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PubMed2003

Influence of traffic patterns on particulate matter and polycyclic aromatic hydrocarbon concentrations in Roxbury, Massachusetts.

Vehicle emissions have been associated with adverse health effects in multiple epidemiological studies, but the sources or constituents responsible have not been established. Characterization of vehicle-related exposures requires detailed information on spatial and temporal trends of various pollutants and the ability to predict exposures in unmonitored settings. To address these issues, in the summer of 2001 we measured continuously particle-bound polycyclic aromatic hydrocarbons (PAHs), ultrafine particles, and PM(2.5) at a number of sites in Roxbury, a neighborhood of Boston, Massachusetts with significant diesel and gasoline-fueled traffic. We took measurements at the side of the road and at varying distances from the road, with simultaneous collection of traffic counts and meteorological conditions. Across all nine sites, median roadside concentrations were 8 ng/m(3) of particle-bound PAHs (range: 4-57), 16,000 ultrafine particles/cm(3) (range: 11,000-53,000), and 54 microg/m(3) of PM(2.5) as measured with a DustTrak (range: 12-86). Concentrations of all pollutants were lower at greater distances from the road, upwind, and at higher wind speeds, with greater concentration gradients for PAHs and ultrafine particles. In linear mixed effects regression models accounting for temporal autocorrelation, large diesel vehicle counts were significantly associated with roadside concentrations of PAHs (P=0.02), with a moderate association with ultrafine particles and little relation with PM(2.5). Although more comprehensive information would be needed for epidemiological applications, these data demonstrate significant spatial and temporal heterogeneity for traffic-related pollutants during the summer in an urban center, with our monitoring and analytical methodology helping to inform source attribution.

Air Pollutants↗

PubMed2006

Personal exposure to benzene from fuel emissions among commercial fishers: comparison of two-stroke, four-stroke and diesel engines.

Commercial fishers are exposed to unburned hydrocarbon vapors and combustion products present in the emissions from their boat engines. The objective of this study was to measure personal exposure to benzene as a marker of fuel exposure, and to predict exposure levels across categories of carbureted two-stroke, four-stroke and diesel engines. A self-monitoring approach, employing passive monitors, was used to obtain measurements of personal exposure to benzene over time. Mixed-effect linear regression models were used to predict exposure levels, identify significant effects and determine restricted maximum likelihood estimates for within- and between-person variance components. Significant fixed effects for engine type and refueling a car or truck were identified. After controlling for refueling, predicted benzene exposure levels to fishers on boats equipped with two-stroke, four-stroke and diesel engines were 58.4, 38.9 and 15.7 microg/m3, respectively. The logged within-person variance component was 1.43, larger than the between-person variance component of 1.13, indicating that the total variation may be attributable to monitor placement, environmental conditions and other factors that change over time as well as differences between individual work practices. The health consequences of exposure to marine engine emissions are not known. The predicted levels are well below those at which health effects have been attributed, however.

Animals↗

PubMed2003

An in vitro study on spontaneous cervical contractility in the cow during oestrus and diestrus.

Cervical smooth muscle specimens were collected from slaughtered cows in oestrus and diestrus. Longitudinal and circular specimens were mounted in organ baths and after equilibration time and 2 g pre-load, their physiologic isometric contractility was recorded for 2.5 h. Area under the curve (AUC), maximal amplitude (Amax), mean amplitude (Amen) and minimal amplitude (Amin) were studied. Differences between cycle phases, between muscle layers and over the recorded time periods were statistically evaluated using linear mixed-effect models. In the cow, physiologic contractility of the cervix decreased significantly over time for all variables evaluated (time as covariate on a continuous scale). Furthermore, for Amax, there was a tendency for an influence of muscle layer (longitudinal > circular). Contractility was not influenced by cycle phases.

Animals↗

PubMedDate not supplied

The incidence and risks of failure to heal after lower extremity amputation for the treatment of diabetic neuropathic foot ulcer.

The primary goal of this retrospective cohort study was to determine the incidence of failure to heal after lower extremity amputation for the treatment of diabetic neuropathic foot ulcer, and the secondary goal was to identify risk factors associated with the outcome. We evaluated 1775 patients who underwent amputation for the treatment of 5314 neuropathic foot ulcers, and who were treated in a network of wound care centers. We calculated the incidence of failure to heal after the initial amputation, and used generalized estimation equations and generalized linear latent and mixed model regression to evaluate the association of failure to heal by the 20th week of care. The unadjusted incidence of failure to heal was 34.01%, and male sex, number of wounds, wound grade, and adjunct therapy were all significantly associated with failure to heal. With the exception of wound grade, the associations were not significantly affected by the treating wound care center, and a sensitivity analysis showed the results to be resistant to the theoretical influence of an unmeasured potential confounder. These findings should be useful to clinicians treating diabetic neuropathic foot ulcers, and should aid surgeons in the determination of the most appropriate level for lower extremity amputation.

Age Factors↗

PubMed2000

Longitudinal evaluation of cardiopulmonary performance during exercise after bone marrow transplantation in children.

OBJECTIVE: Abnormalities in cardiopulmonary performance during exercise have been reported in children after bone marrow transplantation (BMT). We sought to study changes in exercise performance over time in pediatric BMT survivors. STUDY DESIGN: We retrospectively reviewed the results of serial cardiopulmonary exercise tests performed by patients who had undergone BMT at our institution. Four measurements of cardiopulmonary function are reported: maximum cardiac index (MCI), maximal oxygen consumption (Max VO(2)), oxygen consumption at ventilatory threshold (VO(2) at VT), and maximum work (Max Work) performed. A linear mixed-effects model was fitted to assess changes in these parameters over time. RESULTS: Thirty-three patients performed 96 cardiopulmonary exercise tests. MCI and VO(2) at VT were depressed at initial testing and did not change over time. Max VO(2) increased by 4% per year to 69% predicted, and Max Work increased to 77% predicted at 6 years after BMT. CONCLUSIONS: In spite of an impaired cardiovascular response to exercise as indicated by the persistently low MCI, aerobic and physical working capacity increase. Improved Max VO(2) suggests that oxygen extraction at the musculoskeletal level becomes more efficient with recovery from BMT. This may represent a compensatory response to an impaired ability to increase cardiac output.

Adolescent↗

PubMed2002

Amsterdam Cohort Study on HIV and AIDS: impact of exposure to UVR as estimated by means of a 2-year retrospective questionnaire on immune parameters in HIV positive males.

We studied a group of HIV-infected homosexuals who participated in the Amsterdam Cohort Study on HIV and AIDS to investigate whether greater exposure to sunlight is associated with a less favorable course of some important immunological parameters. This was done because ultraviolet radiation (UVR) is potentially harmful to the cellular immunity and may enhance viral replication. The exposure to UVR was estimated by means of a 2-year retrospective questionnaire in 1997. Both a 2-year cumulative estimate and estimates by 3-monthly episodes were calculated. The associations with CD4+ T-cell count, CD4+/CD8+ T-cell ratio, and T-cell reactivity were investigated. First, the associations between the cumulative estimate and the individual slopes of these parameters during the 2 years covered by the questionnaire were explored by means of a robust regression analysis. Secondly, the short-term association with the estimate by episode was examined by means of a linear mixed-effect model for repeated measurements (LME). No statistically significant associations with the cumulative estimate were found. Although a trend to lower values of the immunological parameters studied after short-term greater exposure in the LME model was observed, the differences were not statistically significant either. These findings suggest that exposure to sunlight does not have a suppressive effect on the above mentioned immunological parameters in HIV-infected persons.

Acquired Immunodeficiency Syndrome↗

PubMed2026

Effects of passive blood flow restriction on muscle function following exercise-induced muscle damage in recreationally active males.

This investigation examined the effects of passive blood flow restriction (pBFR) on indices of exercise-induced muscle damage (EIMD) in recreationally active males. Fifteen males completed six consecutive visits (±2 hours). Participants completed 3 × 25 maximal, unilateral, isokinetic (60°·s-1), concentric-eccentric leg extensions on both legs. Each leg was randomly assigned to receive pBFR (80% arterial occlusion pressure) or sham (20 mmHg) at 0, 24, 48, 72, and 96 hours post-EIMD. Perceived muscle soreness, range of motion (ROM), pain pressure threshold (PPT), concentric peak torque (CPT), and maximal voluntary isometric contraction (MVIC) torque were assessed and analyzed using separate linear mixed-effects models. Perceived muscle soreness increased at 24 hours (mean difference [meandiff] = 4.9 au; p < 0.001) and recovered by 96 hours (p = 0.482), with no differences between conditions (p = 0.450). ROM (meandiff = -3.1°; p = 0.040), PPT (meandiff = -1.63 kgf; p < 0.001), CPT (meandiff = -27.7 Nm; p < 0.001), and MVIC torque (meandiff = -30.8 Nm; p < 0.001) decreased at 24 hours, with recovery occurring between 48-96 hours. Condition-specific differences were observed for ROM (meandiff = 2.5°; p < 0.001), PPT (meandiff = 0.49 kgf; p = 0.005), CPT (meandiff = 6.2 Nm; p = 0.020), and MVIC torque (meandiff = 7.1 Nm; p = 0.044), which were greater in pBFR than sham. These findings suggested that pBFR may reduce impairments in ROM, PPT, CPT, and MVIC torque following EIMD, despite a similar recovery trajectory between conditions.

Humans↗

PubMed2026

Differences in circadian rhythm changes between myopic and non-myopic college students over 2 years.

This study aimed to characterize and compare the differences in circadian rhythm changes during 2 years between college students with myopia and non-myopia based on a longitudinal cohort study. Wake-up time and bedtime were obtained through a self-administered questionnaire. Chronotype was assessed using the reduced Morningness-Eveningness Questionnaire (rMEQ). Circadian rhythm timing was determined by dim-light melatonin onset (DLMO), measured through hourly saliva collection from 21:00 to 01:00. A total of 450 college students (146 [32.4%] males) with a mean age of 18.65 ± 1.05 years were included, of whom 353 (78.4%) students had myopia. Compared with non-myopic individuals, myopic students slept later, woke up earlier, and exhibited lower rMEQ scores at baseline. Over the 2-year follow-up, both groups showed significantly earlier bedtimes, later wake-up times, and higher rMEQ scores. Only myopic students demonstrated a 45-minute delay in DLMO after the 2-year follow-up. After adjusting for potential confounders, linear mixed-effects models showed that myopic individuals had later bedtimes and earlier wake-up times. These findings indicate significant circadian rhythm changes in individuals with myopia, suggesting the potential of targeted sleep rhythm interventions on preventing myopia.

Myopia↗

PubMed2026

Repeated low-level red-light therapy for improving asthenopic symptoms and accommodation in presbyopia.

BACKGROUND: To assess the short-term effectiveness of repeated low-level red light (RLRL) therapy in relieving asthenopia and enhancing accommodation in presbyopia. METHODS: This randomized, parallel-group, double-masked clinical trial enrolled adults with presbyopia and self-reported asthenopia. Participants were allocated using computer-generated randomization and randomly assigned at a 1:1 ratio to RLRL or sham groups. Blinding included participants, examiners, assessors, and statisticians. The primary outcome was the change from baseline in the Computer Vision Syndrome Questionnaire (CVS-Q) score at day 31. Secondary outcomes were the change in accommodative amplitude (AA), Near Activity Visual Questionnaire (NAVQ) score, habitual near visual acuity, near-addition power, accommodative facility, positive and negative relative accommodation, binocular cross-cylinder response, and accommodative convergence-to-accommodation ratio. Continuous outcomes were analyzed using linear mixed-effects models. RESULTS: Sixty-four of 66 randomized participants (aged 41-62 years) completed the 1-month trial. At day 31, RLRL showed greater improvement than sham in CVS-Q score (adjusted mean difference, -1.75 points; 95% CI, -3.10 to -0.39), binocular AA (1.09 D; 95% CI, 0.37 to 1.82), and NAVQ score (-8.07 points; 95% CI, -14.17 to -1.97). The effect on AA was most pronounced in a subgroup of eyes with baseline amplitude >2.0 D (adjusted mean difference 1.33 D; 95% CI 0.32-2.34). Other measures did not differ between groups at each visit. No treatment-related adverse events were reported. Adherence was similar between groups (mean compliance: 98.2% vs 97.5%). CONCLUSIONS: Short-term treatment with RLRL significantly reduced asthenopic symptoms and improved accommodative amplitude in individuals with presbyopia.Trial registration: NCT06745661 (registered December 8, 2024).

Humans↗

PubMed2026

Oro-esophageal feeding for tracheostomized patients with severe traumatic brain injury: a randomized controlled trial.

BACKGROUND: This study reports the clinical effects of intermittent oro-esophageal tube feeding (IOE) versus nasogastric tube feeding (NGT) on nutritional status, aspiration pneumonia, decannulation, and level of consciousness in tracheostomized patients with severe traumatic brain injury (sTBI). METHODS: A randomized controlled trial was conducted between March 2024 and October 2025 in China and included tracheostomized patients with sTBI. Participants were randomized 1:1 to the intervention and control groups for 28-day interventions. IOE or NGT was used for nutritional supports, respectively. The primary outcome was nutritional status, including hemoglobin, albumin, prealbumin and body mass index. The secondary outcomes included aspiration pneumonia, decannulation, and level of consciousness assessed using the Glasgow Coma Scale (GCS). Generalized linear mixed-effects models, generalized estimating equations, and Cox regression were used for data analyze. RESULTS: A total of 104 participants were included in the analysis. After intervention, significant interaction effects were observed in hemoglobin (β = 5.272, 95% CI: 2.707, 7.837), albumin (β = 3.675, 95% CI: 1.854, 5.496), prealbumin (β = 11.835, 95% CI: 6.623, 17.047), body mass index (β = 1.719, 95% CI: 0.868, 2.569), the GCS (β = 0.981, 95% CI: 0.572, 1.390), and aspiration pneumonia (OR= 0.304, 95% CI: 0.133, 0.693). The Cox model revealed that group significantly influenced the decannulation outcomes [HR (95% CI) =5.556 (3.197, 9.657), p < 0.001]. CONCLUSIONS: In tracheostomized patients with sTBI who received routine treatment, IOE is more conducive to decannulation and the improvement in nutritional status, aspiration pneumonia, and level of consciousness than NGT. CLINICAL TRIAL REGISTRATION: Prospectively registered at ClinicalTrials.gov (NCT06328985, 03/18/2024, clinicaltrials.gov/study/NCT06328985).

Humans↗

PubMed2026

Long-term microbiome and clinical effects of a microbiome-guided personalized diet versus low-FODMAP diet in irritable bowel syndrome: A 12-month follow-up randomized controlled trial.

Dietary therapy is central to irritable bowel syndrome (IBS) management, yet the long-term durability of the low-FODMAP diet (LFD), and of microbiome-guided personalization, remains unclear. We assessed the long-term clinical and gut-microbiome effects of a microbiome-guided personalized diet (PD) compared with a standard LFD in adults meeting Rome IV criteria for IBS. In this multicenter, open-label randomized controlled trial with blinded outcome assessment, participants who completed a 6-week dietary intervention (PD or LFD) were followed at 6 and 12 months without further dietary intervention. Outcomes included the IBS Severity Scoring System (IBS-SSS), IBS Quality of Life (IBS-QOL), and the Hospital Anxiety and Depression Scale (HADS); gut microbiota were profiled by 16S rRNA sequencing. Longitudinal changes were evaluated using linear mixed-effects models, responder analyses, PERMANOVA, and PERMDISP. Both diets reduced IBS-SSS at 6 weeks. PD maintained symptom improvement at 6 and 12 months (-82.0 and -78.3 points from baseline), whereas LFD benefits regressed by 12 months (+29.3 points; between-group p = 0.001). At 12 months, IBS-SSS responder rates were higher with PD than LFD (62.5% vs 34.5%; absolute risk difference +28.0%, 95% CI 4.2-47.7; Fisher p = 0.029), and IBS-QOL, HADS-anxiety, and HADS-depression showed more favourable trajectories with PD. PD was associated with sustained Shannon alpha-diversity gains (+0.488 at 6 weeks; +0.205 at 12 months; both p < 0.01). A modest between-group beta-diversity difference at 6 months (R2 = 0.035; p = 0.011) was not significant at 12 months. This hypothesis-generating follow-up suggests more durable benefit with PD; larger trials powered for long-term clinical and microbiome outcomes are warranted.

Humans↗

PubMed2002

A randomized, double-blind, placebo-controlled trial of dexamethasone in severe respiratory syncytial virus (RSV) infection: effects on RSV quantity and clinical outcome.

Forty-one previously healthy children <2 years of age who required mechanical ventilation for respiratory syncytial virus (RSV) infection were randomized to receive dexamethasone (0.5 mg/kg; n=22) or saline placebo (n=19) intravenously every 12 h for 4 days. RSV quantity was measured by quantitative plaque assay in fresh tracheal and nasal aspirates obtained at intervals of 24+/-3 h on days 0, 1, 2, 5, and 7 following entry. Analysis by linear mixed-effects modeling demonstrated a significantly greater decline in mean tracheal RSV quantity in the placebo group than in the dexamethasone group from day 0 to day 1 (0.82 vs. 0.21 log pfu/mL; P=.01) and from day 0 to day 2 (1.45 vs. 0.53 log pfu/mL; P=.03). No differences were found between groups in nasal RSV quantity, white blood cell counts in tracheal or nasal aspirates, serum neutralizing antibody titers during convalescence, or duration of mechanical ventilation, intensive care unit stay, or hospital stay.

Antibodies, Viral↗

PubMed2006

An integrated approach to identify spatiotemporal and individual-level determinants of animal home range size.

Animal home range use is a central focus of ecological research. However, how and why home range size varies between individuals is not well studied or understood for most species. We develop a hierarchical analytical approach--using generalized linear mixed-effects modeling of time series of home range sizes--that allows variance in home range size to be decomposed into components due to variation in temporal, spatial, and individual-level processes, also facilitating intra- and interspecific comparative analyses. We applied the approach to data from a roe deer population radiotracked in central Italy. Over multiple timescales, temporal variation is explained by photoperiod and climate and spatial variation by the distribution of habitat types and spatial variance in radiotracking error. Differences between individuals explained a substantial amount of variance in home range size, but only a relatively minor part was explained by the individual attributes of sex and age. We conclude that the choice of temporal scale at which data are collected and the definition of home range can significantly influence biological inference. We suggest that the appropriate choice of scale and definition requires a good understanding of the ecology and life history of the study species. Our findings contrast with several common assumptions about roe deer behavior.

Age Factors↗

PubMed2004

Inhaled steroid delivery from small-volume holding chambers depends on age, holding chamber, and interface in children.

The relationship between the amount of inhaled steroids delivered from pressurized metered-dose inhalers used with their recommended holding chambers and age of the patients using these devices was studied in an open randomised cross-over filter study. We recruited 1-2-month-old healthy infants (n = 21), 2-3-year-old asthmatics (n = 13), 4-6-year-old asthmatics (n = 15), and 10-15-year-old asthmatics (n = 20). Each child inhaled two puffs, administered by a single investigator, of both budesonide through Nebuchamber and fluticasone propionate through Babyhaler, on two occasions. Moreover, the 4-6-year-old group inhaled via both facemask and mouthpiece. Drug, collected on a filter interposed between holding chamber and patient, was analysed by high performance liquid chromatography. Filter dose, expressed in percent of the nominal dose, was analysed in a mixed effect linear regression model with age group, holding chamber and inhalation interface (facemask or mouthpiece) as fixed effects and subject as random effect. Filter dose from both holding chambers increased significantly with age, from 3% with Babyhaler and 7% with Nebuchamber in the youngest children, to 40-41% with both holding chambers in adolescents. Nebuchamber delivered more drug than Babyhaler (p = 0.002), but variability in drug delivery (about 11%) was similar between holding chambers. Filter dose decreased from 35% to 22% with Babyhaler, and from 42% to 27% with Nebuchamber when using a mouthpiece rather than a facemask (p < 0.0001). Delivery of inhaled steroids used with their recommended holding chambers depends from age and holding chamber, but also from the inhalation interface. Lung deposition and clinical studies comparing inhalation from holding chambers with mouthpiece and facemask are urgently required.

Adolescent↗

PubMed2003

Sources of variability in blood pressure measurement using the Dinamap PRO 100 automated oscillometric device.

The Dinamap automated oscillometric device (GE Medical Systems Information Technologies, Inc., Milwaukee, Wisconsin) for blood pressure measurement is widely employed in epidemiologic studies because it is easy to use and because it eliminates observer variability. In this study, the authors assessed the variability in observed blood pressures associated with use of the Dinamap monitor and estimated the contributions of various factors to that variability. In 60 volunteers (30 aged 23-35 years and 30 aged 54-82 years) from New York, New York, the authors obtained 30 simultaneous paired blood pressure measurements in both arms at 1-minute intervals, using three separate Dinamap PRO 100 devices allocated to arm and subject according to a balanced incomplete block design. Variability, defined as the between-arm difference in blood pressure measurements, was analyzed using a mixed-effects linear regression model. A total of 1,800 paired blood pressure measurements were obtained between September 2001 and June 2002. The mean ages of the two groups were 28.3 years (standard deviation, 4.0) and 71.7 years (standard deviation, 8.0). A diagnosis of hypertension was present in 53% of the older subjects and none of the younger subjects. Fifty percent of paired simultaneous blood pressure measurements obtained were in agreement within 4 mmHg for systolic blood pressure or within 3 mmHg for diastolic blood pressure. Residual variability, attributable to the intrinsic inaccuracy of the device, accounted for 64-82% of the total systolic and diastolic blood pressure variability. The majority of variability in blood pressure measurement was due to the device as used under the study conditions.

Adult↗

PubMed2026

Systemic Platelet Activation and Respiratory Exacerbations, Pulmonary Symptoms, and Mortality among Current and Former Smokers in SPIROMICS.

RATIONALE: Platelet activation is elevated in chronic obstructive pulmonary disease (COPD) and associated with self-reported respiratory symptoms. Observational studies link the antiplatelet drug aspirin to lower exacerbation rates and fewer symptoms. However, it is unknown if platelet activation predicts incident respiratory exacerbations or mortality. OBJECTIVE: Is systemic platelet activation prospectively associated with respiratory exacerbations and mortality among ever-smokers with or at risk for COPD? METHODS: We measured two systemic platelet activation biomarkers, urinary 11-dehydro-thromboxane B2 (11dTxB2) and plasma soluble CD40 ligand (sCD40L), at baseline in self-reported aspirin non-users in the longitudinal SPIROMICS cohort. Adjusted generalized negative binomial and linear mixed-effects models assessed associations between these biomarkers and prospective rates of total and severe exacerbations, plus cross-sectional and longitudinal respiratory health (St. George's Respiratory Questionnaire, COPD Assessment Test, modified Medical Research Council questionnaire, and six minute walk distance). Cox proportional hazard and competing risk models evaluated associations between platelet activation biomarkers and all-cause and cause-specific mortality. RESULTS: Among 2,711 participants, 1,572 (58.0%) reported aspirin non-use; of these, 1,433 and 1,437 had 11dTxB2 and sCD40L measured, respectively. Over a median 6.6 years, a two-fold higher baseline 11dTxB2 was associated with increased rates of total (8.8%; 95%CI: 0.4-17.8%) and severe (18.1%; 95%CI: 5.1-32.6%) exacerbations. Although there were no significant interactions, there was a trend toward higher severe exacerbation rates among current cigarettes smokers and those with COPD. There were no significant results for sCD40L. Among aspirin non-users, higher 11dTxB2, but not sCD40L, was associated with worse cross-sectional respiratory health and modestly increased all-cause mortality over a median 8.2 years (adjusted hazard ratio 1.11; 95%CI: 1.00-1.24). After covariate adjustment, there were no associations with longitudinal respiratory health or cause-specific mortality. CONCLUSIONS: Systemic platelet activation, measured by urinary 11dTxB2, is a statistically significant but modest predictor of respiratory exacerbations and all-cause mortality in individuals with or at risk for COPD, suggesting its potential utility as a prognostic and predictive biomarker for antiplatelet therapy trials. CLINICAL TRIAL REGISTRATION: NCT01969344.

aspirin↗

PubMed2005

Investigation of determinants of past and current exposures to formaldehyde in the reconstituted wood panel industry in Quebec.

OBJECTIVES: Past and present formaldehyde measurements made in facilities manufacturing reconstituted wood panels in Quebec have been collected in order to assess formaldehyde exposure and its determinants in this industry. METHODS: All 12 plants manufacturing Oriented-strand board (OSB), Medium density fibreboard (MDF) and Particle board (PB) in Quebec were visited by a research team which took area and personal measurements. Past measurements taken by governmental occupational health teams in these plants were also collected. Log-transformed formaldehyde concentrations were analysed with extended linear mixed-effects models. RESULTS: During 2001-2002, 275 measurements were taken by the research team, while 590 measurements dating back to 1984 were collected from governmental files. The area measurements had a global geometric mean (GM) of 0.28 p.p.m. [geometric standard deviation (GSD): 3.1]. The GM of the personal measurements was 0.17 p.p.m. (GSD: 2.3). The fixed-effects of the models for personal and area measurements explained 61 and 57% of the variance, respectively. Job (working area for area concentrations), process (PB, MDF, OSB), season of sampling, origin of the data (research, governmental) and year of sampling were significant determinants of exposure. Proximity to the press, winter conditions, PB and MDF processes and governmental data resulted in the highest exposures. Significant within-sampling campaign correlation was found for both personal and area models. The final models include different residual variances by process for personal measurements and by working area for area measurements. CONCLUSIONS: Several determinants of exposure to formaldehyde in the reconstituted wood panel industry were successfully identified. Higher levels found in governmental data as compared to research data may be explained by a 'worst-case' strategy bias. The observed intra-sampling campaign correlation supports existing results suggesting that measurements taken in a small time frame tend to be correlated. Exposures in this sector are low compared to most 8 h-TWA occupational exposure limits (e.g. 1 p.p.m.) but close to the most demanding ones (e.g. 0.3 p.p.m.).

Data Collection↗

PubMed2006

From expert-based to quantitative retrospective exposure assessment at a Soderberg aluminum smelter.

OBJECTIVES: Expert judgement of exposure levels is often only poorly or moderately correlated with directly measured levels. For a follow-up of a historical cohort study at a Söderberg aluminum smelter we updated an expert-based semiquantitative job exposure matrix of coal tar pitch volatiles (CTPV) to quantitative estimates of CTPV and benzo(a)pyrene (BaP). METHODS: Mixed effects models to predict exposure for potroom operation and maintenance jobs were constructed from personal CTPV and BaP measurements. Mean exposures of jobs in non-potroom locations were directly calculated when measurements were available. Exposure estimates for jobs/time periods with no measurements were based on proportion of time spent in exposed areas compared to jobs where exposure was modeled or measured. For pre-1977, the original expert exposure assignments were calibrated using the updated 1977 estimates. RESULTS: The rate of change in exposure levels varied by time period and was accounted for in mixed models with a linear spline time trend. Other variables significant in the models were job, potroom group and season as fixed effects, and worker as a random effect. The models for potroom operations explained 45 and 27% of the variability in the CTPV and BaP measurements, respectively. The models for maintenance jobs explained 40 and 19% of the variability in the CTPV and BaP measurements, respectively. For 1977-2000 model estimates, direct calculation of means and extrapolation from modeled/measured exposures accounted for 57, 6 and 37% of the exposed person-years, respectively. CONCLUSIONS: The above methodology maximized the use of exposure measurements and largely replaced the original expert-based estimates. Finer discrimination between exposure levels was possible with the updated exposure assessment. The new estimates are expected to reduce exposure misclassification and help better assess the exposure-response relationships.

Air Pollutants, Occupational↗