Not exactly true. There were good small studies out of Australia using non-smoking volunteers who claimed they were not effected by second hand smoke.
There were measurable decreases in lung function, measurable clamping of blood vessels, and cancer causing metabolites in their urine.
This was back in the 70’s or 80’s when we couldn’t measure as finely as we can now.
Unfortunately they were never followed up with more larger studies because then it was PC to promote non-smoking. PC decided the science was settled. So politics allowed both sides of the argument on how dangerous second hand smoke is to claim to be correct.
You failed to address the subject.
Are there any studies that show second hand smoke increasing the risk of lung cancer?