehyde indicates that the paper processing was operating at a rate of 81% during the sampling period, which is lightly below its usual conditions of 90% capacity.

There were no disruptions in typical roadway activity during the sampling period.  
The concentrations of acetaldehyde, benzene, and 1,3-butadiene measured at the school are lower than those suggested by the information that helped identify this school for monitoring.
The nearby source of acetaldehyde has an operating air permit issued by TCEQ that includes operating requirements.

EPA’s ongoing research and national air toxics monitoring programs will continue to collect information on mobile source impacts on outdoor air nationally.

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Additional Information

Technical Report for School: Assessing Outdoor Air Near Schools: NW Harllee Elementary School (Dallas, TX) (PDF) (36pp, 647k). 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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