Dose-response relationships in mutagenicity assays including an appropriate positive control group: a multiple testing approach

The objective of mutagenicity assays in regulatory toxicology is the decision on non-mutagenicity or mutagenicity. An inherent problem of statistical tests is the possibility of false decisions, i.e., a mutagenic substance will be falsely labeled as non-mutagenic or a non-mutagenic substance will be falsely labeled as mutagenic. These probabilities of false negative (consumer's risk=type II error) and/or false positive decision (producer's risk=type I error) can be limited by using suitable testing procedures as well as a design including an appropriate positive control. Using the proof of hazard concept the well-known many-to-one procedures with total order restriction for increasing effect differences are used, while using the proof of safety concept procedures on equivalence with total order restriction are discussed. Both approaches are demonstrated on a real data example.     

The phytotoxic effect of C(1)/C(2)-halocarbons and trichloroacetic acid on the steppe plant Artemisia lerchiana

Artemisia lerchiana is a wormwood species of the Central Asian steppe regions, where it completely cover whole areas. For the first time it was possible to show through field experiments that C(1)/C(2) halocarbons (VCHCs), such as chloroform (CHL), tetrachloroethene (PER) and hexachloroethane (HEX), can be taken up by test plants of the species A. lerchiana via the soil/root pathway and metabolised inter alia into trichloroacetic acid (TCA) under semi-aride conditions. At the same time, chlorophyll a fluorescence measurements carried out on the test plants revealed a phytotoxic influence on plant vitality (max. decline in vitality of 52% with application of CHL) and less efficient energy flows in the photosynthesis mechanism of the A. lerchiana test plants. The authors examine possible links between the simultaneous appearance of VCHCs and additional drought stress in the acceleration of desertification processes.     

The annual course of TCA formation in the lower troposphere: a modeling study

We present a modeling study investigating the influence of climate conditions and solar radiation intensity on gas-phase trichloroacetic acid (TCA) formation. As part of the ECCA-project (Ecotoxicological Risk in the Caspian Catchment Area), this modeling study uses climate data specific for the two individual climate regimes, namely "Kalmykia" and "Kola Peninsula". A third regime has also been included in this study, namely "Central Europe", which serves as a reference to somehow more moderate climate conditions. The simulations have been performed with a box modeling package (SBOX, photoRACM), which uses Regional Atmospheric Chemistry Mechanism (RACM) as its chemistry scheme. For this model a mechanism supplement has been developed including the reaction pathways of methyl chloroform photooxidation. The investigations are completed by a detailed sensitivity study addressing the impact of temperature and relative humidity. Atmospheric OH and HO2 concentrations and the NOx/HO2 ratio were identified as the governing quantities controlling the TCA formation trough methyl chloroform oxidation in the gas phase. Model calculations show a TCA production rate ranging between almost zero and 6.5 x 10(3) molecules cm(-3) day(-1) depending on location and season. In the Kalmykia regime the model predicts mean TCA production rates of 1.3 x 10(-4) and 5.4 x 10(-5) microg m(-3) year(-1) for the urban and rural environment, respectively. From the comparison of model calculations with measured TCA burdens in the soil ranging between 130 g m(-3) and 1750 g m(-3) we conclude that TCA formation through methyl chloroform photooxidation in the gas-phase is probably not the principal atmospheric TCA source in this region.     

Rating accident models and investigation methodologies

This is a report of research to identify, rate, and rank accident models and accident investigation methodologies. Models and methodologies used in 17 selected government agencies were examined. The examination disclosed 14 accident models and 17 different accident investigation methodologies in those agencies. To determine their relative merit, evaluation criteria and a rating scheme were developed from user data, statutes, applications, and work products, and each model and methodology was rated. The ratings indicated significant differences in their relative merit. The highest rated model and methodology were tested to determine if the estimated ratings were supported by observable differences in actual performance and to compare investigative results against previously reported cases. Differences found prompted further examination of the benefits and problems that would result from implementation of the preferred model and methodology. Additional exploration of comparative performance measurement techniques disclosed further differences affecting the selection decisions. The models, methodologies, criteria, ratings, rankings, test results, and initial measurement findings are summarized in this report. Issues ranging from oversimplification to ethical questions were discovered during this work. The findings strongly suggest that significant accident investigation program changes should be considered in agencies and organizations using lower-ranked accident models or investigation methodologies and that a compelling need exists for more exhaustive research into accident model and accident investigation methodology selection decisions.     

Sustainable value assessment of farms using frontier efficiency benchmarks

Appropriate assessment of firm sustainability facilitates actor-driven processes towards sustainable development. The methodology in this paper builds further on two proven methodologies for the assessment of sustainability performance: it combines the sustainable value approach with frontier efficiency benchmarks. The sustainable value methodology tries to relate firm performance to the use of different resources. This approach assesses contributions to corporate sustainability by comparing firm resource productivity with the resource productivity of a benchmark, and this for all resources considered. The efficiency is calculated by estimating the production frontier indicating the maximum feasible production possibilities. In this research, the sustainable value approach is combined with efficiency analysis methods to benchmark sustainability assessment. In this way, the production theoretical underpinnings of efficiency analysis enrich the sustainable value approach. The methodology is presented using two different functional forms: the Cobb–Douglas and the translog functional forms. The simplicity of the Cobb–Douglas functional form as benchmark is very attractive but it lacks flexibility. The translog functional form is more flexible but has the disadvantage that it requires a lot of data to avoid estimation problems. Using frontier methods for deriving firm specific benchmarks has the advantage that the particular situation of each company is taken into account when assessing sustainability. Finally, we showed that the methodology can be used as an integrative sustainability assessment tool for policy measures.     

Failure to confirm previous identification of two putative museum specimens of the Atlantic sturgeon, Acipenser sturio, as the Adriatic sturgeon, A. naccarii

MtDNA analyses were employed to examine the species identification of three preserved museum sturgeon specimens from the River Guadalquivir, two of which were originally described as Acipenser sturio L., 1758 by Hernando (1975; Doñana, Acta Vertd 2: 263–264). Later the same two specimens were identified as A. naccarii Bonaparte, 1836 by Garrido-Ramos et?al. (1997; Mar Biol 129: 33–39) on the basis of morphometric and nuclear DNA analyses. Three different laboratories using independent techniques were unsuccessful in extracting authentic DNA from tissue samples from the three specimens and in obtaining any verifiable PCR product. We cannot confirm the previous molecular identification of two of these specimens by Garrido-Ramos et?al. as A. naccarii. We suggest that these specimens are indeed A. sturio.     

Land Use,Geology, Enrichment,and Stream Biota in the Eastern Ridge and Valley Ecoregion: Implications for Nutrient Criteria Development1

Abstract: The eastern panhandle region of West Virginia is entirely within the Appalachian Ridge and Valley ecoregion. It is underlain by limestone in the eastern part and by shale and sandstone in the western part. Agricultural and urban development has affected the condition of the streams of this region. We examined samples from 165 stations in the Ridge and Valley, collected from 1998 to 2004. Land use, geological characteristics, physical and chemical parameters, and algal and macroinvertebrate assemblages were used to identify potential stressors that affect streams in the region. Our analyses indicated that both human land uses and ecoregional differences led to elevated nutrient concentrations in streams of the study areas. Multiple regression analyses indicated that both agricultural and urban land use in the watershed were associated with high nutrient concentrations (NO₂₊₃, total nitrogen, and total phosphorus) in streams. These elevated nutrient concentrations have led to increased algal biomass, increased trophic state, and degradation of macroinvertebrate community in the streams. Values of the West Virginia Stream Condition Index, as well as several other benthic macroinvertebrate metrics, decreased with increased nutrient concentrations and conductivity, especially in the limestone region. When regional differences were partitioned out in the analysis, nutrient concentrations became the strongest stressor in the limestone region while conductivity exhibited less of an effect on macroinvertebrate metrics. Meanwhile, periphyton diagnostic metrics also responded to increased nutrient concentrations, suggesting nutrients could be a cause of biological degradation in the Eastern Ridge and Valley region. Multiple approaches and multiple lines of evidence (reference approach and stressor‐response approach) were applied to develop nutrient benchmarks for different geological regions in the study watershed.     

Biomonitoring of airborne mercury with perennial ryegrass cultures

A biomonitoring network with grass cultures was established near a chlor-alkali plant and the mercury concentration in the cultures were compared with the average atmospheric total gaseous mercury (TGM). Biomonitoring techniques based on different exposure periods were carried out. When comparing the mercury concentration in the grass cultures, both the average atmospheric TGM concentration during exposure and the exposure time determined to a large extent the accumulation rate of TGM. The maximum tolerable level of mercury in grass (approximately equal to 110 microg kg(-1) DM) corresponds with an average TGM concentration of 11 ng m(-3) for 28 days exposure. The background concentrations in grass were on an average 15 microg kg(-1) DM and the effect detection limit (EDL) was 30 microg kg(-1) DM. This value corresponds with an average TGM concentration of 3.2 and 4.2 ng m(-3) for 28 and 14 days exposure, respectively, which is in turn the biological detection limit (BDL) of ambient TGM. Exposures for 7 days were less appropriate for biomonitoring.