Guide to Asbestos

Proper safety measures must be taken when working near asbestos. This PE Fact article will provide you with the information needed to properly protect employees and monitor asbestos levels.

Asbestos is a naturally occurring mineral that's been known to man for centuries. Originally, asbestos was used by the ancient Greeks who weaved it into a cotton-like material. In more recent times, asbestos was frequently used during the industrial revolution because of its structural strength and insulating properties.

During the early to mid 1900s, asbestos became a very popular resource. Asbestos was considered the "miracle mineral," and it had various uses from insulation and fire walls, to Christmas tree decoration. As the century went on, asbestos was sprayed as a fireproofing material in many of the new buildings that were constructed. Approximately half of all the multi-story structures built between 1950 and 1970 contain some sort of sprayed asbestos.

By the late 1960s, information began to surface that removed some of the hype from the “miracle mineral.” Tests showed that asbestos was actually a health risk. By the 1970s, asbestos was regulated by the government, and OSHA's Asbestos Standard, 29 CFR 1910.1001, was published June 20th 1986.

With the current information we have regarding the dangers linked with asbestos, it's very important for those who are exposed to be aware of the health risks that it presents. Wearing proper safety equipment and having a strong knowledge of air monitoring methods is also essential for those working with or near asbestos.

Health Hazards

The air we breathe is filtered through the respiratory system. However, even though air is filtered, some impure substances can still get by and reach the lungs. Once asbestos attaches to the lung wall, large cells called, macrophages destroy most of it. Unfortunately, since asbestos is a mineral fiber, the macrophages are incapable of eliminating it from the lung. The macrophages leave a coating on the asbestos fiber, and scar tissue starts to form around it.

Exposure to asbestos can lead to disease such as asbestosis, lung cancer, and mesothelioma. Asbestosis is identified by fibrotic scarring of the lung. It's a restrictive lung disease that limits lung capacity. Asbestosis is commonly found among workers who have been exposed to great amounts of asbestos over an extended period of time.

Data shows that workers exposed to industrial concentrations of asbestos have a much higher risk of obtaining lung cancer. This risk is compounded for smokers who work with asbestos. Mesothelioma is a cancer of the chest cavity lining. It's the rarest of the three asbestos-related diseases.

It's significant to note that the studies which the hazards of asbestos were based on were conducted with asbestos workers and laboratory animals. Risks associated with low level, non-occupational exposures are not well established.

So how much asbestos is too much? OSHA has established an eight-hour time-weighted average (TWA) permissible exposure limit (PEL) for employees of 0.1 fiber per cubic centimeter of air. They've also established a 30 minute excursion limit of 1.0 fiber per cubic centimeter (1 f/cc). The excursion limit is basically a short-term exposure limit. Workers cannot be exposed to concentrations of asbestos more than 1 f/cc averaged over a 30 minute sampling period.

Employers with workers who are exceeding these exposure levels need to apply engineering or work practice controls to reduce the exposures below the established limits. If these controls are not possible or can't by themselves reduce the exposures to acceptable levels, then respiratory protection, protective clothing and other personal protective equipment (PPE) must be implemented.

Monitoring for Asbestos

Monitoring for TWA asbestos exposure can’t be performed by merely using a colorimetric tube or badge. Appendix A in OSHA's Asbestos Standard identifies the mandatory procedure for conducting asbestos air monitoring. A continuous flow pump capable of delivering a flow rate of between 0.5 and 2.5 liters per minute is required. The sampling medium must be a mixed cellulose ester filter membrane, designated by the manufacturer as suitable for asbestos counting.

The appendix also states, "The preferred collection device shall be a 25-mm electrically conductive extension cowl. The 37-mm cassette may be used if necessary but only if written justification for the need to use the 37-mm filter cassette accompanies the sample results in the employees’ exposure monitoring record."

Once the samples are collected, they must be analyzed and the asbestos particles physically counted by an analytical laboratory. The procedure that the laboratory must follow is also detailed in the appendix.

Respiratory Protection and PPE

If the results of the monitoring verify that the exposure limits are being exceeded, the employer must implement engineering controls and work practices to reduce exposure to acceptable levels. Improved ventilation or a reduction of the amount of dust created, are examples of these control measures.

From an OSHA perspective, respiratory protection is the last option to reduce asbestos exposure. The following is the respirator selection guide found in OSHA's Asbestos Standard:

Respiratory Protection for Asbestos Fibers

Airborne concentration of asbestos or conditions of use

Required respirator

Not in excess of 1 f/cc (10 x PEL), or otherwise as required independent of exposure pursuant to (h)(2)(iv)

Half-mask air purifying respirator other than a disposable respirator, equipped with high efficiency filters

Not in excess of 1 f/cc
(10 x PEL)

Half-mask air purifying respirator other than a disposable respirator, equipped with high efficiency filters

Not in excess of 5 f/cc
(50 x PEL)

Full facepiece air-purifying respirator equipped with high efficiency filters

Not in excess of 10 f/cc
(100 x PEL)

Any powered air-purifying respirator equipped with high efficiency filters or any supplied air respirator operated in continuous flow mode

Not in excess of 100 f/cc
(1000 x PEL)

Full facepiece supplied air respirator operated in pressure demand mode

Greater than 100 f/cc
(1000 x PEL) or unknown concentration

Full facepiece supplied air respirator operated in pressure demand mode equipped with an auxiliary positive pressure self-contained breathing apparatus

Note:
a. Respirators assigned for high environmental concentrations may be used at lower concentrations, or when required respirator use is independent of concentration.
b. A high efficiency filter means a filter that is at least 99.97 percent efficient against mono-dispersed particles of 0.3 micrometers in diameter or larger.

The "high efficiency filters" identified in the selection guide were for many years known as High Efficiency Particulate Absolute (HEPA) filters. With the adoption of NIOSH's 42 CFR 84 standard for particulate filters, 100 class filters will soon be the standard air purifying element for asbestos. Both HEPA and 100 Class filters are acceptable for asbestos. However, it's important to note that OSHA excludes any type of disposable respirator-even HEPA and 100 Class disposables-for asbestos protection.

Under 29 CFR 1910.1001(h), OSHA identifies protective clothing and other PPE. Protective clothing is necessary to keep asbestos fibers from contacting the body, as well as to prevent the contamination of an employee's street clothes. Contaminated street clothing presents an obvious concern because asbestos fibers can be transported on the clothing from the work site to the employee's home.

In terms of appropriate PPE, OSHA suggests coveralls, gloves, head coverings, foot coverings, face shields and vented goggles. A Tyvek full-body coverall with elastic wrists, attached hood and booties, combined with nitrile gloves and ANSI-compliant face shield and goggles are specific examples of the PPE OSHA suggests.

Other PPE such as hard hats and steel-toed footwear may also be necessary depending upon the job function.

References:

Code of Federal Regulations, Title 29, Part 1910.1001 (OSHA Asbestos Exposure Regulations)

Please Note: The information contained in this publication is intended for general information purposes only. This publication is not a substitute for review of the applicable government regulations and standards, and should not be construed as legal advice or opinion. Readers with specific questions should refer to the cited regulation or consult with an attorney.