Radiological HEPA Filter 10-year Lifetime Evaluation in Research Facilities.

ABSTRACT: High-efficiency particulate air (HEPA) filters are widely employed by nuclear facilities to remove radiological particulate matter from their effluent exhaust streams. The purpose of this study is to evaluate the relationships between the 10-y HEPA filter lifetime deployment and its other performance indicators. This 10-y-long endeavor to collect and analyze data regarding the service life of HEPA filters at the Pacific Northwest National Laboratory began in 2010. A set of HEPA filters was selected, and the filters have been surveyed and analyzed at least annually to verify compliance with permit conditions. The study suggests the frequency of filter replacement should be based on the actual operational requirements, such as fume hood face velocity and/or efficiency test results, instead of on the prescribed filter "age limit" of 10 y from the date of manufacture (e.g., birth date) when operating under dry conditions. The study has now been completed, and over the past decade, all the HEPA filters have been replaced due to either technical issues as listed in this report or the previously recommended filter "age limit" of 10 y as prescribed by the oversight bodies. Experimentally determined failure rates are also determined from the data set and can be used to estimate the chances of HEPA filters surviving 15, 20, or even 30 y.

A multistep enrichment process with custom growth medium improves resuscitation of chlorine-stressed coliforms from secondary sewage effluents.

Resuscitation and detection of stressed total coliforms in chlorinated water samples is needed to assess and prevent health effects from adverse exposure. In this study, we report that the addition of a growth enhancer mix consisting of trehalose, sodium pyruvate, magnesium chloride, and 1× trace mineral supplement improved growth of microorganisms from chlorinated secondary effluent in the base medium with Colilert-18. Improving growth of chlorine stressed microorganisms from secondary effluent is crucial to decreased detection time from 18 to 8 h.

Cells Respond to Distinct Nanoparticle Properties with Multiple Strategies As Revealed by Single-Cell RNA-Seq.

The impact of distinct nanoparticle (NP) properties on cellular response and ultimately human health is unclear. This gap is partially due to experimental difficulties in achieving uniform NP loads in the studied cells, creating heterogeneous populations with some cells "overloaded" while other cells are loaded with few or no NPs. Yet gene expression studies have been conducted in the population as a whole, identifying generic responses, while missing unique responses due to signal averaging across many cells, each carrying different loads. Here, we applied single-cell RNA-Seq to alveolar epithelial cells carrying defined loads of aminated or carboxylated quantum dots (QDs), showing higher or lower toxicity, respectively. Interestingly, cells carrying lower loads responded with multiple strategies, mostly with up-regulated processes, which were nonetheless coherent and unique to each QD type. In contrast, cells carrying higher loads responded more uniformly, with mostly down-regulated processes that were shared across QD types. Strategies unique to aminated QDs showed strong up-regulation of stress responses, coupled in some cases with regulation of cell cycle, protein synthesis, and organelle activities. In contrast, strategies unique to carboxylated QDs showed up-regulation of DNA repair and RNA activities and decreased regulation of cell division, coupled in some cases with up-regulation of stress responses and ATP-related functions. Together, our studies suggest scenarios where higher NP loads lock cells into uniform responses, mostly shutdown of cellular processes, whereas lower loads allow for unique responses to each NP type that are more diversified proactive defenses or repairs of the NP insults.