MassDEP explains VOC monitoring, dashboard tools and data access

The Massachusetts Department of Environmental Protection on a public instructional video explained how it monitors volatile organic compounds, or VOCs, and how residents and researchers can use the agency—s VOC dashboard to view and download data.

VOCs are pollutants that can be present in air, water and soil and may come from fossil fuel combustion, manufacturing, commercial and household products, and natural sources. The presenter cited common examples including benzene and formaldehyde.

MassDEP monitors VOCs at four sites — Boston, Chelsea, Lynn and Weymouth — using 24-hour air samples collected every six days at each site. The agency said valid regulatory data are submitted to the U.S. Environmental Protection Agency—s Air Quality System (AQS). The dashboard is intended to display both valid and void samples for informational purposes.

The video demonstrates dashboard features: use the Sample Date slider or the calendar icon to choose start and end dates; use the VOC name box to select a single VOC to view (only one VOC can be viewed at a time); and use the site box or the map to filter by monitoring location (control-click to select multiple sites). Data can be displayed as individual sample dates, monthly averages or annual averages via the time-interval selector. MassDEP instructs users to ensure an entire month or year is included in the sample date range before relying on monthly or annual averages.

MassDEP explains that some samples may be classified as void for technical reasons and that monthly and annual averages shown on the dashboard are based on the selected date range and on the samples designated valid. Users may toggle the display of void data on or off. The video walks through how to download graph data (monthly and annual averages) and table data (individual samples) as CSV files using the dashboard—s —more options— menu, and how to reset filters with the —clear all filters— button.

The dashboard includes an air-guidelines box that displays MassDEP—s effects exposure limits (TELs) and allowable ambient limits (AALs) when a selected VOC has an associated guideline. The presenter said that if any sample in the displayed date range exceeds a TEL, an indicator line will appear on the graph. Technical detail and methodology are available in the dashboard—s Information and Disclaimers and How to Use tabs.

The presenter also noted an AQS codes tab that lists state, county, site and VOC parameter codes needed to retrieve data from EPA—s AQS and closed by providing a contact for further information: Sean Dunn, deputy division director of the Air Assessment Branch.

For more information, MassDEP directs users to the VOC dashboard and to EPA—s AQS at epa.gov/aqs.