Steam, irradiation and fumigation
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Almost every spice reaching a commercial buyer in the United States has been treated. Sellers often have no idea which method was used on theirs, and it is a question with consequences for flavor, for labeling and for what you can claim.
What the trade means by treated
In this industry treating means applying a microbial reduction process. It is not cleaning, it is not drying and it is not fumigating for insects in storage. It is a deliberate kill step, and under a modern food safety plan it functions as a preventive control for pathogens.
Why it exists
FDA identifies Salmonella as a hazard to be considered for all herbs, spices and seasonings, alongside Bacillus cereus and pathogenic E. coli. The uncomfortable part is what dryness does to it: Salmonella survives in dried spices for years, is harder to kill in a dry environment than a wet one, and takes only a small dose to make someone ill.
A dry product is not a safe product. It is a product where the organism cannot grow but does not die either, which is a different and less reassuring thing.
The three methods
Steam. Saturated steam under controlled conditions. Accepted everywhere, compatible with an organic claim, and the gentlest on appearance. It does cost volatile oil, because it is heat and moisture applied to a product ruined by both.
Irradiation. Effective and cold, so flavor survives better than steam. It carries a labeling obligation and a consumer reaction that is out of proportion to the evidence, which is a marketing problem rather than a safety one.
Ethylene or propylene oxide. Chemical fumigation. Widely used, effective, and incompatible with an organic claim. Not permitted in some export markets.
What you have to say on the label
This is where it bites. Irradiated ingredients carry disclosure obligations, and organic claims are unavailable if the material was treated with ethylene oxide. If you are buying ground spice and reselling it in a jar, the treatment happened before you bought it and you may still be the one making the claim.
Ask the method before you buy, in writing, and keep the answer with the lot record. It is the one attribute of your product that you cannot determine by looking at it.