Can my fires in my fireplaces be harmful to my health?

Okay so in my house we have 3 fireplaces, and usually have at least one of them in use on saturday and sunday (for long periods of time), sometimes 2 in use at the same time, and they are all linked to the same (large) chimney. Also maybe once on weekdays. I am 16, and i was wondering if this is/could affect my health/lungs, long term or short term. we burn wood with newspaper and twigs, and occasionally a starter log (to make the fire burn better) which could also be harmful? anyway, i'm afraid this is dangerous and we've been doing it for a while now so. Thank you for your answers!