National Wildlife Refuge System

Scenic views of Breton Scenic views of Breton Scenic views of Breton Scenic views of Breton

Breton National Wildlife Refuge

Air Pollution Impacts


Natural and scenic resources in the Breton National Wildlife Refuge (NWR) are susceptible to the harmful effects of air pollution. Fine particles and toxic emissions, nitrogen/sulfur deposition, and formation of ozone can impact scenic resources. In addition to affecting visibility, these pollutants can potentially harm natural resources such as surface waters, fish, wildlife, and vegetation. Click on the tabs below to learn more about air pollutants and their impacts on natural and scenic resources at Breton National Wildlife Refuge.


  • Visibility
  • Fine Particles
  • Nitrogen & Sulfur
  • Toxics & Mercury
  • Ozone



Many visitors come to wildlife refuges to enjoy the spectacular vistas. Unfortunately, these vistas are often obscured by haze caused by fine particles in the air. Each major chemical component that affects haze or visibility at Breton NWR is shown in the pie chart below. Organic compounds, soot, and dust reduce visibility as well. The pie chart below shows the average percent contribution to haze at Breton NWR by each major chemical component. Sulfate contributes to 55% of the haze at Breton Island NWR and is due mainly to burning of coal at electric generating plants in the eastern US. Organic (OC) and elemental carbon (EC) contribute to 13% of the haze at Breton NWR and are thought to come mainly from sources such as motor vehicles and oil combustion. Rayleigh scattering is a natural optical phenomenon where light is deflected by matter. While this natural phenomenon contributes to visibility impairment, it also gives the atmosphere its blue color. The other contributors to visibility are a combination of man-made and natural elements.


Visibility effects at Breton Island NWR include:

  • A reduction of the average natural visual range from about 115 miles (without the effects of pollution) to about 33 miles (with the effects of pollution) at the refuge.
  • A reduction of the average visual range to about 20 miles on the most polluted days (20% highest pollution days).
  • Human produced haze frequently impairs scenic vistas at the refuge.


Breton Visibility/Haze Contributions Graph


Visibility data at Breton more>>

Fine particles


Public Health Concerns

Fine particles can get deep into human lungs because of their small size and can cause serious health problems. Numerous scientific studies have linked particle pollution exposure to irritation of the airways, coughing, difficulty breathing, aggravated asthma, chronic bronchitis, heart attacks, and premature death in people with heart or lung disease.


Breton Fine Particles Contributions Graph

Although frequently elevated, concentrations of fine particles in the wilderness area’s air comply with the National Ambient Air Quality Standards set by the U.S. Environmental Protection Agency to protect public health. Fine particles (smaller than 2.5 micrometers) originate from either direct emissions from a source (primary particle) such as construction sites, power plants and fires, or secondary particles which are created from reactions with gases and aerosols in the atmosphere emitted from sources upwind. For example, power plants, industries, and automobiles emit gases such as sulfur dioxides and nitrogen oxides, which form particles of sulfate and nitrate in the atmosphere. A modeling analysis of particles at Breton NWR gave the following estimated source contributions to PM2.5.  Sulfate rich particles and mobile sources accounted for 60% of the fine particle concentration.
Source: COHA

Nitrogen and Sulfur


Nitrogen and sulfur compounds deposited from the air may cause acidification to ecosystems at Breton NWR. Also, nitrogen deposition may cause nutrient imbalances in the ecosystem, sometimes leading to increases in weedy plant species and cause the loss of native species. Although the EPA's Acid Rain Program and other air quality management programs have significantly reduced nitrogen and sulfur deposition, some areas continue to show the effects of acid deposition.


Wet deposition of nitrogen and sulfur at the Southeast Research Station, LA 1983-2010

There is no deposition monitoring at Breton Island NWR. However, there is wet deposition monitoring at two sites in the region at the Grand Bay National Estuarine Research Reserve in Jackson County, MS, about 30 miles northeast of Breton Island NWR and at the Southeast Research Station about 100 miles northwest of Breton Island NWR in Washington Parish, LA. The Grand Bay site has only been collecting data since March 2010. The plot below shows annual average values of nitrogen and sulfur from wet deposition at the Southeast Research Station. Sulfur deposition has a decreasing trend due to controls of sulfur dioxide at coal-burning power plants. Nitrogen deposition has a smaller decreasing trend since about 1995. Wet deposition data of nitrogen and sulfur at Southeast Research Station, LA is gathered through the National Atmospheric Deposition Program (NADP).

Annual Wet Deposition at Southeast Research Station


Nationwide Nitrogen and Sulfur Deposition

The nitrogen and sulfur deposition rates near Breton Island NWR are typical for locations in the eastern United States. The total annual sulfate and nitrogen deposition throughout the United States for 2009 is shown below. Click on the maps to see better resolution images.

Nitrogen Deposition
Inorganic Nitrogen Wet Deposition 2009
US Map of Sulfate Ion Wet Deposition
Sulfate Ion Wet Deposition 2009


Nitrogen and Sulfur Deposition Data at Breton more>>

Toxics & Mercury


Toxics, including heavy metals like mercury, accumulate in the tissue of organisms in a process called bioaccumulation. In the environment, mercury converts to methylmercury in the environment and then enters the food chain. The effects of mercury can include reduced reproductive success, impaired growth and development, and decreased survival. Human activities have greatly increased the amount of mercury in the environment through processes such as burning coal for electricity and burning waste. Deposition of mercury from the air into water bodies often starts the bioaccumulation process.  An example of bioaccumulation is where plankton will take up mercury and are eaten by smaller fish, which are eaten by larger fish and then eaten by humans. This bioaccumulation affect causes potential adverse health effects in people. The southeastern US, particularly near the Gulf Coast, has the highest levels of mercury deposition in the US.

Other toxic air contaminants of concern include pesticides, industrial by-products, and emerging chemicals such as flame retardants for fabrics, some of which are also known or suspected to cause cancer or other serious health effects in humans and wildlife.


Effects of mercury and airborne toxics on ecosystems at Breton Island NWR include

    • Elevated mercury concentrations in fish and seafood have caused the Louisiana Department of Wildlife and Fisheries to recommend limited consumption.

    Additional Information:

    There are no mercury deposition monitoring sites at Breton Island NWR.  There are sites near Breton Island NWR at the Grand Bay National Estuarine Research Reserve in Jackson County, MS, about 30 miles northeast of Breton Island NWR and in Perry County, MS, about 60 miles north of Breton Island NWR. The map below shows mercury wet deposition throughout the United States for 2009. Click on the map to see a better resolution image.

    U.S. Map of Mercury Deposition Network
    Map of Mercury Deposition


    Mercury Monitoring at Breton more>>



    Public Health and Ecosystem Concerns

    Naturally-occurring ozone in the upper atmosphere forms a layer that absorbs the sun’s harmful ultraviolet rays and protects all life on earth. However, in the lower atmosphere, ozone is considered an air pollutant. Ozone forms when nitrogen oxides from vehicles, power plants, and other sources combine with volatile organic compounds from gasoline, solvents, and vegetation, in the presence of sunlight. In addition to inducing respiratory problems in people, elevated ozone exposures can injure plants. Ozone enters the plant leaves through pores (stomata), where it can kill plant tissues, causing visible injury like bleaching or dark stippling, or reduce the plant's photosynthesis, growth, and reproduction abilities.

    In humans, ozone is a respiratory irritant. Research shows that ozone can cause coughing, sinus inflammation, chest pains, scratchy throat, permanent lung damage, and reduced immune system functions. Children, the elderly, people with existing health problems, and active adults are most vulnerable.


    Ground-level ozone concentrations at the refuge approach the eight-hour average National Ambient Air Quality Standard (NAAQS) set by the U.S. Environmental Protection Agency (EPA) to protect public health. 

    The current standard is 75 parts per billion (ppb). Compliance with the standard is based on the three-year average of the 4th highest daily value per year.  EPA’s Clean Air Scientific Advisory panel has recommended a standard to 60-70 ppb. EPA has proposed to set the standard in the 60-70 ppb range but has deferred action until 2013.  Ozone has not been monitored at Breton Island NWR.  Is has been monitored since 2006 at Chalmette, LA about 50 miles west of the refuge. The three year average of the yearly 4th highest 8-hour ozone concentration in Chalmette ranged from 72.7 ppb for the 2006-2008 period to 69.0 for the 2008-2010 period.  While ozone levels at St. Marks have declined since the early 2000’s, values are still above most of the range of the recommended standard of 60-70 ppb.

    3-year average 4th highest 8-hour average concentration graph


    Effects of ozone on vegetation at Breton NWR

    The USEPA has proposed that a weighted index, called “W126” be used to evaluate potential damage to vegetation from ozone.  EPA proposed a secondary air quality standard for ozone to protect vegetation with a W126 between 7-15 ppm-hr based on a 3-year average.  The 3-year average indices at Chalmette for 3-year periods starting in 2006-2008, until 2008-2010 ranged from 6.5-8.0 ppm-hr, which are below or in the lower end of the proposed range of 7-15 ppm-hr.  Ground-level ozone at monitors nearest the refuge has in the past reached levels expected to injure sensitive plants.

    3-year average W126 index graph




    Last updated: November 8, 2012