Are engineered nanoparticles dangerous?

Picked one by one from a mixed channel. Transcript check: both title readers certain; 4 of 5 sampled certain picks confirmed by transcript, none failed. Channel rule: Include only videos whose title and content directly explain a risk-science or technology concept (e.g. 'What is Epidemiology?', 'What is nanotechnology?', 'How Face Masks Work', 'How dangerous is radon', dose-response, risk assessment, 'what does probably causes cancer mean'); exclude holiday/novelty hooks, self-help-style AI rules, advocacy pieces, personal-advice titles like 'Should I get the COVID vaccine?', and the channel intro.