> Asthma and allergic diseases cases have risen in recent decades. Plant pollen is considered as the main aeroallergen causing allergic reactions. According to

> Asthma and allergic diseases cases have risen in recent decades. Plant pollen is considered as the main aeroallergen causing allergic reactions. According to available data, urban residents experience more respiratory allergies than rural residents mainly due to the interaction between chemical air pollutants and pollen grains. From: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5941124/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5941124/ There's a lot of research linking the two - particulate matter in the air from burning coal is another allergen related to this.