Exactly, you need to rely on universal truths rather than symbols. The article has an example very similar to yours. They picture a man next to a small tree when he is exposed to the radiation, and then collapsed in agony next to a larger version of the same tree.

They additionally convey a "contamination" of radioactivity that stays with the man over time.

http://www.wipp.energy.gov/picsprog/articles/WIPP%20Exhibit%...