Air Quality

John Wilson of the Galveston-Houston Association for Smog Prevention is the latest in a long line of experts to describe the air in the Houston region as “toxic soup.” Gases from many urban and industrial sources, including trees, can brew in the air into noxious compounds, even when a chemical is benign in itself. The area’s most prevalent air pollutants are ground-level ozone (formed in mid-air on sunny days from volatile organic compounds and nitrogen oxides), airborne particulates, air toxics, carbon dioxide, and mercury.

Air pollution is a serious threat to the health and enjoyment of area residents and recently has become an economic issue. Our poor air quality has been named as a factor in corporate decisions to locate elsewhere.

However, the real impetus for business, industry, and local officials to deal with Houston’s air pollution problems is that the region does not meet federal health standards for ground-level ozone and faces a potential cut in federal highway funds if we don’t meet the standards within the next four years.

Control of Air Pollution

Air pollution in the region comes from a variety of industrial, transportation, and public and consumer sources. Only half of the nitrogen oxides, for example, is produced by area industry. Sources of other air pollutants include, but are not limited to, vehicles, furnaces, open burning, power plants, off-road vehicles, jet skis, boats, petroleum storage, factories, landfills, commercial printers, dry cleaners, filling stations, charcoal grills, lawn mowers, airplanes, and paints and solvents. Everyone can do something to reduce local air pollution.

Ozone

Without the combination of lots of ultraviolet sunlight, nitrogen oxides (NOX), and volatile organic compounds (VOC), groundlevel ozone does not form.

One way to decrease ozone formation is to decrease emissions of NOX and VOC from vehicles by consolidating errands, driving less, reducing speed, reducing idling, and by keeping vehicles properly tuned up. Technology exists for chemical plants to reduce emissions of NOX if they are willing or compelled to spend the money.

Postponing activities that produce ozone precursors until late in the day, such as waiting until after dark to refuel vehicles, will also help reduce ozone. Steps that reduce ozone will also reduce other air pollutants.

Progress

A variety of events in 2005 created a foundation for substantial progress in the region’s campaign against air pollution.

Early in the year, the Houston Chronicle ran a series of articles about its field tests for air pollution in Houston neighborhoods. The City of Houston began to take legal action against some notorious polluters. New pollution-sensing cameras have become available that make it possible for regulators to identify the source of a specific pollutant. The Texas Commission on Environmental Quality has drafted stricter regulations.

The transportation bill Congress passed in July 2005 increased highway funds for the state by more than 30 percent and allocated an additional $100 million to specific projects in the Houston area intended to reduce congestion. The bill also gives Metro an opportunity to obtain as much as $1 billion in funds for mass transit over the next ten years.

However, a 2005 energy bill approved by Congress did nothing to aid the fight against air pollution in this region, but did include funding for the National Cancer Institute to study the health effects of living near refineries and petrochemical plants.

Until 2005, the ground-level ozone standard was based on a one-hour measurement. That standard was exceeded on 33 days in 2005, a slight decrease from the year before. In June of 2005, the EPA replaced the onehour with a new eight-hour method of assessing ground-level ozone. Implementing this change has postponed the Houston-Galveston area ozone attainment deadline from 2007 to 2010. In 2005, the eight-hour standard was exceeded on 52 days, about 10 more days than in 2004.

Ozone is the only air pollutant in the region that exceeds federal health standards. However, the Houston area is close to the edge of the limit for fine particulates.

More About Ozone

Ozone is an unstable molecule of three oxygen atoms, created when a single oxygen atom reacts with an oxygen molecule. It can be formed in several ways.

The peculiar odor in the air during a thunderstorm is often ozone, formed when lightning strikes water droplets. The jolt severs the bonds between water’s two atoms of hydrogen and one atom of oxygen, freeing the oxygen atom to bond with a regular O2 molecule to form ozone.

Pure ozone is an extremely corrosive bluish gas with a pungent smell. It is manufactured in factories to be used as a bleach, to deodorize air, to purify water, and to treat industrial waste.

Ozone is also created when volatile organic compounds react with nitrogen oxides in the presence of sunlight. It is often referred to as ground-level ozone, to distinguish it from the beneficial ozone layer in the stratosphere. High levels of ground-level ozone are harmful to people, animals, plants, and even material surfaces.

Volatile organic compounds (VOC) are organic chemicals that vaporize easily, such as those found in gasoline and solvents. They are emitted from gasoline stations, motor vehicles, airplanes, trains, boats, petroleum storage tanks, and oil refineries, among many other sources. Although trees and plants emit VOCs, they are not concentrated near sources of nitrogen oxide and are not a major contributor to ozone formation.

A study of the air at the western end of the Houston Ship Channel, where the region’s most hazardous ozone plumes typically form, found that 75 percent of the ozone-forming VOC came from industrial sources. Eight percent came from trees and plants, and 17 percent was attributed to other sources such as vehicles, gas stations, and equipment.

Ozone’s second precursor, nitrogen oxides, are either nitrogen oxide molecules (NO) or nitrogen dioxide molecules (NO2). They are produced during high-temperature combustion. Half of the NOX in our area comes from industrial sources, 30 percent comes from traffic, and 20 percent comes from all other sources such as aircraft, ships, trains, and construction equipment.

Houston’s climate affects ozone levels. Warm, sunny days with calm winds are necessary for ozone to reach unhealthy levels. In some weather, ozone can reach very hazardous levels very quickly. Rain often improves air quality by “raining out” pollutants and cooling air temperatures. Cloudy days lower ozone levels by reducing temperatures and sunlight.

Although the ozone season in the Houston area typically extends from March through November, Mothers for Clean Air notes that one of the high ozone days was on December 13, when the peak temperature for the day was 70 degrees. The group also reports that high ozone levels are not limited to industrial neighborhoods. The monitor at Bunker Hill in Memorial area registered ozone levels exceeding the federal health standard on two days and a monitor at Tom Bass Park in south Houston measured excessive levels on six days.

The American Lung Association’s 2005 report gave Brazoria, Galveston, Harris, and Montgomery counties an F for their ozone levels. It ranks Harris County as the eighth worst county in the country for ozone. The Lung Association estimates that more than half a million adults and children in these counties with asthma, chronic bronchitis, and cardiovascular disease have increased health risks because of the area’s ozone levels. People who have these conditions may go to Harris County’s office of emergency management at http://hcoem.org to register for an e-mail alert notice of unhealthy ozone levels.

Particulate Matter

The accumulation of airborne particulate matter is a major concern for Houston. Particulate matter may incorporate water and a wide variety of inorganic salts, acids, metals, organic compounds, and soot-like material. A 2003 study done by Rice University found that diesel engines are the primary contributors of fine particles to Houston’s air, followed by gasoline-powered vehicles and road dust. Smoke particles from wood burning and fatty acids from meat grilling contributed considerably smaller but nonetheless significant amounts of the particulates in Houston’s air.

Very fine particulates (tiny particles and droplet aerosols smaller than 2.5 microns in diameter) are among the most deadly of air pollutants because they are small enough to settle deep into the lungs where they are absorbed and transferred to the bloodstream. It is difficult to take health-protective action against particulate matter because it easily travels indoors.

Air particulates are more of a problem in Harris County than in the rest of the region. The Lung Association’s 2005 report gave Harris County a D for this pollutant, but Brazoria and Galveston County each received a B and Montgomery County achieved an A. No Texas city is on the Lung Association’s 25 worst list for particulates.

Air particulates increase the risk of cancer and, according to some studies, cause strokes and heart attacks. The cardiovascular effects of air particulates make them particularly risky for diabetes.

The region meets the federal standards for air particulates that are 10 microns in diameter or smaller, but may not be able to comply with a new standard for particles smaller than 2.5 microns in diameter.

Air Toxics

Most other air pollutants in the Houston region are lumped into a category called air toxics. Air toxics are chemical compounds such as toluene and formaldehyde that are known to play a role in causing chronic disease, such as cancer. Sources include industry, vehicles, combustion, pesticide use, dry cleaners, and building materials. The term “air toxics” usually refers to the 188 Hazardous Air Pollutants listed in the Clean Air Act.

It is difficult to determine the extent of the problems with air toxics in the greater Houston area because there is little study or monitoring of these chemicals. Regulators rely on self-reporting by industry to determine how much of these chemicals is released each year, but recent studies have documented massive under-reporting by industry. The studies estimate that less than 15 percent of the chemicals that are released are reported.

The greatest impacts of toxic pollutants are in the industrial areas of east Harris County, especially near the Houston Ship Channel, but air toxics are present at dangerous levels everywhere in the Houston region where monitoring has occurred.

Carbon Dioxide

Another troublesome air pollutant in the Houston-Galveston metropolitan area is carbon dioxide. It is not a direct risk to human health, but is the major contributor to global warming. Most experts believe global warming contributed to the strength and number of hurricanes in the 2005 hurricane season. Local horticulturist Bob Randall at Urban Harvest said he has already noticed warmer winter temperatures. If global warming brings less rain and more heat, the area’s ozone problem will worsen.

Mercury

Mercury contamination primarily comes from coal burned in power plants. The Parish power plant in Fort Bend County is the sixth largest source of mercury emissions in the nation. Mercury pollution has become an increasing problem because mercury, first released as air pollution from factories and plants, eventually ends up in bodies of water where it bio-accumulates up the food chain. Most human exposure comes from eating contaminated fish. Large fish that feed on smaller aquatic species generally have the highest levels. The Texas Department of Health warns against eating king mackerel caught in the Gulf of Mexico and several kinds of fish caught in many lakes in East Texas because of mercury contamination.

Mercury pollution can result in serious neurological and reproductive problems.

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