There has been a lot of research on this, so risks of these have been known for a while. Ones commonly used in the UK aren't likely to be entirely comparable to ones used throughout much of the world like the ones discussed in this National Geographic piece described as:
"The typical cooking fire produces about 400 cigarettes’ worth of smoke an hour, and prolonged exposure is associated with respiratory infections, eye damage, heart and lung disease, and lung cancer. In the developing world, health problems from smoke inhalation are a significant cause of death in both children under five and women."
Yes billions of people use open fires and it's been known to be a health risk for a while now, and some live to old age in varying degrees of health, but there is a higher rate of health problems and deaths associated with long-term exposure to woodburners often depending on factors like ventillation, type of stoves, and so on.
It isn't paranoia or otherwise irrational to discuss how long-term exposure is an issue and to weigh those against the benefits & ways to improve the situation with better technology, just as it isn't such a major issue of instant suffering and death that people need to try to avoid them at all costs. There are ways to balance and reduce risks for those who really want them in their homes or work with them for the benefits they give.