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1.
Risk Anal ; 24(1): 73-85, 2004 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-15028002

RESUMO

Assessments of aggregate exposure to pesticides and other surface contamination in residential environments are often driven by assumptions about dermal contacts. Accurately predicting cumulative doses from realistic skin contact scenarios requires characterization of exposure scenarios, skin surface loading and unloading rates, and contaminant movement through the epidermis. In this article we (1) develop and test a finite-difference model of contaminant transport through the epidermis; (2) develop archetypal exposure scenarios based on behavioral data to estimate characteristic loading and unloading rates; and (3) quantify 24-hour accumulation below the epidermis by applying a Monte Carlo simulation of these archetypal exposure scenarios. The numerical model, called Transient Transport through the epiDERMis (TTDERM), allows us to account for variable exposure times and time between exposures, temporal and spatial variations in skin and compound properties, and uncertainty in model parameters. Using TTDERM we investigate the use of a macro-activity parameter (cumulative contact time) for predicting daily (24-hour) integrated uptake of pesticides during complex exposure scenarios. For characteristic child behaviors and hand loading and unloading rates, we find that a power law represents the relationship between cumulative contact time and cumulative mass transport through the skin. With almost no loss of reliability, this simple relationship can be used in place of the more complex micro-activity simulations that require activity data on one- to five-minute intervals. The methods developed in this study can be used to guide dermal exposure model refinements and exposure measurement study design.


Assuntos
Poluentes Ambientais/toxicidade , Modelos Biológicos , Pele/efeitos dos fármacos , Criança , Comportamento Infantil , Difusão , Poluentes Ambientais/administração & dosagem , Poluentes Ambientais/farmacocinética , Mãos , Humanos , Método de Monte Carlo , Praguicidas/farmacocinética , Praguicidas/toxicidade , Medição de Risco , Pele/metabolismo , Propriedades de Superfície
2.
Environ Health Perspect ; 108(6): 475-86, 2000 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10856019

RESUMO

We review the factors influencing children's exposure to environmental contaminants and the data available to characterize and assess that exposure. Children's activity pattern data requirements are demonstrated in the context of the algorithms used to estimate exposure by inhalation, dermal contact, and ingestion. Currently, data on children's exposures and activities are insufficient to adequately assess multimedia exposures to environmental contaminants. As a result, regulators use a series of default assumptions and exposure factors when conducting exposure assessments. Data to reduce uncertainty in the assumptions and exposure estimates are needed to ensure chemicals are regulated appropriately to protect children's health. To improve the database, advancement in the following general areas of research is required: identification of appropriate age/developmental benchmarks for categorizing children in exposure assessment; development and improvement of methods for monitoring children's exposures and activities; collection of activity pattern data for children (especially young children) required to assess exposure by all routes; collection of data on concentrations of environmental contaminants, biomarkers, and transfer coefficients that can be used as inputs to aggregate exposure models.


Assuntos
Proteção da Criança , Exposição Ambiental , Xenobióticos/efeitos adversos , Administração Cutânea , Administração Oral , Adolescente , Algoritmos , Biomarcadores/análise , Criança , Pré-Escolar , Bases de Dados Factuais , Humanos , Lactente , Recém-Nascido , Exposição por Inalação
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