RESUMEN
While microplastics are a pollutant of growing concern in various environmental compartments, less is known regarding the sources and delivery pathways of microplastics in urban rivers. We investigated the relationship between microplastic concentrations and various spatiotemporal factors (e.g., land use, arterial road length, water velocity, precipitation) in two watersheds along an urban-rural gradient in the Portland metropolitan area. Samples were collected in August, September, and February and were analyzed for total microplastic count and type. Nonparametric statistics were used to evaluate potential relationships with the explanatory variables, derived at both the subwatershed and near stream scales. In August, microplastic concentrations were significantly higher than in February. August concentrations also negatively correlated with flow rate, suggesting that lower flow rates may have facilitated the accumulation of microplastics. Smaller size microplastic particles (< 100 µm) were found more in August than September and February, while larger size particles were more dominant in February than the other months. Microplastic concentrations were positively related to 24-h antecedent precipitation in February. Negative correlations existed between wet season microplastic concentrations and agricultural lands at the near stream level. The results indicate that near stream variables may more strongly influence the presence and abundance of microplastics in Portland's waterways than subwatershed-scale variables. Fragments were the most commonly observed microplastic morphology, with a dominance of gray particles and the polymer polyethylene. The findings of this study can inform management decisions regarding microplastic waste and identify hotspots of microplastic pollution that may benefit from remediation.
Asunto(s)
Microplásticos , Contaminantes Químicos del Agua , Ecosistema , Monitoreo del Ambiente , Agua Dulce , Plásticos , Polietileno , Ríos , Contaminantes Químicos del Agua/análisisRESUMEN
This paper presents the development of an occupational exposure level (OEL) for n-propylbromide (nPB) using benchmark dose methods. nPB is a non-ozone depleting solvent, proposed under the Significant New Alternatives Policy (SNAP) for use as a precision vapor degreaser. OELs have generally been developed on the basis of a NOAEL or LOAEL and application of uncertainty factors; this paper represents a departure from historic methods. Six recently completed toxicological studies were critically reviewed to identify (1) toxicologically significant endpoints, (2) dose-response information on these endpoints, and (3) uncertainties and limitations associated with the studies. Dose-response data were compiled and entered into the USEPA's benchmark dose software for calculation of a benchmark dose (BMD) and a benchmark dose low (BMDL). Once values were estimated for all relevant studies, they were then incorporated into a weight-of-evidence approach to develop a single BMD and BMDL representative of nPB. This approach is similar to that recently taken by USEPA to develop their own recommended OEL for nPB. USEPA's approach is compared and contrasted with ours, particularly in relation to the application of uncertainty factors (UFs) to generate a final OEL. There are no published criteria for application of UFs in developing an OEL. Although USEPA recommends utilizing a UF of 9, based on intraspecies variability and pharmacokinetic differences between rats and humans, to meet the goal of protecting healthy adult in a workplace setting, no uncertainty factor was deemed necessary for nPB in this paper. Therefore, the BMDL was recommended as the OEL.
Asunto(s)
Benchmarking/métodos , Exposición Profesional/normas , Valores Limites del Umbral , Animales , Atmósfera/análisis , Benchmarking/normas , Relación Dosis-Respuesta a Droga , Humanos , Hidrocarburos Bromados/análisis , Hidrocarburos Bromados/normas , Hidrocarburos Bromados/toxicidad , Exposición Profesional/prevención & control , Medición de Riesgo/métodos , Solventes/análisis , Pruebas de Toxicidad/métodos , Incertidumbre , Estados Unidos , United States Environmental Protection Agency/organización & administración , United States Environmental Protection Agency/normasRESUMEN
Is your hospital getting ready for the Joint Commission's core measures project? Some hospitals are already transmitting the necessary data as part of the pilot project. Here's how they are handling the challenges and deriving benefits.