The hazard
A lot of the safety on a job depends on messages getting through: the morning plan, a shouted warning, a hand signal to an operator, a tag on a switch, a label on a drum. On a crew that speaks more than one language, any of those messages can get lost without anyone noticing. A nod does not always mean someone understood. Clear communication is a safety control, just like a guard or a harness.
The action
Do not ask "Does everyone understand?" and take silence as a yes. Ask people to say the plan back in their own words, or to show you the step. For important messages, use three-way communication: you say it, the other person repeats it back, and you confirm it or correct it. If you do not understand something, say so, and nobody on this crew should give you a hard time for asking.
ASK THE CREW
How can we check that someone understood the plan, not just nodded?
From the talk: Safety communication on mixed-language crews. Read it in full, free, with the questions and the sign-in sheet.