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Many of the job processes being performed today in ship construction, repair and recycling yards do not differ significantly from those same processes as performed fifty years ago. The complexity of vessels may have increased dramatically in the past fifty years but many of the job processes have not kept pace with changes in tech-nology. Due in part to the mismatch of technology between work processes and product design, researchers at the National Institute for Occupational Safety and Health (NIOSH), in collaboration with the National Shipbuilding Research Program Advanced Shipbuilding Enterprise (NSRP ASE) and the Maritime Advisory Committee for Occupational Safety and Health (MACOSH), have conducted a series of ergonomic analyses of work processes at a number of domestic shipyards. These analyses have identified specific work processes within the shipyards that have resulted in numerous, severe, or costly musculoskeletal injuries to the shipyard work-force. The mitigation of the occupational risk factors associated with these processes was the focus of targeted ergonomic interventions.

One common framework for describing the evaluation and assessment of hazards in the workplace includes the four steps of hazard identification, exposure assessment, exposure-response modeling, and risk characterization (NAS, 1983). We discuss hazards for occupational injury and illness in light of this framework, and we contrast the evaluation of injury hazards with the evaluation of illness hazards. In particular, the nature of the hazards, typical exposure patterns, quantification of exposure, and the attribution of outcome to exposure are discussed. Finally, we discuss the management of occupational illness and injury hazards and issues encountered when evaluating efforts designed to mitigate the effects of occupational hazards.

OBJECTIVES: An updated version of a national surveillance system of traumatic occupational fatalities was used to explore adjusted and unadjusted trends in rates of fatal injury. METHODS: Data from the national traumatic occupational fatalities surveillance system were combined with data on employment from the United States Bureau of Labor Statistics. Poisson regression was then used to examine trends in rates of occupational fatality injuries while controlling for demographic and workplace characteristics. RESULTS: Adjusted annual changes in rates of fatal injuries ranged from a decline of 6.2% for workers in technical and administrative support occupations--for example, health, science, and engineering technicians, pilots, computer programmers--to an increase of 1.6% in machine operators, assemblers, and inspectors. For industries, annual changes ranged from a decline of 5.3% for workers in public administration--for example, justice, public order, and safety workers--to an increase of 2.6% for workers in the wholesale trade. By comparison, the annual decline over all industries and occupations was 3.1%. In many industries and occupations, an effect modification of annual trends by the age of the worker was also found with the oldest workers experiencing either no decline or a significant increase in rates of fatal injuries. CONCLUSIONS: This general pattern of decline, adjusted for the effects of demographic characteristics of the worker population, is encouraging; however, increases in rates of fatal injuries found in particular industries and occupations, suggest appropriate targets for increased injury prevention efforts.

Injury surveillance data serves as the foundation of many safety studies. These studies frequently gather information on the number of injuries along with the number of employees at risk of injury in each of several strata where the strata are defined in terms of a series of important predictor variables. It is common for analyses of such data to examine injury rates separately for each predictor variable. The analysis of the crude or unadjusted injury rates give an overall indication of injury rate changes as a function of a particular predictor variable; however, further insights may be gained from analyses using Poisson regression models. Poisson regression models are described as a means of analyzing rates adjusting for one or more predictor variables. In these models, the log rate of injury is expressed as a linear function of predictor variables. The interpretation of model parameters is given along with a presentation of the basic formulation of such models. Testing for trend, evaluation of confounding, and effect modification are illustrated using surveillance data describing occupational fatal injury rates as a function of year (1983–1992), gender and age for White workers employed in agriculture, forestry, or fishing. Data for this analysis were obtained from two sources: the National Traumatic Occupational Fatality (NTOF) database from the National Institute for Occupational Safety and Health provided counts of the fatal injuries, while data from the U.S. Bureau of Labor Statistics (BLS) provided counts on employment. Using an unadjusted trend model, a statistically nonsignificant decline in fatal injury rates over 1983–1992 is observed. Further analysis using Poisson regression revealed an interaction between gender and calendar year with males experiencing a weak, albeit significant, decrease and females experiencing a strong and significant increase.

Associations between environmental factors and work-related health conditions were assessed using regression techniques with environmental and health data for 2435 respondents in 80 office buildings included in the National Institute for Occupational Safety and Health Health Hazard Evaluation program. The health conditions analyzed included two symptom groupings—multiple lower respiratory symptoms and multiple atopic symptoms—and the presence of asthma diagnosed after beginning work in the building. Four categories of environmental variables were included: heating, ventilation, and air conditioning (HVAC) system design; HVAC maintenance; building design; and building maintenance. Female gender and age over 40 years showed increased relative risks (RRs) for each health condition. In regression models adjusted for age and gender, RRs of multiple lower respiratory symptoms were increased for variables in the HVAC design and maintenance categories, with the highest RR for presence of debris inside th...

In the attempt to estimate the average concentration of a particular contaminant during some period of time, a certain proportion of the collected samples is often reported to be below the limit of detection. The statistical terminology for these results is known as censored data, i.e., nonzero values which cannot be measured but are known to be below some threshold. Samples taken over time are assumed to follow a lognormal distribution. Given this assumption, several techniques are presented for estimation of the average concentration from data containing nondetectable values. The techniques proposed include three methods of estimation with a left-censored lognormal distribution: a maximum likelihood statistical method and two methods involving the limit of detection. Each method is evaluated using computer simulation with respect to the bias associated with estimation of the mean and standard deviation. The maximum likelihood method was shown to produce unbiased estimates of both the mean and s...

Engineering is the application of scientific and technical knowledge to solve human problems. Using imagination, judgment, and reasoning to apply science, technology, mathematics, and practical experience, engineers develop the design, production, and operation of useful objects or processes. During the 1940s, engineers dominated the ranks of CDC scientists. In fact, the first CDC director, Assistant Surgeon General Mark Hollis, was an engineer. CDC engineers were involved in malaria control through the elimination of standing water. Eventually the CDC mission expanded to include prevention and control of dengue, typhus, and other communicable diseases. The development of chlorination, water filtration, and sewage treatment were crucial to preventing waterborne illness. Beginning in the 1950s, CDC engineers began their work to improve public health while developing the fields of environmental health, industrial hygiene, and control of air pollution. Engineering disciplines represented at CDC today include biomedical, civil, chemical, electrical, industrial, mechanical, mining, and safety engineering. Most CDC engineers are located in the National Institute for Occupational Safety and Health (NIOSH) and the Agency for Toxic Substances and Disease Registry (ATSDR). Engineering research at CDC has a broad stakeholder base. With the cooperation of industry, labor, trade associations, and other stakeholders and partners, current work includes studies of air contaminants, mining, safety, physical agents, ergonomics, and environmental hazards. Engineering solutions remain a cornerstone of the traditional "hierarchy of controls" approach to reducing public health hazards.

Aerosol instrumentation was used to evaluate air infiltration into tractor cabs that are used to protect the agricultural worker during pesticide applications. Preliminary surveys were conducted on three different manufactured agriculture enclosures. The results of these preliminary surveys indicated that aerosols are entering the cab through leak sources or are being generated inside the cab. These results identified the need for in-depth field evaluations of tractor cabs to identify any leak sources. To evaluate the ability of tractor cabs to reduce operator air contaminant exposure, field evaluations were conducted on two tractor cabs. Specifically, we evaluated: 1) the particle size distribution and the effectiveness of the filter system; and 2) air infiltration into the cab. These evaluations were also conducted to demonstrate the ease and practicality of using optical particle counters to evaluate the ability of cabin filtration systems. Pesticide particle size distribution during an air blast spray operation was also evaluated during the study. The field tests were conducted on a John Deere 7000 series tractor cab (tractor manufacturer's cab) and a Nelson spraycab (retrofit cab). Both cabs were equipped with high efficiency particulate air (HEPA) filter media which were assumed to be 99.97 percent efficient at removing the test aerosol, atmospheric condensation nuclei. Thus, the major source of aerosols inside the cab was assumed to be leakage around filters at the seals. Using a portable dust monitor (PDM), the ratio of the outside to inside aerosol measurements was used to calculate a cab protection factor. During the evaluations, one PDM was placed inside the tractor cab (near the tractor operator) and one PDM was placed outside (near the air intake) to count particles. During the evaluations, the instruments were switched to prevent instrument bias from affecting the findings. The ratio of the two measurements (i.e., protection factor = outside concentration / inside concentration) was used to calculate how efficient the tractor cab was at removing aerosols. The John Deere cab was more than 99 percent efficient at removing aerosols larger than 3.0 microm in diameter and had protection factors greater than 260 for particles larger than 3.0 microm (indicated by the PDM results). The Nelson cab was more than 99 percent efficient at removing aerosols larger than 3.0 microm in diameter and had protection factors greater than 200 for particles larger than 3.0 microm (indicated by the PDM results). For aerosols smaller than 1.0 microm in diameter (indicated by a PortaCount Plus instrument), the John Deere cab provided a mean protection factor of 43 and the Nelson cab provided a mean protection factor of 16. The results from this study indicate that tractor cabs can be effective at removing different size aerosols depending on the seals and filters used with the enclosure. This study has also demonstrated the practical use of real-time aerosol counting instrumentation to evaluate the effectiveness of enclosures and to help identify leak sources. The method used in this study can be applied to various cabs used in different industries including agriculture, construction, and manufacturing.

Pesticide application can create aerosols that pose a health risk to the workers. During air blast sprayings in orchards, dilute emulsions, solutions, and suspensions of pesticides are sprayed into an air flow of about 44 to 67 m/s (100 to 150 mph). This results in a mist with a primary droplet size in excess of 100 μm and some smaller droplets. Thus, pesticide spray application can cause detectable pesticide exposure via respiration and skin exposure routs [Carman et al., 1982; Wojeck et al., 1980]. The U.S. EPA Worker Protection Standard (WPS) requires that applications and workers must wear the personal protective equipment specified by label [Title 40 Code of Federal Regulations, 1992]. To comply with the EPS, a governmental agency or manufacturer must declare in writing that the enclosed cab (Fig. 1) provides protection which is equivalent to the protection provided by a respirator. For agricultural cabs to be an acceptable substitute for respirators, cab manufacturers much demonstrate a 50 to 1 reduction in pesticide exposure during pesticide applications [Department of Pesticide Regulation, 1995, and California Department of Food and Agriculture, 1991]. Frequently, however, pesticide concentrations outside a cab are not large enough to determine whether the cab offers a protection factor of 50. Therefore, a study was undertaken

Industrial hygiene sampling for total airborne particulate during the manufacture of a concrete patching compound revealed concentration estimates which exceeded the ACGIH TLV of 10 mg/m3. These results led to recommendations for the implementation of improved engineering controls and the initiation of a respiratory protection program on an interim basis. The 3M 9910 disposable respirator was selected for use based upon a knowledge of existing total dust concentrations and a review of assigned protection factors for the various classes of respiratory protective devices. A follow-up evaluation by NIOSH investigators revealed that use of 3M 9910 respirators reduced total dust exposures to levels considered to be acceptable, but that the assigned protection factor derived from a set of workplace protection factors was less than anticipated. The results of this study suggest the need for inmask sampling after the implementation of respiratory protection to ensure, in a direct manner, that the particu...