HEALTH AND SAFETY FOR HISTORIC STRUCTURES PRESERVATION By Karen Yager Fellow: American Institute for Conservation Conservator in Private Practice Methods and materials used in the field of Historic Structures Preservation have the potential to adversely affect great numbers of workers, as well as the public at large. The containment or removal of asbestos, for example, presents severe health risks for those not properly trained in its identification and handling, while freed airborne asbestos particles constitute a major public health threat. Similarly, the broad range of cleaning products - such as those used in the removal of graffiti, masonry grime, or wall paints - may contain toxic or otherwise hazardous ingredients, which can pose risks both to personnel and the environment during their application and disposal. Some of these occupational and environmental hazards are researched and regulated by federal agencies such as the Occupational Safety and Health Administration (OSHA), National Institute for Occupational Safety and Health (NIOSH), and the Environmental Protection Agency (EPA), as well as by various state and local agencies. Local agencies also grant building permits and inspect premises for fire, electrical, and health code violations. In addition to governmental regulations, there are health and safety guidelines published by unions, trade associations, and recognized professional standard-setting organizations. Sometimes these are more stringent than government regulations. It is advisable to follow the most protective recommendations, rather than rely on the minimum protection provided by government regulations. Workers' compensation claims and lawsuits could result if an employee, subcontractor, student or member of the public is injured on the site or becomes ill as a result of overexposure to toxic chemicals. In the case of lawsuits, liability could extend to conservators, who are often assumed to be the on-site experts, as well as to the owner of the structure, overseeing architects, construction and engineering firms, etc. The wide variation in contractual relationships on a work site can also complicate the liability question. Failure to consider health and safety issues may affect workers' health, work performance, liability, cost, and work schedules. This data sheet provides basic information on health and safety issues and resources in historic structures preservation. It is written for architecture and art conservators, architects, construction and engineering personnel, and for owners of historic structures. HEALTH AND SAFETY PLANNING: A PROCEDURAL OVERVIEW Health and safety issues should be addressed systematically throughout the planning and execution stages of a historic preservation project. An essential step towards implementing this would be to appoint a health and safety officer or committee, whose role it is to oversee these issues, research applicable regulations and laws, and to act as liaison with other workers, outside inspectors, industrial hygienists, and additional experts when necessary. The health and safety officer or committee should immediately begin to identify areas of potential danger such as toxic on-site materials and restoration products, hazardous working conditions, dangerous equipment and procedures, and potential sources of fires and accidents. Preliminary analyses for example, might detect the presence of asbestos in wallboard insulation materials or caulking compounds, or the presence of lead in wall paints or gesso. Special consideration must be given to the large volume of site materials and chemicals utilized since precautions followed while working with smaller quantities may be totally inadequate for large scale use. Possible cumulative effects of exposures to chemicals and synergistic interactions between different chemicals must also be recognized. A health and safety program should include provisions for training a foreman or other responsible individual and all workers in chemical hazards, emergency procedures, the use of personal protective equipment, etc. Often this training is mandated under federal or state laws (i.e. State Right-To-Know Laws). A. PRELIMINARY SURVEY AND ANALYSIS OF SITE HAZARDS (1) Structural Hazards. Conduct a general survey of the structural hazards of the site with the assistance of a structural engineer. * Recognize rotted, weakened, or unsecured ceilings, floors, staircases, walls, beams or other load-bearing elements. * Determine the soundness of the materials on which work is to be performed. Radiography, soundings, test-cuts etc., may reveal deep cracks, wood density inconsistencies (due to rot or infestations), and friable masonry products behind deceptively coherent surface layers: the removal of multiple layers of paint or corrosion products, for example, may significantly destabilize delicate structures such as corroded fretwork, causing them to collapse or break. Similarly restoration of a ceiling or wall fresco or statuary frieze may require reinforcement of supporting walls or other substrates. * Seek engineering approval before considering the removal of stained glass windows or panels, statuary columns, entablature, false walls, "modernization" etc. Historic buildings have collapsed during these procedures. (2) Material Hazards Conduct a preliminary survey of on-site hazardous materials. * Identify asbestos and other dangerous substances in insulation, drywall, caulking compounds, plaster, dusts, soils, and structural materials (e.g. stone such as serpentine, steatite, etc.). * Test for lead and other toxic pigments in paints on masonry or wooden walls, backs of murals, etc. * Test for the toxic residual products of pesticides, preservatives, and fire retardants. Toxic residues such as DDT, cyanide salts and arsenic, may be found in wooden structures and on corroded metals. Be aware that fumigated objects or buildings may continue to outgas toxic gases for days and sometimes even months after the fumigation has been completed. (3) Fire Hazards Note inherent fire hazards on the site. Inventory flammable structural materials, such as dried-out wood, textiles, or paper products (tapestries, wallpapers, etc.), overloaded wiring, construction material wastes, solvents, chemical wastes, general debris, sawdust, etc. A local fire department may be able to help with this process. Smoking should not be permitted on the site, especially if flammable solvents are used. B. PREPARATORY RESEARCH AND INVESTIGATION Once the appropriate procedures and materials for the project have been selected, health and safety information should be gathered for the products, methods, and equipment which will be used. Applicable government and industry regulations and guidelines should be researched. (1) Product Information Collect occupational safety and health information from the appropriate manufacturing and construction industries and from within the conservation field. Several suppliers of chemicals used in building conservation have prepared safety manuals or information booklets; these can provide some essential safety information. Major manufacturers and suppliers may also have experts on staff willing to advise conservators about the safe use of their products. Specific safety information must be requested; otherwise it is generally not provided, particularly for raw materials or common consumer products. Be especially careful when interpreting product literature as health and safety recommendations are often obscured by advertising and promotional information. Rarely, for example, will demonstration photographs ever show a worker wearing appropriate protective equipment even during chemical spraying operations. (2) Labels Product labels can be sources of health and safety information. Labels on laboratory chemicals usually provide detailed ingredient information, even listing small impurities. In practice, though, most field materials are industrial grade or consumer products whose labels are far less informative, at times providing no listing of ingredients and only trade names for the products. Some products marketed especially for the conservation trade do list primary ingredients but not contaminants. Health warnings on labels are usually restricted to acute exposure warnings. Chronic hazards such as cancer, birth defects, and effects of repeated low dose exposure are usually not listed. Under current consumer product laws (labeling provisions of the Federal Hazardous Substances Act), products with chronic hazards may even be labeled "non-toxic". However informative the label may appear, it is still necessary to obtain additional information in the form of a Material Safety Data Sheet (MSDS). (3) Material Safety Data Sheets (MSDSs) An MSDS should be obtained on every toxic or suspected toxic product used on the site, with workers having access to these MSDSs and training in their interpretation. They may be obtained by writing to the manufacturer, distributor, or importer of the product. A MSDS should list all ingredients in the product - including contaminants - as well as physical data ( boiling point, vapor pressure, etc.), fire and explosion hazards, effects of acute and chronic exposure, first aid recommendations, reactivity data (decomposition products or dangerous reactions), protective equipment and ventilation requirements, and methods for spill control and waste disposal. Some proprietary products do not list ingredients, claiming trade secrets; some of these, however, have been analyzed by museums and university conservation laboratories. The widespread presence of hazardous chemicals in conservation, as well as the need to preserve and protect the integrity of the materials treated, presents a very strong case to pressure suppliers into providing complete ingredient data on their products. Right-To-Know laws in some states and the OSHA Hazard Communication Standard mandates this information (except for proven trade secrets). (4) Government Regulations Once the site and product hazards are assessed, all applicable governmental regulations should be researched. For example, OSHA has standards for airborne exposure to many chemicals, regulations concerning scaffolding, ladders, power tools, abrasive blasting, general emergency procedures, et al. C. SAFETY EQUIPMENT NEEDS ASSESSMENT An ongoing assessment must be made of all related health and safety equipment needs, choosing equipment appropriate to each hazardous procedure. Safety equipment will offer protection only against the particular substance or procedure for which it was specifically designed. Training in the equipment's limitations, use, and maintenance is essential. Sources of safety equipment can be found in various safety directories such as Best's Safety Directory. (1) Respiratory Protective Equipment Conservation workers often work very close to their materials, and the concentration of chemical vapors or respirable dusts in the worker's breathing zone may be of a magnitude higher than even a very short distance away. This can be true outdoors as well as indoors. A variety of types of respirators may be necessary on a restoration site, including air-purifying respirators with filters or chemical cartridges, powered air-purifying respirators, or even supplied-air respirators (air-line or self-contained breathing apparatus). The choice of respirator depends on the toxic substance being used and its concentration in the worker's breathing zone. * If respirators are required for restoration work: OSHA requires that there be a written respirator program which includes provisions for proper selection, training, fit testing, respirator care, and more. * Neither filters nor chemical cartridges are designed to work at high concentrations of contaminants (usually over 10 times the OSHA Permissible Exposure Limit). Filters may allow significant breakthrough of the dust, fumes, or particles, and chemical cartridges can saturate and cease to function in minutes at high concentrations. * There are many substances for which there are no NIOSH-approved cartridges, often due to lack of adequate odor warning properties. Examples likely to be encountered by conservators include methanol, acrolein (from burning wax vapors), nitric acid, nitrogen oxides, isocyanates (from foaming and casting polyurethane), etc. Carefully research the limitations of available cartridges and filters. * Air-supplied (rather than air-purifying) respirators should be used (1) for protection against substances for which there are no approved cartridges, (2) when concentrations of contaminants will exceed the air purifying respirator's capacity, or (3) in situations that are immediately dangerous to life or health. For further information see the CSA data sheet "Respirators" for information on the selection and use of respirators. 2. Face and Eye Protection Equipment. Any number of conservation procedures may cause face or eye injury from physical, chemical, or radiation (welding, black light, etc.) agents. A variety of face and eye protection devices may be necessary. All face and eye protection should meet standards of the American National Standards Institute (ANSI Z87.1). * Face shields and goggles. There are a wide variety of types of chipping, welding, and chemical-resistant goggles, available for use with or without eye glasses, or made with appropriate corrective lenses. Face shields, having mesh or plastic windows, may be used in place of, or in addition to goggles, where appropriate. * Welding hoods and goggles. Welding operations require the use of helmets, goggles, and/or face shields. ANSI has recommendations and guidelines for appropriately graded filter lens shades for this equipment. * Abrasive blasting helmets. OSHA regulates the use of blasting equipment and abrasive blasting respirator hoods. Blasting hoods or helmets, which protect the workers' head and neck, must be used for continuous protection where toxic materials are released during blasting. Respirable dusts and mists (when water or chemicals are used) may be released from both the abrasive agent (sand, carborundum, glass beads, ground slag, shells, etc.), and from the blasted surface (masonry dusts, lead or other paints, corrosion products, etc.). A particulate filter respirator may be worn during small outdoor blasting operations if no toxic dusts or mists are generated. A face shield and goggles should always be used in conjunction with these respirators. Check appropriate OSHA regulations, as well as local regulations regarding abrasive blasting. (3) Other Personal Protective Equipment. * Wear appropriate work clothing. A worksite is a construction site. Work clothes suitable for such sites include at the least coveralls, heavy boots (possibly with steel-tipped toes, and hard hats or other head coverings. * Wear chemically resistant clothes when working with solvents or corrosive chemicals. There are no `all purpose' impervious materials; appropriate clothing must be chosen for each class of chemicals used. Neoprene rubber gloves, for example, may not be resistant to aromatic hydrocarbons, but are likely to provide adequate protection for dilute acids, alkalis, alcohols and ketones. Glove manufacturers will provide detailed information on glove resistance to various substances. For further information see CSA publication Glove Selection. * Wear washable or disposable coveralls, heavy duty puncture-and slip-resistant gloves, shoe covers, and head protectors during heavy dust- generating finishing operations such as sanding, or grinding. If the dusts and debris created are toxic, for example from stripping of lead paint or sanding of epoxy consolidants, workers must use special precautions. * Wear full body suits (space suits) for extremely hazardous processes such as large-volume acid cleaning. * Use proper hearing protectors (ear muffs or plugs) for protection in noisy environments. (4) Ventilation Equipment. Adequate ventilation must be assured throughout the work site. Open windows are not sufficient for situations involving high humidity, stagnant air, or toxic contaminants. Air conditioning units cannot be used to provide fresh air as they function primarily to recirculate room air (even on an exhaust setting). When feasible, contain the work area (with curtains, tarps, moveable walls, etc.), and install an exhaust fan of appropriate power at the site. Ensure sufficient intake air to replace that which is exhausted. Work as close to the exhaust area as possible. Use local exhaust systems such as portable flexible duct exhausts or spray booths when appropriate. If significant quantities of flammable solvents or dusts are exhausted, the system must be explosion-proof. Locate exhaust outlets so that contaminated air cannot re-enter the worksite or any other undesirable area. Exhaust fans may be useful in some outdoor operations. Refer to the CSA book Ventilation or consult with a ventilation specialist. Check the EPA and local regulations regarding substances which may be lawfully exhausted into outdoor air. (5) Fire Protection Equipment Choose the right type of fire protection equipment. * Store flammable chemicals safely. Provide approved safety cans, flammable storage cabinets, waste disposal cans, etc. * When transferring flammable liquids from drums to smaller containers: make sure that the drums are grounded and that the drums and smaller containers are bonded to prevent build-up of static electricity and the possibility of a fire. * Have smoke alarms, sand, water hoses with adequate water pressure, and appropriate fire extinguishers in case of fire. Workers should be trained to use these fire extinguishers. * For further information on fire prevention, refer to the COH Data Sheet Fire Prevention in the Conservation Laboratory. (6) Safety Devices, Tools and Storage Equipment. * Keep hand and power tools and their safety guards in proper working order. Brace heavy equipment to avoid electrical, safety and stress hazards. * Use proper extension cords and ground fault interrupters where necessary. * Motors, blowers, and vacuum attachments should be spark-proof, with proper filters and dust collectors. * Scaffolding, staging, etc., must be equipped with steel cable or other appropriate chemical-resistant safety rigging. * Use approved safety belts, lanyards, harnesses, etc. * Store tools, equipment, supplies, etc. in closed cabinets. (7) Emergency Medical Equipment. Establish a first aid station, with portable shower and eyewash bath, or fresh running water supply. Stock first aid supplies for chemical burns, shock, accidental ingestion, etc. and have blankets available. Install a telephone at the work site if possible. For other aspects of emergency preparedness, see the CSA data sheet "Emergency Plans for Museum Conservation Laboratories". (8) Facilities for Personal Hygiene Provide a changing area where contaminated clothing may be hosed down and removed, special disposal bins for contaminated clothing, and a separate storage area for uncontaminated clothing. Note that OSHA has special requirements for hygiene on sites where lead or asbestos are involved. D. HAZARDOUS OPERATIONS: ONGOING SITE EVALUATION The Health and Safety Officer should conduct regular inspections of the work site: assess air quality, monitor hazardous operations and ensure that safety precautions are followed. (1) Monitor Hazardous Procedures. * Assess Air Quality. Air sampling equipment should be used to monitor project site air quality whenever large quantities of hazardous substances can become airborne, when there is exposure to hazardous airborne chemicals in enclosed environments, or whenever fumigants are or have been used. In some instances OSHA regulations require air monitoring ( e.g. asbestos removal). COH, industrial hygiene consultants and state OSHA consultative services are some sources of information on air sampling techniques and equipment. * Avoid worker fatigue. Physical stress is inherent to some work procedures. Working on hard to reach areas or oddly shaped surfaces, working on one's back or above one's head, or performing repetitive movements such as injecting, scraping, painting, or cleaning, may cause severe strain or fatigue. Strain can lead to physical impairment (repetitive strain injuries such as carpal tunnel syndrome or tendonitis). Fatigue is also a leading cause of workplace accidents. Schedule frequent short breaks, and rotate tasks when possible. * Control potential fire hazards. Welding and soldering equipment, heat guns and plates, torches, portable kilns, etc. are potential sources of burns and fire. Such equipment has caused major site fires by igniting site debris, dusts inside hidden air spaces in walls, etc. Flammable dusts and debris may also be generated during finishing operations such as sanding or blasting. Wood dusts, cured resin dusts, and the like should be wet down or equipment such as appropriately filtered vacuum cleaners used for collecting these dusts. (3) Post warning signs These should be present when dangerous materials, procedures, and conditions exist. Signs should also be posted indicating the locations of safety and fire fighting equipment and temporary exits. "No Smoking" signs should be posted in appropriate locations. Federal and state laws may mandate other work site signs such as notification of Right-To-Know laws. (4) Develop safe work schedules Schedule work with personnel and environmental safety in mind. For instance, no worker should be allowed to do hazardous work alone: develop a buddy system instead. Develop and post time charts for hazardous operations. Everyone on the work site should know when and where chemicals are in use, and the approximate time required for completion of the operation, including curing or drying time. Incompatible work procedures should not be scheduled simultaneously unless they are sufficiently separated by distance. For example, large volumes of acids, alkalis, or solvent chemicals should not be in use at the same time. Similarly, electrical or mechanical equipment should not be used while flammable dusts and chemicals are present. In one instance, a major fire on a historical site was apparently started when electrical sparks, created during sanding operations, ignited varnish dust and solvent vapors. (5) Establish written emergency procedures Formalize procedures for dealing with accidents, fires, medical emergencies, chemical spills and other emergencies. Post emergency telephone numbers for hospitals, fire departments, poison control centers, etc. Develop abort procedures (plans for shutting down hazardous processes in response to an emergency), and evacuation procedures. Practice drills are recommended. For further information refer to CSA Data Sheet, "Emergency Plans For Museum Conservation Laboratories". (6) Dispose of waste materials safely Select safe locations for the on-site storage of hazardous waste materials, prior to disposal. Inspect periodically to ensure that the materials remain isolated and completely contained. Be certain to comply with federal, state, and local regulations concerning hazardous waste disposal. E. MEDICAL ASPECTS OF A HEALTH AND SAFETY PROGRAM. A formal health and safety program should have provisions for medical surveillance and accident/illness reporting and investigation. (1) Develop a health monitoring or medical surveillance plan. This should include a pre-employment physical and periodic re-examinations. OSHA regulations, in fact, require medical surveillance and retention of medical records for exposures to certain substances including lead and asbestos. Workers with pre-existing medical conditions which might put them at higher risk should be informed of these risks. Pregnant or nursing women in particular should be informed of any hazards and special precautions that might be needed for them to work safely. (See CSA data sheet "Reproductive Hazards in the Arts and Crafts".) Consultations with an occupational health specialist may be necessary. (2) Report and investigate work-related accidents and illnesses. Record-keeping is advisable to protect workers' health and employers' liability. It is also required by OSHA under certain circumstances. These records are also invaluable for future research, assessment and correction of hazards in the conservation industry. Workers should include these records in their personal medical files. For further information contact OSHA and refer to the CSA data sheet "Health and Safety Programs for Conservation Laboratories". MATERIALS AND PROCESSES IN HISTORIC STRUCTURES PRESERVATION This section discusses some of the materials, products and procedures found in historic structures preservation that have been found to pose the greatest potential hazards. A. ASBESTOS Asbestos materials will be present in most 20th century buildings built between 1945-1975 and in many buildings repaired or renovated in the mid-20th century. Any operation that generates airborne asbestos particles on the site is a major hazard. Repeated inhalation of asbestos may cause asbestosis (fibrosis or scarring of the lungs), lung cancer, mesothelioma ( an always fatal cancer of the lining of the chest or abdominal cavity), lung cancer and possibly intestinal cancer. Smokers are even more likely to get lung cancer if they work with asbestos. These diseases might take 20-40 years to appear after first exposure. Asbestos-containing materials in buildings are found especially in the following types of products: * Surfacing materials - troweled or sprayed on walls or ceilings; scratch and finish coats (stuccos, plaster, ornamental plaster, cement surfaces). * Pipe and boiler insulation - around hot and cold pipes, boilers, ducts, and tanks; the insulation is often wrapped with canvas outer layers. * Miscellaneous materials - such as wallboard or partitions, ceiling and floor tiles, acoustical tiles and boards, decorative plaster panels, asphalt roofing shingles and tile, vinyl tiles, fireproof textiles, wallpapers and sealers, grouts and caulking compounds. Conservators may encounter asbestos in otherwise safe environments in the following situations: * Exposing walls, ceilings or floors; behind murals, wallpapers, plaster friezes, floor coverings, etc.; removing or treating the verso of these objects. * Consolidating friable materials or removing efflorescence products in locally damaged areas. * Removing grouts,etc. during repointing operations. * Drilling, sanding, removing or otherwise disturbing modern additions such as acoustical boards or wallboards. All suspect materials should be analyzed for asbestos by a reputable laboratory (for instance, those certified by the American Industrial Hygiene Association). Conservators should not undertake this analysis by themselves. If asbestos is found, experts must be consulted and all of the latest federal, state, and local regulations must be followed. Asbestos abatement (encapsulation, removal, or containment) and disposal of asbestos waste must be done by trained professionals. Constant air monitoring during abatement will be required. Abatement costs for contaminated work sites are high. Penalties for violations of asbestos regulations are also often high; costs to life and health, over the long run, are much higher. B. SURFACE COATING MATERIALS (1) Lead Paint Until 1976, nearly all outdoor paints contained lead pigments. Lead was also a common ingredient in indoor paints, artists' gesso, and adhesives for backing murals and oil paintings. Today, artists' paints, metal priming paints, and boat and automobile paints may all still legally contain lead. Lead can affect the kidneys, blood, reproductive system, gastrointestinal system, and nervous system. In severe cases of lead poisoning, such as has been found in architectural conservators using torches to remove lead paint, brain damage (encephalopathy) has occurred. All suspect paints and surface coatings should be tested for lead. If lead is present, check federal and local laws regarding its removal. The EPA has rules for exhausting lead dust and fumes into outside air and for disposal of lead paint waste. The Department of Housing and Urban Development issues lead removal guidelines and lead abatement regulations. Precautions include: isolation of the work area by taped plastic walls, keeping the work area under negative pressure so that lead dust does not escape from the area, wearing protective clothing, respirators,etc. (2) Paints Containing Other Toxic Pigments Toxic paint pigments are primarily those containing toxic metals (such as arsenic, cadmium, manganese, or chrome) or certain organic pigments. These organic pigments may l) be inherently toxic (e.g. toluidine red which can cause cyanosis; 2) contain highly toxic impurities (e.g. phthalocyanine blues and greens containing PCBs); or 3) break down into highly toxic or carcinogenic chemicals (e.g. benzidine pigments). Many historic paints - especially those with rich chromas in the reds, yellows, and oranges - often contain toxic pigments. Workers should be aware of the dangers and precautions associated with cleaning or removing specific paints or pigments. For example, acid or alkaline cleaning methods could result in the release of highly toxic arsine gas from paints containing arsenic pigments. Several instances of arsine exposure have recently been documented among conservators. 3) Natural Resin Coatings and Varnishes Natural resin varnishes and shellacs are formulated from organic resins dissolved in alcohols, turpentine, and other solvents. They may also contain additives such as pigments for color (arsenic trisulfide has been used in some amber shellacs), anticorrosive agents, or mold inhibitors. Some linseed oil varnishes may contain small amounts of lead driers. These organic varnishes and shellacs have traditionally been used for coating operations. Hazards of varnish removal are usually associated with the organic solvents used. 4) Rust and Corrosion Inhibitors Rust control and anti-corrosion coatings which are applied to metal surfaces often contain highly toxic pigments such as zinc, lead, potassium and strontium chromates, as well as hazardous oxides, amines and carbonates. If sprayed, inhalation can be a serious hazard requiring special precautions. Removal of these coatings may also be hazardous, and can in additoin seriously destabilize degraded metals. C. SURFACE COATING TREATMENTS: CHEMICAL CLEANING Cleaning removes grime, accretions, stains, and other unwanted materials from a surface by methods ranging from gentle eraser cleaning of wall paper and plaster to pressure hose cleaning of masonry. Industrial cleaners used in large-scale restoration procedures often contain dangerous organic solvents, acids, and alkalis, which can dissolve, corrode, liquify, burn, fume, precipitate, emulsify, bleach, or otherwise destabilize both organic and inorganic materials. These are the characteristics required for the removal of surface deposits, ranging from soot, grease, tar and rust to the countless graffiti products including pencil, egg, lipstick, marking pens, and spray enamel. These are the same characteristics which make the cleaners capable of causing burns and respiratory system damage; dissolving clothing; pitting metal, masonry and glass; harming plant life, and the like. Some products may be so hazardous that their drifting on the wind during outdoor cleaning projects may harm other workers, by-standers and/or the environment. The number of liability cases involving outdoor cleaning agents is steadily increasing. Carefully read the product literature for cleaners. The advertised and promoted "safety" of the products often pertains only to the materials on which they will be applied, not to the worker. Never use these products without researching the hazards carefully. Pay particular attention to all the MSDS recommendations for use of protective clothing, ventilation, and respiratory protection. It is important to recognize any hazards associated with diluting or mixing cleaners, or the generation of toxic decomposition products from the cleaner's reaction with the substances on the surface. For example, dilution of some industrial strength acid and alkaline cleaners can generate excessive heat, and acid cleaners on certain metal surfaces can liberate flammable hydrogen gas. The hazards of the main categories of chemical cleaning agents are discussed in the following sections. 1) Organic Solvent Cleaners Organic solvents are used in cleaning procedures for the removal of natural and synthetic resins, gums, oils, tars, and other organic matter. They are also diluents, thinners and vehicles for any number of chemicals. All organic solvents are toxic to some degree and many are flammable and explosive. Acute exposure to most organic solvents can cause intoxication, dizziness, loss of coordination, headaches, nausea, and other symptoms of narcosis. In addition they may cause respiratory, skin, and eye irritation. Long term exposure may, depending on the solvent, damage the liver, kidneys, brain and central nervous system, the peripheral nervous system, the reproductive system, and the heart, blood and bone marrow. Some solvents are so toxic that they should be avoided. Examples are benzene (which causes leukemia), carbon tetrachloride (causes severe liver and kidney damage, possible liver cancer and fatalities in association with drinking alcohol), and chlorinated hydrocarbons such as methylene chloride, tri- and tetra-chloroethylene (which are suspected carcinogens causing cancer in animals). Glycol ethers ( eg. "cellosolves" ) are used in solvent-cleaning products, or as additives in other types of cleaners (including water-based products). These solvents can be inhaled and absorbed through the skin. Research on animals indicates that many glycol ethers can damage the developing fetus and impair the reproductive system of both men and women. They should be used with caution. Since it is virtually impossible for conservators to avoid dangerous solvents, a general rule would be to use the least toxic solvent in any chemical class. Solvents in the same chemical class have similar working properties. In addition, all the precautions for avoiding exposure to solvents should be followed (See CSA data sheet "Solvents Used in Conservation Laboratories"). 2) Acid Cleaners Acid cleaners are highly corrosive and can severely burn the skin, eyes, stomach and mucous membranes, and cause severe systemic damage depending on type of acid, concentration, amount absorbed, and route of entry. The concentration of the acid is more critical than the volume. Inhalation of acid gases can cause respiratory irritation and even chemical pneumonia. Repeated or prolonged skin contact with even dilute acid solutions can cause dermatitis. Masonry and metal cleaners are often concentrated solutions of aqueous mineral acids, such as hydrofluoric, muriatic (hydrochloric acid), and nitric acids, or blends of these with other inorganic and organic acids such as oxalic, phosphoric, sulfuric (oleum), perchloric or chromic acids. All of the above may be found in proprietary mixtures, with additions of surfactants, chelators, and solvents. Muriatic acid (30-35 per cent hydrochloric acid in water) is a very common masonry and graffiti cleaner. Hydrofluoric acid (in an aqueous solution of up to 70 per cent), is another commonly used product. Hydrofluoric acid is an extremely dangerous material in all concentrations, and can cause severe fulminating burns and respiratory tract irritations which can be fatal. It is readily absorbed through skin, and reactions to dilute solutions may be delayed for many hours. Chromic acid and perchloric acid are corrosive because of their oxidizing potency as well as their acidity. They also present severe fire and explosion hazards on contact with organic compounds and other oxidizable substances. Acetic acid is found in some cleaners. Acetic acid should not be mixed with oxidizing acids because of possible reactions. 3) Alkali cleaners Alkalis are used as cleaners for wax, soot, grease and grime on stone and masonry, wall coverings, painted surfaces, and for the removal of graffiti products. Detergents and household cleaners also are alkaline to varying degrees. Alkali (caustic) cleaners generally contain carbonates or hydroxides of potassium, sodium, barium or ammonium, along with various stabilizers, surfactants and additives, which may include organic solvent additives (sometimes the glycol ethers). Among the highly corrosive alkalis are lye or caustic soda (NaOH), caustic potash (KOH), and washing soda (sodium carbonate). Some highly alkaline phosphate detergents, for example trisodium phosphate, may produce injuries similar to that of lye. The hazards of alkali cleaners are more dependant on concentration than dose. Damage may range from caustic burns and tissue cell dehydration in the case of mild skin contact to fatal burns from extensive skin contact, and blindness when splashed in the eyes. Accidental inhalation of powdered caustics can cause deep burns of the upper respiratory system as the granules tend to adhere to the mucous membranes. Barium alkalies such as barium carbonate or hydroxide can also cause cardio-vascular and central nervous system effects. Ammonium hydroxide (ammonia water) differs from the other alkalis in its volatility. Ammonia gas, even in very low concentrations, is extremely irritating to the eyes, skin and respiratory tract, and may cause contact burns. Ammonium hydroxide solutions of 5-10% for household use and 27-30% in water for commercial use are common. Mixing ammonia with chlorine bleach preparations (hypochlorites) leads to the formation of ammonium trichloride, a poisonous gas. Alkalis containing hypochlorites (chlorine) serve as cleaners as well as disinfectants, bleaches and deodorizers. Concentrated hypochlorite solutions of sodium, potassium, calcium, etc. are corrosive to the skin and mucuous membranes. Alkalis tend to stabilize the hypochlorites; acids cause them to decompose, releasing chlorine gas. Addition of hypochlorite bleaches to solutions of phenolic disinfectants may generate toxic polychlorinated phenols. Alkali cleaners may react with some metals to produce hydrogen gas, which is explosive and flammable. Alkalis should never be stored in metal containers. Metal-containing pigments (e.g. arsenic pigments), strong acids, and some oxidizing compounds may also react with alkalis. Workers using acid or alkali cleaning methods must be equipped with protective clothing, goggles, gloves, boots, and all other safeguards against acid or alkaline burns. If toxic pigments such as arsenic are present, air-supplied respirators may also be necessary. D. SURFACE COATING REMOVAL METHODS Health, safety, and the protection of the integrity of the surface must all be considered when choosing paint or varnish removal methods. The choice is often a difficult one, since there are some hazards inherent in virtually all removal methods. 1) Heat gun and plates These are currently used to soften and remove paints and adhesives, and to dry or cure newly applied adhesives and consolidants. Some of the equipment can cause fires and thermal burns. If the temperature is high enough, they may also liberate toxic decomposition products from paints, waxes and adhesives. Lead fumes can also be created by heat guns. Although the amount is less than those produced by torches, there are several documented cases of lead poisoning from this source. Lead fumes are particularly hazardous because they remain in the work area as an inhalable or ingestible fine dust long after the work is complete. If these methods are used, provisions for isolation of the work area must be made; proper ventilation, respiratory protection, and scrupulous clean up must be followed. 2) Torching or burning These methods should rarely, if ever, be used due to the large volumes of lead, cadmium, and other toxic fumes they may liberate from toxic pigments. Using torches on lead paints has resulted in many cases of lead poisoning over the years. Other major hazards associated with these methods are fire and damage to surfaces. 3) Mechanical sanding and abrasive blasting Power sanding and abrasive blasting (dry, chemical or aqueous), and other similar treatments can generate toxic and flammable dusts and debris (from woods, paints and pigments, cured resins, masonry, chemical-soaked slag,etc.). Such finishing operations on lead-painted surfaces is prohibited in some areas. 4) Hand scraping Although these methods generate less dust than power tool sanding, scraping is still a hazard if lead or other toxic pigments are present in the paints. All the precautions for isolation of the work area, respiratory protection, and clean up must be followed. 5) Solvent-based stripping Paint strippers usually contain some of the most toxic solvents, including suspected carcinogens such as methylene chloride. All of the precautions necessary for working with solvents should be followed. If lead or other toxic substances are present disposal of the paint waste must be done in accordance with regulations. 6) Acids and alkalis Workers using acids and alkalis for removal of surface coatings must wear appropriate protective clothing and equipment as discussed. E. CONSOLIDANTS AND BINDING MATERIALS Consolidants and binders used in conservation are generally formulated for structural replacement, that is, to restore cohesion or adhesion to damaged, delaminated or fractured materials. Some are also used as sealants or adhesive vehicles. 1) Epoxy Resin Systems Epoxy resins find widespread use as adhesives and consolidants in historic structures. Earthquake-ravaged buildings worldwide have been stabilized with massive infusions of epoxy adhesives and sealers. The structural stabilization of plaster ceilings to metal lathe by means of epoxy flooding techniques, or the consolidation of damaged load-bearing members such as masonry walls, columns or arches by means of high pressure injections, may involve the application of thousands of gallons of epoxy material. Epoxies are also used as wood consolidants. Epoxies are thermosetting plastics formed by the two- component reaction of a resin and a substance which starts the polymerization reaction, usually referred to as curing agents or hardeners. Often epoxies are modified for specific characteristics with fillers, plasticizers, or diluents. Cured resins are usually polymerized condensation products of epichlorohydrin and bisphenol-A or other polyhydric compounds. The curing agents include aromatic and aliphatic amines, organic peroxides, polyamides and amides, polymercaptans and phenolic materials, and organic acid anydrides, such as phthalic or maleic anydride. Epoxies and their curing agents are potent sensitizers, causing allergic reactions (usually dermatitis or asthma) in over 50% of industrial workers exposed to them, according to some studies. The cured or set epoxies are relatively non-sensitizing and are not known to be hazardous to handle, except by extremely sensitized individuals. Epoxy dusts, however, generated in such finishing operations as grinding or sanding, may be lung, eye or skin sensitizers or irritants, especially if the dust contains dangerous filler materials or uncured components. Freshly hardened resins, in fact, may not be completely cured for days (or even weeks) after hardening, depending on temperature, humidity and other factors. Large amounts of epoxy dusts are also a fire hazard. The amine and acid anhydride curing agents are caustic, and many of them can cause severe burns, irritation and sensitization. The aliphatic amines set at room temperature; however, the reaction is strongly exothermic, and produces vapors of toxic amines and phenols. Modifiers, fillers, and solvent diluents may further add to the hazards. Diluents may include many different solvents, such as methylene chloride, toluene or diglycidyl ethers. Evidence of CNS and liver damage associated with epoxies may be due to the solvent components. Diglycidyl ethers are associated with reproductive hazards in animals. Epoxies may be modified with fillers, including asbestos, fiberglass, silica flour, and diatomaceous earth. There is some evidence that one epoxy resin, epichlorohydrin, may be carcinogenic. Investigate thoroughly the particular epoxy used. Follow all precautions to avoid skin contact and inhalation of vapors or dusts. Scrupulous personal and work-site cleanliness should be practiced including immediate clean up of spills and disposal of contaminated clothing. Large volumes of epoxy should be mixed in an enclosed system such as a pressure-injection pump mixhead or with local exhaust ventilation. 2) Alkoxysilanes: Silanes, Siloxanes, Ethyl Silicates Silicones Alkoxysilanes used in conservation include the materials known as silanes, siloxanes, ethyl silicates and silicones. They are formulated primarily as masonry consolidants and water-repellent agents. In smaller quantities, they are used in statuary conservation in the execution and preservation of murals and frescoes, as well as for some treatments of wood, paper, textiles and basketry, and as binders for paints and other coatings. Most of the proprietary stone consolidants in use since the 1970's are based on alkoxysilane mixtures. Although health and safety information and evaluation is scarce for these chemicals, the evidence suggests that they are systemic poisons, particularly by ingestion and inhalation, and may variously cause injury to skin, eyes, kidneys, respiratory, circulatory and central nervous system. Symptoms may include nausea, abdominal pain, vomiting, dizziness, confusion, visual disturbances, leading to blindness, coma and death with severe overexposure. Some of these symptoms can be caused by methanol, which is a basic diluent in some silanes. Methanol is also produced by some of these materials in contact with air, and is also quickly formed in the stomach if the materials are ingested; remember that ingestion may occur while clearing the throat and swallowing expectorate. Certain organofunctional silanes are known to cause gene mutations and animal cancers under laboratory conditions. The terminology for alkoxysilanes can lead to great confusion for anyone seeking health and safety information about specific chemical materials. The nomenclature is vague, both in the literature and in the proprietary products themselves. Alkoxysilanes used in conservation treatments refer broadly to three types of interrelated chemical families: ethyl silicates, siloxane (actually ethoxysiloxane, which is a partly polymerized ethylsilicate), and silane ( organofunctional silane). Both the ethyl silicates and siloxane may be described variously as silicon ester, silicic acid ester, and silicic ether. Silicone is a popular name for siloxane, but has been used when referring to silane. Various catalysts, accelerators, etc. are mixed with these materials, and may include acids, alkalis, amines, alcohols, cellosolves, and organometallic compounds, many of which vaporize during the curing process. The alkoxysilanes and their additives are all toxic, but each may have different toxicological properties. Similarly, their physical hazards vary; some pose unusually severe fire and explosion dangers (for example, generating vapors which can be ignited by static electricity at locations distant from the point of application, due to vapor migration). The MSDSs for these materials must be studied very carefully, since many individual warnings and notes sometimes appear on them. For example, some alkoxysilanes must not be diluted with water; they will give off explosive and toxic vapors. 3) Acrylics and Methyl Methacrylates Acrylic resins, and particularly methyl mathacrylates, are used extensively in Historic Structures Preservation as consolidants, adhesives, media, and protective finishes. Applications of these synthetic polymer plastics include paint media, varnishes, stabilizers for frescoes, murals and paintings, wood finishes, metal coatings, plaster and masonry consolidants, weatherproofing. Methacrylate polymers are the basis of lucites, rhoplexes, elvacites, plexiglass and acryloids. The acryloids are among the most utilized materials in the field, with large volume applications, particularly for statuary and consolidation of exterior stonework. Esters of acrylic and methacrylic acid are monomer liquids that polymerize to form thermoplastic resins. The cured resins are essentially inert and nontoxic, although they may cause occasional allergic skin reactions, probably due to unreacted monomers. The liquid forms and the monomers are quite hazardous, as are the solvents and catalysts used with them. Through inhalation or skin contact, these can cause burns, sensitization, and such central nervous system (CNS) disturbances as nausea, vomiting, headaches, lowered blood pressure. The polymerizing catalysts, such as benzoyl peroxide, can cause burns and blindness on skin and eye contact. Normally they are available in solution; in pure form they are highly flammable and explosive. Methylmethacrylate monomers and polymers can be dissolved and diluted in a great variety of solvents including chlorinated hydrocarbons, glycol ethers, ketones, alcohols, and more. Since acrylics and methyl methacrylates can be successfully formulated with so many different solvents, use solvents which are the least toxic in their class. This is most critical when working with large volumes of material. For example, acryloid dissolved in chlorinated hydrocarbons is a widely used consolidant for exterior stone. Most of these chlorinated hydrocarbons (such as perchlorethylene and carbon tetrachloride), are suspected carcinogens as well as liver and kidney toxins, and should be avoided. If possible, formulate the consolidants in methyl chloroform (1,1,1- trichloroethane). This solvent appears to be less toxic than other chlorinated hydrocarbons (although it can be fatal when used in enclosed spaces without proper precautions). 4) Foams Foams have been used for the consolidation of plaster, the replication of masonry elements such as terra cotta cornices, and for the stabilization and encapsulation of materials during transfers, for example, during the removal of a fresco from its substrate. The polyurethane foams are 2-component systems, with one of the components an isocyanate. Inhalation of isocyanates, even in small concentration, may produce progressive disabling respiratory illness, characterized by breathlessness, pulmonary distress and coughing, with asthma-like allergic reactions. Inhalation of large amounts can cause severe respiratory irritation and chemical pneumonia. Isocyanates are also irritating to eyes and skin. They are especially hazardous if sprayed. Local exhaust ventilation or positive pressure air- supplied respirators should be used when working with these consolidants. Appropriate protective clothing should also be worn. F. CHEMICAL PEST CONTROL MEASURES There are many different pest control procedures in use. Most of these, such as fumigation, must be undertaken by certified professionals. Vapors, gases and particulates from these substances can be highly toxic and proper precautions must be taken to avoid exposure. These measures can include air sampling to determine safe reentry times, proper protective equipment, ventilation, emergency planning etc. Pesticides and fumigants that can leave residues in the treated materials are of particular concern. DDT, arsenic, and cyanides have been widely used in the past and could pose present risks to workers. Fumigants such as ethylene oxide which are easily absorbed by organic materials may continue top outgas for weeks or months after the fumigation, posing risks to workers handling these objects. For further information, see the CSA data sheet "Safe Pest Control Procedures for Museum Collections". REFERENCES American Conference of Governmental Industrial Hygienists. Threshold Limit Values for Chemical Substances and Physical Agents in the Work Environment. Cincinnati (1984) Updated regularly. American Mutual Assurance Alliance. Handbook of Organic Industrial Solvents. 5th ed. Chicago (1980) Babin, Angela and McCann, Michael. "Fire Prevention". Center for Safety in the Arts, 1988. Casarett, L.J. & Doull, J. Toxicology, The Basic Science of Poisons, 2nd Ed. McMillan, New York (1980 ). Department of Housing and Urban Development. Lead-based Paint Removal: Final Rule and Proposed Rule. Federal Register 24 CFR Part 35 (August 1986) Environmental Protection Agency. Guidance for Controlling Asbestos-Containing Materials in Buildings. EPA 560/5-85-024. Office of Pesticides & Toxic Substances Washington, D.C. (June 1985). Gosselin, R.E., et al. Clinical Toxicology of Commercial Products, 5th Ed. Williams and Wilkins, Baltimore, MD (1984). McCann, M. Artist Beware: The Hazards and Precautions in Working with Art and Craft Materials. Watson-Guptill, New York (1979). McCann, Michael. "Emergency Plans for Museum Conservation Laboratories" Center for Safety in the Arts, 1986. McCann, Michael. "A Health and Safety Program for Conservation Laboratories". Center for Safety in the Arts, 1985. McCann, M. "Respirators" Center for Safety in the Arts, 1986. Michael, Herbert. Ionizing Radiation Protection for Conservation Laboratories. Center for Occupational Hazards, 1986. Nadel, Brian. "Chemical Storage and Disposal in the Conservation Laboratory". Center for Safety in the Arts, 1985. National Safety Council. Epoxy Resin Systems Data Sheet. 1-553-81. Chicago (1981) Occupational Safety and Health Administration. Construction Industry 29 CFR 1926/1910. OSHA 2207. U.S. Department of Labor (1985). Occupational Safety and Health Administration. General Industry 29 CFR 1910, OSHA 2206. U.S. Department of Labor (1981) Patty, F.A. (Ed.). Industrial Hygiene and Toxicology, Vol II, 3 part, 3rd Ed. Interscience Publishers, New York (1982). Peltz, Perri and Rossol, Monona. Safe Pest Control Procedures for Museum Collections. Center for Safety in the Arts, 1983. Rossol, Monona and Netburn, Alice. Hazards of Dyes and Pigments for Museum Personnel. Center for Safety in the Arts, 1986. Rossol, Monona. "Solvents in Museum Conservation Labs". Center for Safety in the Arts, 1985. Clark, Nancy, Cutter, Thomas and McGrane Jean-Ann. Ventilation. Nick Lyons Books, 1985. The data sheet has been made possible with the assistance of public funding from the Architectural Planning and Development Program of the New York State Council on the Arts. c Copyright Center for Safety in the Arts 1986.