New risk assessment advice for tDCE

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New risk assessment advice for tDCE

The Minnesota Department of Health (MDH) recently completed an updated evaluation of the existing air risk assessment advice (RAA) for trans-1,2-dichloroethylene (tDCE), which was developed specifically for the Water Gremlin site. The updated evaluation incorporated improvements in modeling of the study data used to develop the RAA, resulting in a change to the air RAA for tDCE.

The RAA set in 2019 was 70 micrograms per cubic meter (µg/m3) of air. This was a level determined to be safe for long-term exposure. The new RAA has values for two exposure durations: a chronic (up to a lifetime) value of 20 µg/m3 and a subchronic (up to 8 years) value of 200 µg/m3. For an MDH information sheet and toxicological summary that describes the updated RAA, please see the MDH Air Guidance Values Table.

MDH conducts chemical updates to keep existing air guidance values up-to-date with the most recent MDH risk assessment methodology and available science. Incorporating new data and methodologies may result in changes to existing air guidance values.

MDH has added a new document in the Water Gremlin Health Assessment Series: trans-1,2-Dichloroethylene in Air and Health, to their Water Gremlin webpage. This document describes how MDH uses tDCE toxicology studies and risk assessment to develop air guidance values, the Water Gremlin tDCE air monitoring data, and MDH’s conclusions about Water Gremlin’s tDCE emissions and health risk.

As part of enforcement actions, the MPCA issued an Administrative Order controlling Water Gremlin’s tDCE emissions in 2019. While the new RAA numbers may result in changes to how much tDCE Water Gremlin will be allowed to emit, MDH does not expect health effects to occur in the community from Water Gremlin’s past or current level of tDCE emissions. (Current average levels are less than the subchronic risk assessment advice.) Water Gremlin’s new permit will require keeping future emissions below the revised chronic level.

MPCA ordered Water Gremlin to monitor tDCE at five locations around Water Gremlin when the facility began using it in January 2019, and the MPCA added monitoring at two more locations farther out in the community. The monitoring data can be viewed here.

MPCA will evaluate how the new risk assessment advice numbers affect the new Water Gremlin permit currently in development. Future tDCE emissions will be limited as appropriate for protection of human health. The need for future tDCE monitoring around the facility is being evaluated as part of the permit process, and MPCA will hold Water Gremlin accountable for any new limits that may be imposed.

For more information

MPCA and MDH will provide further updates as new information becomes available.  If you’d like to speak with staff at either agency, contact:

MPCA: 651-757-2998 (leave a message for callback) or

MDH: 651-201-4897 (leave a message for callback) or