INTRODUCTION TO OCCUPATIONAL HEALTH

Threshold Limit Values

Time-Weighted Average (TLV-TWA)
Short-Term Exposure Limit (TLV-STEL)
Ceiling (TLV-C)

Nearly one-fourth of the substances in the TLV list are followed by the designation "Skin." This refers to potential significant contribution to the overall exposure by the cutaneous route, including mucous membranes and the eyes, usually by direct contact with the substance. This designation is intended to suggest appropriate measures for the prevention of cutaneous absorption.

It is important to observe that if any one of these three TLVs is exceeded, a potential hazard from that substance is presumed to exist.