On the conversion of solid cancer excess relative risk into lifetime attributable risk

Risk coefficients representing the lifetime radiation-induced cancer mortality (or incidence) attributable to an exposure to ionizing radiation, have been published by major international scientific committees. The calculations involve observations in an exposed population and choices of a standard population (for risk transportation), of suitable numerical models, and of computational techniques. The present lack of a firm convention for these choices makes it difficult to inter-compare risk estimates presented by different scientific bodies. Some issues that relate to a necessary harmonization and standardization of risk estimates are explored here. Computational methods are discussed and, in line with the approach utilized by ICRP, conversion factors from excess relative risk (ERR) to lifetime attributable risk (LAR) are exemplified for exposures at all ages and for occupational exposures. A standard population is specified to illustrate the possibility of a simplified standard for risk transportation computations. It is suggested that a more realistic perception of lifetime risk could be gained by the use of coefficients scaled to the lifetime spontaneous cancer rates in the standard population. The resulting quantity lifetime fractional risk (LFR) is advantageous also because it depends much less on the choice of the reference population than the lifetime attributable risk (LAR). Received: 5 April 2001 / Accepted: 1 July 2001     

Monte Carlo mixture model of lifetime cancer incidence risk from radiation exposure on shuttle and international space station

Estimating uncertainty in lifetime cancer risk for human exposure to space radiation is a unique challenge. Conventional risk assessment with low-linear-energy-transfer (LET)-based risk from Japanese atomic bomb survivor studies may be inappropriate for relativistic protons and nuclei in space due to track structure effects. This paper develops a Monte Carlo mixture model (MCMM) for transferring additive, National Institutes of Health multiplicative, and multiplicative excess cancer incidence risks based on Japanese atomic bomb survivor data to determine excess incidence risk for various US astronaut exposure profiles. The MCMM serves as an anchor point for future risk projection methods involving biophysical models of DNA damage from space radiation. Lifetime incidence risks of radiation-induced cancer for the MCMM based on low-LET Japanese data for nonleukemia (all cancers except leukemia) were 2.77 (90% confidence limit, 0.75-11.34) for males exposed to 1 Sv at age 45 and 2.20 (90% confidence limit, 0.59-10.12) for males exposed at age 55. For females, mixture model risks for nonleukemia exposed separately to 1 Sv at ages of 45 and 55 were 2.98 (90% confidence limit, 0.90-11.70) and 2.44 (90% confidence limit, 0.70-10.30), respectively. Risks for high-LET 200 MeV protons (LET=0.45 keV/micrometer), 1 MeV alpha-particles (LET=100 keV/micrometer), and 600 MeV iron particles (LET=180 keV/micrometer) were scored on a per particle basis by determining the particle fluence required for an average of one particle per cell nucleus of area 100 micrometer(2). Lifetime risk per proton was 2.68x10(-2)% (90% confidence limit, 0.79x10(-3)%-0. 514x10(-2)%). For alpha-particles, lifetime risk was 14.2% (90% confidence limit, 2.5%-31.2%). Conversely, lifetime risk per iron particle was 23.7% (90% confidence limit, 4.5%-53.0%). Uncertainty in the DDREF for high-LET particles may be less than that for low-LET radiation because typically there is very little dose-rate dependence. Probability density functions for high-LET radiation quality and dose-rate may be preferable to conventional risk assessment approaches. Nuclear reactions and track structure effects in tissue may not be properly estimated by existing data using in vitro models for estimating RBEs. The method used here is being extended to estimate uncertainty in spacecraft shielding effectiveness in various space radiation environments.     

A micro-scale method for determining relative metal-binding affinities of proteins

This article describes a quick and easy method for determining relative binding affinities between proteins and metal ions. The method is based on separating unbound metal ions from metal ions bound to protein by ultrafiltration using microcentrifuge ultrafiltration units. Bovine serum albumin (BSA) was used as the test protein and the relative affinity towards divalent metal ions was found to be Cu²⁺>Zn²⁺>Cd²⁺>Pb²⁺>Ni²⁺>Co²⁺, which corresponds to the relative orders reported in the literature.     

Simple multi-filter sensors for determining relative radiation in the sea and in freshwater

The design, construction, testing and use of an underwater relative radiation sensor are described. The sensor incorporates four narrow band interference filters and a broad band (400–700 nm) filter so that variation in spectral quality as well as visible light attenuation can be determined. Comparison with a proprietary, calibrated sensor, a Macam SD 101, indicates the reliability of the relative radiation sensor of the range 1 to >300 Wm^–2 P.A.R. and to a depth of at least 20 m. Brief reference is made to selected data from a variety of aquatic habitats. A general table for the comparison of radiation and illumination units is presented.     

A nonintrusive method for determining relative body fat in free-ranging monkeys

A procedure is described for designing simple obesity rating scales for use with free-ranging rhesus monkeys (Macaca mulatta). Ratings are based on observers' judgments of degree of overall obesity of individual monkeys. The procedure was tested separately on samples of males and females over 2 successive years. Within each of these four samples, observers' judgments were both highly reliable and highly correlated with actual measures of body weight and with estimates of body fat based on morphometric measures, including the Quetelet index. To test the degree to which scores from different applications of the scale could be compared with one another, regression functions were calculated for scale vs. the Quetelet index and for scale vs. body weight for each application. No significant differences were found among the four regression functions for scale vs. the Quetelet index for fully grown adult monkeys. This suggested that observers' judgment criteria with regard to this measure were sufficiently stable across the four test applications to allow meaningful comparison of scores. Comparable analyses for body weight suggested that observers' judgment criteria were stable over time but not between sexes. These data suggest that observers had been successful in attending more closely to obesity than to body weight. Obesity scales have many potential uses both in the field and in captivity provided they are adequately tested before use.     

A computer-assisted image processing method for determining relative cardiac function in the chick embryo.

The general objective of this study was to develop a noninvasive method for efficiently and reproducibly determining relative cardiac function parameters in the chick embryo. The specific objectives of the study were 1) to develop several methods for computer-assisted image processing and quantitation of relative intraventricular blood volumes in the 3-day-old embryonic chick heart and 2) to compare methods for precision and with a previously established manual processing method. Images of the embryonic chick heart in ovo were recorded on videocassette tape, digitized, and enhanced by computer-aided histogram equalization. The area occupied by blood within the common ventricle was extracted by region-growing and spurious region removal algorithms and defined by the determination of edge-pixel coordinates. Edge-pixel coordinates of the longitudinal and transverse axes of the common ventricular blood region were located by three different methods, the lengths of the axes calculated, and volumes computed from the equation for determining volume of a prolate spheroid. Twenty-five images of the embryonic heart were randomly selected and processed. Volumes were calculated with each of the three methods on six different occasions. A coefficient of variation was calculated for each method. The intraobserver mean coefficient of variation for each method was 7.4%. When a 2-way ANOVA was conducted, mean coefficients of variation did not differ significantly for the three methods. However, computer processing (in addition to significantly reducing the time required to generate data) reduced the coefficient of variation observed in manual processing by 56.5%.     

A nested case-control study of lung cancer risk and ionizing radiation exposure at the portsmouth naval shipyard

Results have been inconsistent between studies of lung cancer risk and ionizing radiation exposures among workers at the Portsmouth Naval Shipyard (PNS). The purpose of this nested case-control study was to evaluate the relationship between lung cancer risk and external ionizing radiation exposure while adjusting for potential confounders that included gender, radiation monitoring status, smoking habit surrogates (socioeconomic status and birth cohort), welding fumes and asbestos. By incidence density sampling, we age-matched 3,291 controls selected from a cohort of 37,853 civilian workers employed at PNS between 1952 and 1992 with 1,097 lung cancer deaths from among the same cohort. Analyses using conditional logistic regression were conducted in various model forms: log-linear (main), linear excess relative risk (ERR), and categorical. Lung cancer risk was positively associated with occupational dose (OR = 1.02 at 10 mSv; 95% CI 0.99- 1.04) but flattened after the inclusion of work-related medical X-ray doses (OR = 1.00; 95% CI 0.98-1.03) in multivariate analyses. Similar risk estimates were observed in the linear ERR model at 10 mSv of cumulative exposure with a 15-year lag.     

A simple method for determining the relative activities of individual peroxidase isozymes in a tissue extract

A peroxidase specific zymogram staining procedure has been designed which not only locates peroxidase isozymes which have been resolved electrophoretically, but simultaneously estimates the relative activity of each peroxidase isozyme in the system under study. This quantitative assay of individual peroxidase isozymes is chronometric; the time required for the appearance of a peroxidase band is inversely proportional to its activity. By recording the time required for the appearance of each peroxidase isozyme in a tissue extract, the percent contribution each isozyme makes toward the total peroxidatic activity of that tissue can readily be determined.     

Quantitative microbiological risk assessment: principles applied to determining the comparative risk of salmonellosis from chicken products

Since causal links have been established between food-borne illness and particular microorganisms, it has been possible to assess the public health risks of their presence in foods and propose measures to ensure the safety of customers. Effective control measures for food safety have been based on knowledge of the resistance of pathogenic microorganisms to the treatments used for preservation (e.g. acidification or reduced water activity) or decontamination (e.g. pasteurisation or sterilisation). Using this principle, food safety has been managed informally and successfully within the food industry for many years. Recently, formal risk assessment schemes, for example from Codex Alimentarius, have developed and placed the elements of decision-making on suitable control measures into a formal framework with clearly identifiable stages. The output of the four stages of a formal risk assessment (hazard identification, hazard characterisation, exposure assessment and risk characterisation) provides the basis for decisions on actions needed to control the identified hazard. There are many difficulties in ensuring that risk assessments are realistic and accessible to potential users, in many cases their value is limited by the data available. The study reported here on control of Salmonella in poultry products illustrates that it is possible to produce a comparative risk assessment based on published data. This study is not a full quantitative risk assessment, but provide useful pointers for a risk manager. Differences are discussed between the exposure assessment data needed to propose controls for infectious or toxigenic pathogens. For infectious pathogens, the presence of viable and infectious microorganisms is itself the hazard, but for toxigenic microorganisms, absence or destruction of viable cells at ingestion does not in itself ensure the absence of toxin. For toxin hazards, exposure assessment needs to consider previous conditions that may have led to toxin formation and persistence, rather than just the level of microbes at ingestion.     

A SXRF method for determining the relative concentration of trace elements in plasma protein affected by cisplatin

This article presents an analytical method for the determination of the relative concentrations of trace elements in plasma protein by gel chromatography combined with SXRF (synchrotron radiation X-ray fluorescence). The fraction of plasma protein of male Kunming mice (body weight 24.2±0.3 g), treated with a cisplatin ip injection at a dose of 10 mg/kg, was obtained by the separation of a Sephadex G-50 column (buffered with ammonium acetate, pH 5.7). The SXRF experiments were performed at the Beijing Electron Positron Collider synchrotron radiation facility. The elements (Pt, S, Ca, Fe, Ni, Cu, Zn, Se, Br, and Sr) in the fraction of the plasma proteins (>22 kDa) were assayed using highly sensitive SXRF. The relative concentrations of elements were calculated by a normalization of Compton scattering intensity around 22 keV, after the normalization for the collection time of the X-ray spectrum and the counting of the ion chamber, and subtracting the contribution of the polycarbonate film for the supporting sample. The determination could prove that the element Pt in plasma was bound with macromolecular protein. Cu and S were present in the fraction of the protein in mice treated with cisplatin increase, and their ratios of treated/control were 1.66±0.06 and 1.78±0.33, respectively; Zn decreased to a ratio of 0.78±0.09. Our results are in agreement with others that cisplatin exposure leads to a marked loss of kidney copper and a moderate rise in kidney zinc. However, this article primarily describes one of the analytical methods used; it does not emphasize the results of the effect of cisplatin on trace elements in plasma protein.     

A method for determining identity and relative purity of carmine, carminic acid and aminocarminic acid

Carmine is one of the few dyes currently certified by the Biological Stain Commission that is not assayed for dye content. Existing assay methods are complex and do not differentiate the three cochineal derivatives carmine, carminic acid and aminocarminic acid. The latter dye is relatively new to the food trade as an acid-stable red colorant and may eventually enter the biological stains market. The assay proposed here is a two-step procedure using quantitative spectrophotometric analysis at high pH (12.5-12.6) followed by a qualitative scan of a low pH (1.90-2.10) solution. Carmine is distinct at high pH, and the remaining dyes are easily distinguished at low pH. Four instances of mislabeling are documented from 18 commercial products, but the mislabeled dyes were not certified dyes. Samples from nearly all lots of carmine certified by the Biological Stain Commission from 1920 to 2004 proved to be carmine, but they varied widely in dye content. Batches from 1920 through the 1940s were significantly richer in dye content. Variability has been extreme since 2000, and most of the poorest lots have been submitted since 1990.     

A method for determining identity and relative purity of carmine,carminic acid and aminocarminic acid

Carmine is one of the few dyes currently certified by the Biological Stain Commission that is not assayed for dye content. Existing assay methods are complex and do not differentiate the three cochineal derivatives carmine, carminic acid and aminocarminic acid. The latter dye is relatively new to the food trade as an acid-stable red colorant and may eventually enter the biological stains market. The assay proposed here is a two-step procedure using quantitative spectrophotometric analysis at high pH (12.5–12.6) followed by a qualitative scan of a low pH (1.90–2.10) solution. Carmine is distinct at high pH, and the remaining dyes are easily distinguished at low pH. Four instances of mislabeling are documented from 18 commercial products, but the mislabeled dyes were not certified dyes. Samples from nearly all lots of carmine certified by the Biological Stain Commission from 1920 to 2004 proved to be carmine, but they varied widely in dye content. Batches from 1920 through the 1940s were significantly richer in dye content. Variability has been extreme since 2000, and most of the poorest lots have been submitted since 1990.     

A method for determining the K-uptake from subsoil by plants

Summary Rb was applied to the topsoil in order to trace the potassium which was taken up from the topsoil by plants. The resulting K/Rb ratio in plants increased when plants came into contact with the Rb free subsoil. This change in the K/Rb ratio enables the calculation of the K uptake from the subsoil. the average of the K uptake from the subsoil by spring wheat was 35% of the total uptake.