MassDEP monitors volatile organic compounds (VOCs) in Boston (Roxbury), Chelsea, Lynn, and Weymouth as shown on the map below. VOCs can contribute to ozone formation and some VOCs are toxic and can adversely affect human health and the environment. VOCs are ubiquitous in the environment because they are emitted by fossil fuel combustion (e.g., cars and trucks, power plants, homes and businesses), manufacturing processes (e.g., solvents), commercial and household products (e.g., paints, cleaners), and by natural sources (e.g., vegetation, forest fires).
MassDEP collects 24-hour air samples every 6 days at each of its VOC monitoring sites. MassDEP uses canisters to collect samples for most VOCs (e.g., benzene, toluene, 1,3-butadiene), and sends the samples to the Rhode Island State Health Laboratory for analysis. MassDEP uses cartridges to collect samples of a subset of VOCs called carbonyls (e.g., formaldehyde and acetaldehyde) and analyzes these samples at MassDEP’s Wall Experiment Station laboratory. MassDEP posts the monitoring data results on a monthly basis (see spreadsheets below). MassDEP also submits the data to the U.S. Environmental Protection Agency’s (EPA) Air Quality System (AQS) database.
MassDEP VOC data are available in the dashboard and spreadsheets below. VOC data prior to February 2020 are available from EPA’s AQS database. A mobile view of the dashboard is also available.
VOC Data Summary Files
VOC Dashboard Resources
Additional Information
- MassDEP monitors volatile organic compounds (VOCs) at 4 locations: Boston (Roxbury), Chelsea, Lynn, and Weymouth. (The Weymouth site moved from Bridge Street to Monatiquot Street in April 2021.)
- A 24-hour canister sample for 60 VOCs and a carbonyl cartridge sample for 5 carbonyls is taken every 6 days, with all sites on the same schedule. Samples on dates other than the scheduled run dates are typically make-up samples that are sometimes run in the event of a missed or voided sample.
- VOC canister samples are analyzed by the Rhode Island State Health Laboratories by 'VOCs by GCFID and GCMS' (i.e., modified EPA Method TO-15A).
- VOC carbonyl cartridge samples are analyzed by MassDEP’s Division of Environmental Laboratory Sciences by modified EPA Method TO-11A.
- All data displayed is in parts per billion (ppb).
- This dashboard displays VOC data from both the canister samples and the carbonyl cartridge samplers.
- The 5 carbonyls are formaldehyde, acetaldehyde, acetone, propionaldehyde, and benzaldehyde.
- Acetaldehyde and acetone are also measured in the VOC canister sample. Acetone and acetaldehyde measured from the carbonyl cartridge samples are labelled "(carbonyl)" in the parameter name.
- Acetaldehyde measured using the carbonyl cartridge sample method is the preferable sampling method. Therefore, applicable TEL/AAL values are listed only for the acetaldehyde (carbonyl) data.
- Freon-12, bromomethane and alpha-pinene were added to the list of VOCs analyzed in June 2020.
- Chloroprene and cis-1,2,-dichloroethene were removed from the list of VOCs analyzed in June 2020.
- C5-C8 aliphatics represents the sum total of pentane, hexane, heptane, octane, and 2,2,4-trimethylpentane measured on a sample day.
- Historically, 1-butene was deliberately introduced by the Rhode Island laboratory as a tracking compound to monitor the accuracy of the analytical procedure. 1-butene is not associated with the air sample being analyzed, and 1-butene values are not reported to AQS. In December 2023, the laboratory stopped reporting any values of 1-butene to MassDEP so it was removed from the VOC list.
TELs/AALs Notes
MassDEP uses Air Guidelines to evaluate potential health effects from breathing chemicals in the outdoor air. These guidelines are compared to long term average levels in the air. Each chemical has two Air Guideline values: a TEL and an AAL.
- TEL – Threshold Effects Exposure Limit. TELs are based on non-cancer health effects. The TEL is a level in the outdoor air that protects the general population, including sensitive people such as children, from adverse health effects over a lifetime of breathing the air every day for 24 hours a day. TELs consider that people may be exposed to a chemical from multiple sources, including indoor air, food, soil, and water.
- AAL – Ambient Air Limit. AALs are based on the TEL and the Non-Threshold Effects Exposure Limit (NTEL), a level associated with a one in one million excess lifetime cancer risk over a lifetime of breathing the air every day for 24 hours a day. The AAL is set at the lower of the NTEL or TEL value for a chemical. When a chemical does not pose a cancer risk, the AAL and the TEL are the same.
Exposure above an AAL or TEL does not mean an individual will develop cancer or experience health effects. However, the risk of developing health effects increases with the intensity and frequency of exposure.
TELs and AALs are developed by MassDEP.
If a VOC has a TEL or AAL, it will populate in the “Air Guidelines” box when the VOC is selected.
If any value in the dataset exceeds the TEL, a dotted line will appear on the graph to show the TEL in context.