What is the relationship between reportable quantities (RQs) and threshold planning quantities (TPQs)?

The reportable quantity (RQ) that triggers emergency release notification (Section 304) was developed as a quantity that when released, poses potential threat to human health and the environment. The RQs were developed using several criteria, including aquatic toxicity, mammalian toxicity, ignitability, reactivity, chronic toxicity, potential carcinogenicity, biodegradation, hydrolysis, and photolysis (50 FR 13468, April 4, 1985).

The threshold planning quantities for emergency planning provisions (Section 302) were designed to help States and local communities focus their planning efforts. The TPQs are based on acute mammalian toxicity and potential for airborne dispersion and represent those quantities of substances that can cause significant harm should an accidental release occur.