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Chemicals that are in the Toxic Categories of X, A, and B qualify as "extremely hazardous waste" in the State of Washington. Many laboratory chemicals fall into this definition. If you have extremely hazardous chemicals in your workplace, please know and follow hazardous waste accumulation limits and empty container disposal guidelines for extremely hazardous chemicals. These limits and guidelines are more stringent than for other chemicals.
Use the MSDS of your chemical and the table below to determine whether your chemical falls into Toxic Category X, A or B. These limits apply only for concentrated or "pure" solutions of your chemical.
| Toxic Category Table (WAC 173-303-100) |
| Toxic Category | Fish
LC50 (mg/L) | Oral (Rat)
LD50 (mg/kg) | Inhalation (Rat)
LD50 (mg/kg) | Dermal (Rabbit)
LC50 (mg/L) |
| X |
< 0.01 |
< 0.5 |
< 0.02 |
< 2 |
| A |
0.01 - < 0.1 |
0.5 - < 5 |
0.02 - < 0.2 |
2 - < 20 |
| B |
0.1 - < 1 |
5 - < 50 |
0.2 - < 2 |
20 - < 200 |
| C |
01 - < 10 |
50 - < 500 |
2 - < 20 |
200 - < 2000 |
| D |
10 - < 100 |
500 - < 5000 |
20 - < 200 |
2000 - < 20,000 |
Diluted chemicals
If your chemical is diluted with water, you may take the dilution into account when determining whether your chemical is Extremely Hazardous. If your chemical is diluted, its toxicity is reduced proportionately. For example, if you have a 10% mixture in water of a chemical in the toxic category "X" in undiluted form, it is then in the less toxic category "A". If it is a 1% mixture, it is in toxic category "B", and if it is a 0.1% mixture, it is no longer qualifies as Extremely Hazardous (although it is still of course Hazardous and must be stored, handled and disposed of as such.)
Chemical mixtures
Finally, if your chemical is mixed with other chemicals or in a solvent other than other water, then use the following equation to determine if its "Equivalent Concentration" (EC) is greater than 1% and therefore whether it qualifies as Extremely Hazardous.
EC =sum(X)% + sum(A)%/10 + sum(B)%/100 + sum(C)%/1000 + sum(D)%/10000
where sum(X, A, B, C, or D)% is the sum of all the concentration percentages for a particular toxic category.
For example, a hypothetical waste contains .01% "die-ketone" (Category X), 1% "methyl ethyl death" (Category A) and 98.99% "ace-done" (Category B). The EC would be:
EC=.01%/1 + 1%/10 + (98.99%)/100
EC=.01% + .1% + .9899 = 1.0999%, and therefore the mixture is an Extremely Hazardous Waste.
If you have any questions, please email chmwaste@u.washington.edu or call 206.616.5835.
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