Both OSHA and the International Fire Code use the Lethal-Dose 50 (LD50) to establish the toxicity of hazardous chemicals/materials and both use the metric milligram per kilogram of body weight in their assessments. Just so we all have an idea of how small a milligram is…
- One (1) grain of sand weighs 1 mg
- An average-sized ant will weigh around 2 mg
So we are talking about some REALLY toxic materials when they have an LD50 less than 50 mg/kg.
OSHA has four (4) categories of ORAL ACUTE Hazard Categories:
| Exposure route | Category 1 | Category 2 | Category 3 | Category 4 |
|---|---|---|---|---|
| Oral (mg/kg body weight) |
≤ 5 a few drops |
> 5 and ≤ 50 a few drops to a teaspoon |
> 50 and ≤ 300 over 1 teaspoon to 1 ounce |
> 300 and ≤ 2,000 over 1 ounce |
OSHA and the IFC differ when it comes to CAT 1 & 2; as OSHA has a CAT 1 that has a range of 0 to < 5 mg/kg body weight. The IFC uses a median lethal dose (LD50) of 50 milligrams or less per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each. So we can say the IFC has merged OSHA’s CAT 1 & 2’s into their Highly Toxic class.
For something to be a CAT 1 it is supper toxic (my term not an official term). Imagine something the size of five (5) grands of sand per kilogram of body weight killing half the test subjects!
Here are a few of the CAT 1 ORAL ACUTE chemicals:
| Chlorotoxin (the venom of the deathstalker scorpion) | 4.3 mg/kg |
| Hydrogen cyanide (the bitter almond smell) | 3.7 mg/kg |
| White phosphorus | 3.03 mg/kg |
| Strychnine (pesticide) | 1–2 mg/kg |
| Arsine | 3 mg/kg |
| Mercury(II) chloride | 1 mg/kg |
Now there are some really common OSHA CAT 2’s that may surprise you, but these are also considered HIGHLY TOXIC by most fire codes as they are all less than 50 mg/kg of body weight:
| Nicotine | 50 mg/kg |
| Pentaborane | 50 mg/kg |
| Capsaicin (the active component of chili peppers) | 47.2 mg/kg |
| Vitamin D3 (cholecalciferol) | 37 mg/kg |
| Piperidine (food additive) | 30 mg/kg |
| Arsenic trioxide | 14 mg/kg |
| Metallic Arsenic | 13 mg/kg |
| Sodium cyanide | 6.4 mg/kg |
PLEASE be aware, that the values I stated above are mostly derived from SDSs, but when I would search for these I go some wildly varying levels.