Browsing by Author "Davis, Katherine"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Results from Screening Polyurethane Foam Based Consumer Products for Flame Retardant Chemicals: Assessing Impacts on the Change in the Furniture Flammability Standards.
    (Environmental science & technology, 2016-10) Cooper, Ellen M; Kroeger, Gretchen; Davis, Katherine; Clark, Charlotte R; Ferguson, P Lee; Stapleton, Heather M
    Flame retardant (FR) chemicals have often been added to polyurethane foam to meet required state and federal flammability standards. However, some FRs (e.g., PBDEs and TDCIPP) are associated with health hazards and are now restricted from use in some regions. In addition, California's residential furniture flammability standard (TB-117) has undergone significant amendments over the past few years, and TDCIPP has been added to California's Proposition 65 list. These events have likely led to shifts in the types of FRs used, and the products to which they are applied. To provide more information on the use of FRs in products containing polyurethane foam (PUF), we established a screening service for the general public. Participants residing in the US were allowed to submit up to 5 samples from their household for analysis, free of charge, and supplied information on the product category, labeling, and year and state of purchase. Between February 2014 and June 2016, we received 1141 PUF samples for analysis from various products including sofas, chairs, mattresses, car seats and pillows. Of these samples tested, 52% contained a FR at levels greater than 1% by weight. Tris(1,3-dichloroisopropyl)phosphate (TDCIPP) was the most common FR detected in PUF samples, and was the most common FR detected in all product categories. Analysis of the data by purchasing date suggests that the use of TDCIPP decreased in recent years, paralleled with an increase in the use of TCIPP and a nonhalogenated aryl phosphate mixture we call "TBPP." In addition, we observed significant decreases in FR applications in furniture products and child car seats, suggesting the use of additive FRs in PUF may be declining, perhaps as a reflection of recent changes to TB-117 and Proposition 65. More studies are needed to determine how these changes in FR use relate to changes in exposure among the general population.
  • Thumbnail Image
    ItemOpen Access
    The Role of Phylogeny in Associations Between Marine Phytoplankton and Heterotrophic Bacteria
    (2014) Davis, Katherine

    Empirical studies show coupling between phytoplankton and heterotrophic bacterioplankton across marine ecosystems through correlations between bacterial cell abundances and bulk phytoplankton measurements of chlorophyll-a or primary production. However, it is still not known whether associations between heterotrophic and autotrophic microbes are mediated solely through bulk carbon pools or if specific cellular interactions are involved. We examined the coupling of heterotrophic bacteria and specific phytoplankton populations in a dynamic, coastal ecosystem and explored the phylogenetic diversity of heterotrophic bacteria associated with a model phytoplankton taxon. Using flow cytometry to count distinct microbial groups, we found heterotrophic bacteria and phytoplankton abundances exhibit similar seasonal dynamics at the coastal sampling site, indicative of close coupling between these organisms. Heterotrophic bacterial abundances were more tightly correlated with small eukaryotic phytoplankton than either cyanobacteria group, Prochlorococcus or Synechococcus. Given our finding that associations between bacteria and eukaryotic phytoplankton drive ecologically important heterotroph-phytoplankton coupling, we examined the community composition of heterotrophic bacteria in culture with a model diatom, Thalassiosira rotula using 16S rRNA gene sequencing. Results indicate that strains of T. rotula support unique heterotrophic bacterial taxa but that all T. rotula also associate with a common set of bacterial phylotypes, comprised of members of the Alphaproteobacteria. Characterizing the phylogenetic associations between heterotrophic bacteria and phytoplankton is essential for identifying factors shaping phytoplankton-bacteria interactions and their role in organic matter processing, trophic dynamics and biogeochemical cycles in marine ecosystems.