EGEE 101
Energy and the Environment

What is Regional Haze? Regional Haze Revisited

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London shrouded in haze.
A view of London
Credit: © Chris M/adobe.stock.com
Map of the UK with the area around Liverpool circled.
My home town of Chester is close
to Liverpool in a key industrial 
region of the North West of England

When I was a young boy the family moved to the plains of Cheshire, a region in the northwest of England that is very flat. From my bedroom window, I could see a couple of castles (I would have to lean out of the window precariously). When I go back home, my memories of the great view are rarely repeated because the view is now often hazy. The NW of England is an industrial area: Manchester, Liverpool, etc. My bedroom window view is also of Stanlow, one of the largest European refineries (Shell).

Tankers offload oil in the Mersey estuary and it is piped to the refinery. All the industry, the utilities, and transportation (lots of cars in a small place) contribute to the pollution. It is nothing like the peace and tranquility of State College. The cause of the haze is very small particles that can stay suspended in the air for days, and can thus travel large distances on the wind. There are a number of different types of particles depending on where you are, and the local events. Haze can be a natural event when the air is humid and contains many tiny suspended water particles (think Florida on a hot and humid day - recall this is one of the reasons that solar cells are not as efficient in Florida).

Visibility often is measured as the farthest distance from which a person can see a landscape feature. Haze currently reduces natural visibility from 90 miles to between 14 and 24 miles in the eastern United States, and from 140 miles to between 33 and 90 miles in the western United States. Visibility generally is worse in the eastern United States due to higher average humidity levels and higher levels of particulate matter from manmade and natural sources.

- EPA

See It For Yourself

Natural Causes

Some of the natural particular matter (PM) emissions are from forest fires. The smoke contains fine ash particles and fine soot particles (if you have ever owned a fireplace, you know that the routine of having a chimney sweep removes soot periodically!) All combustion can produce small particles, and it is the small particles that contribute to visibility reductions and health-related problems.

Aerial view of the 2002 forest fires in Arizona.
An image captured by NASA of forest fires in Arizona.
Credit: NASA
Cotopaxi volcano eruption with huge ash cloud
Ash cloud from a volcanic eruption.
Credit: © ecuadorquerido/adobe.stock.com

Volcanic eruptions are also natural sources of particulates in the atmosphere. In addition to their potentially catastrophic consequences on the immediate localities and regions, they can also send particles high (many miles) into the atmosphere, and the fine particles can be very dangerous to aircraft (particularly those with jets), often forcing airline travel delays and the creation of alternative routes around the volcanic activity.

Manmade Causes

cars on highway with exhaust
Car exhaust
Credit: © Nady/adobe.stock.com

Dust from unpaved roads, the use of leaf blowers (often gasoline-powered, which means that VOCs are also released, contributing to more smog), and mowing the lawn, etc., all can add particles into the air and increase the smog problem, so those activities are best avoided on days where air quality is already low. Would people rather make sure the yard looks good, or do their part to preserve higher air quality?

Deisel soot
This is what diesel soot looks like, viewed by a scanning electron microscope. Just to give you a sense of the scale here, the average human hair is about 80 microns thick. If we can reduce the particulate emissions from diesel engines, that will help regional haze abatement too.
Credit: Jonathan Mathews

The Clean Air Act

lungs of nonsmoker.  They are mostly black as a result of air pollution.
You might think these are the
lungs of a smoker but they are
not. This is a result of air
pollution. There are many
nations currently struggling
with massive air pollution in
very overcrowded cities.
Credit: AQMD

The Clean Air Act classifies the size of these fine particles by two terms:

  • PM10: Particulate Matter below 10 microns
  • PM2.5: Particulate Matter below 2.5 microns

Dust is anything below 100 microns, and so we are focused on very small particles. The old standard was a limitation of the number of PM10 particulates in the air. Now, that law remains and there is another standard focusing on the very smallest particles below 2.5 microns. This is because the health impact of these smallest particles is greater than the slightly larger particles. Small particles enter into the lungs and can stay there (recall the discussion of Black Lung). Particles smaller than 1 micron not only enter the lungs but can also enter the bloodstream. This is a great concern because the small particles have a very large surface area (recall this is why we pulverize coal). Heavy metals and carcinogens from the combustion process coat these small particles. In the blood these chemicals and metals cause disease. Similar to the smog influences, these particles impact those who already suffer from limited lung capacity the most. So if you smoke, this is what you are adding to your lungs.

The cigarette is an example of biomass combustion. It produces much of the same carcinogens as does any combustion. In fact, the only way of producing these very small particles of < 1 micron is via the combustion process

Cigarette burning in an ashtray.
Credit: © Vesna/adobe.stock.com

The Environmental Protection Agency (EPA) classifies environmental tobacco smoke (ETS) as a class A carcinogen, the most hazardous classification for cancer causing agents. ETS kills as many as 53,000 nonsmokers in the United States annually; 3,000 from cancer deaths and 50,000 from cardiovascular disease and other tobacco-related illnesses.

- Smoking Cessation Program

Take a good look at the chart below. You'll see that, when the air is unhealthy, you are better off staying indoors and avoiding strenuous exercise (if only I could use this excuse more often to watch football and drink beer while eating chicken wings!)

Air Quality Index (AQI): Particulate Matter (PM)
Index Values Levels of Health Concerns PM 2.5
Cautionary Statements*
PM10
Cautionary Statements*
0-50 Good None None
51-100** Moderate None None
101-150 Unhealthy for Sensitive Groups People with respiratory or heart disease, the elderly, and children should limit prolonged exertion. People with respiratory diseases such as asthma should limit outdoor exertion.
151-200 Unhealthy People with respiratory or heart disease, the elderly, and children should avoid prolonged exertion; everyone else should limit prolonged exertion. People with respiratory diseases such as asthma should avoid outdoor exertion; everyone else should limit prolonged exertion.
201-300 Very Unhealthy People with respiratory or heart disease, the elderly, and children should avoid any outdoor activity; everyone else should avoid prolonged exertion. People with respiratory diseases such as asthma should avoid any outdoor activity; everyone else, especially the elderly and children, should limit outdoor exertion.
301-500 Hazardous Everyone should avoid any outdoor exertion; people with respiratory or heart disease, the elderly, and children should remain indoors. Everyone should avoid any outdoor exertion; people with respiratory diseases such as asthma should remain indoors.

* PM has two sets of cautionary statements which correspond to the two sizes of PM that are measured:

  • Particles up to 2.5 micrometers in size (PM2.5)
  • Particles up to 10 micrometers in size (PM10)

Progress

As you can see we are getting better air quality (but this is still problematic for those at-risk groups).

Comparison map showing improvements in air visibility between ~2000 and 2015.  The east side of the nation has reduced visibility in comparison to the west (generally).
The regional haze is finally getting better after very limited progress during the 1990s and onwards. There has been an improvement but the east of the nation is still significantly impacted. 
Credit: EPA