Virus transfer between fingerpads and fomites.

AIMS: Virus transfer between individuals and fomites is an important route of transmission for both gastrointestinal and respiratory illness. The present study examines how direction of transfer, virus species, time since last handwashing, gender, and titre affect viral transfer between fingerpads and glass. METHODS AND RESULTS: Six hundred fifty-six total transfer events, performed by 20 volunteers using MS2, φX174, and fr indicated 0·23 ± 0·22 (mean and standard deviation) of virus is readily transferred on contact. Virus transfer is significantly influenced by virus species and time since last handwashing. Transfer of fr bacteriophage is significantly higher than both MS2 and φX174. Virus transfer between surfaces is reduced for recently washed hands. CONCLUSIONS: Viruses are readily transferred between skin and surfaces on contact. The fraction of virus transferred is dependent on multiple factors including virus species, recently washing hands, and direction of transfer likely because of surface physicochemical interactions. SIGNIFICANCE AND IMPACT OF THE STUDY: The study is the first to provide a large data set of virus transfer events describing the central tendency and distribution of fraction virus transferred between fingers and glass. The data set from the study, along with the quantified effect sizes of the factors explored, inform studies examining role of fomites in disease transmission.

Effect of 200 days' sludge retention time on performance of a pilot scale submerged membrane bioreactor for high strength industrial wastewater treatment.

A high strength industrial wastewater was treated using a pilot scale submerged membrane bioreactor (MBR) at a sludge retention time (SRT) of 200 d. The MBR was operated at a high sludge concentration of 20 g/L and a low F/M ratio of 0.11 during 300 d of operation. It was found that the MBR could achieve COD and TOC overall removal efficiencies at more than 99 and 98% TN removal. The turbidity of the permeate was consistently in the range of 0.123 to 0.136 NTU and colour254 absorbance readings varied from 0.0912 to 0.0962 a.u. cm(-1). The sludge concentration was inversely proportional to the hydraulic retention time (HRT), yielded excellent organic removal and extremely low sludge production (0.0016 kgVSS/day).

Surface complexation modeling of carbonate effects on the adsorption of Cr(VI), Pb(II), and U(VI) on goethite.

Dissolved carbonate species are known to affect the sorption behavior of trace species. The macroscopic description of these interactions with a thermodynamic approach has been limited by the lack of data on the binary interaction between carbonate and relevant mineral surfaces. This work follows from two detailed studies of carbonate adsorption on goethite (4, 13). It shows that independent triple-layer surface complexation modeling (TLM) of carbonate adsorption allows successful descriptions of carbonate-trace element ternary sorption on this oxide, using relatively simple and optimal stoichiometries. Carbonate adsorption was considerably enhanced in the presence of Pb(II), despite an invariant total Pb(II) sorption to equilibration with up to 1% C02(g). Both the Pb(II)-carbonate system behavior and the anion-like pH adsorption behavior of U(VI) in the presence of C02 were successfully modeled using binary and ternary metal-bound surface complexes. The significant reduction of Cr(VI) adsorption edges to lower pH values in the presence of C02 was accurately simulated and explained via site competition and surface electrostatic repulsion effects on the predicted inner- and outer-sphere Cr(VI) surface complexes formed. The results of this research are highly relevant to modeling of metal transport field data and of potential soil remediation schemes using carbonate.

Factors influencing total dietary exposures of young children.

A deterministic model was developed to identify the critical input parameters needed to assess dietary intakes of young children. The model was used as a framework for understanding the important factors in data collection and data analysis. Factors incorporated into the model included transfer efficiencies of pesticide from surfaces to food, transfer efficiencies of pesticide from surfaces to hands to food, and more accurate microactivity data related to contact frequency for the three variables of interest--hands, surfaces, and food. Results from range-finding measurements of transfer efficiencies using an aqueous pesticide solution of a mixture of malathion, diazinon, and chlorpyrifos sprayed on the surfaces indicate that a higher pesticide transfer occurred from hard surfaces to food (hardwood, plastic), with low transfer from soft surfaces (carpet, cloth). Six children, all less than 4 years old, were videotaped to obtain realistic contact frequency and times for the interaction of hands, surfaces, and foods during eating meals and snacks while in their homes or day care centers. The time range of eating events varied from about 2 to 55 min, with an average of about 20 min. The average number of contact frequencies between food and hands was 19 times for each eating event, with a range of 10-40. Contacts between the surface and hand were about the same as the food and hands. Contacts between foods and surfaces ranged from 0 to 32, but only five or less of the contacts per eating event were associated with surfaces other than eating utensil. The children's microactivity data collected during the eating events, together with the laboratory results from the transfer studies, were provided as input into a Monte Carlo simulation of the dietary ingestion model. Simulation results indicate that children's handling of the food could contribute 20-80% of the total dietary intake of pesticides. Dietary exposure due to residues in the food before handling accounted for 16% and 47%, respectively, of the total mean intake from simulations for a child's consumption of an apple or banana. These results indicated that transfer efficiencies for foods on various surfaces typically found in homes as well as children's hand contacts with the food and surfaces are important as determinants of dietary exposure.

Quantifying videotaped activity patterns: video translation software and training methodologies.

Questionnaires and diaries, the current methods of human activity data collection, do not accurately capture the detail necessary to quantify exposure incurred through the dermal and non-dietary ingestion routes. Stanford University's Environmental Engineering and Science Program has developed methodologies and software (VideoTraq) for training video translators, determining inter-observer reliability, and translating videotaped micro-activity patterns into computer text files. VideoTraq output files contain duration, in seconds, for each combination of location, activity, and object contacted corresponding to the sequential micro-activities of a videotaped subject's contact boundary (e.g., left hand, right hand, mouth). Such output allows for detailed analyses of micro-activity data, including contact frequency and duration. When coupled with environmental concentrations, these data will allow for more accurate exposure assessments, particularly for the dermal and non-dietary ingestion exposure routes.

Quantified dermal activity data from a four-child pilot field study.

Thirty-three hours of videotape collected in a 1993 pilot study were quantified, via a video translation software application, to obtain left and right hand activity data of four children of farmworkers. Reported here are the children's contact duration and frequency for each object in their environment, duration spent in each location and activity exertion level, and frequency distributions of object contact durations. The pilot study provided valuable information for evaluating and improving videotaping and videotape translation methodologies as a means of gathering activity information that can be used to refine dermal exposure estimates. Although a larger database of children's videotaped activities for different ages and populations is needed before generalizations can be made, the data presented here are the most detailed information to date for children's micro-level dermal activities.

Anion-exchange preparation of a (232)U radiotracer for alpha-particle liquid scintillation counting.

Daughter product ingrowths, which could act as analytical interferences, are removed from (232)U(VI) stock solutions prior to use as an alpha-particle emitting radiotracer in conjunction with detection by liquid scintillation counting. The preparative benchtop separation procedure employs elution with HCl through a BioRad AG1-X8 anion-exchange resin column, and fraction collection. The importance of the separation of the (232)U isotope from daughter products, characterized by high recovery, is illustrated by liquid scintillation energy spectra. Rapid ingrowth in the purified fraction also limits the period of time after purification in which the radiotracer is usable.

A pilot study to collect micro-activity data of two- to four-year-old farm labor children in Salinas Valley, California.

A pesticide exposure assessment pilot study was conducted in Salinas Valley, California during September, 1993. The pilot study had two main purposes: 1) to develop general methodologies for videotaping micro-activities of a population, and 2) to collect an initial database of activity patterns of two- to four-year-old farm labor children. Tools to accurately determine exposure and dose through all three pathways (dermal, ingestion, and inhalation) are needed to effectively assess and manage health risks posed by pesticides and other environmental pollutants. Eight to ten hours of videotape data were collected for each of four Mexican-American farm labor children. In addition, the researchers administered a day-after recall questionnaire to the caregivers of the children to test (for the study sample) the hypothesis that recall questionnaires are inadequate for collecting detailed information regarding dermal and hand-to-mouth exposures. The results of this study provide the first detailed set of videotape data on farm labor children, a population at high risk to pesticide exposures. In addition, this is the first project in the exposure assessment field to use direct observation videotaping for collecting micro-activity data in order to quantify dermal and ingestion exposure. The comparison of caregivers' recall of children's activities to actual videotapes from the pilot study supports the hypothesis that videotaping may greatly improve the accuracy of activity information used to compute dermal and ingestion exposures. However, as it was clear that the researchers' presence in some cases altered the activities of the subjects, further experiments need to be conducted to minimize interference of videotaping on exposure-related activities. This paper explains the selection of the study population, the methods used to implement the pilot study, and the lessons learned. While the discussion focuses on four case studies in the Mexican-American farm labor population, the data collection methods developed and the lessons learned can be applied to other populations.

In Situ X-ray Absorption Study of Surface Complexes: Selenium Oxyanions on agr-FeOOH.

A novel application of x-ray absorption spectroscopy has provided structural information for ions sorbed at oxide-water interfaces. As an example, in situ extended x-ray absorption fine structure (EXAFS) measurements of adsorbed selenate and selenite ions at ah alpha-FeOOH(goethite)-water interface have been performed; these measurements show that selenate forms a weakly bonded, outer-sphere complex and that selenite forms a strongly bonded, inner-sphere complex. The selenite ion is bonded directly to the goethite surface in a bidentate fashion with two iron atoms 3.38 angstroms from the selenium atom. Adsorbed selenate has no iron atom in the second coordination shell of selenium, which indicates retention of its hydration sphere upon sorption. This method provides direct structural information for adsorbed species at solid-liquid interfaces.