What is Carbon monoxide?
Carbon monoxide (CO) is a colorless, odorless gas that is formed when carbon in fuel is not burned completely. EPA has defined the national ambient air quality standard (NAAQS) for carbon monoxide as nine parts per million averaged over an eight-hour period, and this threshold cannot be exceeded more than once a year or an area would be violating the standard.

Where does Carbon monoxide come from?
In New England, fuel combustion in residential housing, businesses, industry and utilities accounts for 10 to 20 percent of the total CO emissions, while mobile sources (cars, trucks, buses and off-road equipment such as marine engines and construction equipment) account for 80 to 90 percent.

How can Carbon monoxide affect my health?
Carbon monoxide enters the bloodstream through the lungs and reduces oxygen delivery to the body's organs and tissues. The health threat from lower levels of CO is most serious for those who suffer from cardiovascular disease, such as angina pectoris. At much higher levels of exposure, CO can be poisonous and even healthy individuals may be affected. Visual impairment, reduced work capacity, reduced manual dexterity, poor learning ability, and difficulty in performing complex tasks are all associated with exposure to elevated CO levels.

What causes variations in levels of Carbon monoxide?
High concentrations of CO generally occur in areas with heavy traffic congestion. Levels can vary based on wind speed and direction, air mixing zones, and other climatic factors. Peak CO concentrations typically occur during the colder months of the year when CO automotive emissions are greater and nighttime inversion conditions (where air pollutants are trapped near the ground beneath a layer of warm air) are more frequent.

What is being done to reduce Carbon monoxide?
EPA and the States have implemented many programs during the last two decades that have reduced CO emissions. At the national level, these measures include establishing national standards for tailpipe emissions, new vehicle technologies, and clean fuels programs. State emissions reduction measures include inspection and maintenance (I/M) programs and transportation management programs.


Sources:
EPA New England
EPA Office of Air and Radiation

Traffic monitoring is being performed to potentially show a correlation between vehicles and carbon monoxide. When traffic counts increase, do CO levels also increase? When are CO levels the highest? Do these times correspond with rush hours?

Previous studies done across the US, such as one in Los Angeles, California, found that CO levels increased as traffic increased. Data from St. Paul, Minnesota also show an increase in CO levels during peak traffic hours. These studies point out that factors such as wind speed and non-mobile sources in the area can influence CO levels and air quality overall.

Vehicles can also be a source of other air pollutants such as ozone and nitrogen dioxide. During the Olympics in Atlanta, traffic density was decreased in downtown areas which were usually congested. The decrease in traffic was associated with a prolonged reduction in ozone pollution and significantly lower rates of childhood asthma events. These data provide support for efforts to reduce air pollution and improve health via reductions in motor vehicle traffic.