• > Air Pollutants and Their Effects

• > Criteria Pollutants, NAAQS, Non-attainment, and SIPs

• > DCAT Messages

• > References

Texas Department
of Public Safety

Texas Department of State Health Services

U.S. Environmental Protection Agency

Air Quality Programs around Texas

Air Pollutants and Their Effects

General

• > In 2002, approximately 133 million people in the United States lived in counties that did not meet EPA standards for air quality. [1]
• > In 2006, despite great progress in air quality improvement, but due to new and more stringent federal standards, approximately 158 million people nationwide still lived in 462 counties in 119 eight-hour ozone non-attainment areas ["non-attainment" means that ozone pollution levels are above the National Ambient Air Quality Standards (NAAQS)].[2]
• > When considering all six criteria pollutants [ozone, carbon monoxide, particulate matter (PM2.5, PM10), sulfur dioxide, and lead], there were a total of 182 million people in 570 counties in 172 non-attainment areas in 39 states and territories in March 2006.[3]
• > In 2006 , there were five non-attainment areas in Texas [including San Antonio which as an Early Compact Area (EAC) is a deferred ozone non-attainment area] covering 24 counties and over 12 million population. [2,3]

NOx

• > Nitrogen oxide (NOx) is the generic term for compounds containing oxygen and nitrogen. The compounds in this category that are of most concern for air quality are NO (nitrogen monoxide) and NO₂ (nitrogen dioxide). [4]
• > NOx is formed when fuel is burned at high temperatures. Man-made sources of NOx include motor vehicle engines, electric utilities, and other fuel-burning activities. [4]
• > NOx has several negative effects on the environment and public health. For example, it: [5]
  • can trigger serious respiratory problems because it is one of the main ingredients involved in the formation of ground-level ozone;
  • reacts with other airborne substances to form toxic chemicals or nitrate particles and acid aerosols, as well as NO₂, which also cause respiratory problems;
  • plays a part in the formation of acid rain;
  • often speeds deterioration of water quality by contributing to nutrient overload;
  • contributes to smog, which is frequently noticeable in panoramic views at scenic overlooks and in national parks.

VOC

• > Volatile organic compounds (VOCs) include a variety of organic chemical compounds such as hydrocarbons, aldehydes, and ketones. [5]
• > VOCs evaporate into the atmosphere and react with other airborne compounds. They combine with NOx emissions to produce atmospheric ozone. [6]
• > VOC emissions produced by mobile sources come from both fuel combustion and fuel evaporation. Operating vehicles produce VOC emissions, but even when a vehicle is not running VOC emissions can occur in the following ways: [7]
  • After being turned off – Fuel evaporates from the engine while the motor is cooling down. This process creates what is called "hot soak" emissions.
  • While parked – Fuel evaporates from the engine while the vehicle is parked especially if the outside temperature rises during the day. This process creates what is called "diurnal" emissions.
  • During refueling – Fuel evaporates from the tank while the tank is being filled.

Ozone

• > Ozone is a form of molecular oxygen made up of three oxygen atoms linked together. The atmospheric ozone layer, which is ozone found in the upper atmosphere, occurs naturally and protects life on earth by filtering out ultraviolet radiation from the sun. [7]
• > Ozone found at ground level is a noxious pollutant--and the major component of smog. Ozone presents this country's most intractable urban air quality problem. [8]
• > Ground-level ozone is not emitted directly. Instead, it is formed by chemical reaction when NOx and VOC emissions are exposed to heat and sunlight. [9]
• > Changing weather patterns contribute to yearly differences in ozone concentrations from city to city. Also, ozone and the pollutants that cause ozone can be carried to an area from pollution sources located hundreds of miles upwind." [10]
• > For the national standard for ozone concentration in the air, the EPA set a limit of 85 parts per billion (ppb) averaged over eight hours of measurements. This standard is based on the highest ozone exposure that sensitive people (e.g., children, elderly people, and persons with asthma or other respiratory illnesses) can tolerate. [11]
• > Ground-level ozone is the major component of smog. [12]
• > At elevated levels, ozone becomes an irritant to the eyes and the respiratory system. [13]
• > Exposure to elevated levels of ground-level ozone can lead to: [10]
  • aggravation of asthma symptoms;
  • temporary decreases in lung capacity in some healthy adults; and]
  • inflammation of lung tissue.
• > Long-term or repeated exposure to elevated ground-level ozone has been associated with: [10]
  • impairment of the immune system;
  • increased susceptibility to respiratory infection; and
  • permanent scarring of the lungs.
• > Long-term exposures to ozone levels of 100 ppb can prematurely age lung tissue. [14]
• > Children are most at risk from ozone exposure because, for their size, their need for oxygen is greater than that of adults, resulting in more rapid breathing and therefore greater inhalation of pollutants. [10]
• > Children make up 25 percent of the population but 40 percent of the asthma cases. [10]
• > Children who are active outdoors during the summer when ozone levels are at their highest are most at risk of experiencing respiratory effects. [10]
• > At elevated levels, ozone can aggravate asthma, causing more asthma attacks, increased use of medication, more medical treatment, and more visits to hospital emergency clinics. [10]
• > Ozone temporarily reduces lung function by as much as 15 to 20 percent in healthy, exercising adults; over time, with repeated exposures to elevated ozone levels, permanent structural damage to the lungs is possible. [10]
• > Adults who are active outdoors (e.g., some outdoor workers) and individuals with pre-existing respiratory diseases such as asthma and chronic obstructive pulmonary disease comprise additional at-risk groups. [9]
• > "Elevated ozone levels also inhibit plant growth and can cause widespread damage to crops and forests." [7]
• > In 2001, ground-level ozone caused annual reductions of agricultural and commercial forest yields at an estimated cost of over $500 million. [15]

Carbon Monoxide

• > Carbon monoxide (CO) is a colorless, odorless, poisonous gas. It consists of a carbon atom and an oxygen atom linked together and is a product of incomplete burning of hydrocarbon-based fuels. [16]
• > Carbon monoxide results from incomplete combustion of fuel. Improperly tuned vehicle engines are likely to have higher carbon monoxide emissions. [17]
• > Nationwide, 56 percent of the carbon monoxide emissions comes from motor vehicle exhaust, while in urban areas the percentage of carbon monoxide emissions produced by motor vehicles increases to 85 to 95 percent. [18]
• > For the national standard, the EPA set a limit of nine parts per million when averaged over eight hours and a limit of 35 parts per million in any given hour.
• > Carbon monoxide interferes with the delivery of oxygen to body tissues and organs by binding to hemoglobin, the substance in blood that carries oxygen to cells. [19]
• > CO [18]
  • is poisonous even to healthy people when at high levels in the air;
  • can affect people who have heart disease; and
  • can affect the central nervous system of anyone exposed to it.
• > A study conducted from 1994 to 1996 indicated that babies born to mothers residing in Northeastern urban areas of the United States, with greater exposure to carbon monoxide and sulfur dioxide, had a significantly higher risk of low birth weight. [20]
• > For individuals who suffer from heart disease like angina, clogged arteries, or congestive heart failure, the health threat from exposure to lower levels of CO is very serious. A single exposure to CO at low levels may cause chest pain and reduce that person's ability to exercise; repeated exposures may contribute to other cardiovascular problems. [18]

Particulate Matter (PM₁₀ and PM_2.5)

• > Particulate matter refers to solid and liquid particles that can be found suspended in the air. [20]
• > Coarse particulates, from 2.5 microns up to 10 microns in diameter, are generally associated with windblown dust and from crushing or grinding operations. [20]
• > Fine particulates, smaller than 2.5 microns in diameter, are generally produced during fuel combustion or as a result of reactions of gases such as sulfur dioxide, nitrogen oxides, and volatile organic compounds. [21]
• > Particulates are emitted from vehicle fuel combustion, from tire and brake wear, and from vehicles traveling on unpaved roads. [22]
• > Both short-term (from one to 24 hours) and long-term exposures (years) to elevated concentrations of particles smaller than 10 micrometers in diameter can cause or aggravate a number of health problems and have been linked with illnesses and deaths from heart or lung diseases. [23]
• > People with heart or lung disease, older adults who may have undiagnosed heart or lung disease, and children comprise the groups most sensitive to particle pollution. [23]
• > "When exposed to [elevated concentrations of airborne] particles, people with existing lung disease may not be able to breathe as deeply or vigorously as they normally would. They may experience symptoms such as coughing and shortness of breath. Healthy people also may experience these effects, although they are unlikely to experience more serious effects." [23]
• > At sufficient levels, particle pollution can aggravate existing respiratory diseases, such as asthma and chronic bronchitis, causing more use of medication, more medical treatment, and more doctor visits. [23]
• > Elevated levels of fine particles in the air are a serious public health problem because they can pass through the nose and throat and become lodged in the lungs. These tiny particles can cause lung damage and premature death and can also aggravate respiratory conditions such as asthma and bronchitis. [23]
• > Diesel exhaust likely causes cancer in humans. [24]
• > As with cigarette smoking, exposure to elevated levels of particle pollution is associated with increased mortality and morbidity rates from respiratory and cardiovascular diseases. [25]

Criteria Pollutants, NAAQS, Non-attainment, and SIPs

• > "Criteria pollutants" are common air pollutants, found all over the United States, that can injure health, harm the environment and cause property damage. These pollutants include ozone, particulate matter, nitrogen oxides, carbon monoxide, lead, and sulfur dioxide. [26]
• > National Ambient Air Quality Standards (NAAQS) are limits set by the EPA on the maximum concentrations of criteria pollutants in the air. Primary standards are intended to protect human health; secondary standards are set to protect against other adverse effects of air pollution such as crop damage and reduced visibility. [26]
• > If an area exceeds the levels set by the NAAQS primary standards of one or more criteria pollutants in the air (as measured by air quality monitors), the area is said to be in "non-attainment" of federal air quality standards. [26]
• > State and local environmental agencies must adopt federally-approved strategies to control and/or reduce the levels of criteria pollutants in the air. These control strategies are detailed in a State Implementation Plan (SIP). [26]
• > Areas that are in non-attainment of NAAQS for one or more pollutants must adopt additional strategies to control those pollutants. These additional area-specific strategies become part of the SIP. [27]
• > The Air Quality Index (AQI) is a scale used by state and local air agencies to report how clean or polluted the air is. [26]
• > A ground-level ozone AQI of 100 or less (color code green or yellow) is considered satisfactory for most people. Air quality values above 100 (orange, red, and purple) are considered unhealthy for sensitive groups and for everyone as the AQI gets higher. [28]
• > Transportation conformity means that planned transportation facilities and traffic conditions will not cause new air quality violations, worsen existing violations, or delay timely attainment of the NAAQS air quality standards. [29]

DCAT Messages

Maintain Your Vehicle

• > Drivers will reduce their vehicles' emissions and enhance performance if they follow the manufacturers' recommended maintenance guidelines. Proper vehicle care will also extend the vehicle's life, increase its resale value, and optimize its fuel economy. [30]
• > "A car that is out of tune may have poor timing of the sparks in the engine, resulting in situations that can either cause less efficient combustion (thereby increasing carbon monoxide and hydrocarbon emissions) and/or may cause increased emissions of nitrogen oxides." [31]
• > Fixing a car that is noticeably out of tune or has failed an emissions test can improve its gas mileage by an average of four percent, though results vary based on the engine problem, kind of repair, and how well the repair is done. Fixing a serious maintenance problem, such as a faulty oxygen sensor, can improve your mileage by as much as 40 percent. [32]
• > "Check and replace air filters regularly. Replacing a clogged air filter can improve your car's gas mileage by as much as ten percent. Your car's air filter keeps impurities from damaging the insides of your engine. Not only will replacing a dirty air filter save gas, it will protect your engine." [32]
• > Keeping tires properly inflated can improve gas mileage by around 3.3 percent. Not only can underinflated tires lower gas mileage by 0.4 percent for every one psi drop in pressure of all four tires, but properly inflated tires are safer and last longer. [32]
• > When fueling, avoid "topping up" the tank – that is, dispensing a little more gasoline into the tank after the pump automatically clicks off – for two reasons:
  • Most gasoline pumps are now equipped with a vapor recovery system that prevents gasoline vapors from escaping into the air. Topping up the tank when using one of these pumps will overwhelm this system and allow more fuel to escape as vapor. [33]
  • Topping up the tank also increases the possibility of spilling fuel on the ground where it will evaporate into the air. [30]

Avoid Idling

• > Extended idling is not an effective way to "warm up" a modern vehicle's engine, even on cold days. For the computer-controlled, fuel-injected engines found in most modern vehicles, no more than 30 seconds of idling should be needed; this is enough to circulate oil through the engine. Otherwise, the best way to warm up the engine is to drive the vehicle. [34,35]
• > When a vehicle is idling, its engine uses fuel less efficiently. Excessive idling can cause a buildup of fuel residues on engine cylinder walls, spark plugs, and other engine components which eventually leads to even greater engine inefficiency, and can increase fuel consumption by four to five percent. [34]
• > Idling for long periods of time, such as while waiting in line at a drive-through, can burn more gasoline and create more polluting emissions than turning off and then re-starting the vehicle. [36]

Buy a Cleaner Vehicle

• > The Green Vehicle Guide on the EPA web site (www.epa.gov/greenvehicles) provides information about the fuel efficiency and emissions ratings of new vehicles. Fuel efficiency ratings are also provided on the window stickers of new cars.
• > The EPA assigns "bin" numbers from one to 11 to all new vehicles except heavy-duty vehicles weighing over 8500 pounds, with lower bin numbers reflecting lower emission rates. The bin numbers indicate rates of pollutant emissions. When purchasing a new vehicle, try to purchase one with a low bin number. [37]
• > "Vehicles with lower fuel economy create more carbon dioxide – the most important human-made greenhouse gas – (per mile) than vehicles with higher fuel economy. Every gallon of gasoline your vehicle burns puts 20 pounds of carbon dioxide into the atmosphere." [38]
• > "The difference between a car that gets 20 miles per gallon (MPG) and one that gets 30 MPG amounts to $663 per year (assuming 15,000 miles of driving annually and a fuel cost of $2.65)." [39]

Slow Down

• > A vehicle burns more gas and emits more pollution when its engine is operating especially hard under high load. Extra load can be created by running the air conditioner, quick accelerations, high-speed driving, climbing grades, revving the engine, and carrying extra weight. [30]
• > A vehicle's emissions can differ greatly depending upon who is driving or how they are driving. The emissions from a trip with moderate accelerations and steady speed will typically be much lower than those from a trip involving a lot of aggressive accelerations and speed changes, but even modest changes in speed during high speed driving can intermittently produce high emissions. [31]
• > Vehicles typically emit more NOx as speeds rise over 45 miles per hour; the higher the speed, the greater the pollutant emissions. [40]

Drive Less

• > In 1970, passenger and heavy-duty vehicles traveled a little more than 1.1 trillion miles in the United States. By 2004, total vehicle travel for the year was over 2.9 trillion miles. [41]
• > Options available to help reduce driving include consolidating trips, telecommuting, carpooling, using public transit, and choosing clean transportation alternatives such as biking or walking. [30]

References