4 ms·
Pollen, I believe, is that they're referring to.
by Afton 6y ago
Pollen, I believe, is that they're referring to.
- nitrogen 6y agoPBS Terra on YouTube recently did an episode about the blue haze over forests in (IIRC) Tennessee. Trees emit VOCs that make the air hazy. The blue haze from trees was being replaced by brown haze from industry. Maybe tree smog is safe to breathe, but trees do create smog in at least some places.