Now right off the top, I have to interject, using the word dangerous with the word hamburger seems unfair. Is it because of the calorie content or the possibility of food poisoning? It doesn't say.
Demand for salad has boomed because of healthily eating campaigns. But salad is considered one of the products most likely to cause food-related illness – largely because greens are grown directly in the soil, and some pathogens can only be killed by heat or strong detergents, not just water.
Certain types of bacteria found in the pre-cut salad bags can be almost impossible to kill, Professor Hugh Pennington said, unless the leaves are irradiated – a process the public would oppose.
When specific retailers were included in the analysis, the strongest association with infection was found to be with consumption of ready to eat pre-cut mixed salad leaves from a major supermarket chain.
First off, it may be best to stay away from those bagged salads, they're too expensive anyway and the greens aren't as fresh as buying a whole head of whatever type of lettuce you prefer. Sure you'll have to wash and tear them into pieces but it's a small price to pay. Buy a simple salad spinner and you're halfway done.