Remediation

Hazardous Waste Generation

The generation of HW has many sources and is a result of intended or unintended human actions. The electronics and petroleum industries, for instance, produce HW by-products. HW is also generated when excess hazardous materials are unwanted. Examples include chlorinated solvents used in dry cleaning, pesticides used in agriculture and lawn care, and household paint thinners. Uncontrolled releases of HW can occur in leaking underground storage tanks, leaking waste disposal landfills or ponds, hazardous waste spills, or other improper disposal or storage, and they can contaminate groundwater, surface water, or air. Natural sources for hazardous chemicals, such as radon from the subsurface, selenium from soils, and toxic gases from volcanic eruptions, are a concern, but they are normally not considered when considering site remediation.

Hazardous Waste Types

The following is the U.S. Environmental Protection Agency (EPA) classification for HW:

• Listed wastes contain specific wastes that are considered hazardous. F-list wastes occur in all sectors of manufacturing and industry and are known as nonspecific source wastes. Examples include solvents, sludges from water treatment, plating bath solution and residue, wastewaters, refinery wastes, and leachate. K-list wastes identify certain wastes from specific industries. Examples include wood preservation, organic and inorganic chemical, petroleum refining, pesticide, explosive, iron and steel, and pharmaceutical industries. P- and U-list wastes identify discarded hazardous chemicals.
• Characteristic wastes do not fall into any listing category but are ignitable, corrosive, reactive, or toxic.
• Universal wastes include batteries, pesticides, mercury-containing equipment, and lamps with fluorescent bulbs.
• Mixed wastes contain a combination of radioactive and hazardous waste.

The Risks of Hazardous Waste Exposure

Since World War II, more than 70,000 synthetic chemicals have been commercially launched worldwide, and more than 1,000 new chemicals are added each year. Yet, very little is known about their effects on human health. The U.S. National Academy of Sciences estimates that scientists understand the toxicity of less than 10% of these chemicals. Moreover, a site contaminated with HW usually contains a mixture of chemicals, and little is known about their combined impacts. Increased exposure to HW probably has contributed to negative effects on human health, as described in the following:

• Cancer incidence rates have increased in the last 40 years. For example, exposures to polychlorinated biphenyls (PCBs) and dioxin has contributed to an increase in reproductive organ cancers, which represent approximately 30% of all cancers.
• Birth defects occur in roughly 15% of children born in the United States. Additionally, many still births or miscarriages occur as a result of defective fetal development. Studies have shown that birth defects are the result of exposure to five main classes of pollutants: radiation, pesticides, heavy metals, solvents, and dioxin-like chemicals.
• Asthma has increased to the point where it is a leading cause for hospitalization for inner-city children. Asthma is an immune system dysfunction triggered by common air pollutants such as street-level ozone, nitrogen oxides, particulate matter, and sulfur dioxides.
• Endocrine disruption occurs when pollutants such as PCBs, dioxins, atrazine, hexachlorobenzine, and polycyclic aromatic hydrocarbons (PAHs) interfere with hormone production causing feminization and reproductive failure. This has been shown in studies of wildlife and has raised concerns that it will have the same effect on humans.
• Nervous system can be impacted by pollutants to cause degenerative brain disorders such as Parkinson's disease, Alzheimer's disease, and Lou Gehrig's disease.
• Metabolic abnormalities can be caused by pollutants that could impair normal use of energy, manufacture of tissue, and the function of waste excretion.
• Chemical sensitivity causing allergies seems to be growing.
• Immune system damage is caused by dioxins and certain pesticides in wildlife. These same chemicals have been proven to suppress human immune systems.
• Thyroid dysfunction is part of the endocrine system, and it can result in fatigue, nervous system impacts, weight problems, reproductive problems, and other effects.
• Declining intelligence of children may occur when born to mothers exposed to PCBs.

Regulating Hazardous Waste and Remediation

As a result of a better understanding of the risks of HW in the environment, government regulations were established in most counties to prevent dumping HW directly in the ground or into streams and lakes. In the United States, for example, the Resource Conservation and Recovery Act (RCRA, Pub. L. 94–580) enacted in 1976 requires generators to track HW throughout its life cycle. However, illegal dumping and accidental discharge of HW are still contributing to the vast number of contaminated sites that were already present.

...