A test of the Australian Weed Risk Assessment system in China

The Australian Weed Risk Assessment system (AWRA) is an effective pre-border weed-screening tool that has played an active role in preventing the introduction of alien weeds into Australia and has been utilized in several other countries worldwide. Here, we selected 131 species of naturalized exotic plants (including 76 species of given non-weeds and 55 species of given weeds) to evaluate the AWRA in China for the first time. The AWRA performed better for discriminating major weeds than non-weeds and minor weeds, as it correctly rejected 84% of major weeds and did not wrongly accept a major weed. Among non-weeds, 76% were correctly classified with the final outcome of “accept” and 7.9% were wrongly rejected by the AWRA. This system correctly rejected 56% of minor weeds but accepted only 2.8% of minor weeds. The remaining 23% of all alien plants tested were classified as “evaluate further” by the AWRA. The area under the ROC curve (AUC) was 0.944, suggesting that the AWRA would be highly efficient at discriminating alien plants in China. In addition, we compared the scores of seven attributes of the AWRA between prior plant categories and analyzed their correlation with weed status. The average score for each attribute differed significantly between the two prior categories (weed and non-weed), but the average scores of the attribute “undesirable traits” did not significantly differ between any two of the three categories (non-weeds, minor weeds, and major weeds). There was a significant positive correlation between the scores of each attribute of the AWRA and weed status. The correlation coefficient for “dispersal mechanisms” and weed status was the highest and that for “undesirable traits” was the lowest. We believe that the AWRA can serve as an important weed-screening tool for plant introduction management in China.     

Ecological Risk Assessment of Tebuthiuron Following Application on Tropical Australian Wetlands

The present study assessed the ecological risks of the herbicide tebuthiuron to freshwater fauna and flora of northern Australia's tropical wetlands. Effects characterization utilized acute and chronic toxicity data of tebuthiuron to local freshwater species (three animals and two plants) as well as toxicity data derived from northern hemisphere species. Species sensitivity distributions (SSDs) for four effects scenarios—plant chronic toxicity (NOEC data), plant chronic toxicity (EC/IC₅₀ data), invertebrate and vertebrate chronic toxicity (NOEC data), and vertebrate acute toxicity (LC₅₀ data)—were used to characterize effects and calculate 10, 5, and 1% hazardous concentrations (HCs). Tebuthiuron concentrations affecting 5% of species (i.e., HC₅s) for the earlier scenarios were 0.013, 0.093, 9.0, and 97 mg L^?1, respectively. Exposure characterization involved the use of historical field monitoring data of tebuthiuron concentrations following application of tebuthiuron to a large infestation of the wetland weed Mimosa pigra (Mimosa). Tebuthiuron concentrations in surface water ranged from below detection to 2.05 mg L^?1 and were still measurable up to 10 months following application. A breakpoint regression model was fitted to the field monitoring data, providing a time-dependent estimate of exposure to tebuthiuron. Risk characterization involved the comparison of the SSDs and associated HCs for each of the effects scenarios, with the time-dependent model of tebuthiuron exposure. Modeled tebuthiuron concentrations over the first 12 days post-application were in excess of concentrations required to cause major (i.e., 50% reductions in population numbers) effects to over 85% of freshwater plant species (based on data for phytoplankton and floating macrophytes). Beyond this period and up to 300 d post-application, 10–20% of species were still predicted to be affected. To quantify the probability of prolonged effects, the plant SSDs were compared to a cumulative probability distribution of tebuthiuron measured from 70 d to 293 d post-application. The probability of at least 5% of freshwater plant species experiencing chronic effects due to tebuthiruon at ≥70 d post-application was 58% based on NOEC data and 8% based on EC/IC₅₀ data. Overlap of the 95% confidence limits of the exposure distribution and plant SSDs indicated substantial uncertainty in the risk estimates. Risks of effects to freshwater invertebrates and vertebrates were generally < 1%. It was concluded that tebuthiuron appears to represent a significant and prolonged risk to native freshwater plant species, particularly phytoplankton and floating macrophytes, whereas the risks to freshwater invertebrates and vertebrates appear low. However, from a management perspective, the risks of tebuthiuron (and other herbicides) must be weighed against the known, serious environmental and economic impacts of the target weed, Mimosa. Overall, the outcomes of the risk assessment support the various management options that have been implemented with regard to the use of tebuthiuron to control Mimosa.     

Risk assessment for invasiveness differs for aquatic and terrestrial plant species

Predictive tools for preventing introduction of new species with high probability of becoming invasive in the U.S. must effectively distinguish non-invasive from invasive species. The Australian Weed Risk Assessment system (WRA) has been demonstrated to meet this requirement for terrestrial vascular plants. However, this system weights aquatic plants heavily toward the conclusion of invasiveness. We evaluated the accuracy of the WRA for 149 non-native aquatic species in the U.S., of which 33 are major invaders, 32 are minor invaders and 84 are non-invaders. The WRA predicted that all of the major invaders would be invasive, but also predicted that 83% of the non-invaders would be invasive. Only 1% of the non-invaders were correctly identified and 16% needed further evaluation. The resulting overall accuracy was 33%, dominated by scores for invaders. While the overall accuracy increased to 57% when the points assigned to aquatic life forms were removed, 57% of the non-invaders required further evaluation rather than were identified as having low probability of naturalizing. Discrimination between non-invaders and invaders would require an increase in the threshold score from the standard of 6 for this system to 19. That higher threshold resulted in accurate identification of 89% of the non-invaders and over 75% of the major invaders. Either further testing for definition of the optimal threshold or a separate screening system will be necessary for accurately predicting which freshwater aquatic plants are high risks for becoming invasive.     

Machinery Risk Assessment for Risk Reduction

New avenues are reviewed and discussed for preventing industrial machine-related injury by means of realistic risk evaluation and reduction processes at the design and application stages of machinery development and use. U.S. guidelines and European standards on machinery risk assessment procedures are described. Applications of risk assessment for machine-related injury risk management and teaching machine-risk control are discussed.     

Evaluation of the Australian weed risk assessment system for the prediction of plant invasiveness in Canada

The Australian Weed Risk Assessment system has been tested in a number of countries and geographical areas since its introduction in 1997, and is widely considered to be an accurate method of predicting the risk of invasiveness of new plant introductions. We evaluated the system against 152 plant species with at least a 50-year introduction history in Canada, including major and minor weeds and species which have not naturalized. Four questions that referred explicitly to Australian conditions were replaced with appropriate equivalent questions for Canada. The weediness of each species was independently rated by a panel of Canadian agricultural, botanical, and conservation experts. Using the standard cut-off scores, the system correctly rejected all major and 86% of minor weeds. However, it also incorrectly rejected 44% of non-weedy species. The diagnostic power of the system, as measured by the receiver operating characteristic curve, was similar to but somewhat lower than that found in other regions where the system has been evaluated. Answers to 23 of the 49 questions were not significantly associated with experts’ weediness ratings, indicating that a simplified system could give equally reliable results for Canada. Experts’ ratings were strongly related to cold-hardiness, suggesting that the system could be improved by making better use of data on climatic tolerances. We suggest that performance would also be improved by combining likelihood- and consequence-related scores in a multiplicative rather than additive way.     

Health Risk Assessment and Vapor Intrusion: A Review and Australian Perspective

Soil contamination by volatile hydrocarbons is of public health importance due to vapor intrusion and indoor inhalation exposures. These are assessed using measurement or predictive modeling and need to consider the key areas of subsurface partitioning and transport, dwelling ventilation, and receptor inhalation dosimetry. While subsurface partitioning and transport have been subject to intensive international investigation, limited consideration has been given to the latter. Building ventilation research has developed multi-zone airflow and contaminant dispersal models including AccuRate, an Australian model that examines natural ventilation modeling, roof and sub-floor ventilation, and identifies the importance of geometry and thermal factors on ventilation (the most sensitive variable) and indoor pollutant concentrations. Inhalation dosimetry has received recent attention due to concerns over child inhalation susceptibility and dose metrics. Research using coupled computational fluid dynamics (CFD) and physiologically based pharmaco-kinetic (PBPK) models has reported variance from previous animal models’ extrapolation while CFD modeling of transient lung vapor absorption suggests the significance of transient versus steady-state evaluation of volatiles absorption into tissue and blood. The transient nature of sub-surface fate and transport, ventilation, and inhalation uptake thus warrants integrated exploration and application in order to realize improvements in vapor intrusion assessments. These perspectives and Australian modeling initiatives are presented in this article.     

Testing marker-based estimates of heritability in the wild

Marker-based estimates of heritability are an attractive alternative to pedigree-based methods for estimating quantitative genetic parameters in field studies where it is difficult or impossible to determine relationships and pedigrees. Here I test the ability of the marker-based method to estimate heritability of a suite of traits in a wild population of bighorn sheep (Ovis canadensis) using marker data from 32 microsatellite loci. I compared marker-based estimates with estimates obtained using a pedigree and the animal model. Marker-based estimates of heritability were imprecise and downwardly biased. The high degree of uncertainty in marker-based estimates suggests that the method may be sufficient to detect the presence of genetic variance for highly heritable traits, but not sufficiently reliable to estimate genetic parameters.     

Approaches for Integrated Risk Assessment

Recognizing the need to enhance the effectiveness and efficiency of risk assessments globally, the World Health Organization's International Programme on Chemical Safety, the U.S. Environmental Protection Agency, the European Commission, and the Organization for Economic Cooperation and Development developed a collaborative partnership to foster integration of assessment approaches used to evaluate human health and ecological risks. The objectives of this effort included: improving understanding of the benefits of integration, identifying obstacles to the integration process, and engaging key agencies, organizations, and scientific societies to promote integration. A framework with supporting documentation was developed to describe an approach for integration. Four case studies were constructed to illustrate how integrated risk assessments might be conducted for chemical and nonchemical stressors. The concepts and approaches developed in the project were evaluated in an international workshop. The goal of this effort was international acceptance of guidance for integrated risk assessment.     

Risk Factors for Acute Respiratory Infection in the Australian Community

Objectives

The objective of this study was to identify the risk factors for ARI in the Australian community.

Methods

We used a national survey of 7578 randomly selected respondents in 2008–2009 to identify the risk factors of ARI. A case was defined as a person experiencing cold or flu with one or more symptoms of: fever, chills, sore throat, runny nose, or cough in the previous four weeks.

Results

There were 19.8% (1505/7578) of respondents who reported ARI in the four weeks prior to the survey. Age was an independent risk factor for ARI, with the risk of acquiring ARI decreasing as age increased. Respondents reporting asthma (OR 1.4, 95%CI: 1.2–1.7) or having someone in their house attending childcare (OR 1.6, 95%CI: 1.2–2.1) were more likely to report ARI.

Conclusions

It is important to identify ways of interrupting transmission of ARI amongst children. Improving identification of risk factors will enable targeted interventions for this exceedingly common syndrome.     

Sediment Toxicity Testing for Prospective Risk Assessment—A New Framework and How to Establish It

There is a recognized need to design a new framework for sediment toxicity testing that meets current scientific standards and regulatory requirements, such as reliable assessment of toxicity, which prevents any harmful effects on biodiversity, a strong capability to predict population- and community-level effects, and applicability of the results to decision-making. We propose a new framework for prospective sediment toxicity testing, and suggest solutions to the key methodological challenges that hinder establishment of this framework (comparison of sensitivities, design of test batteries, consideration of different exposure routes, extrapolations to population and community levels, use of test results for decision-making). The proposed framework consists of the following three units: test-battery system, higher-tier testing systems and additional ecological modeling, and a decision support system. The key methodologies proposed to establish this framework are compound-tailored test-battery use approach, relative sensitivity distribution analysis, toxicity tests that combine bacteria and arthropods, micro- and mesocosms studies, population and community models, and model-driven decision support systems. The proposed framework, as well as the key methods mentioned above, has the potential to improve not only prospective toxicity testing for sediments, but also ecological risk assessment in general.     

Human Risk Assessment for Nonylphenol

This article presents a risk assessment for human exposure to nonylphenol (NP). We critically reviewed and assessed all relevant full-text publications based on a variety of data quality attributes. Two categories of data, environmental monitoring and biomonitoring from exposed individuals, were used to estimate human exposure to NP. Environmental monitoring data included the measurement of NP in food, water, air, and dust. From these data and estimates of human intake rates for the sources, exposures were estimated from each source and source-specific Margins of Exposure (MOEs) calculated. However, the nature of the populations studied prevented the calculation of aggregate exposure calculations from these data. Rather, the most reliable estimates of aggregate exposure to NP were those derived from biomonitoring studies in exposed individuals. Using the daily absorbed dose estimates for NP, MOEs were calculated for these populations. The MOEs were based on the use of a No-Observed-Adverse-Effect-Level (NOAEL) for sensitive toxicological endpoints of interest, that is, systemic and reproductive toxicity from continuous-feeding more than 3.5 generations (13 mg/kg/day). The MOEs were all greater than 1000 (ranging from 2863 to 8.4 × 10⁷), clearly indicating reasonable certainty of no harm for source-specific and aggregate (based on biomonitoring) exposures to NP.     

Dealing with Uncertainty in Risk Assessment

This paper is a commentary on Hattis’ three laws of risk assessment. The first law, that “application of standard statistical techniques to a single data set will nearly always reveal only a trivial proportion of the overall uncertainty in the parameter value” is illustrated both by examining the relevance of animal models to man and by a retrospective view of exposure conditions whose importance has only recently been recognized to be important. The second law, that “any estimate of the uncertainty of a parameter value will always itself be more uncertain than the estimate of the parameter value,” is examined in terms of a model addressing multiple levels of uncertainty, e.g., the “uncertainty in the uncertainty”. A argument is made that the number of terms needed for convergence of this uncertainty hierarchy depends on how far from the central tendency of the risk distribution one goes. The further out the “tail” of the distribution, the more terms in the uncertainty hierarchy are needed for convergence. The third law, that “nearly all parameter distribu tions look lognormal, as long as you don't look too closely,” is illustrated with a number of examples. Several reasons are put forward as to why risk variables appear so frequently to be lognormal. Recognition of the lognormal character of variable distributions can provide insight into the proper form for the associated uncertainty distributions.     

Survival estimates for the Australian sea lion: Negative correlation of sea surface temperature with cohort survival to weaning

The Australian sea lion (Neophoca cinerea) population at Seal Bay Conservation Park, South Australia, is estimated to be declining at a rate of 1.14% per breeding season. To better understand the potential causes of this decline, survival rates were examined to 14 yr of age for eight cohorts marked as pups (aged 0.17 yr) between 1991 and 2002. Apparent yearly survival rates (Φ) varied by cohort for pups from marking to weaning at 1.5 yr (Φ= 0.30–0.67). Postweaning juvenile survival (1.5–3 yr) was 0.89 and survival from 3 to 14 yr was constant (Φ female:male = 0.96:0.89). Φ of pup cohorts was negatively correlated to local sea surface temperature where the sea lions forage (SST) and was especially low for cohort 7 in 2000 (0.30). It is possible that periods of unusually warm oceanographic conditions may be limiting primary production and inhibiting maternal provisioning to pups. Pup survival to weaning is relatively low compared to other otariid species, is likely to limit recruitment, and may be contributing to the decline in pup abundance observed in the colony.     

Absolute Risk and Loss-of-Lifetime Estimates for Quantitative Risk Assessment

Quantitative risk assessments in public health settings intend to describe the hazard of a specific exposure in a given population on the basis of epidemiological and/or experimental results. Two different risk quantities, the absolute lifetime excess risk and the loss-of-lifetime, which differ in their definition of hazard, are discussed and compared. For both measures estimation procedures are derived and the relationship between the various estimates which are currently in use are investigated. It is shown that the two most common estimators can be written as special cases of a more general concept. This leads to conclusions about the assumptions on which different estimation procedures are implicitly based. For all discussed estimators variance estimates are derived. The analytical results for both risk parameters will be elucidated by an example on lung cancer risk due to residential radon in Germany.     

Korean Risk Assessment Model for Breast Cancer Risk Prediction

Purpose

We evaluated the performance of the Gail model for a Korean population and developed a Korean breast cancer risk assessment tool (KoBCRAT) based upon equations developed for the Gail model for predicting breast cancer risk.

Methods

Using 3,789 sets of cases and controls, risk factors for breast cancer among Koreans were identified. Individual probabilities were projected using Gail''s equations and Korean hazard data. We compared the 5-year and lifetime risk produced using the modified Gail model which applied Korean incidence and mortality data and the parameter estimators from the original Gail model with those produced using the KoBCRAT. We validated the KoBCRAT based on the expected/observed breast cancer incidence and area under the curve (AUC) using two Korean cohorts: the Korean Multicenter Cancer Cohort (KMCC) and National Cancer Center (NCC) cohort.

Results

The major risk factors under the age of 50 were family history, age at menarche, age at first full-term pregnancy, menopausal status, breastfeeding duration, oral contraceptive usage, and exercise, while those at and over the age of 50 were family history, age at menarche, age at menopause, pregnancy experience, body mass index, oral contraceptive usage, and exercise. The modified Gail model produced lower 5-year risk for the cases than for the controls (p = 0.017), while the KoBCRAT produced higher 5-year and lifetime risk for the cases than for the controls (p<0.001 and <0.001, respectively). The observed incidence of breast cancer in the two cohorts was similar to the expected incidence from the KoBCRAT (KMCC, p = 0.880; NCC, p = 0.878). The AUC using the KoBCRAT was 0.61 for the KMCC and 0.89 for the NCC cohort.

Conclusions

Our findings suggest that the KoBCRAT is a better tool for predicting the risk of breast cancer in Korean women, especially urban women.     

Ethical Issues in the Use of Data from Testing of Human Subjects to Support Risk Assessment

The public understands and supports the ethical use of human subjects in medical research, recognizing the unique role for this type of study in the development of new drugs and therapeutic strategies for treatment of disease. The use of data from human subjects can also be of value in understanding the circumstances under which individuals exposed to chemicals in the food supply, in the workplace, or in the environment might experience toxicity, i.e., in support of risk assessment. However, questions have been raised as to whether this latter type of research is ethical, or can be performed in an ethical manner. Under what circumstances is it acceptable to intentionally expose human subjects to potentially toxic agents? This is an extremely important issue for the risk assessment community to address, because it affects in a fundamental way the types of information that will be available to conduct human health risk assessments. Four papers in this issue offer viewpoints on the value of human data, the circumstances under which human subjects might be exposed to toxic chemicals for research purposes, the ethical problems associated with this research, and the role of human vs. animal data in the development of toxicity values for human health risk assessment     

Framework for Human Health Risk Assessment

The views expressed in this paper are those of the authors and do not necessarily reflect the views or policies of the USEPA. The U.S. Government has the right to retain a nonexclusive royalty-free license in and to any copyright covering this article. The U.S. Environmental Protection Agency has recognized the need to develop a framework for human health risk assessment that puts a perspective on the approaches in practice throughout the Agency. In response, the USEPA's Risk Assessment Forum has begun the process of developing a framework for human health risk assessment. This paper provides some additional background to the previous review of the framework efforts and notes the Agency's extramural efforts to begin the process of integrating and harmonizing risk assessment approaches for all human health endpoints.