"A forest is a pristine environment..." Hmm, is that really so? The forest air is also full of pollen, fungal spores, viruses and bacteria, all kinds of volatile organic molecules and so on. The terpenes mentioned as problematic come from conifers after all.
Things we had hundreds millions of years to evolve with and adapt too... now we have brake pad dust and haribo strawberry flavored candles
Not just conifers. In Los Angeles, liquidambar trees are planted all over for autumn color, and it turns out that they’re an enormous contributor to smog formation.