What is Air Pollution?

Air pollution occurs when the air that sustains all life becomes contaminated with harmful substances and toxins. This pollution, originating from within the watershed region and well-beyond it, is one of the greatest threats to the Chesapeake Bay.

What Types of Air Pollution Are There?

Several types of airborne pollution impact our treasured Chesapeake Bay and our local rivers and streams:

Nitrogen Oxide Pollution: NO₂ is a highly reactive gas that gets into the air when fuel is burned. We find elevated levels of nitrogen oxide pollution in regions with a high density of fuel-burning vehicles as well as areas with power plants. According to the EPA, NO₂ affects both humans and our environment. Here in the watershed, we see the impact of NO2 in acid rain which harms the Bay’s ecosystem.  

In fact, each year more than 85 million pounds of nitrogen pollution—about one-third of the bay’s total yearly load—comes from the air.

Sulfur Dioxide Pollution: SO₂ emissions occur when vehicles and heavy equipment burn fuel with high sulfur content. In addition to contributing to damaging acid rain, SO2 can damage the growth of plants that sustain the Bay’s ecosystem.

Mercury Pollution: Elemental and inorganic mercury are released into the air when coal, oil, or wood are burned; when medical waste is burned; or when mercury is used by industrial plants and factories. That mercury ends up in our waterways and can reach toxic levels, particularly in the tissue of fish and shellfish. For this reason, the consumption of certain fish prone to high levels of mercury should be limited. According to a 2020 study by the United State Geological Survey, the most contaminated fish in the Chesapeake Bay watershed include striped bass (rockfish), walleye, largemouth bass, and flathead catfish. 

What Are the Causes of Air Pollution?

Pollutants created and dispersed into the air by power plants, smokestacks, and vehicle exhaust are eventually washed out of the air by rain.

While air pollution has many sources, they share one critical origin: humans. The influx in air pollution in and around the Bay can be traced back to a corresponding influx of people in the region.

It is estimated an additional 157,000 people move into the region every year, bringing with them more vehicles and more demands for energy from power plants. And as a result, more nitrogen, sulfur, and mercury pollution will damage our waterways.

But it’s not just people who move to the watershed region that impact air pollution. The air over the Chesapeake region travels here from as far away as Canada in the north and Indiana and Kentucky in the west. This "airshed" is 570,000 square miles—more than nine times the watershed itself. In September 2017, the Maryland Department of the Environment filed suit against the U.S Environmental Protection Agency (EPA) for not responding to its petition to require 19 power plants in upwind states to turn on their pollution controls in a manner consistent with Maryland law.

What are the Effects of Air Pollution?

As nitrogen washes out of the air in rain, it falls into our waters, starting a deadly chain reaction: The oxides of nitrogen and mercury contribute to algal blooms that cloud the water and absorb the oxygen. Without oxygen, underwater grasses, crabs, fish, and other marine life suffocate and die. These dead zones can be truly devastating to biodiversity and are an ongoing cause for concern.  

Recreational and commercial anglers are feeling the effects of airborne pollutants, too. Air pollution, primarily from power plants, is the main source of the mercury that contaminates fish in the Bay watershed. As a result, anglers are warned to limit their consumption of certain fish species due to potentially harmful levels of this toxic chemical.

How Can We Reduce Air Pollution?

Unhealthy air doesn't have to be part of life in the Bay. And because humans are largely the cause of air pollution, we must also drive the solutions.

Alternative and renewable energy sources and low-emission vehicles should be part of our local and national strategy to reduce pollution from smokestacks and tailpipes. Smart land-use planning and innovative means of transportation are also key pieces of the pollution puzzle. Nutrient trading is another option. Individuals can take action by driving less—combining errands, carpooling, and using public transportation can help reduce car emissions.

Every Bay-loving citizen and stakeholder should demand that state and federal leaders act to enforce air-quality standards and promote innovative ways to reduce pollution from airborne sources.