39 research outputs found
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From pesticide degradation products to legacy toxicants and emerging contaminants : novel analytical methods, approaches, and modeling
Environmental toxicologists and public health officials are responsible for assisting in the identification, management, and mitigation of public health hazards. As a result, there is a continued need for robust analytical tools that can aid in the rapid quantification and characterization of chemical exposure. In the first research phase, we demonstrated that a current tool for estimating human organophosphate pesticide exposure, measuring dialkyl phosphate (DAPs) metabolites in urine as chemical biomarkers of pesticide exposure, could represent exposure to DAPs themselves and not to pesticides. We showed that DAPs are metabolically stable, have high oral bioavailability, and are rapidly excreted in the urine following oral exposure. Results suggest that DAP measurements may lead to overestimates of human organophosphate pesticide exposure.
In the second phase of research, a quick, easy, cheap, effective, rugged, and safe (QuEChERS) based analytical method was developed and validated for quantifying polycyclic aromatic hydrocarbons (PAHs) in biotic matrices with fat contents that ranged from 3 to 11%. Our method improved PAH recoveries 50 to 200% compared to traditional QuEChERS methods, performed as well or better than state of the art Soxhlet and accelerated solvent extraction methods, had sensitivity useful for chemical exposure assessments, and reduced sample preparation costs by 10 fold. The validated QuEChERS method was subsequently employed in a human exposure assessment.
Little is known about how traditional Native American fish smoke-preserving methods impact PAH loads in smoked foods, Tribal PAH exposure, or health risks. Differences in smoked salmon PAH loads were not observed between Tribal smoking methods, where smoking methods were controlled for smoking structure and smoke source. PAH loads in Tribally smoked fish were up to 430 times greater than those measured in commercially available smoked fish. It is not likely that dietary exposure to non-carcinogenic PAHs at heritage ingestion rates of 300 grams per day poses an appreciable risk to human health. However, levels of PAHs in traditionally smoked fish may pose and elevated of risk of cancer if consumed at high rates over a life time.
Accurately estimating PAH exposure in cases where aquatic foods become contaminated is often hindered by sample availability. To overcome this challenge, we developed a novel analytical approach to predict PAH loads in resident crustacean tissues based on passive sampling device (PSD) PAH measurements and partial least squares regression. PSDs and crayfish collected from 9 sites within, and outside of, the Portland Harbor Superfund site captured a wide range of PAH concentrations in a matrix specific manner. Partial least squares regression of crayfish PAH concentrations on freely dissolved PAH concentrations measured by PSDs lead to predictions that generally differed by less than 12 parts per billion from measured values. Additionally, most predictions (> 90%) were within 3-fold of measured values, while state of the art bioaccumulation factor approaches typically differ by 5 to 15-fold compared to measured values.
In order to accurately characterize chemical exposure, new analytical approaches are needed that can simulate chemical changes in bioavailable PAH mixtures resulting from natural and/or remediation processes. An approach based on environmental passive sampling and in-laboratory UVB irradiation was developed to meet this need. Standard PAH mixtures prepared in-lab and passive sampling device extracts collected from PAH contaminated environments were used as model test solutions. UV irradiation of solutions reduced PAH levels 20 to 100% and lead to the formation of several toxic oxygenated-PAHs that have been previously measured in the environment. Site specific differences in oxygenated-PAH formation were also observed. The research presented in this dissertation can be used to advance chemical exposure estimation techniques, rapidly and cost-effectively quantify a suite of PAHs in biotic tissues, and simulate the effect of abiotic transformation processes on the bioavailable fraction of environmental contaminants
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Predicting Polycyclic Aromatic Hydrocarbon Concentrations in Resident Aquatic Organisms Using Passive Samplers and Partial Least-Squares Calibration
The current work sought to develop predictive
models between time-weighted average polycyclic aromatic
hydrocarbon (PAH) concentrations in the freely dissolved
phase and those present in resident aquatic organisms. We
deployed semipermeable membrane passive sampling devices
(SPMDs) and collected resident crayfish (Pacifastacus
leniusculus) at nine locations within and outside of the
Portland Harbor Superfund Mega-site in Portland, OR.
Study results show that crayfish and aqueous phase samples
collected within the Mega-site had PAH profiles enriched in
high molecular weight PAHs and that freely dissolved PAH
profiles tended to be more populated by low molecular weight
PAHs compared to crayfish tissues. Results also show that of
several modeling approaches, a two-factor partial least-squares (PLS) calibration model using detection limit substitution
provided the best predictive power for estimating PAH concentrations in crayfish, where the model explained ≥72% of the
variation in the data set and provided predictions within ∼3× of measured values. Importantly, PLS calibration provided a means
to estimate PAH concentrations in tissues when concentrations were below detection in the freely dissolved phase. The impact of
measurements below detection limits is discussed
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Effect of Native American Fish Smoking Methods on Dietary Exposure to Polycyclic Aromatic Hydrocarbons and Possible Risks to Human Health
Although it is known that polycyclic aromatic hydrocarbons (PAHs) can be found in smoked meats, little is known about their prevalence in Native American smoked fish. In this work, the effect of traditional Native American fish smoking methods on dietary exposure to PAHs and possible risks to human health has been assessed. Smoking methods considered smoking structure (tipi or shed) and wood type (apple or alder). Neither smoking structure nor wood type accounted for differences in smoked salmon content of 33 PAHs. Carcinogenic and noncarcinogenic PAH loads in traditionally smoked salmon were 40–430 times higher than those measured in commercial products. Dietary exposure to PAHs could result in excess lifetime cancer risks between 1 × 10⁻⁵ and 1 × 10⁻⁴ at a daily consumption rate of 5 g d⁻¹ and could approach 1 × 10⁻² at 300 g d⁻¹. Hazard indexes approached 0.005 at 5 g d⁻¹, or approximately 0.3 at 300 g d⁻¹. Levels of PAHs present in smoked salmon prepared using traditional Native American methods may pose elevated cancer risks if consumed at high consumption rates over many years.Keywords: food safety, smoked fish, relative potency factor, risk assessment, Native AmericanKeywords: food safety, smoked fish, relative potency factor, risk assessment, Native America
Progress report no. 2
Statement of responsibility on title-page reads: Editors: I.A. Forbes, M.J. Driscoll, N.C. Rasmussen, D.D. Lanning and I. Kaplan; Contributors: S.T. Brewer, G.J. Brown, P.DeLaquil, III, M.J. Driscoll, I.A. Forbes, C.W. Forsberg, E.P. Gyftopoulos, P.L. Hendrick, C.S. Kang, I. Kaplan, J.L. Klucar, D.D. Lanning, T.C. Leung, E.A. Mason, N.R. Ortiz, N.A. Passman, N.C. Rasmussen, I.C. Rickard, V.C. Rogers, G.E. Sullivan, A.T. Supple, and C. P. TzanosIncludes bibliographical referencesProgress report; June 30, 1971U.S. Atomic Energy Commission contract AT(11-1)306
Progress report no. 1
Statement of responsibility on title-page reads: Editors: I.A. Forbes, M.J. Driscoll, D.D. Lanning, I. Kaplan, N.C. Rasmussen; Contributors: S.A. Ali, S.T. Brewer, D.K. Choi, F.M. Clikeman, W.R. Corcoran, M.J. Driscoll, I.A. Forbes, C.W. Forsberg, S.L. Ho, C.S. Kang, I. Kaplan, J.L. Klucar, D.D. Lanning, T.C. Leung, E.L. McFarland P.G. Mertens, N.R. Ortiz, A. Pant, N.A. Passman, N.C. Rasmussen, M.K. Sheaffer, D.A. Shupe, G.E. Sullivan, A.T. Supple, J.W. Synan, C.P. Tzanos, W.J. Westlake"MIT-4105-3."Includes bibliographical referencesProgress report; June 30, 1970U.S. Atomic Energy Commission contracts: AT(30-1)410
Broad host range plasmids can invade an unexpectedly diverse fraction of a soil bacterial community
Conjugal plasmids can provide microbes with full complements of new genes and constitute potent vehicles for horizontal gene transfer. Conjugal plasmid transfer is deemed responsible for the rapid spread of antibiotic resistance among microbes. While broad host range plasmids are known to transfer to diverse hosts in pure culture, the extent of their ability to transfer in the complex bacterial communities present in most habitats has not been comprehensively studied. Here, we isolated and characterized transconjugants with a degree of sensitivity not previously realized to investigate the transfer range of IncP- and IncPromA-type broad host range plasmids from three proteobacterial donors to a soil bacterial community. We identified transfer to many different recipients belonging to 11 different bacterial phyla. The prevalence of transconjugants belonging to diverse Gram-positive Firmicutes and Actinobacteria suggests that inter-Gram plasmid transfer of IncP-1 and IncPromA-type plasmids is a frequent phenomenon. While the plasmid receiving fractions of the community were both plasmid- and donor- dependent, we identified a core super-permissive fraction that could take up different plasmids from diverse donor strains. This fraction, comprising 80% of the identified transconjugants, thus has the potential to dominate IncP- and IncPromA-type plasmid transfer in soil. Our results demonstrate that these broad host range plasmids have a hitherto unrecognized potential to transfer readily to very diverse bacteria and can, therefore, directly connect large proportions of the soil bacterial gene pool. This finding reinforces the evolutionary and medical significances of these plasmids.Fil: Klumper, Uli. Technical University of Denmark; DinamarcaFil: Riber, Leise. Universidad de Copenhagen; DinamarcaFil: Dechesne, Arnaud. Technical University of Denmark; DinamarcaFil: Sannazzaro, Analía Inés. Universidad de Copenhagen; DinamarcaFil: Hansen, Lars H.. Universidad de Copenhagen; Dinamarca. Aarhus University. Roskilde; DinamarcaFil: Sørensen, Søren. Universidad de Copenhagen; DinamarcaFil: Smets, Barth F. Technical University of Denmark; Dinamarc
Defining the effect and mediators of two knowledge translation strategies designed to alter knowledge, intent and clinical utilization of rehabilitation outcome measures: a study protocol [NCT00298727]
BACKGROUND: A substantial number of valid outcome measures have been developed to measure health in adult musculoskeletal and childhood disability. Regrettably, national initiatives have merely resulted in changes in attitude, while utilization remains unacceptably low. This study will compare the effectiveness and mediators of two different knowledge transfer (KT) interventions in terms of their impact on changing knowledge and behavior (utilization and clinical reasoning) related to health outcome measures. METHOD/DESIGN: Physical and occupational therapists (n = 144) will be recruited in partnership with the national professional associations to evaluate two different KT interventions with the same curriculum: 1) Stakeholder-Hosted Interactive Problem-Based Seminar (SHIPS), and 2) Online Problem-Based course (e-PBL). SHIPS will consist of face-to-face problem-based learning (PBL) for 2 1/2 days with outcome measure developers as facilitators, using six problems generated in consultation with participants. The e-PBL will consist of a 6-week web-based course with six generic problems developed by content experts. SHIPS will be conducted in three urban centers in Canada. Participants will be block-allocated by a minimization procedure to either of the two interventions to minimize any prognostic differences. Trained evaluators at each site will conduct chart audits and chart-stimulated recall. Trained interviewers will conduct semi-structured interviews focused on identifying critical elements in KT and implementing practice changes. Interviews will be transcribed verbatim. Baseline predictors including demographics, knowledge, attitudes/barriers regarding outcome measures, and Readiness to Change will be assessed by self-report. Immediately post-intervention and 6 months later, these will be re-administered. Primary qualitative and quantitative evaluations will be conducted 6-months post-intervention to assess the relative effectiveness of KT interventions and to identify elements that contribute to changing clinical behavior. Chart audits will determine the utilization of outcome measures (counts). Incorporation of outcome measures into clinical reasoning will be assessed using an innovative technique: chart-stimulated recall. DISCUSSION: A strategy for optimal transfer of health outcome measures into practice will be developed and shared with multiple disciplines involved in primary and specialty management of musculoskeletal and childhood disability
Owner-Level Taxes and Business Activity
In some classes of models, taxes at the owner level are "neutral" and have no effect on firm activity. However, this tax neutrality is sensitive to assumptions and no longer holds in more complex models. We review recent research that incorporates greater complexity in studying the link between taxes and business activity - particularly entrepreneurship. Dividend taxes on owners of large firms affect firm activity in models that include agency conflicts between owners and managers. Similarly, after incorporating entrepreneurs' occupational choice into the model, taxes are no longer neutral. By forsaking lucrative alternative careers, skilled entrepreneurs tend to have high opportunity costs, which make the choice of attempting to start a business of first order importance. Moreover, in models where it is assumed that capital flows across borders without cost, taxes on domestic business owners do not alter business activity because foreign capital seamlessly compensates for tax-induced declines in investments. This theoretical notion is contradicted by the strong "home bias" observed in business ownership, in particular for small firms and startups without easy access to international capital markets. Recent empirical work has emphasized that taxes have heterogeneous effects on mature firms, entrepreneurial startups, and owner-managed small firms. Lowering dividend taxes on firms with dispersed ownership has been shown to shift capital from mature firms into rapidly growing firms. Moreover, capital gains taxation tends to reduce the number of innovative startups and diminish venture capital activity, while high owner-level taxes encourage small business activity and non-entrepreneurial self-employment because such firms have more opportunities to avoid or evade taxes. To obtain efficient incentives in entrepreneurial startups, contractual terms are required that ex ante guarantee that all providers of critical inputs, especially equity constrained entrepreneurs, are entitled to a share of the resulting capital value firm. Unless properly designed, owner-level taxes prevent such ex ante contracting and thus lower the likelihood of eventual success
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ForsbergNormanEMTPredictingPolycyclicAromatic.pdf
The current work sought to develop predictive
models between time-weighted average polycyclic aromatic
hydrocarbon (PAH) concentrations in the freely dissolved
phase and those present in resident aquatic organisms. We
deployed semipermeable membrane passive sampling devices
(SPMDs) and collected resident crayfish (Pacifastacus
leniusculus) at nine locations within and outside of the
Portland Harbor Superfund Mega-site in Portland, OR.
Study results show that crayfish and aqueous phase samples
collected within the Mega-site had PAH profiles enriched in
high molecular weight PAHs and that freely dissolved PAH
profiles tended to be more populated by low molecular weight
PAHs compared to crayfish tissues. Results also show that of
several modeling approaches, a two-factor partial least-squares (PLS) calibration model using detection limit substitution
provided the best predictive power for estimating PAH concentrations in crayfish, where the model explained ≥72% of the
variation in the data set and provided predictions within ∼3× of measured values. Importantly, PLS calibration provided a means
to estimate PAH concentrations in tissues when concentrations were below detection in the freely dissolved phase. The impact of
measurements below detection limits is discussed