Dental Workers,Musculoskeletal CumulativeTrauma,and Carpal Tunnel Syndrome: Who is at Risk? A Pilot Study

A pilot study was conducted at a dental clinic to identify (a) the prevalence of musculoskeletal cumulative trauma disorders (MCTD), (b) associated symptoms (with special attention paid to carpal tunnel syndrome [CTS]), and (c) practitioners at risk. Videotapes, two questionnaires, a medical record review, and interviews were used. Forty-five dental workers participated and were classified into three categories: (a) dentists, (b) dental assistants and special assistants (DA/SA), and (c) dental hygienists and dental assistant-expanded function (DH/DAEF). Categorical data were analyzed using the chi- square statistic and risk ratios. The Fisher exact probability test was used for categorical data with a small cell. One or more symptoms associated with CTS were noted by 75.6% of the dental workers, 11% reported diagnosed CTS, and 53% reported back and shoulder pain. Both psychosocial factors and job demands appear to be associated with MCTD. All three categories of dental workers reported MCTD symptoms, and the DH/DAEF group was found to be at greatest risk for developing upper extremity symptoms, CTS, and back pain.     

Comparisons of PBDE composition and concentration in fish collected from the Detroit River,MI and Des Plaines River,IL

Polybrominated diphenyl ethers (PBDEs) were identified in fish collected from the Detroit River, MI and Des Plaines Rivers, IL. In the Detroit River fish, carp and large mouth bass, the congener patterns were dominated by the 2,2',4,4'-tetrabromo (BDE-47) congener, however, in Des Plaines River carp the dominant isomers were the heptabromo congeners BDE-181 and BDE-183 and lesser amounts of another heptabromo congener, BDE-190, and two hexabromo congeners, BDE-154 and BDE-153. Three possible sources exist for these less-commonly identified PBDE congeners: (a) waste discharge from manufacturing or discarded products near the river, (b) public owned treatment work (POTW) effluents which constitute more than 75% of the flow in the Des Plaines River, (c) or formation of these congeners by debromination of in-place deposits of decabromodiphenyl ether. Average concentration totals (sum of concentrations for seven of the dominant PBDE congeners) were similar on a wet weight bases for the carp (5.39 ng/g wet weight) and large mouth bass (5.25 ng/g) in the Detroit River samples; however, the bass were significantly higher, p = 0.01, when compared on a lipid basis (bass--163 ng/g vs. carp--40.5 ng/g lipid weight). Some of the PBDE congeners were positively correlated with increasing lipid levels in both fish species. Average total PBDE concentrations in the carp from the Des Plaines River (12.48 ng/g wet weight) were significantly higher, p = 0.01, than in carp from the Detroit River. The residues were isolated using standard organochlorine methods for fish and analyzed using gas chromatography/mass spectrometry-negative chemical ionization methods.     

Uptake,binding and clearance of divalent cadmium in Glycera dibranchiata (Annelida: Polychaeta)

The bloodworm Glycera dibranchiata Ehlers, 1968 accumulates cadmium through the general body surface and the intestine. Absorption through the gut accounts for cadmium which rapidly binds to coelomic proteins. Intracoelomic injection of ¹⁰⁹Cd demonstrates that cadmium binds readily to hemoglobin and other proteins. The degree of cadmium binding is pH-dependent. The apparent pK of binding sites in body wall and musculature homogenates is 5.39. Cadmium ions injected into the coelom at 7 g g^-1 tissue increase proline incorporation rates into the positively charged hemoglobin (cathode fraction) by 15-fold in 3 days. A 3-fold increase of proline incorporation was observed in the anode hemoglobin fraction over the same time period. Radioactivity in various protein fractions decreases at different rates after injection of ¹⁰⁹Cd. Comparisons between the function of mammalian metallothionein and the coelomic fluid proteins of G. dibranchiata as a detoxification mechanism are discussed.     

Effects of the California graduated driver licensing program

PROBLEM: On July 1, 1998, in an effort to ameliorate the problem of high teenage driver crash rates, California implemented a graduated driver licensing system (GDLS). METHOD: Data on injury crashes of 16- and 17-year-old drivers from a pre-GDLS year were compared with data from two post-GDLS years. Per-capita crash rate ratios were adjusted for changes in crash rates of 25- to 34-year-old drivers, who were unaffected by the GDLS. Prevented numbers and 95% confidence intervals were estimated. RESULTS: Fatal or severe injury crash rates were significantly lower during each of the two post-GDLS years (adjusted rate ratios (RR)=0.72 and 0.83, for 2000 vs. 1997 and 2001 vs. 1997, respectively). Significant rate reductions were observed for all crash types, particularly for struck object (RR=0.71 and 0.80, for 2000 vs. 1997 and 2001 vs. 1997, respectively) and non-collision (RR=0.63 and 0.72, for 2000 vs. 1997 and 2001 vs. 1997, respectively). Minor injury crash rates were also lower during post-GDLS years (RR=0.87 and 0.90, for 2000 vs. 1997 and 2001 vs. 1997, respectively). Percent reductions were notably larger during the hours of the late night driving restriction (midnight-5 a.m.) (RR=0.79 and 0.87, for 2000 vs. 1997 and 2001 vs. 1997, respectively). SUMMARY: The implementation of the California GDLS was followed by large reductions in the rate of injury-producing motor-vehicle crashes. IMPACT ON INDUSTRY: This evaluation supports previous evidence that GDLS is an effective countermeasure to adolescent motor-vehicle crashes and their associated injuries. States with a traditional licensing system may prevent adolescent driver crashes by adopting a GDLS. Future studies should examine factors that influence teenager compliance with GDLS provisions and identify approaches to improving compliance.     

Influence of simulated tidal cycles on aromatic hydrocarbon uptake and elimination by the shore crab Hemigrapsus nudus

Specimens of the intertidal crab Hemigrapsus nudus (Dana, 1851) were collected near Sitka, Alaska, in 1983, and were used in laboratory experiments to determine the influence of periodic exposure to air on the toxicity, uptake, and elimination of two aromatic hydrocarbons, toluene and naphthalene. Three tidal cycles were simulated; i.e., crabs spent 0, 33, or 66% of the time in air and the remainder of the time in toxicant or seawater solutions. Naphthalene was 10 to 20 times more toxic than toluene: naphthalene caused locomotory impairment or killed the crabs more rapidly and at concentrations lower than those of toluene. In tissues, naphthalene was accumulated faster and to higher concentrations than was toluene. Exposure to air 66% of the time reduced mortality as well as the rate at which toluene and naphthalene were accumulated and lost. Crabs exposed to air had significantly higher respiration rates than those submerged in seawater; thus, reduced rates of accumulation and loss of hydrocarbons were not caused by general metabolic quiescence. Exposure to air reduced the time the crabs were in contact with water-borne hydrocarbons and, therefore, reduced toxicity of the hydrocarbons. Once crabs had accumulated the toxicants, however, elimination was hindered by exposure to air, even for the somewhat volatile compound toluene.     

Host-plant green-leaf volatiles synergize the synthetic sex pheromones of the corn earworm and codling moth (Lepidoptera)

Summary The capture of adult male moths in female sex pheromone traps of two key agricultural pests, the corn earworm (Helicoverpa zea) and the codling moth (Cydia pomonella), is enhanced or synergized by a certain group of host-plant volatiles, the green-leaf volatiles (GLVs). Since female adults of both species call and release their sex pheromones while perched upon the leaves of their host-plants, the volatile constituents from the leaves of a number of host-plants were compared. Sex pheromone traps containing one of the prominent leaf volatiles of certainH. zea hosts, (Z)-3-hexenyl acetate, not only significantly increased the capture ofH. zea males but were preferred over traps baited only with sex pheromone. Similarly, traps baited with synthetic sex pheromome ofC. pomonella plus a blend of GLVs captured significantly more males than traps baited only with sex pheromone. Since male moths are not captured in traps baited only with these GLVs, it appears that these GLVs act as pheromone synergists which increase or enhance the attraction or arrestment of male moths in pheromone traps.     

ESTIMATING BASEFLOW VOLUME AND ITS UNCERTAINTY1

ABSTRACT: By using the exponential baseflow recession equation it is possible to estimate from a single discharge measurement the total volume of stream discharge during a baseflow period. If the discharge measurement is properly centered in the baseflow period the resulting estimate will be fairly precise, even if the baseflow recession coefficient is not known. Furthermore, based on an assumed probability distribution of the baseflow coefficient it is possible to estimate the uncertainty of the baseflow volume estimate. Estimates of baseflow volume and their uncertainty are potentially useful for estimating water budgets of lakes.     

Environmental contaminants in nonviable eggs of the endangered Mississippi sandhill crane (Grus canadensis pulla)

Our objectives were to determine if concentrations of environmental pollutants and microbial contamination in nonviable eggs of the endangered Mississippi sandhill crane (Grus canadensis pulla) contributed to egg failure. Six eggs collected in 1990 and four in 1991 contained only background levels of organochlorine pesticides and polychlorinated biphenyls (PCBs), and tests for microbial contamination were all negative. Two eggs contained late dead embryos, but neither revealed obvious abnormalities. Three eggs contained potentially harmful concentrations (23, 39, 146 pg/g, wet mass) of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), based on 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ) for combined compounds. Because of the scarcity of material suitable for laboratory examination and the endangered status of the crane, we recommend that nonviable eggs continue to be monitored for toxic pollutants.     

Management Implications of Snowpack Sensitivity to Temperature and Atmospheric Moisture Changes in Yosemite National Park,CA

In order to investigate snowpack sensitivity to temperature increases and end‐member atmospheric moisture conditions, we applied a well‐constrained energy‐ and mass‐balance snow model across the full elevation range of seasonal snowpack using forcing data from recent wet and dry years. Humidity scenarios examined were constant relative humidity (high) and constant vapor pressure between storms (low). With minimum calibration, model results captured the observed magnitude and timing of snowmelt. April 1 snow water equivalent (SWE) losses of 38%, 73%, and 90% with temperature increases of 2, 4, and 6°C in a dry year centered on areas of greatest SWE accumulation. Each 2°C increment of warming also resulted in seasonal snowline moving upslope by 300 m. The zone of maximum melt was compressed upward 100–500 m with 6°C warming, with the range reflecting differences in basin hypsometry. Melt contribution by elevations below 2,000 m disappeared with 4°C warming. The constant‐relative‐humidity scenario resulted in 0–100 mm less snowpack in late spring vs. the constant‐vapor‐pressure scenario in a wet year, a difference driven by increased thermal radiation (+1.2 W/m²) and turbulent energy fluxes (+1.2 W/m²) to the snowpack for the constant‐relative‐humidity case. Loss of snowpack storage and potential increases in forest evapotranspiration due to warming will result in a substantial shift in forest water balance and present major challenges to land management in this mountainous region.     

A new approach to propellant formulation: minimizing life-cycle costs through science-based design

The traditional approach to developing propellants for specific gun applications relies heavily on trial and error. Candidate formulations must be made in small quantities and subjected to burning-rate measurements and small-scale vulnerability assessments. If the properties of these candidates fail to meet expectations, the process must be repeated. This approach, while historically unavoidable, is obviously inefficient in time and expense, but it also can generate considerable waste streams associated with unsuccessful formulations. With added considerations of life-cycle costs including environmental impact at all stages of development, use, and disposal, this traditional approach becomes increasingly unworkable. In this report a new approach is proposed which makes maximal use of scientific understanding embodied in models during the early phases of the propellant-development cycle. Through simple simulations, it is shown that this strategy can have a significant impact on the overall costs of the development process. In analogy to the DOE program to convert the nuclear-weapon stewardship from testing-based to science-based, we term the new approach "science-based design." It is argued that the modeling contribution to the propellant-development process is most efficiently implemented by subjecting candidate formulations to a hierarchy of models of different sophistication and input-data requirements, reserving the most rigorous models (usually the most data-intensive and least robust) for the most promising candidates. This new approach will require concentration and leveraging of resources toward the most critical early-phase development steps, but it may be the only credible strategy to reconcile the need for higher-performance weapons with the reality of declining resources.