Just do a google scholar search for "marijuana lung damage" or similar and you will find that there is no clear evidence (yet) for correlation between consumption and lung cancer. There is convincing evidence for significant effects related to inhaling smoke - all the usual ones you'll also find with elevated PM2.5 levels such as emphysema, asthma, chronic cough, bronchial inflammation, etc.

You will find disturbing (and growing) evidence linking marijuana use and heart health. Turns out regularly raising your heart rate and dropping blood pressure increases a host of risks for those susceptible to cardiac issues. On the order of 30% more risk for daily smokers.

No doubt inhaling smoke is bad for you, but vaping a couple of times a week is definitely in the noise. You likely have more lung damage and risk to your heart from cooking food in your kitchen without proper ventilation (virtually 90% of homes). If you're smoking a joint a day then the scientific data should give you pause, assuming you're optimizing your life choices for health.

Back to my original point - the equivalent to a joint a day would be several glasses of alcohol a day, and the health impacts are not even comparable (alcohol consumption is far worse overall).