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1.  Simulation enhanced distributed lag models for mortality displacement 
SpringerPlus  2016;5(1):1951.
Distributed lag models (DLM) are attractive methods for dealing with mortality displacement, however their estimates can have substantial bias when the data is generated by a multi-state model. In particular DLMs are not valid for mortality displacement. Alternative methods are scarce and lack feasibility and validation. We investigate the breakdown of DLM in three state models by means of simulation and propose simulation enhanced distributed lag models (SEDLM) to overcome the defects. The new method provides simultaneous estimates of the net effect (entry) and the displacement effect (exit). These have improved performance over the singular estimate from a regular DLM. SEDLM entry estimates have negligible bias and their variance is reduced. The exit estimates are unbiased and their variance is one order of magnitude lower with respect to the entry estimates. Applying SEDLM to the original Chicago data, the 95% highest posterior density intervals for both entry and exit contain 0, providing neither evidence for a ‘displacement effect’ nor for a ‘net effect’.
Electronic supplementary material
The online version of this article (doi:10.1186/s40064-016-3566-6) contains supplementary material, which is available to authorized users.
PMCID: PMC5104706  PMID: 27933234
Air pollution; Distributed lag model; Harvesting; Mortality displacement; Simulation study; Time series
2.  Human biomonitoring of heavy metals in the vicinity of non-ferrous metal plants in Ath, Belgium 
A previous study revealed an environmental contamination by heavy metals in the vicinity of two non-ferrous metal plants in Ath, Belgium. The purpose of the current cross-sectional study was to estimate exposure of the population to heavy metals in the vicinity of the plants, in comparison with population living further away.
We did a random sampling in the general population of Ath in two areas: a central area, including the plants, and a peripheral area, presumably less exposed. We quantified cadmium, lead, nickel, chromium and cobalt in blood and/or urine of children and adults in three age groups: (i) children aged 2.5 to 6 years (n = 98), (ii) children aged 7 to 11 years (n = 74), and (iii) adults aged 40 to 60 years (n = 106). We also studied subclinical health effects by quantifying retinol-binding protein and microalbuminuria, and by means of a Strengths and Difficulties Questionnaire.
We obtained a participation rate of 24 %. Blood lead levels were significantly higher in young children living in the central area (18.2 μg/l ; 95 % CI: 15.9–20.9) compared to the peripheral area (14.8 μg/l ; 95 % CI: 12.6–17.4). We observed no other significant mean difference in metal concentrations between the two areas. In the whole population, blood lead levels were higher in men (31.7 μg/l ; 95 % CI: 27.9–36.1) than in women (21.4 μg/l ; 95 % CI: 18.1–25.3). Urine cadmium levels were 0.06 μg/g creatinine (95 % CI: 0.05–0.07), 0.21 μg/g creatinine (95 % CI: 0.17–0.27), and 0.25 μg/g creatinine (95 % CI: 0.20–0.30) for children, men, and women, respectively.
Despite higher blood lead levels in young children living close to the plants, observed metal concentrations remain in the range found in other similar biomonitoring studies in the general population and are below the levels of concern for public health.
PMCID: PMC5047349  PMID: 27729976
Human biomonitoring; Heavy metals; Lead; Cadmium; Biomarkers; Retinol-binding protein; Albumin
3.  Short-Term Effect of Pollen and Spore Exposure on Allergy Morbidity in the Brussels-Capital Region 
Ecohealth  2016;13(2):303-315.
Belgium is among the European countries that are the most affected by allergic rhinitis. Pollen grains and fungal spores represent important triggers of symptoms. However, few studies have investigated their real link with disease morbidity over several years. Based on aeroallergen counts and health insurance datasets, the relationship between daily changes in pollen, fungal spore concentrations and daily changes in reimbursable systemic antihistamine sales has been investigated between 2005 and 2011 in the Brussels-Capital Region. A Generalized Linear Model was used and adjusted for air pollution, meteorological conditions, flu, seasonal component and day of the week. We observed an augmentation in drug sales despite no significant increase in allergen levels in the long term. The relative risk of buying allergy medications associated with an interquartile augmentation in pollen distributions increased significantly for Poaceae, Betula, Carpinus, Fraxinus and Quercus. Poaceae affected the widest age group and led to the highest increase of risk which reached 1.13 (95% CI [1.11–1.14]) among the 19- to 39-year-old men. Betula showed the second most consistent relationship across age groups. Clear identification of the provoking agents may improve disease management by customizing prevention programmes. This work also opens several research perspectives related to impact of climate modification or subpopulation sensitivity.
PMCID: PMC4996865  PMID: 27174430
allergic rhinitis; ecology; fungal spore; medication; pollen; public health
6.  Correction: SmeltCam: Underwater Video Codend for Trawled Nets with an Application to the Distribution of the Imperiled Delta Smelt 
PLoS ONE  2013;8(12):10.1371/annotation/0c42ea0f-6d99-44a7-84ff-aeec57133f13.
PMCID: PMC3862835
7.  SmeltCam: Underwater Video Codend for Trawled Nets with an Application to the Distribution of the Imperiled Delta Smelt 
PLoS ONE  2013;8(7):e67829.
Studying rare and sensitive species is a challenge in conservation biology. The problem is exemplified by the case of the imperiled delta smelt Hypomesus transpacificus, a small delicate fish species endemic to the San Francisco Estuary, California. Persistent record-low levels of abundance and relatively high sensitivity to handling stress pose considerable challenges to studying delta smelt in the wild. To attempt to overcome these and other challenges we have developed the SmeltCam, an underwater video camera codend for trawled nets. The SmeltCam functions as an open-ended codend that automatically collects information on the number and species of fishes that pass freely through a trawled net without handling. We applied the SmeltCam to study the fine-scale distribution of juvenile delta smelt in the water column in the upper San Francisco Estuary. We learned that during flood tides delta smelt were relatively abundant throughout the water column and that during ebb tides delta smelt were significantly less abundant and occurred only in the lower half and sides of the water column. The results suggest that delta smelt manipulate their position in the water column to facilitate retention in favorable habitats. With the application of the SmeltCam we increased the survival of individual delta smelt by 72% compared to using a traditional codend, where all of the fish would have likely died due to handling stress. The SmeltCam improves upon similar previously developed silhouette photography or video recording devices and demonstrates how new technology can be developed to address important questions in conservation biology as well as lessen the negative effects associated with traditional sampling methods on imperiled species.
PMCID: PMC3701597  PMID: 23861814
8.  Sulfide‐ and nitrite‐dependent nitric oxide production in the intestinal tract 
Microbial Biotechnology  2012;5(3):379-387.
In the gut ecosystem, nitric oxide (NO) has been described to have damaging effects on the energy metabolism of colonocytes. Described mechanisms of NO production are microbial reduction of nitrate via nitrite to NO and conversion of l‐arginine by NO synthase. The aim of this study was to investigate whether dietary compounds can stimulate the production of NO by representative cultures of the human intestinal microbiota and whether this correlates to other processes in the intestinal tract. We have found that the addition of a reduced sulfur compound, i.e. cysteine, contributed to NO formation. This increase was ascribed to higher sulfide concentrations generated from cysteine that in turn promoted the chemical conversion of nitrite to NO. The NO release from nitrite was of the order of 4‰ at most. Overall, it was shown that two independent biological processes contribute to the chemical formation of NO in the intestinal tract: (i) the production of sulfide by fermentation of sulfur containing amino acids or reduction of sulfate by sulfate reducing bacteria, and (ii) the reduction of nitrate to nitrite. Our results indicate that dietary thiol compounds in combination with nitrate may contribute to colonocytes damaging processes by promoting NO formation.
PMCID: PMC3821680  PMID: 22129449
9.  Human biomonitoring on heavy metals in Ath: methodological aspects 
Archives of Public Health  2011;69(1):10.
The municipality of Ath is characterised by the presence, in its center, of two non-ferrous metal industries whose emissions make local residents concerned for their health. Therefore, authorities of the Walloon Region and the municipality of Ath undertook biomonitoring to assess the impact of those industrial emissions on heavy metal body burden in humans.
This paper describes the study design and methodology used to carry out this human biomonitoring.
A random sampling was done in the general population, in two areas of Ath: an area centered around the industries and a peripheral area. The target population was children (2.5-11 years) and adults (40-60 years) without occupational exposure. The three-stage sampling procedure consisted of a mixture of both mail and telephone recruitment. Firstly, 3259 eligible people, identified from a population register, were mailed an introductory letter. In a second stage, eligible individuals were contacted by phone to propose them to participate in the study. They were randomly contacted until the required sample size was obtained. In the third stage, a second mail was sent to those who agreed to participate with a questionnaire to be filled out. Finally, biological samples (blood and urine) from 278 persons were collected. The final participation rate of this study was 24%.
This sampling procedure, especially designed for the purpose of this biomonitoring study in Ath, allowed us to recruit a sample representative of the population of children and adults of Ath, reaching the expected sample size in a short period of time.
PMCID: PMC3436742  PMID: 22958427
Ath; biomonitoring; heavy metals; methodology; sampling; study design
10.  Physical characteristics of the back are not predictive of low back pain in healthy workers: A prospective study 
In the working population, back disorders are an important reason for sick leave and permanent work inability. In the context of fitting the job to the worker, one of the primary tasks of the occupational health physician is to evaluate the balance between work-related and individual variables. Since this evaluation of work capacity often consists of a physical examination of the back, the objective of this study was to investigate whether a physical examination of the low back, which is routinely performed in occupational medicine, predicts the development of low back pain (LBP).
This study is part of the Belgian Low Back Cohort (BelCoBack) Study, a prospective study to identify risk factors for the development of low back disorders in occupational settings. The study population for this paper were 692 young healthcare or distribution workers (mean age of 26 years) with no or limited back antecedents in the year before inclusion. At baseline, these workers underwent a standardised physical examination of the low back. One year later, they completed a questionnaire on the occurrence of LBP and some of its characteristics. To study the respective role of predictors at baseline on the occurrence of LBP, we opted for Cox regression with a constant risk period. Analyses were performed separately for workers without any back antecedents in the year before inclusion ('asymptomatic' workers) and for workers with limited back antecedents in the year before inclusion ('mildly symptomatic' workers).
In the group of 'asymptomatic' workers, obese workers showed a more than twofold-increased risk on the development of LBP as compared to non-obese colleagues (RR 2.57, 95%CI: 1.09 – 6.09). In the group of 'mildly symptomatic' workers, the self-reports of pain before the examination turned out to be most predictive (RR 3.89, 95%CI: 1.20 – 12.64).
This study showed that, in a population of young workers wh no or limited antecedents of LBP at baseline, physical examinations, as routinely assessed in occupational medicine, are not useful to predict workers at risk for the development of back disorders one year later.
PMCID: PMC2630962  PMID: 19123931
11.  The role of physical workload and pain related fear in the development of low back pain in young workers: evidence from the BelCoBack Study; results after one year of follow up 
To study the influence of work related physical and psychosocial factors and individual characteristics on the occurrence of low back pain among young and pain free workers.
The Belgian Cohort Back Study was designed as a prospective cohort study. The study population of this paper consisted of 716 young healthcare or distribution workers without low back pain lasting seven or more consecutive days during the year before inclusion. The median age was 26 years with an interquartile range between 24 and 29 years. At baseline, these workers filled in a questionnaire with physical exposures, work related psychosocial factors and individual characteristics. One year later, the occurrence of low back pain lasting seven or more consecutive days and some of its characteristics were registered by means of a questionnaire. To assess the respective role of predictors at baseline on the occurrence of low back pain in the following year, Cox regression with a constant risk period for all subjects was applied.
After one year of follow up, 12.6% (95% CI 10.1 to 15.0) of the 716 workers had developed low back pain lasting seven or more consecutive days. An increased risk was observed for working with the trunk in a bent and twisted position for more than two hours a day (RR 2.2, 95% CI 1.2 to 4.1), inability to change posture regularly (RR 2.1, 95% CI 1.3 to 3.5), back complaints in the year before inclusion (RR 1.7, 95% CI 1.1 to 2.8), and high scores of pain related fear (RR 1.8, 95% CI 1.0 to 3.1). Work related psychosocial factors and physical factors during leisure time were not predictive.
This study highlighted the importance of physical work factors and revealed the importance of high scores of pain related fear in the development of low back pain among young workers.
PMCID: PMC2078035  PMID: 16361405
low back pain; pain related fear; physical work factors; prospective; young workers
12.  Arthroscopic meniscus repair in the ACL-deficient knee 
International Orthopaedics  2005;29(2):109-112.
Between 1985 and 1995, 45 patients underwent closed meniscus repair. There were 30 men and 15 women with a mean age of 32.5 years. In 23 patients, the anterior cruciate ligament was intact (group 1) whereas it was deficient in 22 patients (group 2). All patients were managed with the same postoperative program of partial weight bearing, immediate motion and rehabilitation of the knee. Five patients had a failed meniscal repair and underwent a repeat arthroscopy and a partial meniscectomy. These patients were considered as failures and excluded from the final scoring. After a mean follow-up of more than 9 years, all patients were subjected to a clinical examination using the Hospital for Special Surgery (HSS) knee rating system. Seven patients in group 2 had episodes of frequent giving way and had their anterior cruciate ligament (ACL) reconstructed 6 and 7 years after the initial meniscus repair. None of the other patients had any clinical symptoms or signs of a meniscal tear. In group 1, 20 patients and in group 2, 14 patients, all had a satisfactory knee score. Even though the failure rate of meniscus repair may be greater in an unstable knee, it is concluded that meniscal repair is not contraindicated in a knee with a deficient ACL.
PMCID: PMC3474515  PMID: 15696316

Results 1-12 (12)