The researchers discovered that once a tattoo is made, the ink rapidly travels through the lymphatic system and, within hours, accumulates in large quantities in the lymph nodes — key organs of the body’s defense system. Inside these nodes, immune cells called macrophages actively capture all types of pigment. This ink uptake triggers an inflammatory response with two phases: an acute phase lasting about two days after tattooing, followed by a chronic phase that can persist for years. The chronic phase is particularly concerning because it weakens the immune system, potentially increasing the susceptibility to infections and cancer. The study also showed that macrophages cannot break down the ink like they would other pathogens, wich causes them to die, especially with red and black inks, suggesting these colors may be more toxic. As a result, ink remains trapped in the lymph nodes in a continuous cycle of capture and cell death, gradually affecting the immune system’s defensive capacity.
I think if these effects were universal and as serious as the paper makes out,, we'd have noticed them waaay sooner.
To be fair, it’s possible it has been a significant factor to weakend immune systems all along; it was just now that the connection/link with tattoo ink was identified. Not a scientist obviously, just spitballing.
And yet things like asbestos, lead, and smoking all took way longer than you'd expect (given they were a lot more universal).
And yet humans have been tattooing themselves since the dawn of recorded history - significantly longer than any of those other things were around before their harm became evident.