Why is RPE the last resort or last line of protection?

RPE can only protect the wearer. Control measures at source (at the point where hazardous substances are released into workplace air), such as local exhaust ventilation or enclosures, protect all those working in the area.

So, only use or provide RPE as a last line of choice for respiratory protection. Consider other control measures before deciding upon RPE.

https://www.hse.gov.uk/respiratory-protective-equipment/faq.htm#before-providing-rpe-employees

Exactly and a point many cannot seem to understand, most occupational diseases are as a whole, caused simply by ignorance : The time to change this corporate ‘for profit over all’ ideology has well past. You take care sir and try not to worry . As with your elders, I am quite sure the heart failure will get you first ! Live long and prosper dude

That shit is mass produced over here in garages and garden sheds, the only substance that does go into every batch of whatever the manufacturers have to hand is the colouring. Taking it is even more dangerous than giving it a label !