Abstract:Introduction: Clostridium difficile is the leading cause of health care-associated gastric illness. Environmental contamination with C difficile spores is a risk factor for contact transmission, and toilet flushing causes such contamination. This work explores toilet contamination persistence and environmental contamination produced over a series of flushes after contamination. Methods: A flushometer toilet was seeded with C difficile spores in a sealed chamber. The toilet was flushed 24 times, with postflush bowl water samples and settle plates periodically collected for culturing and counting. Air samples were collected after each of 12 flushes using rotating plate impactors. Results: Spores were present in bowl water even after 24 flushes. Large droplet spore deposition accumulated over the 24-flush period. Droplet nuclei spore bioaerosol was produced over at least 12 flushes. Conclusions: Toilets contaminated with C difficile spores are a persistent source of environmental contamination over an extended number of flushes. (C) 2018 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Abstract:Deoxynivalenol (DON) is a group B trichothecene and a common contaminant of food crops worldwide. DON is known to cause a spectrum of diseases in animals and humans such as vomiting and gastroenteritis and has been shown to cross the human placental barrier: therefore, dietary exposure during pregnancy could lead to exposure of the fetus. Since the mechanism of DON toxicity action has not been thoroughly elucidated, further evaluation of the underlying mechanisms of DON's embryotoxicity is needed. This is especially important for developing exposure guidance recommendations, especially those targeted towards pregnant women. In the present study, murine embryonic stem cell test (mEST) and human embryonic stem cell test (hEST) models were developed according to protocols of the European Centre for the Validation of Alternative Methods (ECVAM). Different concentrations of DON were administered to mouse embryonic stem cells D3 (mESC-D3), mouse Balbic-3T3 (3T3) embryo fibroblast cells, and human embryonic stem cells H9 (hESC-H9) for 10 days to detect the 50%% inhibitory proliferation concentration (1050) of mESC-D3 cells, 313 cells, and hESC-H9 cells with DON. Differentiation of ESCs was initiated by embryoid body (EBs) formation. EBs were exposed to different concentrations of DON for 10 days. The expression of cardiomyocyte differentiation gene alpha-myosin heavy chain (alpha-MHC) was detected by real-time PCR and the 50%% inhibition of cardiomyocyte differentiation (ID50) was determined. Based on the values of IC50 and ID50, functions I, II, and III were calculated by three linear discriminant functions in the EST model and the embryotoxicity of DON was described by comparing the three functions. Results of the three endpoints of DON in murine EST were 0.141 mu g/ml (IC50 3T3), 0.085 mu g/ml (IC50 D3), and 0.110 mu g/ml (ID50 D3). The function I (-34.43), function II (-18.62), and function III (1.98) were calculated for DON by them EST model. The three endpoints of DON in hEST were 0.13 mu g/ml (IC50 313), 0.11 mu g/ml (IC50 H9), and 0.078 mu g/ml (ID50). Function I (-25.97), function II (-13.18), and function III (-0.12) were calculated based on IC50 and ID50. Since function III > function II > function I, according to the EST criteria, DON was determined to have strong embryo toxicity both by mEST and hEST. Moreover, the hEST model, which excluded species differences, is suggested to be a more accurate and reliable method for the evaluation of chemical embryotoxicity. (C) 2017 Elsevier Ltd. All rights reserved.

Abstract:Associations have been shown between poor classroom indoor air quality (IAQ) and schoolchildren's risk of asthma, increased absenteeism, and impaired performance on standardized tests. Mechanically ventilated classrooms often lack an adequate fresh air supply. There is also concern that outdoor pollutants, particularly vehicle exhaust products, may penetrate classrooms. The purpose of this work was to characterize IAQ in elementary school classrooms and estimate average effective fresh air ventilation rates under cold, mild, and warm season conditions. IAQ measures were made in third-grade classrooms of 12 elementary schools. Particulate matter, CO2, CO, NO2, total VOCs, and formaldehyde concentrations, as well as relative humidity and temperature, were measured for 24-h periods in each season. Effective fresh air ventilation rates were estimated using a transient mass balance modeling approach. The schools measured had generally adequate temperature and humidity control, extremely low non-occupant related pollutants, and little to no incursion of outdoor vehicle-related pollutants. However, there was a lack of adequate fresh air ventilation in many cases. Ventilation adequacy varied within the schools across seasons but with no consistent pattern, perhaps reflecting variations in class size as well as seasonal demands on the HVAC systems and/or HVAC seasonal operating mode. Transient mass balance method effective fresh air ventilation estimates near or above ASHRAE-recommended fresh air ventilation rates for people-related pollutants corresponded well with good CO2 control in the classrooms.