It doesn't seem hard to isolate; some people drive every day, and others ride transit. Common sense is often wrong, so it's good to interrogate it. (E.g., maybe

It doesn't seem hard to isolate; some people drive every day, and others ride transit. Common sense is often wrong, so it's good to interrogate it. (E.g., maybe constant low level exposures lead to stronger immune systems and less loss of life? Common sense tells me it's an effect!)