Sampling household surfaces for pesticide residues: comparison between a press sampler and solvent-moistened wipes.

A modified Press Sampler was evaluated to determine the efficiency of pesticide transfer from household surfaces to collection disks as compared to wiping with a solvent-moistened gauze pad. Organophosphate (OP), pyrazole, and pyrethroid pesticides were applied to three hard flooring materials and carpet at two loading rates. Surfaces were dried and press sampled using C(18), 100% cotton or polyurethane foam (PUF) for either 2 or 10 min or wiped with isopropanol-moistened gauze pads. Transfer efficiencies (TE, %) were calculated as a fraction of surface loadings captured simultaneously on foil deposition coupons. The highest mean TEs (17-55%) for the Press Sampler were observed for OPs from hard surfaces to C(18), considering both contact times. Cotton and PUF transferred 6-27% and 5-30% of OPs, respectively. Corresponding mean TEs for pyrazole and pyrethroid pesticides were only 3% (C(18)), 2-3% (cotton) and 1-2% (PUF). Wipes of hard surfaces removed 84-97% of all pesticides while wipes of carpet removed 31-39%, much higher than transferred to any Press Sampler materials. The mean TEs suggested that the extent of pesticide residue transfer was affected by surface type, pesticide class, and sampling procedure. Wiping was more efficient than press sampling for pesticide surface residue measurements, particularly for loading rates typical of residences.

Use of pharmacokinetic modeling to design studies for pathway-specific exposure model evaluation.

Validating an exposure pathway model is difficult because the biomarker, which is often used to evaluate the model prediction, is an integrated measure for exposures from all the exposure routes and pathways. The purpose of this article is to demonstrate a method to use pharmacokinetic (PK) modeling and computer simulation to guide the design of field studies to validate pathway models. The children's dietary intake model is discussed in detail as an example. Three important aspects are identified for a successful design to evaluate the children's dietary intake model: a) longitudinally designed study with significant changes in the exposure for the route/pathway of interest, b) short biologic half-life of the selected chemical, and c) surface loading of the selected chemical at sufficient levels. Using PK modeling to guide a study design allowed a path-specific exposure model to be evaluated using urinary metabolite biomarkers.

Transfer efficiencies of pesticides from household flooring surfaces to foods.

The transfer of pesticides from household surfaces to foods was measured to determine the degree of excess dietary exposure that occurs when children's foods contact contaminated surfaces prior to being eaten. Three household flooring surfaces (ceramic tile, hardwood, and carpet) were contaminated with an aqueous emulsion of commercially available pesticides (diazinon, heptachlor, malathion, chlorpyrifos, isofenphos, and cis- and trans-permethrin) frequently found in residential environments. A surface wipe method, as typically used in residential exposure studies, was used to measure the pesticides available on the surfaces as a basis for calculating transfer efficiency to the foods. Three foods (apple, bologna, and cheese) routinely handled by children before eating were placed on the contaminated surfaces and transfers of pesticides were measured after 10 min contact. Other contact durations (1 and 60 min) and applying additional contact force (1500 g) to the foods were evaluated for their impact on transferred pesticides. More pesticides transferred to the foods from the hard surfaces, that is, ceramic tile and hardwood flooring, than from carpet. Mean transfer efficiencies for all pesticides to the three foods ranged from 24% to 40% from ceramic tile and 15% to 29% from hardwood, as compared to mostly non-detectable transfers from carpet. Contact duration and applied force notably increased pesticide transfer. The mean transfer efficiency for the seven pesticides increased from around 1% at 1 min to 55- 83% when contact duration was increased to 60 min for the three foods contacting hardwood flooring. Mean transfer efficiency for 10-min contact increased from 15% to 70% when a 1500 g force was applied to bologna placed on hardwood flooring. Contamination of food occurs from contact with pesticide-laden surfaces, thus increasing the potential for excess dietary exposure of children.

Using Thermocouples to Measure Temperatures during Retort or Autoclave Validation 1.

Thermocouples (TCs) are used almost exclusively in designing and validating the heat processes needed for sterilization of product in retorts or autoclaves. In this paper we discuss the vexing errors associated with using TCs in a hot, wet environment. Most problems seem to be associated with the action of steam and water on the TC lead wires and/or caused by temperature gradients on lead wire connectors. These errors are particularly troublesome since they are in the range of 1 to 2°C and are random in nature. The use of a pair of continuous wires that is protected or sealed from the wet retort environment, from the TC junction to the measuring instrument, is the most effective way to reduce or eliminate these problems. The hot, wet environment apparently causes electrochemical effects that produce measurable electromotive forces (EMFs) whenever bare wires come in contact with steam or water. However, the effect is greater when the wires pass through water than through steam. For containers that are nonconductors of electricity, such as plastics, grounding of the TC junction has proved necessary, particularly when processing in flowing water. We conclude that TCs can measure temperature very accurately if properly used. We emphasize that the TC system must be adequately calibrated, and that ambient temperature calibration will not compensate for high-temperature water effects and the errors caused by temperature gradients across connectors.

Critical Factors for Thermal Processing of Institutional Pouches.

Institutional-sized pouches filled with whole kernel com in brine and condensed cream of celery soup were heated in a still retort. The sterilization values (Fo) and heat penetration parameters (j, fh, f2) were determined from temperature/time data as a function of the residual air in the horizontal pouches, pouch thickness, product fill, and circulation of the heating water. The Fo value for the soup was reduced from 11.5 to 2.5 min as the residual air in the pouch was increased to 250 ml The fh value nearly doubled as a result of the insulating effect of the air layer at the upper surface of the pouch, Eliminating the circulation of the heating water between the pouch layers increased the critical dimension for heat transfer and reduced the Fo for the soup to 0.6 min, an unacceptable value.