Dermal exposure methodology

Modeling Residential Re-entry Dermal Exposures 157 Integrated Physical-Stochastic Dermal Model 158 Macro-Based Dermal Exposure Methodology 159 Scenario 1 159... 

Micro-Based Dermal Exposure Methodology (SHEDS) 167 References 169... 

Estimates of exposure levels posing minimal risk to humans (Minimal Risk Levels or MRLs) have been made for methyl parathion. An MRL is defined as an estimate of daily human exposure to a substance that is likely to be without an appreciable risk of adverse effects (noncarcinogenic) over a specified duration of exposure. MRLs are derived when reliable and sufficient data exist to identify the target organ(s) of effect or the most sensitive health effect(s) for a specific duration within a given route of exposure. MRLs are based on noncancerous health effects only and do not consider carcinogenic effects. MRLs can be derived for acute, intermediate, and chronic duration exposures for inhalation and oral routes. Appropriate methodology does not exist to develop MRLs for dermal exposure. 

The first pesticide exposure study was reported by Griffiths et al. (1951). Parathion was trapped on respirator filter discs during application to citrus trees. Batchelor and Walker (1954) expanded exposure monitoring to include the estimation of potential dermal exposure using pads attached to workers clothing. Durham and Wolfe (1962), in their classic review of worker exposure methodologies, also provided some experimental validation for the best available methods. 

Disparate effects on T-cell proliferative responses have been reported following exposure to JP-8. Significant suppression of T-cell proliferation is reported following either inhalation or dermal exposure to JP-8 [ 18,20,36], while the response is unaffected following either the oral or dermal exposure routes in other studies [66,71,72], These differences may be explained by variations in exposure routes and in assay methodology, as agents used to evaluate T-lymphocyte activation and proliferation were diverse and included Con A plus IL-2 [18,20], anti-CD3 [36], or Con A only [66,71,72],... 

MRLs are based on noncancer health effects only and do not reflect a consideration of carcinogenic effects. MRLs can be derived for acute, intermediate, and chronic duration exposures for inhalation and oral routes. Appropriate methodology does not exist to develop MRLs for dermal exposure. 

Fenske, R.A., J.T. LeffingweU and R.C. Spear (1985). Evaluation of Fluorescent Tracer Methodology for Dermal Exposure Assessment, in Dermal Exposure Related To Pesticide Use, R.C. Honeycutt, G. Zweig and N.N. Ragsdale (Eds), ACS Symposium Series 273, American Chemical Society, Washington, DC, USA, pp. 377-393. 

Hsu, I.P., C.E. Camann, E. Schattenberg m, B. Wheeler, K. Villalobos, S. Quarderer and R.G. Lewis (1990). New dermal exposure sampling technique, in Total Exposure Assessment Methodology A New Horizon, Pubhcation VIP-16, Air and Waste Management Association, Pittsburgh, PA, USA, pp. 489-497. 

Driver, J.H., G.K. Whitmyre, J.J. Konz, T.A. Roy, J.J. Yang and A.J. Krueger (1989). Dermal exposure assessment for toxicants in soU soil adherence to skin and dermal bioavailability, in Total Exposure Assessment Methodology A New Horizon, Proceedings of the EPA/A WMA Speciality Conference, November 1989, Las Vegas, NV, USA, pp. 597-618. 

Different methods of human exposure assessment vary with respect to the input data or information required and the degree of uncertainty associated with resulting estimates. Eor example, the film-thickness approach to dermal exposure assessment is a screening-level methodology that assumes a uniform layer of material (e.g., a liquid consumer product) is on the skin, and that a portion of the material in this layer is absorbed, per the dermal absorption characteristics of the chemical. In contrast, dermal exposure assessment and percutaneous absorption methods can include metrics that account for time-dependent exposure and absorption processes. Eor example, in the case of secondary dermal contact with chemicals on surfaces (e.g., transfer of pesticide residues from... 

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