Even with a chimney, an open fireplace is very dangerous because open fireplaces do not burn hot enough to burn cleanly. True, wet coal (and wet wood) make things even worse, but an open open fireplace with bone dry coal (or wood) still doesn't burn cleanly. Burning anything plastic, rubber etc. is still dangerous, even if you don't smell anything.
Closed fireplaces are a bit better but still dangerous, although (as you note) more outside the house than inside. Wood or coal smoke is as dangerous as car exhaust fumes, or worse, in terms of particulate matter, although of course in most urban areas there is more particulate matter from cars than there is from burning wood or coal. But measured levels of particulate matters in rooms with fireplaces are as high as right next to highways, and often people spend more time in those rooms than they do next to highways.
Anyway, lots of people grew up in houses that were heated with coal or wood fires and only a small part of them got cancer from it, and as I mentioned I had one installed last year because as they say 'it's easy to live to 100: just give up everything that makes it worth to live to 100'. It's just that this is one of my pet peeves to bring up to people (not saying you are one of those) who think they're doing the environment a favor by not burning gas but by burning wood - because hey, wood is 'renewable', right? It's quite strange that so few people know about the health impacts of fireplaces, the scientific literature is crystal clear on it yet I know of very few places where residential burning of wood is subject to regulation, let alone prohibited.