Mutagenic and carcinogenic potency of extracts of diesel and related environmental emissions: Study design, sample generation, collection, and preparation

A major diesel emissions research program has been initiated by the U.S. Environmental Protection Agency to assess the human health risk associated with increased use of diesel automobiles. This program is intended to establish the mutagenic and carcinogenic potency of complex organics associated with diesel particles as well as comparative particle-bound organics from other environmental emissions for which human epidemiological data are available. The mobile source samples selected for this study were collected from a heavy-duty diesel engine, a series of light-duty diesel passenger cars, and a gasoline catalyst automobile. The comparative source samples incorporated into the study were cigarette smoke condensate, coke oven emissions, roofing tar emissions, and benzo(a)pyrene. The samples were tested using three mutagenic assays and four carcinogenic assays as prescribed by a test matrix. This report describes the study design, particle generation, and sample collection and preparation. A brief summary of the bioassays is also included.     

RELATIVE RATES OF EVAPORATIVE WATER LOSSES FROM OPEN AND VEGETATION COVERED WATER BODIES1

ABSTRACT: A review of literature pertaining to the relative rates of evaporation from vegetation covered and open water bodies is presented. The review indicates that the only reliable experiments capable of correctly addressing this question are those conducted in situ. Experiments of this nature show the ratio of vegetation covered (swamp) evaporation to open water evaporation to generally be less than unity over extensive surfaces and to only approach unity for vegetation that is young and vigorous. Recent experimental evidence presented within a theoretical context, however, indicates that even in the latter situation the ratio may never reach unity. Consequently, over large lakes and reservoirs, the presence of vegetation may actually be a water conservation mechanism, with the eradication of the vegetation leading to significantly increased evaporative water losses.     

DYNAMIC PROGRAMMING FOR OPTIMUM CONJUNCTIVE USE1

The Las Vegas, Nevada area like most semi-arid basins, was developed through exploitation of available ground-water resources. Area growth in this large valley has occurred in a scattered and sporadic manner with development both in incorporated areas and within the County. As a result, today there exist five major water suppliers which are: a water district, three municipalities, and a large corporation, in addition to numerous small water companies and thousands of domestic wells. In the past 20 years the area has grown from a population of less than 50,000 to over 300,000 today. The bulk of the water demand for this growth has been met from the ground-water resource and as a result the basin is being severely mined. Current extractions are over three times the estimated annual replenishment. Rapidly declining water levels are increasing the costs of water and are creating water shortages during periods of peak demand. To meet both the current and anticipated water demands, the Southern Nevada Water Supply Project is being constructed to import additional water from nearby Lake Mead. Agriculture in the area is very limited, and primarily uses reclaimed waste water for irrigation. The chief water demands in the area are thus municipal and industrial, with the former predominating. This study was designed to determine how best the Las Vegas Valley Water District, supplier of 80 percent of the domestic water, might integrate the use of the existing ground water and anticipated imported surface water. Additionally the consequences of application of certain provisions in the Nevada Water Law were examined to determine their effects on the ground-water system and costs of water. To achieve these objectives, a dynamic programming technique was utilized. The problem as formulated consists of a single decision variable, single state variable dynamic programming algorithm evaluated over a fifty-year planning horizon at monthly intervals. Three alternative solutions, with different ground-water law constraints are evaluated. In all solutions certain basic operating rules regarding ground-water pumping distribution and use of surface-water systems are kept constant. The problem is considered as deterministic in all respects. Recharge to ground water is assumed to equal the estimated average annual replenishment evenly distributed over the year and additionally is not considered to be a function of average basin ground water potential. The only surface supply, Lake Mead, is considered to operate at near constant elevation and not be subject to shortage conditions. In light of the size of Lake Mead, the Colorado River flow and the size of Nevada's allotment, 300,000 ac ft, the latter assumption is reasonable. Demand for water is considered as a known function of time. Optimization of conjunctive use for the Water District is based on the objective function of minimizing water production costs. Costs of distributing water are considered to be constant regardless of source, and so are not included. Also, fixed costs of amortizing the pipeline project and well fields are not considered. Results of the study are presented as a series of policy traces under each of the three alternatives considered. These traces describe the ground-water basin response under optimal operating conditions, given an estimate as to the present worth of ground-water pumping rights, and prescribe monthly water-procurement schedules for the operation of the Water District.     

Response of a coral-associated crustacean community to eutrophication

Seventy-five samples of the crustacean fauna associated with the coral Madracis mirabilis (Duchassaing and Michelotti) were obtained at five sites along the west coast of Barbados in 1985. Samples were analyzed to determine whether any community response to eutrophication was evident. Ordination (multidimensional scaling) and classification (group average clustering) based on Bray-Curtis dissimilarity measures separated the fauna of highly eutrophied sites from those that were less eutrophied. Dominance plots based on relative abundance and log-normal plotting methods were ineffective in distinguishing the fauna of eutrophied sites. The crustacean fauna responded to eutrophication mainly by reduction of density of animals. No differences in species richness, number of site endemic species or rare species were observed between highly eutrophied and less eutrophied sites. Nine indicator species of eutrophy were identified on the basis of strong density differences between sites.     

Barriers to interlock implementation

This commentary reviews current and past vehicle interlock programs for impaired driving offenders with a focus on the challenges that courts and motor vehicle departments face in attempting to implement mandatory programs as required by current federal legislation. There are few offenders in interlock programs compared to the large number of impaired drivers arrested each year. This suggests that, to increase participation, courts will have to threaten more severe sanctions for those offenders who reject interlock programs. A combination of electronic house arrest with interlock programs is suggested as a method of maximizing interlock use.     

Influence of seat foam and geometrical properties on BioRID P3 kinematic response to rear impacts

As the primary interface with the human body during rear impact, the automotive seat holds great promise for mitigation of Whiplash Associated Disorders (WAD). Recent research has chronicled the potential influence of both seat geometrical and constitutive properties on occupant dynamics and injury potential. Geometrical elements such as reduced head to head restraint, rearward offset, and increased head restraint height have shown strong correlation with reductions in occupant kinematics. The stiffness and energy absorption of both the seating foam and the seat infrastructure are also influential on occupant motion; however, the trends in injury mitigation are not as clear as for the geometrical properties. It is of interest to determine whether, for a given seat frame and infrastructure, the properties of the seating foam alone can be tailored to mitigate WAD potential. Rear impact testing was conducted using three model year 2000 automotive seats (Chevrolet Camaro, Chevrolet S-10 pickup, and Pontiac Grand Prix), using the BioRID P3 anthropometric rear impact dummy. Each seat was distinct in construction and geometry. Each seat back was tested with various foams (i.e., standard, viscoelastic, low or high density). Seat geometries and infrastructures were constant so that the influence of the seating foams on occupant dynamics could be isolated. Three tests were conducted on each foam combination for a given seat (total of 102 tests), with a nominal impact severity of Delta V = 11 km/h (nominal duration of 100 msec). The seats were compared across a host of occupant kinematic variables most likely to be associated with WAD causation. No significant differences (p < 0.05) were found between seat back foams for tests within any given seat. However, seat comparisons yielded several significant differences (p < 0.05). The Camaro seat was found to result in several significantly different occupant kinematic variables when compared to the other seats. No significant differences were found between the Grand Prix and S-10 seats. Seat geometrical characteristics obtained from the Head Restraint Measuring Device (HRMD) showed good correlation with several occupant variables. It appears that for these seats and foams the head-to-head restraint horizontal and vertical distances are overwhelmingly more influential on occupant kinematics and WAD potential than the local foam properties within a given seat.     

The impact of mandatory versus voluntary participation in the Alberta ignition interlock program

Research has demonstrated that participation in an interlock program significantly reduces the likelihood of subsequent driving while intoxicated (DWI) convictions at least so long as the interlock device is installed in the vehicle. Despite the growing number of jurisdictions that allow interlock programs and the demonstrated success of these programs, the proportion of DWI offenders who actually have the device installed is minimal. In an effort to increase the proportion of offenders using interlocks, some jurisdictions require offenders to install an interlock as a condition of license reinstatement whereas others merely offer offenders a reduction in the period of hard suspension if they voluntarily participate in an interlock program. The objective of the present study was to determine the extent to which voluntary interlock participants are more or less successful in terms of subsequent recidivism than those for whom interlock program participation has been mandated. The issue was addressed using data from the interlock program in Alberta, Canada, which provides for both mandatory and voluntary participation. The recidivism experience of voluntary and mandatory interlock participants was examined both during and after the period of interlock installation. Cox regression revealed that, after controlling for (or equating) the number of prior DWI offenses, the survival rates of DWI offenders who were ordered to participate in the interlock program did not differ from those of voluntary participants. These results suggest that further use of mandatory interlock programs should be just as successful as voluntary programs when offenders share characteristics with those studied in Alberta.