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Publication Number: FHWA-RD-98-180
Safety and Health on Bridge Repair, Renovation and Demolition Projects
Health Hazard Programs, Practices, and Procedures
Table of Contents
Section 1: Introduction
Section 2: General Principles of Health Hazard Control
Section 3: Hazard Communication
Section 4: Lead
Section 5: Other Metal Fumes
Section 6: Silica and Other Dusts
Section 7: Noise
Section 8: Heat Stress
Section 9: Carbon Monoxide
Section 10: Ergonomic Hazards
Section 11: Solvent Exposures
The purpose of this chapter is to discuss the various health hazards found on bridge RR&D sites and to outline programs that will prevent illnesses to workers from recognized health hazards. Potential health hazards abound for workers on bridge RR&D sites. Lead hazards may be created by abrasive blasting, burning, and welding activities. Silica, noise, nuisance dust, carbon monoxide, heat stress, solvent exposures, metal fumes, and ergonomic hazards may also be present on bridge RR&D sites. Many of these hazards can be controlled or eliminated with proper planning and the implementation of effective industrial hygiene programs.
SECTION 2: GENERAL PRINCIPLES OF HEALTH HAZARD CONTROL
Exposure Routes and Limits
Employees on bridge RR&D sites are generally exposed to health hazards through three major routes: inhalation, ingestion, and skin absorption. For example, lead most commonly enters bridge workers' bodies through the inhalation of lead fumes or dust, and through the ingestion of lead-contaminated foods. Solvents in paints and coatings may be absorbed through the skin.
Assessing the extent of exposure through inhalation routes is commonly done by air sampling methods. In air sampling, a known volume of air is drawn through a collection device such as a filter cassette clipped to an employee's collar. The filter is then analyzed for a particular contaminant or contaminants, and an exposure level can be found. When several sampling filters (or other collection devices) are worn by an employee throughout the day, the results of the individual samples can be combined to determine the employee's time weighted average (TWA) exposure level. If 8 hours of sampling is conducted using one or more filters, an 8-hour TWA exposure can be determined. These TWA exposure levels are used to figure out whether exposures are a health hazard by comparing the employee's TWA exposure with established occupational exposure limits. Most established occupational exposure limits, including those for lead, are expressed as 8-hour TWA exposure limits. The limits may be reduced due to longer work days.
Assessing exposures through ingestion and skin absorption are mainly done indirectly, by measuring the level of the contaminant (or its metabolite) in the blood, urine, or other body medium.
For inhalation, ingestion, and sometimes skin absorption routes of exposure, occupational exposure limits have been established that roughly define when the exposure becomes hazardous. Many different groups recommend exposure limits, including OSHA, the National Institute for Occupational Safety and Health (NIOSH), and the American Conference of Governmental Industrial Hygienists (ACGIH). The particular limits may be called by various names such as permissible exposure limits (PELs), threshold limit values (TLVs), occupational exposure levels (OELs), and recommended exposure limits (RELs).
Many occupational exposure limits refer to excessive exposure conditions outside the body, such as the OSHA PEL of 50 micrograms (µg) per cubic meter (m³) for lead fumes or dust in the air. Other exposure limits, known as biological exposure limits, help detect excessive levels of a contaminant in the body, whatever the route of exposure. The OSHA medical removal trigger point for lead in the blood of 50 µg/deciliter of blood is an example of a biological exposure limit. In this chapter, discussions of various hazards will primarily refer to the OSHA PELs and biological exposure limits where they exist.
Basic Hazard Control Principles
When a hazardous exposure condition is detected through air or biological sampling, a hierarchy of controls is employed to eliminate or reduce the hazard to employees. A hierarchy means that there is a priority order for the controls. In industrial hygiene, the first types of controls usually employed are engineering controls.
A. Engineering Controls
Ventilation: The most prominent engineering control used to eliminate industrial hygiene hazards is ventilation. There are two general types of ventilation controls-general and local exhaust. General ventilation uses non-contaminated air to dilute the levels of a contaminant in the air to a level that is not hazardous. The non-contaminated air can either be blown into the work area, or it can come in on its own by drawing out large amounts of contaminated air from the work area. An example of dilution ventilation on a bridge RR&D site would be providing a supply of clean air into the containment area.
Local exhaust ventilation typically uses smaller amounts of air directed at the source of the problem to control contaminants. An example includes the use of vacuum abrasive blasting systems that capture and recover the spent abrasive and removed substrate materials.
Substitution: Replacing a material that creates a health or safety hazard with a less toxic or safer material is a very useful engineering control technique. Silica hazards from the use of sand in abrasive blasting can be eliminated by substituting a non-silica-based abrasive such as slag, steel shot, organic abrasives, or non-silica-bearing minerals. Flammable solvent-based paints can sometimes be replaced by water-glycol based paints.
B. Administrative Controls
When engineering controls are not feasible, available, or completely effective, administrative controls may be used. Administrative controls rely on reducing scheduled work times in a contaminated area, thus reducing exposures. Employees may be rotated from a contaminated area to a non-contaminated area to reduce exposure times and, hence, 8-hour TWA exposure levels.
C. Work Practice Controls
Exposures to hazards can be reduced by doing jobs in ways that minimize the creation of hazardous conditions. Vacuuming dusts instead of sweeping or cleaning with compressed air reduces exposures. Using wet methods to clean up contaminated areas may also reduce exposures to dusts.
D. Personal Protective Equipment
When the control measures above have been used and hazardous exposure conditions still exist, various forms of personal protective equipment may be used to protect employees. The use of personal protective equipment is usually a last choice because its effectiveness depends on the proper selection, use, and maintenance of the equipment. All these factors are subject to the laws of entropy and they take a large amount of effort to maintain effectiveness.
Personal protective equipment exists for virtually every part of the body. Commonly used personal protective equipment on bridge RR&D sites includes respirators, ear plugs, safety glasses, gloves, coveralls, safety footwear, and personal fall arrest systems.
E. Respiratory Protection
Before respirators are chosen as a hazard control measure, several steps must be taken. The first step in controlling any potentially hazardous airborne exposure is to measure the concentration of the contaminant through air sampling techniques. Air sampling provides information about whether the contaminant is hazardous to unprotected employees through the airborne route of exposure. Sampling results are compared with published exposure limits such as OSHA's PELs or the ACGIH's TLVs to determine if the contaminant levels in the workplace may be hazardous to workers. For example, OSHA's PEL for lead fumes and dusts is 50 µg/m³. OSHA does not require an employer to institute engineering controls or provide respirators when employees are exposed to air contaminant levels below the PEL. However, if an employer chooses to require respirators even when they are not required (e.g., at exposure levels below the PEL), the OSHA respiratory protection requirements in 1910.134 must be followed.
If contaminant levels exceed the PEL, OSHA requires that engineering and work practice controls be applied first to reduce contaminant levels to below the PEL. Only after it has been shown that engineering and work practice controls are unable to reduce exposures to below the PEL, or that these controls are unfeasible, may respiratory protection be considered as an exposure control means.
Once it has been determined that respirators are necessary or required, care must be taken to properly select, use, and maintain the respiratory protection equipment. Both the nature of the air contaminant and its exposure concentration must be considered in properly selecting a respirator.
Employees must be provided training in the proper use and care of the respirators they are provided, and must be medically fit to wear the respirator. The employer must designate a respiratory protection program administrator who is responsible for overseeing the employer's respirator program and conducting the required evaluations of the program's effectiveness. The requirements for an effective respiratory protection program are found in OSHA's 1910.134 regulation. This standard was updated in 1997, and became effective in April 1998. A copy of the 1998 respiratory protection standard and its appendices is found in appendix S.
According to 1910.134, whenever respirators are necessary to protect the health of employees, or whenever an employer requires the use of respirators, the employer must have a written respiratory protection program that covers certain required worksite-specific procedures for respirator use. Note that the written program must be worksite-specific, and in most cases a generic type of program will not suffice unless all of the employer's worksites are identical in nature. The basic elements that must be covered in a written respiratory protection program are:
All of the procedures spelled out in the written program must then be implemented.
If employees on a worksite casually use respirators, but they are not required to use them because of worksite overexposure conditions or by employer policy, the employer still has a few obligations. First, the employer must determine that the employee's voluntary or non-mandatory respirator use will not create a hazard. Second, the information provided in appendix D of 1910.134 must be provided to all employees who use respirators not mandatorily worn. Third, an abbreviated respiratory protection program must be implemented that includes provisions for initial medical screening of the voluntary respirator user, means and training so that the user can properly clean, store, and maintain the respirator. And lastly, unless the voluntarily used respirator is a filtering facepiece respirator (e.g., paper dust mask), a short written program must be put together that discusses how the previous three items will be accomplished.
The OSHA respiratory protection standard (1910.134) that went into effect in April 1998 differs from its predecessor significantly in the area of medical evaluations for individuals prior to respirator use. For some employees, the additional stresses on the cardiovascular system associated with using a respirator may be unhealthy. Therefore, the standard requires that, even before an employee is fit tested for a respirator, the employer shall provide a medical evaluation to determine the employee's ability to use a respirator.
The medical evaluation must be done by a physician or other licensed health care professional who uses a mandatory medical questionnaire (found in appendix C of 1910.134) or an initial medical examination that obtains the same information as the medical questionnaire. Prior to giving the medical questionnaire, the health care provider must be given the following information:
Any positive response to a question on the questionnaire by the prospective respirator wearer triggers a follow-up medical examination by the health care provider.
Upon completion of the initial evaluation (and follow-up exam if necessary), the health care provider must make a medical determination regarding the employee's ability to use a respirator, and provide a written report to the employer regarding the employee's ability to use a respirator, any limitations on respirator use, the need for any further medical evaluations, and a statement that the provider has given the employee a copy of the written medical determination report that is provided to the employer.
The 1998 respirator standard also contains detailed sections on respirator fit testing; the proper use of respirators; the use of respirators in emergency situations; the maintenance, care, cleaning, storage and inspection of respirators; breathing air quality and use in supplied-air type respirators; training; program evaluation; and recordkeeping.
Setting up and maintaining an effective respiratory protection program is hard work, but the effort is necessary in light of the function that respirators serve to protect workers from airborne contaminants. You may want to consult a qualified industrial hygienist to set up an initial respiratory protection program, and training company personnel to administer an ongoing program. A sample written respiratory protection program is provided in appendix U.
SECTION 3: HAZARD COMMUNICATION
Construction projects often require the use of materials and chemicals that are hazardous. Employees must be aware of the identity and hazards of the chemicals they use. The company must establish a Hazard Communication Program in accordance with 29 CFR 1926.59 to ensure that employees understand the nature of the chemical materials they use. A hazard communication program has four main components.
SECTION 4: LEAD
Lead is a toxic substance that may enter the body by breathing or swallowing lead dusts, fumes, or mists. Once in the body, lead enters the bloodstream and may be carried to all parts of the body. It can especially affect the proper functioning of the kidneys, liver, brain, blood forming, and reproductive systems. Lead poisoning can occur from acute (short term, high level) or chronic (longer term, lower level) exposures. The body can eliminate some of the lead, but if there is continuing exposure to lead, the lead is stored in the body, and it may cause irreversible damage to cells, organs, and whole body systems. After exposure stops, it takes months or even years for all lead to be removed from the body.
Many of the bridges in this country have been primed and painted for years with lead-based coatings. In bridge RR&D work the operations that most often generate lead dust and fume exposures include:
In addition, workers on bridge RR&D sites may be exposed to lead when eating, smoking, or drinking if their food, drink, cigarettes, or hands are contaminated with lead.
In response to these hazards, OSHA established an occupational health standard to protect workers from the adverse health effects associated with lead exposures-Lead in Construction (1926.62). To encourage employers to comply with this standard, OSHA also began a compliance Special Emphasis Program in March 1996 to conduct targeted inspections in construction workplaces where there are lead exposures. A copy of this special emphasis directive (CPL 2.105) is found in appendix R.
Contractor Compliance Program Summary
A. Look for Lead
Perhaps the most important step in preventing lead poisoning is finding out before the job begins if lead is present on structures where welding, burning, abrasive blasting, or any other lead-exposing activities will be performed. Many times the owner will have already determined if lead is present in the structural components or coatings. In Connecticut, potential contractors are informed of the presence of lead on bridge structures, and are required to provide evidence of programs that protect employees from the hazards of lead (see appendix H). Model contract specifications have also been developed for owners of lead-painted bridges who are seeking contractors for RR&D work. The "Model Specifications for the Protection of Workers from Lead on Steel Structures" developed by the Center to Protect Workers' Rights (appendix I) is an example of these contract specifications. These specifications are usually included in contract information to advise potential contractors of the lead hazards present on the jobsite.
If information is not available about the nature of old coatings on bridges, the contractor must make an initial determination to see if lead is present. A visual inspection of the paint layers can sometimes reveal the presence of a red primer coating, which may indicate that a "red lead" primer was used. The presence of lead in coatings can be more definitively determined by taking paint chip samples and having them analyzed for lead, looking at prior maintenance records for indications of lead paint use, and the use of other assessment techniques such as X-ray fluorescence analyzers.
In general, it is probably wise on bridge RR&D sites to assume the presence of lead until exposure monitoring shows otherwise, and contractors should never assume that lead is not present solely on the basis of visual paint characteristics.
B. Lead is Found or Presumed on the Structure, but Potential Employee Exposure Levels are Unknown
When lead is present on the structure (or when there is doubt that the initial screening detected all the lead present), and when there are no prior lead employee exposure level data for similar projects within the last 12 months, an interim basic level lead protection program (LPP) must be established for employees performing certain activities before the structure is disturbed. This basic LPP needs to be set up prior to the commencement of work and kept in place until actual lead exposures can be determined. The basic program consists of:
The basis for requiring this interim basic LPP is that, until lead monitoring is completed, employees performing the various lead-disturbing activities listed below on leaded structures have exposures presumed to be above the PEL. The following exposures are presumed until monitoring shows differently:
Presumed Exposure = 50 to 500 µg/m³ for the following activities:
Presumed Exposure > 500 µg/m³ for the following activities:
Presumed Exposure > 2500 µg/m³ for the following activities:
C. Exposure Monitoring
When lead has been found during the initial screening process, employees' actual lead exposures must be determined through either historical exposure data obtained within the last 12 months or by actual exposure monitoring. Many contractors rely on historical data from past bridge RR&D jobs reflecting lead exposures above the PEL to justify establishing a full lead protection program on subsequent jobs. Extreme care must be exercised, however, when using sampling data from past jobs that show exposures below the lead action level or PEL to justify the establishment of no or a minimal lead protection program on a subsequent job. Factors such as the amount of lead in the paint and substrate, the number of prior paint coatings on the structure, and the nature of the work can vary greatly from structure to structure, rendering historical data unsuitable for determining lead exposures on subsequent jobs.
If historical exposure data are used, an exposure-appropriate lead protection plan as summarized in one of the sections D,E, or F below can be implemented prior to the beginning of the work. If no historical data exist, and employee lead exposure levels are unknown, the interim lead protection program must be established for lead-disturbing activities, and lead exposure monitoring must be done.
Exposure monitoring results can generally be grouped into three categories:
1. Exposures less than the Action Level of 30 µg/m³.
2. Exposures between the Action Level and the PEL of 50 µg/m³.
3. Exposures greater than the PEL of 50 µg/m³.
Exposure monitoring may at first be conducted on a few representative employees who are believed to have the highest exposures. If exposures are found to be above the action level, additional exposure monitoring may have to be done to establish the exposures of each job classification on the site. Periodic monitoring is required for exposures above the action level. All monitoring must consist of personal samples conducted for a full shift, and must represent an employee's regular, daily exposure to lead.
D. Lead Exposures Less than the Action Level
If lead exposure levels are less than the action level, the basic interim lead protection program can be cut back to consist of only the following elements:
For lead exposures between the action level and PEL, the basic interim lead protection program must be modified somewhat to consist of the following:
F. Lead Exposures Above the PEL
For lead exposures above the PEL, the basic interim lead protection program must be expanded somewhat to consist of the following:
Further details and information about establishing and maintaining a full lead protection program will be discussed in the next chapter. Many organizations have published guidelines and overviews of the lead standard and its provisions. Appendix G provides summary information on the lead standard and its provisions, including a decision tree regarding medical monitoring.
SECTION 5: OTHER METAL FUMES
In addition to creating lead fumes and dusts, blasting, burning, and welding operations may expose employees to other metallic fumes and dusts. Existing paints may contain heavy metals such as chromium, arsenic, cadmium, and zinc, and the metal structure itself may be composed of heavy metal components and iron. Blasting agents, such as metal slags, may also contain toxic metal contaminants such as beryllium and cadmium.
A variety of sampling and biological monitoring methods exist to measure exposures to these contaminants, and sampling may be employed as necessary to assess exposures. Laboratory analysis for many of these metals can be done using the same air sampling filter used to determine airborne lead exposures. Contractors should ask the lab or industrial hygienist collecting the samples about obtaining exposure results for these other metals at the same time lead sampling is conducted.
The following PELs have been established for exposures to metals:
*Because of their toxicities, OSHA has promulgated specific standards for cadmium and arsenic. Please refer to 1926.1127 for cadmium and 1926.1118 for arsenic. Biological exposure indices are also available for many of these substances.
As with most other air contaminants, a variety of engineering, administrative, work practice, and personal protective equipment controls should be used to eliminate the hazards or protect workers from hazardous exposures to these substance.
SECTION 6: SILICA AND OTHER DUSTS
In bridge RR&D work, abrasive blasting is often employed to remove old paints, coatings, and corrosion from steel structures. Employees who perform abrasive blasting and those who tend abrasive blasting operations are often exposed to excessive abrasive dust levels while performing their duties, in addition to the excessive lead levels.
If silica sand is used as the abrasive blasting material, employees must be protected from the silica hazards created during abrasive blasting because exposures to silica exceeding the PEL are common. The current silica dust PEL established by OSHA for the total respirable dust concentration is 10 mg/m³ ÷ (%SiO2 + 2). The use of other abrasive blasting materials often creates dust hazards as well. Most substitute materials have a PEL of 5 mg/m³ for the respirable fraction or 15 mg/m³ for the total dust.
Breathing dust containing crystalline silica particles in excess of the PEL may cause a disabling or fatal chronic lung disease known as silicosis. The dust can cause fibrosis or scar tissue formations in the lungs that reduce the lungs' ability to work to extract oxygen from the air. Exposure to silica may cause lung cancer as well.
Early stages of silicosis may go unnoticed. Continued exposure may result in a shortness of breath on exercising, possible fever, and occasionally bluish skin at the ear lobes or lips. Silicosis makes a person more susceptible to infectious diseases of the lungs such as tuberculosis. Progression of silicosis leads to fatigue, extreme shortness of breath, loss of appetite, pain in the chest, and respiratory failure, which may cause death. Acute silicosis may develop after short periods of exposure. Chronic silicosis usually occurs after 10 or more years of exposure to lower levels of quartz.
Silicosis is a preventable disease. In mid-1996 several governmental agencies such as NIOSH, Mine Safety and Health Administration (MSHA), and OSHA began programs to encourage the eradication of silicosis in the United States. In May 1996, OSHA began a Special Emphasis Program (SEP) for silicosis. This program directed OSHA Area Offices and State Plan States to begin conducting targeted inspections in industries where silica exposures are found. In construction, activities such as jack hammering, rock drilling, abrasive blasting, concrete mixing, concrete drilling, brick and concrete block or slab cutting, and guniting were targeted for inspection activities. A copy of the directive establishing the SEP is found in appendix Q.
To control exposures to silica the hierarchy of controls is used. For engineering controls, non-silica abrasives can sometimes be used to eliminate the silica hazard. Vacuum-blasting locally exhausts silica and other abrasive dusts at the point of operation. Water sprays alone or in combination with abrasive materials can also be used. Needle peening can be used to limit the creation of silica dusts.
Work practice controls may also be employed to reduce blasting dust exposures. Perhaps blasting can be performed on only portions of a steel structure, while combinations of grinding and peening and could be used elsewhere. Abrasive blasting tenders should limit cleanup operations that create dusts such as sweeping or compressed air clean up.
Administrative controls limiting exposure times to blasters are not usually effective since the dust levels created in abrasive blasting are so high. Rotating pot-tending and cleanup employees into non-exposure areas is, however, often effective in reducing daily exposures to abrasive dusts.
When engineering, work practice, and administrative controls are not employed or they are insufficient to fully control exposures to levels below the PEL, an effective crystalline silica control program needs to be established. An effective silica control program should include the following elements:
* Required by specific OSHA standards if an overexposure to crystalline silica exists.
In most cases, abrasive blasting with dry materials requires the use of respiratory protection because of the high exposures generated in blasting. Abrasive blasters are usually simultaneously overexposed to lead and to silica, and respirators selected must be capable of protecting employees from both hazards. The most suitable respirator for dually-overexposed employees is the Type CE supplied air abrasive blasting respirator operated in the pressure demand mode. Helpers and cleaners may also be overexposed to silica and a suitable air-purifying dust respirator can be used, provided exposures don't exceed the protection factor of the respirator.
Regardless of the type of abrasive used, employees must be protected from the high impact velocity of the abrasives through the use of suitable personal protective equipment such as leather gloves, aprons, and chaps. Safety shoes should also be worn if heavy pieces of work are handled. In most cases, abrasive blasting with dry materials requires the use of respiratory protection because of the high exposures generated in blasting.
SECTION 7: NOISE
Noise is a common hazard on most bridge RR&D sites. Air compressors, blasting equipment, and pneumatic hand tools may emit noise in excess of 90 decibels on the A scale (dBA). When employees are exposed to average workday noise levels above 90 dBA, permanent hearing loss could occur unless interventions such as engineering controls, personal protective equipment, and hearing conservation programs are implemented. The OSHA requirements for noise exposures on construction sites are found in 1926.52.
Administrative or engineering controls must be utilized to reduce noise exposures exceeding the permissible noise exposure of 90 dBA for an 8-hour TWA (see table below) when feasible. An example of a frequently used engineering control in construction is the use of a muffler on the exhaust port of pneumatic equipment. If such controls are not effective in reducing sound levels to within the levels specified in the table, personal protective equipment (ear plugs or muffs) must be provided to and used by each affected employee, and employees must participate in a hearing conservation program.
Employees must be allowed to select from a variety of hearing protection devices such as ear plugs or ear muffs. If the types of plugs provided to employees have several sizes, employees' ear canals must be measured to ensure the proper fit of the plug. Many one-size-fits-all type plugs are available, and thus eliminate the need for sizing plugs. The use of hearing protection devices is mandatory in work areas where average noise levels exceed 90 dBA. They should be worn in all areas above 85 dBA as well, since some employees may experience hearing losses at exposures to noise levels between 85 and 90 dBA.
In addition to requiring the use of hearing protection at average noise levels above 90 dBA, the employer must implement a hearing conservation program for employees working in areas with noise levels above 90 dBA. The following elements are included in a hearing conservation program:
All training should be documented on a form similar to that found in appendix D.
PERMISSIBLE NOISE EXPOSURES
SECTION 8: HEAT STRESS
Bridge RR&D activities during the summer months is hot work in many parts of the country. High ambient temperatures combined with the use of protective clothing in a containment enclosure is a recipe for heat illness if employees are not properly informed and protected.
Heat illnesses arise when the body's heat dissipation mechanisms such as sweating and increased bloodflow to the skin are unable to sufficiently remove heat due to metabolic, radiant, and conductive heat sources. When internal body temperatures rise, employees may experience heat-related disorders such as heat cramps, fainting, heat exhaustion, and heat stroke.
Heat exhaustion is characterized by heavy sweating, weakness, fatigue, nausea, and headache. In more serious cases, the victim can vomit or may become unconscious. Recognizing the onset of heat exhaustion and taking steps to cool the body are vitally important in reversing the deadly march toward heat stroke. Employees should rest in a cool or shady place and drink plenty of liquids until symptoms subside.
If the warnings of heat exhaustion are not heeded, employees may lapse into heat stroke, which is often fatal. In heat stroke, the body's temperature regulatory system fails and sweating often ceases because it is inadequate to remove accumulated heat. In heat stroke, internal body temperatures can reach 105ºF (40.6ºC) or higher, and the victim is often mentally confused and delirious or unconscious. Unless immediate steps are taken to reduce body core temperatures through means such as cooling the victim in water or placing the victim in an air conditioned area, brain damage or death could occur.
Like most health hazards, heat exposures are typically controlled through the use of engineering, administrative, and work practice controls. Avoiding exposure to hot ambient conditions is the best prevention-and perhaps work can be performed at night or in the early morning or later afternoon. When work in hot environments cannot be avoided, however, a general heat stress program that utilizes a combination of engineering, administrative, and work practice controls should be employed.
The heat stress program shall consist of at least:
Recommended work/rest regimens for various heat exposures have been established by the ACGIH based on the work loads of the employees. The most recent TLV booklet may be consulted to perform a heat stress survey.
SECTION 9: CARBON MONOXIDE
The presence of internal combustion engines, containment systems, and compressor-fed, supplied-air respirators on a bridge RR&D site sets up a potential for carbon monoxide problems. Carbon monoxide produced by gasoline and diesel engines may enter containment systems or the air intakes of supplied-air respirators.
Containment areas must be kept free of internal combustion engines and fuel-fired heaters. In addition, when the containment areas are kept under negative pressure to the outside (i.e., air is being sucked into the structure), care must be taken to locate internal combustion engines away from air intakes to the containment.
To avoid carbon monoxide contamination of breathing air to airline type respirators, the air intake for the system must be located away from all contaminant sources. In addition, the air must be periodically tested to ensure that carbon monoxide is not entering the system. The air quality section of the respiratory protection standard, 1926.103(f), provides additional considerations that must be followed to ensure purity of the breathing air to employees using supplied-air respirators.
SECTION 10: ERGONOMIC HAZARDS
The ergonomic hazards most anticipated on bridge RR&D sites include back strains and sprains from lifting, pushing, pulling and moving tools and materials, vibration-related disorders from the use of power tools, and repetitive motion disorders, especially resulting from work in awkward postures.
Back Injury Hazards
Back injuries may occur from repetitive lifting tasks or from a one-time event. NIOSH has published a Manual Lifting Guide which describes the variables that must be considered to effect safe lifts. These variables include the weight of the object lifted, size and configuration of the object, beginning height of the lift, ending height of the lift, number of lift repetitions, and several other factors. The importance of these factors must be understood by employees doing manual material handling tasks to avoid back injuries due to lifting, and lifts must be designed to stay within the recommended lifting limits.
The use of vibrating hand tools such as jackhammers, chippers, and grinders is associated with damage to the small blood vessels in the hand. The damage can lead to a disorder called Raynaud's disease. Raynaud's disease is characterized by a blanching or whitening of the fingers upon exposure to cold, and a temporary loss of sensation. The condition can often be prevented by using tools that vibrate less or by insulating the hands from the vibratory surface through the use of impact-absorbing materials.
Much work on bridge RR&D sites involves work on overhead structures. The act of repeatedly raising the hands above the heart level is a risk factor for the development of cumulative trauma and shoulder disorders. Efforts should be made to ensure that work surfaces are between the knee and heart level to avoid awkward postures.
Several potential resources exist for employers who are trying to address ergonomic issues at their jobsites. Workers' compensation insurance carriers often have people on staff who are knowledgeable in back injury prevention and other good ergonomic practices. At the employer's request, an ergonomics specialist from the insurance company can often visit a site or observe a troublesome job to suggest ways of avoiding back injuries or repetitive strain injuries. Some State and Federal OSHA 7(c)(1) consultation programs also provide ergonomics assistance to employers.
SECTION 11: SOLVENT EXPOSURES
The use of solvent-based paints may present health hazards to workers on bridge RR&D sites, especially if the paints are applied by spray apparatus in the containment enclosure. Spray finishing with combustible and flammable materials is also a fire risk. Other solvent exposures may arise from the use of chemical paint stripping agents.
Material safety data sheets (MSDSs) should be reviewed prior to painting or using chemical strippers to determine the solvents present in the products used on the job. Air monitoring should be conducted, especially in enclosed situations, to assess the level of solvent exposures to employees. Any overexposure conditions revealed by the monitoring should be corrected by using the engineering control, administrative control, work practice control, personal protective equipment hierarchy.