References: 
Centers for Disease Control and Health Prevention (2015) National Health Interview Survey, 2015. Retrieved from:  https://www.cdc.gov/nchs/fastats/asthma.htm
Asthma Respiratory Foundation NZ (2017) Common Asthma Triggers. Retrieved from: https://www.asthmafoundation.org.nz/your-health/living-with-asthma/common-asthma-triggers 
NYC Open Data (2017) 2015 Street Tree Census Tree Data. Retrieved from: https://data.cityofnewyork.us/Environment/2015-Street-Tree-Census-Tree-Data/uvpi-gqnh/data 
New York State Department of Health (2016) Asthma Hospital Discharge ZIP Code Level Data for Counties. Retrieved from: https://www.health.ny.gov/statistics/ny_asthma/hosp/zipcode/map.htm