World Trade Center Dust: Safe Work Practices for Conservators

World Trade Center Dust: Safe Work Practices For Conservators
Based on data available as of 12-6-01
Monona Rossol, President, Arts, Crafts and Theater Safety
Kathryn Makos, CIH, Smithsonian Institution Office of Safety and Environmental Management

IDENTIFICATION OF HAZARDS
The dust created from the collapse and subsequent fires at the World Trade Center (WTC) is unlike any you will have encountered in the past. The WTC collapse pulverized 210 floors of the building's cement, glass windows, insulation (asbestos and fiber glass), and other building elements. The fire is now the longest burning commercial building fire in United States history. Smoke from this fire contains the products of incomplete combustion of thousands of plastic computers, miles of vinyl coated wiring, acres of flammable carpet, tons of office furniture, reservoirs of hydraulic oil and other fuels including some contaminated with polychlorinated biphenyls (PCBs), and more.

The dust components of most concern are asbestos (cancer, lung disease), fiberglass (skin, eye, and respiratory irritant, suspect carcinogen), cement and drywall dust (respiratory irritant, caustic, contains silica dust which can cause serious lung disease and cancer), organic particulates from burning plastic such as polyvinyl chloride, PCBs, dioxins and other polynuclear aromatic hydrocarbons, and metals such as lead, copper, iron oxide, and cadmium. In addition, conservators should be aware that there are many other combustion product chemicals, not included in the routine monitoring plans, that may be present in small quantities in this dust.

Bulk analyses of the settled dust samples taken all over the disaster area confirm that the dust is not uniform. The dust blown in through a particular broken window of a building can vary considerably in composition from that blown in the same building a few windows away. The street dust varies in composition from block to block and from day to day.

DUST PARTICULATES
There are two basic size categories for dust particulates: respirable and inhalable.

RESPIRABLE dust particles are generally less than 10 microns in diameter, are invisible, and are capable of settling deep in the lung=s air sacs (alveoli). The smaller the particles, the more toxic they appear to be. For this reason, EPA has separate standards for particles that are < 10 microns and < 2.5 micron particles called "PM10" and "PM2.5." Both sizes of respirable particulates are associated with chronic lung diseases, such as asthma, and with heart problems. However, inhalation of these particles usually does not cause symptoms at the time of exposure, except in people with pre-existing respiratory problems.

INHALABLE dust includes particles that range between 10 and 100 microns. They are visible in the air at high concentrations. They can settle throughout the upper respiratory system from the sinuses through the throat and bronchi, and into all but the smallest of the bronchiole tubes. These dusts often cause immediate symptoms and discomfort including coughing, bloody noses, and bronchitis. In most people, these symptoms resolve when exposure is discontinued or when infections or tissue damage caused by irritation are healed. However, a small number of people will develop permanent respiratory conditions from repeated exposures to inhalable dusts.

Both respirable and inhalable dusts are capable of exacerbating pre-existing conditions such as asthma. Additional exposure to these dusts (especially to the inhalable dusts) occurs by ingestion when they are raised by the lung's clearance mechanisms and swallowed.

RATIONALE FOR PROTECTIVE MEASURES
The acts of moving or manipulating the dusty object or simply walking though a dusted room, can re-aerosolize settled dust. The hazardous particulates can now be inhaled, and are likely to resettle on skin, clothing, hair, and other surfaces. Accidental ingestion is also possible if good personal hygiene is not practiced. Most of the contaminants identified are not easily absorbed through the skin, but many may cause external skin irritation. Therefore, all cleaning and handling efforts need to include dust suppression techniques.

The degree to which these techniques will be needed, as well as the level of personal protective equipment required, will depend on the amount of settled dust present and its known or presumed composition. In the absence of bulk sampling data on the dust itself, it is recommended that one assume that the material contains, as a minimum, asbestos, drywall/plaster/concrete dust, and fiberglass. The advice of an industrial hygienist is strongly recommended in tailoring these safe work practice guidelines to your particular contamination situation. Conservators who choose not to test the dust or have the exposure hazards professionally evaluated (for reasons of cost or time) may be placing themselves and their clients at a certain level of risk. The American Industrial Hygiene Association (AIHA) or ACTS can refer callers to environmental experts in the NYC area (see Reference Section).

REGULATIONS
Before working in an affected building, be sure that it has been approved for re-entry by the NYC Department of Health (212-213-1844) relative to structural integrity and safety of essential (utility) services. Be sure that your cleaning plans do not invalidate the owner's insurance policy conditions and limitations pertaining to the building, object, or art work.

A bulk sample of the dust should be tested to determine if it contains asbestos fibers. Any amount would be reason to take protective measures. However, if the amount detected is greater than one percent of the bulk sample, it is defined as an "asbestos-containing material (ACM)" and is subject to OSHA and EPA regulations regarding warnings, removal, and disposal. The only individuals who are allowed to remove materials containing greater than one percent asbestos are those trained and certified in asbestos removal. There are reports, according to testimony at recent City Council and New York State Assembly hearings, that these rules have been circumvented in the urgency to cleanup businesses and residences in lower Manhattan. Until this issue is clarified by regulators, conservators should use all the precautions required for protection from, and disposal of, asbestos-containing dust. Conservators who are working in areas, or on objects, with asbestos contamination must have some level of training in asbestos removal techniques, through an EPA-certified asbestos training provider, or work through licensed asbestos abatement contractors. NYC Department of Environmental Protection (718-DEP-HELP) can provide names of such certified trainers and licensed contractors.

LAB TESTS
Identification of the dust will help guide your treatment protocols and personal protection strategies. Please refer to "World Trade Center Dust, Its Potential to Interact with Artifacts and Works of Art". If the job is large and the amount of dust is not thick enough to take a bulk sample, we recommend sampling according to ASTM D-5755-95, a micro-vacuum sampling procedure. This test should be done by an industrial hygienist and the sample analyzed by an AIHA accredited laboratory (see Reference Section). Consult with the laboratory as to the type of collection method and analyses available, as there are various methods for crystalline silica, fibers, and organic residues. Fiber analysis should be the basic test, as it will yield information on asbestos and fiberglass. If the number of fibers seen in this test exceed 1000 per 100 square centimeters, then asbestos precautions should be taken.

Bulk testing of asbestos dust samples is not expensive or time-consuming. There are laboratories in the NYC area that can provide Polarized Light Microscopy (PLM) fiber identification on bulk samples in less than an hour and for around $25. More expensive Transmission Electron Microscopy (TEM) is recommended when PLM samples show amounts of asbestos near the one percent level, since TEM can detect smaller fibers than PLM. Contact the AIHA or ACTS for a list of local laboratories with the proper accreditation (see Reference Section).

PERSONAL PROTECTIVE EQUIPMENT & PERSONAL HYGIENE PRACTICES
Minimum personal protective equipment needed to protect against presumed hazardous dusts would include:

* a properly fitted, NIOSH-certified, half-mask air-purifying respirator with P (or N or R) 100 (HEPA-grade) filters;

* disposable barrier gloves (nitrile or vinyl suggested). These gloves should not be re-used.

If it is likely that clothing will be contaminated as well (for example, if the room you are working in has dusty floors, or the objects cannot be handled without body contact), then wear a disposable full-body suit or disposable clothing, and cleanable or disposable shoe coverings. Disposable suits or clothing must not be re-used.

Smoking and the consumption of food or beverages should not be permitted in the work area. A supply of wet-wipes, or a water source for washing hands, clothing and shoes, is needed. Hands, face, and other exposed skin should be washed upon exiting the work area.

SPECIAL NOTE ON PROPERLY FIT-TESTED RESPIRATORS
The effectiveness of a respirator in preventing exposure depends on a) the correct filter or chemical cartridge certified to collect the contaminant of concern, and b) a tight face-to-facepiece seal. The most protective filter for protection against particulates is the P (or N or R) 100, which is made of HEPA (High Efficiency Particulate Air) filter material.

The minimum recommended respirator facepiece is a "half-mask, air-purifying" type, which is the familiar rubber or elastomeric mask. A "disposable dust mask" (now referred to as a "filtering facepiece") cannot easily be fit-tested against the face, and is not the preferred choice. If one has no other option than to use this type of respirator, then it must be manufacturer-listed and NIOSH-certified as AP (or N or R) 100". Nothing (like beards) can be allowed to interfere with the facepiece seal.

OSHA standards require that all respirator users be properly trained, fit-tested, and medically-certified to safely and properly wear such a device. Fit testing is necessary because you cannot judge the seal by how tight it feels on your face. A medical evaluation is also required to determine whether or not you can safely tolerate the breathing resistance caused by respirators and that you can work in this type of hazardous environment. It is preferable that this approval be obtained by a physician who is Board Certified in Occupational Medicine. Such resources can be found through the Association of Occupational and Environmental Health Clinics (see Reference section). The OSHA Medical Evaluation Questionnaire is included in this packet and can be obtained through the OSHA web site (see Reference section).

PREPARING THE WORK SITE
Site contamination must be evaluated before work can commence, and a clean work area created. It is important to remove dust in a clean space in order to prevent re-contamination of the object(s).

* If the area has been closed and stabilized, is not subject to further contamination, and only minimal (barely visible) floor dust is present, then the floor should be HEPA-vacuumed and a plastic sheeting should be used on the floor beneath the object.

* If the general area is still covered with dust and debris or subject to more contamination due to open windows or functioning air conditioning systems (these cannot prevent re-entrainment of PM2.5), then the objects to be cleaned need to be wrapped and removed to a clean work site.

* If the objects are too large or heavy to be wrapped and moved easily, then a filtered containment tent may be constructed along the lines of an asbestos abatement work area with negative pressure air filtration. As mentioned in "Regulations", this type of work is best done by licensed and certified asbestos or lead-paint abatement contractors. NYC Department of Environmental Protection (718-DEP-HELP) can be contacted for licensed firms.

DUST SUPPRESSION AND FILTRATION
Dust suppression, control, and removal methods of choice include vacuuming with a HEPA-filtered vacuum cleaner, or/and wet methods. A conservator's choice of specific techniques will be guided by the type and condition of the object or surface, as well as techniques compatible with containment of abrasive, and potentially hazardous dust. Please refer to "World Trade Center Dust, Its Potential to Interact with Artifacts and Works of Art" for more specific information on the potentially abrasive characteristics of dust components.

* If you choose to use brushes in tandem with vacuum suction, then the brush diameter must be smaller than the nozzle opening.

* Any dry dusting materials, such as cloths or soot sponges, must be dampened after use and sealed in plastic bags.

* Any damp or wet cleaning materials must be sealed without drying. Disposal may be subject to local regulations guiding the disposal of hazardous waste.

* If objects must be handled or cleaned vigorously, such actions should be conducted under local exhaust ventilation or in a full containment enclosure.

DAILY CLEANUP AND DISPOSAL
The work area should be cleaned by HEPA-vacuuming and/or wet wiping at the end of the workday. Alternatively, new polyethylene plastic staging area sheeting could be used and changed daily.

Removal of personal protective equipment should be done in a staging area. While wearing all the recommended personal protective equipment, including your respirator, first use a HEPA vacuum on the body suit to remove gross debris. Remove clothing and gloves by rolling material in on itself to contain any dust. Wet down outside of respirator and remove it. Remove and discard filters. Wash hands and face with soap and water.

The used gloves, suits, sheeting, vacuum bags, and cleaning rags may be considered as hazardous waste by local environmental authorities. Therefore, you will need to dispose of those items in an impervious bag or container, in accordance with local or state regulations. Call NYC Department of Environmental Protection for guidance (718-DEP-HELP).

Arts, Crafts and Theater Safety www.caseweb.com/ACTS or e-mail directly to ACTSNYC@cs.com or call 212/777-0062.

American Industrial Hygiene Association www.aiha.org (for advice and consultant/laboratory lists) (703-849-8888).

Mount Sinai-Irving J. Selikoff Center for Occupational and Environmental Medicine (212-987-6043)