A social-ecological analysis of drinking water risks in coastal Bangladesh.

Groundwater resources in deltaic regions are vulnerable to contamination by saline seawater, posing significant crisis for drinking water. Current policy and practice of building water supply infrastructure, without adequate hydrogeological analysis and institutional coordination are failing to provide basic drinking water services for millions of poor people in such difficult hydrogeological contexts. We apply a social-ecological systems approach to examine interdisciplinary data from hydrogeological mapping, a water infrastructure audit, 2103 household surveys, focus group discussions and interviews to evaluate the risks to drinking water security in one of 139 polders in coastal Bangladesh. We find that increasing access through public tubewells is common but insufficient to reduce drinking water risks. In response, there has been a four-fold growth in private investments in shallow tubewells with new technologies and entrepreneurial models to mitigate groundwater salinity. Despite these interventions, poor households in water-stressed environments face significant trade-offs in drinking water quality, accessibility and affordability. We argue that institutional coordination and hydrogeological monitoring at a systems level is necessary to mitigate socio-ecological risks for more equitable and efficient outcomes.

Risks and responses to universal drinking water security.

Risks to universal drinking water security are accelerating due to rapid demographic, climate and economic change. Policy responses are slow, uneven and largely inadequate to address the nature and scale of the global challenges. The challenges relate both to maintaining water security in increasingly fragile supply systems and to accelerating reliable access to the hundreds of millions who remain water-insecure. A conceptual framework illustrates the relationship between institutional, operational and financial risks and drinking water security outcomes. We apply the framework to nine case studies from rural and urban contexts in South Asia and sub-Saharan Africa. Case studies are purposively selected based on established and emerging examples of political, technological or institutional reforms that address water security risks. We find broad evidence that improved information flows reduce institutional costs and promote stronger and more transparent operational performance to increase financial sustainability. However, political barriers need to be overcome in all cases through internal or external interventions that require often decadal time frames and catalytic investments. No single model exists, though there is sufficient evidence to demonstrate that risks to drinking water security can be reduced even in the most difficult and challenging contexts.

Scattered ultraviolet emissions during refractive surgery using a high-frequency, wavefront-optimized excimer laser platform.

PURPOSE: To evaluate occupational ultraviolet (UV) exposure during photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with the Allegretto Wave Eye-Q 400 Hz excimer laser. SETTING: Walter Reed Center for Refractive Surgery, Washington, DC, USA. METHODS: Intraoperative UV measurements were performed during PRK with epithelial removal using an Amoils brush, PRK with epithelial removal using 20% ethanol, or femtosecond LASIK. A LaserStar power/energy meter with a silicone detector (model PD-10) was used for the measurements. The maximum pulse energy 25.4 cm from the corneal surface was recorded for each surgical procedure. Measurements were evaluated using a worst-case scenario for exposure of operating room personnel, and the results were compared with the occupational exposure limit set by the International Commission on Non-Ionizing Radiation Protection. RESULTS: Measurements were taken during 15 cases of each procedure. The mean maximum exposure was 129.38 nJ/pulse +/- 79.48 (SD) during brush PRK, 69.72 +/- 68.80 nJ/pulse during ethanol PRK, and 29.17 +/- 13.82 nJ/pulse during LASIK. The mean maximum exposure per eye was 0.085 mJ/cm(2), 0.046 mJ/cm(2), and 0.01 mJ/cm(2), respectively. The worst-case cumulative exposure during a heavy workday of 20 patients (40 eyes) was calculated at 3.92 mJ/cm(2), 1.51 mJ/cm(2), and 0.79 mJ/cm(2) for brush PRK, ethanol PRK, and LASIK, respectively. CONCLUSION: Results indicate that the excimer laser platform used in the study may yield greater UV exposure than previous systems; however, the levels did not exceed occupational exposure limits. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.