1,4-Dioxane drinking water occurrence data from the third unregulated contaminant monitoring rule.

This study examined data collected from U.S. public drinking water supplies in support of the recently-completed third round of the Unregulated Contaminant Monitoring Rule (UCMR3) to better understand the nature and occurrence of 1,4-dioxane and the basis for establishing drinking water standards. The purpose was to evaluate whether the occurrence data for this emerging but federally-unregulated contaminant fit with common conceptual models, including its persistence and the importance of groundwater contamination for potential exposure. 1,4-Dioxane was detected in samples from 21% of 4864 PWSs, and was in exceedance of the health-based reference concentration (0.35µg/L) at 6.9% of these systems. In both measures, it ranked second among the 28 UCMR3 contaminants. Although much of the focus on 1,4-dioxane has been its role as a groundwater contaminant, the detection frequency for 1,4-dioxane in surface water was only marginally lower than in groundwater (by a factor of 1.25; p<0.0001). However, groundwater concentrations were higher than those in surface water (p<0.0001) and contributed to a higher frequency of exceeding the reference concentration (by a factor of 1.8, p<0.0001), indicating that surface water sources tend to be more dilute. Sampling from large systems increased the likelihood that 1,4-dioxane was detected by a factor of 2.18 times relative to small systems (p<0.0001). 1,4-Dioxane detections in drinking water were highly associated with detections of other chlorinated compounds particularly 1,1-dichlorethane (odds ratio=47; p<0.0001), which is associated with the release of 1,4-dioxane as a chlorinated solvent stabilizer. Based on aggregated nationwide data, 1,4-dioxane showed evidence of a decreasing trend in concentration and detection frequency over time. These data suggest that the loading to drinking water supplies may be decreasing. However, in the interim, some water supply systems may need to consider improving their treatment capabilities in response to further regulatory review of this compound.

Efficacy of static stretching and proprioceptive neuromuscular facilitation stretch on hamstrings length after a single session.

A number of studies have investigated the efficacy of several repetitions of proprioceptive neuromuscular facilitation stretching (PNF) and static stretching (SS). However, there is limited research comparing the effects of a single bout of these stretching maneuvers. The aim of this study was to compare the effectiveness of a single bout of a therapist-applied 30-second SS vs. a single bout of therapist-applied 6-second hamstring (agonist) contract PNF. Forty-five healthy subjects between the ages of 21 and 35 were randomly allocated to 1 of the 2 stretching groups or a control group, in which no stretching was received. The flexibility of the hamstring was determined by a range of passive knee extension, measured using a universal goniometer, with the subject in the supine position and the hip at 90° flexion, before and after intervention. A significant increase in knee extension was found for both intervention groups after a single stretch (SS group = 7.53°, p < 0.01 and PNF group = 11.80°, p < 0.01). Both interventions resulted in a significantly greater increase in knee extension when compared to the control group (p < 0.01). The PNF group demonstrated significantly greater gains in knee extension compared to the SS group (mean difference 4.27°, p < 0.01). It can be concluded that a therapist applied SS or PNF results in a significant increase in hamstring flexibility. A hamstring (agonist) contract PNF is more effective than an SS in a single stretching session. These findings are important to physiotherapists or trainers working in clinical and sporting environments. Where in the past therapists may have spent time conducting multiple repetitions of a PNF and an SS, a single bout of either technique may be considered just as effective. A key component of the study methodology was the exclusion of a warm-up period before stretching. Therefore, the findings of efficacy of a single PNF are of particular relevance in sporting environments and busy clinical settings where time may be limited.