I’ve got some comments on two bacteria-related columns, although they were posted more than ten years apart.
The conclusion reached in “Do microwave ovens kill bacteria?” was that nuking your 4-hour-old pizza for an amount of time short enough that the pizza is still edible afterward doesn’t kill off the bacteria. However, I would disagree with this conclusion based on the results. My premise is that we shouldn’t be concerned with getting rid of -all- bacteria on the pizza; we should be concerned with reducing their numbers to roughly the ballpark of how many there are on fresh pizza, which is presumably considered perfectly safe to eat. If the fresh pizza produced 11 colonies and the 4-hour pizza produced 28, then 17 colonies for the 30-second sample represents a substantial reduction from the un-nuked 4-hour pizza, bringing it closer to the fresh pizza if not all the way there. Nuking it for a full minute produced only 3 colonies, which is much, much less than the fresh sample. So apparently, nuking the pizza actually is effective in reducing the bacterial population. My next question, then, would be: how old can the pizza be so that nuking it for a minute reduces the bacteria population to roughly what would be found on a fresh one?
Next, the comparison with a fresh pizza is already an unnecessarily high standard for pizza cleanliness. After all, plenty of people eat pizza that’s been sitting around for well upwards of four hours with no ill effects, so presumably those 28 colonies still represent a safe level of bacteria. So, if I leave the pizza sitting out for 8 hours and then nuke it for 45 seconds, is that roughly like eating 4-hour pizza without nuking it? What if it’s a day old and I microwave it for a minute?
Of course, it’s possible that some bugs are more susceptible to damage in the microwave than others, and that the ones that make you sick could be more or less susceptible than average. But that’s a separate issue.
Along similar lines, the column “Does flushing the toilet cause dirty water to be spewed around the bathroom?” discusses all the various ways fecal bacteria get spread around, from remaining airborne for a hours after toilet flushes to contamination from your dirty underwear. The ubiquity of said bacteria (I remember a Daily Show segment from a few years ago that found trace amounts of E. coli on a voting booth curtain) and the fact that most people spend most of the time not being sick indicates that, again, there is some safe level of exposure. Notwithstanding the number of cases of food poisoning from home contamination, we spend some amount of time breathing post-flush bathroom air, not to mention public restroom air; and this guy’s demonstrated that we come into regular contact with this stuff all the time because we live an inherently germy existence. So rather than worrying about toilet aerosols getting germs on our toothbrushes, which doesn’t seem to be a public health risk even if it’s gross to think about, why don’t we accept that certain levels of bacteria are safe and normal (assuming no immunodeficiency disorders or other medical conditions, etc) and worry about the sources of contamination that are likely to cause harm? I bet I reduce my risk much more by replacing my kitchen sponge more often than by pouring bleach (which comes with its own health risks anyway) all over everything in sight.