Robert B. Dick

A Cross-Sectional Study of Risk Factors for Musculoskeletal Symptoms in the Workplace Using Data From the General Social Survey (GSS)

Objective: Assessments of potential risk factors for musculoskeletal disorders (MSDs) from large, national study populations using personal interviews are critical to our understanding of exposure-response relationships. To address this need, we analyzed two outcome measures—self-reported back pain and upper extremity pain—from the quality of work life (QWL) module of the General Social Survey (GSS). We investigated several individual, psychosocial, and physical factors for their relationship to these outcome measures. Methods: The study population included US adults, noninstitutionalized, English-speaking, aged 18 years or older, and employed at least part time (≥20 hr/wk). Final sample size was 1484 workers. Results: Variables of physical exposure significantly increased the risk of both low back pain and upper extremity pain. Multiple injuries and some psychosocial factors were associated with MSDs, and there was an additive effect on risk of MSDs with exposure to both physical exposure and work stress. Conclusions: A relationship between physical loads and musculoskeletal disorders was indicated by the results, which will enable creating a database for tracking reports of MSDs in the US working population.

Effects of acute exposure of toluene and methyl ethyl ketone on psychomotor performance

SummaryOrganic solvents are used frequently in industry and workers are often exposed to various combinations of these chemicals. Several are CNS depressants, and the purpose of this experiment was to assess the behavioral effects of 4-hour inhalation exposures to two solvents, toluene and methyl ethyl ketone (MEK) alone and combined. Ethanol at 0.08% blood levels was used as a positive control. A total of 144 paid volunteers were randomly assigned to one of eight treatment combinations in a series of four two-group between subjects studies. Testing was carried out in an exposure chamber, and participants were tested before, during, and after the treatment or control condition on three performance tasks. The tasks measured alertness and psychomotor function and produced a total of 28 measures on each individual over the approximate 8 h of testing. Results indicated that toluene at 100 ppm produced a small but significant impairment on one measure of a visual-vigilance task by lowering the percentage of correct hits. MEK at 200 ppm produced no interpretable significant effects on any of these measures. Additivity was not evident when individuals were exposed to MEK (100 ppm) and toluene (50 ppm) in combination, as no significant performance differences were noted. Ethanol, at 0.08%, affected both the visual-vigilance and a choice-reaction time task at statistically significant levels on two measures, confirming the sensitivity of these two tasks to CNS depressants.

Evaluation of acute sensory-motor effects and test sensitivity using termiticide workers exposed to chlorpyrifos

Sensory and motor testing was performed on a group of termiticide workers primarily using chlorpyrifos-containing products to evaluate both the acute effects from current exposure and sensitivity of the measures to detect effects. The study group comprised 106 applicators and 52 nonexposed participants. Current exposure was measured by urinary concentrations of 3,5,6-trichloro-2-pyridinol (TCP) collected the morning of testing. The mean TCP value for the 106 applicators was 200 microg/g creatinine. Participants received 4--5 h of testing and were evaluated using a sensory--motor test battery recommended by a National Institute for Occupational Safety and Health (NIOSH)-sponsored advisory panel to be appropriate for testing effects from pesticide exposures. Measurements testing olfactory dysfunction, visual acuity, contrast sensitivity, color vision, vibrotactile sensitivity, tremor, manual dexterity, eye--hand coordination, and postural stability were analyzed. Study results indicated limited acute effects from exposure to chlorpyrifos using urinary TCP as a measure of current exposure. The effects occurred primarily on measures of postural sway in the eyes closed and soft-surface conditions, which suggests a possible subclinical effect involving the proprioceptive and vestibular systems. Several other tests of motor and sensory functions did not show any evidence of acute exposure effects, although statistically significant effects of urinary TCP on the Lanthony color vision test scores and one contrast sensitivity test score were found. The visual measures, however, were not significant when a step-down Bonferroni correction was applied. Information also is presented on the sensitivity of the measures to detect effects in an occupationally exposed population using standard error of the parameter estimates.

Neurobehavioural effects of short duration exposures to acetone and methyl ethyl ketone

A total of 137 volunteers were recruited and tested for neurobehavioural performance before, during, and after a short duration (4 h) exposure to acetone at 250 ppm, methyl ethyl ketone (MEK) at 200 ppm, acetone at 125 ppm with MEK at 100 ppm, or a placebo. Ethanol (95%-0.84 ml/kg) was used as a positive control. Performance testing was computer controlled and took place in an environmental chamber with four test stations. The total test regimen before, during, and after exposure covered 10 hours and 32 measures were collected. The measurements were extracted from two biochemical (venous blood and alveolar breath) tests, four psychomotor (choice reaction time, visual vigilance, dual task (auditory tone discrimination and tracking), memory scanning) tests, one sensorimotor (postural sway) test, and one psychological (profile of mood states (POMS] test. The exposure to 250 ppm acetone produced small but statistically significant changes in performance from controls in two measures of the auditory tone discrimination task and on the anger hostility scale (men only) of the POMS test. Neither MEK nor the combined acetone/MEK exposures produced statistically significant interpretable results. The combination exposure provides some indication that there was no potentiation of the acetone effects with the coexposure to MEK or vice versa. More pronounced performance decrements occurred with ethanol at 0.07-0.08% BAC. Significant (less than 0.05) differences were evident on both the auditory tone and tracking tests in the dual task and there was partial significance on the visual vigilance test (0.05-0.06) and some postural sway measures (less than 0.09). These findings agree with an earlier Japanese study in showing some mild decrements on behavioural performance tests with exposures to acetone at 250 ppm.

Trends in work-related musculoskeletal disorders: a comparison of risk factors for symptoms using quality of work life data from the 2002 and 2006 general social survey.

Objective: To report trends for the risk of musculoskeletal disorders. Methods: Three Quality of Work Life surveys examine the risk factors for musculoskeletal disorders. Results: Findings similar for several risk factors, but differences across the reporting years may reflect economic conditions. Respondent numbers in 2010 were reduced, some risk factors had pattern changes, and there were sex and age differences. Trend analysis showed most significant changes were for the “work fast” risk factor. New 2010 “physical effort” item showed sex differences, and items reflective of total worker health showed strong associations with “back pain” and “pain in arms.” Conclusions: Intervention strategies should focus on physical exposures and psychosocial risk factors (work stress, safety climate, job satisfaction, supervisor support, work fast, work freedom, work time) that have been consistently related to reports of musculoskeletal disorders. Economic conditions will influence some psychosocial risk factors.

Are aluminium potroom workers at increased risk of neurological disorders

OBJECTIVE: To determine whether long term potroom workers in an aluminium smelter are at increased risk of neurological disorders. METHODS: Cross sectional study of 63 current and former aluminium potroom workers first employed before 1970 and with at least 10 years of service. A group of 37 cast house and carbon plant workers with similar durations of employment and starting dates in the same smelter were used as controls. The prevalence of neurological symptoms was ascertained by questionnaire. Objective tests of tremor in both upper and lower limbs, postural stability, reaction time, and vocabulary were conducted. All subjects were examined by a neurologist. RESULTS: No significant differences in age, race, or education were found between the two groups. Although the potroom group had higher prevalences for all but one of the neurological symptoms, only three odds ratios (ORs) were significantly increased; for incoordination (OR 10.6), difficulty buttoning (OR 6.2), and depression (OR 6.2). Tests of arm or hand and leg tremor in both the visible and non-visible frequencies did not show any significant differences between the two groups. Testing of postural stability showed no definitive pattern of neurologically meaningful differences between the groups. There were no significant differences between the two groups in reaction time, vocabulary score, or clinical neurological assessment. CONCLUSIONS: The objective measures of neurological function provided little support for the finding of increased neurological symptom prevalences in the potroom workers, although increased symptoms may be an indicator of early, subtle neurological changes. The results provide no firm basis for concluding that neurological effects among long term potroom workers are related to the working environment, in particular aluminium exposure, in potrooms. These findings should be treated with caution due to the low participation of former workers and the possibility of information bias in the potroom group.

Use of a computerized postural sway measurement system for neurobehavioral toxicology

The study of standing posture has been associated with nervous system functioning for over a hundred years. Measures of human standing ability have attracted some attention as indicators of neurotoxic insult. The use of postural sway measures as subclinical indicators of toxicity has not been regularly incorporated into most neurobehavioral test batteries, but the development of microcomputer-controlled systems offers new possibilities. The mechanisms involved in controlling postural sway are discussed, as well as the various measurement techniques. In addition, studies involving the effects of some neurotoxic agents are cited. A postural sway measurement system that is noninvasive, has 1-2-minute test periods, provides immediate test results, and is relatively free of practice and motivation effects is described. Results present the normative characteristics of the sway parameters, a comparison of three data transformation techniques, and the effects of height and weight on the sway parameters. Power calculations were also performed to estimate the number of subjects needed to detect effects at both the 80% and 90% power levels.

Effects of short duration exposures to acetone and methyl ethyl ketone

Workers are commonly exposed to mixtures or combinations of chemical agents, and these mixtures often consist of solvents. One group of solvents that has been extensively studied for its neurotoxic properties has been the ketones. However, previous research has focused on neuropathies produced by extended exposures and not on the simple pharmacokinetics or the reversible central nervous system (CNS) effects from short-duration exposures. In this research, 137 volunteers were recruited and tested for neurobehavioral performance changes and biochemical indicators during and after a short-duration (4-h) exposure to either acetone at 250 ppm, methyl ethyl ketone (MEK) at 200 ppm, acetone at 125 ppm with MEK at 100 ppm, or a chemical-placebo. Ethanol (95%, 0.84 ml/kg) was used as a positive control. Testing took place in an environmental chamber with four test stations. The computer-controlled test regimen took 10 h, and several measures were collected: (1) biochemical measurements of venous blood and alveolar breath; (2) psychomotor tests of choice reaction time, visual vigilance, dual task (auditory tone discrimination and tracking), and memory scanning; (3) one sensorimotor (postural sway) test; and (4) one psychological (Profile of Mood States [POMS]) test. Blood and breath concentrations during and after exposure did not demonstrate any interaction between the two solvents, nor were statistically significant sex differences present during uptake or elimination. The 250-ppm acetone exposure produced small but statistically significant differences from controls in two measures of the auditory tone discrimination task, and on the anger-hostility scale (males only) of the POMS test. The other chemical exposure conditions, MEK at 200 ppm and combination MEK with acetone, produced no consistent statistically significant results, which suggests there was no potentiation of the acetone effects with the co-exposure to MEK or vice versa under these test conditions. Ethanol at 0.07-0.08% blood alcohol concentration (BAC) caused significant decrements on both the auditory tone and tracking tests in the dual task.

Evaluation of tremor in aluminum production workers

A cross-sectional study of 63 current and former aluminum potroom workers and 37 comparison workers was conducted to evaluate for evidence of neurological dysfunction, including tremor from long-term exposures to aluminum using sensitive quantitative measures of arm/hand and leg tremor. Signs of upper extremity tremor were also evaluated by neurological examination and compared with the quantitative measures of arm/hand tremor. Both arm/hand and leg tremor were measured using fatiguing test conditions, but no statistically significant differences due to exposure to aluminum were present between the potroom workers and the comparison workers. The neurological examination also showed no statistically significant differences between the groups on the evaluation of signs of tremor. These results do not support the findings of Best-Pettersen et al., who reported evidence of increased tremor in aluminum workers using the static steadiness test in the Halstead-Reitan battery. Differences between the studies that may have contributed to the contrasting results are discussed. In addition, techniques are presented for using microcomputer-controlled devices to evaluate tremor in both the visible (1-6 Hz) and nonvisible (7-18 Hz) frequencies of the tremor spectrum.