Only chemicals listed in the "Catalogue of Hazardous Chemicals (2015 Edition)" and marked as "highly toxic" are considered highly toxic chemicals.

According to the Catalogue of Hazardous Chemicals (2015 Edition), highly toxic chemicals refer to chemicals with severe acute toxicity hazards, including artificially synthesized chemicals and their mixtures, natural toxins, as well as chemicals with acute toxicity that can easily cause public safety hazards.

Severe acute toxicity threshold: Acute toxicity category 1, which meets one of the following conditions: rat experiment, oral LD50 ≤ 5mg/kg, transdermal LD50 ≤ 50mg/kg, inhalation (4h) LC50 ≤ 100ml/m3 (gas) or 0.5mg/L (vapor) or 0.05mg/L (dust, mist). The experimental data of transdermal LD50 can also be obtained from rabbit experiments.