In December 2000, the coalition filed suit against ACGIH claiming the organization is a standards-setting body and that its TLV for refractory ceramic fibers is unreasonable and unjustified.

The two groups have agreed to clarify the meaning of the TLV for refractory ceramic fibers. According to the clarification, TLVs "are developed as guidelines to assist in the control of health hazards — (not) for use as legal standards and ACGIH does not advocate their use as such."

"No TLV, including the TLV for refractory ceramic fibers, represents a judgment that other exposure guidelines, which may be based on other parameters, are appropriate or inappropriate," according to the clarification. "(TLVs) are not fine lines between safe and dangerous exposures, nor are they a relative index of toxicity. TLVs should not be used by anyone untrained in the discipline of industry hygiene."

The coalition has advised ACGIH that it has developed additional data regarding refractory ceramic fibers and will submit that data for review by ACGIH. ACGIH has agreed to review this data.

ACGIH's TLVs still face another legal challenge that threatens their existence — producers and users of Trona have filed suit seeking to prohibit ACGIH from publishing a Trona threshold limit value.