Preliminary Release of Microbial and Disinfection Byproduct Data Files (2012-2019) from EPA’s Fourth Six-Year Review Information Collection Request

As a result of EPA’s third Six-Year Review (SYR3) of the National Primary Drinking Water Regulations (NPDWRs), EPA identified eight contaminants covered by the Microbial and Disinfection Byproducts (MDBP) rules as candidates for revision. EPA is currently conducting analyses with relevant data and information (including characterization of national baselines after implementation of MDBP rules) to further evaluate the eight NPDWRs for potential regulatory revisions.

In support of conducting these analyses, in August 2022 EPA did a preliminary release of the MDBP-related data that were collected under the fourth Six-Year Review (SYR4) Information Collection Request (ICR). The released datasets contain compliance monitoring data and treatment technique information from January 2012 to December 2019, voluntarily provided by states and primacy agencies.

The preliminary release of SYR4's MDBP data files ahead of the publication of SYR4 results allows access to these data prior to the publication of EPA's SYR decisions. In particular, these MDBP compliance data could help inform analyses related to the potential revisions of the MDBP rules. The other data elements (e.g., those related to chemical phase rules) from the SYR4 ICR will be released along with the publication when the SYR4 is completed. The SYR4 data files released in August 2022 have undergone a rigorous Quality Assurance/Quality Control (QA/QC) review and are believed to be accurate. EPA has updated the preliminary release files to allow for compatibility with previous Six-Year Review data. The updated files include a field to identify the location of tribal systems, as was included in previous SYR data files.

You can see the updated data files here.

Each zip file below includes data for multiple contaminants and related information. The number of records and associated systems in the data files and the size of the files range considerably from contaminant to contaminant, which may be attributed to many factors such as the applicability of monitoring requirements (e.g., required sampling frequencies and locations), results from QA/QC measures, and completeness of data records.

The Data Management and Quality Assurance/Quality Control Process for EPA’s Fourth Six-Year Review’s Microbial and Disinfection Byproduct Preliminary Datasets contains a detailed description of each of these datasets (including the data fields, definitions, and associated QA/QC) and instructions for downloading and importing datasets into common analytical software applications such as Excel, Access, or R.

View the document here:

The Data Management and Quality Assurance/Quality Control Process for EPA’s Fourth Six-Year Review’s Microbial and Disinfection Byproduct Preliminary Datasets (pdf) (1.33 MB, August 2022, EPA- 810-R-22-001)