Nancy Clark, MA, CIH, CSP; Harry Monioudis, MS; Mount Sinai-Irving J. Selikoff
Center for Occupational and Environmental Medicine
Goldberg, PhD, CIH; Walter Jones, MS
In 1995, CPWR – Center for Construction Research and Training awarded a small-study grant to Hunter College School of Health Sciences and the Mount Sinai Center for Occupational and Environmental Medicine. The grant was to be used to characterize flammable atmospheres and solvent exposures to metal maintenance workers during refinishing of metal interiors of commercial elevators and other metal surfaces. The main goal was to assess the use of substitute refinishing materials of lower flammability and toxicity. The investigation was conducted jointly with companies in the metal-polishing industry and Local 8A-28A of the International Brotherhood of Painters and Allied Trades.
Metal maintenance workers maintain decorative finishes in commercial and residential buildings in cities throughout the country. Architectural finishes on the interior and exterior of buildings, including elevator interiors, require regular cleaning and refinishing to maintain design appearances. Bronze and other metal finishes are protected with a clear lacquer coating to protect the surface from tarnish and scratches. The materials used to protect surfaces and to remove the protective coatings prior to refinishing contain volatile organic solvents with recognized fire and health hazards.
Nationally, about 1,200 metal polishers are employed at 100 companies. Many metal refinishers work for companies who also provide other cleaning and maintenance services. Most metal maintenance companies employ fewer than 50 workers and do not have the full-time services of safety and health professionals. Work is performed during day and evening shifts and scheduled so that work activities do not interfere with a building's usual functions.
Many of the metal maintenance companies as well as the union of metal refinishers are members of a national trade organization. The trade group meets regularly to address common issues facing the industry as a whole including the environmental and occupational health impact of industry operations.
Basis for This Study
Industry concerns regarding the use of volatile materials in metal polishing have grown over the past five years for two reasons. For one, in 1992 two refinishers were killed and another was seriously injured in a St. Louis elevator car. The materials they were using produced a flammable atmosphere that was most likely ignited by heat from an electric light bulb or contact with a live electrical component. The elevator doors were closed for refinishing and the controls had been locked out to prevent the car from being summoned to other floors. The work crew was trapped inside. By the time the doors were pried open from the outside, one man was dead from carbon monoxide poisoning and another suffered second- and third degree burns and died 39 days later. A third worker survived first- and second-degree burns.
A second reason for industry concern with refinishing chemicals is environmental regulations limiting volatile organic compounds in architectural coatings. Protective coatings and solvents used in this industry have a high percentage of volatile organic compounds and the industry has been investigating products with reduced volatile-organic-compound content. In addition to regulatory concerns, the presence of volatile organic compounds in commercial buildings and the quality of indoor air increasingly are issues for owners and managers.
Although, on the surface, refinishing operations involve simply the removal of old lacquers and the spraying on of new coatings, the work demands great skill. Metal polishers must have extensive knowledge of refinishing materials, methods of using these materials, and precise treatments for surfaces of different metals and different degrees of damage. Although the design and size of elevator cars may vary, the work tasks, equipment, and materials used to refinish most metal surfaces are standardized throughout the industry.
Workers performing metal maintenance in elevators are equipped with air-purifying respirators, gloves, eye protection, and cotton work uniforms. Other safety equipment on site includes fire extinguishers inside and outside the elevator car, lidded plunger cans for solvent dispensing, and covered waste cans.
The predominant stripper used in elevators is a Class 1A flammable liquid containing organic solvents with a flash point of 20° F and a lower explosive limit of 1.8% (Gloss-Flo Corporation 1984).
Inhalation is the primary route of exposure to solvents, although some of the components, notably methanol, are readily absorbed through the skin. Health effects associated with acute exposure to the stripper include central-nervous system depression and irritation to the skin, eyes, and upper respiratory system. Chronic exposure may cause peripheral neuropathy and damage to the optic nerve, liver, and kidneys (Hathaway, Proctor, and Hughes 1996).
The lacquer is a nitrocellulose material in an organic solvent with a flash point of 56° F and a lower explosive limit (LEL) of 1.1 %. (The flash point is the lowest temperature at which a liquid gives off enough vapor to ignite.) Prior to spraying, the lacquer is diluted with a lacquer thinner that has a flash point of 67° F and a lower explosive limit of 1.1 %. Both materials are classified as Class 1B flammable liquids (Agate Lacquer Manufacturing 1986).
The lacquer is a complex mixture of toluol, butanol, isopropanol, amyl acetate, butyl acetate, n-propyl acetate, glycol ether, methyl isobutyl ketone, and ethyl 3-ethoxypropionate. The lacquer thinner contains methyl isobutyl ketone, toluol, butanol, amyl acetate, butyl acetate, and n-propyl acetate.
Inhalation and skin contact are the primary routes of exposure. Health effects associated with these materials include central nervous system depression and irritation. Chronic exposure may cause permanent damage to the nervous system, liver, and kidneys (Hathaway, Proctor, and Hughes 1996).
When elevator doors are closed, the cars certainly meet the NIOSH definition of a confined space (see National Institute for Occupational Safety and Health 1987). The definition of confined space used by the US Occupational Safety and Health Administration (OSHA) in its 1994 confined-space standard for general industry has a definition similar to NIOSH's. This OSHA standard requires employers to implement confined-space-entry procedures.
During metal refinishing, flammable and toxic materials are introduced into the space, creating potentially hazardous atmospheres. NIOSH does not specifically define hazardous atmospheres. However, OSHA considers a toxic atmosphere to be greater than the permissible exposure limit and a flammable atmosphere to be greater than 10% of the lower explosive limit. Potential ignition sources include heat from lighting fixtures, exposed wiring, and arcing from power sanders and compressors.
OSHA and NIOSH investigated the St. Louis disaster and recommended that the metal maintenance industry adopt confined-space entry program procedures and training described in the NIOSH publications, Working in Confined Spaces and A Guide to Safety in Confined Spaces. NIOSH also recommended that employers follow precautions outlined in a publication of the American Society of Mechanical Engineers (1991).
Researchers at Mount Sinai performed preliminary evaluations of the nature and extent of the hazards associated with refinishing elevators. Investigators observed work procedures at five elevator refinishing jobs, monitored the elevator cars for flammable atmospheres, and evaluated worker exposures to organic solvents.
The goals of this preliminary investigation were to observe work practices of metal refinishers in elevators, assess the fire hazard, assess exposure to volatile solvents during stripping and refinishing and develop an approach to hazard control.
Findings and Conclusions
The results of the preliminary investigation formed the basis for the study design of the current investigation. The most important findings of the preliminary investigation are as follows:
1. Personal sampling results during stripping, preliminary investigation
Spraying operation. Exposure to specific organic solvent components of the lacquer and thinner was not assessed. However, in order to get an estimate of vapor generation, sampling for total hydrocarbons was conducted in four elevators. The results averaged 114 parts per million (PPM) with a range of 43 PPM to 370 PPM Approximately eight ounces of the lacquer and thinner mixture, containing nine volatile materials, is applied during spraying. Because of the low lower-explosive-limit readings obtained during spraying (10%), the short time of exposure (15 minutes), the small quantity of material used, and the high costs associated with analysis of the volatile components of the lacquer, exposures to the specific solvents were not assessed. However, the authors are not confident that a more-sophisticated exposure assessment protocol that could account for both the solvent vapor and mist components would yield different results.
The concentration of solvent vapors generated could potentially be reduced by adhering to strict work practices, such as minimizing the amount of stripping solvent used, keeping stripping containers closed, placing soiled solvent rags in closed containers and stripping smaller areas of the doors at a time. Implementation of these work practices could be coupled with constant lower-explosive-limit monitoring so that work could be interrupted if 10% of the lower explosive limit was reached. This approach is cumbersome for the metal polishers doing the work and requires close supervision and specialized training.
Based on this review of possible control options, substitution of materials was considered to be the most efficacious and protective approach. In the interim, the industry developed elevator refinishing procedures involving a combination of work practices, personal protective equipment, and more-frequent door opening.
Fire and toxic
The preliminary investigation clearly highlighted the fire and toxic hazards associated with the stripping operation in closed elevator cars. Given the limited resources for the study, the authors decided to focus on work in closed elevator cars and not to characterize the hazards during refinishing of other metal surfaces (surfaces that are not in elevators). As mentioned above, the authors decided not to assess exposures to individual substances associated with lacquering.
Most of the alternative products identified have proprietary formulations and many contain substances that do not have exposure limits set by OSHA, NIOSH, or the American Conference of Government Industrial Hygienists (ACGIH). Confidentiality of product ingredients has been maintained for this research and specific substances are identified by chemical class when required. Descriptions of ingredients appear below. Exposure limits are provided when available.
Strippers # 1-3. These three strippers have flash points of 126° F, 199° F, and 212° F respectively, as indicated by the manufacturer. All of the strippers contain d-limonene along with other solvent components. D-limonene is a well known alternative solvent widely used in degreasing operations and as a substitute in other petroleum-based solvent applications. The American Industrial Hygiene Association (AIHA), the only organization that has established an exposure limit, issued a workplace environmental exposure level of 30 PPM as an 8-hour time-weighted average (TWA) in 1995. The most notable health effects of d-limonene are irritation to skin and eyes. Sensitization to the skin may also occur. Inhalation can cause headache, dizziness, nausea and upper respiratory irritation. Chronic exposure may cause drying and cracking of the skin. Animal studies have shown adverse effects in the liver at high exposure levels. AIHA considered this finding in setting the workplace environmental exposure limit for d-limonene at 30 PPM The other components in these strippers also cause eye, skin and mucous membrane irritation and may cause systemic effects when inhaled (American Industrial Hygiene Association 1993).
Strippers # 4 and 5. These two strippers are manufactured by the same company and each one has different ingredients. Both strippers have very low vapor pressures (less than 1 millimeter of mercury) and flashpoints above 200° F, as indicated by the manufacturer. Both strippers contain materials that cause irritation to the skin and eyes.
Lacquers #1-3. All substitute lacquers have flashpoints above 120° F and contain proprietary mixtures of organic materials. Inhalation and skin contact are primary routes of exposure. Health effects include irritation to skin, eyes, and mucous membranes and potential long-term effects to liver and kidneys.
of traditional, solvent-based strippers and lacquers
Personal air samples were collected to assess worker exposure to specific solvent vapors during closed door stripping and to total hydrocarbons during spraying using the traditional solvent- based materials. MSA Flow Lite pumps were calibrated at approximately 50 milliliters per minute in order to minimize the possibility of breakthrough of acetone and methanol, as occurred during the preliminary study. Sampling times were determined by the time period necessary for the completion of each task (e.g., stripping, lacquering). All solvents were monitored using charcoal tubes (50/100 mesh) except for methanol for which silica gel tubes were used. Stripping and spraying tasks were monitored separately.
Two workers engaged in the removal of the old lacquer finish from the inside surfaces of the elevator doors were monitored for exposure to acetone, ethyl acetate, methyl ethyl ketone and methanol. The elevator doors remained closed during the sampling period. Diacetone alcohol was excluded from the sample collection because preliminary sampling indicated that concentrations of this substance were extremely low.
The samples were analyzed in accordance with NIOSH analytic methods P & CAM 127 for volatile organic compounds, NIOSH method 2000 for methanol, and modified OSHA M139 for solvents (National Institute for Occupational Safety and Health 1984). All samples were analyzed by a laboratory accredited by AIHA.
of substitute, water-based strippers and lacquers
Exposure to the materials in the water-based products is brief, less than 20 minutes. Most of these materials do not have short-term exposure limits. However, it is important to control exposures within some reasonable limit, even if the 8-hour exposure limit is not exceeded. For substances with threshold-limit value time-weighted averages (TLV-TWAs) that do not have short-term exposure limits, the ACGIH recommends "excursion limits." This study uses the excursion-limit concept for materials that do not have short-term exposure limits, but have an 8-hour limit set by ACGIH, AIHA, or the manufacturer.
ACGIH defines excursion limits as follows:
Lower-explosive-limit measurement results confirm the findings of the preliminary investigation described above (see table 2). Lower-explosive-limit measurements were obtained in six closed elevator cars during stripping with solvent-based materials. Results indicate that four of the six operations resulted in concentrations above 10% of the lower explosive limit. Of those, two were above 20% of the lower explosive limit. In all cases in which 10% of the lower explosive limit was exceeded, the 10% level was reached within two to five minutes of door closure.
Atmospheres generated during spraying operations did not exceed 10% of the lower explosive limit. However one sample reached the 10% level, indicating the potential for creation of a flammable atmosphere in confined space locations.
Due to equipment difficulties, measurements were not taken in four of the stripping operations and five of the spraying operations.
Lower-explosive-limit measurements were taken during stripping and spraying using water-based strippers and lacquers (tables 3 and 4). Five aqueous strippers in 17 elevator cars and 3 aqueous lacquers in 13 elevator cars were evaluated.
All measurements were less than 10% of the lower explosive limit, indicating that the use of these water-based materials inside closed elevator cars did not create flammable conditions.
to stripper vapors
Sampling times ranged from 14 to 71 minutes with an average of 33 minutes. The stripping compound contains materials with relatively high vapor pressures accounting for the high concentrations generated in these relatively short work periods. Because of the brief sampling times, 8-hour time-weighted averages were not calculated.
Water-based stripping materials
Personal monitoring was performed during use of three water-based strippers (tables 6-8). Because all of the materials are composed of proprietary mixtures, the results for various ingredients are identified by chemical class when required by confidentiality agreements. Sampling times for strippers #1-3 ranged from 10 to 16 minutes.
Excursion limits (5 times the exposure limit) were exceeded for several of the solvent components in each of the three strippers. Results indicate that the lowest exposures were generated during use of stripper #3. Only one excursion limit (for the ester solvent) was exceeded for that stripper.
(Parts per million)
The results of lower-explosive-limit measurements and exposure monitoring presented here might underestimate true exposures. Only two companies participated in the study. One performed refinishing with traditional materials, while the other worked with the water-based products. The crews selected to perform the work with the new products were very experienced and safety conscious. The presence of investigators may also have encouraged especially careful work practices and, thus, affected the results.
This study did not attempt to assess the effects of solvent-based products on the health of metal polishers. The investigation did confirm that workers in this industry are potentially exposed to short-term high-peak exposures to solvents while using traditional strippers. However, these exposures are not necessarily typical of the workers' daily exposures. On the whole, workers in the industry do not perform work tasks only in one setting, but work in a number of indoor and outdoor environments. Those who perform stripping and finishing tasks in closed elevators on one day might be working on building facades the following day. In this outdoor setting, exposures could reasonably be expected to be lower than in closed elevators.
Based on the results of this study, these measures are recommended:
The introduction of new products represents an important step forward for the industry and workers alike. In the best tradition of toxic-use reduction, the new products will meet or exceed air pollution requirements, and considerably lower the risk to life and health of workers. In addition, the introduction of the alternate products should reassure building owners and managers who are increasingly confronted by both regulators and building occupants regarding the use of hazardous materials on their properties.
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