According to the New York City Department of Health and Mental Hygiene, air quality in NYC is getting better. Here at AIRE, we hypothesized the opposite last summer. Based on a very unscientific survey of our own asthma responses and perceptions of visibility in the city, we suspected that summertime air quality had been on the decline in recent years (2014-2015). To test this hypothesis, summer undergraduate researcher Silvia Vina Lopez gathered Air Quality Index (AQI) data for NYC from 2000-2015, and data on criteria pollutant (SO2, CO, NO2, O3, PM) concentrations from 9 NYSDEC monitoring sites around the five boroughs. Here are some highlights of her findings:
- Overall, air quality has been improving since 2000. Importantly, there has clearly been a steady decrease in the number of “bad air days”. Since 2000, the number of days categorized as “Unhealthy for sensitive groups,” “Unhealthy,” or “Very unhealthy” has been on the decline.
- Since 2008, the number of “Good” air quality days has had an overall upward trend, but there indeed has been a sharp decrease in “Good” days since 2013. Since “Moderate” air quality is also pretty good in the big scheme of things, this trend may be subtle to perceive as you’re walking the streets of NYC unless you have asthma (like us) or think about PM 2.5 a lot (also like us).
To dig deeper into these trends, Silvia investigated the frequency with which each criteria pollutant exceeded the 24 h NAAQS standards. She found that SO2 violations decreased between 2004-2009 and have stayed low. The City attributes this trend to changes in heating oil regulations. On the other hand, the frequency of PM2.5 violations increased over the same time period and has remained elevated since 2009. This value decreased somewhat between 2007-2015, consistent with the data presented in the City’s survey, which covered 2008-2014. However, the average number of PM2.5 violations 2009-2015 was still significantly higher than 2000-2005.
The verdict: air quality in NYC is not bad and getting better in general. However, work needs to be done to reduce PM2.5 violations, and hold on to the gains made between 2008-2014. One possible source of elevated PM2.5 not mentioned in the City’s report is secondary organic aerosol formation: the formation of PM2.5 in situ, due to gas-phase reactions of oxidants and volatile organic compounds (which can be natural or man-made).
Question: An alert on my smartphone told me today is an Ozone Action Day. What is that and how does it affect me? – D.E., New York, NY
Answer: An Ozone Action Day is a day when the concentration of ozone gas in a particular area is predicted to be higher than healthy levels. Ozone Action Days generally coincide with high Air Quality Index days. Ozone is one of the main urban air pollutants that we regulate, due to its potential negative impacts on human health, alone or in combination with other pollutants such as particulate matter. Ozone can irritate the lungs and cause respiratory symptoms, especially in sensitive groups such as children, the elderly, and those with respiratory problems such as asthma or COPD.
On Ozone Action Days it is generally a good idea to avoid exercise outdoors if possible. Children’s outdoor play time should be limited on those days, especially for children with asthma. You can do your part to help keep ozone levels down on Ozone Action Days by taking measures to reduce your emissions of NOx and volatile organic compounds (VOCs): limit electricity use and use of gasoline vehicles.
Pregunta: Mi hija tiene asma. ¿De qué manera la contaminación del aire afecta a su salud? – M.N., New York, NY
Respuesta: Las personas asmáticas son muy sensibles a los efectos de la contaminación del aire. Al respirar el aire contaminado, esto puede desencadenar o empeorar los síntomas del asma. El ĺndice de Calidad del Aire (AQI) es una medida que nos dice que tan ‘saludable’ es el estado actual del aire que respiramos. El AQI se calcula por los niveles de unas sustancias presentes en el aire, las cuales pueden afectar la salud humana, por ejemplo el ozono y la materia particulada. Un nivel AQI sobre 101 no es saludable para la gente asmática, mientras que para los adultos con un buen estado de salud y sin asma, un nivel de AQI sobre 151 no es saludable.
La Prof. McNeill también tiene asma y en los días con alto AQI, ella no se siente bien y usa más el inhalador. Cuando ella estudiaba en la universidad Caltech, cerca de Los Angeles, la calidad del aire fue muy mala, peor que hoy, y esto la motivó a estudiar la química atmosférica.
Question: What does the air quality index measure, and what values correspond to ‘good’ air quality? – T.L., Manila, Philippines
Answer: Good question! The Air Quality Index (AQI) is calculated based on the concentrations of different pollutants in the air, including atmospheric particulate matter, ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide. According to the U.S. EPA, an AQI of 0-50 corresponds to “good” air quality. AQI of 51-100 is “moderate.” When AQI is 101-150, the conditions are “unhealthy for sensitive groups” such as asthmatics, children, and the elderly. AQI of above 151 is considered unhealthy for everyone.