QMRA for Drinking Water: 2. The Effect of Pathogen Clustering in Single‐Hit Dose‐Response Models

Spatial and/or temporal clustering of pathogens will invalidate the commonly used assumption of Poisson‐distributed pathogen counts (doses) in quantitative microbial risk assessment. In this work, the theoretically predicted effect of spatial clustering in conventional “single‐hit” dose‐response models is investigated by employing the stuttering Poisson distribution, a very general family of count distributions that naturally models pathogen clustering and contains the Poisson and negative binomial distributions as special cases. The analysis is facilitated by formulating the dose‐response models in terms of probability generating functions. It is shown formally that the theoretical single‐hit risk obtained with a stuttering Poisson distribution is lower than that obtained with a Poisson distribution, assuming identical mean doses. A similar result holds for mixed Poisson distributions. Numerical examples indicate that the theoretical single‐hit risk is fairly insensitive to moderate clustering, though the effect tends to be more pronounced for low mean doses. Furthermore, using Jensen's inequality, an upper bound on risk is derived that tends to better approximate the exact theoretical single‐hit risk for highly overdispersed dose distributions. The bound holds with any dose distribution (characterized by its mean and zero inflation index) and any conditional dose‐response model that is concave in the dose variable. Its application is exemplified with published data from Norovirus feeding trials, for which some of the administered doses were prepared from an inoculum of aggregated viruses. The potential implications of clustering for dose‐response assessment as well as practical risk characterization are discussed.     

Construct and Criterion Validity of a Norwegian Instrument for Health Related Quality of Life Among Elderly Women Living at Home

Purpose of the study: The aim of the current study is to validate an instrument consisting of five items and first used in the Nord-Trondelag Health Survey (HUNT-5), as a measure of health related quality of life (QOL) in a population of elderly women living at home. Design and methods: A random sample of 307 women aged 75 years and over (mean 80.8 years, response rate 74.5%) and living at home were interviewed using the HUNT-5 instrument, the 20-question version of the General Health Questionnaire (GHQ-20) and the respondents’ records of their health status and functional ability. Results: No significant relationships were found between age and the sumscores of GHQ-20 and HUNT-5. Factor analysis indicated that HUNT-5 is primarily unidimensional. The Cronbach α for HUNT-5 was 0.79 and that for GHQ-20 was 0.87. The correlation between the HUNT-5 and the GHQ-20 sumscores was 0.75 (p < 0.001). There were significant correlations between some of the health and function items and the two QOL instruments (ranging from 0.14 to 0.68). Implications: This evaluation supports the psychometric validity of HUNT-5 for elderly women living at home. It is important to take into consideration the women’s own experience of their health and functional ability in planning therapy and in obtaining the best possible QOL for them.     

Messaging,music, and mailbags: How technical design and entertainment boost the performance of environmental organizations’ podcasts

The production and consumption of podcasts have grown exponentially since their introduction in 2004. As organizations increasingly use this social media tactic to reach their stakeholders, two theoretical frameworks – the theory of entertainment persuasion and the PodCred framework – can be used to create more meaningful messages for the podcasts’ audiences. Through a content analysis of 67 environmental podcasts, this study examined the extent to which environmental podcasts developed by organizations incorporate seven distinct communication strategies and design techniques. The study found that while inclusion of these strategies and techniques has statistical correlation to podcast popularity, organizations are only modestly incorporating them into their podcasts.     

QMRA for Drinking Water: 1. Revisiting the Mathematical Structure of Single‐Hit Dose‐Response Models

Dose‐response models are essential to quantitative microbial risk assessment (QMRA), providing a link between levels of human exposure to pathogens and the probability of negative health outcomes. In drinking water studies, the class of semi‐mechanistic models known as single‐hit models, such as the exponential and the exact beta‐Poisson, has seen widespread use. In this work, an attempt is made to carefully develop the general mathematical single‐hit framework while explicitly accounting for variation in (1) host susceptibility and (2) pathogen infectivity. This allows a precise interpretation of the so‐called single‐hit probability and precise identification of a set of statistical independence assumptions that are sufficient to arrive at single‐hit models. Further analysis of the model framework is facilitated by formulating the single‐hit models compactly using probability generating and moment generating functions. Among the more practically relevant conclusions drawn are: (1) for any dose distribution, variation in host susceptibility always reduces the single‐hit risk compared to a constant host susceptibility (assuming equal mean susceptibilities), (2) the model‐consistent representation of complete host immunity is formally demonstrated to be a simple scaling of the response, (3) the model‐consistent expression for the total risk from repeated exposures deviates (gives lower risk) from the conventional expression used in applications, and (4) a model‐consistent expression for the mean per‐exposure dose that produces the correct total risk from repeated exposures is developed.     

The promises of practice

Practice has become a topic of increasing empirical and conceptual concern within sociology and neighbouring fields. ‘Practice’ can refer to a location or it can refer to action. It is possible to be ‘in practice’, to ‘have a practice’ or to be ‘constituted by practice’. Practice can be a cause, an effect or an explanation. Within science and technology studies (STS), the practice orientation is simultaneously analytical – in the form of various practice theories – and empirical, in that research objects are often defined as ‘practices’. Focusing on a range of examples, especially ethnomethodological, this paper examines some implications and problems that follow when practice slides unnoticed between empirical and conceptual registers. Arguing that a reconsideration of practice thinking is important in order to retain its vigour, we outline a view of practice as a ‘factish’, at once conceptual and empirical, which facilitates analyses of practical ontologies and their transformations. This informs a final discussion of the politics and promises of practice.     

Comparison of approaches for estimating the probability of coastal flooding

Coastal flooding is typically caused by combinations of extreme water-levels and large waves. Two extreme value methods, one univariate and the other multivariate, have been used for estimating the probability of coastal flooding at an existing flood defence structure and for aiding the design of a new structure. The properties of these two methods are compared in terms of extrapolation, sophistication and use of information for a range of extremal dependence structures. We find that, when applied to the assessment of the safety offered by an existing Dutch dike, the multivariate approach provides the more useful and accurate design information and has the substantial benefits of consistency and reduced statistical analysis when applied to several sites along a Dutch coastline.     

Health, balance, and walking as correlates of climbing steps

The aim of this study was to investigate walking and health among woman age 75 yr or older, in the associations between the highest step up performed without support by an individual and balance, walking, and health among women age 75+. Records of the highest step, balance, walking, and health were made for 307 women age 75-93 yr living in the community. Eighty percent managed to climb steps higher than 20 cm. There was a statistically significant negative relationship between age and stair-climbing capacity. The highest steps registered were significantly and independently associated with a short time on the timed up-and-go test, long functional reach, low body weight, lack of perceived difficulty walking outdoors, low number of "missteps" when walking in a figure of 8, longer time in one-leg stance, ability to carry out tandem stance, no walking aids outdoors, and not being afraid of falling. These variables together explained 67% of the variance in the step-height score.     

“What Will My Friends Think?” Social Consequences for Danish Victims of Sexual Assaults in Peer Groups

Being exposed to sexual assaults has numerous psychological and social consequences, which may interfere with the adolescent’s still-ongoing development. This article focuses on social consequences for adolescents exposed to sexual assault by someone from their peer group.

Participants were 148 in number and 15–18 year olds (M = 16.34 years, 90.5% female) from Centre for Victims of Sexual Assault’s “Youth Programme.”

A mixed methods design combined extensive survey data collected from the 148 adolescents and five case stories. Almost half of the assaults (47.4%) were committed by someone from the victim’s social circle who was not a family member. Only 30.5% of these victims reported the assault to the police. Fear of social consequences was the main reason for not reporting. The majority of the participants described failure to thrive in school in the aftermath of the assault, for example, because the assailant attended the same school. Result furthermore showed how social relations can be complicated due to an assault and subsequent reactions, which can result in isolation for the victim and exclusion from their peer group.

Sexual assaults in peer groups have great impact on the victim’s well-being. Understanding and support from peers is of the utmost importance. Implications for practice are discussed.     

Retrospective accounts of first exposure to minoritized sexual and gender identities

Although there has been considerable research about attitudes towards LGBTQ+ people, there has been little research into how people first come to be aware of minoritized sexual and gender minority (SGM) identities. This study sought to address this gap. A sample of sexual minority (n = 150) and heterosexual (n = 802) young adults (N = 952; M_age = 18.88 years, SD = 1.75; 949 were cisgender, three were transgender), primarily recruited from a large southern university, were asked retrospectively to recount their first exposure to or awareness of SGM identities. Responses between SGM and heterosexual participants were compared through a variety of analytical approaches, including analyzing themes about the source from which participants first recalled encountering these identities, and whether understanding about these identities came through a personal connection to someone with these identities. SGM participants reported encountering minoritized sexual identities a year earlier than did heterosexual participants, with both groups encountering these concepts in middle childhood, on average. SGM participants were more likely than heterosexual participants to report learning about minoritized gender identities from someone with a minoritized gender identity, while heterosexual participants more often reported learning about these identities from media or celebrities. Heterosexual (vs. SGM) participants were also more likely to imply that minoritized gender identities were adopted to be popular, rather than being authentic identities in themselves. Framed by developmental intergroup theory (DIT), we discuss implications of these findings, especially potential interrelationships with the development of prejudiced attitudes about SGM identities.