Answer:
An ethics review board would most likely be concerned about the physical risk to the participants.
Explanation:
The physical risks would be the ethics review board's main concern since Matt want to get participants to get a tattoo but this experiment and activity may have repercussions on the individuals that they might not even be aware of.
Since a tattoo is permanent and could in some cases lead to complications, it is not ethical to ask participants to get it. Their health may be at risk.
