1 5 8 C h A p T E r 8 Environmental Health, Pollution, and Toxicology
Toxic Air Pollution and Human Health: Story of a Southeast Houston Neighborhood
Manchester is a neighborhood in southeast Houston, Texas, that is nearly surrounded by oil refineries and pet- rochemical plants. Residents and others have long noted the peculiar and not so pleasant smells of the area, but only recently have health concerns been raised. The neigh- borhood is close to downtown Houston, the houses are relatively inexpensive, and the streets are safe. It was a generally positive neighborhood except for the occasional complaints about nosebleeds, coughing, and acidic smoke smells. Over a period of years, the number of oil refineries, petrochemical plants, and waste-disposal sites grew along what is known as the Houston Ship Channel (see opening photograph).1
Cancer is the second leading cause of death of U.S. children who are not linked to a known health risk before being stricken by the disease. Investigations into child- hood cancer from air pollution are few in number but now include exposure to benzene, 1,3-butadiene (com- monly referred to simply as butadiene), and chromium.1-3
Benzene is a colorless toxic liquid that evaporates into the air. Exposure to benzene has a whole spectrum of possible consequences for people, such as drowsi- ness, dizziness, and headaches; irritation to eyes, skin, and respiratory tract; and loss of consciousness at high levels of exposure. Long-term (chronic) exposure through inhalation can cause blood disorders, includ- ing reduced numbers of red blood cells (anemia), in industrial settings. Inhalation has reportedly resulted in reproductive problems for women and, in tests on animals, adverse effects on the developing fetus. In hu- mans, occupational exposure to benzene is linked to increased incidence of leukemia (a cancer of the tissues that form white blood cells). The many potential sourc- es of exposure to benzene include tobacco smoke and evaporating gasoline at service stations. Of particular concern are industrial sources; for example, the chemi- cal is released when gasoline is refined from oil.
The chemical 1,3-butadiene is a colorless gas with a mild gasoline-like odor. One way it is produced is as a by-product of refining oil. Health effects from this toxin are fairly well-known and include both acute and chronic problems. Some of the acute problems are irritation of the eyes, throat, nose, and lungs. Possible chronic health effects of exposure to 1,3-butadiene include cancer, disorders of the central nervous system, damage to kidneys and liver, birth defects, fatigue, lowered blood pressure, headache, nausea, and cancer.1,2 While there is controversy as to whether exposure to 1,3-butadiene causes cancer in people, more definitive studies of animals (rats and mice) exposed to the toxin have prompted the Environmental Protection Agency to classify 1,3-butadiene as a known human carcinogen.1,2
Solving problems related to air toxins in the Hous- ton area has not been easy. First of all, the petrochemi- cal facilities along the Houston Ship Channel were first established decades ago, during World War II, when the area was nearly unpopulated; since then, communities such as Manchester have grown up near the facilities. Sec- ond, the chemical plants at present are not breaking state or federal pollution laws. Texas is one of the states that have not established air standards for toxins emitted by the petrochemical industry. Advocates of clean air argue that the chemical industry doesn’t own the air and doesn’t have the right to contaminate it. People in the petrochem- ical industry say they are voluntarily reducing emissions of some of the chemicals known to cause cancer. Butadiene emissions have in fact decreased significantly in the last several years, but this is not much comfort to parents who believe their child contracted leukemia as a result of expo- sure to air toxins. Some people examining the air toxins released along Houston’s Ship Channel have concluded that although further reducing emissions would be expen- sive, the technology to do it is available. Petrochemical companies are taking steps to reduce the emissions and the potential health risks associated with them, but more may be necessary.
A recent study set out to study neighborhoods (census tracts near the ship channel) with the highest levels of benzene and 1,3-butadiene in the air and to evaluate whether these neighborhoods had a higher incidence of childhood lymphohematopoietic cancer. After adjusting for sex, ethnicity, and socioeconomic status, the study found that census tracts with the highest exposure to benzene had higher rates of leukemia.1 The study concluded that elevated exposure to benzene and 1,3-butadiene may contribute to increased rates of childhood leukemia, but the possible link between the air pollution and disease needs further exploration.
Another study that examined the cancer risk near the Ship Channel concluded that, in addition to benzene, chromium IV (a combustion waste product produced in industrial processes), when inhaled, is a known human carcinogen. Chromium IV is thought to be responsible for up to 75% of the cancer risk along the Ship Channel.3
The case history of the Houston Ship Channel, oil refi- neries, and disease is a complex problem for several reasons:
1. Disease may have more than a one-cause/one-effect relationship.
2. Data on air-pollution exposure are difficult to collect and link to a population that is moving around and has different responses to exposure to chemicals.
3. It is difficult to definitively link health problems to toxic air pollutants.
4. There have been few other studies with which the Houston study can be compared.
In this chapter we will explore selected aspects of exposure to toxins in the environment and real and potential health consequences to people and ecosystems.
· Botkin, D. B., & Keller, E. A. (2014). Environmental science: Earth as a living planet (9th ed.). Hoboken, NJ: John Wiley & Sons, Inc
· Chapter 8: Environmental Health, Pollution, and Toxicology