The “Big Five” Air Pollutants

Carbon Monoxide

• When fossil fuels and other organic fuels (e.g. wood) burn, they release water vapor and carbon dioxide by a process called “complete combustion”

• This reaction is never truly perfect, however, and as a result, we get a fair amount of “incomplete combustion”

• Incomplete combustion is the source of several waste products that come from burning fossil fuels

• One product of incomplete combustion is carbon monoxide, a very deadly poison

Carbon Monoxide

• Carbon monoxide binds to hemoglobin which would normally carry oxygen to the body’s organs, but instead carry carbon monoxide

Carbon Monoxide

Carbon Monoxide Oxygen

Carbon Monoxide

• Sources of carbon monoxide include:– Automobile exhaust– Furnaces– Cigarettes– Fires

• Indoor carbon monoxide detectors can be installed to protect residents of the house from over-exposure

Carbon Monoxide• We can minimize (but not

eliminate) the amount of carbon monoxide released by a car using a catalytic converter

• Catalytic converters cause carbon monoxide (and other waste products) to react and form less harmful substances

Unburned Hydrocarbons

• Also called volatile organic compounds (VOC’s)• Sources– Incomplete combustion of gasoline– Evaporation of gasoline or other solvents (paints,

cleaning fluids, etc)• Are partly dealt with by catalytic converters

Nitrogen Oxides

• Referred to as Nox as it can be several compounds of nitrogen and oxygen (NO2, N2O4, for example)

• Sources– Incomplete combustion in car engines– Incomplete combustion in furnaces

VOC and NOx

• When VOC’s and NOx’s are combined together in the atmosphere, and exposed to sunlight, the combination produces photochemical smog

• Smog contains three components– VOC’s– NOx’s– Ozone

VOC and NOx

• Ozone is found in two places:– Stratosphere –

protects sun from ultraviolet radiation

– Troposphere – acts as key component of smog

VOC and NOx

• VOC’s & Nox undergo a chemical reaction in the sun to produce ozone

• Ozone in the troposphere– Lung irritant– Eye irritant– Been shown to cause emphysema

• NOx

– Brown color of smog– Shown to cause numerous breathing disorders, including

lung cancer

VOC and NOx

Sulfur Oxides (SOx)

• Coal contains sulfur (though the higher quality coals, anthracite, have a very low sulfur content).

• When coal burns, this sulfur becomes a sulfur oxide (SOx) released into the air. Sox react with water in the air to become very acidic, forming acid rain

• Can be controlled by scrubbing, a process used to remove sulfur from emissions where coal is burned

Sulfur Oxides (SOx)

Particulates

• Particulates – small solid particles or liquid droplets suspended in air currents

• Most are natural (pollen, fog for example)• Many arise from industrial and combustion

processes• Particulates reduce visibility, cause stains, and

may play a role in climate change