NYSDOH Revises Vapor Intrusion Guidance to Add Volatile Petroleum Compounds

In February 2024, the New York State Department of Health (NYSDOH) updated the decision matrices to its “Guidance for Evaluating Soil Vapor Intrusion in the State of New York” (” VI Guidance) to  include 13 volatile petroleum  compounds .  Previously, the NYSDOH decision matrices only assessed potential human health risks for contaminated vapors associated with chlorinated solvents.

The decision matrices are risk management tools used to evaluate sampling results for buildings with full slab foundations. The decision matrices  establish  ranges of sub-slab air concentrations and indoor air concentrations that may require mitigation, monitoring or do not require any action.  The sub-slab concentrations are displayed vertically while the indoor air concentrations are displayed horizontally. The decision matrices are discussed in section 3.4 of the NYSDOH VI Guidance and available HERE.

When it issued its 2006 VI guidance,  NYSDOH developed two decision matrices-  one for Trichloroethene (“TCE”) and the second for Tetrachloroethene (“PCE”). In 2013, NYSDOH amended table 3.1 of the VI Guidance to lower the PCE air guidance values from 100 micrograms per cubic meter (mcg/m3) to 30 mcg/m3 and lowered the recommended immediate action level from 1000 mcg/m3 to 300 mcg/m3. Corresponding changes were made to then Matrix 2 (now Matrix B).  In 2015, NYSDOH again amended table 3.1 to lower  the air guidance value for TCE from 5 mcg/m3 to 2 mcg/m3 and developed a recommended immediate action level of 20 mcg/m3. Corresponding changes were made to then Matrix 1 (now Matrix A)

In 2017, NYSDOH added NYSDOH a third matrix and assigned eight volatile chemicals to three newly revised matrices. The decision matrices were renamed the Soil Vapor/Indoor Air Decision Matrices and numbering was changed to lettering. Matrix A covered TCE, cis-1,2-Dichloroethene (c12-DCE), 1,1-Dichloroethene (11-DCE), and Carbon Tetrachloride. Matrix B covered PCE, 1,1,1-Trichloroethane (111-TCA), Methylene Chloride. Matrix C was limited to vinyl chloride. More information about the 2017 updates is available HERE:

Because these three matrices were limited to chlorinated solvents, it was difficult for building owners and residents to evaluate risks posed by petroleum vapors  arising from leaks from gasoline tanks or the many fuel oil tanks that are used to heat thousands of multi-family buildings in New York City.  With its February 2024, NYSDOH is attempting to fill this gap by creating three new decision matrices and assigning action values for 13 petroleum volatile compounds.

Matrix D applies to benzene, ethylbenzene, naphthalene, cyclohexane, isooctane (2,2,4-trimethylpentane), 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, o-xylene. The sub-slab action levels range from below 60, 60 to 6000 and above 6000 mcg/m3. The indoor air values range from below 2, 2 to below 10 and 10 or above mcg/m3.

Matrix E applies to m-xylene, p-xylene, heptane, hexane. The sub-slab values range from 200, 200 to 2000 and above 2000 mcg/m3. he indoor air values range from below 6, 6 to below 20 and 20 or above mcg/m3.

Air Matrix F  applies to Toluene.  The sub-slab values range from 300, 300 to 3000 and above 3000 mcg/m3. he indoor air values range from below 10, 10 to below 50 and 50 or above mcg/m3.

The six decision matrices may be viewed HERE

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