Because the tuna is cooked in the can. It's not raw. Neither are the maintenance workers where they cook it.
http://www.usatoday.com/story/news/...bumble-bee-foods-tuna-worker-cooked/26517161/
WTF? I bet you it was the guy who got cooked's fault. Maintenance workers are required to "lock out" any piece of equipment they are working on. They have a padlock on their belts and the only key. They use this padlock on the main power switch before they work on it.