1. Your manager is dismissive of your concerns about WHS issue in your organisation. You feel that?

Have a formal discussion with the concerned Manager, involve Safety committee if there is one. Ensure these are recorded. Should the Manager still does not cooperate, take the matter to higher authorities in your company..as a last resort you might have to take it up with the relevant Government ministry..
Ensure the risk is genuine and adequately explained.

All the best.