Yeast Water

I recently made some yeast water with blueberries and grapes (separately).   I made some bread with the yeast water, resulting in some of the best bread I have ever made. Then I got to thinking, is it safe to make yeast water? Is there a chance of botulism? I assume skip the yeast waster and stick to sourdough starter if it's not safe, but if it's safe, I'd like to continue experimenting.