Environmental Health
Asbestos Program
The Asbestos Program identifies and keeps records of asbestos containing materials in City-owned buildings and provides consulting to City-owned buildings and provides consulting to City departments regarding all aspects of managing asbestos in buildings. In addition, the Asbestos Program, in compliance with Assembly Bill 3713 of the California Health and Safety Code, issues and updates asbestos notices to city agencies and their employees on a yearly basis. These notices contain summaries of both suspect and sampled asbestos containing building materials that may exist in specific city owned or leased buildings.
The program also answers community complaints and questions, such as concerns about possible unsafe asbestos removal, how to test for asbestos, and what is the risk of exposure to airborne asbestos?
For assistance, please contact the Asbestos Program Manager, David Rizzolo, by telephone at (415) 252-3951, or by e-mail .
Test before you renovate!
What Asbestos Is
Asbestos is the name applied to a group of six different minerals that occur naturally in the earth. They are chrysotile, amosite, crocidolite, tremolite, actinolite, and anthophyllite. Of the asbestos used commercially, over 95% is chrysotile which is white in color and found in serpentine rock. These minerals are made up of fibers that vary in length, and may be straight or curled. They can be so small that they are invisible to the naked eye. Asbestos fibers do not have any detectable odor or taste. Asbestos became a popular commercial product because it is strong, won’t burn, resists corrosion, and insulates well.
Two forms of asbestos
- Friable: A “friable” substance is one that can be crumbled or easily broken to a powder or dust under hand pressure when dry. All friable asbestos-containing materials (ACM), or materials contaminated by friable ACM, are considered hazardous waste. Examples include sprayed acoustical ceilings, paper insulation on furnace ducting, and pipe insulation that is of the soft crumbly type. Friable materials are not a health hazard as long as they remain undamaged and undisturbed.
- Non-friable: Hard materials that are not easily broken, such as floor tile, hard cement-like pipes and panels. Non-friable asbestos-containing wastes are considered to be non-hazardous (regardless of their asbestos content), but are still subject to the labeling requirements of the Cal-OSHA regulations.
How is asbestos used?
Because of the above properties, asbestos has been used in building materials, friction products, and heat-resistant fabrics. Asbestos containing materials are commonly referred to as ACM. The following are examples of products that may contain asbestos:
| Insulation for boilers, tanks, and other vessels |
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Sheetrock (only in specialty uses) |
| Pipe insulation |
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Sealants and coatings |
| Textured or sprayed acoustical ceiling |
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Ceramic tile grout |
| Structural Steel sprayed or troweled-on fireproofing |
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Window glazing |
| Duct insulation |
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Fire-doors |
| Furnace insulating pads |
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Textured paints and street and concrete paint |
| Sheetrock joint compounds |
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Laboratory tabletops |
| Wall and ceiling plaster (non-acoustic) |
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Clutch, brake, transmission components |
| Patching plaster |
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Fuse box liners |
| Asbestos cement (Transite) pipe |
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Fireplace artificial logs or ashes |
| Heater register tape and insulation |
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Conduits for electrical wire |
| Furnace duct insulation |
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Corrosive chemical containers |
| Pipe covering |
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Electric motor components |
| Roofing felts, shingles, patching tars, etc. |
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Heat protective pads |
| Acoustic ceiling tiles (glued-on or laid-in) |
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Paper products |
| Asbestos cement shingles (Transite siding) |
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Textiles (including curtains, stage fire-curtains) |
| Sheet vinyl flooring, vinyl floor tiles and mastics |
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Fireproof blankets |
| Linoleum sheet flooring |
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Specialized theatrical materials |
How is asbestos detected?
Asbestos is not a single chemical entity, but is the name for a group of six hydrated fibrous polysilicates. Because the toxicity of asbestos appears to be related primarily to fiber number and size, modern analytical methods focus on providing information on these parameters as well as on total amount and mineral type. At present, the number and size distribution of fibers in a sample can only be determined by direct microscopic examination. This may be performed using either light or electron microscopy.
The standard method for measuring airborne asbestos fibers in the workplace is phase contrast optical microscopy (PCM). Fibers are collected on a filter and then transferred to a microscope slide where it is dissolved or treated to make it transparent. The residual material is viewed at 400-500X under phase contrast, and a fiber is defined as a length greater than 5 microns and an aspect ratio (length to width ratio) of at least 3 to 1. However, many asbestos fibers are even too small to be seen by this method. Furthermore, this method cannot distinguish other fibers, such as non-hazardous carpet fibers, from asbestos fibers. Consequently, this method is most useful for analysis of samples that are composed mainly of asbestos (as in asbestos materials manufacturing settings), and where a significant fraction of the fibers are large enough to be counted.
Examination of an air sample by transmission electron microscopy (TEM) allows the detection of even the smallest asbestos fibers, many of which are invisible by light microscopy -- reportedly up to 99% of airborne chrysotile fibers. TEM can distinguish asbestos from other fibers as well as measuring their length and diameter. TEM is the preferred method for analysis of all types of asbestos air samples
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