The eaten one goes through your stomach acid and can be flushed out naturally through the system. The inhaled particles may get stuck in your lungs or worse: absorbed. Lungs are not a through channel. Things absorbed there go to the brain, blood stream, a lot faster. The stuff you spray on plants is usually meant to kill or repel bugs and critters. So won’t be friendly to lung or brain tissue. Possible cancerous too.

some chemistry occurs as a result of burning. dependent on substance it can be worse, or more immediate.

e.g. benomyl [fungicide] https://en.wikipedia.org/wiki/Benomyl

will produce cyanide as combustion product.