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David S White

Publications and source records attributed to David S White.

5 recordsLinked to original sources
PubMed2005

Resolving disputes about toxicological risks during military conflict : the US Gulf War experience.

In the last 15 years, the US and UK have fought two major wars in the Persian Gulf region. Controversy has arisen over the nature and causes of health problems among military veterans of these two wars. Toxic exposures have been hypothesised to cause the majority of the long-term health problems experienced by veterans of the 1991 Gulf War. The assessment of these toxic exposures and the resolution of controversy about their health effects provide a unique case study for understanding how toxicological disputes are settled in the US. Neither clinical examination of ill war veterans nor scientific research studies have been sufficient to answer contentious questions about toxic exposures. Numerous expert review panels have also been unable to resolve these controversies except for the US National Academy of Sciences Institute of Medicine (IOM). The IOM has conducted exhaustive and independent investigations based on peer-reviewed scientific literature related to potential health risks during the two Gulf Wars. In four recent studies, IOM committees identified a wide range of previously documented illnesses associated with common occupational and environmental exposures after considering thousands of relevant publications; however, they did not identify a new medical syndrome or a specific toxic exposure that caused widespread health problems among Gulf War veterans. These IOM studies have, therefore, added little to our basic knowledge of environmental hazards because most of the health effects were well known. Nevertheless, this expert review process, which is on-going, has been generally acceptable to a wide range of competing interests because the findings of the IOM have been perceived as scientifically credible and independent, and because none of the postulated toxicological risks have been completely ruled-out as possible causes of ill health among veterans.

Expert Testimony↗
PubMedDate not supplied

Physicians answer more clinical questions and change clinical decisions more often with synthesized evidence: a randomized trial in primary care.

PURPOSE: Clinicians need evidence in a format that rapidly answers their questions. DynaMed is a database of synthesized evidence. We investigated whether primary care clinicians would answer more clinical questions, change clinical decision making, and alter search time using DynaMed in addition to their usual information sources. METHODS: Fifty-two primary care clinicians naïve to DynaMed searched for answers to 698 of their own clinical questions using the Internet. On a per-question basis, participants were randomized to have access to DynaMed (A) or not (N) in addition to their usual information sources. Outcomes included proportions of questions answered, proportions of questions with answers that changed clinical decision making, and median search times. The statistical approach of per-participant analyses of clinicians who asked questions in both A and N states was decided before data collection. RESULTS: Among 46 clinicians in per-participant analyses, 23 (50%) answered a greater proportion of questions during A than N, and 13 (28.3%) answered more questions during N than A (P = .05). Finding answers that changed clinical decision making occurred more often during A (25 clinicians, 54.3%) than during N (13 clinicians, 28.3%) (P = .01). Search times did not differ significantly. Overall, participants found answers for 263 (75.8%) of 347 A questions and 250 (71.2%) of 351 N questions. Answers changed clinical decision making for 224 (64.6%) of the A questions and 209 (59.5%) of the N questions. CONCLUSIONS: Using DynaMed, primary care clinicians answered more questions and changed clinical decisions more often, without increasing overall search time. Synthesizing results of systematic evidence surveillance is a feasible method for meeting clinical information needs in primary care.

Databases, Factual↗
PubMedDate not supplied

Particulates, not plants, dominate nitrogen processing in a septage-treating aerated pond system.

In pond and wetland systems for wastewater treatment, plants are often thought to enhance the removal of ammonium and nitrogen through the activities of root-associated bacteria. In this study, we examined the role of plant roots in an aerated pond system with floating plants designed to treat high-strength septage wastewater. We performed both laboratory and full-scale experiments to test the effect of different plant root to septage ratios on nitrification and denitrification, and measured the abundances of nitrifying bacteria associated with roots and septage particulates. Root-associated nitrifying bacteria did not play a significant role in ammonium and total nitrogen removal. Investigations of nitrifier populations showed that only 10% were associated with water hyacinth [Eichhornia crassipes (Mart.) Solms] roots (at standard facility plant densities equivalent to 2.2 wet g roots L(-1) septage); instead, nitrifiers were found almost entirely (90%) associated with suspended septage particulates. The role of root-associated nitrifiers in nitrification was examined in laboratory batch experiments where high plant root concentrations (7.4 wet g L(-1), representing a 38% net increase in total nitrifier populations over plant-free controls) yielded a corresponding increase (55%) in the non-substrate-limited nitrification rate (V(max)). However, within the full-scale septage-treating pond system, nitrification and denitrification rates remained unchanged when plant root concentrations were increased to 7.1 g roots L(-1) (achieved by increasing the surface area available for plants while maintaining the same tank volume). Under normal facility operating conditions, nitrification was limited by ammonium concentration, not nitrifier availability. Maximizing plant root concentrations was found to be an inefficient mechanism for increasing nitrification in organic particulate-rich wastewaters such as septage.

Adsorption↗