Occupational injuries among aides and nurses in acute care

BACKGROUND

Occupational injuries are common among nursing personnel. Most epidemiologic research on nursing aides comes from long-term care settings. Reports from acute care settings often combine data on nurses and aides even though their job requirements and personal characteristics are quite different. Our objective was to assess risk of work-related injuries in an acute care setting while contrasting injuries of aides and nurses.

METHODS

A retrospective cohort of aides (n = 1,689) and nurses (n = 5,082) working in acute care at a large healthcare system between 1997 and 2004 were identified via personnel records. Workers' compensation filings were used to ascertain occupational injuries. Poisson regression was used to estimate rate ratios (RR) and 95% confidence intervals (95% CI).

RESULTS

Aides had higher overall injury rates than nurses for no-lost work time (RR = 1.2, 95% CI: 1.1-1.3) and lost work time (RR = 2.8, 95% CI: 2.1-3.8) injuries. The risk of an injury due to lifting was greater among aides compared to nurses for both non-lost work time and lost work time injuries. Injury rates among aides were particularly high in rehabilitation and orthopedics units. Most of the injuries requiring time away from work for both groups were related to the process of delivering direct patient care.

CONCLUSIONS

Our findings illustrate the importance of evaluating work-related injuries separately for aides and nurses, given differences in injury risk profiles and injury outcomes. It is particularly important that occupational safety needs of aides be addressed as this occupation experiences significant job growth.

Use of protective equipment in a cohort of rugby players

PURPOSE

To describe the level of usage of protective devices and equipment in a cohort of New Zealand rugby players.

METHODS

Male and female players (N = 327) from a range of competitive grades were followed over the course of the season. Participants were interviewed weekly about their participation in rugby and use of protective equipment. The main outcome measure was percentage of all player-weeks of follow-up for which each equipment item was used.

RESULTS

Mouthguards, the most commonly used equipment item, were worn for 64.9% of player-weeks. Mouthguard usage ranged from 55.0% of player-weeks in Schoolgirls grade to 72.9% of player-weeks in Senior A competition. The next most common item was taping of body joints (23.7% of player-weeks). The sites most commonly taped were the ankle, knee, and hand. Overall usage for the other protective equipment items studied (shin guards, padded headgear, head tape, support sleeves, and grease) was below 15%. In general, forwards had higher usage of protective equipment than backs, and male players had higher usage than female players. The most common self-reported reasons for using protective equipment were to prevent injury and because of a past injury. Players exhibited considerable week-to-week variation in their usage of protective equipment.

CONCLUSIONS

In general, equipment usage was highest in those at greatest risk of injury, namely, forwards, male players, and the senior grades. The high voluntary use of mouthguards is encouraging and indicative of a base of player support for their role in this sport.

Housework, paid work and psychiatric symptoms

OBJECTIVE

To evaluate the hypothesis that work burden, the simultaneous engagement in paid work and unpaid family housework, is a potential risk factor for psychiatric symptoms among women.

METHODS

A cross-sectional study was carried out with 460 women randomly selected from a poor area of the city of Salvador, Brazil. Women between 18 to 70 years old, who reported having a paid occupation or were involved in unpaid domestic activities for their families, were eligible. Work burden-related variables were defined as: a) double work shift, i.e., simultaneous engagement in a paid job plus unpaid housework; and b) daily working time. Psychiatric symptoms were collected through a validated questionnaire, the QMPA.

RESULTS

Positive, statistically significant associations between high (>7 symptoms) QMPA scores and either double work shift (prevalence ratio - PR=2.04, 95% confidence interval - CI: 1.16, 2.29) or more than 10 hours of daily work time (PR=2.29, 95% CI: 1.96, 3.43) were found after adjustment for age, marital status and number of pre-school children.

CONCLUSIONS

Major correlates of high QMPA scores are work burden variables. Being married or having pre-school children are also associated with high QMPA scores only when associated with work burden.

Killed on the clock: a population-based study of workplace homicide, 1977-1991

BACKGROUND

This paper describes the epidemiology of workplace homicides in North Carolina, with emphasis on the circumstances.

METHODS

Workplace homicide victims were identified by and data were abstracted from the North Carolina medical examiner system.

RESULTS

Workplace homicide rates are highest for men, older and self-employed workers, minorities and specific occupations, especially taxi drivers. Robberies, mostly in retail settings, accounted for half of the cases, while 20% were known to involve disputes, the contexts of which differed by sex. Women were most likely to be killed by estranged partners.

CONCLUSIONS

Preventive strategies need to address the specific contexts in which workplace homicide occurs, such as retail and taxi robberies, and law enforcement officers interacting with suspects. A workplace response to domestic violence is also needed. Other areas for future research and intervention include environmental modifications, employee screening and training, and identifying more inclusive occupational data sources.

Uncertainty in the relation between exposure to magnetic fields and brain cancer due to assessment and assignment of exposure and analytical methods in dose-response modeling

Incomplete scientific knowledge ensures that, in every study, uncertainty will enter the processes of exposure estimation and exposure-response modeling. In the light of the heated debate about the health effects of magnetic fields resulting from power production and usage, we undertook a sensitivity analysis to evaluate uncertainty related to key decisions in a previous study of brain cancer and occupational exposure to magnetic fields. The findings appeared to be relatively insensitive to most variations in the methods of exposure assessment, exposure assignment, and data analysis. The results can be visualized by defining bands of uncertainty about a best-bet estimate of the association based on our original study. These bands of methodological uncertainties were similar in magnitude to the conventional 95% confidence interval, but they provide a measure of the potential range of systematic bias in the results, rather than reflecting statistical variability alone. The methodology employed here can be applied to other studies, and other researchers are encouraged to conduct sensitivity analysis in order to estimate methodological uncertainty as an alternative to statistical confidence intervals.

Magnetic field exposure and neurodegenerative disease mortality among electric utility workers

Several recent reports indicate that occupational exposure to electric and magnetic fields may be associated with increased risk of neurodegenerative diseases. To address that hypothesis, we analyzed data from a cohort study of electric utility workers. We examined exposure to magnetic fields, assessed as duration of work in exposed jobs and through an index of cumulative exposure based on magnetic field measurements, in relation to mortality from Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, considering both underlying and all mentioned causes of death. Adjusted mortality rate ratios based on Poisson regression models indicate no association between magnetic fields and Parkinson's disease and little support for an association with Alzheimer's disease mortality. Mortality from amyotrophic lateral sclerosis was positively associated with duration of work in exposed jobs [rate ratio = 2.0, 95% confidence interval (CI)= 0.7-6.0; and rate ratio = 3.1, 95% CI = 1.0-9.8, based on underlying cause for 5 - < 20 years and > or = 20 years vs < 5 years, respectively], as well as with cumulative magnetic field exposure with a > or = 20-year lag (rate ratio = 2.3, 95% CI = 0.8-6.6; and rate ratio = 3.0, 95% CI = 1.0-9.2, for exposure in the middle and upper intervals relative to the lowest interval, respectively).

Electrical occupations and neurodegenerative disease: analysis of U.S. mortality data

Investigators have hypothesized that occupations involving electric and magnetic field exposure are associated with a variety of health problems, including neurological disease. The authors conducted a case-control study, and they used U.S. death certificates with occupational coding to compare male cases of Alzheimer's disease (n = 256), Parkinson's disease (n = 168), and amyotrophic lateral sclerosis (n = 114) with controls matched for age and calendar time. The authors selected controls in a 3:1 ratio to cases from persons who died of causes other than leukemia, brain cancer, and breast cancer. Overall associations with electrical occupations were modest (i.e., adjusted odds ratios of 1.2, 1.1, and 1.3 for Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, respectively). Individual electrical occupations were associated more strongly with disease than overall electrical occupations, particularly amyotrophic lateral sclerosis, for which relative risks ranged from 2 to 5 across several job categories. The largest associations with all three diseases occurred for power plant operators.

Surveillance of work-related musculoskeletal injuries among union carpenters

Combined data sources, including union administrative records and workers' compensation claims, were used to construct event histories for a dynamic cohort of union carpenters from Washington State during the period 1989-1992. Person-time at risk and the events of interest were stratified by age, sex, time in the union, and predominant type of carpentry work. Poisson regression techniques were used to identify subgroups at greatest risk of filing claims for a variety of musculoskeletal disorders defined by ANSI codes for body part injured and injury nature. Distinguishing different kinds of musculoskeletal disorders, even crudely with ANSI codes, led to different conclusions about the effects of the explanatory variables. Among older workers, the rates of fractures of the foot were higher, while rates of contusions of the hand and foot were lower. Women had higher rates of sprain/strains and nerve conditions of the wrist/forearm. Higher rates of injuries to the axial skeleton were seen among carpenters who did predominantly light commercial and drywall work, while piledrivers had lower rates of these injuries. Drywall workers had higher rates of sprains to the ankle/lower leg. Workers who were members of the union as long as four years had lower risks for the vast majority of musculoskeletal disorders studied. Similar patterns were seen for more serious claims that resulted in paid lost time from work.

Fatal Occupational Injuries in the Forestry and Logging Industry in North Carolina, 1977-1991

Fatal occupational injuries in the forestry and logging industry and occupation in the state of North Carolina from January 1, 1977, to December 31, 1991, were analyzed. Data were obtained through the North Carolina medical examiners system. The analysis was performed for the whole state as well as for the four forestry regions into which the state is divided. A total of 125 deaths happened over the study period. All were men, and the majority (60%) were white, with a mean age of 43 years. The crude fatality rate for the overall study period was 2.2 deaths per 1,000 person-years, with age-specific rates increasing with age. The Piedmont region had the highest proportion of cases (31.2%), while the Mountain region accounted for the highest overall rate (22.7 per 1,000 person-years). For all the forestry regions, the leading means of injury was found to be falling objects.

Sensitivity of the relation between cumulative magnetic field exposure and brain cancer mortality to choice of monitoring data grouping scheme

We examined the effectiveness of alternative grouping strategies with respect to cumulative exposure to magnetic fields and brain cancer mortality among electric utility workers. We applied a statistically optimal job-exposure matrix to calculate cumulative exposure over full work histories. We studied the sensitivity of the exposure-disease relation by assigning an array of different quantitative exposure estimates based on six schemes for grouping exposure measurements. The quantitative relation between cumulative magnetic field exposure and brain cancer mortality appeared to be sensitive to the choice of grouping scheme, with the optimized grouping scheme indicating stronger relations than standard schemes.

Fatal occupational injuries in a southern state

Fatal occupational injuries were studied using data from medical examiners' reports in North Carolina for the years 1977-1991. Cases were defined as deaths due to accidents or homicide at the workplace, and populations at risk were estimated from the 1980 and 1990 US Censuses. Mortality rate ratios and proportionate mortality ratios were used as measures of association, and the population attributable risk percentage was used as an indicator of the burden of injury. Standard weights for direct age-adjustment of rates were obtained from the total state workforce. There were 2,524 eligible deaths-83 percent from unintentional traumatic injuries, 14 percent from homicide, and the remainder from other causes. This report focuses on unintentional trauma deaths, which were strongly associated with the wood production, fishing, and transportation industries. Elderly, African-American, and self-employed workers had higher fatality rates than members of other groups. Among male workers, motor vehicle crashes were the principal cause of death on the job, followed by falling objects, machinery, and falls. The industries contributing the largest proportions of these deaths were construction, trucking, agriculture, and logging (population attributable risk percentages were 16.8%, 8.8%, 7.9%, and 6.9%, respectively). The fatality patterns of female workers were different: Numbers of deaths from homicide and unintentional trauma were equal, and 27% of the latter deaths occurred in one catastrophic fire. Decentralized and rural industries were the most hazardous, but many deaths were outside the current jurisdiction of occupational safety and health agencies. These patterns suggest that greater scrutiny of such industries, through both research and intervention, is warranted.

Ozone, suspended particulates, and daily mortality in Mexico City

To investigate acute, irreversible effects of exposure to ozone and other air pollutants, the authors examined daily death counts in relation to air pollution levels in Mexico City during 1990-1992. When considered singly in Poisson regression models accounting for periodic effects, the rate ratio for total mortality associated with a 100-ppb increment in 1-hour maximum ozone concentration was 1.024 (95% confidence interval (CI) 1.011-1.039). Measures of average ozone concentration were somewhat more strongly related to mortality. The rate ratio was 1.024 (95% CI 0.984-1.062) per 100 ppb for sulfur dioxide and 1.050 (95% CI 1.030-1.067) per 100 micrograms/m3 for total suspended particulates. However, when all three pollutants were considered simultaneously, only total suspended particulates remained associated with mortality, indicating excess mortality of 6% per 100 micrograms/m3 (rate ratio = 1.058, 95% CI 1.033-1.083), consistent with observations in other cities in the United States and Europe. The authors found no independent effect of ozone, but it is difficult to attribute observed effects to a single pollutant in light of the complexity and variability of the mixture to which people are exposed. Nevertheless, particulate matter may be a useful indicator of the risk associated with ambient air pollution.

Ozone exposure and daily mortality in Mexico City: a time-series analysis

Daily death counts in Mexico City were examined in relation to ambient ozone levels during 1990-1992 for the purpose of investigating the acute, irreversible effects of air pollution, with emphasis on ozone exposure. Air pollution data were obtained from nine monitoring stations operated by the Departamento del Distrito Federal. Mortality data were provided by the Instituto Nacional de Estadística, Geografía, e Informática. Increases in numbers of deaths were positively associated with elevated air pollution levels on the same day and on the previous day. The magnitude of the increases was small but statistically significant, after Poisson regression models were used to adjust for temperature and long-term trends. In models using data for a single pollutant, the "crude" ratio for total mortality associated with an increase of 100 parts per billion (ppb)* in one-hour maximum ozone concentration was 1.029 (95% CI 1.015, 1.044). A moving average of ozone showed a stronger association (rate ratio [RR] = 1.048, 95% CI 1.025, 1.070), and excess mortality (an increase in the number of deaths, relative to the average on days with low pollution levels) was more evident for persons over 65 years of age. Separate analyses of the effect of elevated ozone for different areas of the city showed similar results, but they were not statistically significant. Other pollutants also were related to mortality. The RR was 1.075 (95% CI 0.984, 1.062) per 100-ppb increase for sulfur dioxide and 1.049 (95% CI 1.030, 1.067) per 100 micrograms/m3 increase in total suspended particulates (TSP) when these pollutants were considered in separate models. However, when all three pollutants were considered simultaneously, only TSP remained associated with mortality, indicating excess mortality of 5% per 100 micrograms/m3 increase [RR = 1.052, 95% CI 1.034, 1.072]. The excess mortality associated with TSP is consistent with that observed in other cities in America and Europe. This study provides some evidence that ozone is associated with all-cause mortality and with mortality among the elderly after controlling for long-term cycles. However, ozone levels exhibited little or no effect on mortality rates when other air pollutants were considered simultaneously. Particulate matter appeared to be an important pollutant; it independently predicted changes in mortality. Nevertheless, because of the complexity and variability of the mixtures to which people are exposed, it is difficult to attribute the observed effects to a single pollutant. The technical feasibility and scientific validity of isolating the effect of single pollutants in such complex mixtures requires further research and careful consideration. Given the large population living in and exposed to ambient air pollution in Mexico City and other metropolises throughout the world, these small but significant associations of mortality with air pollution indices are of public health concern.

Mortality of workers at a nuclear materials production plant at Oak Ridge, Tennessee, 1947-1990

The Y-12 plant at Oak Ridge, Tennessee, produced nuclear materials for the U.S. government's nuclear weapons program beginning in 1943. Workers at Y-12 were exposed to low dose, internal, alpha radiation and external, penetrating radiation, as well as to beryllium, mercury, solvents, and other industrial agents. This paper presents updated results from a long-term mortality study of workers at Y-12 between 1947 and 1974, with follow-up of white men through 1990 and data reported for the first time for women and men of other races. Vital status was determined through searches of the National Death Index and other records, and the workers' mortality was compared to the national population's using standardized mortality ratios (SMRs). Total mortality was low for all Y-12 workers and total cancer mortality was as expected. Among the 6,591 white men, there were 20% more lung cancer deaths than expected (95% confidence interval [CI] 1.04-1.38). Death rates from brain cancer and several lymphopoietic system cancers were also elevated among white men, with SMRs of 1.28 and 1.46. Mortality from cancer of the pancreas, prostate, and kidney was similarly elevated. There was evidence of excess breast cancer among the 1,073 female workers (SMR 1.21, 95% CI 0.60-2.17). Lung cancer mortality among these workers warrants continued surveillance because of the link between internal alpha radiation exposure and this disease, but other agents, notably beryllium, also merit considerations as potential causes of lung cancer. Other cancers and agents should also be investigated as part of a comprehensive study of the health consequences of the production of nuclear weapons.

Assessment and grouping of occupational magnetic field exposure in five electric utility companies

OBJECTIVES

Occupational exposure to 60-Hz magnetic fields was surveyed among randomly selected workers in five electric power companies.

METHODS

The study facilitated the examination of exposure variability and provided the base for a job-exposure matrix linking health outcomes and occupational magnetic field exposures.

RESULTS

Average exposures ranged from 0.11 to 1.50 microT. The differences among the five companies were small, the more urban companies showing somewhat higher averages. The day-to-day component of variance exceeded the within- and between-group components of variance. The final job-exposure matrix consisted of five groups with average exposure levels of 0.12, 0.21, 0.39, 0.62, and 1.27 microT. Given the variance in exposure, even this optimal grouping considerably overlapped.

CONCLUSIONS

The job-exposure matrix used in this study efficiently incorporated the differences in exposure within occupational categories between companies and provided an objective and statistically based method for estimating cumulative magnetic field exposure.

Magnetic field exposure in relation to leukemia and brain cancer mortality among electric utility workers

Reports of leukemia and brain cancer among men in electrical occupations suggest a small increase in risk, but most previous studies have failed to classify magnetic field exposure accurately or to consider potential confounders. The authors conducted an historical cohort mortality study of 138,905 men employed at five large electric power companies in the United States between 1950 and 1986 with at least 6 months of work experience. Exposure was estimated by linking individual work histories to data from 2,842 workshift magnetic field measurements. Mortality follow-up identified 20,733 deaths based on 2,656,436 person-years of experience. Death rates were analyzed in relation to magnetic field exposure history with Poisson regression. Total mortality and cancer mortality rose slightly with increasing magnetic field exposure. Leukemia mortality, however, was not associated with indices of magnetic field exposure except for work as an electrician. Brain cancer mortality was modestly elevated in relation to duration of work in exposed jobs and much more strongly associated with magnetic field exposure indices. Brain cancer risk increased by an estimated factor of 1.94 per microtesla-year of magnetic field exposure in the previous 2-10 years, with a mortality rate ratio of 2.6 in the highest exposure category. In contrast to other studies, these data do not support an association between occupational magnetic field exposure and leukemia but do suggest a link to brain cancer.

Organization and classification of work history data in industry-wide studies: an application to the electric power industry

Industry-based cohort studies require systems for organizing work history data. Although the ultimate goal may be to assess the hazards of specific exposures, classification of the job titles that comprise work histories serves an important descriptive purpose in itself and is often necessary before exposure data can be obtained. A system we have created for organizing jobs in a study of 135,000 workers at five electric power companies highlights conceptual and practical issues in managing work history data for epidemiological studies. Job characteristics including function, location, and authority were used to develop a system of 28 occupational categories. Comprehensibility, flexibility, and efficiency were important criteria in designing the system. Assessment of exposures was an implicit goal; the same categories will define job-exposure matrices for numerous agents. A combination of computer algorithms and expert judgment was used to assign individual job titles to the categories. This system facilitates examining the effects of various agents and controlling for confounding. The 28 categories can be collapsed and regrouped to analyze disease risks in relation to exposures to magnetic fields and other agents; even exposures not previously considered could be brought into the study with this generic system for organizing the electric power industry.

Breast cancer mortality among female electrical workers in the United States

BACKGROUND

Previous epidemiologic studies have suggested that exposure to electric or magnetic fields in occupational and residential environments may cause cancer. Recent experimental findings provide some support for the hypothesis that exposure to extremely low-frequency electromagnetic fields reduces the pineal gland's nocturnal production of the hormone melatonin, thereby increasing susceptibility to sex hormone-related cancers such as breast cancer.

PURPOSE

Our purpose was to assess the evidence that cancer of the female breast might be associated with exposure to extremely low-frequency electromagnetic fields.

METHODS

Records of women who had breast cancer as the underlying cause of their death (ICD-9 174) and control subjects (four per case) were selected from computer files of U.S. mortality data for the years 1985-1989. Women 20 years and older at the time of their death were eligible for inclusion if they were residents of and died in one of the 24 states that provided death certification records with occupation and industry codes to the National Center for Health Statistics for at least 1 year during the study interval. Data from death certificates were used to classify the case and control subjects with regard to potential occupational exposure to electric and magnetic fields. Control subjects were a random sample of women who died of any other underlying cause, excluding leukemia and brain cancer.

RESULTS

The data analysis contrasted 68 women with breast cancer and 199 controls, all with electrical occupations, with 27,814 women with breast cancer and 110,750 controls, all of whom had other occupations. Electrical workers had excess mortality from breast cancer relative to other employed women [odds ratio (OR) = 1.38; 95% confidence interval (CI) = 1.04-1.82]). Adjusted ORs for specific electrical occupations were 1.73 (95% CI = 0.92-3.25) for electrical engineers, 1.28 (95% CI = 0.79-2.07) for electrical technicians, and 2.17 (95% CI = 1.17-4.02) for telephone installers, repairers, and line workers. There was no excess of breast cancer, however, in seven other occupations held more frequently by women and also involving potentially elevated electrical exposures, including telephone operators, data keyers, and computer operators and programmers.

CONCLUSIONS

In light of the limitations inherent in death certification data and the design of this study, any conclusions regarding the hypothesis that exposure to extremely low-frequency electromagnetic fields causes breast cancer among women must be limited. Nevertheless, our findings are broadly consistent with that hypothesis and encourage further investigation with improvements in study design and data quality.

Effect of incomplete exposure assessment on epidemiologic dose-response analyses

OBJECTIVES

When potentially hazardous agents have multiple environmental sources, failure to include all exposure sources can constitute a type of measurement error. In addition, the effects of exposure from one source can also be confounded by exposure to other sources of the same agent. In this study clarification of these concepts is sought, and the direction and magnitude of the resulting bias in epidemiologic measures of association are examined.

METHODS

The bias in dose-response functions when the exposure data omit some sources of the agent was estimated with linear and log-linear models to compute risk differences and risk ratios under different assumptions about the magnitude and correlation of exposures from measured and unmeasured sources.

RESULTS

With unmeasured exposure of constant magnitude, there is no bias when a measure of association of the appropriate form (difference measures for additive dose-response processes, ratios for multiplicative ones) is selected. When the magnitude of unmeasured exposure varies, the results is nondifferential measurement error that can bias observed dose-response relations upward or downward, depending on the pattern of measurement error and the measure of association.

CONCLUSIONS

Failure to measure all sources of exposure to an agent and account for them in the analysis can bias the results of epidemiologic studies. When it is not feasible to measure all exposure sources, the magnitude of bias can be predicted by estimating the distribution of omitted exposures from external data or substudies. Sensitivity analyses are particularly useful for estimating the direction and magnitude of potential bias from incomplete exposure assessment.

Pesticide exposures, cholinesterase depression, and symptoms among North Carolina migrant farmworkers

OBJECTIVES

We conducted a clinic-based study of erythrocyte cholinesterase levels, pesticide exposures, and health effects among farmworkers and nonfarmworkers to determine risks for exposure and associated morbidity.

METHODS

Two hundred two farmworkers and 42 nonfarmworkers were recruited sequentially at two community health centers. Erythrocyte cholinesterase levels were measured colorimetrically. Questionnaires obtained data on demographics, occupational history, exposures, and symptoms.

RESULTS

Cholinesterase levels were significantly lower among farmworkers (30.28 U/g hemoglobin) than among nonfarmworkers (32.3 U/g hemoglobin). Twelve percent of farmworkers, but no nonfarmworkers, had very low levels. Farmworkers applying pesticides also had lower cholinesterase levels. One half of farmworkers reported being sprayed by pesticides and working in fields with an obvious chemical smell. Of reported symptoms, only diarrhea was associated with cholinesterase levels. Reported exposures, however, were strongly associated with symptoms.

CONCLUSIONS

Farmworkers reported many pesticide exposures that violate state and federal regulations. Farmworkers had cholinesterase levels significantly lower than those of nonfarmworkers, although only spraying pesticides was associated with very low levels.

Correlations among indices of electric and magnetic field exposure in electric utility workers

Power-frequency electric and magnetic fields are known to exhibit marked temporal variation, yet in the absence of clear biological indications, the most appropriate summary indices for use in epidemiologic studies are unknown. In order to assess the statistical patterns among candidate indices, data on 4383 worker-days for magnetic fields and 2082 worker-days for electric fields collected for the Electric and Magnetic Field Project for Electric Utilities using the EMDEX meter [Bracken (1990): Palo Alto, CA: Electric Power Research Institute] were analyzed. We examined correlations at the individual and job title group levels among indices of exposure to both electric and magnetic fields, including the arithmetic mean, geometric mean, median, 20th and 90th percentiles, time above lower cutoffs of 20 V/m and 0.2 microT, and time above higher cutoffs of 100 V/m and 2.0 microT. For both electric and magnetic fields, the arithmetic mean was highly correlated with the 90th percentile; moderately correlated with the geometric mean, median, and lower and higher cutoff scores; and weakly correlated with the 20th percentile. Electric and magnetic field indices were generally weakly correlated with one another. Rank-order correlation coefficients were consistently greater than product-moment correlation coefficients. Job title group summary scores showed higher correlations among electric field indices and magnetic field indices and between electric and magnetic field indices than was found for individual worker-days, with only the 20th percentile clearly independent of the others. These results suggest that individuals' exposures are adequately characterized by a measure of central tendency for electric and magnetic fields, such as the arithmetic or geometric mean, and an indicator of a lower threshold or cutoff for each field type, such as the 20th percentile or proportion of time above 20 V/m or 0.2 microT. A single measure of central tendency for each type of field appears to be adequate when exposures are assessed at the job title level.

Occupation, industry, and fatal motor vehicle crashes in 20 states, 1986-1987

BACKGROUND

Motor vehicles are a leading cause of injury on and off the job.

METHODS

To describe the occurrence of fatal motor vehicle crashes in the working-age population, a case-control study was conducted among persons 15-64 years old who died in 1986 or 1987 in any of 20 states reporting death certificate occupational data to the National Center for Health Statistics. Cases were occupants of motor vehicles (excluding motorcycles) who died of injuries sustained in a crash (E810-E825, 9th revision International Classification of Diseases), and controls died of any other cause.

RESULTS

Transportation-related occupations had more than the expected number of deaths for men (odds ratio = 1.6, 95% confidence interval = 1.4-1.9) and women (odds ratio = 2.1, 95% confidence interval = 1.0-4.5), as did managerial occupations (odds ratio = 1.3 and 1.7, 95% confidence interval = 1.1-1.5 and 1.3-2.2 for men and women, respectively). Men in mining and oil drilling occupations and the wholesale trade industry also had excess crash deaths. Among women, additional excesses were observed among professional specialists and in several groups with few deaths, including agriculture, construction, and the military, whereas homemakers had markedly fewer vehicle crash deaths than expected.

CONCLUSIONS

These findings encourage further investigation of this important safety hazard, but also call attention to a need for more detailed studies and improved data.

Childhood cancer mortality and radon concentration in drinking water in North Carolina

We explored the association between groundwater radon levels and childhood cancer mortality in North Carolina. Using data from two state-wide surveys of public drinking water supplies, counties were ranked according to average groundwater radon concentration. Age and sex-adjusted 1950-79 cancer death rates among children under age 15 were calculated for counties with high, medium, and low radon levels. Overall cancer mortality was increased in counties with medium and high radon levels. The strongest association was for the leukaemias, but risks were also suggested for other sites. These associations could be due to confounding or other biases, but the findings are consistent with other recent reports.

Occupation and leukemia mortality among men in 16 states: 1985-1987

The relationship between leukemia and occupation was investigated in a case-control study using death certificates of 5,147 men who died of leukemia (ICD-9 codes 204-208) and 51,470 who died of other causes in 16 U.S. states from 1985 to 1987. Of six occupational activities identified previously as potentially increasing the risk of leukemia, only petroleum refining and rubber manufacturing had excess deaths for all leukemias combined (odds ratios (ORs) = 1.3, 95% confidence intervals (CI) = 0.6-2.8 and 0.9-1.8, respectively). Meat workers and wood workers had elevated mortality from acute lymphocytic leukemia (OR = 2.2, 95% CI = 0.7-7.0 and OR = 1.3, 95% CI = 0.8-2.2, respectively). There was no leukemia excess among farmers or auto mechanics. A survey of 43 other occupational groups indicated a widespread excess of leukemia among white collar occupations, primarily managers and professionals, but none among blue collar workers. This pattern was most pronounced for men under 65 years of age, and existed for all leukemia subtypes and among both blacks and whites. Despite the lack of specific exposure information and other limitations of death certificate data, these results encourage further examination of occupational causes of leukemia.

Micronuclei in epithelial cells from sputum of uranium workers

The cytogenetic effects of exposure to radon progeny and cigarette smoke were assessed with the exfoliated-cell micronucleus assay among 99 uranium workers. Cells with micronuclei were determined in one sputum specimen from each worker. Exposure to radon progeny and smoking habits were classified from interview data collected at the same time as the sputum specimens. Underground miners were considered exposed to radon progeny, and the other workers were considered unexposed. Neither radon progeny exposure nor cigarette smoking had any appreciable effect on the prevalence of cells with micronuclei; the crude prevalence ratios for the two groups were 1.0 (95% confidence interval 0.7-1.4) and 0.9 (95% confidence interval 0.6-1.3), respectively. The effects of radon and smoking were not confounded by each other or by age, nor were they synergistic. These findings cast doubt on the use of sputum-based micronucleus assay in epidemiologic studies of other populations exposed to occupational or environmental lung carcinogens.

Mortality from brain cancer and leukaemia among electrical workers

The relation of brain cancer and mortality from leukaemia to electrical occupations was investigated in a case-control study based on all deaths in 1985 and 1986 in the 16 states in the United States that report occupational data from death certificates to the national vital statistics registry. The case series comprised all 2173 men who died of primary brain cancer (International Classification of Diseases-9 ((ICD-9) code 191) and all 3400 who died of leukaemia (ICD-9 codes 204-208). Each was matched with 10 controls who died of other causes in the same year. Men employed in any electrical occupation had age race adjusted odds ratios (ORs) of 1.4 (95% confidence interval (CI) 1.1-1.7) for brain cancer and 1.0 (95% CI 0.8-1.2) for leukaemia, compared with men in all other occupations. Brain cancer odds ratios were larger for electrical engineers and technicians (OR 2.7, 95% CI 2.1-3.4), telephone workers (OR 1.6, 95% CI 1.1-2.4), electric power workers (OR 1.7, 95% CI 1.1-2.7), and electrical workers in manufacturing industries (OR 2.1, 95% CI 1.3-3.4). There was some evidence of excess leukaemia among the same groups (ORs of 1.1-1.5) despite absence of an association for all electrical workers. The excess of deaths from brain cancer was concentrated among men aged 65 or older, whereas leukaemia was associated with electrical work only among younger decedents and those with acute lymphocytic leukaemia. These results from a large and geographically diverse population corroborate reports of increased mortality from brain cancer among electrical workers, but gives only limited support to suggestions of excess deaths from leukaemia.

Relationship of mortality, occupation, and pulmonary diffusing capacity to pleural thickening in the First National Health and Nutrition Examination Survey

We studied the relationship of pleural thickening consistent with asbestos exposure to mortality, career employment in asbestos-related jobs, and pulmonary diffusing capacity among participants in the first National Health and Nutrition Examination Survey. Three "B" readers examined chest X-rays to identify 59 individuals with such pleural abnormalities. From 1975 to 1984, the all-cause mortality rate ratio (RR) comparing males with and without occupational pleural thickening was 1.3 (95% C.I. 0.8-2.2). For lung cancer, the mortality RR for males was 3.0 (95% C.I. 1.0-9.1). Career asbestos work was not associated with occupational pleural thickening among men, probably because some with the condition had only short-term exposure to asbestos. Pulmonary diffusing capacity was lower in those with occupational pleural thickening, taking smoking into account. These results suggest that individuals in the general population who have occupational pleural thickening are at risk for some of the health consequences of asbestos work, including lung cancer, even if they were not career asbestos workers.

Radon-222 concentration in groundwater and cancer mortality in North Carolina

In a geographic correlation study, we explored the possibility that residential exposure to radon in groundwater may be related to cancers other than lung cancer. Measurements of radon in groundwater and 1978-1982 cancer mortality data from North Carolina, USA were used to investigate this relationship. Counties were categorized in two levels of radon exposure according to measured radon concentration and geology. In the lower exposure group (unexposed) county mean radon concentrations ranged from 0-228 pCi/l (0-8436 Bq/m3), and in the upper group (potentially exposed) the range of county average concentrations was 229-10892 pCi/l (8473-403004 Bq/m3) (median 1375 pCi/l (50875 Bq/m3)). Adjusted mortality ratios and 95% confidence intervals were calculated for selected cancers, including leukemias, gastro-intestinal tract cancers, and respiratory tract cancers excluding lung cancer. In contrast to other ecologic studies, we found no consistent association between radon level and cancer mortality.

Predicting the occurrence of radon-222 in groundwater supplies

The intent of this study was to develop an understanding of some of the factors that affect the concentration ol radon-222 ((222)Rn) in drinking water supplies derived from groundwater, with specific application to North Carolina. Data for this investigation were collected on a sample of 96 North Carolina public water supply wells. Water samples were collected and analyzed for(222)Rn content. Data on site geology and well characteristics (discharge, specific capacity, depth, and casing length) were obtained from existing sources. From a statistical examination of the data collected in this study, we conclude that there is a distinct and statistically significant difference in the mean(222)Rn concentrations of groundwater associated with different types of rocks. The data, however, also indicate that there is a great degree of variability in the(222)Rn concentrations of samples drawn from any giver rock type. The situation is made slightly better by introducing a second variable given as the geologic region of a water supply. A fairly surprising finding of this study is the relative insignificance of discharge, specific capacity, depth, and casing length of wells as predictors of(222)Rn concentration. The present study indicates that use of these variables as predictors does not significantly improve the likelihood of locating water supplies with elevatec(222)Rn concentrations.