Determination of cyclic volatile methylsiloxanes in personal care products by gas chromatography.

OBJECTIVE: Organosiloxanes are prevalent in personal care products (PCPs) due to the desired properties they impart in the usage and application of such products. However, the European Chemical Agency (ECHA) has recently published restriction proposals on the amount of two cyclic siloxanes, octamethylcyclotetrasiloxane (D4) and decamethylcyclotetrasiloxane (D5), allowed in wash off products such as shampoos and conditioners which are discharged down the drain during consumer use. This legislation will require that reliable analytical methods are available for manufacturers and government agencies to use in documenting compliance with the restrictions. This article proposes a simple analytical method to enable accurate measurement of these compounds down to the circa 0.1 weight per cent level in PCPs. METHODS: Although gas chromatography methods are reported in the literature for quantitation of D4 and D5 in several matrices including PCPs, the potential for generation of false positives due to contamination, co-elution and in situ generation of cyclic volatile methylsiloxanes (cVMS) is always present and needs to be controlled. This report demonstrates the applicability of using a combination of emulsion break, liquid-liquid extraction and silylation sample preparation followed by GC-FID analysis as a suitable means of analysing PCPs for specific cVMS. RESULTS: The reliability and limitations of such methodology were demonstrated through several round-robin studies conducted in the laboratories of a consortium of silicone manufacturers. In addition, this report presents examples of false positives encountered during development of the method and presents a comparative analysis between this method and a published QuEChERS sample preparation procedure to illustrate the potential for generation of false positives when an inappropriate approach is applied to determination of cVMS in personal care products. CONCLUSION: This report demonstrates that an approach to determine cVMS levels in personal care products is to perform an emulsion break on the sample, isolate the non-polar phase from the emulsion break and treat with a silylation reagent to abate potential in situ formation of cyclics during the course of GC-FID analysis. Round-robin studies conducted in laboratories representing multiple siloxane manufacturers demonstrated the reliability of the GC-FID method when measuring cVMS in PCPs down to circa 0.1%.

Cryptosporidiosis from a community swimming pool: outbreak investigation and follow-up study.

Tri-County Health Department investigated an outbreak of cryptosporidiosis linked to a community swimming pool. A cohort study was conducted in 37 persons who were invited to the pool party; 12 (57%) of 21 attendees had primary cryptosporidiosis infection. Risk factors for illness included swimming, getting water in mouth, and swallowing water. The pool met chlorination guidelines and used UV light irradiation, a supplemental disinfection technology that inactivates Cryptosporidium. A follow-up survey of the cohort was completed 7-8 weeks after the pool party; four (25%) of 16 non-attendees had secondary cryptosporidiosis infection. The median duration of illness, including patients with recurring symptoms, was 26 days. Clinical response rate to nitazoxanide, a therapeutic agent, was 67%. This study is unique because it describes a cryptosporidiosis outbreak from a well-maintained community swimming pool using supplemental disinfection. It also reports information on disease burden and treatment response.

Personal, neighbourhood and urban factors associated with obesity in the United States.

INTRODUCTION: Growing evidence suggests the built environment impacts obesity within urban areas; however, little research has investigated these relationships across levels of urbanisation in diverse and representative populations. This study aimed to determine whether personal and neighbourhood barriers differ by the level of urbanisation and the relative importance of personal barriers, neighbourhood barriers and land-use development patterns measured by a county-level sprawl index. METHODS: Population-based, cross-sectional telephone survey data were collected on 1818 United States adults of diverse ethnicity and income level. Primary analyses were stratified by the level of urbanisation at the county level (large metropolitan, small metropolitan, non-metro, rural). Associations between obesity and neighbourhood and personal barriers were estimated with logistic regression, controlling for demographic variables. Within metropolitan areas, the association between body mass index (BMI) and county-level sprawl was estimated using hierarchical linear modelling, controlling for individual-level neighbourhood and personal barriers and demographic variables and then assessing cross-level interaction. RESULTS: The prevalence of neighbourhood, but not personal, barriers differed widely across levels of urbanisation. Specific neighbourhood (eg traffic, unattended dogs) and personal (eg time, injury) barriers differentially correlated with obesity across strata. The impact of sprawl on BMI (B = -0.005) was consistent with previous findings; standardised coefficients indicate that personal (beta = 0.10) and neighbourhood (beta = 0.05) barriers had a stronger association than sprawl (beta = -0.02). Furthermore, the effect of sprawl on BMI increased by -0.006 with each additional personal barrier. CONCLUSIONS: Future intervention planning and policy development should consider that personal barriers and built environment characteristics may interact with each other and influence obesity differently across urbanisation levels.

Perceived and observed neighborhood indicators of obesity among urban adults.

OBJECTIVE: The global obesity epidemic has been partially attributed to modern environments that encourage inactivity and overeating, yet few studies have examined specific features of the physical neighborhood environment that influence obesity. Using two different measurement methods, this study sought to identify and compare perceived and observed neighborhood indicators of obesity and a high-risk profile of being obese and inactive. DESIGN: Cross-sectional telephone surveys (perceived) and street-scale environmental audits (observed) were conducted concurrently in two diverse US cities to assess recreational facility access, land use, transportation infrastructure and aesthetics. SUBJECTS: A total of 1032 randomly selected urban residents (20% obese, 32% black, 65% female). ANALYSIS: Bivariate and multivariate logistic regression analyses were conducted to estimate the association (adjusted prevalence odds ratio (aOR)) between the primary outcome (obese vs normal weight) and perceived and observed environmental indicators, controlling for demographic variables. RESULTS: Being obese was significantly associated with perceived indicators of no nearby nonresidential destinations (aOR=2.2), absence of sidewalks (aOR=2.2), unpleasant community (aOR=3.1) and lack of interesting sites (aOR=4.8) and observed indicators of poor sidewalk quality (aOR=2.1), physical disorder (aOR=4.0) and presence of garbage (aOR=3.7). Perceived and observed indicators of land use and aesthetics were the most robust neighborhood correlates of obesity in multivariate analyses. CONCLUSIONS: The findings contribute substantially to the growing evidence base of community-level correlates of obesity and suggest salient environmental and policy intervention strategies that may reduce population-level obesity prevalence. Continued use of both measurement methods is recommended to clarify inconsistent associations across perceived and observed indicators within the same domain.