Ronald M. Hall

Health effects and occupational exposures among office workers near the World Trade Center disaster site.

The extent of health effects and exposure to environmental contaminants among workers and residents indirectly affected by the September 11, 2001, attack on the World Trade Center (WTC) is unknown. The objective of this study was to evaluate concerns related to health effects and occupational exposures three months after the WTC disaster among a population of employees working in a building close to the disaster site. A cross-sectional questionnaire survey was performed of Federal employees working near the WTC site in New York City (NYC) and a comparison group of Federal employees in Dallas, Texas. An industrial hygiene evaluation of the NYC workplace was conducted. Constitutional and mental health symptoms were reported more frequently among workers in NYC compared to those in Dallas; level of social support was inversely related to prevalence of mental health symptoms. Post-September 11th counseling services were utilized to a greater degree among workers in NYC, while utilization of other types of medical services did not differ significantly between the groups. No occupational exposures to substances at concentrations that would explain the reported constitutional symptoms were found; however, we were unable to assess potential occupational exposures in the time immediately after the WTC disaster. There is no evidence of ongoing hazardous exposure to airborne contaminants among the workers surveyed. Specific causes of reported constitutional health symptoms have not been determined. Health care providers and management and employee groups should be aware of the need to address mental health issues as well as constitutional symptoms among the large number of workers in the NYC area who have been indirectly affected by the WTC disaster.

Evaluation of a Tractor Cab Using Real-Time Aerosol Counting Instrumentation

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 manufacturers 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.

An evaluation of an engineering control to prevent carbon monoxide poisonings of individuals on and around houseboats

From 1990 to 2000, a total of 111 carbon monoxide (CO) poisonings occurred on Lake Powell near the Arizona and Utah border. Seventy-four of the poisonings occurred on houseboats, and 64 were attributable to generator exhaust alone. Seven of the 74 houseboat-related CO poisonings resulted in death. Although many of the reported CO poisonings occurred to members of the general public, some poisonings involved workers performing houseboat maintenance. The National Institute for Occupational Safety and Health evaluated an engineering control retrofitted to a houseboat gasoline-powered generator to reduce the hazard of CO poisoning from the exhaust. The control consisted of a water separator and a 17-foot exhaust stack that extended 9 feet above the upper deck of the houseboat. When compared to a houseboat having no engineering controls, study results showed that the exhaust stack provides a dramatically safer environment to individuals on or near the houseboat. CO concentrations were reduced by 10 times or more at numerous locations on the houseboat. Average CO concentrations near the rear swim deck of the houseboat, an area where occupants frequently congregate, were reduced from an average of 606.6 ppm to 2.85 ppm, a reduction greater than 99%. CO concentrations were also reduced on the upper deck of the houseboat. Hazardous CO concentration in the confined area beneath the near swim deck were eliminated. Based on the results of this study, it is clear that houseboats having gasoline-powered generators that have been outfitted from the factory or retrofitted with an exhaust stack that extends well above the upper deck of the boat will greatly reduce the hazard of CO poisoning.

Exposure Assessment for Roofers Exposed to Silica during Installation of Roof Tiles

This case study is presented for use with graduate students in educational administration. The intent is to further those students’ preparation to deal with cultural and organizational change, along with the examination of the role of the administrative team as instructional leaders. One of the primary roles of the building principal is to be the instructional leader and create a climate that is conducive to learning. The scenario for this case is built around a negative atmosphere that will require campus-level administrators to transform the campus into a high-performing school in a brief period of time.Occupational exposure to silica in the construction industry has been well documented,(1–7) and respirable crystalline silica (quartz and cristobalite) has been associated with silicosis,(8,9) lung cancer,(10,11) pulmonary tuberculosis,(12,13) and airway diseases.(14,15) These concerns prompted a local construction union to request assistance from the National Institute for Occupational Safety and Health (NIOSH) for health hazard evaluations concerning exposures to dust and silica among roofers in Phoenix, Arizona. In response to these requests, NIOSH performed field studies to evaluate roofers’ exposures to silica. Health Effects Associated with Silica Exposure Silicosis is a disease of the lung caused by the deposition of fine crystalline silica particles (10 μm or less in diameter) in the lungs. The deposition of silica particles in the lungs triggers a chronic inflammatory response resulting in normal lung tissue being replaced with scar tissue (fibrosis). Symptoms of silicosis may include cough, shortness of breath, chest pain, early fatigue with exertion, and wheezing. Silicosis usually occurs after years of exposure (chronic) but may appear in a shorter period of time (acute) if exposure concentrations are very high. Acute silicosis is typically associated with a history of high exposures from tasks that produce small particles of airborne dust with a high silica content.(16) The International Agency for Research on Cancer (IARC) in 1996 concluded that there was “sufficient evidence in humans for the carcinogenicity of inhaled crystalline silica in the form of quartz or cristobalite from occupational sources.”(17) Workers diagnosed with silicosis are also at an increased risk of developing tuberculosis due to silica particles disabling the macrophages.(18) For a diagnosis of occupational silicosis, workers must have a history of exposure to respirable silica and a confirmatory test such as a chest X-ray, chest computed tomography (CT), or lung biopsy.

SILICA EXPOSURE IN HAND GRINDING STEEL CASTINGS

Exposure to silica dust was studied in the grinding of castings in a steel foundry that used conventional personal sampling methods and new real-time sampling techniques developed for the identification of high-exposure tasks and tools. Approximately one-third of the personal samples exceeded the National Institute for Occupational Safety and Health recommended exposure limit for crystalline silica, a fraction similar to that identified in other studies of casting cleaning. Of five tools used to clean the castings, the tools with the largest wheels, a 6-in. grinder and a 4-in. cutoff wheel, were shown to be the major sources of dust exposure. Existing dust control consisted of the use of downdraft grinding benches. The size of the casting precluded working at a distance close enough to the grates of the downdraft benches for efficient capture of the grinding dust. In addition, measurements of air recirculated from the downdraft benches indicated that less than one-half of the respirable particles were removed from the contaminated airstream. Previous studies have shown that silica exposures in the cleaning of castings can be reduced or eliminated through the use of mold coatings, which minimize sand burn-in on the casting surface; by application of high-velocity, low-volume exhaust hoods; and by the use of a nonsilica molding aggregate such as olivine. This study concluded that all these methods would be appropriate control options.

Case Study: Evaluation of Carbon Monoxide Emissions from Engines on Recreational Boats Equipped with Prototype Catalysts

Column Editor Lawrence F. Mazzuckelli1Division of Surveillance, Hazard Evaluation and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio 2Division of Applied Research and Technology, National Institute for Occupational Safety and Health, Cincinnati, Ohio 3Engine, Emissions, and Vehicle Research Division, Southwest Research Institute, San Antonio, Texas 4California Air Resources Board, Mobile Source Control Division, El Monte, California

An Evaluation of an Aftermarket Local Exhaust Ventilation Device for Suppressing Respirable Dust and Respirable Crystalline Silica Dust from Powered Saws

The objective of this study was to quantify the respirable dust and respirable silica exposures of roofing workers using an electric-powered circular saw with an aftermarket local exhaust ventilation attachment to cut concrete roofing tiles. The study was conducted to determine whether the local exhaust ventilation attachment was able to control respirable dust and respirable silica exposure below occupational exposure limits (OELs). Time-integrated filter samples and direct reading respirable dust concentrations were evaluated. The local exhaust ventilation consisted of a shroud attached to the cutting plane of the saw; the shroud was then connected to a small electric axial fan, which is intended to collect dust at the point of generation. All sampling was conducted with the control in use. Roofers are defined as those individuals who only lay tiles. Cutters/roofers are defined as those workers who operate the powered saw to cut tiles and also lay tiles. Respirable dust from this evaluation ranged from 0.13 to 6.59 milligrams per cubic meter (mg/m3) with a geometric mean of 0.38 mg/m3 for roofers and from 0.45 to 3.82 mg/m3 with a geometric mean of 1.84 mg/m3 for cutters/roofers. Cutters/roofers usually handle areas close to crevices, edges, or tips of the roof whereas roofers handle areas where complete tiles can be placed. The respirable dust exposures for all cutters/roofers indicated concentrations exceeding the Occupational Safety and Health Administrations (OSHA) permissible exposure limit (PEL) for respirable dust containing silica; it was also exceeded for some of the roofers. The respirable silica concentrations ranged from 0.04 to 0.15 mg/m3 with a geometric mean of 0.09 mg/m3 for roofers, and from 0.13 to 1.21 mg/m3 with a geometric mean of 0.48 mg/m3 for cutters/roofers. As with respirable dust, the respirable silica exposures for cutters/roofers were higher than the exposures for roofers.

A Summary of Research and Progress on Carbon Monoxide Exposure Control Solutions on Houseboats

Investigations of carbon monoxide (CO-related poisonings and deaths on houseboats were conducted by the Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. These investigations measured hazardous CO concentrations on and around houseboats that utilize gasoline-powered generators. Engineering control devices were developed and tested to mitigate this deadly hazard. CO emissions were measured using various sampling techniques which included exhaust emission analyzers, detector tubes, evacuated containers (grab air samples analyzed by a gas chromatograph), and direct-reading CO monitors. CO results on houseboats equipped with gasoline-powered generators without emission controls indicated hazardous CO concentrations exceeding immediately dangerous to life and health (IDLH) levels in potentially occupied areas of the houseboat. Air sample results on houseboats that were equipped with engineering controls to remove the hazard were highly effective and reduced CO levels by over 98% in potentially occupied areas. The engineering control devices used to reduce the hazardous CO emissions from gasoline-powered generators on houseboats were extremely effective at reducing CO concentrations to safe levels in potentially occupied areas on the houseboats and are now beginning to be widely used.

Exposures to Lead, Metals, and Wood Dust During Stripping and Refinishing Furniture

The National Institute for Occupational Safety and Health (NIOSH) received a request for a Health Hazard Evaluation (HHE) from a management official at a furniture finishing company. The request concerned worker exposures to lead and other metals that may result from stripping and refinishing furniture. A survey was conducted to evaluate worker exposures in the furniture stripping shop for lead, other metals, and wood dust during typical wood stripping and refinishing operations.

Use of ambient aerosol for testing agricultural cabs for protection against pesticide aerosol.

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