I was going to suggest glyphosate weedkiller e.g roundup, but it is now listed as a human carcinogen. So not worth the risk.
As is toast. And bacon. As above, while clearly you should follow normal precautions, and clearly it’s better to use nothing, this stuff is not regarded as being particularly dangerous or particularly environmentally damaging. Opening myself up for a flaming here but health risks have only ever been associated with heavy users over many years and I wouldn’t be at all surprised to find out that burning the necessary gas/parafin was a lot worse for the world than a dose of glyphosate.
That said, what are you replacing the lawn with? Is it something that means you’ll be covering the area anyway? You might get away with mowing it tight and covering it. Or if you aren’t covering it you might need some other means to keep the weeds at bay anyway.
If you do use glyphosate, you may well get away with a lower concentration. Use it sparingly, in warm weather, and don’t expect to see visible results for some time. Gardeners often use more than necessary.