Regional Air Quality

DNREC continually works to improve air quality through planning, pollution controls, and monitoring for National Ambient Air Quality Standards (NAAQS). However, pollution from states upwind of Delaware can have an effect on our air quality as well. Since Delaware cannot regulate pollutant sources outside its boundaries, solving this problem requires regional cooperation between state and federal government agencies. 
Current data estimates that only 10% of the ozone pollution impacting Delaware is actually generated from within the state (Docket ID No. EPA-HQ-OAR-2015-0500-0459). The remaining 90% of the polluted air is largely out of DNREC’s regulatory control. The Department seeks to find ways to keep our state in compliance by examining the combination of air pollution problems generated locally and regionally. The Environmental Protection Agency (EPA) generates an Air Quality Index forecast for the region to highlight areas of potential concern.
Delaware's Airshed
Nitrogen compounds (or oxides) contribute to the formation of ozone and particulate matter, both related to serious health risks, and can themselves be a threat to human health and vegetation.  This map shows the airshed for the Delaware Bay, outlined in red, specifically for nitrogen oxides. Nitrogen oxides transported through the atmosphere from within this area may be deposited in the Delaware Bay. This means that activities occurring in many of the states surrounding Delaware, especially those within the red circle, have an impact on our air and water quality.
Delaware's Watershed
The smaller area, shaded in red, is the watershed for the Delaware Bay, which is also greatly affected by upstream activity. Nitrogen deposited into water bodies through precipitation or runoff from land can act as a source of nutrients in aquatic environments. Too much nitrogen can lead to nutrient pollution and harmful algal blooms that may negatively affect aquatic life in the area.
Regional Greenhouse Gas Initiative (RGGI)
RGGI is the first mandatory market-based program in the United States to reduce greenhouse gas emissions. It is a cooperative effort among Delaware and eight other states to cap and reduce carbon dioxide (CO2) emissions from the power sector. RGGI is successfully reducing carbon pollution, while continuing to support economic growth and grid resiliency. The RGGI states have experienced more than 45% reduction of carbon pollution in the power sector since 2005. In 2016, $436.4 million in RGGI CO2 allowance auction proceeds were invested regionally in programs including energy efficiency, clean and renewable energy, greenhouse gas abatement, and direct bill assistance. Over the lifetime of the projects, these investments are projected to provide participating households and businesses with $1.7 billion in energy savings, while avoiding the use of 7 million MWh of electricity and 30.4 trillion Btu of fossil fuels.
Regional Comparisons
The charts below compare Wilmington, Delaware's air quality in 2017 against the national standards and nearby monitored regions in Maryland, New Jersey, and Pennsylvania for fine particulate matter (PM2.5), carbon monoxide (CO), sulfur dioxide (SO2), and nitrogen dioxide (NO2). In 2017, these criteria pollutants were all below the NAAQ Standards (the red line on the charts). To find out how Delaware compares to the region for other pollutants or years, explore the EPA's Monitor Values Report. For a better understanding of how these standards are measured, use the EPA's NAAQS Table read DNREC's Annual Air Quality Reports.
The PM2.5 values represent the average of daily samples collected in a calendar year. When multiple monitoring stations are present in one city, the site with the highest value is shown.
The CO values represent the highest 8-hour daily averages collected in a calendar year. When multiple monitoring stations are present in one city, the site with the highest value is shown.
The SO2 values are calculated for each site by looking at the highest 1-hour average for every day sampled, then arranging them from highest to lowest and choosing the value that is above 99% of the rest. For 365 days, this would be the 5th highest value. When multiple monitoring stations are present in one city, the site with the highest value is shown.
The NO2 values are calculated for each site by looking at the highest 1-hour average for every day sampled, then arranging them from highest to lowest and choosing the value that is above 98% of the rest. For 365 days, this would be the 7th highest value. When multiple monitoring stations are present in one city, the site with the highest value is shown.
Are we speaking another language? Try the air quality glossary.

Page reviewed 5/14/19