losis. Available information suggests that most of the benefit of control measures comes from administrative and engineering controls. Modeling studies support the tailoring of personal respiratory protections to the level of risk faced by workers—that is, more stringent protection for those in high-risk situations and less stringent measures for others.

Although control measures have helped to end workplace outbreaks of tuberculosis and prevent transmission of the disease, these measures cannot prevent all types of worker exposure to tuberculosis. In areas with moderate to high levels of tuberculosis, some worker exposure to patients with unsuspected infectious tuberculosis can be expected. Not all infectious individuals have easily recognized symptoms or signs of the disease, so workers may be exposed to them for a period before tuberculosis is suspected, a diagnosis is made, and precautions are initiated. Conscientious implementation of tuberculosis control measures does not guarantee that transmission will never occur, but it appears to reduce risk significantly, especially in high-prevalence areas.

Question 3: What will be the likely effects on rates of tuberculosis infection, disease, and mortality of an anticipated OSHA standard to protect workers from occupational exposure to tuberculosis?

Because the committee had to work without access to the final OSHA regulations on occupational tuberculosis, it could not be certain of whether or how the final standard would differ from the 1997 proposed rule or from the 1994 CDC guidelines. Therefore, rather than concentrate narrowly on individual features of the proposed rule, the committee decided to consider more generally the conditions that would need to be met for a standard to have positive effects on tuberculosis infection, disease, or mortality. It identified three such conditions.

First, implementation of workplace tuberculosis control measures as recommended by CDC and proposed by OSHA must contribute meaningfully to the prevention of transmission of Mycobacterium tuberculosis in hospitals and other covered workplaces. Second, an OSHA standard must sustain or increase the level of adherence to workplace tuberculosis control measures, especially in high-risk institutions and communities. Third, an OSHA standard must allow reasonable adaptation of tuberculosis control measures to fit differences in the levels of risk facing workers.

Overall, the committee expects that the first of the conditions outlined above—that tuberculosis control measures are effective—will be met for hospitals and possibly correctional facilities. Insufficient information is available to assess the effectiveness of control measures in other workplaces.

The committee expects that the second condition will also be met; that is, an OSHA standard will sustain or increase the level of compliance with mandated tuberculosis control measures. A standard is likely to motivate



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