How does ethylene affect humans?

Ethylene enters the body primarily by inhalation of air containing ethylene, but can also enter the body by dermal contact with ethylene. Ethylene is of low toxicity to humans and exposure to ethylene is unlikely to have any adverse health effects. However, inhalation of air containing extremely high levels of ethylene may lead to effects including headache, drowsiness, dizziness, nausea, weakness and unconsciousness.

Ethylene is a plant hormone. It is released as a gas and speeds up the ripening of fruits.