EPA Region 7 Statement on Non-Targeted Air Monitoring Performed at and Near AltEn LLC Facility in Mead, Nebraska, on May 31 and June 1, 2022

(April 17, 2023) – The U.S. Environmental Protection Agency (EPA) provided preliminary, raw sample data to the Nebraska Department of Environment and Energy (NDEE) from its May 31 and June 1, 2022, non-targeted air sampling at and near the AltEn LLC ethanol facility (AltEn) in Mead, Nebraska. The preliminary data that was shared publicly via NDEE’s AltEn public information page is complex and requires context and careful consideration for appropriate use and interpretation.

Problem: Public concern over an odor and possible hazards originating from a closed ethanol production facility, AltEn, prompted the state of Nebraska to seek advice and technical assistance from EPA Region 7 (EPA R7). EPA R7 collected and analyzed air samples using targeted methods for volatile chemicals, some of which were known to cause odors. While some compounds were detected in this analysis, EPA R7 concluded that the concentrations were found to be below levels of concern surrounding the AltEn property.

Action: To understand what other chemicals might be present, EPA R7 began working with scientists in EPA’s Office of Research and Development (ORD) to employ a technique known as non-targeted analysis. Non-targeted analysis methods can detect chemicals that were not included in the original measurements. EPA R7 collected more air samples from various locations on the AltEn property and near the town of Mead, Nebraska, on May 31 and June 1, 2022. EPA R7 shipped the samples to an EPA research lab in Research Triangle Park, North Carolina, where ORD researchers analyzed them using non-targeted analysis methods.

Unlike the typical chemistry methods that are used to measure chemicals in the environment, non-targeted analysis is a new technique that allows researchers to detect chemicals that aren’t pre-selected for analysis. Non-targeted analysis methods can potentially detect many more chemicals compared to the typical chemistry methods; however, with more possible chemical detections, the chances of misidentifying chemicals become higher. Non-targeted analysis methods typically produce a list of candidate chemicals, which are then analyzed using the traditional chemistry methods in order to confirm the identifications. Non-targeted analysis also produces qualitative results, meaning that it provides a yes or no answer on whether the chemical was detected and does not measure chemical concentrations. The qualitative results limit their use in understanding human health risks. Understanding human health risks requires both measuring the air concentrations to which people are exposed and knowing the amount of the chemical required to cause adverse health effects.

Analysis: The goal of the non-targeted analysis study was to identify candidate chemicals (chemicals that might exist in the sample but are not confirmed) from the samples that were collected and prioritize some of the candidates for follow-up confirmation by traditional chemistry methods.

Non-targeted analysis works by matching chemical signatures from the samples to large databases containing thousands of chemical signatures to get potential matches. In many cases, the chemical signatures are not unique. Multiple candidates are often identified for each chemical signature, but only one chemical can be the correct one.

There are many ways researchers could reduce the number of candidates to focus on those that are likely correct and those that have a higher priority for confirmation. For this study, researchers first removed chemicals that may have been introduced during the shipping, storing, or laboratory processes. This was done by preparing laboratory samples that used the same sampling methods but were not exposed to any air. Candidate chemicals were removed if the strength of the signal was not significantly larger in the air samples taken from the AltEn site than in the laboratory samples not exposed to air. Researchers then focused on removing candidate chemicals that are not known to be hazardous or are known to have low toxicity. The reason for removing these chemicals was to prioritize those chemicals for confirmation which may pose human health risks regardless of their likelihood of being correct. However, in doing so, the list of candidate chemicals (posted to the state of Nebraska’s public records portal on April 7, 2023) knowingly contains multiple candidates for the same chemical signature, even though only one is correct, and the list of candidates contains more hazardous chemicals than are likely to exist in the air samples taken from the site.

Preliminary results: The preliminary results of this study show a successful application of non-targeted sampling and analysis, providing preliminary information on the mixture of chemicals in the air around the AltEn property and Mead, Nebraska. The identities of these chemicals have not been confirmed. Furthermore, this first analysis of the data did not attempt to determine the source of these chemicals. Therefore, the origin of the chemical signals could not be conclusively linked to the AltEn property.

Next steps: EPA will continue to work with the state of Nebraska to analyze these preliminary results and to determine if any additional sampling is needed. The next steps in this project are to explore alternative ways to reduce the number of candidates by trying to identify odor-causing chemicals and to use background air samples to determine which chemical signals are unique to the AltEn facility. After these types of further data analyses, candidate chemicals can be selected for confirmation studies. These next steps will likely take several months.

More information about the AltEn LLC Facility: NDEE is the lead regulatory agency overseeing the AltEn facility and has conducted numerous other sampling efforts, including groundwater, surface water, air, waste material, and soil. For current information on the AltEn LLC facility, please visit NDEE’s public information page: AltEn LLC Information and Updates.

EPA contact: Curtis Carey, Public Affairs Office, 913-551-7506, carey.curtis@epa.gov.