Cold Response of Digital Vessels and Metrics of Daily Vibration Exposure

The cold response of the digital arteries in a cohort of vibration-exposed workers was related to measures of daily vibration exposure expressed in terms of r.m.s. acceleration magnitude normalised to an 8-hour day, and frequency was weighted according to either the frequency weighting Wh defined in ISO 5349-1:2001 (Ah(8) in ms−2 r.m.s) or the hand–arm vascular frequency weighting Wp proposed in the ISO Technical Report 18570:2017 (Ap(8) in ms−2 r.m.s.). The metric Ap(8), which assigns more weight to intermediate- and high-frequency vibrations (31.5–250 Hz), performed better for the prediction of cold-induced digital arterial hyperresponsiveness in the vibration-exposed workers than the measure Ah(8) derived from the conventional ISO frequency weighting, which gives more importance to lower-frequency vibrations (≤ 16 Hz)

A note on prognostic accuracy evaluation of regression models applied to longitudinal autocorrelated binary data

Background: Focus of this work was on evaluating the prognostic accuracy of two approaches for modelling binary longitudinal outcomes, a Generalized Estimating Equation (GEE) and a likelihood based method, Marginalized Transition Model (MTM), in which a transition model is combined with a marginal generalized linear model describing the average response as a function of measured predictors. Methods: A retrospective study on cardiovascular patients and a prospective study on sciatic pain were used to evaluate discrimination by computing the Area Under the Receiver-Operating-Characteristics curve, (AUC), the Integrated Discrimination Improvement (IDI) and the Net Reclassification Improvement (NRI) at different time occasions. Calibration was also evaluated. A simulation study was run in order to compare model’s performance in a context of a perfect knowledge of the data generating mechanism. Results: Similar regression coefficients estimates and comparable calibration were obtained; an higher discrimination level for MTM was observed. No significant differences in calibration and MSE (Mean Square Error) emerged in the simulation study, that instead confirmed the MTM higher discrimination level. Conclusions: The choice of the regression approach should depend on the scientific question being addressed, i.e. if the overall population-average and calibration or the subject-specific patterns and discrimination are the objectives of interest, and some recently proposed discrimination indices are useful in evaluating predictive accuracy also in a context of longitudinal studie

Reduction in finger blood flow induced by hand-transmitted vibration: effect of hand elevation

Objectives This study investigated the effect of hand elevation on reductions in finger blood flow (FBF) induced by hand-transmitted vibration. Methods Fourteen males attended six sessions on six separate days, with a control sessions and a vibration session (125-Hz vibration at 44 ms 2 r.m.s.) with the right hand supported at each of three elevations: 20 cm below heart level (HL), at HL, and 20 cm above HL. Finger blood flow on the left and right hand was measured every 30 s during each 25-minute session comprised of five periods: (i) no force and no vibration (5 minutes), (ii) 2-N force and no vibration (5 minutes), (iii) 2-N force and vibration (5 minutes), (iv) 2-N force and no vibration (5 minutes), and (v) no force and no vibration (5 minutes). Results Without vibration, FBF decreased with increasing elevation of the hand. During vibration of the right hand, FBF reduced on both hands. With elevation of the right hand, the percentage reduction in FBF due to vibration (relative to FBF on the same finger at the same elevation before exposure to vibration) was similar on the middle and little fingers of both hands. After cessation of vibration, there was delayed return of FBF with all three hand heights. Conclusions Vibration of one hand reduces finger blood flow on both exposed and unexposed hands, with the reduction dependent on the elevation of the hand. The mechanisms responsible for vibration-induced reductions in FBF seem to reduce blood flow as a percentage of the blood flow without vibration. Tasks requiring the elevation of the hands will be associated with lower FBF, and the FBF will be reduced further if there is exposure to hand-transmitted vibration

A note on prognostic accuracy evaluation of regression models applied to longitudinal autocorrelated binary data

Background: Focus of this work was on evaluating the prognostic accuracy of two approaches for modelling binary longitudinal outcomes, a Generalized Estimating Equation (GEE) and a likelihood based method, Marginalized Transition Model (MTM), in which a transition model is combined with a marginal generalized linear model describing the average response as a function of measured predictors. Methods: A retrospective study on cardiovascular patients and a prospective study on sciatic pain were used to evaluate discrimination by computing the Area Under the Receiver-Operating-Characteristics curve, (AUC ), the Integrated Discrimination Improvement (IDI) and the Net Reclassification Improvement (NRI) at different time occasions. Calibration was also evaluated. A simulation study was run in order to compare model’s performance in a context of a perfect knowledge of the data generating mechanism. Results: Similar regression coefficients estimates and comparable calibration were obtained; an higher discrimination level for MTM was observed. No significant differences in calibration and MSE (Mean Square Error) emerged in the simulation study; MTM higher discrimination level was confirmed. ConclusionS: The choice of the regression approach should depend on the scientific question being addressed: whether the overall population-average and calibration are the objectives of interest, or the subject-specific patterns and discrimination. Moreover, some recently proposed discrimination indices are useful in evaluating predictive accuracy also in a context of longitudinal studies

An overview of low back pain and occupational exposures to whole-body vibration and mechanical shocks

This paper offers an overview of the relation of low back pain (LBP) to occupational exposures to whole-body vibration (WBV) and mechanical shocks. LBP is a condition of multifactorial origin and is a very common health problem in the general population. Among occupational risk factors, epidemiological studies of driving occupations have provided evidence for strong associations between LBP and occupational exposures to WBV and mechanical shocks. Since it is hard to separate the contribution of WBV exposure to disorders in the lower back from that of other individual, ergonomic or psychosocial risk factors, a quantitative exposure-response relationship for WBV cannot be outlined precisely. Experimental research has provided biodynamic support to the findings of epidemiological studies, showing that in controlled laboratory conditions exposure to WBV can cause mechanical overload to the human spine. The EU Directive on mechanical vibration has established daily exposure action and limit values to protect the workers against the risk from WBV. There is some evidence that the EU exposure limit values are excessive, so much so that an elevated risk of LBP has been found for WBV exposures beneath the EU limit values. In the Italian arm of the EU VIBRISKS prospective cohort study of professional drivers, measures of internal lumbar load (compressive and shear peak forces), calculated by means of anatomy-based finite-element models, were found better predictors of the occurrence over time of low back disorders than the metrics of external exposure suggested by the EU Directive on mechanical vibration. Further biodynamic and epidemiological studies are needed to validate the findings of the VIBRISKS study

Combined Effects of Noise and Hand-transmitted Vibration on Workers’ Muscle and Mental Fatigues in a Simulated Construction Operation

Background: The frequent use of hand-held vibrating tools by construction workers exposes them to hand-transmittedvibratio n (HTV) and noise. This study investigated the effect of combined exposure to HTV and noise on workers’ fatigues under simulated work with a typical building destruction tool. Methods:The repeated measures study was conducted on 40 construction workers exposed to HTV (5 m/s2 rms with frequencies of 31.5, 63, and 125 Hz), HTV (10 m/s2 rms- 31.5 Hz), noise (90 dBA), and concurrent exposure (noise (90 dBA) + HTV (10 m/s2 rms- 31.5 Hz)) with the typical vibrating hand-held tool for 30 minutes. Electromyography signals determined each worker’s fatigue level in the Flexor digitorum superficialis (FDS) muscle in two pre- and post-exposure periods. The subjects also filled out the visual analog scale to evaluate mental fatigue severity subjectively. Results: The mean difference of muscle fatigue parameters was significant in all scenarios except for the two scenarios of alone exposure to HTV (5 m/s2 -125 Hz) and noise exposure (p-value < 0.05). The mean difference of mental fatigue in all scenarios except for the two scenarios of exposure to HTV (5 m/s2 -125 Hz) and exposure to HTV (5 m/s2 -63 Hz) was significant (p-value < 0.05). The most differences in muscle fatigue parameters (Amplitude = 8.16±5.63, Mean frequency=-4.69±3.78) and mental fatigue (4.97±2.38) were observed in the simultaneous exposure to noise and HTV. Conclusion: Noise exposure alone cannot produce remarkable effects on muscle fatigue but can aggravate the effects of vibrations as a consequence of synergistic interaction. However, the role of noise on perceived mental fatigue was more dominant than the HTV.These findings should be considered to adapt the existing exposure limits to actual work conditions

In vitro dermal penetration of nickel nanoparticles.

Nickel nanoparticles (NiNPs) represent a new type of occupational exposure because, due to the small size/high surface, they can release more Ni ions compared to bulk material. It has been reported a case of a worker who developed sensitization while handling nickel nanopowder without precautions. Therefore there is the need to assess whether the skin absorption of NiNPs is higher compared to bulk nickel. Two independent in vitro experiments were performed using Franz diffusion cells. Eight cells for each experiment were fitted using intact and needle-abraded human skin. The donor phase was a suspension of NiNPs with mean size of 77.7 \ub1 24.1 nm in synthetic sweat. Ni permeated both types of skin, reaching higher levels up to two orders of magnitude in the damaged skin compared to intact skin (5.2 \ub1 2.0 vs 0.032 \ub1 0.010 \u3bcg cm(-2), p = 0.006) at 24 h. Total Ni amount into the skin was 29.2 \ub1 11.2 \u3bcg cm(-2) in damaged skin and 9.67 \ub1 2.70 \u3bcg cm(-2) in intact skin (mean and SD, p = 0.006). Skin abrasions lead to doubling the Ni amount in the epidermis and to an increase of ten times in the dermis. This study demonstrated that NiNPs applied on skin surface cause an increase of nickel content into the skin and a significant permeation flux through the skin, higher when a damaged skin protocol was used. Preventive measures are needed when NiNPs are produced and used due to their higher potential to enter in our body compared to bulk nickel

Transdermal permeation of inorganic cerium salts in intact human skin

The stratum corneum protects the body against external agents, such as metals, chemicals, and toxics. Although it is considered poorly permeable to them, comprising the major barrier to the permeation of such substances, it may become a relevant gate of entry for such molecules. Cerium (Ce) is a lanthanide that is widely used in catalytic, energy, biological and medicinal applications, owing to its intrinsic structural and unique redox properties. Cerium salts used to produce cerium oxide (CeO2) nanostructures can potentially come into contact with the skin and be absorbed following dermal exposure. The objective of this study was to investigate the percutaneous absorption of three inorganic Ce salts: cerium (III) chloride (CeCl3); cerium (III) nitrate (Ce(NO3)3) and ammonium cerium (IV) nitrate (Ce(NH4)2(NO3)6), which are commonly adopted for the synthesis of CeO2 using in vitro - ex vivo technique in Franz diffusion cells. The present work shows that Ce salts cannot permeate intact human skin, but they can penetrate significantly in the epidermis (up to 0.29&nbsp;μg/cm2) and, to a lesser extent in dermis (up to 0.11&nbsp;μg/cm2). Further studies are required to evaluate the potential effects of long-term exposure to Ce

In vitro permeability of silver nanoparticles through porcine oromucosal membrane

Silver nanoparticles (AgNPs) can come in contact with human oral mucosa due to their wide use infood industry and hygiene devices. We evaluate transmucosal absorption of 19 nm AgNPs using excisedporcine buccal mucosa applied on Franz diffusion cells. Two donor solutions were used: one containingAgNPs (0.5 g/L) and one derived from the ultrafiltration of the former and containing only Ag in its solubleform. Experiments were carried out separately for 4 h. Silver flux permeation was demonstrated throughoral mucosa, showing similar values for AgNPs (6.8 \ub1 4.5 ng cm 122h 121) and Ag ions (5.2 \ub1 4.3 ng cm 122h 121).Our study demonstrates that silver can permeate the oromucosal barrier and that absorption is sub-stantially due to Ag ions, since no permeation difference was found using the two solutions. Mucosalabsorption has to be considered in further risk assessment studies

Comparison Between the Biomechanical Responses of the Hand and Foot When Exposed to Vertical Vibration

Workers can be exposed daily to foot-transmitted vibration (FTV) from standing on mobile equipment or vibrating platforms and surfaces. This results in a consistent risk of developing neurological, vascular, and musculoskeletal problems. To date, there are no international stand-ards describing procedures with which to evaluate the health risks deriving from long-term ex-posure to FTV. To study the applicability of hand–arm vibration (HAV) standards to the foot, the biomechanical responses of the hand and foot in terms of the frequency response function upon varying contact conditions were compared. Results evidenced similarities between the responses of the wrist and ankle, with differences in resonance for the fingers and toes. The study confirms that HAV standards are more suitable than whole-body vibration standards for evaluating higher frequency exposure to FTV