Acceptable Contamination Levels Research Articles

The role of meteoritics in spaceflight missions and vice versa

Abstract— Research on extraterrestrial materials plays a critical role in formulating the science rationale and design for spacecraft missions, and, conversely, spaceflight holds great promise for solving perplexing problems in meteoritics. The connections between meteoritics and sample‐return missions are obvious: Meteorite research can define sampling strategies, the capabilities of sampling devices, acceptable levels of chemical contamination and physical alteration of samples, and the conditions under which samples are stored prior to and during recovery. For their part, sample‐return missions can provide geologic context for meteorites, increased sampling diversity (including materials not sampled as meteorites, such as unconsolidated regolith, ices, and atmosphere), calibration for crater‐counting chronology, and ground truth for remote sensing measurements of meteorite parent bodies. Meteoritics also relates to spacecraft flyby, rendezvous, and lander missions that do not necessarily return samples. Specific illustrations of this mutual relationship, based on a selection of recent or planned spacecraft missions include: Identifying source asteroid classes for ordinary and carbonaceous chondrites and reconstructing their thermal and collisional histories (Galileo, NEAR, Clementine II, and Muses‐C); determining the extent to which cometary dust and interstellar grains are found as interplanetary dust particles and assessing volatile abundances, isotopic compositions, and molecular species in cometary nuclei (Stardust and Rosetta); understanding the compositions of ancient Martian crust and the mantle sources for SNC meteorites, as well as inventorying the planet's volatile reservoirs and interactions (Mars Pathfinder, Mars Global Surveyor, and Mars Volatiles and Climate Surveyor); assessing whether lunar meteorites provide a more representative chemical sampling of the highlands crust and of mare volcanism than do Apollo samples (Galileo, Clementine, and Lunar Prospector). Spaceflight is the first priority of the space agencies that fund most research on extraterrestrial materials, and the continued level of support for such research may be linked, in part, to its use in exploration by spacecraft.

Evaluation of Procedures for Production of Dust Samples for Biomedical Research

Abstract There are several logical objectives for dust samples used in biomedical research. Obviously, the dusts used should closely resemble natural mine dusts with respect to particle size distribution, particle shape, and composition. These characteristics must be consistent from sample to sample. Usually the relative freshness of the dust is also of primary concern. A generalized procedure for producing dust by single- or multiple-stage grinding and classification has been developed. Three laboratory-scale grinding devices—a Bleuler rotary mill (ring and puck grinder), a Retsch high speed planetary mill, and a Sweco vibratory mill—have been tested. The results have been evaluated in terms of the product size distribution, particle shape, and contamination introduced in the grinding process. All three devices have been found to be capable of producing appropriate size distributions at acceptable contamination levels. Multistage grinding with intermediate classification steps generally provides angular ...

The Usefulness of the Sputum Gram Stain in the Diagnosis of Pneumonia

The value of the sputum Gram stain in the diagnosis of pneumonia is controversial. Use of the Gram stain to screen sputum samples for contamination before culture is well accepted, but the ability of the Gram stain to predict the microbial cause of pneumonia and guide antibiotic therapy is less certain. Studies in which the criteria for Gram stain interpretation are clearly identified indicate that, when a specimen meets acceptable levels of purulence and salivary contamination and shows a predominant organism, the Gram stain predicts the results of sputum, transtracheal aspirate, and blood cultures with high specificity. Moreover, Gram stains meeting these criteria have been shown to be accurate guides to antibiotic treatment. In intubated patients, the Gram stain of lower respiratory secretions collected by endotracheal aspirate, protected specimen brush, or bronchoalveolar lavage provides immediate and reasonably specific information regarding the presence of pneumonia and the causative agent. However, many patients with pneumonia do not produce an adequate sputum specimen, and not all Gram stains show a predominant organism. Furthermore, Gram stains are often poorly prepared or misinterpreted by inexperienced clinicians. Common errors include interpreting an inadequate or improperly stained specimen, overlooking Gram-negative bacilli (particularly Haemophilus influenzae), and mistakenly identifying all Gram-positive organisms as pneumococci. Thus the sputum Gram stain is helpful in the diagnosis of pneumonia when it is interpreted according to specific criteria and when attention is paid to the avoidance of common pitfalls. In the patients from whom a diagnostic specimen is available, the sputum Gram stain can be an accurate, low-cost guide to effective, narrow-spectrum antibiotic therapy.

Determination of Lead in Beer Using Zeeman Background-Corrected Graphite Furnace Atomic Absorption Spectrometry

Because of its toxicity and the potential for adverse health effects, lead has attracted widespread interest in its occurrence in the environment, drinking water, and many comestibles, including alcoholic beverages. Its accurate analysis at very low levels in complex matrices such as beer is subject to many difficulties from interferences and demands specialized equipment and techniques. Graphite furnace atomic absorption spectrometry has been successfully used for the analysis of lead in biological samples and has previously been applied to beer. In recent times, the reassessment of lead's human health implications has prompted North American regulatory agencies to lower the acceptable levels of lead contamination in the environment and, particularly, in drinking water. Consequently, this has renewed the requirements for lower detection limits and improved accuracy in analyses. Earlier studies have shown that with modern-day standards for equipment and materials used in beer production and packaging, beers contain only trace levels of lead and generally were below the newly established guidelines for drinking water. There is need, however, for improved accuracy in lead determinations. This method achieves that by combining an appropriate matrix modifier, platform atomization, peak area integration, Zeeman background correction, insertion of a cool-down step before atomization, and the use of the alternate wavelength (283.3 nm) for lead. The method has a limit of detection of 0.87 μg/L and a limit of determination of 2.1 μg/ L.

Determination of Lead in Beer Using Zeeman Background-Corrected Graphite Furnace Atomic Absorption Spectrometry

Because of its toxicity and the potential for adverse health effects, lead has attracted widespread interest in its occurrence in the environment, drinking water, and many comestibles, including alcoholic beverages. Its accurate analysis at very low levels in complex matrices such as beer is subject to many difficulties from interferences and demands specialized equipment and techniques. Graphite furnace atomic absorption spectrometry has been successfully used for the analysis of lead in biological samples and has previously been applied to beer. In recent times, the reassessment of lead's human health implications has prompted North American regulatory agencies to lower the acceptable levels of lead contamination in the environment and, particularly, in drinking water. Consequently, this has renewed the requirements for lower detection limits and improved accuracy in analyses. Earlier studies have shown that with modern-day standards for equipment and materials used in beer production and packaging, beers contain only trace levels of lead and generally were below the newly established guidelines for drinking water. There is need, however, for improved accuracy in lead determinations. This method achieves that by combining an appropriate matrix modifier, platform atomization, peak area integration, Zeeman background correction, insertion of a cool-down step before atomization, and the use of the alternate wavelength (283.3 nm) for lead. The method has a limit of detection of 0.87 μg/L and a limit of determination of 2.1 μg/ L.

Advanced Technology Processing and State-of-the-art Solutions to Cleaning, Contamination Control, and Integration Problems

ABSTRACTUltraclean semiconductor processes were developed for ULSI technologies to significantly reduce metallics, foreign materials, and to preserve silicon surface morphology. State-of-the-art detection techniques (Elymat, TXRF, VPD, and SPV) were implemented in all critical process sectors. Acceptable levels of metallic contamination were derived from previous experience and from published work on this subject relating metallic contamination levels to gate oxide reliability and retention time.A comprehensive diagnostic/characterization system was utilized in evaluating a wide variety of test structures emulating key device process interactions. Advanced techniques were employed for measurement of reliability and surface morphology. Also root causes for all integration problems are identified.

Soil, Groundwater, and Plant Resources in Sludge‐Treated Bigtooth Aspen Sapling Ecosystems

AbstractSludge fertilization of a 10‐yr‐old coppice bigtooth aspen (Populus grandidentata Michx.) with 500 to 600 kg ha−1 N, and associated nutrients, resulted in plant, soil, and groundwater responses that are important silviculturally, ecologically, and environmentally. Results included: sapling biomass growth responses of 66% over 4 yr; ecologically significant and environmentally acceptable understory, ground flora, and regeneration responses; increased amounts of soil nutrients in available, cycling, and physiologically active forms; storage of nutrients in the forest floor but not the surface and subsurface soil; increased nutrients in soil water; and significant but environmentally acceptable levels of groundwater contamination. Responses are explained as perturbations in normal ecological processes. Aspen growth responses continued after 4 yr, but are expected to moderate to near unfertilized levels unless nutrients are reapplied.

Effect of Ionized Impurities at Heterointerface on Concentration and Mobility of Two-Dimensional Electrons in Selectively Doped Heterojunction Structures

The concentration N S and the low-temperature mobility µ of two-dimensional electron gas in GaAs/AlGaAs selectively doped heterojunctions have been studied theoretically and experimentally for the case where ionized impurities are present at heterointerfaces. It is found that N S scarcely changes when the concentration N IF of interfacial impurities is below 1×1011 cm-2, but it rapidly disappears at higher values of N IF if the impurities are of the acceptor type. In contrast, the mobility is found to decrease substantially even when N IF is as low as 109 cm-2. Based on these results, a quantitative guideline is drawn on the acceptable level of contamination in ultrahigh-vacuum wafer processings including molecular beam epitaxial regrowth.

Materials and failure analysis methods and systems used in the development and manufacture of silicon integrated circuits

The trends within the electronic industry toward decreasing device dimension and increasing integrated circuit device density are driving developments in analytical technology. The lateral resolution and sensitivity of present generation analytical equipment are challenged by device feature dimensions. In addition, acceptable contamination levels are decreasing. Some of the analysis methods facing this challenge are total reflection x-ray fluorescence, ellipsometry, Auger microprobe, and secondary-ion-mass spectrometry. Networked analytical systems are presently used to improve cycle time for analysis. This type of system allows a focused ion beam tool or a scanning electron microscope to quickly move to previously located electrically active defect. The focus of this presentation will be on the challenges facing materials characterization and failure analysis methods. The discussion will include the effect of networked analytical systems on both problem solving methodology and the potential role of new characterization methods such as heavy-ion backscattering spectrometry and post-ionization of sputtered neutrals.

Assessment of health risks in the redevelopment of contaminated land

Guide-lines and codes of practice for the redevelopment of contaminated sites should address acceptable residual levels of contamination of substances which are potentially harmful to the prospective user of the site. The Paper discusses the commonly used rules and guide-lines with reference to this issue, and highlights some apparent anomalies. The difficulties involved in taking proper account of the toxicological significance of contaminants are explored. The practicability of codes and standards quantifying trigger and/or target levels of contaminants is also addressed. Although the scope for quantitative codes of practice is limited by the probable individuality of any particular case, procedures can and should be codified. More of the existing data on substances used in industrial processes and their possible harmful effects could usefully be collated into a form more amenable to the appraisal of contaminated sites. Les conseils techniques et les règles de pratique concernant l'utilisation nouvelle des emplacements pollues devraient fixer les niveaux de pollution acceptables des matières nuisibles à l'utilisateur éventuel de l'emplacement. L'article discute les règles et les conseils techniques généralement employés à ce sujet et souligne les anomalies évidentes. On étudie les problèmes rencontrés dans l'attribution aux polluants d'un seuil de toxicité convenable et on examine aussi la praticabilité des règles et des normes qui quantifient les niveaux de déclenchement et/ou d'objectifs des polluants. Bien que les limites des règles de pratique quantitatives soient limitées par la nature individuelle de chaque cas particulier, les procédures pourraient et devraient être codifiées. Il serait utile de faire la corrélation des données disponsibles concernant les matières employées dans les opérations industrielles et leurs effets nuisibles potentiels afin d'arriver à un système plus satisfaisant pour l'évaluation des emplacements pollués.

Human exposures from dioxin in soil—a meeting report

A 1984 risk assessment identified 1 part per billion (ppb) of dioxin in soil as a "level of concern" at Times Beach, Mo. The authors of the assessment had to rely on many assumptions in their analysis, but since that time, a number of investigators have obtained data that bear directly on estimating exposures from substances in soil. Partly because of the assumptions and partly because of the site-specific nature of their analysis, the authors of the Times Beach risk assessment cautioned against the adoption of 1 ppb as a delineator between acceptable and nonacceptable levels of contamination. Those cautions have been more frequently ignored than honored, and 1 ppb has become a de facto standard. In November 1989, the Center for Risk Management at Resources for the Future hosted 50 experts at a workshop that heard and discussed published and new research about exposure estimates and measures. The 1984 assessment identified soil ingestion by toddlers as the single most important source of exposure to dioxin in soil; it assumed that toddlers ingested 10 g soil daily. Research discussed at the workshop shows that the average child ingests about 0.04 g soil daily, but that 1 of 320 studied children ingested 5 g. These findings leave open the risk management decision about whether acceptable exposure levels should be established to protect the average child or the extreme child. Furthermore, the absence of children from commercial and industrial sites led to suggestions that higher concentrations of dioxin are acceptable in soil at such sites. Some workshop participants objected to those suggestions because of the difficulty of assuring that such sites would not revert to residential use in the future. Whether deed restrictions are sufficient to prevent such reversions was seen as an important research topic. Workshop participants repeatedly discussed the importance of site-specific data in estimating exposures: Measured half-lives of dioxin in different soils range from 18 mo to greater than 100 yr; bioavailability from various soils differs by at least 20-fold; and the amounts of soil ingested by grazing cattle can differ 20-fold depending on conditions. Workshop participants agreed upon some suggestions for research and generally favored the development of guidelines for exposure assessment that would allow consideration of site-specific information. Furthermore, they generally agreed that no single concentration should be taken as a level of concern. Instead, levels should be established that consider the planned uses of the sites.

A pathway analysis approach for determining acceptable levels of contamination of radionuclides in soil.

A methodology for determining acceptable levels for decontamination of soil containing radionuclides at waste sites is described. This methodology calculates the annual radiation dose that an individual receives while living on property that has been decommissioned and decontaminated. Pathways of exposure include direct radiation from ground surfaces, ingestion of contaminated food, inhalation of resuspended radionuclides and drinking contaminated water. Results calculated using this methodology were compared with U.S. Department of Energy (DOE) guidelines for a southeastern U.S. site. There is good agreement between the two methods provided similar assumptions are used.

Characterization of the CFC issues relating to the air conditioning and refrigeration industry part 2: standards for acceptable levels of contaminants in refrigerants

This Paper deals with the ozone depletion and the CFC (chlorofluorocarbon) as they affect the air conditioning and refrigeration industry. The past, the current and the future will be covered with respect to regulations and industry standards for cleanliness of refrigerants. Two ad hoc committees of the Air-Conditioning and Refrigeration Institute (ARI) were formed in January 1987: one to address the CFC regulations and the other to address the acceptable level of contaminants in refrigerants. This Paper will summarize the workings of the second committee.

Food Tolerances and Action Levels: Do They Adequately Protect Children?

Developmental embryology has long indicated the heightened susceptibility of young organisms to toxicants. Despite some detailed scientific research on differential responses between young and adult organisms, most regulatory standards for exposure to environmental contaminants in food are set for the more tolerant adults rather than for the more sensitive younger populations. Environmental contaminants in foods are of particular concern for three major reasons: First of all, aside from selfsufficient farmers, individuals typically have limited control over their exposure; everyone must eat food to live. Secondly, food both nourishes for the present and introduces potentially long-lasting substances that affect future development and reproductive capacities. Finally, average doses relative to body size for the young are substantially higher than those for adults. The higher average exposure of the young and unborn, together with their greater sensitivity, suggests the need for concerted regulatory attention. Standards set only for adults may not protect the young. This threepart paper briefly details federal monitoring for contaminants in food; federal methods for establishing acceptable levels of contaminants in food; and some scientific research on the differential responses of young and adult organisms to toxicants. Chemical contaminants of food derive from multiple sources, including indus-

Heavy metals in the soils Euro-Arctic territories

The features of metal accumulation by the Arctic soils are analyzed. The data of a comparative analysis content of total and metals mobile forms in natural and anthropogenic soils in the Euro-Arctic region are presented. Such areas studied: Frans Joseph Land, Spitsbergen, Solovetsky, Novaya Zemlya, Kolguev Island, cape Kanin Nos, Varnek, Sosnovets Island. The chemical analysis was carried out with the use of modern instrumental methods and certified methods: by X-ray fluorescence and atomic absorption methods. The degree of soil contamination was assessed by the maximum permissible concentrations exceeding and biogeochemical coefficients. Analysis of the experimental data has shown that metals accumulation by different types of soils is ambiguous: zinc and lead predominate in the arctic and tundra bog soils, manganese and cobalt in the non-gley and gley tundra soils, and cobalt and lead in the podzolic and alluvial meadow soils. Correlation analysis revealed the dependence of the metals accumulation with such physicochemical parameters as the content of physical clay, organic matter and the pH of the soil solution. According to the total pollution index (Zc), calculated related to clark, a dangerous level of contamination have the Arctic soils of Pyramid settlement, tundra non-gley soils of cape Belyy Nose, alluvial meadow acidic soils of Dixon settlement and peat soils of Sosnowiec Island. Tundra gley soils in Cape Kanin Nos have a moderately dangerous level of pollution. At the same time, the soils have an acceptable level of contamination with metals mobile forms. Practically all of the examined elements are represented by non-mobile forms, which are confirmed by the high value of the protective soils coefficients.

The size distribution of particles contaminating parenteral solutions

Some problems in the formulation of a standard for the minimum acceptable level of particulate contamination in large volume parenteral solutions are discussed. The proposed Australian Biological Standards Laboratory standard, in which an electrical method is used to detect particulate matter, makes some assumptions about the nature of the particle-size distribution. These are critically examined from the published results. Experimentally, it is confirmed that the relationship between particle diameter D and number N is dN/d(D)=CD–M where C and M are constants. A membrane filtration method for the determination of particle numbers is shown to have serious limitations for the type of solution at present available, as there are few particles present that are larger than the lowest practical limit of detection (10 to 15 µm).

Microbial content of nonsterile therapeutic agents containing natural of seminatural active ingredients.

The relationship was investigated between various chemical or pharmaceutical production processes and the extent of microbial contamination, of natural origin, of the resulting products. The products contained active ingredients of vegetable, enzymatic, or animal origin. It was concluded that (i) vegetable products practically free from microbes can be produced if the proper manufacturing steps are taken; (ii) sterilization of the media used to manufacture antibiotics, etc., produces products with little contamination; and (iii) products containing extracts of animal organs require careful refrigeration and addition of preservatives to produce acceptable levels of microbial contamination.

Microbial Content of Nonsterile Therapeutic Agents Containing Natural or Seminatural Active Ingredients

The relationship was investigated between various chemical or pharmaceutical production processes and the extent of microbial contamination, of natural origin, of the resulting products. The products contained active ingredients of vegetable, enzymatic, or animal origin. It was concluded that (i) vegetable products practically free from microbes can be produced if the proper manufacturing steps are taken; (ii) sterilization of the media used to manufacture antibiotics, etc., produces products with little contamination; and (iii) products containing extracts of animal organs require careful refrigeration and addition of preservatives to produce acceptable levels of microbial contamination.