Validation of the bag-mediated filtration system for environmental surveillance of poliovirus in Nairobi, Kenya.

AIMS: This study compared the bag-mediated filtration system (BMFS) and standard WHO two-phase separation methods for poliovirus (PV) environmental surveillance, examined factors impacting PV detection and monitored Sabin-like (SL) PV type 2 presence with withdrawal of oral polio vaccine type 2 (OPV2) in April 2016. METHODS AND RESULTS: Environmental samples were collected in Nairobi, Kenya (Sept 2015-Feb 2017), concentrated via BMFS and two-phase separation methods, then assayed using the WHO PV isolation algorithm and intratypic differentiation diagnostic screening kit. SL1, SL2 and SL3 were detected at higher rates in BMFS than two-phase samples (P < 0·05). In BMFS samples, SL PV detection did not significantly differ with volume filtered, filtration time or filter shipment time (P > 0·05), while SL3 was detected less frequently with higher shipment temperatures (P = 0·027). SL2 was detected more frequently before OPV2 withdrawal in BMFS and two-phase samples (P < 1 × 10-5 ). CONCLUSIONS: Poliovirus was detected at higher rates with the BMFS, a method that includes a secondary concentration step, than using the standard WHO two-phase method. SL2 disappearance from the environment was commensurate with OPV2 withdrawal. SIGNIFICANCE AND IMPACT OF THE STUDY: The BMFS offers comparable or improved PV detection under the conditions in this study, relative to the two-phase method.

Adult responses to a survey of soil contact-related behaviors.

Protocols used to assess human exposure to chemicals in soils at contaminated sites often include a dermal pathway. Use of default parameters to assess dermal exposure to soil can easily lead to risk projections that appear to warrant remedial action. However, because those default parameters are typically highly uncertain, risk estimates based upon them inspire little confidence. To better characterize assumptions regarding dermal exposures, a telephone survey instrument was developed to elicit information on behaviors relevant to assessment of dermal contact with soil and dust. Participation in four activities--gardening, other yard work, outdoor team sports, and home construction or repair involving digging--was investigated. Questions were also asked regarding clothing choices and post-activity bathing practices. The survey was administered to two populations of approximately 450 adult respondents each using random digit dialing. The first was a national (U.S.) sample. The second sample was drawn from counties surrounding the Hanford Nuclear Reservation. Seventy-nine percent of the regional respondents and 89% of the national respondents reported participating in at least one of the four targeted activities. Responses of doers regarding clothing choices suggest that median fractions of skin exposed during warm-weather activities typically exceed the 25% often assumed. The Hanford sample differed from the national sample in the fraction residing in single-family homes, the fraction describing their residential surroundings as rural, and in ethnic makeup. The Hanford population displayed greater rates of participation than the national sample in three activities that have an obvious link to residence in a single-family dwelling: home repair involving digging, gardening, and other yard work, but differences were not explained entirely by residence type. The regional population also reported greater frequency of participation in multiple activities. In contrast, clothing choices among doers could not be distinguished between the two groups.

Adult proxy responses to a survey of children's dermal soil contact activities.

Contaminated site cleanup decisions may require estimation of dermal exposures to soil. Telephone surveys represent one means of obtaining relevant activity pattern data. The initial Soil Contact Survey (SCS-I), which primarily gathered information on the activities of adults, was conducted in 1996. Data describing adult behaviors have been previously reported. Results from a second Soil Contact Survey (SCS-II), performed in 1998-1999 and focused on children's activity patterns, are reported here. Telephone surveys were used to query a randomly selected sample of U.S. households. A randomly chosen child, under the age of 18 years, was targeted in each responding household having children. Play activities as well as bathing patterns were investigated to quantify total exposure time, defined as activity time plus delay until washing. Of 680 total survey respondents, 500 (73.5%) reported that their child played outdoors on bare dirt or mixed grass and dirt surfaces. Among these "players," the median reported play frequency was 7 days/week in warm weather and 3 days/week in cold weather. Median play duration was 3 h/day in warm weather and 1 h/day in cold weather. Hand washes were reported to occur a median of 4 times per day in both warm and cold weather months. Bath or shower median frequency was seven times per week in both warm and cold weather. Finally, based on clothing choice data gathered in SCS-I, a median of about 37% of total skin surface is estimated to be exposed during young children's warm weather outdoor play.

Uncertainty in estimated half-lives of PCBS in humans: impact on exposure assessment.

Estimates of the half-lives of PCBs in humans derived from successive body burden measurements are reviewed and found to vary widely whether based on congener-specific or aggregate data. Variability due to differences in physiological processes among individuals and in congener properties is to be expected, but does not appear to be a complete explanation. Very short half-lives (i.e. < 1 year) are unlikely for those congeners most frequently found in human blood because the exposures required to sustain observed body burdens are too large to be easily explained. Very long half-lives ( > 10 years) may be artifacts of confounding by ongoing exposures (a common effect at low body burdens) and are also suspect. The loss of significant quantities of PCBs from the blood of occupationally exposed persons with half-lives of 2-6 years is comparatively well documented (i.e. has been observed in studies with relatively large numbers of subjects and high initial body burdens). Therefore, very long half-lives must be limited to subsets of congeners or of populations if they occur at all. The impact of the use of fixed estimates of half-lives drawn from the tails of the observed range on the evaluation of regulatory standards is shown to be substantial.

Field measurement of dermal soil loadings in occupational and recreational activities.

Risks associated with dermal exposure to contaminated soil are not well-characterized, but nevertheless must be estimated to define endpoints for remedial strategies. Among the parameters contributing to the uncertainty of these estimates is soil adherence to skin. Pre- and postactivity soil loadings have been obtained from hands, forearms, lower legs, faces, and/or feet of volunteers engaged in various occupational and recreational activities. These data are distinguished from other sources of estimates of soil adherence by the manner of their collection. Soil loads were obtained directly from multiple body parts before and after uncontrived exposure scenarios. Data presented for the first time here supplement prior results and roughly double the available data base. This expanded data base provides a useful perspective on types of behavior likely to lead to soil contact falling within general classes of activity (e.g., background, low, moderate, or high contact). Prior conclusions supported by the additional data include the following: (1) post-activity loadings are typically higher than preactivity levels, demonstrating that exposure is episodic; (2) hand loadings are dependent upon class of activity; (3) hand loadings generally provide conservative estimates of loadings on nonhand body parts within activity classes; and (4) hand loadings do not provide conservative estimates of nonhand loadings across activity classes. Finally quantitative estimates of relative loads on unclothed nonhand body parts are presented.