Public Service Announcement

Low-level Carbon Monoxide Poisoning from Fossil Fuel Combustion

Emission of carbon monoxide (CO) is a byproduct of fossil fuel combustion. This varies according to make/model of vehicle, for example SUVs emit nearly twice the amount of CO than do smaller cars. This carbon monoxide is an invisible odorless gas that is often inhaled by people in the vicinity of vehicles. The approx. amount CO inhaled and its effect on the body is the subject of this report.

After CO enters the lungs it is absorbed into the bloodstream (along with oxygen, O2 gas) through the capillaries. What normally happens is the O2 molecule binds chemically with the iron (Fe) molecule in the hemoglobin. Hemoglobin is found in red blood cells and its primary function is to transport oxygen to cells. When the iron delivers the oxygen to the cells, it picks up the waste product carbon dioxide (CO2) and returns to the lung’s capillaries where CO2 is exhaled.

The CO molecule is 200 times more likely to bind with the iron molecule in hemoglobin than is O2. When this occurs, the hemoglobin can no longer deliver O2 to the cells and is considered “carboxylated hemoglobin”. When cells do not receive the needed oxygen they die. The effect of cell death from CO inhalation is called carbon monoxide poisoning. Severe cases of CO poisoning cause death, yet milder cases of CO poisoning are less noticeable but are also detrimental to health.

Low-level CO poisoning symptoms are a result of less oxygen being transported to the brain. These symptoms include nausea, dizziness, depression, irritability, headaches and other common symptoms often misdiagnosed. People who live and/or work in the vicinity of heavy vehicle traffic are more susceptible to low level CO poisoning. Long term exposure to low level CO poisoning can cause worsening of symptoms, sometimes leading to violence. The question is how much CO inhalation can cause the symptoms mentioned above?

CO inhalation is usually measured in parts per million (PPM). The amount in CO ppm inhaled that causes the above symptoms varies with each individual. On average, a one hour exposure time to CO levels of 300 ppm can lead to 10 percent carboxylated hemoglobin in the blood. (CO Headquarters) This is an estimate for an adult at rest. Any level above 5 percent carboxylated hemoglobin is abnormal and unsafe. Obviously a child at play will be far more sensitive to CO uptake and resulting increase of carboxylated hemoglobin in the blood.

Since CO inhalation is most common in urban areas of high vehicle traffic; the equation below applies to “street canyons”, areas surrounded by buildings;

Ce = (0.1*K*N*V^-0.75) / (U + 0.5)[(x^2 + z^2)^(1/2) + 2]

Ce = concentration of CO in parts per million

K = constant of 7

N = traffic (vehicles per hour)

V = vehicles ave. velocity (miles per hour)

U = wind speed (meters per second)

W = street width (meters)

x = distance of receptor from traffic lane

z = height of receptor above traffic lane

This equation is used for the “leeward” side of the street canyon, there is a separate equation for the winward side of the canyon. The leeward side is where the wind is coming from, winward side where the wind is blowing to. This is assuming the wind is blowing at an approx. 90 degree angle perpendicular to the street canyon. (Eagleman, pg. 95)

Although there are less CO emissions from modern vehicles, there are more vehicles on the road, so CO poisoning in urban areas like Los Angeles, Mexico City and Houston is still a great risk.

“The total miles driven by all passenger vehicles in the U.S. increased 2.7 times between 1965 and 1995. The passenger vehicle is still the largest single source of carbon monoxide nationwide. The emissions of hydrocarbons have been reduced by two-thirds, while the emissions of carbon monoxide have been reduced by only one-third.” (Auto Emissions and Carbon Monoxide)

Symptoms of aggressive behavior and depression in large urban areas are often misdiagnosed as mental health problems. Many people from urban areas are being incarcerated for behavior that is a result of CO poisoning over several years exposure. Urban children are especially at risk, even more frequently misdiagnosed and label ADD by a mental health system that attempts to correct this problem by prescribing pharmaceuticals.

A simpler and healthier solution would be to reduce the amount of fossil fuel combusting vehicles by increasing public transit, making cities more bike/pedestrian friendly, and using alternative fuels (hydrogen, biodiesel) instead of petroleum.

References:

“Air Pollution Meteorology” by Joe R. Eagleman 1991, University of Kansas

CO Headquarters;

http://www.coheadquarters.com/ChronicCO/indexchronic2.htm

Auto Emissions and Carbon Monoxide

http://www.sas.upenn.edu/~jafield/CO_auto_emissions.html