Pauline Slottje

Expert elicitation on ultrafine particles: likelihood of health effects and causal pathways

BackgroundExposure to fine ambient particulate matter (PM) has consistently been associated with increased morbidity and mortality. The relationship between exposure to ultrafine particles (UFP) and health effects is less firmly established. If UFP cause health effects independently from coarser fractions, this could affect health impact assessment of air pollution, which would possibly lead to alternative policy options to be considered to reduce the disease burden of PM. Therefore, we organized an expert elicitation workshop to assess the evidence for a causal relationship between exposure to UFP and health endpoints.MethodsAn expert elicitation on the health effects of ambient ultrafine particle exposure was carried out, focusing on: 1) the likelihood of causal relationships with key health endpoints, and 2) the likelihood of potential causal pathways for cardiac events. Based on a systematic peer-nomination procedure, fourteen European experts (epidemiologists, toxicologists and clinicians) were selected, of whom twelve attended. They were provided with a briefing book containing key literature. After a group discussion, individual expert judgments in the form of ratings of the likelihood of causal relationships and pathways were obtained using a confidence scheme adapted from the one used by the Intergovernmental Panel on Climate Change.ResultsThe likelihood of an independent causal relationship between increased short-term UFP exposure and increased all-cause mortality, hospital admissions for cardiovascular and respiratory diseases, aggravation of asthma symptoms and lung function decrements was rated medium to high by most experts. The likelihood for long-term UFP exposure to be causally related to all cause mortality, cardiovascular and respiratory morbidity and lung cancer was rated slightly lower, mostly medium. The experts rated the likelihood of each of the six identified possible causal pathways separately. Out of these six, the highest likelihood was rated for the pathway involving respiratory inflammation and subsequent thrombotic effects.ConclusionThe overall medium to high likelihood rating of causality of health effects of UFP exposure and the high likelihood rating of at least one of the proposed causal mechanisms explaining associations between UFP and cardiac events, stresses the importance of considering UFP in future health impact assessments of (transport-related) air pollution, and the need for further research on UFP exposure and health effects.

The use of expert elicitation in environmental health impact assessment: a seven step procedure

BackgroundEnvironmental health impact assessments often have to deal with substantial uncertainties. Typically, the knowledge-base is limited with incomplete, or inconsistent evidence and missing or ambiguous data. Consulting experts can help to identify and address uncertainties.MethodsFormal expert elicitation is a structured approach to systematically consult experts on uncertain issues. It is most often used to quantify ranges for poorly known parameters, but may also be useful to further develop qualitative issues such as definitions, assumptions or conceptual (causal) models. A thorough preparation and systematic design and execution of an expert elicitation process may increase the validity of its outcomes and transparency and trustworthiness of its conclusions. Various expert elicitation protocols and methods exist. However, these are often not universally applicable, and need customization to suite the needs of a specific study. In this paper, we set out to develop a widely applicable method for the use of expert elicitation in environmental health impact assessment.ResultsWe present a practical yet flexible seven step procedure towards organising expert elicitation in the context of environmental health impact assessment, based on existing protocols. We describe how customization for specific applications is always necessary. In particular, three issues affect the choice of methods for a particular application: the types of uncertainties considered, the intended use of the elicited information, and the available resources. We outline how these three considerations guide choices regarding the design and execution of expert elicitation. We present signposts to sources where the issues are discussed in more depth to give the newcomer the insights needed to make the protocol work. The seven step procedure is illustrated using examples from earlier published elicitations in the field of environmental health research.ConclusionsWe conclude that, despite some known criticism on its validity, formal expert elicitation can support environmental health research in various ways. Its main purpose is to provide a temporary summary of the limited available knowledge, which can serve as a provisional basis for policy until further research has been carried out.

Concentration Response Functions for Ultrafine Particles and All-Cause Mortality and Hospital Admissions: Results of a European Expert Panel Elicitation

Toxicological studies have provided evidence of the toxicity of ultrafine particles (UFP), but epidemiological evidence for health effects of ultrafines is limited. No quantitative summary currently exists of concentration-response functions for ultrafine particles that can be used in health impact assessment. The goal was to specify concentration-response functions for ultrafine particles in urban air including their uncertainty through an expert panel elicitation. Eleven European experts from the disciplines of epidemiology, toxicology, and clinical medicine selected using a systematic peer-nomination procedure participated. Using individual ratings supplemented with group discussion, probability distributions of effect estimates were obtained for all-cause mortality and cardiovascular and respiratory hospital admissions. Experts judged the small database of epidemiological studies supplemented with experimental studies sufficient to quantify effects of UFP on all-cause mortality and to a lesser extent hospital admissions. Substantial differences in the estimated UFP health effect and its uncertainty were found between experts. The lack of studies on long-term exposure to UFP was rated as the most important source of uncertainty. Effects on hospital admissions were considered more uncertain. This expert elicitation provides the first quantitative evaluation of estimates of concentration response functions between urban air ultrafine particles and all-cause mortality and hospital admissions.

Long term health complaints following the Amsterdam Air Disaster in police officers and fire‐fighters

Background: On 4 October 1992, a cargo aircraft crashed into apartment buildings in Amsterdam, the Netherlands. Fire-fighters and police officers assisted with the rescue work. Objectives: To examine the long term health complaints in rescue workers exposed to a disaster. Methods: A historical cohort study was performed among police officers (n = 834) and fire-fighters (n = 334) who performed at least one disaster related task and reference groups of their non-exposed colleagues (n = 634 and n = 194, respectively). The main outcome measures included digestive, cardiovascular, musculoskeletal, nervous system, airway, skin, post-traumatic stress, fatigue, and general mental health complaints; haematological and biochemical laboratory values; and urinalysis outcomes. Results: Police officers and fire-fighters who were professionally exposed to a disaster reported more physical and mental health complaints, compared to the reference groups. No clinically relevant statistically significant differences in laboratory outcomes were found. Conclusions: This study is the first to examine long term health complaints in a large sample of rescue workers exposed to a disaster in comparison to reference groups of non-exposed colleagues. Findings show that even in the long term, and in the absence of laboratory abnormalities, rescue workers report more health complaints.

Associations of cortisol with posttraumatic stress symptoms and negative life events: a study of police officers and firefighters

Given the inconsistent associations of cortisol with posttraumatic stress disorder (PTSD), analysis of basal functioning of the hypothalamic-pituitary-adrenal (HPA) axis in subjects frequently exposed to trauma and critical incidents with a range of PTSD symptomatology, may be valuable. In an epidemiological sample of 1880 police officers and firefighters, associations of salivary cortisol with PTSD, negative life events (NLE) and exposure to a major air disaster more than 8 years earlier, was explored. Probable PTSD was unrelated to cortisol level while past (>8 years earlier) and more recently experienced NLE were associated with lower cortisol levels even after adjustment for confounders. Disaster exposure interacted significantly with PTSD symptoms on cortisol level. In the disaster-exposed subgroup, PTSD symptomclusters of intrusion and hyperarousal (in particular sleep disturbances), were associated with lower and higher cortisol levels, respectively. A final model using backward elimination strategy, retained time of saliva sampling, smoking, gender, and NLE>8 years earlier in the total sample, and additionally symptomclusters of intrusion and hyperarousal in the disaster-exposed subgroup. The final model explained 10% of the variance in cortisol. The findings are discussed in relation to literature on posttraumatic stress and basal functioning of the HPA-axis.

Psychological distress of rescue workers eight and one-half years after professional involvement in the Amsterdam air disaster

This study examined specific and general psychological distress 8.5 years following the 1992 cargo aircraft crash in Amsterdam. Participants included 334 occupationally exposed fire fighters and 834 occupationally exposed police officers compared with reference groups of 194 fire fighters and 634 police officers who were exposed to duty-related stressors other than the disaster. On the standardized instruments of psychological distress, exposed fire fighters reported more somatic complaints and fatigue, while exposed police officers reported higher psychological distress on all aspects. The degree and type of exposure at the disaster site and other background factors were associated with several outcomes of psychological distress levels of exposed rescue workers. The disasters’ aftermath of rumors about potential health consequences due to toxic exposure likely contributed to the long-lasting psychological distress of some of the rescue workers as well.

Effects of magnetic stray fields from a 7 tesla MRI scanner on neurocognition: a double-blind randomised crossover study.

Objective This study characterises neurocognitive domains that are affected by movement-induced time-varying magnetic fields (TVMF) within a static magnetic stray field (SMF) of a 7 Tesla (T) MRI scanner. Methods Using a double-blind randomised crossover design, 31 healthy volunteers were tested in a sham (0 T), low (0.5 T) and high (1.0 T) SMF exposure condition. Standardised head movements were made before every neurocognitive task to induce TVMF. Results Of the six tested neurocognitive domains, we demonstrated that attention and concentration were negatively affected when exposed to TVMF within an SMF (varying from 5.0% to 21.1% per Tesla exposure, p<0.05), particular in situations were high working memory performance was required. In addition, visuospatial orientation was affected after exposure (46.7% per Tesla exposure, p=0.05). Conclusion Neurocognitive functioning is modulated when exposed to movement-induced TVMF within an SMF of a 7 T MRI scanner. Domains that were affected include attention/concentration and visuospatial orientation. Further studies are needed to better understand the mechanisms and possible practical safety and health implications of these acute neurocognitive effects.

Epidemiological study air disaster in Amsterdam (ESADA): study design

BackgroundIn 1992, a cargo aircraft crashed into apartment buildings in Amsterdam, killing 43 victims and destroying 266 apartments. In the aftermath there were speculations about the cause of the crash, potential exposures to hazardous materials due to the disaster and the health consequences. Starting in 2000, the Epidemiological Study Air Disaster in Amsterdam (ESADA) aimed to assess the long-term health effects of occupational exposure to this disaster on professional assistance workers.Methods/DesignEpidemiological study among all the exposed professional fire-fighters and police officers who performed disaster-related task(s), and hangar workers who sorted the wreckage of the aircraft, as well as reference groups of their non-exposed colleagues who did not perform any disaster-related tasks. The study took place, on average, 8.5 years after the disaster. Questionnaires were used to assess details on occupational exposure to the disaster. Health measures comprised laboratory assessments in urine, blood and saliva, as well as self-reported current health measures, including health-related quality of life, and various physical and psychological symptoms.DiscussionIn this paper we describe and discuss the design of the ESADA. The ESADA will provide additional scientific knowledge on the long-term health effects of technological disasters on professional workers.

Dimensionality of the posttraumatic stress response among police officers and fire fighters: An evaluation of two self-report scales

Confirmatory factor analyses were done to assess the dimensionality of the stress response in a sample of police officers and fire fighters (n = 1,168) involved in the 1992 air disaster in Amsterdam. The confirmatory factor analyses were applied to the responses on two psychometrically different instruments, i.e., the Self-Rating Inventory for Posttraumatic Stress Disorder (SRIP) and the Impact of Event Scale (IES). The previously found distinction between (active) avoidance and numbing in samples highly affected by posttraumatic stress disorder appears to be applicable to the stress response of a less affected sample. For the SRIP, a five-factor structure (i.e., intrusion, avoidance, hyperarousal, emotional numbing and sleep disturbance) appeared to fit slightly better than the four-factor structures from previous findings. For the IES, our results replicated findings of a four-dimensional structure (i.e., intrusion, avoidance, numbing and sleep disturbance) underlying the posttraumatic stress response. The factors of the best-fitting structure of both instruments proved reliable. Due to the psychometric properties of the two instruments, the relationship between similar factors in both instruments was only low to moderate. Compared with the IES, factors of the SRIP were, however, less discriminative from other symptoms of psychopathology. Replication in different traumatized or community samples is recommended.

MRI-related static magnetic stray fields and postural body sway: a double-blind randomized crossover study.

We assessed postural body sway performance after exposure to movement induced time‐varying magnetic fields in the static magnetic stray field in front of a 7 Tesla (T) magnetic resonance imaging scanner. Using a double blind randomized crossover design, 30 healthy volunteers performed two balance tasks (i.e., standing with eyes closed and feet in parallel and then in tandem position) after standardized head movements in a sham, low exposure (on average 0.24 T static magnetic stray field and 0.49 T·s−1 time‐varying magnetic field) and high exposure condition (0.37 T and 0.70 T·s−1). Personal exposure to static magnetic stray fields and time‐varying magnetic fields was measured with a personal dosimeter. Postural body sway was expressed in sway path, area, and velocity. Mixed‐effects model regression analysis showed that postural body sway in the parallel task was negatively affected (P < 0.05) by exposure on all three measures. The tandem task revealed the same trend, but did not reach statistical significance. Further studies are needed to investigate the possibility of independent or synergetic effects of static magnetic stray field and time‐varying magnetic field exposure. In addition, practical safety implications of these findings, e.g., for surgeons and others working near magnetic resonance imaging scanners need to be investigated. Magn Reson Med, 2013.