Assessing Outdoor Air Near Schools
Concord Elementary School - Seattle, WA
Results and Analysis of EPA’s monitoring
EPA selected this school for monitoring because it is located near several small metal plating facilities, roadways, and an airport, 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 hexavalent chromium, benzene, 1,3-butadiene, and lead 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 | Levels of hexavalent chromium in the air at the school are below levels of concern for short-term and long-term exposure. Levels of 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. Levels of lead, a pollutant for which there are national standards for ambient (outdoor) air, are below the level of the national standard for protection of public health. |
| Key Pollutants Monitored | Hexavalent chromium. Inhalation of hexavalent chromium at high levels can damage the respiratory system and cause cancer. |
| Next Steps | Based on the analysis described here, EPA will not extend air toxics monitoring at this school. However, EPA remains concerned about stationary source and mobile source emissions 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 Puget Sound Clean Air Agency (PSCAA) will continue to implement reductions in mobile source emissions through implementation of national programs and will continue to oversee industrial facilities in the area through air permits and other programs. |
Summary of Study Approach and Findings
Approach:
- A monitor collected air samples from August 20, 2009 through November 18, 2009 at Concord Elementary School in Seattle, WA.
- 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 hexavalent chromium, benzene, 1,3-butadiene, and lead emissions.
Findings:
- Our analysis found that levels of hexavalent chromium in the air at the school are below levels of concern for long term exposure.
- Measured levels of benzene and 1,3-butadiene and associated longer-term concentration estimates 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.
- Levels of lead, a key pollutant for which there are national standards for ambient (outdoor) air, are below the national standard for protection of public health.
- 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. Levels of benzene and 1,3-butadiene in many urban areas, such as Detroit, can be elevated. 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.
- There are a number of potential sources of hexavalent chromium within a one mile radius, including sources involved in chrome plating, steel production, and other types of metal working. However, from this study it is not possible to discern direct emissions or the impact at the school from the individual sources as the sources’ emissions are below required reporting thresholds and the total emissions per source is unclear.
- The most recently available benzene, 1,3-butadiene, and lead emissions estimates for the nearby roadways and airport from the 2005 National-Scale Air Toxics Assessment (NATA) are lower than the estimates used to identify this school for monitoring.
- Based on the analysis summarized here, EPA will not extend air toxics monitoring at this school.
- Click here for additional information
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 hexavalent chromium, benzene, 1,3-butadiene, and leadconcentrations and information on hexavalent chromium, benzene, 1,3-butadiene, and lead
- Measured wind direction and wind speed at the school
- Information about nearby sources of hexavalent chromium, benzene, 1,3-butadiene, and lead emissions
Analysis of Measured Hexavalent Chromium Concentrations:
1. Calculate the average: We calculated the average of the hexavalent chromium measurements (shown by the black diamond in the graph below). We compared this average to the long-term comparison levels (see thick line on the graph below).
Result: The average hexavalent chromium level for the samples collected was well below the long-term comparison levels. The health concern is low.
2. Calculate a range: To account for varying air concentrations of hexavalent chromium, 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 levels.
Result: The high end of the range is much lower than the comparison levels. The health concern is low.
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.
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.
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.
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 long-term comparison level.
Result: The high end of the range is lower than the comparison level.
Analysis of Measured Lead Concentrations:
1. Calculate the average: We calculated the average of the lead (TSP) measurements for each of the 3-month periods in which monitoring occurred (the higher of these averages is 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). The comparison level is the level of the national ambient air quality standards (NAAQS) for lead, which is for a 3-month averaging period.
Result: The average lead level for the samples collected was well below the comparison level. The health concern is low.
2. Calculate a range: To account for varying air concentrations of lead, we calculated a range around the average 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. The health concern is low.
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 hexavalent chromium, benzene, 1,3-butadiene, and lead.
| What we looked at | What we found |
| We looked at whether the wind data taken on the days we took measurements of hexavalent chromium, benzene, 1,3-butadiene, and lead 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 hexavalent chromium, benzene, 1,3-butadiene, and lead to be generally 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. | Although we lack long-term wind data at the monitoring site, 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. |
Analysis of Information on Nearby Sources of Hexavalent Chromium, Benzene, 1,3-Butadiene, and Lead Emissions
| What we looked at | What we found |
| Whether we could determine if the source were operating as usual during the sampling period. | There are a number of potential sources of hexavalent chromium within a one mile radius, including sources involved in chrome plating, steel production, and other types of metal working. However, from this study it is not possible to discern direct emissions or the impact at the school from the individual sources as the sources’ emissions are below required reporting thresholds and the total emissions per source is unclear. The most recently available benzene, 1,3-butadiene, and lead emissions estimates for the nearby roadways and airport from the 2005 National-Scale Air Toxics Assessment (NATA) are lower than the estimates used to identify this school for monitoring. |
The concentrations of hexavalent chromium, benzene, 1,3-butadiene, and lead measured at the school are lower than those suggested by the information that helped identify this school for monitoring. |
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| PSCAA will continue to implement reductions in mobile source emissions through implementation of national programs and its own mobile source programs and initiatives. |
Additional Information
Technical Report for School: Assessing Outdoor Air Near Schools: Concord Elementary School (Seattle, WA) (PDF) (39pp, 769k). The technical report is geared toward risk assessors, risk managers, and other regulatory agencies.
Background on School Monitoring Effort