Abstract
Certain changes are described in the operations of the Threshold Limits Committee that have occured in the recent past as a result of increased interest in its actions. Although the basic tenets on which it operated a decade ago still hold, some new findings in environmental medicine are resulting in new concepts of the relation of inhaled irritants to health. A new procedure of notification of the Committee's intentions with solicitation of data is described that is hoped will make for a greater annual number of limits in which industry has a voice. Two types of limits, and their basis for selection and application are clearly defined for the first time.