Could it be that people who use fires as their primary cooking source have other disease causing things in common as well.
A blatant attempt to bank bbqs and grills.
More ECO NAZI B LL SH T.
At least non-propane models. More likely target is wood burning fireplaces. They've been after them for years around here in the Pacific Northwest.
Regarding the third world use of open flame cooking. I'm betting it depends more on ventilation and what is used for fuel. In some places they use pretty much anything that burns including animal scat.