The dutch agency responsible for food safety has recently found that a lot of sesame seed from india is contaminated with ethylene oxide.

Growers and distributors in india apparently use it a lot as an insecticide.

Ethylene oxide is a gas at room temperature so traces of it in food are always very small, but as sesame seeds are used in a lot of products, repeated exposure to it cannot be ruled out.

It's probably wise to only buy sesame seed products that have some "certified organic" label on it. And not some fancy label that is made up by the producer itself, but one that actually means something.