Thomas Hales

Musculoskeletal disorders among visual display terminal users in a telecommunications company

The relationship between workplace factors and work-related upper extremity musculoskeletal disorders (UE disorders) was assessed in a cross-sectional study of 533 telecommunication employees utilizing video display terminals (VDTs). Cases of UE disorders were defined using symptom questionnaires and physical examinations. Data on demographics, individual factors (medical conditions and recreational activities), work organization and practices, and psychosocial aspects of work, including electronic performance monitoring (EPM), were obtained by questionnaire. Associations between workplace factors and UE disorders were assessed by multiple logistic models generated for each of the four UE areas (neck, shoulder, elbow, hand/wrists). One-hundred and eleven (22%) participants met our case definition for UE disorders. Probable tendon-related disorders were the most common (15% of participants). Probable nerve entrapment syndromes were found in 4% of participants. The hand/wrist was the area most affected, 12% of participants. The following variables had associations in the final models (p < 0.05) with at least one of the four UE disorders, although the strength of these associations were modest. Non-white race, a diagnosis of a thyroid condition (self-reported) use of bifocals at work, and seven psychosocial variables (fear of being replaced by computers, increasing work pressure, surges in workload, routine work lacking decision-making opportunities, high information processing demands, jobs which required a variety of tasks and lack of a production standard) were associated with UE disorders. This study indicates that work-related UE musculoskeletal disorders are relatively common among telecommunication workers who use VDTs, and adds to the evidence that the psychosocial work environment is related to the occurrence of these disorders.

Evaluation of symptom surveys for occupational musculoskeletal disorders

Symptom surveys have been used extensively as part of workplace ergonomic screening programs and epidemiologic assessments of musculoskeletal disorders in groups of workers. This paper examines the reliability and validity of two musculoskeletal symptom surveys, the Nordic Musculoskeletal Questionnaire (NMQ) and a survey used in conjunction with epidemiologic assessments by the National Institute for Occupational Safety and Health (NIOSH). Journal articles assessing the validity and reliability of the NMQ were reviewed. A retrospective assessment combining two NIOSH cohorts with a total of 852 workers assessed the reliability and validity of that survey. Reliability was assessed through test-retest methods and interitem correlations between similar questions. Validity was assessed by comparison with results from physical examination assessments of workers and self-reports of workers seeking medical care. Both reliability and validity were found to be acceptable for the purposes of workplace ergonomics programs. Implications for use of these surveys for prevention and treatment outcomes research are discussed.

Mortality and cancer incidence in a pooled cohort of US firefighters from San Francisco, Chicago and Philadelphia (1950-2009)

Objectives To examine mortality patterns and cancer incidence in a pooled cohort of 29 993 US career firefighters employed since 1950 and followed through 2009. Methods Mortality and cancer incidence were evaluated by life table methods with the US population referent. Standardised mortality (SMR) and incidence (SIR) ratios were determined for 92 causes of death and 41 cancer incidence groupings. Analyses focused on 15 outcomes of a priori interest. Sensitivity analyses were conducted to examine the potential for significant bias. Results Person-years at risk totalled 858 938 and 403 152 for mortality and incidence analyses, respectively. All-cause mortality was at expectation (SMR=0.99, 95% CI 0.97 to 1.01, n=12 028). There was excess cancer mortality (SMR=1.14, 95% CI 1.10 to 1.18, n=3285) and incidence (SIR=1.09, 95% CI 1.06 to 1.12, n=4461) comprised mainly of digestive (SMR=1.26, 95% CI 1.18 to 1.34, n=928; SIR=1.17, 95% CI 1.10 to 1.25, n=930) and respiratory (SMR=1.10, 95% CI 1.04 to 1.17, n=1096; SIR=1.16, 95% CI 1.08 to 1.24, n=813) cancers. Consistent with previous reports, modest elevations were observed in several solid cancers; however, evidence of excess lymphatic or haematopoietic cancers was lacking. This study is the first to report excess malignant mesothelioma (SMR=2.00, 95% CI 1.03 to 3.49, n=12; SIR=2.29, 95% CI 1.60 to 3.19, n=35) among US firefighters. Results appeared robust under differing assumptions and analytic techniques. Conclusions Our results provide evidence of a relation between firefighting and cancer. The new finding of excess malignant mesothelioma is noteworthy, given that asbestos exposure is a known hazard of firefighting.

Exposure–response relationships for select cancer and non-cancer health outcomes in a cohort of US firefighters from San Francisco, Chicago and Philadelphia (1950–2009)

Objectives To examine exposure–response relationships between surrogates of firefighting exposure and select outcomes among previously studied US career firefighters. Methods Eight cancer and four non-cancer outcomes were examined using conditional logistic regression. Incidence density sampling was used to match each case to 200 controls on attained age. Days accrued in firefighting assignments (exposed-days), run totals (fire-runs) and run times (fire-hours) were used as exposure surrogates. HRs comparing 75th and 25th centiles of lagged cumulative exposures were calculated using loglinear, linear, log-quadratic, power and restricted cubic spline general relative risk models. Piecewise constant models were used to examine risk differences by time since exposure, age at exposure and calendar period. Results Among 19 309 male firefighters eligible for the study, there were 1333 cancer deaths and 2609 cancer incidence cases. Significant positive associations between fire-hours and lung cancer mortality and incidence were evident. A similar relation between leukaemia mortality and fire-runs was also found. The lung cancer associations were nearly linear in cumulative exposure, while the association with leukaemia mortality was attenuated at higher exposure levels and greater for recent exposures. Significant negative associations were evident for the exposure surrogates and colorectal and prostate cancers, suggesting a healthy worker survivor effect possibly enhanced by medical screening. Conclusions Lung cancer and leukaemia mortality risks were modestly increasing with firefighter exposures. These findings add to evidence of a causal association between firefighting and cancer. Nevertheless, small effects merit cautious interpretation. We plan to continue to follow the occurrence of disease and injury in this cohort.

Blood-Borne Pathogens among Firefighters andEmergency Medical Technicians

Objective. Firefighters andemergency medical services (EMS) personnel have the potential for occupational exposures to blood, which increases their risk for occupational blood-borne infection. To address this concern, the authors conducted a literature review of occupational blood exposures, the seroprevalence of blood-borne pathogens among these workers, andthe seroprevalence of blood-borne pathogens among the patients they serve. Methods. A MEDLINE search was conducted, andall identified articles that described surveys of exposures to blood or surveillance of blood-borne infections among firefighters and/or emergency medical technicians (EMTs) in the United States were reviewed. For hepatitis B, only seroprevalence surveys conducted after the 1992 requirement by the Bloodborne Pathogens Standard to offer vaccination to potentially exposed employees were included.Results. From these data, the expected number of annual occupational hapatitis C virus seroconversions was estimated to be between 5.8 and118.9 per 100,000 employee-years for EMT–paramedics, between 3.4 and33.7 per 100,000 for firefighter–EMTs, andup to 3.6 per 100,000 for firefighters (non-EMT). Conclusions.This review suggests there are a limited number of studies addressing this issue, andthese studies have numerous limitations. Despite the expected occupational seroconversions andrecognizing the limitations in drawing conclusions from these studies, it appears that firefighters andEMS personnel do not have an elevated seroprevalence of hepatitis C virus compared with the general population. Improved exposure surveillance programs would clarify exposure risks andidentify potential interventions for firefighters andEMS personnel.

Exposures and health effects: An evaluation of workers at a sodium azide production plant

Sodium azide is the principal gas-generating agent used to inflate automobile supplemental restraint systems, more commonly called airbags. Although sodium azide is known to affect the cardiovascular system by causing peripheral vasodilation, there is no published literature describing occupational exposures to sodium azide in the rapidly growing automobile airbag industry. In 1994-1995, the National Institute for Occupational Safety and Health (NIOSH) conducted a cross-sectional study of health complaints reported by sodium azide production workers at the only continuous sodium azide production facility in the United States. The NIOSH evaluation consisted of a plant industrial hygiene survey, a symptom questionnaire, ambulatory blood pressure monitoring, and blood azide analysis. Personal breathing zone air monitoring revealed exposures to sodium azide and hydrazoic acid (a reactant product) at levels greater than the NIOSH Recommended Exposure Limits (RELs). In some cases, exposures exceeded the REL despite the use of air-supplied respirators. The questionnaire revealed that most workers reported headache (10 of 11 [91%]), episodes of low blood pressure (9 of 11 [82%]), and palpitations (8 of 11 [73%]) occurring in the production areas within the 6 months preceding the study. Mild headache (4 of 11 [36%]) was the only symptom reported during our 24-hr medical survey. Ambulatory blood pressure monitoring revealed one asymptomatic employee with a drop in blood pressure (defined as a drop in systolic [at least 20 mm Hg] and diastolic [at least 10 mm Hg] blood pressure) during a period of exposure to sodium azide at a level five times the NIOSH REL. Improvements in plant engineering controls, increased attention to employee hygiene practices, and a more comprehensive respiratory protection program were recommendations made by NIOSH to reduce exposures at the plant. All facilities handling sodium azide should be aware of the potential toxicity of sodium azide and hydrazoic acid.

The Magnitude, Science Base, and Solutions for One of the Largest Occupational Health Problems in the United States:

The surveillance data on work-related musculoskeletal problems clearly indicate that they are one of the largest occupational health problems in the United States. Some MSDs have specific diagnostic criteria and clear pathological mechanisms (e.g., carpal tunnel syndrome). Others are defined primarily by the location of pain and have a more variable or less clearly defined pathology (e.g., back disorders). MSDs represent a wide range of disorders, which can differ in severity from mild periodic conditions to those that are severe, chronic, and debilitating. While some of these disorders, such as low back pain, are common in the general population, NIOSH research has consistently found that the rates of these disorders are higher in heavily exposed workers, such as those in meatpacking, grocery-store checking, newspaper editing, and warehousing, compared to those with lower exposure.