How can you tell if an agent is harmless enough? In 1950, San Francisco had a population over 750,000 (see [0]). There was one death that we know of that seems

How can you tell if an agent is harmless enough? In 1950, San Francisco had a population over 750,000 (see [0]). There was one death that we know of that seems likely linked to this bacteria. How would you find an agent that is more harmless? After all, the effect of this agent seems to be on the order of one in a million. How can you find out an agent causes death one in a million times without testing it on (roughly) a million people? I think that there are valid reasons to be concerned or upset about this test, but that they chose an insufficiently harmless agent is not one of them. [0]: http://www.bayareacensus.ca.gov/counties/SanFranciscoCounty50.htm http://www.bayareacensus.ca.gov/counties/SanFranciscoCounty5...