R. Jeffrey Lewis

Factors associated with self-reported musculoskeletal discomfort in video display terminal (VDT) users

Abstract The purpose of this study was to identify risk factors associated with the self-reported musculoskeletal discomfort in a population of video display terminal (VDT) operators. The data were collected via a survey administered to 373 persons who use a VDT at a corporate office site; 292 of the surveys were returned (78%). Respondents were asked to report on symptoms for six body regions, as well as job requirement information, demographic information, and a question regarding non-occupational hobbies. Six specific body regions were included: head and eyes, neck and upper back, lower back, shoulders, elbows and forearms, and hands and wrists. Descriptive information on these data was obtained through exploratory factor analysis, while logistic regression was used to estimate risk. The results indicated a statistically significant increased risk of discomfort on each of the body regions as the number of hours of keyboard use increases. Improper monitor and keyboard position were also significantly associated with head/eye and shoulder/back discomfort, respectively. These results emphasize the importance of workstation ergonomics and the need to limit the number of uninterrupted hours at the keyboard to reduce musculoskeletal symptoms. Relevance to industry VDTs are ubiquitous in the workplace, even outside the office environment. Understanding risk factors for musculoskeletal discomfort among VDT users will help reduce cost associated with lost time, medical expenses and lost productivity due to improper use of VDTs in the workplace.

Effectiveness of a VDT ergonomics training program

Abstract This study evaluated the effectiveness of an ergonomics training program directed toward video display terminal (VDT) users in an office environment. The goals of the training were to teach VDT users to evaluate and adjust their own workstations (i.e., a self-directed intervention) and confer upon each user the responsibility of maintaining an ergonomic workstation, with the ultimate aim of reducing musculoskeletal symptoms. Questionnaires were administered to 170 participants before and after the program to determine changes in both workstation configuration and self-reported musculoskeletal symptoms. The results indicated statistically significant positive changes in two workstation configuration variables (head and mouse position). There were statistically significant improvements observed in the severity of symptoms. The presence of symptoms did not show a statistically significant reduction; however there was a trend toward a reduction in frequency. The results suggest the program was effective in changing reported workstation configuration/posture, which resulted in a reduction of symptom severity over the period of the study. Longer-term follow up may be necessary to detect statistically significant changes in the presence of symptoms. Relevance to industry Musculoskeletal injuries associated with improper video display terminal (VDT) workstation setup represent a health and financial burden to employees and industry. Training programs to provide employees with the necessary ergonomics knowledge and skills regarding proper workstation setup may be effective in reducing and preventing musculoskeletal symptoms and injuries.

Musculoskeletal disorder worker compensation costs and injuries before and after an office ergonomics program

Abstract This study assessed the effectiveness of an office ergonomics training program for video display terminal (VDT) users. Worker compensation costs and injury rates for the VDT-related musculoskeletal disorders (MSDs) were examined before and after implementation of training at two company locations. A greater number of claims were filed in the post- ( n =18) versus pre-intervention period ( n =12), but the average cost per claim was considerably reduced (

Guidance on assessing the methodological and reporting quality of toxicologically relevant studies: A scoping review

1553 in the post- versus

A systematic approach for evaluating and scoring human data

15,141 in the pre-intervention period). This reduced cost per claim is consistent with the programs emphasis on seeking early treatment for MSD-related symptoms. The average injury rate also was reduced in the post- (6.94 per 1000 employees) versus pre-intervention period (16.8 per 1000 employees). These results suggest that self-direct office ergonomic interventions may be effective in reducing the MSD-related worker compensation costs and injury rates. Relevance to industry Office ergonomic training programs are used to prevent and control musculoskeletal disorders among the VDT users. Programs that provide employees with the necessary ergonomics knowledge and skills regarding proper workstation setup may be effective in reducing the injury rates and costs associated with those injuries.

Chronic low-level hydrogen sulfide exposure and potential effects on human health: A review of the epidemiological evidence

Assessments of methodological and reporting quality are critical to adequately judging the credibility of a studys conclusions and to gauging its potential reproducibility. To aid those seeking to assess the methodological or reporting quality of studies relevant to toxicology, we conducted a scoping review of the available guidance with respect to four types of studies: in vivo and in vitro, (quantitative) structure-activity relationships ([Q]SARs), physico-chemical, and human observational studies. Our aims were to identify the available guidance in this diverse literature, briefly summarize each document, and distill the common elements of these documents for each study type. In general, we found considerable guidance for in vivo and human studies, but only one paper addressed in vitro studies exclusively. The guidance for (Q)SAR studies and physico-chemical studies was scant but authoritative. There was substantial overlap across guidance documents in the proposed criteria for both methodological and reporting quality. Some guidance documents address toxicology research directly, whereas others address preclinical research generally or clinical research and therefore may not be fully applicable to the toxicology context without some translation. Another challenge is the degree to which assessments of methodological quality in toxicology should focus on risk of bias - as in clinical medicine and healthcare - or be broadened to include other quality measures, such as confirming the identity of test substances prior to exposure. Our review is intended primarily for those in toxicology and risk assessment seeking an entry point into the extensive and diverse literature on methodological and reporting quality applicable to their work.

Preliminary evaluation of the human relevance of respiratory tumors observed in rodents exposed to naphthalene

An approach is described for how the quality of human data can be systematically assessed and categorised. The approach mirrors the animal data quality considerations set out by Klimisch et al., in order that human data quality can be addressed in a complementary manner and to help facilitate transparent (and repeatable) weight of evidence comparisons. Definitions are proposed for the quality and adequacy of data. Quality is differentiated into four categories. A description of how the scheme can be used for evaluating data reliability, especially for use when contributing entries to the IUCLID database, is shown. A discussion of how the criteria might also be used when determining overall data relevance is included. The approach is intended to help harmonise human data evaluation processes worldwide.

Approaches for describing and communicating overall uncertainty in toxicity characterizations: U.S. Environmental Protection Agency's Integrated Risk Information System (IRIS) as a case study.

Abstract The effects of exposure to high concentrations of hydrogen sulfide (H2S) on human health are well known. However, the potential human health hazards posed by low-level chronic environmental H2S exposure are being debated. Accordingly, we reviewed the literature regarding the effects of chronic, environmentally-relevant H2S exposures on human health. All human observational studies using an analytical study design (e.g. cohort, cross-sectional, case-control) to evaluate chronic-duration low-level H2S exposure (approximately ≤ 10 ppm on average, for 1 year or more), were evaluated for a range of health outcomes. Respiratory symptoms in both adults and children were the most consistently reported symptoms on the increase. When reported, such effects appear to be temporary, given that there is no consistent evidence of pulmonary function deficit in either age group, among those chronically exposed to low H2S concentrations. While sparse, some data also suggest potential ocular symptoms and disorders associated with chronic ambient level H2S exposure in adults (not children), but the limited data on H2S exposures, co-exposures and/or strong odor stimulus of H2S, temper interpretation. Neurological symptoms and deficits have been reported in some studies, but the highest quality evidence, obtained using objective outcome measures and a reasonably detailed assessment of exposure, does not support a neurological-related risk in adults (only one study in children). For the other endpoints assessed (cardiovascular, reproductive and developmental, and carcinogenicity), the results were mixed and/or conflicting, but did not indicate a potential health hazard, although this literature has several major limitations, particularly with regard to exposure estimation and the ability to assess exposure-response.

Naphthalene animal carcinogenicity and human relevancy: Overview of industries with naphthalene-containing streams

Inhalation bioassays in mice and rats exposed to naphthalene (NA) show incidences of lung and nasal cancer, respectively. This paper describes a preliminary mode of action (MOA)/human relevance (HR) framework for NA. Species differences in both carcinogenic and cytotoxic responses between the rodent and human have been noted based on qualitative and quantitative differences in metabolism. Some occur at the initial oxidation of NA in the rat through CYP2F, versus CYP2A13 metabolism in the human respiratory system and which results in a difference in the specific naphthoquinone formed. Normally, subsequent reactive metabolites are then conjugated through glutathione, but high dose exposures, as in the rat bioassay, result in glutathione depletion, and the availability of 1,2-naphthoquinone for other conjugation. In the rat nose, it is proposed that a naphthoquinone imine is formed via a species and site-specific aryl amidase acting on an amino acid conjugate of the quinone. Such a quinone imine is believed to be the active agent in Alachlor and phenacetin, resulting in the same profile of respiratory tumors in the rat as NA. Based on the MOA and the limited epidemiological data indicating no human evidence of nasal or lung tumor risk, the carcinogenic response observed in rats does not appear relevant to the human.

A framework for fit-for-purpose dose response assessment.

Single point estimates of human health hazard/toxicity values such as a reference dose (RfD) are generally used in chemical hazard and risk assessment programs for assessing potential risks associated with site- or use-specific exposures. The resulting point estimates are often used by risk managers for regulatory decision-making, including standard setting, determination of emission controls, and mitigation of exposures to chemical substances. Risk managers, as well as stakeholders (interested and affected parties), often have limited information regarding assumptions and uncertainty factors in numerical estimates of both hazards and risks. Further, the use of different approaches for addressing uncertainty, which vary in transparency, can lead to a lack of confidence in the scientific underpinning of regulatory decision-making. The overarching goal of this paper, which was developed from an invited participant workshop, is to offer five approaches for presenting toxicity values in a transparent manner in order to improve the understanding, consideration, and informed use of uncertainty by risk assessors, risk managers, and stakeholders. The five approaches for improving the presentation and communication of uncertainty are described using U.S. Environmental Protection Agencys (EPAs) Integrated Risk Information System (IRIS) as a case study. These approaches will ensure transparency in the documentation, development, and use of toxicity values at EPA, the Agency for Toxic Substances and Disease Registry (ATSDR), and other similar assessment programs in the public and private sector. Further empirical testing will help to inform the approaches that will work best for specific audiences and situations.